Change search
Refine search result
1234567 101 - 150 of 2454
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 101.
    Aminlashgari, Nina
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    SALDI-MS Method Development for Analysis of Pharmaceuticals and Polymer Degradation Products2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Surface assisted laser desorption ionization-mass spectrometry (SALDI-MS) was evaluated as a new tool for analysis of polymer degradation products. A SALDI method was developed enabling rapid analysis of low molecular mass polyesters and their degradation products. In addition, the possibility to utilize nanocomposite films as easy-to-handle surfaces for analysis of pharmaceutical compounds was investigated.

    Poly(ε-caprolactone) was used as a model compound for SALDI-MS method development. The signal-to-noise values obtained by SALDI-MS were 20 times higher compared to traditional matrix assisted laser desorption ionization-mass spectrometry (MALDI-MS) of the same samples with 2,5-dihydroxybenzoic acid as a matrix. Halloysite nanoclay and magnesium oxide showed best potential as surfaces and clean backgrounds in the low mass range were observed. The SALDI-MS method for the analysis of polyester degradation products was also verified by electrospray ionization-mass spectrometry (ESI-MS). An advantage over ESI-MS is the possibility to directly analyze degradation products in buffer solutions. Compared to gas chromatography-mass spectrometry (GC-MS) it is possible to analyze polar compounds and larger molecular mass ranges at the same time as  complicated extraction steps are avoided.

    The possibility to use nanocomposite films as surfaces instead of free nanoparticles was evaluated by solution casting of poly(lactide) (PLA) films with eight inorganic nanoparticles. The S/N values of the pharmaceutical compounds, acebutolol, propranolol and carbamazepine, analyzed on the nanocomposite surfaces were higher than the values obtained on the surface of plain PLA showing that the nanoparticles participated in the ionization/desorption process even when they are immobilized. Beside the ease of handling, the risk for instrument contamination is reduced when nanocomposites are used instead of free nanoparticles. The signal intensities depended on the type of drug, type and concentration of nanoparticle. PLA with 10 % titanium oxide or 10 % silicon nitride functioned best as SALDI-MS surfaces.

  • 102.
    Aminlashgari, Nina
    et al.
    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.
    Emerging Mass Spectrometric Tools for Analysis of Polymers and Polymer Additives2012In: Advances in Polymer Science, ISSN 0065-3195, E-ISSN 1436-5030, Vol. 248, p. 1-38Article in journal (Refereed)
    Abstract [en]

    The field of mass spectrometry has experienced enormous developments in the last few years. New interesting mass spectrometric techniques have arrived and there have been further developments in the existing methods that have opened up new possibilities for the analysis of increasingly complex polymer structures and compositions. Some of the most interesting emerging techniques for polymer analysis are briefly reviewed in this paper. These include new developments in laser desorption ionization techniques, like solvent-free matrix-assisted laser desorption ionization (solvent-free MALDI) and surface-assisted laser desorption ionization (SALDI) mass spectrometry, and the developments in secondary ion mass spectrometry (SIMS), such as gentle-SIMS and cluster SIMS. Desorption electrospray ionization (DESI) mass spectrometry and direct analysis in real time (DART) mass spectrometry offer great possibilities for analysis of solid samples in their native form, while mobility separation prior to mass spectrometric analysis in ion mobility spectrometry (IMS) mass spectrometry further facilitates the analysis of complex polymer structures. The potential of these new developments is still largely unexplored, but they will surely further strengthen the position of mass spectrometry as an irreplaceable tool for polymer characterization.

  • 103.
    Aminlashgari, Nina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Surface Assisted Laser Desorption Ionization-Mass Spectrometry (SALDI-MS) for Analysis of Polyester Degradation Products2012In: Journal of the American Society for Mass Spectrometry, ISSN 1044-0305, E-ISSN 1879-1123, Vol. 23, no 6, p. 1071-1076Article in journal (Refereed)
    Abstract [en]

    Novel surface assisted laser desorption ionization-mass spectrometry (SALDI-MS) method was developed for rapid analysis of low molecular mass polyesters and their degradation products by laser desorption ionization-mass spectrometry. Three polycaprolactone materials were analyzed by the developed method before and after hydrolytic degradation. The signal-to-noise values obtained by SALDI-MS were 20-100 times higher compared with the ones obtained by using traditional MALDI-MS matrices. A clean background at low mass range and higher resolution was obtained by SALDI-MS. Different nanoparticle, cationizing agent, and solvent combinations were evaluated. Halloysite nanoclay and magnesium hydroxide showed the best potential as SALDI surfaces. The SALDI-MS spectrum of the polyester hydrolysis products was verified by ESI-MS. The developed SALDI-MS method possesses several advantages over existing methods for similar analyses.

  • 104.
    Aminlashgari, Nina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Pal, Jit
    Sanwaria, Sunita
    Nandan, Bhanu
    Srivastava, Rajiv K.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Degradation product profiles of melt spun in situ cross-linked poly(epsilon-caprolactone) fibers2015In: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 156, p. 82-88Article in journal (Refereed)
    Abstract [en]

    In situ cross-linking of poly(epsilon-caprolactone) (PCL) fiber with bis-(epsilon-caprolactone-4-yl) (BCY) was shown to be a feasible approach to compensate for reduction in molar mass of PCL during melt-spinning. The effect of in situ cross-linking on the degradation profile of melt spun PCL fibers with different amounts of BCY was evaluated using electrospray ionization-mass spectrometry. Degradation of the cross-linked fibers was carried out in aqueous medium at 37 degrees C and 60 degrees C for different periods of time. The degradation profiles were then compared with uncross-linked fiber and 3D porous cross-linked film of PCL Interesting differences in the degradation product profiles with linear, cyclic or BCY-related low molar mass compounds were observed, clearly demonstrating the effect of cross-linking and processing on the degradation process and formation of water-soluble products. In addition the degradation product profiles demonstrated that in situ cross-linking is a feasible technique for counteracting degradation reactions during melt-spinning.

  • 105.
    Aminlashgari, Nina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Shariatgorji, Mohammadreza
    Department of Analytical Chemistry, Stockholm University, Stockholm, Sweden.
    Ilag, Leopold L.
    Department of Analytical Chemistry, Stockholm University, Stockholm, Sweden.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Nanocomposites as novel surfaces for laser desorption ionization mass spectrometry2011In: Analytical Methods, ISSN 1759-9660, E-ISSN 1759-9679, Vol. 3, no 1, p. 192-197Article in journal (Refereed)
    Abstract [en]

    The possibility to utilize nanocomposite films as easy-to-handle surfaces for surface assisted laser desorption ionization-mass spectrometry (SALDI-MS) of small molecules, such as pharmaceutical compounds, was evaluated. The signal-to-noise values of acebutolol, propranolol and carbamazepine obtained on the nanocomposite surfaces were higher than the values obtained on plain PLA surface showing that the nanoparticles participate in the ionization/desorption process even when they are immobilized in the polymer matrix. The advantages of nanocomposite films compared to the free nanoparticles used in earlier studies are the ease of handling and reduction of instrument contamination since the particles are immobilized into the polymer matrix. Eight inorganic nanoparticles, titanium dioxide, silicon dioxide, magnesium oxide, hydroxyapatite, montmorillonite nanoclay, halloysite nanoclay, silicon nitride and graphitized carbon black at different concentrations were solution casted to films with polylactide (PLA). There were large differences in signal intensities depending on the type of drug, type of nanoparticle and the concentration of nanoparticles. Polylactide with 10% titanium oxide or 10% silicon nitride functioned best as SALDI-MS surfaces. The limit of detection (LOD) for the study was ranging from 1.7 ppm up to 56.3 ppm and the signal to noise relative standard deviations for the surface containing 10% silicon nitride was approximately 20-30%. Scanning electron microscopy demonstrated in most cases a good distribution of the nanoparticles in the polymer matrix and contact angle measurements showed increasing hydrophobicity when the nanoparticle concentration was increased, which could influence the desorption and ionization. Overall, the results show that nanocomposite films have potential as surfaces for SALDI-MS analysis of small molecules.

