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  • 1.
    Acevedo Gomez, Yasna
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    On Gas Contaminants, and Bipolar Plates in Proton Exchange Membrane Fuel Cells2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The proton exchange membrane (PEM) fuel cell is an electrochemical device that converts chemical energy into electrical energy through two electrocatalytic reactions. The most common catalyst used is platinum on carbon (Pt/C), which has shown the best performance in the fuel cell until now. However, the drawback of this catalyst is that it does not tolerate impurities, and both hydrogen and oxygen may carry small amounts of impurities depending on the production sources. The purpose of this thesis is to understand the effect of two impurities that are less investigated, i.e., ammonia, which may accompany the hydrogen rich reformates from renewable sources, and nitrogen dioxide, which may come from air pollution. The mechanism of contamination and an adequate recovery method for the respective contaminant are studied. Additionally, electroplated bipolar plates with Ni-Mo and Ni-Mo-P coatings were tested as alternatives to stainless steel and carbon materials.

    The results show that ammonia not only provokes changes in the polymer membrane but also in the oxygen reduction reaction (ORR), hydrogen oxidation reaction (HOR) and catalyst ionomer in both electrodes. The extent of performance recovery after the contamination depends on the concentration used and the exposure time. In contrast, nitrogen dioxide affects the catalyst in the electrode directly; the contamination is related to side reactions that are produced on the catalyst’s surface. However, NO2 is not attached strongly to the catalyst and it is possible to restore the performance by using clean air. The time the recovery process takes depends on the potential applied and the air flow.

    Finally, the evaluation of electroplated Ni-Mo and Ni-Mo-P on stainless steel by ex situ and in situ studies shows that these coatings reduce the internal contact resistance (ICR) and the corrosion rate of the stainless steel considerably. However, the in situ experiments show that phosphorus addition to the coating does not improve the fuel cell performance; thus, the Ni-Mo alloy is found to be a promising choice for electroplating stainless steel bipolar plates.

  • 2.
    Acevedo Gomez, Yasna
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Effect of nitrogen dioxide impurities on PEM fuel cell performanceManuscript (preprint) (Other academic)
    Abstract [en]

    Air is the most practical and economical oxidant to feed to the cathode in a proton exchange membrane fuel cell (PEMFC). However, the air is accompanied by small amounts of impurities that affect the performance of the fuel cell. Among these, nitrogen dioxide is the impurity that has been least investigated, and its effect is not fully understood. In this study, a possible mechanism is proposed based on the contamination of the fuel cell at different concentrations and adsorption potentials, and by employing stripping cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The results at different concentrations showed that the catalyst sites are blocked by the adsorption of NO2, and that there is a non-linear relationship between the concentration and degradation. The degradation is suggested to be related to the formation of intermediate species, as also shown by the pseudo-inductive impedance at the concentration of 100 and 200 ppm. Furthermore, the cyclic voltammetry showed that there is an oxidation to NO3- at 1.05 V, followed by the reduction of this specie to NO2- at 0.68 V, and a subsequent reduction of NO2- to N2O and/or NH2OH.

  • 3.
    Acevedo Gomez, Yasna
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Performance recovery after contamination with nitrogen dioxide in a PEM fuel cellManuscript (preprint) (Other academic)
    Abstract [en]

    While the market of fuel cell vehicles is increasing, these vehicles will still coexist with combustion engine vehicles on the roads and will be exposed to an environment with significant amounts of contaminants that will decrease the durability of the fuel cell. In order to investigate different recovery methods, a PEM fuel cell is in this study contaminated with 100 ppm of NO2 at the cathode side. The possibility to recover the cell performance is studied by using different airflow rates, different current densities, and by subjecting the cell to successive polarization curves. The results show that the successive polarization curves are the best choice for recovery; it took 35 min to reach full recovery of cell performance, compared to 4.5 hours of recovery with pure air at 0.5 A cm-2 and 110 ml min-1. However, the performance recovery at a current density of 0.2 A cm-2 and air flow 275 ml min-1 was done in 66 min, which is also a possible alternative. Additionally, two operation techniques are suggested and compared during 7 h of operation; air recovery and air depletion. The air recovery technique shows to be a better choice than the air depletion technique.

  • 4.
    Akhand, Victoria
    KTH, School of Chemical Science and Engineering (CHE).
    Mass Balance Model of Impurities for the WoodRoll Process2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The depletion time for fossil fuels calculated from 2009 is 35 years for oil, 37 years for gas

    and 107 years for coal. Hence, it has become essential to reduce the dependence on fossil

    fuels by switching over to renewable resources. This in turn will also help in combating the

    negative effects on the environment like global warming. Thermochemical processes such as

    pyrolysis and gasification of biomass are considered the most efficient technology for

    converting biomass to useful energy carriers. Cortus Energy AB is a Swedish company that

    has developed a patented gasification technology called WoodRoll

    ® for gasification of fuels derived from biomass. However, ash in a thermochemical conversion process can cause

    corrosion, sintering, slag and poisoning of catalysts, which leads to operational problems. In

    addition, heavy metals such as Zn, Pb and Cd are environmentally problematic. These metals

    contribute to environmental pollution by contaminating the soil, which in turn can harm

    humans and the ecosystem via the food chain. The undesired elements should therefore be

    identified to minimize their impact on the overall thermochemical process and to reduce the

    emission of these harmful substances.

    The objective of this master thesis project, on behalf of Cortus Energy AB, was to investigate

    possible key numbers that can be used to describe and predict how the ash behaves in their

    patented WoodRoll® process. The key numbers that have been identified are empirically

    developed based on experience of coal combustion. These key numbers are regularly used for

    fuel derived from biomass by companies specializing in analyzing, although knowledge about

    whether they can actually be used on biomass is limited. In order to ensure that the use of

    these for biomass is correct, they must be experimentally verified in the future. In addition, a

    theoretical investigation is conducted to study which species can form and in what phase this

    occurs. The investigation reveals that there are no clear trends for how the inorganic elements

    behave since contradicting results from different studies have been reported. Formation of

    species and their phase depends on several parameters such as temperature, heating rate,

    particle size, volatility, quantity and interaction between the elements in the biomass. The

    thesis project ends with a mass balance model on selected inorganic elements for wood

    residues, as well as for bark. The model could be a tool for Cortus Energy AB to identify

    approximately how much of each element is present in each stream in the WoodRoll® process.

    The models are verified with analysis results. Inorganic elements that affect the

    overall process and its equipment have been selected for modelling. The volume percent of

    H2, CO, CO2 and CH4 in the models agree well with the values obtained by Cortus Energy

    AB. This shows that the thermodynamic equilibrium calculations performed are reasonable.

  • 5.
    Alemrajabi, Mahmood
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Transport Phenomena.
    Recovery of Rare Earth Elements from an Apatite Concentrate2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Rare earth elements (REE) are a group of 17 elements including lanthanides, yttrium and scandium; which are found in a variety of classes of minerals worldwide. The criticality of the application, lack of high grade and economically feasible REE resources and a monopolistic supply situation has raised significant attention in recovery of these metals from low grade ores and waste materials. In this thesis, the recovery of REE from an apatite concentrate, containing 0.5 mass% of REE, within the nitrophosphate route of fertilizer production has been investigated. Most of the REE (≥ 95%) content can be recovered into a phosphate precipitate with almost 30 mass% REE. Different processes have been developed to convert the REE phosphate precipitate into a more soluble form to obtain a solution suitable for further REE purification and individual separation. It has been shown that after reprecipitation of the REE phosphate concentrate as REE sodium double sulphate and then transformation into a REE hydroxide concentrate, a solution containing 45g/L REE free of Ca, Fe and P can be obtained. The results suggest that the apatite waste after processing of iron ore have the potential to be a very important source for REE in Europe and that the economy is strongly supported by the simultaneous extraction of phosphorous.

    The potential of using hollow fiber supported liquid membrane (HFSLM) extraction in individual and group separation of REE has been investigated. A hollow fiber supported liquid membrane plant in pilot scale has been operated according to the three main configurations: standard hollow fiber supported liquid membrane technology (HFSLM); hollow fiber renewal liquid membrane technology (HFRSLM) and emulsion pertraction technology (EPT). The standard HFSLM operation is more selective than HFRSLM and EPT, while higher metal transport rate is observed in EPT followed by HFRSLM and HFSLM. The HFRLM configuration helps to maintain the performance of the liquid membrane.

  • 6.
    Andersson Krohn, Robert
    KTH, School of Chemical Science and Engineering (CHE).
    Biomethane via Woodroll® - Investigation of Revenues & Profitability Analysis2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Woodroll® is a gasification technology developed by Cortus that produces synthetic gas (syngas) from biomass. Syngas can be used in several different applications. One interesting option is to convert it further into biomethane, which can be used as automotive fuel or replace natural gas in gas grids. The revenues and profitability of biomethane production is heavily dependent on policy instruments and support schemes. These subsidies can be either direct, where the producer receives a feed-in tariff for biomethane production, or indirect, where consumption rather than production is stimulated.

    This work has investigated which revenues that can be expected from biomethane production via Woodrooll® in Sweden, the Netherlands, Germany, the UK, France and Italy, both in terms of amounts and risks. A profitability analysis have also been carried out to preliminary compare the returns in the different countries, where two different scenarios for different revenues have been analyzed for two different feedstock prices.

    The results showed that the Netherlands and Italy provides the potentially highest revenues. However, there are uncertainty factors associated with all cases. Sweden and Germany offers indirect support and negative market trends. The Netherlands and the UK are the only options that provide a feed-in tariff for biomethane production via gasification. In the Netherlands the tariff can be secured before making investment decision but is only disbursed for 12 years. The UK offers a fixed feed-in tariff for 20 years but the tariff is secured first after plant start-up and the tariff may be reduced on a quarterly basis. In fact, the tariff has been reduced with 40 % over the last 24 months, but there are discussions on introducing a separate tariff for gasification. Italy has the support schemes that potentially offer the highest revenues, but gasification is currently not eligible for support. The latter also holds for France, which may be an interesting case in the future.

    If risk is to be minimized, Cortus may either focus on the Netherlands or await the discussions in the UK and France on introducing a gasification tariff. The work on standardization of biomethane use should also be followed since Italy offers the potentially highest return of the investigated countries. It is also recommended to look further for other cases. The best-case scenario for the risk averse is the one that provides a fixed tariff for 20 years and in which the tariff can be secured before an investment decision is taken.