  • 106.
    Aminzadeh, Selda
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Lauberts, M.
    Dobele, G.
    Ponomarenko, J.
    Mattsson, T.
    Lindström, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Sevastyanova, Olena
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Membrane filtration of kraft lignin: Structural charactristics and antioxidant activity of the low-molecular-weight fraction2018In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 112, p. 200-209Article in journal (Refereed)
    Abstract [en]

    Lignin, which is the second most abundant biomass component and has carbon-rich phenolic content, is a promising renewable raw material for multiple applications, such as carbon fibers, adhesives, and emulsifiers. To use lignin efficiently, it is important to ensure its purity and homogeneity. As a result, the separation of lignin into fractions with high purity and narrow molecular-weight distributions is likely a prerequisite for several applications. Ultrafiltration using ceramic membranes has many advantages, including enabling direct lignin extraction from Kraft pulp cooking liquors without pH and temperature adjustment. One challenge with membrane filtration using such a system is the potential for reduced membrane performance over time, which is associated with fouling. In this study, LignoBoost Kraft lignin was fractionated using a ceramic membrane with a molecular weight cut-off of 1 kDa. The separation behavior during ultrafiltration fractionation was investigated and the antioxidant properties of the recovered low-molecular-weight (low-MW) lignin samples were evaluated. Using this model system, the permeate fluxes were unstable during the 100 h of membrane operation. However, a decrease in the average MW in the permeate over time was observed. The shift in MW was most pronounced for virgin membranes, while a more stable MW distribution was evident for membranes subjected to multiple cleaning cycles. According to 2D NMR analysis, low-MW lignin that was recovered after 100 h of operation, consisted of smaller lignin fragments, such as dimers and oligomers, with a high content of methoxy-groups. This was confirmed using the size exclusion chromatography method, which indicated an weigh average molecular weight in the range of 450–500 Da. 31P NMR spectroscopy showed that, despite the lower total content of phenolic OH groups, the low-MW sample had a higher proportion of non-condensed phenolic OH groups. The results of the antioxidant tests demonstrated the strong potential of lignin and its low-MW fraction as a natural antioxidant, particularly for lipid-containing systems. The low-MW lignin fraction showed better antioxidant activity than the non-fractionated LignoBoost lignin in the kinetic oxygen radical absorbance capacity (ORAC) test and demonstrated three-fold stronger inhibition of the substrate (fluorescein) than the reference antioxidant Trolox (a water-soluble derivative of vitamin E).

  • 107.
    Anantha, Krishnan Hariramabadran
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Örnek, Cem
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Ejnermark, S.
    Medvedeva, A.
    Sjöström, J.
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    In situ AFM study of localized corrosion processes of tempered AISI 420 martensitic stainless steel: Effect of secondary hardening2017In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 164, no 13, p. C810-C818Article in journal (Refereed)
    Abstract [en]

    The effect of secondary hardening of tempered AISI 420 martensitic stainless steel on the corrosion behavior in aqueous 0.01 M NaCl has been studied, in-situ, using atomic force microscopy (AFM) to monitor real-time localized corrosion processes. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy, and X-ray diffraction analyses confirmed the presence of undissolved and secondary carbides (Cr23C6, Cr7C3, Cr3C2, Cr3C, Cr2C, and CrC) as well as retained austenite, all finely dispersed in the tempered martensitic matrix. Electrochemical measurements, consisted of monitoring of the open-circuit potential vs. time and cyclic polarization in 0.01 M NaCl solution, were performed to evaluate the passivity and its breakdown, and it was seen that initiation sites for localized corrosion were predominantly peripheral sites of carbides. In-situ AFM measurements revealed that there was a sequence for localized corrosion in which the neighboring matrix next to secondary carbides dissolved first, followed by corrosive attack on regions adjacent to undissolved carbides. Tempering at 500◦C reduced the corrosion resistance and the ability to passivate in comparison to tempering at 250◦C.

  • 108.
    Anantha, Krishnan Hariramabadran
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Örnek, Cem
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Ejnermark, Sebastian
    Uddeholms AB, Res & Dev, SE-68385 Hagfors, Sweden..
    Thuvander, Anders
    Uddeholms AB, Res & Dev, SE-68385 Hagfors, Sweden..
    Medvedeva, Anna
    Uddeholms AB, Res & Dev, SE-68385 Hagfors, Sweden..
    Sjostrom, Johnny
    Uddeholms AB, Res & Dev, SE-68385 Hagfors, Sweden..
    Pan, Jinshan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Experimental and modelling study of the effect of tempering on the susceptibility to environment-assisted cracking of AISI 420 martensitic stainless steel2019In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 148, p. 83-93Article in journal (Refereed)
    Abstract [en]

    The resistance to environment-assisted cracking (EAC) of AISI 420 martensitic stainless steel (MSS) was investigated in 0.3 M NaCl solution (room temperature) at constant loads for 30 days. The steel tempered at 250 degrees C was superior to the 500 degrees C-temper, which showed corrosion pits favouring cracking. The fracture surface showed faceted grains, cleavage, striations, and inter- and transgranular cracks, suggesting a mixed stress corrosion cracking (SCC) and hydrogen embrittlement (HE) mechanism as the cause for EAC. Finite element modelling (FEM) indicated strain/stress localization at the mouth of deep pits and at the wall of shallow pits, displaying the favoured locations for pit-to-crack transition.

  • 109.
    Andersson, Anna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Characterisation of the influence of curing temperature on the properties of 2K waterborne topcoat2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Replacing solventborne coating with waterborne can reduce emission of VOC from paint shops, and decrease the amount of CO2 released from after-burners. The chemistry of 2K WB urethane coatings includes complex kinetics, with a selectivity which is highly dependent on application and curing conditions. To be able to design a coating process producing stable high quality coatings, it is important to know what factors affect the material properties. In this project, the effect of variations in temperature during curing of 2K WB and 2K SB topcoats have been evaluated in order to determine if there are any measurable effects on the material. The significance of these difference have also been evaluated to substantiate the need for thorough design of the curing process.

    After evaluation of visual, mechanical and chemical properties, as well as the durability of the cured topcoats, it was found that the effect of curing temperature on the level of gloss on 2K WB topcoats could be seen with the naked eye. Effects on colour, hardness, flexibility, adhesion and durability could also be measured, and revealed apparent changes in the material. Increased curing temperature had effects on both cross-linking density and isocyanate conversion. The heightened temperature contributed to the formation of topcoats with significantly decreased level of gloss and reduced stone-chip resistance, but also increased hardness and chemical resistance to an extent that was deemed significant. Varied curing temperature was found to give variations in durability, which with time may give different ageing properties of parts coated under different conditions. Before implementation of this type of waterborne topcoat, it is recommended that several properties be further evaluated, such as the effect of humidity and wet paint viscosity on the material properties.

  • 110.
    Andersson, Joakim
    KTH, School of Chemical Science and Engineering (CHE).
    Lifetime estimation of lithium-ion batteries for stationary energy storage system2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the continuing transition to renewable inherently intermittent energy sources like solar- and wind power, electrical energy storage will become progressively more important to manage energy production and demand. A key technology in this area is Li-ion batteries. To operate these batteries efficiently, there is a need for monitoring of the current battery state, including parameters such as state of charge and state of health, to ensure that adequate safety and performance is maintained. Furthermore, such monitoring is a step towards the possibility of the optimization of battery usage such as to maximize battery lifetime and/or return on investment. Unfortunately, possible online measurements during actual operation of a lithium-ion battery are typically limited to current, voltage and possibly temperature, meaning that direct measurement of battery status is not feasible. To overcome this, battery modeling and various regression methods may be used. Several of the most common regression algorithms suggested for estimation of battery state of charge and state of health are based on Kalman filtering. While these methods have shown great promise, there currently exist no thorough analysis of the impact of so-called filter tuning on the effectiveness of these algorithms in Li-ion battery monitoring applications, particularly for state of health estimation. In addition, the effects of only adjusting the cell capacity model parameter for aging effects, a relatively common approach in the literature, on overall state of health estimation accuracy is also in need of investigation.

    In this work, two different Kalman filtering methods intended for state of charge estimation: the extended Kalman filter and the extended adaptive Kalman filter, as well as three intended for state of health estimation: the dual extended Kalman filer, the enhanced state vector extended Kalman filer, and the single weight dual extended Kalman filer, are compared from accuracy, performance, filter tuning and practical usability standpoints. All algorithms were used with the same simple one resistor-capacitor equivalent circuit battery model. The Li-ion battery data used for battery model development and simulations of filtering algorithm performance was the “Randomized Battery Usage Data Set” obtained from the NASA Prognostics Center of Excellence. 

    It is found that both state of charge estimators perform similarly in terms of accuracy of state of charge estimation with regards to reference values, easily outperforming the common Coulomb counting approach in terms of precision, robustness and flexibility. The adaptive filter, while computationally more demanding, required less tuning of filter parameters relative to the extended Kalman filter to achieve comparable performance and might therefore be advantageous from a robustness and usability perspective. Amongst the state of health estimators, the enhanced state vector approach was found to be most robust to initialization and was also least taxing computationally. The single weight filter could be made to achieve comparable results with careful, if time consuming, filter tuning. The full dual extended Kalman filter has the advantage of estimating not only the cell capacity but also the internal resistance parameters. This comes at the price of slow performance and time consuming filter tuning, involving 17 parameters. It is however shown that long-term state of health estimation is superior using this approach, likely due to the online adjustment of internal resistance parameters. This allows the dual extended Kalman filter to accurately estimate the SoH over a full test representing more than a full conventional battery lifetime. The viability of only adjusting the capacity in online monitoring approaches therefore appears questionable. Overall the importance of filter tuning is found to be substantial, especially for cases of very uncertain starting battery states and characteristics.

  • 111.
    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.

  • 112.
    Andersson, Linn
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Enskilda brunnars vattenkvalitet samt förekommande vattenreningstekniker2018Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
  • 113.
    Andersson, Rasmus
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Evaluation of two hydrocyclone designs for pulp fractionation2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The process conditions and fractionation efficiency of two hydrocyclone designs, a novel and a conventional conical design, were evaluated. The novel design comprised a modified inlet section, where the pulp suspension had to pass a narrow ring-shaped opening, and a very compact fractionation zone. The influence of feed concentration and fine fraction mass ratio was studied. The trials were performed with never-dried, unrefined bleached chemical softwood pulp. Fractionation efficiency was evaluated in terms of change of surface roughness of handsheets made out of the fractions and the feed pulp respectively.

    The fractionation efficiency increased considerably with decreasing fine fraction mass ratio, especially at higher feed concentrations. This finding prompted a hypothesis on the existence of a radial gradient in the composition of the suspension inside the novel hydrocyclone. Using the novel hydrocyclone in a feed-forward fractionation system would therefore prove to be more favourable as a larger total fine fraction of better properties can be obtained. A three-stage feed-forward fractionation system was evaluated in laboratory scale. Here, it was indeed possible to extract fine fractions with improved surface properties in each of the three consecutive stages. All three fine fractions had about the same surface roughness.

    The fractionation performance of the novel design was benchmarked against that of a conventional, best available technology (BAT) design. In terms of fractionation efficiency, the BAT design performed better. However, the fractions produced with the novel hydrocyclone had a much smaller difference in concentration, implying a much less pronounced enrichment of fines in the fine fraction. It is unclear, to what extent the lower share of latewood fibres and the increased fines content, respectively, contributed to the improved surface roughness of the fine fractions. However, it is clear that the lower enrichment of fines in the novel hydrocyclone makes it easier to install it in industrial applications without a need for auxiliary equipment to redistribute large water flows.

     

  • 114.
    Andersson, Richard L.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Mallon, Peter E.
    Salajkova, Michaela
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Micromechanics of toughness improved electrospun PMMA fibers with embedded cellulose as tested under in-situ microscopyManuscript (preprint) (Other academic)
  • 115.
    Andersson, Richard L.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Salajkova, Michaela
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Mallon, P. E.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Micromechanical Tensile Testing of Cellulose-Reinforced Electrospun Fibers Using a Template Transfer Method (TTM)2012In: Journal of polymers and the environment, ISSN 1064-7546, E-ISSN 1572-8900, Vol. 20, no 4, p. 967-975Article in journal (Refereed)
    Abstract [en]

    A template transfer method (TTM) and a fiber fixation technique were established for fiber handling and micro tensile stage mounting of aligned and non-aligned electrospun fiber mats. The custom-made template had been precut to be mounted on a variety of collectors, including a rapidly rotating collector used to align the fibers. The method eliminated need for direct physical interaction with the fiber mats before or during the tensile testing since the fiber mats were never directly clamped or removed from the original substrate. By using the TTM it was possible to measure the tensile properties of aligned poly(methyl methacrylate) (PMMA) fiber mats, which showed a 250 % increase in strength and 450 % increase in modulus as compared to a non-aligned system. The method was further evaluated for aligned PMMA fibers reinforced with cellulose (4 wt%) prepared as enzymatically derived nanofibrillated cellulose (NFC). These fibers showed an additional increase of 30 % in both tensile strength and modulus, resulting in a toughness increase of 25 %. The fracture interfaces of the PMMA-NFC fibers showed a low amount of NFC pull-outs, indicating favorable phase compatibility. The presented fiber handling technique is universal and may be applied where conservative estimates of mechanical properties need to be assessed for very thin fibers.

  • 116.
    Andersson, Richard L.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Micromechanical, Antimicrobial and Filtration Properties of Electrospun Fiber Mats2014Doctoral thesis, comprehensive summary (Other academic)
  • 117.
    Andersson, Robert
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Catalytic conversion of syngas to higher alcohols over MoS2-based catalysts2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The present thesis concerns catalytic conversion of syngas (H2+ CO) into a blend of methanol and higher alcohols, an attractive way of producing fuels and chemicals. This route has the potential to reduce the oil dependence in the transport sector and, with the use of biomass for the syngas generation, produce CO2-neutral fuels.

    Alkali promoted MoS2-based catalysts show a high selectivity to higher alcohols, while at the same time being coke resistant, sulfur tolerant and displaying high water-gas shift activity. This makes this type of catalyst especially suitable for being used with syngas derived from biomass or coal which typically has a low H2/CO-ratio.

    This thesis discusses various important aspects of higher alcohol synthesis using MoS2-based catalysts and is a summary of four scientific papers. The first part of the thesis gives an introduction to how syngas can be produced and converted into different fuels and chemicals. It is followed by an overview of higher alcohol synthesis and a description of MoS2-based catalysts. The topic alcohol for use in internal combustion engines ends the first part of the thesis.

    In the second part, the experimental part, the preparation of the MoS2-based catalysts and the characterization of them are handled. After describing the high-pressure alcohol reactor setup, the development of an on-line gas chromatographic system for higher alcohol synthesis with MoS2 catalysts is covered (Paper I). This method makes activity and selectivity studies of higher alcohol synthesis catalysts more accurate and detailed but also faster and easier. Virtually all products are very well separated and the established carbon material balance over the reactor closed well under all tested conditions. The method of trace level sulfur analysis is additionally described.

    Then the effect of operating conditions, space velocity and temperature on product distribution is highlighted (Paper II). It is shown that product selectivity is closely correlated with the CO conversion level and why it is difficult to combine both a high single pass conversion and high alcohol selectivity over this catalyst type. Correlations between formed products and formation pathways are additionally described and discussed. The CO2 pressure in the reactor increases as the CO conversion increases, however, CO2 influence on formation rates and product distribution is to a great extent unclear. By using a CO2-containing syngas feed the effect of CO2 was studied (Paper III).

    An often emphasized asset of MoS2-based catalysts is their sulfur tolerance. However, the use of sulfur-containing feed and/or catalyst potentially can lead to incorporation of unwanted organic sulfur compounds in the product. The last topic in this thesis covers the sulfur compounds produced and how their quantity is changed when the feed syngas contains H2S (Paper IV). The effect on catalyst activity and selectivity in the presence of H2S in the feed is also covered.

  • 118.
    Andersson, Robert
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Correlation patterns and effect of syngas conversion level for product selectivity to alcohols and hydrocarbons over molybdenum sulfide based catalysts2012In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 417, p. 119-128Article in journal (Refereed)
    Abstract [en]

    The focus of the present study was to investigate the effect of the operation conditions, space velocity and temperature, on product distribution for a K-Ni-MoS2 catalyst for mixed alcohol synthesis from syngas. All experiments were performed at 91 bar pressure and constant H-2/CO=1 syngas feed ratio. For comparison, results from a non-promoted MoS2 catalyst are presented. It was found that the CO conversion level for the K-Ni-MoS2 catalyst very much decides the alcohol and hydrocarbon selectivities. Increased CO conversion by means of increased temperature (tested between 330 and 370 degrees C) or decreased space velocity (tested between 2400 and 18,000 ml/(g(cat) h)), both have the same effect on the product distribution with decreased alcohol selectivity and increased hydrocarbon selectivity. Increased CO conversion also leads to a greater long-to-short alcohol chain ratio. This indicates that shorter alcohols are building blocks for longer alcohols and that those alcohols can be converted to hydrocarbons by secondary reactions. At high temperature (370 degrees C) and low space velocity (2400 ml/(g(cat) h)) the selectivity to isobutanol is much greater than previously reported (9%C). The promoted catalyst (K-Ni-MoS2) is also compared to a non-promoted (MoS2) catalyst: the promoted catalyst has quite high alcohol selectivity, while almost only hydrocarbons are produced with the non-promoted catalyst. Another essential difference between the two catalysts is that the paraffin to olefin ratio within the hydrocarbon group is significantly different. For the non-promoted catalyst virtually no olefins are produced, only paraffins, while the promoted catalyst produces approximately equal amounts of C-2-C-6 olefins and paraffins. Indications of olefins being produced by dehydration of alcohols were found. The selectivity to other non-alcohol oxygenates (mostly short esters and aldehydes) is between 5 and 10%C and varies little with space velocity but decreases slightly with increased temperature. Very strong correlation patterns (identical chain growth probability) and identical deviations under certain reaction conditions between aldehyde and alcohol selectivities (for the same carbon chain length) indicate that they derive from the same intermediate. Also olefin selectivity is correlated to alcohol selectivity, but the correlation is not as strong as between aldehydes and alcohols. The selectivity to an ester is correlated to the selectivity to the two corresponding alcohols, in the same way as an ester can be thought of as built from two alcohol chains put together (with some H-2 removed). This means that, e.g. methyl acetate selectivity (C-3) is correlated to the combination of methanol (C-1) and ethanol (C-2) selectivities.