  • 7.
    Ascue Avalos, Katia
    KTH, School of Chemical Science and Engineering (CHE).
    Avfallshanteringens miljöpåverkan - Fem avfallstypers koldioxidutsläpp i SÖRABs återvinningsprocess2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The climate change is one of the biggest environmental problems we face today and is due to the increased greenhouse effect caused by mainly carbon dioxide.  SÖRAB is a waste management company in Sweden who has been getting questions from its customers about the amount of carbon dioxide that is emitted when different types of waste is recycled through their process. This thesis answers this question for five different waste types: gypsum, plastic, textile, concrete and tires. In addition to the emissions from the recycling process in SÖRAB the emissions from another alternative process for each waste is estimated. The alternative process will be either incineration or landfill. With the help of both the alternative process and SÖRABs process an environmental benefit is calculated where a positive environmental benefit means that a saving of carbon dioxide emissions has been made by not sending the waste to incineration or landfill.

     

    The carbon emission from the following parts of the process is included:

    • Transportation of the waste (includes transport by truck and ferry)

      • Transportation within SÖRABs different facilities

      • Transportation from SÖRABs facilities external recycling companies.

    • The energy consumption from ”waste crusher” machine in SÖRAB

    • Fuel consumption from the machines in SÖRAB

    •  The carbon dioxide emissions from the external companies where the waste is recycled. This also includes the transportation in the case a part of the waste is further transported to be incinerated and the emission from the incineration itself.

     

    The results showed that the carbon dioxide emissions for each waste differed very much. The differences were due to each waste recycling process in SÖRAB, which differed in the transported weights, transport lengths, and emission levels in the external company. For plastics, textiles and tires, it was the transportation to the external companies which was the factor that contributed the most to the total carbon dioxide emission. For gypsum and concrete it was the emissions in the external companies that contributed the most, which is due to transport length being shorter for their recycling processes.

     

    The environmental benefit was the highest for the recycling of tires, 611 kg C02/ton plastic is saved by not sending it to incineration and instead recycle it through SÖRABs process.  The result is mainly due to the alternatives process emission from the ferry and incineration.

     

    The environmental benefits were positive for all the waste types except for plastic

     (-9,85)  kg CO2/ton textile) which had a long transportation length in comparison to the alternative process which was to send to incineration. In this report it was nevertheless concluded that this doesn’t mean that it would be a better option to incinerate the plastic since the real environmental benefit of plastic and all the other waste types is in the amount of carbon dioxide that is being saved by not needing to manufacture more of the material that is being regenerated through the recycling process.

     

  • 8.
    Barrientos, Javier
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Deactivation of cobalt and nickel catalysts in Fischer-Tropsch synthesis and methanation2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

                A potential route for converting different carbon sources (coal, natural gas and biomass) into synthetic fuels is the transformation of these raw materials into synthesis gas (CO and H2), followed by a catalytic step which converts this gas into the desired fuels. The present thesis has focused on two catalytic steps: Fischer-Tropsch synthesis (FTS) and methanation. The Fischer-Tropsch synthesis serves to convert synthesis gas into liquid hydrocarbon-based fuels. Methanation serves instead to produce synthetic natural gas (SNG). Cobalt catalysts have been used in FTS while nickel catalysts have been used in methanation.

                The catalyst lifetime is a parameter of critical importance both in FTS and methanation. The aim of this thesis was to investigate the deactivation causes of the cobalt and nickel catalysts in their respective reactions.

                The resistance to carbonyl-induced sintering of nickel catalysts supported on different carriers (γ-Al2O3, SiO2, TiO2 and α-Al2O3) was studied. TiO2-supported nickel catalysts exhibited lower sintering rates than the other catalysts. The effect of the catalyst pellet size was also evaluated on γ-Al2O3-supported nickel catalysts. The use of large catalyst pellets gave considerably lower sintering rates. The resistance to carbon formation on the above-mentioned supported nickel catalysts was also evaluated. Once again, TiO2-supported nickel catalysts exhibited the lowest carbon formation rates. Finally, the effect of operating conditions on carbon formation and deactivation was studied using Ni/TiO2 catalysts. The use of higher H2/CO ratios and higher pressures reduced the carbon formation rate. Increasing the temperature from 280 °C to 340 °C favored carbon deposition. The addition of steam also reduced the carbon formation rate but accelerated catalyst deactivation.

                The decline in activity of cobalt catalysts with increasing sulfur concentration was also assessed by ex situ poisoning of a cobalt catalyst. A deactivation model was proposed to predict the decline in activity as function of the sulfur coverage and the sulfur-to-cobalt active site ratio. The results also indicate that sulfur decreases the selectivity to long-chain hydrocarbons and olefins.

  • 9.
    Becker, Sebastian
    KTH, School of Chemical Science and Engineering (CHE).
    Inverkan av olika joner och jonconcentrationer på porstorleksfördelningen i trämassa-fibrer2011Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The basic ingredient of paper is the individual wood fibers. The property of the fibers depends on a variety of factors e.g., method of pulp production and processing. The final sheet quality depends in part on how the fibers interface between each other and therefore factors that affect the fiber size are of interest.

    The flexibility of the fibers depends in part on the pore water i.e., the fiber swelling. The sheet becomes less flexible at low water content which gives a loss in strength. Thus it becomes desirable to increase the water uptake.

    The experimental investigation described in this report consists of exposing the wood fibers to different ions and ionic strength and then measure the pore size by thermoporosimetry where a DSC (Differential Scanning Calorimeter) is used. DSC measures the freezing point of water in the pores of the wood fibers. As the freezing point varies with the pore size the size distribution can be determined.

    The results show that there are complications with thermoporosimetry measurements at different ion concentrations. The strength of the ionic solutions will contribute to a fictitious pore volume, which makes analysis difficult to interpret.

  • 10.
    Benyahia Erdal, Nejla
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymer Technology.
    Adolfsson, Karin H.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Green Strategy to Reduced Nanographene Oxide through Microwave Assisted Transformation of Cellulose2018In: ACS Sustainable Chemistry and Engineering, ISSN 2168-0485, Vol. 6, no 1, p. 1245-1255Article in journal (Refereed)
    Abstract [en]

    A green strategy for fabrication of biobased reduced nanographene oxide (r-nGO) was developed. Cellulose derived nanographene oxide (nGO) type carbon nanodots were reduced by microwave assisted hydrothermal treatment with superheated water alone or in the presence of caffeic acid (CA), a green reducing agent. The carbon nanodots, r-nGO and r-nGO-CA, obtained through the two different reaction routes without or with the added reducing agent, were characterized by multiple analytical techniques including FTIR, XPS, Raman, XRD, TGA, TEM, AFM, UV-vis, and DLS to confirm and evaluate the efficiency of the reduction reactions. A significant decrease in oxygen content accompanied by increased number of sp2 hybridized functional groups was confirmed in both cases. The synergistic effect of superheated water and reducing agent resulted in the highest C/O ratio and thermal stability, which also supported a more efficient reduction. Interesting optical properties were detected by fluorescence spectroscopy where nGO, r-nGO, and r-nGO-CA all displayed excitation dependent fluorescence behavior. r-nGO-CA and its precursor nGO were evaluated toward osteoblastic cells MG-63 and exhibited nontoxic behavior up to 200 μg mL-1, which gives promise for utilization in biomedical applications.

  • 11.
    Beretta, A.
    et al.
    Dipartiemento Energia- Politecnico di Milano.
    Groppi, G.
    Dipartiemento Energia- Politecnico di Milano.
    Lualdi, Matteo
    Dipartiemento Energia- Politecnico di Milano.
    Tavazzi, I.
    Dipartiemento Energia- Politecnico di Milano.
    Forzatti, P.
    Dipartiemento Energia- Politecnico di Milano.
    Experimental and modeling analysis of methane partial oxidation: transient and steady-state behavior of rh-coated honeycomb monoliths2009In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 48, no 8, p. 3825-3836Article in journal (Refereed)
    Abstract [en]

    The present study consists of an experimental and theoretical study of the performance of Rh-coated honeycomb monoliths for methane partial oxidation. The thermal behavior of Rh-coated honeycomb monoliths was studied under representative operating conditions, at steady state and during light-off. Model analysis (based on a dynamic heterogeneous reactor model that incorporates a kinetic scheme of the process independently developed, and well-assessed correlations for heat and mass transfer) provided a key for interpreting the observed effects. The comprehension of how transport phenomena and surface kinetics affect the reactor behavior leads to the conclusion that the feasibility of small-scale production of syngas via CH(4) catalytic partial oxidation relies on thermal management of the short contact time reactor and not the obtainment of high syngas yields (which is not a challenging task). Severe operating conditions (and high surface temperatures) can deplete the catalyst activity and cause unstable reactor operation. Guidelines for optimal reactor design are proposed.

  • 12.
    Bergström, Lars Magnus
    et al.
    KTH, Superseded Departments, Chemistry. YKI, Institute for Surface Chemistry, Sweden .
    Eriksson, Jan Christer
    KTH, Superseded Departments, Chemistry. YKI, Institute for Surface Chemistry, Sweden .
    Synergistic effects in binary surfactant mixtures2004In: Progress in Colloid and Polymer Science, ISSN 0340-255X, E-ISSN 1437-8027, Vol. 123, p. 16-22Article in journal (Refereed)
    Abstract [en]

    By considering the main contributions to the micellar free energy we have analysed the synergistic effect often seen on the CMC of a binary surfactant mixture. The synergistic effects are due mainly to the entropic free energy contributions related with the surfactant head groups. Several cases have been treated: (i) For a mixture of a monovalent ionic and a non-ionic surfactant in the absence of added salt we obtain, entirely because of electrostatic reasons, a negative deviation from the ideal behaviour corresponding to an interaction parameter β≈-1. Upon adding an inert salt we found that the magnitude of the synergistic effect first increases, reaches a maximum and eventually decreases. (ii) For mixtures of two ionic surfactants with the same charge number but with different hydrocarbon moieties β-values as low as -10 may arise. (iii) For mixtures of an anionic and a cationic surfactant enormous effects are anticipated yielding β≤-20 depending on the CMCs of respective pure surfactant. (iv) Synergistic effects due to different cross-section areas of the head groups are found to be rather small, with 0 > β > -1, provided the difference in head group size is modest but can become more significant when the size difference is larger.