  • 119.
    Andrae, Johan
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Numerical Studies of Wall Effects of Laminar Flames2001Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Numerical simulations have been done with the CHEMKINsoftware to study different aspects of wall effects in thecombustion of lean, laminar and premixed flames in anaxisymmetric boundary-layer flow.

    The importance of the chemical wall effects compared to thethermal wall effects caused by the development of the thermaland velocity boundary layer has been investigated in thereaction zone by using different wall boundary conditions, walltemperatures and fuel/air ratios. Surface mechanisms include acatalytic surface (Platinum), a surface that promotesrecombination of active intermediates and a completely inertwall with no species and reactions as the simplest possibleboundary condition.

    When hydrogen is the model fuel, the analysis of the resultsshow that for atmospheric pressure and a wall temperature of600 K, the surface chemistry gives significant wall effects atthe richer combustion case (f=0.5), while the thermal andvelocity boundary layer gives rather small effects. For theleaner combustion case (f=0.1) the thermal and velocityboundary layer gives more significant wall effects, whilesurface chemistry gives less significant wall effects comparedto the other case.

    For methane as model fuel, the thermal and velocity boundarylayer gives significant wall effects at the lower walltemperature (600 K), while surface chemistry gives rather smalleffects. The wall can then be modelled as chemically inert forthe lean mixtures used (f=0.2 and 0.4). For the higher walltemperature (1200 K) the surface chemistry gives significantwall effects.

    For both model fuels, the catalytic wall unexpectedlyretards homogeneous combustion of the fuel more than the wallthat acts like a sink for active intermediates. This is due toproduct inhibition by catalytic combustion. For hydrogen thisoccurs at atmospheric pressure, but for methane only at thehigher wall temperature (1200 K) and the higher pressure (10atm).

    As expected, the overall wall effects (i.e. a lowerconversion) were more pronounced for the leaner fuel-air ratiosand at the lower wall temperatures.

    To estimate a possible discrepancy in flame position as aresult of neglecting the axial diffusion in the boundary layerassumption, calculations have been performed with PREMIX, alsoa part of the CHEMKIN software. With PREMIX, where axialdiffusion is considered, steady, laminar, one-dimensionalpremixed flames can be modelled. Results obtained with the sameinitial conditions as in the boundary layer calculations showthat for the richer mixtures at atmospheric pressure the axialdiffusion generally has a strong impact on the flame position,but in the other cases the axial diffusion may beneglected.

    Keywords:wall effects, laminar premixed flames,platinum surfaces, boundary layer flow

  • 120.
    Andrae, Johan
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Björnbom, Pehr
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Wall Effects of Laminar Hydrogen Flames over Platinum and Inert Surfaces2000In: AIChE Journal, ISSN 0001-1541, E-ISSN 1547-5905, Vol. 46, no 7, p. 1454-1460Article in journal (Refereed)
    Abstract [en]

    Different aspects of wall effects in the combustion of lean, laminar and stationary hydrogen flames in an axisymmetric boundary-layer flow were studied using numerical simulations with the program CRESLAF. The importance of the chemical wall effects compared to thermal wall effects caused by heat transfer to a cold wall was investigated in the reaction zone by using different combustion systems at atmospheric pressure. Surface mechanisms include a catalytic surface, an inert surface that promotes radical recombinations, and a completely inert wall used as reference was the simplest possible boundary condition. The analysis of the results show that for the richer combustion case ( = 0.5) the surface chemistry gives significant wall effects, while the thermal and velocity boundary layer gives rather small effects. But for the leaner combustion case ( = 0.1) the thermal and velocity boundary layer gives more significant wall effects, while surface chemistry gives less significant wall effects compared to the other case. As expected, the overall wall effects were more pronounced for the leaner combustion case.

  • 121.
    Andrae, Johan
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Björnbom, Pehr
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Edsberg, Lennart
    KTH, Superseded Departments, Numerical Analysis and Computer Science, NADA.
    Numerical studies of wall effects with laminar methane flames2002In: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 128, no 1-2, p. 165-180Article in journal (Refereed)
    Abstract [en]

    Wall effects in the combustion of lean methane mixtures have been studied numerically using the CHEMKIN software. To gain a deeper understanding of the flame-wall interaction in lean burn combustion, and in particular the kinetic and thermal effects, we have simulated lean and steady methane/air flames in a boundary layer flow. The gas-phase chemistry is modeled with the GRI mechanism version 1.2. Boundary conditions include an inert wall, a recombination wall and catalytic combustion of methane. Different pressures, wall temperatures and fuel-air ratios are used to address questions such as which part of the wall effects is most important at a given set of conditions. As the results are analyzed it can be seen that the thermal wall effects are more significant at the lower wall temperature (600 K) and the wall can essentially be modeled as chemical inert for the lean mixtures used. At the higher wall temperature (1,200 K), the chemical wall effects become more significant and at the higher pressure (10 atm) the catalytic surface retards homogeneous combustion of methane more than the recombination wall because of product inhibition. This may explain the increased emissions of unburned fuel observed in engine studies, when using catalytic coatings on the cylinder walls. The overall wall effects were more pronounced for the leaner combustion case (phi = 0.2). When the position of the reaction zone obtained from the boundary layer calculations is compared with the results from a one-dimensional premixed flame model, there is a small but significant difference except at the richer combustion case (phi = 0.4) at atmospheric pressure, where the boundary layer model may not predict the flame position for the given initial conditions.

  • 122.
    Andrae, Johan C. G.
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Johansson, A.
    Björnbom, Pehr
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Rosen, A.
    OH desorption energies for a palladium catalyst characterised by kinetic modelling and laser-induced fluorescence2004In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 563, no 03-jan, p. 145-158Article in journal (Refereed)
    Abstract [en]

    A kinetic model for the H-2/O-2 reaction on a polycrystalline palladium catalyst has been constructed using CHEMKIN in order to understand the coverage-dependent OH desorption energy. Each adsorbed oxygen atom was modelled to cover four I'd surface sites. The yield of OH and the water production were measured with laser-induced fluorescence (LIF) and microcalorimetry respectively as a function of the relative hydrogen concentration, alpha(H2). The temperature of the catalyst was 1300 K, the total pressure was 13 Pa and the flow was set to 100 SCCM. In fitting the model to the experimental data, the OH desorption energy E-OH(d) was found to have a first-order coverage dependence according to: E-OH(d)(theta) = E-OH(d)(0) - Btheta, where B is a constant set to 92 kJ/mol. The desorption energy at zero coverage E-OH(d)(0) was determined to be 226 kJ/mol. The model could also qualitatively and quantitatively reproduce the apparent desorption energy as a function of alpha(H2); therefore it is believed that the coverage could be predicted by the model. The values for E-OH(d)(theta) were calculated as a function of alpha(H2). From the results of a sensitivity analysis and rate of production calculations' there are strong reasons to believe that the main water-forming reaction on Pd at 1300 K is the hydrogen addition reaction, H + OH reversible arrow H2O. Enthalpy diagrams for the water-forming reactions are also presented.

  • 123.
    Andrae, Johan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Reaction Engineering.
    Johansson, David
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Reaction Engineering.
    Björnbom, Pehr
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Reaction Engineering.
    Risberg, Per
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Kalghatgi, Gautam
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Cooxidation in the auto-ignition of primary reference fuels and n-heptane/toluene blends2005In: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 140, no 4, p. 267-286Article in journal (Refereed)
    Abstract [en]

    Auto-ignition of fuel mixtures was investigated both theoretically and experimentally to gain further understanding of the fuel chemistry. A homogeneous charge compression ignition (HCCI) engine was run under different operating conditions with fuels of different RON and MON and different chemistries. Fuels considered were primary reference fuels and toluene/n-heptane blends. The experiments were modeled with a single-zone adiabatic model together with detailed chemical kinetic models. In the model validation, co-oxidation reactions between the individual fuel components were found to be important in order to predict HCCI experiments, shock-tube ignition delay time data, and ignition delay times in rapid compression machines. The kinetic models with added co-oxidation reactions further predicted that an n-heptane/toluene fuel with the same RON as the corresponding primary reference fuel had higher resistance to auto-ignition in HCCI combustion for lower intake temperatures and higher intake pressures. However, for higher intake temperatures and lower intake pressures the n-heptane/toluene fuel and the PRF fuel had similar combustion phasing.

  • 124.
    Andrae, Johan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Johansson, David
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Bursell, Martin
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Fakhrai, Reza
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Jayasuriya, Jeevan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Manrique Carrera, Arturo
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    High-pressure catalytic combustion of gasified biomass in a hybrid combustor2005In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 293, no 1-2, p. 129-136Article in journal (Refereed)
    Abstract [en]

    Catalytic combustion of synthetic gasified biomass was conducted in a high-pressure facility at pressures ranging from 5 to 16 bars. The catalytic combustor design considered was a hybrid monolith (400 cpsi, diameter 3.5 cm, length 3.6 cm and every other channel coated). The active phase consisted of 1 wt.% Pt/gamma-Al2O3 With wash coat loading of total monolith 15 wt.%. In the interpretation of the experiments, a twodimensional boundary layer model was applied successfully to model a single channel of the monolith. At constant inlet velocity to the monolith the combustion efficiency decreased with increasing pressure. A multi-step surface mechanism predicted that the flux of carbon dioxide and water from the surface increased with pressure. However, as the pressure (i.e. the Reynolds number) was increased, unreacted gas near the center of the channel penetrated significantly longer into the channel compared to lower pressures. For the conditions studied (lambda = 46, T-in = 218-257 degrees C and residence time similar to 5 ms), conversion of hydrogen and carbon monoxide were diffusion limited after ignition, while methane never ignited and was kinetically controlled. According to the kinetic model surface coverage of major species changed from CO, H and CO2 before ignition to O, OH, CO2 and free surface sites after ignition. The model predicted further that for constant mass flow combustion efficiency increased with pressure, and was more pronounced at lower pressures (2.5-10 bar) than at higher pressures (> 10 bar).

  • 125.
    André, Magnus
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    New Methods for the Determination of Sorption Capacities and Sorption-Related Properties of Intact Rock2009Doctoral thesis, comprehensive summary (Other academic)
  • 126.
    André, Magnus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Malmström, Maria
    KTH, School of Industrial Engineering and Management (ITM), Industrial Ecology.
    Neretnieks, Ivar
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Determination of sorption properties of intact rock samples: New methods based on electromigration2009In: Journal of Contaminant Hydrology, ISSN 0169-7722, E-ISSN 1873-6009, Vol. 103, no 3-4, p. 71-81Article in journal (Refereed)
    Abstract [en]

    Two new methods for determining sorption coefficients in large rock samples have been developed. The methods use electromigration as a means to speed up the transport process, allowing for fast equilibration between rock sample and tracer solution. An electrical potential gradient acts as a driving force for transport in addition to the concentration gradient and forces the cations through the rock sample towards the cathode. The electrical potential gradient induces both electromigration and electroosmotic flow with a resulting solute transport that is large compared to diffusive fluxes. In one of the methods, the solute is driven through the sample and collected at the cutlet side. In the other, simpler method, the rock sample is equilibrated by circulating the solute through the sample. The equilibration of rock samples, up to 5 cm in length, with an aqueous solution has been accomplished within days to months. Experiments using cesium as a sorbing tracer yield results consistent with considerably more time demanding in-diffusion experiments. These methods give lower distribution coefficients than those obtained using traditional batch experiments with crushed rock. (C) 2008 Elsevier B.V. All rights reserved.

  • 127.
    André, Magnus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Malmström, Maria
    KTH, School of Industrial Engineering and Management (ITM), Industrial Ecology.
    Neretnieks, Ivar
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Rapid surface area determination of crystalline rock using impedance spectroscopyManuscript (preprint) (Other academic)
  • 128.
    André, Magnus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Malmström, Maria
    KTH, School of Industrial Engineering and Management (ITM), Industrial Ecology.
    Neretnieks, Ivar
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Specific surface area determinations on intact drillcores and evaluation of extrapolation methods for rock matrix surfaces2009In: Journal of Contaminant Hydrology, ISSN 0169-7722, E-ISSN 1873-6009, Vol. 110, no 1-2, p. 1-8Article in journal (Refereed)
    Abstract [en]

    Permanent storage of spent nuclear fuel in crystalline bedrock is investigated in several countries. For this storage scenario, the host rock is the third and final barrier for radionuclide migration. Sorption reactions in the crystalline rock matrix have strong retardative effects on the transport of radionuclides. To assess the barrier properties of the host rock it is important to have sorption data representative of the undisturbed host rock conditions. Sorption data is in the majority of reported cases determined using crushed rock. Crushing has been shown to increase a rock samples sorption capacity by creating additional surfaces. There are several problems with such an extrapolation. In studies where this problem is addressed, simple models relating the specific surface area to the particle size are used to extrapolate experimental data to a value representative of the host rock conditions. In this article, we report and compare surface area data of five size fractions of crushed granite and of 100 mm long drillcores as determined by the Brunauer Emmet Teller (BET)-method using N-2-gas. Special sample holders that could hold large specimen were developed for the BET measurements. Surface area data on rock samples as large as the drillcore has not previously been published. An analysis of this data show that the extrapolated value for intact rock obtained from measurements on crushed material was larger than the determined specific surface area of the drillcores, in some cases with more than 1000%. Our results show that the use of data from crushed material and current models to extrapolate specific surface areas for host rock conditions can lead to over estimation interpretations of sorption ability. The shortcomings of the extrapolation model are discussed and possible explanations for the deviation from experimental data are proposed.

  • 129.
    Ankerfors, Caroline
    et al.
    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. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    AFM adhesion imaging for the comparison of polyelectrolyte complexes and polyelectrolyte multilayers2012In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 8, no 32, p. 8298-8301Article in journal (Refereed)
    Abstract [en]

    The adhesion and topography of dry surfaces treated with polyelectrolyte complexes (PECs) and multilayers (PEMs) of PAH/PAA or CPAM/silica nanoparticles were studied using AFM adhesion mapping. PEMs gave higher adhesion than did PECs for the PAH/PAA system, but adhesion did not differ significantly between PEMs and PECs for the CPAM/silica system. The latter system displayed multiple release patterns, interpreted as disentanglements and tentatively ascribed to nanoparticle presence. AFM adhesion mapping is valuable for analysing PEC and PEM. The measurements should, however, be combined with separate force measurements for a more complete picture of the adhesion.

  • 130. Ankerfors, Caroline
    et al.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Polyelectrolyte Complexes for Tailoring of Wood Fibre Surfaces2014In: Polyelectrolyte Complexes In The Dispersed And Solid State II: Application Aspects, Springer Berlin/Heidelberg, 2014, p. 1-24Chapter in book (Refereed)
    Abstract [en]

    The use of polyelectrolyte complexes (PECs) provides new opportunities for surface engineering of solid particles in aqueous environments to functionalize the solids either for use in interactive products or to tailor their adhesive interactions in the dry and/or wet state. This chapter describes the use of PECs in paper-making applications where the PECs are used for tailoring the surfaces of wood-based fibres. Initially a detailed description of the adsorption process is given, in more general terms, and in this respect both in situ formed and pre-formed complexes are considered. When using in situ formed complexes, which were intentionally formed by the addition of oppositely charged polymers, it was established that the order of addition of the two polyelectrolytes was important, and by adding the polycation first a more extensive fibre flocculation was found. PECs can also form in situ by the interaction between polyelectrolytes added and polyelectrolytes already present in the fibre suspension originating from the wood material, e. g. lignosulphonates or hemicelluloses. In this respect the complexation can be detrimental for process efficiency and/or product quality depending on the charge balance between the components, and when using the PECs for fibre engineering it is not recommended to rely on in situ PEC formation. Instead the PECs should be pre-formed before addition to the fibres. The use of pre-formed PECs in the paper-making process is described as three sub-processes: PEC formation, adsorption onto surfaces, and the effect on the adhesion between surfaces. The addition of PECs, and adsorption to the fibres, prior to formation of the paper network structure has shown to result in a significant increase in joint strength between the fibres and to an increased strength of the paper made from the fibres. The increased joint strength between the fibres is due to both an increased molecular contact area between the fibres and an increased molecular adhesion. The increased paper strength is also a result of an increased number of fibre/fibre contacts/unit volume of the paper network.

  • 131.
    Ansari, Farhan
    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.
    Salajkova, Michaela
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Zhou, Qi
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Lars, Berglund
    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.
    Strong surface treatment effects on reinforcement efficiency in biocomposites based on cellulose nanocrystals in poly(vinyl acetate) matrix2015In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 16, no 12, p. 3916-3924Article in journal (Refereed)
    Abstract [en]

    In this work, the problem to disperse cellulose nanocrystals (CNC) in hydrophobic polymer matrices has been addressed through application of an environmentally friendly chemical modification approach inspired by clay chemistry. The objective is to compare the effects of unmodified CNC and modified CNC (modCNC) reinforcement, where degree of CNC dispersion is of interest. Hydrophobic functionalization made it possible to disperse wood-based modCNC in organic solvent and cast well-dispersed nanocomposite films of poly(vinyl acetate) (PVAc) with 1-20 wt % CNC. Composite films were studied by infrared spectroscopy (FT-IR), UV-vis spectroscopy, dynamic mechanical thermal analysis (DMTA), tensile testing, and field-emission scanning electron microscopy (FE-SEM). Strongly increased mechanical properties were observed for modCNC nanocomposites. The reinforcement efficiency was much lower in unmodified CNC composites, and specific mechanisms causing the differences are discussed.