  • 13. Bertram, F.
    et al.
    Zhang, Fan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Evertsson, J.
    Carla, F.
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Messing, M. E.
    Mikkelsen, A.
    Nilsson, J-O
    Lundgren, E.
    In situ anodization of aluminum surfaces studied by x-ray reflectivity and electrochemical impedance spectroscopy2014In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 116, no 3, p. 034902-Article in journal (Refereed)
    Abstract [en]

    We present results from the anodization of an aluminum single crystal [Al(111)] and an aluminum alloy [Al 6060] studied by in situ x-ray reflectivity, in situ electrochemical impedance spectroscopy and ex situ scanning electron microscopy. For both samples, a linear increase of oxide film thickness with increasing anodization voltage was found. However, the slope is much higher in the single crystal case, and the break-up of the oxide film grown on the alloy occurs at a lower anodization potential than on the single crystal. The reasons for these observations are discussed as are the measured differences observed for x-ray reflectivity and electrochemical impedance spectroscopy.

  • 14.
    Bessman, Alexander
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Interactions between battery and power electronics in an electric vehicle drivetrain2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The electric machine and power electronics in electric and hybrid electric vehicles inevitably cause AC harmonics on the vehicle's DC-link. These harmonics can be partially filtered out by large capacitors, which today are overdimensioned in order to protect the vehicle's battery pack. This is done as a precaution, since it is not known whether ripple-current has any harmful effect on Li-ion  cells.

    We have measured and analyzed the ripple-current present in a hybrid electric bus, and found that a majority of the power was carried by frequencies in the range 100~Hz to 1~kHz. The single most energetic harmonic in this particular vehicle is believed to have been caused  by a misaligned resolver in the motor.

    We have also designed and built an advanced experimental set-up in order to study the effect of ripple-current on Li-ion cells in the lab. The set-up can cycle up to 16 cells simultaneously, with currents of up to 50~A including a superimposed AC signal with a frequency of up to 2~kHz. The cells' temperatures are controlled by means of a climate chamber. The set-up also includes a sophisticated safety system which automatically acts to prevent dangerous situations before they arise.

    Using this set-up we tested whether superimposing AC with a specific frequency improves the charging performance of Li-ion cells. Statistical analysis found no improvement over regular DC cycling, and a physics-based model explains the experimental findings.

    We have also investigated whether ripple-current accelerates the aging of Li-ion cells. Twelve cells were either calendar or cycle  aged for one year, with some cells being exposed to superimposed AC with a frequency of 1~Hz, 100~Hz, or 1~kHz. No effect was observed on any of capacity fade, power fade, or aging mechanism.

    Finally we also tested whether it is possible to heat Li-ion cells from low temperatures using only AC. We propose a method for AC heating of Li-ion cells, and open the discussion for generalizing the technique to larger battery packs.

    In conclusion, ripple-current has negligible effect on Li-ion cells, except for heating them slightly.

  • 15.
    Bessman, Alexander
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Soares, Rúdi
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Vadivelu, Sunilkumar
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Svens, Pontus
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Ekström, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Challenging Sinusoidal Ripple-Current Charging of Lithium-Ion Batteries2018In: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 65, no 6, p. 4750-4757Article in journal (Refereed)
    Abstract [en]

    Sinusoidal ripple-current charging has previously been reported to increase both charging efficiency and energy efficiency and decrease charging time when used to charge lithium-ion battery cells. In this paper, we show that no such effect exists in lithium-ion battery cells, based on an experimental study of large-size prismatic cells. Additionally, we use a physics-based model to show that no such effect should exist, based on the underlying electrochemical principles.

  • 16.
    Bessman, Alexander
    et al.
    KTH.
    Soares, Rúdi
    KTH.
    Wallmark, Oskar
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Svens, Pontus
    KTH.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Aging effects of AC harmonics on lithium-ion cellsManuscript (preprint) (Other academic)
  • 17.
    Bessman, Alexander
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Soares, Rúdi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Wallmark, Oskar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Svens, Pontus
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Aging effects of AC harmonics on lithium-ion cells2019In: Journal of Energy Storage, E-ISSN 2352-152X, Vol. 21, p. 741-749Article in journal (Refereed)
    Abstract [en]

    With the vehicle industry poised to take the step into the era of electric vehicles, concerns have been raised that AC harmonics arising from switching of power electronics and harmonics in electric machinery may damage the battery. In light of this, we have studied the effect of several different frequencies on the aging of 28 Ah commercial NMC/graphite prismatic lithium-ion battery cells. The tested frequencies are 1 Hz, 100 Hz, and 1 kHz, all with a peak amplitude of 21 A. Both the effect on cycled cells and calendar aged cells is tested. The cycled cells are cycled at a rate of 1C:1C, i.e., 28 A during both charging and discharging, with the exception of a period of constant voltage at the end of every charge. After running for one year, the cycled cells have completed approximately 2000 cycles. The cells are characterized periodically to follow how their capacities and power capabilities evolve. After completion of the test about 80% of the initial capacity remained and no increase in resistance was observed. No negative effect on either capacity fade or power fade is observed in this study, and no difference in aging mechanism is detected when using non-invasive electrochemical methods of post mortem investigation.

  • 18.
    Bhasin, Aditi
    KTH, School of Chemical Science and Engineering (CHE).
    Recovery of Phosphorus from Incineration of Sewage Sludge2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The primary source of phosphorus, phosphate rock, is a non-renewable resource which is expected to get exhausted in the next 50 – 100 years. Sewage sludge in Sweden constitutes 25% of the annual phosphorus in the country, making it a potentially significant source for phosphorus recovery. The aim of this project was to identify the potential for phosphorus recovery from incineration of dewatered and digested sewage sludge in Fortum Värme’s power plants in Stockholm. The study was limited to two boilers located at Bristaverket, Stockholm - boiler B1, a bio-fired fluidized bed boiler and boiler B2, a waste-fired grate incinerator. A theoretical analysis for boiler B1 showed that it is possible to reach a concentration of 4.6% phosphorus in fly ash if sludge and recycled wood fuel are mixed in the ratio 48:52. A test program was executed in boiler B2 to burn up to 12.5% sludge with a mixture of household waste and industrial waste. A total of 755 tons of sludge was used over a period of three weeks during the test in boiler B2. The test was successful in terms of combustion and emissions. There was no increase in the emissions of nitrogen oxides, sulphur dioxide and hydrochloric acid in the flue gas. Mercury emissions in the chimney increased with an increase in the share of sludge, nevertheless, the emission level was below the limit set by the Swedish Environmental Protection Agency. Decrease in the amount of unburnt materials in bottom ash and in the emission of carbon monoxide showed that the burning of fuel was more efficient with input of sludge. The maximum phosphorus concentration was 0.7% in both bottom ash and fly ash from boiler B2 and occurred at an input of 12.5% sludge. This concentration is close to the expected theoretical value, however it is not expected to be feasible to recover phosphorus at such a low concentration. The ashes were sent to Fortum Waste Solutions and Ragn-Sells for recovery of phosphorus, however the results are not included in this report due to time constraints for thesis study. In order to increase the concentration of phosphorus in the ashes, a system approach is recommended, for instance, recirculation of bottom ash into the incinerator.

  • 19.
    BOOG RUDBERG, SUSANN
    KTH, School of Chemical Science and Engineering (CHE).
    Kylanläggning för småskalig ölproduktion anpassad för jäsning och lagring av lageröl2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    There has been a large increase of microbreweries in Sweden in the past few years, most of which produce great beers such as ales and stouts. This is however a bit strange since most Swedes seem to prefer to drink lager; at least if you study the statistics of the Swedish alcohol monopoly’s top hundred most drunken beers last year. There might be several reasons for microbreweries not brewing lagers but one reason is the equipment needed for lager brewing. Apart from the regular brewing equipment needed for brewing ales, a cooling system is needed in lager brewing in order to reach the ideal temperatures for fermentation, 10°°C, and lagering. Lagering is a process where beer is stored for weeks or months in a cold place, typically around 0°C.  The cooling systems on the market are expensive and small start-up microbreweries do not have the funds to purchase these. One example of such a microbrewery is Brewing Költur, and this study aims to solve the cooling problem for them.

    The goal was to design a cheaper alternative for cooling a 300-litre batch of beer but without severe changes in quality. The product needs to be able to hold stable temperatures and also lower the temperatures from 10°°C to 0°°C, both without major fluctuations in temperature within the vessel. The project did not aim at solving other lager brewing related problems.

    The result was a Bag-in-Box: a chest freezer in which a disposable plastic bag, big enough to fit 300 litres of beer, was placed. An air gap was created in between the inside walls of the freezer and the bag to keep the sudden cold walls from damaging the yeast by cooling it to quickly.

    A prototype was put together in order to test the most important features of the product. The tests showed that the product could keep stable temperatures very well in the lower temperature intervals, while it needed manual stirring in the higher regions to avoid temperature gradients, especially when the temperature was lowered.

    The cost of the product is overall very low. The investment cost is very low, however since the disposable bags are somewhat costly the variable cost is fairly high, yet still significantly cheaper than the alternatives on the market.

    It is believed that the product could be used by many smaller microbreweries in the future due to the low investment cost, its ability to keep the temperatures relatively stable and also because it is easy to assemble.

     

  • 20.
    BORIS ERIC ALAIN, BIZET
    KTH, School of Chemical Science and Engineering (CHE).
    From Sugar to Furfural Compounds Using Flow Chemistry2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Due to the need to find alternatives for the current fossil-based chemical industry, the use of blo-sourced platform chemicals as building blocks for the synthesis of a wide range of industrial and consumer chemicals has gained significantly in importance over the past years.

    In this context, 5-(chloromethyl)furfural (CMF) could become a very interesting target for  the implementation of a sugar-based biorefinery. Originating from the dehydration of cellulose,  hemlcellulose or sugar, it can for example be a precursor of bio-fuels and/or fuel additives. However, there are very few published examples on the CMF synthesis as well as its ability to be further converted in interesting derivatives.

    A simple procedure for the conversion of sugar-based feedstocks to CMF, using flow chemistry, is reported in this  master  thesis.  Sucrose  and  High  Fructose  Corn  Syrup  (HFCS-90  and  HFCS-55)  were  shown  to  be suitable feedstocks. The use of HFCS-90 has been demonstrated to be particularly promising, as it could be converted in a stable process which yields 70% of CMF.