  • 132.
    Ansari, Farhan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
    Skrifvars, M.
    Berglund, Lars
    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.
    Nanostructured biocomposites based on unsaturated polyester resin and a cellulose nanofiber network2015In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 117, p. 298-306Article in journal (Refereed)
    Abstract [en]

    Biocomposites reinforced by natural plant fibers tend to be brittle, moisture sensitive and have limited strength. Wood cellulose nanofibers (CNF) were therefore used to reinforce an unsaturated polyester matrix (UP) without the need of coupling agents or CNF surface modification. The nanostructured CNF network reinforcement strongly improves modulus and strength of UP but also ductility and toughness. A template-based prepreg processing approach of industrial potential is adopted, which combines high CNF content (up to 45 vol%) with nanoscale CNF dispersion. The CNF/UP composites are subjected to moisture sorption, dynamic thermal analysis, tensile tests at different humidities, fracture toughness tests and fractography. The glass transition temperature (T-g) increases substantially with CNF content. Modulus and strength of UP increase about 3 times at 45 vol% CNF whereas ductility and apparent fracture toughness are doubled. Tensile properties at high humidity are compared with other bio-composites and interpreted based on differences in molecular interactions at the interface.

  • 133. Antikhovich, I. V.
    et al.
    Kharitonov, Dima S.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. Belarusian State Technological University, Belarus.
    Chernik, A. A.
    Dobryden, Illia B.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Corrosion Resistance of Nickel Coatings Deposited from Low-Temperature Nickel-Plating Electrolytes2017In: Russian journal of applied chemistry, ISSN 1070-4272, E-ISSN 1608-3296, Vol. 90, no 4, p. 566-573Article in journal (Refereed)
    Abstract [en]

    The corrosion resistance of nickel coatings on a copper substrate, plated from low-temperature electrolytes based on acetates, tartrates, and isobutyrates, was studied by the methods of electrochemical impedance spectroscopy (EIS) and polarization curves. The tests were performed in a 0.3% NaCl solution. The nickel coatings exhibit high chemical activity, dissolving in the NaCl solution. The electrochemical step is the limiting step of the corrosion process.

  • 134.
    Antoni, Per
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hed, Yvonne
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Nordberg, Axel
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Nyström, Daniel
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Hult, Anders
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Malkoch, Michael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Bifunctional Dendrimers: From Robust Synthesis and Accelerated One-Pot Postfunctionalization Strategy to Potential Applications2009In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 48, no 12, p. 2126-2130Article in journal (Refereed)
  • 135.
    Antonsson, Stefan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Johansson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Lindström, Mikael E.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Low Mw-lignin fractions together with vegetable oils as available oligomers for novel paper-coating applications as hydrophobic barrier2008In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 27, no 1, p. 98-103Article in journal (Refereed)
    Abstract [en]

    Lignin residues are available in large amounts as kraft lignin from chemical pulping processes. This lignin is mainly incinerated in recovery boilers. The recovery boilers are often the bottle-necks in the overall pulping process when pulp production increases are desired. Through cross-flow nano-filtration of the black liquor from kraft pulping, a low-molecular weight lignin fraction can be removed thus decreasing the organic load on the recovery boilers. The low-molecular weight lignin fraction furthermore exhibit different characteristics compared to other commercial kraft lignins and represents a new raw material source in novel applications.

    The low-molecular weight lignin was used together with a vegetable oil to produce a new hydrophobic lignin derivative similar to suberin. The lignin and the lignin derivative was analysed with FT-IR, UV-vis and SEC. The ability of the product to make paper surfaces hydrophobic was also evaluated.

    The results demonstrate the possibility to make a suberin-like lignin derivative that is potentially of interest in paper-coating applications due to its capability to interact well with wood fibres and make paper hydrophobic.

  • 136. Arasteh, Rouhollah
    et al.
    Naderi, Ali
    Kaptan, Navid
    Maleknia, Laleh
    Akhlaghi, Shahin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Nazockdast, Hosein
    Effects of Fiber Spinning on the Morphology, Rheology, Thermal, and Mechanical Properties of Poly(trimethylene terephthalate)/Poly(ethylene terephthalate) Blends2014In: Advances in Polymer Technology, ISSN 0730-6679, E-ISSN 1098-2329, Vol. 33, no S1, p. 21443-Article in journal (Refereed)
    Abstract [en]

    The morphology, thermal behavior, rheological, and mechanical properties of poly(trimethylene terephthalate) (PTT)/poly(ethylene terephthalate) (PET) blend fibers were investigated. The scanning electron microscopy studies revealed the formation of a microfibrillar network of the PET within the PTT matrix after the fiber-spinning process. Differential scanning calorimetry results demonstrated that although the thermal characteristics of the amorphous phase were unaffected by the fiber-spinning process, the melting and crystallization behavior of the blends was altered by the elongation flow imposed during the melt spinning. The viscoelastic behavior of the PTT/PET blends was also studied by a steady shear rate and dynamic sweep rheological experiments before and after the spinning process. The induced morphology and crystallization reordering resulting from the fibrillation process are shown to have a remarkable effect on the complex viscosity profile of the PTT/PET fibers, particularly in the blend containing 30 wt% PET. The mechanical testing showed that tenacity and Young's modulus of the PTT fibers increased with the addition of PET up to 30 wt%.

  • 137.
    Arias, Veluska
    KTH, School of Chemical Science and Engineering (CHE).
    COPOLYMER MICELLES FOR TARGETED DRUG DELIVERY2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this study, two families of amphiphilic block copolymers were synthesized with different block length. The polymer copolymers are PVP-PCL and PEG-PCL. For each family three copolymers were made with variation in the length of the PCL block, thus the length ratios were label using the following composition: 1-2000-2000 g/mol, 2-2000-4000 g/mol and 3-2000-6000 g/mol. In the synthesis of PVP-PCL copolymers, PVP end-capped in ε-Caprolactone was synthesized by free radical polymerization; then the copolymer was synthesized by ring opening polymerization of ε-Caprolactone using BuLi as initiator. In the case of PEG-PCL copolymers, mPEG (Mn=2000 g/mol) was used as a co-monomer and the process was done by ring opening polymerization of ε-Caprolactone in the presence of Sn(Otc)2.The copolymers were characterized by SEC and the molecular structure confirmed using 1H-NMR. Knowing that amphiphilic block copolymers can form micelles at certain concentration, micellization study was performed by UV-vis spectroscopy. All the copolymers showed micelles formation in deionized water. The micellization process was also tested in buffer solutions with difference in pH, where only PVP-PCL copolymers showed micellar formation. The micelles formation was confirmed by SEM after lyophilization process. Also the size of the micelles was measure by Zetasizer, showing a range size between 100 nm and 500 nm. After studied the micelles features given by all the copolymers, one polymer of each family was chosen for drug loading and further study of release kinetics, based on the efficiency of the formulation. The copolymer chosen were the ones with the highest length of the hydrophobic block. The drug loading was done by direct dissolution method. Two types of drugs were used, SBA and Diflunisal. The drug loading content was 20 % w/w and 50 % w/w. Micelles from the PEG-PCL copolymer could achieve retention till 50 % w/w of drug loaded, whereas micelles from PVP-PCL copolymer only achieved retention of 20 % w/w of the drug. The micelles formation was again confirm by SEM and the micelles size was measure by Zetasizer. The size of the loaded micelles was smaller than the unloaded micelles. The delivery kinetics was study by UV-vis. After lyophilization process, the compound polymer-drug was immersed in PBS to perform the study, examining the delivery of both drugs in each copolymer selected. In the case of micelles from PVP-PCL copolymer, the large amount of drug was release after 9 h in PBS for both Pas. The micelles from PEG-PCL copolymer, showed a difference in release rate for both drugs, 9 h for Diflunisal and 3 h for SBA; the nature of the drug play a role in drug release and thus in drug loading efficiency. Finally, the families investigated seemed to be promising carriers for controlled drug release. In addition, they appeared to be promising formulations as injectable DDS.

  • 138.
    Arias, Veluska
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Höglund, Anders
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Polylactides with "green" plasticizers: Influence of isomer composition2013In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 130, no 4, p. 2962-2970Article in journal (Refereed)
    Abstract [en]

    Synthesized polylactides (PLA) with different D-isomer contents in the polymer chain were melt-blended with a series of green plasticizers by extrusion. Mechanical and thermal properties as well as the morphology of the plasticized materials were characterized to demonstrate how the combination of PLA with different D-contents and plasticizer controls the material properties. After addition of acetyl tributyl citrate (ATC), the elongation at break for PLA with a low D-isomer content was twice as high as that for PLAs with high D-isomer contents. Similar variations in the plasticization effect on the PLAs were also observed with the other plasticizers used, glyceryl triacetate (GTA), glycerol trihexanoate (GTH) and polyethylene glycol (PEG). In order to continue with the development of renewable polymers in packaging applications, the interrelation between a plasticizer and a specific polymer needs to be understood.