    As a proof of concept, condensation reactions of 5-methylfurfural (MF) and CMF were performed with amine compounds, thus expanding the existing pool of CMF derivatives. MF condensations could be performed under harsh conditions, whereas CMF required milder treatments. Very high conversions were observed, especially when using aliphatic amines as starting materials.

  • 21. Bylin, Susanne
    et al.
    Olsson, Carina
    Westman, Gunnar
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Solvation behavior of cellulose and xylan in the MIM/EMIMAc ionic liquid solvent system: Parameters for small-scale solvation2014In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 9, no 1, p. 1038-1054Article in journal (Refereed)
    Abstract [en]

    Ionic liquid treatment has been reported by several researchers as a possible step in the process of fractionating lignocellulosic biomass within the biorefinery concept. However, understanding how solvation can be achieved and how the feedstock biopolymers are affected is needed prior to a viable implementation. An effective two-component solvent system for the wood components cellulose and xylan has been developed. Furthermore, the solvation of these components in the system consisting of the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate (EMIMAc) in a novel combination with the co-solvent 1-methylimidazole (MIM) is investigated. Focused beam reflectance measurement (FBRM) particle characterization in combination with microscopic analysis and molecular weight determinations (xylan) shows that cellulose and xylan can be most efficiently solvated using only 3 to 4% IL (n/n anhydro-glucose units and n/n anhydro-xylose units) and 9% IL, respectively, while still avoiding any significant polymer degradation. A model for a two-step process of cellulose solvation in the present system is proposed.

  • 22.
    Bäckström, Marie
    KTH, School of Chemical Science and Engineering (CHE).
    Global Manufacturing Training: The localization of the Powerformer Field Operator curricula at the Notre Dame de Gravenchon Refinery2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Global Manufacturing Training (GMT) project aims at homogenizing and raising the level of competency of the workforce at ExxonMobil plants in all countries where the company is active. This report presents and introduces the main structures of the GMT venture. It deals with important aspects of the project on a global scale, but it also details the implementation of training on a local level. The different pedagogical strategies are outlined, along with the resulting system of training documents.

    A global team of experts developed general training documents, called global modules in order to set the standard for the various training documents. The inherent differences between the plants in the ExxonMobil corporation makes it necessary to adapt the global modules to fit with the site in question. The differences between the plants are of both technical character, but also concern working procedures. The process of adapting each document according to the GMT outline is called Localization.

    In the current work, the localization of training documents for the Powerformer at the refinery in Notre Dame de Gravenchon-Port Jérôme (NDG-PJG) is detailed and explained. At the NDG-PJG refinery there are two units containing a Powerformer. The training documents concern the field operator, working on what is locally called the Reforming 2 position. The ensemble of the documents localized will be used for the habilitation of the process operator. Habilitation refers the preparatory training needed in order to be able to perform the tasks and procedures of a specific position. The work has resulted in the localization of 90 percent of the global documents concerning the Reforming 2 position.

  • 23.
    Caetano de Souza, Antonio Carlos
    et al.
    Department of Energy, São Paulo State University (UNESP), Brazil.
    Silveira, José Luz
    Department of Energy, São Paulo State University (UNESP), Brazil.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Zanzi Vigouroux, Rolando
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    A low cost & safe system of hydrogen production utilizing NaBH4 and CoO catalysis2007In: 2nd International Congress University-Industry Cooperation (UNIDU07), 2007Conference paper (Refereed)
    Abstract [en]

    The objective of this study was to evaluate the hydrogen production through hydrolysisof sodium borohydride (NaBH4) utilizing catalysts containing CoO. The reactant is safe and stable(when dry) at room temperature. Few works and studies have presented results of investigationsutilizing catalysts containing cobalt; however utilizing catalysts containing CoO were not found yet.In this work simple and cheap hydrogen generation system was developed having reactions atnormal conditions of temperature and pressure. A solution containing a gravimetric composition of10% wt. NaOH, 10% wt. NaBH4 and 80% wt. H2O was utilized. The reaction was carried out atvarious times using the same catalyst to evaluate its performance. This catalyst presented highrates of hydrogen production, especially at its start-up (about 99% of the theoretical hydrogenvolume was produced) at room temperature. After start-up, e.g., when more solution was put, rateof hydrogen production decreased having its production performance also decreased. Probablythis fact occurred due to the formation of the solid phase products such as NaBO2 which might fillthe porous catalyst structure; decreasing the catalytic area. This catalyst is suggested in situationswhere high production rates are necessary such as start-up of fuel cells.

  • 24.
    Caetano de Souza, Antonio Carlos
    et al.
    Department of Energy, São Paulo State University (UNESP), Brazil.
    Silveira, José Luz
    Department of Energy, São Paulo State University (UNESP), Brazil.
    Kiros, Yohannes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Zanzi Vigouroux, Rolando
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Hydrogen production through hydrolysis of NaBH4: The use of catalysts containing Pt and Pt-Ru2007In: 2nd International Congress University-Industry Cooperation (UNIDU07), 2007Conference paper (Refereed)
    Abstract [en]

    Several works about hydrolysis of NaBH4 utilizing various catalysts (such as catalysts containing Pt or Ru) are available in the literature. Investigations involving NaBH4 has increased due to the possibility to produce hydrogen using simple and safe systems, even at room temperatures with very high efficiencies. A solution containing a gravimetric  composition of 10%wt. NaOH, 10%wt. NaBH4 and 80%wt. H2O was utilized and the reaction was initiated immediately as soon as this solution was put in the chosen catalysts, in this case, catalysts containing Pt and mixtures of Pt-Ru. Catalysts containing Pt and Pt-Ru presented high yields of hydrogen after the solution being inserted in the reaction vessel several times. In this study it was found out that the rates of hydrogen production were increased with catalysts containing Pt and Pt-Ru (99 and 96% of theoretical hydrogen production respectively). The catalysts containing Pt presented higher production rate, while the catalysts containing the mixed Pt-Ru presented a quasi-linear production, e.g., stable production rate.

  • 25.
    Carlson, Annika
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Shapturenka, Pavel
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Eriksson, Björn
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Wreland Lindström, Rakel
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Electrode parameters and operating conditions influencing the performance of anion exchange membrane fuel cells2018In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 277, p. 151-160Article in journal (Refereed)
    Abstract [en]

    A deeper understanding of porous electrode preparation and performance losses is necessary to advance the anion exchange membrane fuel cell (AEMFC) technology. This study has investigated the performance losses at 50 °C for varied: Tokuyama AS-4 ionomer content in the catalyst layer, Pt/C loading and catalyst layer thickness at the anode and cathode, relative humidity, and anode catalyst. The prepared gas diffusion electrodes in the interval of ionomer-to-Pt/C weight ratio of 0.4–0.8 or 29–44 wt% ionomer content show the highest performance. Varying the loading and catalyst layer thickness simultaneously shows that both the cathode and the anode influence the cell performance. The effects of the two electrodes are shown to vary with current density and this is assumed to be due to non-uniform current distribution throughout the electrodes. Further, lowering the relative humidity at the anode and cathode separately shows small performance losses for both electrodes that could be related to lowered ionomer conductivity. Continued studies are needed to optimize, and understand limitations of, each of the two electrodes to obtain improved cell performance.

  • 26. Castro, A.
    et al.
    Vilaplana, Francisco
    KTH, School of Biotechnology (BIO), Glycoscience.
    Nilsson, L.
    Characterization of a water soluble, hyperbranched arabinogalactan from yacon (Smallanthus sonchifolius) roots2017In: Food Chemistry, ISSN 0308-8146, E-ISSN 1873-7072, Vol. 223, p. 76-81Article in journal (Refereed)
    Abstract [en]

    Yacon (Smallanthus sonchifolius Poepp. & Endl.) roots are largely grown in Andean countries and have attracted recent interest due to their antioxidant and prebiotic effects. Yacon is typically consumed as a fruit due to its sweet taste and juiciness. The macromolecular properties of an aqueous extract of yacon are investigated using asymmetric flow field-flow fractionation (AF4) coupled to UV, multiangle light scattering (MALS) and differential refractive index (dRI) detection. The method allows for determination of molar mass and size over the size distribution. Three major populations were found of which one strongly dominates in concentration. Through collection of fractions from AF4, carbohydrate composition and glycosidic linkage analysis for the dominating population was performed. The results show that the dominating population consists of a highly branched arabinogalactan (type 2) with a molar mass of approximately 1–2 · 105 g/mol, a hydrodynamic radius of approximately 6–10 nm and a relatively high apparent density (approx. 70–150 kg/m3).

  • 27.
    Chamoun, Ninus
    et al.
    KTH, School of Chemical Science and Engineering (CHE).
    Kjellvertz, Viktor
    KTH, School of Chemical Science and Engineering (CHE).
    Mahajan, William
    KTH, School of Chemical Science and Engineering (CHE).
    Song, Yuanchao
    KTH, School of Chemical Science and Engineering (CHE).
    Fate of Heavy Metals in Waste to Energy (WtE) Processes2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This study was made to increase the understanding of how heavy metals in the aqueous phase are removed at low initial concentrations in different pH and Eh values. The reaction that has been studied is mainly hydroxide precipitation and adsorption in a condensate treatment. In the study, data from one of Vattenfalls waste incinerators was analysed and the results from the data were then compared to previous studies. To increase the understanding, modelling of the heavy metals behaviour in the given concentrations was then made with Medusa and PHREEQC. The heavy metals that were analysed were Sb, As, Pb, Zn, Cr, and Cd. The low initial concentration that vary between 36.1-23600 μg/l complicates the removal process because it corresponds in a low driving force and the results are hard to compare to other studies since the initial concentrations vary between 10-100 mg/l.