  • 139.
    Arias, Veluska
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Nano-Stereocomplexation of Polylactide (PLA) Spheres by Spray Droplet Atomization2014In: Macromolecular rapid communications, ISSN 1022-1336, E-ISSN 1521-3927, Vol. 35, no 22, p. 1949-1953Article in journal (Refereed)
    Abstract [en]

    A direct, efficient, and scalable method to prepare stereocomplexed polylactide (PLA)-based nanoparticles (NPs) is achieved. By an appropriate combination of fabrication parameters, NPs with controlled shape and crystalline morphology are obtained and even pure PLA stereocomplexes (PLASC) are successfully prepared using the spray-drying technology. The formed particles of varying D- and L-LA content have an average size of approximate to 400 nm, where the smallest size is obtained for PLA50, which has an equimolar composition of PLLA and PDLA in solution. Raman spectra of the particles show the typical shifts for PLASC in PLA50, and thermal analysis indicates the presence of pure stereocomplexation, with only one melting peak at 226 degrees C. Topographic images of the particles exhibit a single phase with different surface roughness in correlation with the thermal analysis. A high yield of spherically shaped particles is obtained. The results clearly provide a proficient method for achieving PLASC NPs that are expected to function as renewable materials in PLA-based nanocomposites and potentially as more stable drug delivery carriers.

  • 140.
    Arias, Veluska
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Höglund, Anders
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Homocomposites of Polylactide (PLA) with Induced Interfacial Stereocomplex Crystallites2015In: ACS Sustainable Chemistry & Engineering, ISSN 2168-0485, Vol. 3, no 9, p. 2220-2231Article in journal (Refereed)
    Abstract [en]

    The demand for “green” degradable composite materials increases with growing environmental awareness. The key challenge is achieving the preferred physical properties and maintaining their eco-attributes in terms of the degradability of the matrix and the filler. Herein, we have designed a series of “green” homocomposites materials based purely on polylactide (PLA) polymers with different structures. Film-extruded homocomposites were prepared by melt-blending PLA matrixes (which had different degrees of crystallinity) with PLLA and PLA stereocomplex (SC) particles. The PLLA and SC particles were spherical and with 300–500 nm size. Interfacial crystalline structures in the form of stereocomplexes were obtained for certain particulate-homocomposite formulations. These SC crystallites were found at the particle/matrix interface when adding PLLA particles to a PLA matrix with d-lactide units, as confirmed by XRD and DSC data analyses. For all homocomposites, the PLLA and SC particles acted as nucleating agents and enhanced the crystallization of the PLA matrixes. The SC particles were more rigid and had a higher Young’s modulus compared with the PLLA particles. The mechanical properties of the homocomposites varied with particle size, rigidity, and the interfacial adhesion between the particles and the matrix. An improved tensile strength in the homocomposites was achieved from the interfacial stereocomplex formation. Hereafter, homocomposites with tunable crystalline arrangements and subsequently physical properties, are promising alternatives in strive for eco-composites and by this, creating materials that are completely degradable and sustainable.

  • 141.
    Arjmand, Mehdi
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Motahari, K.
    Energy conservation in atmospheric distillation columns by modifying vapour feed inlet tray2010In: 19th International Congress of Chemical and Process Engineering, CHISA 2010 and 7th European Congress of Chemical Engineering, ECCE-7, 2010Conference paper (Refereed)
    Abstract [en]

    A discussion on energy conservation in atmospheric distillation columns by modifying vapor feed inlet tray covers the basic equipment required for standard continuous industrial distillation; proposal to insert the vapor product of the flash drum into upper trays of the column separately; side stream products; investment costs; and case study involving an atmospheric distillation of a mixture of benzene and toluene. This is an abstract of a paper presented at the 7th European Congress of Chemical Engineering-7 and 19th International Congress of Chemical and Process Engineering CHISA (Prague, Czech Republic 8/28/2010-9/1/2010).

  • 142.
    Arkannia, Maral
    KTH, School of Chemical Science and Engineering (CHE).
    Improved Impregnation of Wood Chips and Increased Pulp Yield by Sulfate Cooking2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim in pulp production is to liberate the wood fibres. This study investigates the possibility of using a high effective alkali charge and a low temperature in the impregnation step when using Kraft cooking to produce pulp. This specific approach increases the rate of diffusion without risking enhancing the peeling process, which could result in a higher yield. This study has used eucalyptus wood chips and the impregnation step has been carried out by using an alkali concentration similar to what is currently being used in the pulp mills, which is in this study is referred to as "REF", and the higher alkali concentration which is referred to as HAI. The impregnation temperature for the REF case was 130 °C and for the HAI cases were 105 °C and 115 °C. The study was divided in two parts; an impregnation pre-study and a cooking study. The cooking parameters were kept constant because in this study only the impregnation has been of interest.

    The results from the impregnation pre-study were that for the HAI cases, when the temperature increased, the residual alkali decreased. The temperature also affected the yield, in such way that as the temperature increased, the yield decreased which means that more carbohydrates were dissolved. In the cooking study, the high alkali impregnation resulted in shorter cooking times. The initial concentration of OH

    - in the cooking was too low (0.6 M) and this made the delignification eventually decline.

  • 143.
    Arkannia, Maral
    KTH, School of Chemical Science and Engineering (CHE).
    Produktion av biodiesel med heterogena katalysatorer2014Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The production of biodiesel, also known as Fatty Acid Methyl Esther (FAME), has been studied by modifying some parameters to increase it’s overall yield. In this study, vegetable oil; specifically rapeseed oil, and methanol were used. The primary catalyst used for this study was calcium oxide. However, calcium oxide along with lithium was also used to study if there were differences in the yield. This was to observe if the catalyst behaved differently in the presence of lithium. The parameters used for this study include a methanol to oil molar ratio of 4, 6 and 8 and the temperature was set to either between 50 ° C or 60 ° C. The amount of catalyst used was 1.4 g and 2.8 g per 60 ml oil with a stirring speed of either 500 rpm or 1000 rpm with an overall reaction time of 1 hour or 2 hours. Based on the test results obtained from gas chromatography, it was determined that the biodiesel yield did not vary significantly when only calcium oxide and calcium oxide along with lithium was used to drive the reaction.

    All experiments had a yield of over 90% but most of them generated a 100% yield which proved to be advantageous. In comparison to previous studies, the differences in the percent yield is not high. Two of the parameters, the molar ratio of methanol/oil and the temperature did not affect the production yield. Even the lowest amount of catalyst (1.4 g) and the shortest response time (1 h) was sufficient to generate a good yield. A stirring speed of 500 rpm proved to produce a maximum yield. Increasing the speed of the stir bar to 1000 rpm did not result in a higher yield. None of the parameters used contributed to a lower yield; therefore, all the parameters can be considered to generated a high yield in varying amounts. The high yield obtained for our laboratory experiments showed no significant difference compared to with the large-scale industrial production of biodiesel with the use of the same catalyst, where the yield is over 98%.

  • 144.
    Armandt, Dannielle
    KTH, School of Chemical Science and Engineering (CHE).
    En studie för att utveckla matavfallsinsamlingen i Nacka kommun2017Independent thesis Basic level (professional degree), 12 credits / 18 HE creditsStudent thesis
  • 145.
    Arnau, Laurent
    KTH, School of Chemical Science and Engineering (CHE).
    Techno-Economic Feasibility Study for the Production of Microalgae Based Plant Biostimulant2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Microalgae are considered as a potential feedstock for many promising applications. Some active substances in microalgae have plant biostimulation effects potentially useful in agriculture. However, to produce such a microalgal biomass, specific microalgae cultivation and post-treatment processes must be designed to preserve active substances. A particular focus is provided on cultivation (tubular photobioreactor) and different plausible post-treatment scenarios for microalgae separation (flocculation and centrifugation) and preservation (sterilization and drying). For each step, yield and energy consumption are modeled using data taken from literature or lab and pilot scale experiments. Industrial equipment for scale-up process is also studied by comparing existing systems. These models enable to make an economic evaluation of the whole process and to study its profitability for each scenario. The breakeven price is calculated as a function of the production rate. Several parameters are suggested to improve system efficiency and profitability at the end of this study. However, a better microalgae characterization and more experiments on potential post-treatment systems are required to improve the accuracy of the model.

  • 146.
    Arrhenius Håkansson, Isabella
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Miljöprestandan hos dagens solceller - produktion av solceller och förslag till alternativa produktionsprocesser2018Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The solar cell industry is one of the fastest growing industries in the world. This is due to thedeclining prices of solar cells and that many countries now try to reduce their greenhouse gasemissions. The growing industry leads to an increased range of variants and suppliers of solarcells on the market. The environmental problems of solar cells occur during the production ofthe various components, as well as in the recovery of the used solar cells.