    From the modelling and the measurement data it can be seen that Pb, Zn, Cr, and Cd was removed by hydroxide precipitation at pH 10. According to the speciation calculations, the dominant species at this pH are Pb(OH)

    2 , Cd(OH)2, Zn(OH)2 and Cr(OH)3. For arsenic a clear conclusion could not be drawn from the modelling and the measurement data because of low precision. Due to the limited thermodynamic parameters of antimony in comparison with other heavy metals in the database of Medusa and PHREEQC, the modelling of antimony behaviour in condensate treatment has relatively larger uncertainty is low. The modelling results show that the main species in acidic solutions for antimony is Sb(OH)3 and in basic solutions Sb(OH)-6. Further investigation for antimony in needed for a clear conclusions to be drawn

  • 28.
    Cho, Sung-Woo
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Protein-based Packaging Films, Sheets and Composites: Process Development and Functional Properties2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The depletion of the petroleum resources and a number of environmental concerns led to considerable research efforts in the field of biodegradable materials over the last few decades. Of the diverse range of biopolymers, wheat gluten (WG) stands out as an alternative to synthetic plastics in packaging applications due to its attractive combination of flexibility and strength, high gas barrier properties under low humidity conditions and renewability. The availability of raw materials has also been largely increased with an increase in the production of WG as a low-cost surplus material due to increasing demand for ethanol as fuel. In this study, WG was processed into films, sheets and composites using some of the most widely used techniques including solution casting, compression molding, extrusion and injection molding, accompanying process optimizations and characterization of their functional properties. This thesis consists mainly of six parts based on the purpose of the study. The first part addresses the aging and optical properties of the cast film in order to understand the mechanisms and reasons for the time-dependant physical and chemical changes. The films plasticized with glycerol were cast from acidic (pH 4) and basic (pH11) solutions. The film prepared from the pH 11 solution was mechanically more stable upon aging than the pH 4 film, which was initially very ductile but became brittle with time. It was revealed that the protein structure of the pH 4 film was initially less polymerized/aggregated and the polymerization increased during storage but it did not reach the degree of aggregation of the pH 11 film. During aging, the pH 4 film lost more mass than the pH 11 film mainly due to migration of glycerol but also due to some loss of volatile mass. In addition the greater plasticizer loss of the pH 4 film was presumably due to its initial lower degree of protein aggregation/polymerization. Glycerol content did not significantly change the opacity and pH 4 films showed good contact clarity because of less Maillard reaction. In the second part, the heat-sealability of WG films was investigated, using an impulse-heat sealer, as the sealability is one of the most important properties in the use of flexible packaging materials. It was observed that the WG films were readily sealable while preserving their mechanical integrity. The sealing temperature had a negligible effect on the lap-shear strength, but the peel strength increased with sealing temperature. The lap-shear strength increased with increasing mold temperature and the failure mode changed. The third part describes the possibility of using industrial hemp fibers to reinforce wheat gluten sheets based on evaluation of the fiber contents, fiber distribution and bonding between the fibers and matrix. It was found that the hemp fibers enhanced the mechanical properties, in which the fiber contents played a significant role in the strength. The fiber bonding was improved by addition of diamine as a cross-linker, while the fiber distribution needed to be improved. The fourth part presents a novel approach to improve the barrier and mechanical properties of extruded WG sheets with a single screw extruder at alkaline conditions using 3-5wt.% NaOH with or without 1 wt.% salicylic acid. The oxygen barrier, at dry conditions, was improved significantly with the addition of NaOH, while the addition of salicylic acid yielded poorer barrier properties. It was also observed that the WG sheets with 3 wt.% NaOH had the most suitable combination of low oxygen permeability and relatively small time-dependant changes in mechanical properties, probably due to low plasticizer migration and an optimal protein aggregation/polymerization. In the fifth part WG/PLA laminates were characterized for the purpose of improving the water barrier properties. The lamination was performed at 110°C and scanning electron microscopy showed that the laminated films were uniform in thickness. The laminates significantly suppressed the mass loss and showed promising water vapor barrier properties in humid conditions indicating possible applications in packaging. The final part addresses the development of injection molding processes for WG. Injection-molded nanocomposites of WG/MMT were also characterized. WG sheets were successively processed using injection molding and the process temperatures were found to preferably be in a range of 170-200°C, which was varied depending on the sample compositions. The clay was found to enhance the processability, being well dispersed in the matrix. The natural clay increased the tensile stiffness, whereas the modified clay increased the surface hydrophobicity. Both clays decreased the Tg and increased the thermal stability of the nanocomposites. The overall conclusion was that injection molding is a promising method for producing WG items of simple shapes. Further studies will reveal if gluten can also be used for making more complex shapes.

  • 29.
    Chondrogiannis, Georgios
    KTH, School of Chemical Science and Engineering (CHE).
    Pretreatmenteffect on induction time and polymorphic outcome of tolbutamide crystallizationin 1-propanol2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this project, the effect of solution thermal and structural history on nucleation was investigated. Many researchers have shown that temperature and duration of pretreatment has an influence on induction time, polymorphic outcome and metastable zone width. Here, solution of tolbutamide in 1-propanol was first prepared with same conditions, to “standardize” and control the initial solution history. Next, pretreatment of varied duration and temperature was applied to introduce different solution history. Then, nucleation began in 9℃, and induction time and polymorphic outcome were measured. Two batches of 30 isolated nucleation experiments each, were done per set of conditions. The results showed an impact on induction time and polymorphic outcome. However, this change cannot be clearly correlated with the conditions of pretreatment. Furthermore, the deviation between series of experiments that were performed under the same set of conditions, showed that the parameters affecting induction time and polymorphism were not controlled sufficiently to reach a safe conclusion.

    Moreover, the effect of solution filtration right before nucleation was investigated. This filtration step decreased experimental induction time from 160 minutes to less than 5. It is possible that this filtration step removed the solution’s structural memory, which accelerated nucleation. However, the effect of evaporation on concentration for example, or other parameters was not investigated.

    Furthermore, the effect of using filtration with 0.1 and 0.2 μm filters was examined. It was found that using 0.1 filter results in decreased median induction time by a factor of 4. Finally, filtration before standardization resulted in a 1.5% increase in concentration compared to solution that was not filtered. Filtration with 0.1 μm filter before standardization decreased median induction time by a factor of 4, as compared to using a 0.2 μm filter.

  • 30. Cracknell, R. F.
    et al.
    Head, R. A.
    McAllister, L. J.
    Andrae, Johan
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Octane sensitivity in gasoline fuels containing nitro-alkanes: A possible means of controlling combustion phasing for HCCI2009In: SAE technical paper series, ISSN 0148-7191Article in journal (Refereed)
    Abstract [en]

    Addition of nitroalkanes to gasoline is shown to reduce the octane quality. The reduction in the Motor Octane Number (MON) is greater than the reduction in the Research Octane Number (RON). In other words addition of nitroalkanes causes an increase in octane sensitivity. The temperature of the compressed air/fuel mixture in the MON test is higher then in the RON test. Through chemical kinetic modelling, we are able to show how the temperature dependence of the reactions responsible for break-up of the nitroalkane molecule can lead to an increase in octane sensitivity. Results are presented from an Homogenous Charge Compression Ignition (HCCI) engine with a homogeneous charge in which the air intake temperature was varied. When the engine was operated on gasoline-like fuels containing nitroalkanes, it was observed that the combustion phasing was much more sensitive to the air intake temperature. This suggests a possible means of controlling combustion phasing for HCCI.

  • 31.
    Cunha, Gisera
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. INRA, Biopolymeres Interact & Assemblages, France.
    Mougel, Jean-Bruno
    Cathala, Bernard
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Capron, Isabelle
    Preparation of Double Pickering Emulsions Stabilized by Chemically Tailored Nanocelluloses2014In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, no 31, p. 9327-9335Article in journal (Refereed)
    Abstract [en]

    Nanocelluloses are bio-based nanoparticles of interest as stabilizers for oil-in-water (o/w) Pickering emulsions. In this work, the surface chemistry of nanocelluloses of different length, nanofibrillated cellulose (NFC, long) and cellulose nanocrystals (CNC, short), was successfully tailored by chemical modification with lauroyl chloride (C12). The resulting nanofibers were less hydrophilic than the original and able to stabilize water-in-oil (w/o) emulsions. The combination of the two types of nanocelluloses (C12-modified and native) led to new surfactant-free oil-in-water-in-oil (o/w/o) double emulsions stabilized by nanocellulose at both interfaces. Characterization was performed with respect to droplet size distribution, droplet stability over time, and stability after centrifugation. Nanocellulose-based Pickering emulsions can be designed with a substantial degree of control, as demonstrated by the stability of the chemically tailored NFC double emulsions. Furthermore, it was demonstrated that increased nanofiber length leads to increased stability.

  • 32.
    Done, Victoria
    KTH, School of Chemical Science and Engineering (CHE).
    General description of measures for environmental compliance of substations owned by Svenska kraftnät in protected areas with focus on oil spill2014Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Svenska kraftnät is the Swedish transmission system operator, responsible for the national electrical grid with power lines of 220 kV and 400 kV, and the electrical substations of the grid. In this master thesis an old substation located in a sensitive environmental area is inspected and its environmental risks defined and assessed. From this “worst case scenario” measures are recommended, that should be applicable on other existing substations, and for new constructed substations. This thesis is limited to a more detailed analysis on how oil spill can be handled. The insulating oil is used in different machines and equipment on the substation to avoid electrical charges.

    The inspected substation has a special feature; a pipe system that connects wells on the substation area, water pipes from the substation house, and transformer pits to an oil-water separation house. The oil pits are made of concrete and placed under machines with large amounts of oil to capture the oil in case of a breakdown or leakage. In the oil-water separation house oil is separated from water and the clean water is sent to a lake in the vicinity. The most severe environmental risks found are the filter in the oil-water separation house and the risk of oil leakage from the open water-cooling system of the synchronous generator. In addition, there is no way to catch oil spill from current and voltage transformers and it is not known if the pipe system that transports water and oil spills is completely sealed. Finally, there is no permanent installation to catch spills from tank filling areas and Svenska kraftnät does rarely follow up the environmental work of the entrepreneurs.

    Svenska kraftnät is recommended to use the products and services from the companies Qlean Scandinavia AB and TTL Miljöteknik AB to attend to the noted environmental risks. Qlean Scandinavia AB offers an environmental friendly cleaning procedure with ultraclean water and sealing of concrete, which can be used for the transformer pits and oil-water separation house. They also sell profile planks as a fire-extinguishing layer for transformer pits. These are considered better and safer than the conventional stones used. The price is almost the same, however the maintenance costs are lower for the profile planks, since they are easier to clean and do not require heavy transports to landfill. They also require less space than the stones, therefore a smaller transformer pit can be built, and cost savings can be made on concrete.

    TTL Miljöteknik AB has products based on environmental friendly oil solidifying polymers placed in different textiles and filters. They let water and other substances pass, but react with hydrocarbons, like oil, forming a tight rubberlike mass. These installations are new to Europe, but more than 12 000 installations have been made, mainly in the United States and Australia. For the inspected substation in this thesis it is recommended to manage oil spill at each machine and to clean the pipe system. An HFF-filter should be installed in cleaned and sealed transformer pits. The filter lets water from precipitation pass, but binds oil, thanks to the solidifying polymers. The clean water is further transported through the pipe system to the oil-water separation house and from there water is pumped to the lake. Wells must be sealed and the pipes from the substation house led to a septic tank. Agent X, a type of filter mat, should be placed on the substation area to catch oil spills from current and voltage transformers, since previous breakdowns show that oil can be spread over a large area.

    For plants without a pipe system the water will be released outside the transformer pits. For new constructions it is suggested that transformer pits are built with a polyvinyl mat in the bottom and a filter on the sides, which will capture the oil. A concrete fundament still needs to be built to support the machine; therefore the price will almost be the same as for the conventional transformer pit in concrete, although less concrete is needed. However, with this technique the transformer pit will not require any maintenance.

  • 33.
    Du, Jian
    et al.
    Dalian Univ Technol, State Key Lab Fine Chem, DUT KTH Joint Educ & Res Ctr Mol Devices, Dalian 116024, Peoples R China..
    Li, Fei
    Dalian Univ Technol, State Key Lab Fine Chem, DUT KTH Joint Educ & Res Ctr Mol Devices, Dalian 116024, Peoples R China..
    Wang, Yong
    Dalian Univ Technol, State Key Lab Fine Chem, DUT KTH Joint Educ & Res Ctr Mol Devices, Dalian 116024, Peoples R China..
    Zhu, Yong
    Dalian Univ Technol, State Key Lab Fine Chem, DUT KTH Joint Educ & Res Ctr Mol Devices, Dalian 116024, Peoples R China..
    Sun, Licheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. Dalian Univ Technol, State Key Lab Fine Chem, DUT KTH Joint Educ & Res Ctr Mol Devices, Dalian 116024, Peoples R China..
    Cu3P/CuO Core-Shell Nanorod Arrays as High-Performance Electrocatalysts for Water Oxidation2018In: Chemelectrochem, ISSN 2196-0216, Vol. 5, no 15, p. 2064-2068Article in journal (Refereed)
    Abstract [en]

    Earth-abundant transition-metal-based oxides are potential candidates to replace the state-of-the-art noble-metal-based oxygen evolution catalysts (OECs) such as IrO2 and RuO2. Despite the low cost and large abundance, copper-based OER catalysts have been less frequently studied, mainly owing to the low electrical conductivity of copper oxides that results in large overpotential and sluggish kinetics for oxygen evolution. We report here the insitu fabrication of semi-metallic Cu3P nanorod arrays on commercial copper foam via a template approach; the resulting self-supported core-shell Cu-Cu3P/CuO electrode has the merits of high electrical conductivity, large active area, and short diffusion paths for electrolyte and evolved oxygen, exhibiting a low overpotential of 315mV and high durability over 50h at a current density of 10mAcm(-2) for OER in 1.0 M KOH. The remarkable OER performance reported here is not only superior to that of analogous Cu-CuO foam electrode, but also outperforms those of copper-based OER electrocatalysts in the literature.

  • 34.
    EDRISI, KEYVAN
    KTH, School of Chemical Science and Engineering (CHE).
    Fastställande av PGM-tillgänglighet för dieseloxidationskatalysator med hjälp av kemisorption2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Diesel Oxidation Catalyst (DOC) is subjected to harsh conditions, causing its performance to

    diminish over time as the result of different aging mechanisms, which either decreases or lowers the

    accessibility to the catalyst’s active sites. Previous work using chemisorption to quantify aging progression

    has resulted in a reproducibility of 17%. In this study it has been attempted to lower this, while

    also performing performance evaluations to see if correlations exist between dispersion and Light-Off

    Temperature (LOT).

    Two catalysts have been investigated, LLC (Low Loading Catalyst) and HLC (High Loading Catalyst).

    These were hydrothermally aged at 600 C, 700 C and 800 C. In addition to these, two HLC engine cell

    samples were also investigated.

    To ensure sample homogeneity, different sample preparation methods were investigated. Catalyst samples

    were crushed, or had their washcoat layer removed, or were milled and then sieved. A total of 5 runs were

    done using fresh catalysts of LLC and HLC to calculate the standard deviation. Evaluation of performance

    was done on all samples using Synthetic Catalyst Activity Testing (SCAT).

    It was deemed that the only viable sample preparation method was to mill and sieve as other methods

    would be hard to reproduce. The results showed that the reproducibility for LLC was %STD = 4% and

    for HLC %STD = 2%. For LLC, a correlation between catalytic activity and dispersion was found. The

    activity dropped with respect to the dispersion in a close to linear fashion without a large effect on BET

    surface area. For HLC the dispersion decreased largely upon hydrothermal aging, however no correlation

    was found with the activity; only when aged at 800 C a significant change in LOT was noted. The BET

    surface area measurements were inconsistent. Lower dispersion sometimes resulted in higher surface area.

    Engine cell samples exhibited notable decrease in dispersion, but not in surface area, and did not correlate

    to the hydrothermally aged catalysts, which might be due to other effects inhibiting CO chemisorption

    during measurements.

  • 35.
    Eita, Mohamed
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    In situ study of the adsorption of humic acid on the surface of aluminium oxide by QCM-D reveals novel features2011In: SOFT MATTER, ISSN 1744-683X, Vol. 7, no 2, p. 709-715Article in journal (Refereed)
    Abstract [en]

    Novel features of the adsorption of humic acid on the surface of aluminium oxide were revealed by means of an in situ study by quartz crystal microbalance with dissipation (QCM-D). The adsorption of humic acid on the surface of aluminium oxide shows a special case at pH 3 where the adsorption takes place in two steps. Each step has characteristic thickness, kinetics and viscoelasticity. While the first step shows low thickness, fast kinetics and almost no viscoelastic character, indicating a rigidly adsorbed humic acid monolayer, the second step is of much higher thickness, slower kinetics and with significant viscoelastic character, indicating a large diffuse layer with significant bulk contributions. In contrast, adsorption at pH 5 and 6.8 was found to be limited to a monolayer which is more rigid at pH 5 than at pH 6.8. Ellipsometry and X-ray photoelectron spectroscopy (XPS) were used to prove and quantify the adsorption in the dry state. The monolayer thickness measured by ellipsometry is close to the Sauerbrey thickness obtained by QCM-D. Adsorption takes place at a dilute concentration of 1 mg L-1, followed by saturation at a concentration of 10-20 mg L-1. XPS spectra of the carbon 1s peak indicated almost no desorption of the adsorbed humic acid layer after immersion in water for 48 hours, implying irreversible adsorption based on a strong binding between humic acid and aluminium oxide.

  • 36.
    Endrodi, Balazs
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Smulders, Vera
    Univ Twente, Fac Sci & Technol, MESA Inst Nanotechnol, PhotoCatalyt Synth Grp, Meander 229,POB 217, NL-7500 AE Enschede, Netherlands..
    Simic, Nina
    Nouryon, SE-44580 Bohus, Sweden..
    Wildlock, Mats
    Nouryon, SE-44580 Bohus, Sweden..
    Mul, Guido
    Univ Twente, Fac Sci & Technol, MESA Inst Nanotechnol, PhotoCatalyt Synth Grp, Meander 229,POB 217, NL-7500 AE Enschede, Netherlands..
    Mei, Bastian
    Univ Twente, Fac Sci & Technol, MESA Inst Nanotechnol, PhotoCatalyt Synth Grp, Meander 229,POB 217, NL-7500 AE Enschede, Netherlands..
    Cornell, Ann M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    In situ formed vanadium-oxide cathode coatings for selective hydrogen production2019In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 244, p. 233-239Article in journal (Refereed)
    Abstract [en]

    Electrode selectivity towards hydrogen production is essential in various conversion technologies for renewable energy, as well as in different industrial processes, such as the electrochemical production of sodium chlorate. In this study we present sodium metavanadate as a solution additive, inducing selective cathodic formation of hydrogen in the presence of various other reducible species such as hypochlorite, chlorate, oxygen, nitrate, hydrogen-peroxide and ferricyanide. During electrolysis a vanadium-oxide coating forms from the reduction of sodium metavanadate, explaining the observed enhanced selectivity. The hydrogen evolution reaction proceeds without significantly altered kinetics on such in situ modified electrode surfaces. This suggests that the reaction takes place at the interface between the electrode surface and the protective film, which acts as a diffusion barrier preventing the unwanted species to reach the electrode surface.

  • 37.
    Endrodi, Balázs
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry. Department of Physical Chemistry and Materials Science, University of Szeged, Szeged, Hungary.
    Sandin, Staffan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Wildlock, Mats
    Simic, Nina
    Cornell, Ann M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Suppressed oxygen evolution during chlorateformation from hypochlorite in the presenceof chromium(VI)2019In: Journal of chemical technology and biotechnology (1986), ISSN 0268-2575, E-ISSN 1097-4660, Vol. 94, no 5, p. 1520-1527Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Chromium(VI) is a crucial electrolyte component in industrial chlorate production. Due to its toxicity, iturgently needs to be abandoned and its functions fulfilled by new solutions. In the industrial production of sodium chlorate,homogeneous decomposition of the hypochlorite intermediate to chlorate is a key step. As a competing loss reaction,hypochlorite can decompose to oxygen. How chromium(VI) affects these reactions is not well understood.

    RESULTS: This work shows, for the first time, that chromium(VI) selectively accelerates the chlorate formation from hypochloriteboth in dilute and concentrated, industrially relevant solutions. The effect of the ionic strength and the specific contributionof different electrolyte components were systematically studied. By simultaneously measuring the concentration decayof hypochlorite (UV–vis spectroscopy) and the oxygen formation (mass spectrometry), both the rate and the selectivity of thereactions were evaluated.

    CONCLUSION: In the presence of chromium(VI) the hypochlorite decomposition is described by the sum of an uncatalyzedand a parallel catalyzed reaction, where oxygen only forms in the uncatalyzed reaction. When removing chromium(VI),the homogeneous oxygen formation increases, causing economic and safety concerns. The need for a catalyst selectivefor chlorate formation is emphasized.

  • 38.
    Endrődi, Balázs
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Sandin, Staffan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Smulders, V.
    Simic, N.
    Wildlock, M.
    Mul, G.
    Mei, B. T.
    Cornell, Ann
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Towards sustainable chlorate production: The effect of permanganate addition on current efficiency2018In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 182, p. 529-537Article in journal (Refereed)
    Abstract [en]

    Sodium dichromate is an essential solution additive for the electrocatalytic production of sodium chlorate, assuring selective hydrogen evolution. Unfortunately, the serious environmental and health concerns related to hexavalent chromium mean there is an urgent need to find an alternative solution to achieve the required selectivity. In this study sodium permanganate is evaluated as a possible alternative to chromate, with positive results. The permanganate additive is stable in hypochlorite-containing solutions, and during electrolysis a thin film is reductively deposited on the cathode. The deposit is identified as amorphous manganese oxide by Raman spectroscopic and X-ray diffraction studies. Using different electrochemical techniques (potentiodynamic measurements, galvanostatic polarization curves) we demonstrate that the reduction of hypochlorite is suppressed, while the hydrogen evolution reaction can still proceed. In addition, the formed manganese oxide film acts as a barrier for the reduction of dissolved oxygen. The extent of hydrogen evolution selectivity in hypochlorite solutions was quantified in an undivided electrochemical cell using mass spectrometry. The cathodic current efficiency is significantly enhanced after the addition of permanganate, while the effect on the anodic selectivity and the decomposition of hypochlorite in solution is negligible. Importantly, similar results were obtained using electrodes with manganese oxide films formed ex situ. In conclusion, manganese oxides show great promise in inducing selective hydrogen evolution, and may open new research avenues to the rational design of selective cathodes, both for the chlorate process and for related processes such as photocatalytic water splitting.

  • 39.
    Eriksson, Adam
    et al.
    KTH, School of Chemical Science and Engineering (CHE).
    Kürten, Charlotte
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Syrén, Per-Olof
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Protonation-Initiated Cyclization by a ClassII Terpene Cyclase Assisted by Tunneling2017In: ChemBioChem (Print), ISSN 1439-4227, E-ISSN 1439-7633, Vol. 18, no 23, p. 2301-2305Article in journal (Refereed)
    Abstract [en]

    Terpenes represent one of the most diversified classes of natural products with potent biological activities. The key to the myriad of polycyclic terpene skeletons with crucial functions in organisms from all kingdoms of life are terpene cyclase enzymes. These biocatalysts enable stereospecific cyclization of relatively simple, linear, prefolded polyisoprenes by highly complex, partially concerted, electrophilic cyclization cascades that remain incompletely understood. Herein, additional mechanistic light is shed on terpene biosynthesis by kinetic studies in mixed H2O/D2O buffers of a classII bacterial ent-copalyl diphosphate synthase. Mass spectrometry determination of the extent of deuterium incorporation in the bicyclic product, reminiscent of initial carbocation formation by protonation, resulted in a large kinetic isotope effect of up to seven. Kinetic analysis at different temperatures confirmed that the isotope effect was independent of temperature, which is consistent with hydrogen tunneling.

  • 40.
    Gara Ramos, Rodriguez
    KTH, School of Chemical Science and Engineering (CHE).
    Nitrate and phosphate removal from aqueous solution by biochar and agroforestry residues2012Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
  • 41.
    Garemark, Jonas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Studies of the Impregnation Stagein Kraft Pulping of Hardwood2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In kraft pulping, one of the main issues is the extensive wood losses. With increasing prices ofwoody biomass an incentive towards minimizing the wood losses exists. Amongst the variousprocess steps, the impregnation of wood chips has shown to enhance the cooking by providinga homogeneous distribution of chemicals inside the chips. It is proven that a more proficientimpregnation phase can improve the overall yield in kraft pulping. However, there is a lack ofscientific research comparing different impregnation techniques for hardwood. Hence, thisthesis will attempt to clarify the impregnation of hardwood.The impregnation efficiency was studied by comparing three different impregnation methods:High Alkali Impregnation (HAI), Extended Impregnation (EI) using a low alkali level and aReference Impregnation (REF) to enable a comparison to the industrially establishedconditions. The cases were compared by analysing the yield, selectivity and homogeneity. Thecomparison was also made under cooking conditions with the objective to understand theimpact of impregnation on the subsequent cooking phase. The cooking procedure was assessedby analysing the degree of delignification, yield and reject content.In impregnation, most chemical consuming reactions occurred within the first 10-30 minutes,mainly contributed by deacetylation. HAI obtained the fastest homogeneous distribution of OH-(~60 min), but the fastest dissolution of wood. The effect was contributed by the high [OH-],providing fast diffusion of ions and rapid dissolution of xylan. In the contrary, EI attained thehighest impregnation yield after a given impregnation time but required a prolonged durationto obtain a chemical equilibrium between the free and bound liquor (~120 min). REF showeda higher yield than HAI and similar chemical equilibrium as EI. The hydrosulphide sorption inimpregnation was highest for EI due to the high initial sulphidity charge and similar for REFand HAI. For impregnations at 115°C, the HS- sorption was significantly increased for all cases,resulting from delignification. In the subsequent cooking phase, it was prevalent that impregnation of chips under EIconditions were easier delignified, leading to a reduced cooking time to reach the defibrationpoint. Birch was more prone to delignification than eucalyptus. In turn, eucalyptus also obtaineda higher defibration point. Highest total cooking yield at similar kappa numbers was achievedwith REF conditions, followed by HAI and lastly the EI conditions. The high yield of REF incontrast to HAI could be explained by an improved xylan yield due to an alleviated hydroxidelevel. The low yield of EI can be assigned to continues peeling due to the prolongedimpregnation and loss of xylan when removing black liquor after impregnation. In terms ofproduction rate, yield, energy and chemical consumption the REF is the most efficientimpregnation condition for birch kraft cooking in this batchwise laboratory kraft cookingprocedure.

  • 42.
    Ghadami Yazdi, Milad
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    H. Moud, Pouya
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology. KTH.
    Marks, Kess
    Piskorz, Witold
    Öström, Henrik
    Hansson, Tony
    Kotarba, Andrzej
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Göthelid, Mats
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    Naphthalene on Ni(111): experimental and theoretical insights into adsorption, dehydrogenation and carbon passivationManuscript (preprint) (Other academic)
    Abstract [en]

    An attractive solution to mitigate tars and also to decompose lighter hydrocarbons in biomass gasification is secondary catalytic reforming, converting hydrocarbons to useful permanent gases. Albeit in use for long time in fossil feedstock catalytic steam reforming, the understanding of the catalytic processes is still limited. Naphthalene is typically present in the biomass gasification gas and to further understand the elementary steps of naphthalene transformation, we investigated the temperature dependent naphthalene adsorption, dehydrogenation and passivation on Ni(111). TPD (temperature programmed desorption) and STM (scanning tunneling microscopy) in ultra-high vacuum environment from 110 K up to 780 K, combined with DFT (density functional theory) were used in the study. Room temperature adsorption results in a flat naphthalene monolayer. DFT favors the di-bridge[7] geometry but the potential energy surface is rather smooth. DFT also reveals a pronounced dearomatization and charge transfer from the adsorbed molecule into the nickel surface. Dehydrogenation occurs in two steps, with two desorption peaks at approximately 450 K and 600 K. The first step is due to partial dehydrogenation generating active hydrocarbon species that at higher temperatures migrates over the surface forming graphene. The graphene formation is accompanied by desorption of hydrogen in the high temperature TPD peak. The formation of graphene effectively passivates the surface both for hydrogen adsorption and naphthalene dissociation. In conclusion, the obtained results on the model naphthalene and Ni(111) system, provides insight into elementary steps of naphthalene adsorption, dehydrogenation and carbon passivation, which may serve as a good starting point for rational design, development and optimization of the Ni catalyst surface, as well as process conditions, for the aromatic hydrocarbon reforming process.

  • 43. Gomez, R. Y.
    et al.
    Nuran, Zaini Ilam
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Yang, Weihong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Helsen, L.
    Landfill solid waste-based syngas purification by a hybrid pulsed corona plasma unit2019In: European Biomass Conference and Exhibition Proceedings, ETA-Florence Renewable Energies , 2019, p. 520-522Conference paper (Refereed)
    Abstract [en]

    Gasification of excavated Municipal Solid Waste (MSW) for energy and materials recovery has been seen as a solution for current energetic, environmental and land availability issues. However, it poses many technological challenges, and among them the most difficult is to obtain of a tar-free syngas. In this work, two set of experiments were performed in order to obtain a syngas from MSW with a low tar content. In the first stage, MSW gasification was performed in order to identify the tar yield and composition at different temperatures using air and steam. After that, the most representative tar compound, naphthalene, was selected to perform tar cracking experiments in a pulsed corona plasma reactor able to operate from ambient temperature up to 1200ᵒC. The results of these experiments show that the pulsed corona plasma can enhance the tar thermal cracking reactions, reducing by 200ᵒC the temperature at which 100% of the naphthalene is converted.

  • 44.
    Gomez, Yasna Acevedo
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Oyarce, Alejandro
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Ammonia contamination of a proton exchange membrane fuel cell2018In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 165, no 3, p. F189-F197Article in journal (Refereed)
    Abstract [en]

    Reformate hydrogen from biogas is an attractive fuel alternative for energy conversion in PEM fuel cells. However, in the reformate traces of ammonia may be found, e.g. if the biogas is produced from agricultural resources. In this investigation the effect of ammonia in the fuel gas, on each part of the fuel cell, is studied by cyclic voltammetry, electrochemical impedance spectroscopy (EIS), symmetrical hydrogen cell (H2|H2)- and real fuel cell operation. A considerable degradation in performance is observed by introducing 200 ppm ammonia. The results show that ammonia not only affects the polymer electrolyte membrane but also the oxygen reduction reaction (ORR) and catalyst ionomer in both electrodes, whereas the hydrogen oxidation reaction (HOR) is the worst affected. In the short-term, the performance is reversible if running the cell on neat hydrogen after ammonia exposure, but this does not apply for long-term exposure. A mitigation method with air bleed is tested but gives no improvement of the performance.

  • 45.
    GONZALEZ NOVOA, NIKLAS
    KTH, School of Chemical Science and Engineering (CHE).
    Katalytisk framställning av syntetisk naturgas (SNG)2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of the  study  was to study  the  performance of nickel-based  catalysts  in the  production  of synthetic  natural  gas from synthesis gas (CO and H,). Nickel-based catalysts are preeminent catalysts in  this  reaction   due  to  their   high activity  and  selectivity  to  methane.  Nevertheless,   these   are threatened by severe  intrinsic deactivation  phenomena. In  more  detail, the goal of this work is to study   the   influence   of  different   catalyst   properties  on   the   three    most  severe   deactivation mechanisms  (nickel carbonyl formation,  carbon formation  and thermal  sintering). For that  purpose,  alumina-supported nickel catalysts containing  30 wt% Ni and promoted with Zr02, MgO, CaO and BaO were  prepared  and tested  in a high pressure  catalytic reactor.   The experimental work was divided in 3 parts according to specific study goals.

    The first  part of the  work consisted  in the  study  of the  catalyst  pellet size on deactivation due  to nickel carbonyl  formation. For that  purpose,  the  non-promoted  alumina-supported  nickel catalyst

    was tested  at 20 bar and 310 oc using three  different  pellet sizes. It was found  and  proved that  the

    use of large catalyst  pellet sizes significantly suppresses this  kind of deactivation. The results  were scientifically explained  by the influence of internal mass transfer phenomena. In order  to support this conclusion,  COMSOL multihpysics computations were  performed  to estimate internal  temperature and concentration profiles for the different  pellet sizes.

    The second  part of the  work was focused  on the effect of the selected  promoters on the  resistance towards  carbon  formation. For that  purpose, the different  catalysts  were tested  at 310 oc, 1 bar and

    a H,/C0=3; conditions  at which the carbon formation  is favorable. The spent  samples  were analyzed by means  of temperature-programmed hydrogenation  analyses  in order  to quantify the  amount  of carbon  formed. It was found  that  the  use of Zr02,  in particular,  significantly reduces  the  rate  of carbon formation.

    The third  part  of  the  work  consisted  in studying  the  effect  of these   promoters on  the  catalyst resistance  towards thermal  sintering.  For that  purpose,  the  different  catalysts  were  exposed  to an

    accelerated aging  procedure (690 oc and  H20/H2=2). The intrinsic catalytic activity of the  catalysts

    was  then  determined for  both  the  fresh  and  aged  samples   by testing  these  at  non-deactivating conditions  (300 oc, 1 bar and  H,jC0=9).  No clear  improvement neither  decline  in catalyst  stability

    was observed for any of the promoted  catalyst samples.

  • 46.
    González, María del Carmen
    et al.
    Universidad Autónoma Metropolitana, Unidad Azcapotzalco.
    Ramírez, Andrés
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.).
    Portilla, Margarita
    Universidad Autónoma Metropolitana, Unidad Azcapotzalco.
    Ramírez, Javier
    Universidad Autónoma Metropolitana, Unidad Azcapotzalco.
    APPLYING THE CASE METHOD AND COMMUNITY – BASED LEARNING FINAL PROJECT IN A CHEMICAL ENGINEERING COURSE AT A PUBLIC UNIVERSITY IN MEXICO2012In: International Journal of Case Method Research & Application, ISSN 1554-7752, Vol. 24, no 3, p. 187-191Article in journal (Refereed)
    Abstract [en]

    The case describes the use of the case method in a capstone course called ‘Terminal Project’ in the Chemical Engineering Department at the Autonomous Metropolitan University (UAM), Campus Azcapotzalco, in Mexico City.

    The purpose of applying the case method in the course was to make use of the students’ previously acquired knowledge in solving a real problem. The project also takes into account one of UAM’s general objectives, to provide community support for sustainable development [Universidad Autonoma Metropolitana, 2011]. Furthermore, the application exemplifies the case method as a useful integrating technique suitable for different types of teaching environments in Mexico, reaching beyond the prevailing practice of using cases to learn about managerial issues in private business schools.

    Through the methodology described. The students were able to retrieve the information that they felt was missing to find a proper solution to the vanilla harvest problem. Based on the answers from the people interviewed, the four students had the opportunity to go a step further in analyzing the case setting.

  • 47.
    Gupta, Apoorv
    KTH, School of Chemical Science and Engineering (CHE).
    Vätgaslagring, -distribution och -rening2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Rising greenhouse gas (GHG) emissions is a major cause of concern today. The primary source of energy all over the globe is fossil fuels, a non-renewable source of energy that is expected to get exhausted in the next 60-100 years. Damage to environment cannot be easily reversed but the initial steps are to reduce the damage done.  Other alternative cleaner sources of energy are being looked into as viable options to replace fossil fuels. The objective of this study is to identify options for using hydrogen as an energy carrier in the future with a major focus on the transportation sector. This project is limited to theoretical study looking into the options for hydrogen storage and distribution. Gaseous and liquid hydrogen storage have been looked in to thoroughly and are far from meeting Department of Energy, USA, (DOE) ultimate targets for automobile fleets, hence a shift to other storage options is imminent. Metal hydride storage is believed to be the upcoming technology as the mid-term solution to storage issues and hence is given a lot of attention in this project. On-board storage in metal hydrides is studied and it can be concluded that no metal hydride known to us today is capable of satisfying the DOE ultimate targets. Finally, the study ends with options accessible to AGA to purchase hydrogen within Sweden and how they can be cleaned to meet the fuel cell gas purity requirements. 

  • 48.
    GUTIÉRREZ VARONA, PABLO
    KTH, School of Chemical Science and Engineering (CHE).
    Experimental testing of catalysts for hybrid combustion2013Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A hybrid heating system for the vehicle industry was customized at the Chemical Engineering and Technology unit, KTH School of Chemical Science and Engineering. This work was performed by Pablo Gutiérrez Varona as his final project work and was carried out in co-operation between KTH-Royal Institute of Technology, Universitat de Barcelona, and ReformTech Heating Technologies Sweden AB.

    The aim of the thesis was to evaluate the performance of three different catalysts (an uncoated cordierite, a lanthanum manganese hexaaluminate, and palladium over alumina) for a 5 kW adiabatic power hybrid heater developed by ReformTech Heating Technologies Sweden AB. Three different catalysts were tested for the combustion of diesel. The catalysts performances were observed for a wide working range of air-to-fuel ratios in order to find an optimum operation point. The catalysts were evaluated based on the emissions and temperatures profiles.

    The most promising results for this application was the Pd-Al2O3 catalyst, 2 CO ppm and 37 NOx ppm for a lambda of 2,3.

  • 49.
    GÓMEZ AGUILERA, Miguel
    KTH, School of Chemical Science and Engineering (CHE).
    Metaloxid katalysatorer för oxidering av kolmonoxid och förbränning av sot2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of this work was to manufacture and test non noble metal catalysts for CO oxidation and soot combustion. The feeding gases consist in the products of the combustion diesel in a Reformtech heater. These gases contain CO, CO2, H2O as well as small amounts of NOx and hydrocarbons.

    Two different catalysts were prepared for CO oxidation, based on cobalt oxide supported on ceria. 12Co/CeO2 with 12% weight of cobalt and 15CoOx/CeO2 with 15%. The first one was prepared by impregnation of cobalt nitrates in cerium oxide support; the second one was prepared by co-precipitation of cobalt and cerium nitrates.

    Another catalyst called 12Co4.5K/CeO2, with 12% cobalt and 4.5% potassium, was made for the simultaneous combustion of soot and oxidation of CO. The base also consisted in cobalt oxide supported on ceria, but with the addition of potassium which could stabilize the cobalt oxide particles.

    Both co-precipitation and impregnation methods gave the desired catalyst structure in the CO oxidation catalysts and both catalysts (12Co/CeO2 and 15CoOx/CeO2) showed activity. Nevertheless, the activity was lower than desired due to low surface area and mass transfer limitations. The catalysts also deactivated in less than three hours on stream, probably due to poisoning.

    The co-precipitation method for the 12Co4.5K/CeO2 catalyst gave the desired cobalt and cerium oxides, but no conclusion can be drawn regarding potassium since it was not shown in the XRD tests.

    The catalyst for both CO oxidation and soot combustion (12Co4.5K/CeO2) showed no activity for any of the reactions. Nevertheless, the tests performed to test the soot combustion ability were not conclusive and should be improved in future studies.

  • 50.
    H. Moud, Pouya
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Catalytic Conversion of Undesired Organic Compounds to Syngas in Biomass Gasification and Pyrolysis Applications2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Reliable energy supply is a major concern and crucial for development of the global society. To address the dependency on fossil fuel and the negative effects of this reliance on climate, there is a need for a transition to cleaner sources. An attractive solution for replacing fossil-based products is renewable substitutes produced from biomass. Gasification and pyrolysis are two promising thermochemical conversion technologies, facing challenges before large-scale commercialization becomes viable. In case of biomass gasification, tar is often and undesired by-product. An attractive option to convert tar into syngas is nickel-based catalytic steam reforming (SR). For biomass pyrolysis, catalytic SR is in early stages of investigation as a feasible option for bio-crude conversion to syngas.

    The focus of the thesis is partly dedicated to describe research aimed at increasing the knowledge around tar reforming mechanisms and effect of biomass-derived impurities on Ni-based tar reforming catalyst downstream of gasifiers. The work focuses on better understanding of gas-phase alkali interaction with Ni-based catalyst surface under realistic conditions. A methodology was successfully developed to enable controlled investigation of the combined sulfur (S) and potassium (K) interaction with the catalyst. The most striking result was that K appears to lower the sulfur coverage and increases methane and tar reforming activity. Additionally, the results obtained in the atomistic investigations are discussed in terms of naphthalene adsorption, dehydrogenation and carbon passivation of nickel.

    Furthermore, the thesis describes research performed on pyrolysis gas pre-conditioning at a small-industrial scale, using an iron-based catalyst. Findings showed that Fe-based materials are potential candidates for application in a pyrolysis gas pre-conditioning step before further treatment or use, and a way for generating a hydrogen-enriched gas without the need for bio-crude condensation.

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