    The studied solar cells are mono- and multi-crystalline silicon cells, cadmium telluride (CdTe)and CIGS/CIS. The mono- and multi-crystalline solar cells are produced from purified siliconwhich achieves a purity of 6N (SG-Si), where silicon is doped with phosphorus to produce nsemiconductorand the p-semiconductor is doped with boron.

    For thin film solar cell CdTe, CdS is used as the n-semiconductor and the p-semiconductorconsists of cadmium and tellurium. For thin film solar cell CIGS/CIS, copper, indium, galliumand selenium are used as p-semiconductors and CdS as n-semiconductors.

    For the monocrystalline solar cells, a recovery rate of 96% can be achieved, which is doneeconomically and environmentally. For CdTe, a 95% recycled material is obtained for glass,90% for CdTe and 90% for CdS. While for CIGS/CIS, glass, EVA, selenium, aluminium,indium and gallium materials can be recycled.

    The chemicals used during the processes have been classified within a risk categorization,where the majority of the chemicals used are classified as high- and very high risk. The greaterimpact on the environment at the production location is due to the energy supply used sinceonly transport accounts for 1,6 to 2,8 % of carbondioxide emissions from solar cells.

    The parameters that were considered to have a major impact on the environment are the loadfrom critical material extraction, the power supply used during production, the hazardouschemicals used during production and recycling, and the air and waterborne emissions thatarise during production and recycling.

    For all solar cells, non-virgin aluminium should be used as construction material for the frame,or it should be without frames. Manufacturers of solar cells should clean the waterconsumption that occurs and recycle water to the their utmost ability. The factories should alsouse a recycling center for their trash and residues, or recycle at the factory. A clear follow-upand residual product plan should exist for the produced solar cells, which can be done throughPV CYCLE. Companies should work actively in matters relating to health, safety, humanrights, labour law and comply with the rules prevailing in the current country.

  • 147.
    Artman, Anna
    KTH, School of Chemical Science and Engineering (CHE).
    Avvattning av nanocellulosa i en DDA2015Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Through laboratory experiments, dewatering and retention of nanocellulose in a DDA (Dynamic Drainage Analyzer) were analysed. By adding retention chemicals in varied amounts, the effects on the dewatering was shown. The Job initiator was Innventia and the laboratory work were made at SP's laboratory where the DDA instrument was available. The DDA instrument is similar to the machine that is used for paper manufacturing in a large scale and therefore, it could be possible to dewater nanocellulose on a similar instrument.

    The goal of the thesis was to develop a nanocellulose film with good barrier properties but also to see how adding carrier fibers effect the properties of the film. The goal was also to see if the retention and dewatering time of nanocellulose are connected and whether it is possible to obtain repeatable results.

    Two different wires were also examined in the laboratory experiments in a DDA, the Albanywire and the Stratexwire. The Albany wire was denser than the Stratex wire and the effect that the density caused on retention and dewatering time was examined.

    Nanocellulose or Microfibrillated cellulose (MFC) is a new and renewable material that is made from wood fibers and is characterized by its gelatinous appearance. [4] Nanocellulose is suited for a variety of products, such as barriers, alone in the form of films or mixed in products. In the manufacture of nanocellulose a homogenizer is used which decomposes cellulose fibers to fibrils fibril aggregate. This was previously a problem while the fibers clogged the homogenizer and the production had a high energy consumption. [4] When it comes to making a nanocellulose film the problems with dewatering remains.

    The nanocellulose was diluted to the desired concentration and before the laboratory experiments it was run through a homogenizer, to disperse the fibrils in the liquid after the dilution. The carrier fibers was prepared in a blender with two liters of tap water before it was added to the homogenized nanocellulose.

    During the experiment in the DDA the amount and proportion of the MFC (microfibrillar cellulose) and carrier fibers (Modorefmassa) was varied. To the MFC and carrier fiber suspension in the DDA two retention chemicals were added in each experiment, C- PAM PL -1520 and EKA NP- 780 in varying amounts. After the dewatering of nanocellulose in the DDA the films were pressed at different pressures and times, thereafter the oxygen permeability was analyzed.

    The film that was considered the most suitable referring to dewatering in the DDA during the attempts was at 0.2 % with 90 % MFC and 10 % carrier fibers. The film gave the highest retention, a good oxygen barrier and was easy to handle. What can be seen from the results of the oxygen barrier measurement is that at 0.2 % with 90 % MFC and 10% carrier fibers obtained the lowest value OTR (oxygen transmission rate), which indicates on a good oxygen barrier. Retention at this concentration was the highest at 87.1 %, while the drainage time was nearly 250 seconds. The dewatering time was high, however during this concentration it’s sometimes difficult to see when the dewatering ended while the time was clocked manually.

    Conclusions from the results are that the carrier fibers doesn’t have a negatively effect on the films, rather they can benefit both the retention and oxygen barrier, however a higher paper weight was obtained and the dewatering time became longer.

  • 148.
    Ascue Avalos, Katerin
    KTH, School of Chemical Science and Engineering (CHE).
    En undersökning av potentialerna för de svenska förnyelsebara primära energikällor till år 2020 och 20502016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The effects of fossil-based energy are becoming increasingly evident. It is particularly visible in the world's climate change. In order to avoid greater consequences, the fossil-based energy sources need to be replaced by renewable ones to reduce the greenhouse gas emissions.

    Sweden aims to have no net emissions of greenhouse gases in 2050. There are good prospects for achieving this, but there are several ways to reach it and many opinions about how to do it.

    This thesis has studied the possibilities for the development of the various renewable primary energy sources until the years 2020 and 2050. The primary energy sources include hydropower, wind, biomass and solar power. The survey is based on the existing estimates and projections.

    The energy potential includes only the potential that exist within the borders of Sweden and do not include imported energy. The work will mainly affect the physical and practical potentials – the latter also includes economic aspects – and is based on a literature survey.

    The survey revealed that hydropower will increase its annual hydropower production with       8 TWh until the year 2050 as a combination of increased efficiency and climate changes that alter the amount of water flows. Regarding wind power, it was concluded that there will be a total of about 22 TWh annual electricity from wind turbines in 2050 and about 37 TWh/year by 2050. The approximation for 2050 is made with the assumption that financial support for offshore wind power will be introduced. The use of bioenergy will increase in the future and the estimates regarding the potential showed large variations. Solar power is increasing and it was concluded that it will be at least 5 TWh/year in 2020.

  • 149.
    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.

     

  • 150.
    Ashour, Radwa
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering. Nuclear Materials Authority, P.O. Box 530, 11381 El Maadi, Cairo, Egypt.
    Samouhos, Michail
    Swedish University of Agricultural Sciences, Department of Molecular Sciences, Uppsala BioCentre.
    Polido Legaria, Elizabeth
    Swedish University of Agricultural Sciences, Department of Molecular Sciences, Uppsala BioCentre.
    Svärd, Michael
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Transport Phenomena.
    Högblom, Joakim
    AkzoNobel, Pulp and Performance Chemicals AB.
    Forsberg, Kerstin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Palmlöf, Magnus
    Kessler, Vadim G.
    Swedish University of Agricultural Sciences, Department of Molecular Sciences, Uppsala BioCentre.
    Seisenbaeva, Gulaim A.
    Swedish University of Agricultural Sciences, Department of Molecular Sciences, Uppsala BioCentre.
    Rasmuson, Åke C.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    DTPA-Functionalized Silica Nano- and Microparticles for Adsorption and Chromatographic Separation of Rare Earth Elements2018In: ACS Sustainable Chemistry & Engineering, ISSN 2168-0485, Vol. 6, no 5, p. 6889-6900Article in journal (Refereed)
    Abstract [en]

    Silica nanoparticles and porous microparticles have been successfully functionalized with a monolayer of DTPA-derived ligands. The ligand grafting is chemically robust and does not appreciably influence the morphology or the structure of the material. The produced particles exhibit quick kinetics and high capacity for REE adsorption. The feasibility of using the DTPA-functionalized microparticles for chromatographic separation of rare earth elements has been investigated for different sample concentrations, elution modes, eluent concentrations, eluent flow rates, and column temperatures. Good separation of the La(III), Ce(III), Pr(III), Nd(III), and Dy(III) ions was achieved using HNO3 as eluent using a linear concentration gradient from 0 to 0.15 M over 55 min. The long-term performance of the functionalized column has been verified, with very little deterioration recorded over more than 50 experiments. The results of this study demonstrate the potential for using DTPA-functionalized silica particles in a chromatographic process for separating these valuable elements from waste sources, as an environmentally preferable alternative to standard solvent-intensive processes.

1234567 101 - 150 of 2454
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf