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  • 1.
    Ahmadi, Mozhgan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Brage, Claes O.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Knoef, H.
    Van De Beld, B.
    Development of an on-line tar measurement method based on photo ionization technique2011In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 176, no 1, p. 250-252Article in journal (Refereed)
    Abstract [en]

    This paper presents work in progress for development of an on-line method based on PID (Photo Ionization Detector) for quantitative measurement of tar from biomass gasification. To calibrate the method the PID signals are compared to quantitative data of individual tar compounds obtained by an established reference method. The measured response factors for the model tar compounds demonstrated very good linearity. The PID approach was tested on-line with real producer gases from an atmospheric fluidized bed gasifier operated at 800-900 °C. The results suggest that PID can be used for continuous on-line tar measurement of product gases from biomass gasification.

  • 2.
    Ahmadi, Mozhgan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Knoef, Harrie
    Van De Beld, Bert
    Liliedahl, Truls
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Engvall, Klaus
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Development of a PID based on-line tar measurement method: Proof of concept2013In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 113, p. 113-121Article in journal (Refereed)
    Abstract [en]

    In this study, a proof of concept was conducted for an on-line tar analyzer based on photo ionization detection (PID). Tar model compounds (naphthalene, acenaphthene, acenaphthylene, fluorene, indane and indene) were used for the initial investigation of the analysis method. It was found that the analysis method has a high sensitivity and a linear behavior was observed between the PID response and the tar concentration over a wide concentration span. The on-line tar analysis method was successfully validated against the solid phase adsorption (SPA) method using a real producer gas.

  • 3.
    Ahmadi, Mozhgan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Brage, Claes
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Liliedahl, Truls
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Develompent of an online tar measuring method using ionization potential2010Conference paper (Refereed)
  • 4.
    Ahmadi, Mozhgan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Svensson, Erik Elm
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Application of solid phase microextraction (SPME) as a tar sampling method during real gasificationManuscript (preprint) (Other academic)
  • 5.
    Ahmadi, Mozhgan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Svensson, Erik Elm
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Application of Solid-Phase Microextraction (SPME) as a Tar Sampling Method2013In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 27, no 7, p. 3853-3860Article in journal (Refereed)
    Abstract [en]

    This paper presents the result of an investigation of the potential use of solid-phase microextraction (SPME) as a tar sampling method. The SPME stationary phase used was 50 mu m of polydimethylsiloxane (PDMS) coated on a fused silica fiber. Tar model compounds normally present in a producer gas from gasifiers, benzene, toluene, indane, indene, naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, and pyrene, were used in the investigation. The adsorbed compounds were analyzed by injection into gas chromatography coupled to a flame ionization detector (GC- FID). The amount of adsorbed tar on the SPME fiber determined the detection and quantification limits for the method. The results showed that adsorption of tar model compounds on the SPME fiber increased with decreasing polarity. The adsorption of compounds increased with a decreasing temperature, enabling a possibility to tune the sensitivity of the method by changing the sampling temperature. Conclusively, SPME has a very high potential as a tar sampling method and, in combination with GC- FID trace analysis of tar, is a feasible application.

  • 6.
    Bäbler, Matthäus Ulrich
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Phounglamcheik, Aekjuthon
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology. Luleå University of Technology, Sweden.
    Amovic, Marko
    Ljunggren, Rolf
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Modeling and pilot plant runs of slow biomass pyrolysis in a rotary kiln2017In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 207, p. 123-133Article in journal (Refereed)
    Abstract [en]

    Pyrolysis of biomass in a rotary kiln finds application both as an intermediate step in multistage gasification as well as a process on its own for the production of biochar. In this work, a numerical model for pyrolysis of lignocellulosic biomass in a rotary kiln is developed. The model is based on a set of conservation equations for mass and energy, combined with independent submodels for the pyrolysis reaction, heat transfer, and granular flow inside the kiln. The pyrolysis reaction is described by a two-step mechanism where biomass decays into gas, char, and tar that subsequently undergo further reactions; the heat transfer model accounts for conduction, convection and radiation inside the kiln; and the granular flow model is described by the well known Saeman model. The model is compared to experimental data obtained from a pilot scale rotary kiln pyrolyzer. In total 9 pilot plant trials at different feed flow rate and different heat supply were run. For moderate heat supplies we found good agreement between the model and the experiments while deviations were seen at high heat supply. Using the model to simulate various operation conditions reveals a strong interplay between heat transfer and granular flow which both are controlled by the kiln rotation speed. Also, the model indicates the importance of heat losses and lays the foundation for scale up calculations and process optimization.

  • 7. Cieclik, Monika
    et al.
    Kot, M.
    Reczyński, W.
    Engvall, Klas
    Rakowski, W.
    Kotarba, Andrzej
    Parylene coatings on stainless steel 316L surface for medical applications - Mechanical and protective properties2012In: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 32, no 1, p. 31-35Article in journal (Refereed)
  • 8.
    Cieslik, Monika
    et al.
    Jagiellonian University, Poland; Institute of Metallurgy and Materials Science, Poland.
    Engvall, Klas
    Swerea KIMAB AB, Sweden.
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Kotarba, Andrzej
    Jagiellonian University, Poland.
    Silane-parylene coating for improving corrosion resistance of stainless steel 316L implant material2011In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 53, no 1, p. 296-301Article in journal (Refereed)
    Abstract [en]

    The corrosion resistance of a two-layer polymer (silane + parylene) coating on implant stainless steel was investigated by microscopic observations and electrochemical measurements Long term exposure tests in Hanks solution revealed that the coating of 2 mu m can be successfully used for corrosion protection However the addition of H2O2 simulating the inflammatory response of human body environment causes a dramatic destruction of the protective coating Analysis of the experimental data in terms of circuit models enables proposing a deterioration mechanism OH radicals formed at the metal surface attack the polymer thus the deterioration starts from the metal/polymer interface and progress towards the outward surface.

  • 9. Cieślik, M.
    et al.
    Zimowski, Sławomir
    Golda, M.
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Rakowski, W.
    Kotarba, A.
    Engineering of bone fixation metal implants biointerface - Application of parylene C as versatile protective coating2012In: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 32, no 8, p. 2431-2435Article in journal (Refereed)
    Abstract [en]

    The tribological and protective properties of parylene C coatings (2-20 ÎŒm) on stainless steel 316L implant materials were investigated by means of electrochemical measurements and wear tests. The thickness and morphology of the CVD prepared coatings were characterized by scanning electron and laser confocal microscopy. The stability of the coatings was examined in contact with Hanks' solution and H 2O 2 (simulating the inflammatory response). It was concluded that silane-parylene C coating with the optimum thickness of 8 ÎŒm exhibits excellent wear resistance properties and limits the wear formation. The engineered versatile coating demonstrates sufficient elastomer properties, essential to sustain the implantation surgery strains and micromotions during long-term usage in the body.

  • 10. Cieślik, Monika
    et al.
    Reczyński, W.
    Janus, A. M.
    Engvall, Klas
    Socha, R. P.
    Kotarba, Andrzej
    Metal release and formation of surface precipitate at stainless steel grade 316 and Hanks solution interface - Inflammatory response and surface finishing effects2009In: Corrosion Science, Vol. 51, no 5, p. 1157-1162Article in journal (Refereed)
  • 11. Dahlquist, Erik
    et al.
    Mirmoshtaghi, Guilnaz
    Larsson, Eva K.
    Thorin, Eva
    Yan, Jinyue
    Engvall, Klas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Liliedahl, Truls
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Dong, C.
    Hu, X.
    Lu, Q.
    Modelling and simulation of biomass conversion processes2015In: 2013 8TH EUROSIM CONGRESS ON MODELLING AND SIMULATION (EUROSIM), 2015, p. 506-512Conference paper (Refereed)
    Abstract [en]

    By utilizing biomass gasification, the energy content of the biomass can be utilized to produce gas to be used for cogeneration of heat and power as well as other energy carriers such as fuels for vehicles. The concept is suitable for application to existing CHP plants as well as for utilizing spent liqour in small scale pulp and paper mills. The introduction would enable flexible energy utilization, use of problematic fuels as well as protects the environment by e.g. avoiding the release of toxic substances. In this paper, the possibilities to develop this concept is discussed. In this paper we compare different gasification processes with respect to what gas quality we get, and how the gasification can be modelled using different modelling approaches, and how these can be combined. Results from simulations are compared to experimental results from pilot plant operations in different scales and with different processes like CFB and BFB Technologies, athmospheric and pressurized, and using steam, air and oxygen as oxidizing media.

  • 12. Davidsson, Kent O.
    et al.
    Engvall, Klas
    Hagström, Magnus
    Korsgren, John G.
    Lönn, Benny
    Pettersson, Jan B. C.
    A surface ionization instrument for on-line measurements of alkali metal components in combustion: Instrument description and applications2002In: Energy and Fuels, Vol. 16, no 6, p. 1369-1377Article in journal (Refereed)
  • 13.
    Ding, Saiman
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Chemical Engineering.
    Engvall, Klas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Kantarelis, Efthymios
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology. KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Secondary tar cracking in fixed bed using char residues from the wood gasification2019Conference paper (Refereed)
    Abstract [en]

    Biomass gasification is a promising technology for production of synthesis gas, hydrogen (H2) and carbon monoxide (CO), which can be subsequently converted into valuable end products. However, high tar content in the product gas during gasification is one of the major problems, limiting the further usage of the producer gas. Tar decomposition using char from the pyrolysis of biomass becomes more popular. Alternatively, using char residues, derived from the gasification process itself, could also be a measure to further reducing the tar content. Char and char-supported catalysts have been studied for the decomposition of model tar compounds, such as toluene, benzene, naphthalene as well as phenol.Moreover, there is no information about interactions or synergistic effects between light and heavy tar model compounds in mixtures of toluene and naphthalene. In this study, the catalytic effect of char samples derived from entrained flow gasification and high pressure carbonization process, on the tar model compounds decomposition was investigated using a fixed-bed reactor. The effects of differently produced char on the tar cracking efficiency was evaluated at 800 °C and 900 °C at a weight hourly space velocity (WHSV) 0.2 h-1 and a tar concentration of 5 g/Nm3.The effect of differently produced char on the efficiency of tar cracking is also evaluated.  Preliminary results show that naphthalene and toluene conversion is increased over the char from the entrained flow with increased temperature.  It verifies the catalytic effect of char on tar removal. However, conversions decreased over time most likely due to a decrease in specific surface area from 42 to 1.5 m2/g during the test at 900 °C. Comparation of catalytic tar cracking properties between different chars will be provided later on.

     

  • 14.
    Ding, Saiman
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Ge, Yaxin
    Department of Chemistry and Molecular Biology, Atmospheric Science, University of Gothenburg, SE-412 96 Gothenburg, Sweden.
    Kantarelis, Efthymios
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Kong, Xiangrui
    Department of Chemistry and Molecular Biology, Atmospheric Science, University of Gothenburg, SE-412 96 Gothenburg, Sweden.
    Pettersson, Jan B.C.
    Department of Chemistry and Molecular Biology, Atmospheric Science, University of Gothenburg, SE-412 96 Gothenburg, Sweden.
    Engvall, Klas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Time-resolved alkali release during steam gasification of char in a fixed bed reactor2024In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 356, p. 129528-, article id 129528Article in journal (Refereed)
    Abstract [en]

    In this study time-resolved char conversion and alkali release under steam gasification conditions were investigated using a fixed bed reactor. The behaviour of an industrial char and chars produced from straw and furniture waste was investigated. For woody chars, an increase in gasification reactivity is observed together with a notable alkali release as the gasification approaches completion (degree of conversion > 0.8). In contrast, straw char exhibited a decrease in conversion rate and alkali release throughout the gasification process, attributed to the formation of catalytically inactive potassium silicates inhibiting the catalytic role of alkali. Aerosol particles in the 0.01–22 µm size range are emitted during the char conversion. A fraction is formed by nucleation of alkali compounds and other condensable gases. A wide particle distribution that extends over the whole size range is also observed, and the particles are likely to consist of solid char fragments. The study concludes on the importance of alkali release, illustrating the difference in alkali release pattern for high and low ash char.

  • 15.
    Ding, Saiman
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Chemical Engineering.
    Kantarelis, Efthymios
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Engvall, Klas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Effects of Porous Structure Development and Ash on the Steam Gasification Reactivity of Biochar Residues from a Commercial Gasifier at Different Temperatures2020In: Energies, E-ISSN 1996-1073, Vol. 13, no 18, article id 5004Article in journal (Refereed)
    Abstract [en]

    The present study aims at investigating the effects of porous structure development and ash content on the observed reactivity during steam gasification of biochar residues from a commercial gasifier. The experiments were conducted at a temperature range of 700 to 800 °C using biochar, derived from entrained flow gasification of biomass, under isothermal conditions using a thermogravimetric analyzer. The pore size distribution, surface area and morphology of char samples were determined by N2 physiosorption and scanning electron microscopy (SEM). The results showed that the gasification temperature does not affect the porous structure development considerably. The total surface area of char exhibits a threefold increase, while the total pore volume increase ranges between 2.0 and 5.3 times, at all temperatures. Both properties are directly proportional to the observed reactivity, especially at conversions up to 70%. Catalytic effects of the mineral matter of the char (mainly potassium) become predominant at the later stages of conversion (conversion greater than 70%).

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  • 16.
    Ding, Saiman
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Kantarelis, Efthymios
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Engvall, Klas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Potassium-Induced Phenomena and Their Effects on the Intrinsic Reactivity of Biomass-Derived Char during Steam Gasification2023In: ACS Omega, E-ISSN 2470-1343, Vol. 8, no 32, p. 29131-29142Article in journal (Refereed)
    Abstract [en]

    The mineral content of biomass plays an important role in the gasification rate of biomass-derived char. The understanding and quantification of mineral-related phenomena are thus of importance when considering gasification reactor design. In the present work, the potassium-induced catalytic phenomena during gasification of biomass-derived char have been studied. Char samples with similar structure and different intrinsic potassium content were gasified in a steam atmosphere at a temperature range of 700-800 °C. It was found that for all the samples, irrespective of the temperature and the initial potassium content, there is a critical K/C ratio (5 × 10-3), whereafter the catalytic phenomena prevail. The instantaneous conversion rate of the char is positively correlated with the potassium content and the progressively increasing conversion. The application of the modified random pore model was able to capture the later stages of conversion by the introduction of two additional parameters (c and p). It was found that these constants are not just fitting parameters but that there is an underlying physical significance with c being directly related to the intrinsic potassium content while being temperature independent and with p being temperature dependent.

  • 17.
    Ding, Saiman
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Kantarelis, Efthymios
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Engvall, Klas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Potassium-induced phenomena and their effects on the intrinsic reactivity of biomass-derived char during steam gasification.Manuscript (preprint) (Other academic)
  • 18. Engvall, Klas
    et al.
    Holmlid, Leif
    Field ionisation of excited alkali atoms emitted from catalyst surfaces1992In: Applied Surface Science, Vol. 55, no 4, p. 303-308Article in journal (Refereed)
  • 19. Engvall, Klas
    et al.
    Holmlid, Leif
    Kotarba, Andrzej
    Pettersson, Jan B. C.
    Menon, P. Govind
    Skaugset, P.
    Potassium promoter in industrial ammonia synthesis catalyst: Studies by surface ionization1996In: Applied Catalysis A: General, Vol. 134, no 2, p. 239-246Article in journal (Refereed)
  • 20. Engvall, Klas
    et al.
    Holmlid, Leif
    Menon, P. Govind
    Comparative loss of alkali promoter by desorption from two catalysts for the dehydrogenation of ethyl benzene to styrene1991In: Applied Catalysis, Vol. 77, no 2, p. 235-241Article in journal (Refereed)
  • 21. Engvall, Klas
    et al.
    Holmlid, Leif
    Prinz, H.
    Hofmann, H.
    Loss of alkali promoter by desorption from promoted vanadium oxide catalysts1991In: Catalysis Letters, Vol. 11, no 1, p. 41-48Article in journal (Refereed)
  • 22. Engvall, Klas
    et al.
    Kotarba, Andrzej
    Holmlid, Leif
    Emission of excited potassium species from an industrial iron catalyst for ammonia synthesis1994In: Catalysis Letters, Vol. 26, no 1-2, p. 101-107Article in journal (Refereed)
  • 23. Engvall, Klas
    et al.
    Kotarba, Andrzej
    Holmlid, Leif
    Long-range diffusion of K promoter on an ammonia synthesis catalyst surface - Ionization of excited potassium species in the sample edge fields1999In: Journal of Catalysis, Vol. 181, no 2, p. 256-264Article in journal (Refereed)
  • 24.
    Engvall, Klas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Kusar, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Sjöström, Krister
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Pettersson, Lars J.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Upgrading of raw gas from biomass and waste gasification: Challenges and opportunities2011In: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 54, no 13-15, p. 949-959Article, review/survey (Refereed)
    Abstract [en]

    The depletion of fossil fuel-based resources and concerns for increasing emissions of CO2 call for newways of producing environmentally- friendly substitutes for motor fuels and chemicals. Thermo-chemical conversion of biomass andwaste using gasification is a strong candidate tomeet these challenges. For efficient and cost-effective application of this technique, novel solutions for hot gas cleaning are needed. This review highlights some important areas for improvement of upgrading technologies for pressurised fluidised bed gasification systems using biomass as a fuel.

  • 25.
    Engvall, Klas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Liliedahl, Truls
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Dahlquist, E.
    Biomass and black liquor gasification2013In: Technologies for Converting Biomass to Useful Energy: Combustion, Gasification, Pyrolysis, Torrefaction and Fermentation, CRC Press , 2013, p. 175-216Chapter in book (Other academic)
    Abstract [en]

    Modern society is profoundly dependent on fossil feed stocks to produce multiple products, such as transportation fuels, fine chemicals, pharmaceuticals, detergents, synthetic fibers, plastics, fertilizers, lubricants, solvents, waxes, etc., as well as heat and power (Demirbas, 2006). The fossil resources are not endless. Their price is increasing continuously due to increasing scarcity, and not regarded as sustainable from an environmental point of view (Kamm, 2006). A versatile resource, especially in terms of producing carbon-based products, to replace fossil feedstocks is biomass (Vlachos, 2010) or other sources originating form biomass, such as black liquor (BL). Conversion of biomass to other products can be performed either by biochemical or thermochemical processes. In the case of large-scale production of, for example, carbon-based products, thermo-chemical conversion is considered more efficient compared to biochemical processes (Zhang, 2010). Techniques for thermo-chemical conversion can be divided into pyrolysis, gasification, combustion and liquefaction. Among these techniques, gasification is a versatile platform for production of multiple products, as illustrated in Figure 6.1. 

  • 26.
    Farah, Elise
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Demianenko, Ludmilla
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology. Department of Energetics and Environmental Engineering, Institut National des Sciences Appliquées (INSA), Villeurbanne Cedex, 69621, Lyon, France, Villeurbanne Cedex.
    Engvall, Klas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Kantarelis, Efthymios
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Controlling the Activity and Selectivity of HZSM-5 Catalysts in the Conversion of Biomass-Derived Oxygenates Using Hierarchical Structures: The Effect of Crystalline Size and Intracrystalline Pore Dimensions on Olefins Selectivity and Catalyst Deactivation2023In: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 66, no 17-18, p. 1310-1328Article in journal (Refereed)
    Abstract [en]

    The conversion of biomass-derived oxygenates over zeolite catalysts constitutes a challenge for the efficient production of bio-based chemicals and fuels due to difficulty in controlling the selectivity and high coke formation of such reactions. This is partly attributed to the microstructure of zeolite catalyst which affects the conversion and selectivity of products derived from biomass-derived oxygenates. In this study, the conversion and deactivation characteristics of three different model oxygenates found in biomass bio-oil (namely, acetol, furfural and guaiacol) over ZSM-5 zeolites of varying acidity, pore and crystal size prepared with bottom-up and top-down approaches were evaluated using a fixed bed microreactor at atmospheric pressure and a space velocity of 5 h−1 at a temperature range of 450–650 °C. Analysis of the experimental results indicates that the optimum temperature for such conversions is in the vicinity of 600 °C allowing for complete conversion of the compounds and high resistance to coking. The mechanisms of those conversions are discussed based on the obtained results. In general, crystal size and mesoporosity induce easier access to active sites improving mass transfer but also alter the location type, and strength of acid sites allowing for higher yields of primary and intermediate products such as olefins.

  • 27.
    Ge, Yaxin
    et al.
    Univ Gothenburg, Dept Chem & Mol Biol, Atmospher Sci, SE-41296 Gothenburg, Sweden..
    Ding, Saiman
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Chemical Engineering.
    Kong, Xiangrui
    Univ Gothenburg, Dept Chem & Mol Biol, Atmospher Sci, SE-41296 Gothenburg, Sweden..
    Kantarelis, Efthymios
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Engvall, Klas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Pettersson, Jan B. C.
    Univ Gothenburg, Dept Chem & Mol Biol, Atmospher Sci, SE-41296 Gothenburg, Sweden..
    Real-time monitoring of alkali release during CO2 gasification of different types of biochar2022In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 327, article id 125102Article in journal (Refereed)
    Abstract [en]

    Potassium and sodium compounds play both positive and negative roles during biomass gasification, but the detailed behavior of alkali metal compounds remain incompletely understood. In this study, alkali release during CO2 gasification of biochar is characterized online with a surface ionization method in combination with thermogravimetric analysis of the char samples undergoing gasification. For wood chars, the alkali release rate follows a slowly decreasing trend as the char conversion proceeds, but increases by up to two orders of magnitude when the conversion approaches completion. In contrast, the alkali release from straw char is 40-50 times higher than observed for wood char and decreases continuously during the whole gasification process. A high temperature and a high CO2 concentration enhance both alkali release and char reactivity. The char preparation method also influences the alkali release from pine char, while the char reactivity is less affected. Alkali release and char reactivity are linked, but other factors including mineral content, surface area and char structure may play important roles for the observed reactivity. The results provide a basis for understanding of alkali behavior during gasification and may help optimize catalytic effects and reduce detrimental issues in biomass gasification.

  • 28. Ge, Yaxin
    et al.
    Ding, Saiman
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Kong, Xiangrui
    Kantarelis, Efthymios
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Engvall, Klas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Pettersson, Jan B.C.
    Online monitoring of alkali release during co-pyrolysis/gasification of forest and agricultural waste: Element migration and synergistic effects2023In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 172, p. 106745-106745, article id 106745Article in journal (Refereed)
    Abstract [en]

    Fuel blends may be used to meet several operational needs in thermal conversion of biomass waste, including optimization of ash properties and fuel conversion efficiency. In this study, online alkali measurements using surface ionization are employed to study synergistic effects produced by inorganic elements during co-pyrolysis/gasification of wood and straw waste. Synergistic effects on the fuel conversion behavior are not observed during co-pyrolysis, while alkali migration from straw to wood is clearly observed above 600 °C by online alkali monitoring. In contrast, synergistic effects on char conversion and alkali release are substantial during co-gasification. Positive effects on char reactivity during most of the gasification process are attributed to alkali migration from the straw to the wood char, and the most pronounced effect occurs at a gasification temperature of 900 °C and a straw content of 25%. Negative effects on char reactivity are observed at the final gasification stage, which is associated with a significantly reduced alkali release from fuel blends compared to pure wood char. The effect is attributed to the migration of silicon, phosphorus, and aluminum to the wood char, as revealed by scanning electron microscopy with energy dispersive spectroscopy, where the elements react with alkali to form catalytically inactive compounds. The mixing of biofuels is concluded to result in substantial effects on the fuel conversion efficiency, which should be taken into consideration in thermochemical conversion of biomass.

  • 29. Ge, Yaxin
    et al.
    Ding, Saiman
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Kong, Xiangrui
    Kantarelis, Efthymios
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Engvall, Klas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Öhman, Marcus
    Pettersson, Jan B.C.
    Effects of used bed materials on char gasification: Investigating the role of element migration using online alkali measurements2022In: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 238, p. 107491-107491, article id 107491Article in journal (Refereed)
    Abstract [en]

    Online alkali measurements using surface ionization are employed to study alkali release during heating of used industrial fluidized bed materials and gasification of biomass-based char and bed material mixtures. The alkali release from the bed materials starts at 820 °C and increases with temperature, the time a bed material has experienced in an industrial process, and in the presence of CO2. Online alkali measurement during heating of char mixed with used bed material shows significant alkali uptake by the char. Complementary SEM-EDS studies confirm the alkali results and indicate that other important inorganic elements including Si, Mg, and Ca also migrate from the bed material to the char. The migration of elements initially enhances alkali release and char reactivity, but significantly reduces both during the final stage of the gasification. The observed effects on char gasification become more pronounced with increasing amount of bed material and increasing time the material experienced in an industrial process. The ash-layer on the used bed material is concluded to play an important role as a carrier of alkali and other active components. The char and bed material systems are closely connected under operational conditions, and their material exchange has important implications for the thermal conversion. 

  • 30.
    Ge, Yaxin
    et al.
    Univ Gothenburg, Dept Chem & Mol Biol, Atmospher Sci, SE-41296 Gothenburg, Sweden..
    Ding, Saiman
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Zhang, Wennan
    Mid Sweden Univ, Dept Chem Engn, SE-85170 Sundsvall, Sweden..
    Kong, Xiangrui
    Univ Gothenburg, Dept Chem & Mol Biol, Atmospher Sci, SE-41296 Gothenburg, Sweden..
    Engvall, Klas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Pettersson, Jan B. C.
    Univ Gothenburg, Dept Chem & Mol Biol, Atmospher Sci, SE-41296 Gothenburg, Sweden..
    Effect of fresh bed materials on alkali release and thermogravimetric behavior during straw gasification2023In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 336, article id 127143Article in journal (Refereed)
    Abstract [en]

    Alkali-associated problems are key issues for the efficient use of straw that is available as a major renewable energy resource worldwide. The effects of six bed materials commonly used in fluidized bed reactors on straw pyrolysis and char gasification were evaluated using online monitoring of alkali release and thermogravimetric analysis. Scanning electron microscopy with energy dispersive spectroscopy was used to determine the elemental composition of the char surface. In the straw pyrolysis stage, alkali release is reduced by the addition of dolomite and silica due to alkali adsorption on the bed materials, and enhanced by the addition of alumina because of its high sodium content. In the char gasification stage, silica, sea sand, olivine, and ilmenite reduce the char reactivity and alkali release, which is attributed to transfer of Si and Ti from the bed materials to the char and reaction with alkali to form stable and catalytically inactive compounds. Alumina also reduces the char conversion rate by transfer of Al to the char and formation of K-Al-Si and Ca-Al-Si compounds, while alkali release from the straw and alumina blend remains high due to the high Na content in alumina. Dolomite initially appears to increase the char gasification reactivity, but the results are affected by conversion of volatile matter that deposited on the dolomite in the straw pyrolysis stage. Dolomite also significantly increases the alkali release, which is attributed to Ca reactions with aluminosilicate compounds that allow potassium to remain in volatile form. Fresh bed materials are concluded to have significant effects on straw conversion depending on their chemical composition, and the results can contribute to the understanding required for efficient use of straw in commercial applications of biomass thermochemical conversion.

  • 31.
    Ge, Yaxin
    et al.
    Department of Chemistry and Molecular Biology, Atmospheric Science, University of Gothenburg, SE-412 96 Gothenburg, Sweden.
    Ding, Saiman
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Zhang, Wennan
    Department of Chemical Engineering, Mid Sweden University, SE-85170 Sundsvall, Sweden.
    Kong, Xiangrui
    Department of Chemistry and Molecular Biology, Atmospheric Science, University of Gothenburg, SE-412 96 Gothenburg, Sweden.
    Kantarelis, Efthymios
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Engvall, Klas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Pettersson, Jan B.C.
    Department of Chemistry and Molecular Biology, Atmospheric Science, University of Gothenburg, SE-412 96 Gothenburg, Sweden.
    Impacts of fresh bed materials on alkali release and fuel conversion rate during wood pyrolysis and char gasification2023In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 353, article id 129161Article in journal (Refereed)
    Abstract [en]

    Bed materials provide efficient heat transfer and catalytic function in the thermochemical conversion of biomass, but their interactions with the fuel remain incompletely understood. In this study, the effects of bed materials on alkali release and fuel conversion during wood pyrolysis and CO2 gasification are investigated by online alkali detection combined with thermogravimetric analysis. The investigated bed materials include silica, sea sand, alumina and the natural ores olivine, ilmenite and dolomite. Only dolomite has a significant effect on fuel mass loss and alkali release during wood pyrolysis, while all bed materials influence char reactivity and alkali release during gasification. Sea sand, alumina and dolomite enhance the char gasification during the whole or most of the gasification process, which is related to alkali migration from the bed materials. All bed materials affect char reactivity and alkali release when the conversion approaches completion, and small amounts of some bed materials reduce the alkali release by an order of magnitude. The findings can be understood based on the chemical composition of the different materials. Silicon-rich materials reduce the levels of catalytically active alkali by formation of stable alkali silicates, and a similar explanation applies for ilmenite that captures alkali efficiently. Magnesium and calcium in contrast promote alkali release through their influence on alkali silicate chemistry. Analysis of char surfaces using scanning electron microscopy with energy dispersive spectroscopy indicates that low amounts of several elements are transferred from the bed material to the char where they may be directly involved in the char conversion process. The transferred elements are specific for each bed material and relates to their chemical composition. Mechanisms for material exchange between bed material and char are discussed.

  • 32. Ghadami Yazdi, M.
    et al.
    Moud, Pouya H.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Marks, K.
    Piskorz, W.
    Öström, H.
    Hansson, T.
    Kotarba, A.
    Engvall, Klas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Göthelid, M.
    Naphthalene on Ni(111): Experimental and Theoretical Insights into Adsorption, Dehydrogenation, and Carbon Passivation2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 40, p. 22199-22207Article in journal (Refereed)
    Abstract [en]

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

  • 33.
    Ghadami Yazdi, Milad
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    H. Moud, Pouya
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology. KTH.
    Marks, Kess
    Piskorz, Witold
    Öström, Henrik
    Hansson, Tony
    Kotarba, Andrzej
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Göthelid, Mats
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    Naphthalene on Ni(111): experimental and theoretical insights into adsorption, dehydrogenation and carbon passivationManuscript (preprint) (Other academic)
    Abstract [en]

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

  • 34. Golda-Cepa, M.
    et al.
    Aminlashgari, Nina
    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, Polymer Technology.
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Kotarba, A.
    LDI-MS examination of oxygen plasma modified polymer for designing tailored implant biointerfaces2014In: RSC Advances, E-ISSN 2046-2069, Vol. 4, no 50, p. 26240-26243Article in journal (Refereed)
    Abstract [en]

    A versatile polymer coating for biomaterials was fabricated by the mild oxygen plasma treatment of Chemical Vapour Deposited (CVD) parylene C. The surface properties were tailored while the excellent protective properties of the bulk were preserved. The species, formed due to the plasma functionalisation, were fingerprinted by a novel Laser Desorption/Ionisation-Mass Spectrometry (LDI-MS) method. Improved osteosarcoma cells (line MG-63) attachment and viability on a modified surface were demonstrated.

  • 35. Golda-Cepa, M.
    et al.
    Brzychczy-Wloch, M.
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Aminlashgari, Nina
    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.
    Kotarba, A.
    Microbiological investigations of oxygen plasma treated parylene C surfaces for metal implant coating2015In: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 52, p. 273-281Article in journal (Refereed)
    Abstract [en]

    Parylene C surface was modified by the use of oxygen plasma treatment and characterized by microscopic and surface-sensitive techniques (E-SEM, AFM, XPS, LDI-TOF-MS, contact angle). The influence of the treatment on surface properties was investigated by calculations of surface free energy (Owens-Wendt method). Moreover, early adhesion (Culture Plate Method, Optical Microscopy Test) and biofilm formation ability (Cristal Violet Assay) on the parylene C surface was investigated. The bacteria strains which are common causative agents of medical device-associated infections (Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa - reference strains and clinical isolates) were used. It was concluded that chemical (oxygen insertion) and physical (nanotopography generation) changes, have a significant impact on the biocompatibility in terms of increased hydrophilicity (θw of unmodified sample = 88° ± 2°, θw of 60 min modified sample = 17.6° ± 0.8°) and surface free energy (SFE of unmodified sample = 42.4 mJ/m2, and for 60 min modified sample = 70.1 mJ/m2). At the same time, no statistical effect on biofilm production and bacteria attachment to the modified surface of any of the tested strains was observed.

  • 36. Golda-Cepa, M.
    et al.
    Chorylek, A.
    Chytrosz, P.
    Brzychczy-Wloch, M.
    Jaworska, J.
    Kasperczyk, J.
    Hakkarainen, M.
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Kotarba, A.
    Multifunctional PLGA/Parylene C Coating for Implant Materials: An Integral Approach for Biointerface Optimization2016In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 8, no 34, p. 22093-22105Article in journal (Refereed)
    Abstract [en]

    Functionalizing implant surfaces is critical for improving their performance. An integrated approach was employed to develop a multifunctional implant:coating based on oxygen plasma-modified parylene C and drug-loaded, biodegradable poly(DL-lactide-co-glycolide) (PLGA). The key functional attributes of the coating (i.e., anti-corrosion, biocompatible, anti-infection, and therapeutic) were thoroughly characterized at each fabrication step by spectroscopic, microscopic, and biologic methods and at different scales, ranging from molecular, through the nano- and microscales to the macroscopic scale. The chemistry of each layer was demonstrated separately, and their mutual affinity was shown to be indispensable for the development of versatile coatings, for implant applications.

  • 37. Golda-Cepa, M.
    et al.
    Engvall, Klas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Hakkarainen, Minna
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymer Technology.
    Kotarba, A.
    Recent progress on parylene C polymer for biomedical applications: A review2020In: Progress in organic coatings, ISSN 0300-9440, E-ISSN 1873-331X, Vol. 140, article id 105493Article, review/survey (Refereed)
    Abstract [en]

    Parylene C films have numerous advantages. The versatility of parylene C coatings makes them useful in a broad range of biomedical applications. The coatings are widely used commercially because of the unique combination of their physicochemical properties, i.e. flexibility and dielectricity. The chemical vapour deposition process enables parylene C conformal coatings to be applied to even the most complex medical devices. The coatings can be customised for the desired application using surface modification methods, which alter surface chemistry and topography. In this review, we summarise the last ten years (2008–2018) of research on parylene C for biomedical applications. We discuss how parylene C properties can be modulated through surface and bulk modifications to improve its key functions, i.e. anticorrosive, biocompatible, anti-infection, and therapeutic functions. We emphasise current and potential biomedical applications and finally highlight the advantages and limitations of the coatings, pointing out the perspectives and the most promising research trends.

  • 38. Golda-Cepa, M.
    et al.
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Kotarba, A.
    Development of crystalline-amorphous parylene C structure in micro-and nano-range towards enhanced biocompatibility: the importance of oxygen plasma treatment time2015In: RSC Advances, E-ISSN 2046-2069, Vol. 5, no 60, p. 48816-48821Article in journal (Refereed)
    Abstract [en]

    The crystalline-amorphous parylene C structure was fabricated by Chemical Vapour Deposited (CVD) and functionalised in the micro- and nano-range with the oxygen plasma treatment. The evolution of thermal stability, structure and surface biocompatibility of parylene C films as an effect of oxygen plasma treatment time were evaluated by means of thermogravimetric/differential thermal analysis (TG/DTA), X-Ray Diffraction (XRD) and cells adhesion tests (crystal violet assay, fluorescence microscopy). The results are epitomized by a crystalline-amorphous parylene C structural model. It was found that the time of oxygen plasma treatment is critical for adhesion of osteoblast cells with the optimum of 5-8 minutes.

  • 39.
    González Arcos, Angélica Viviana
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Diomedi, Matteo
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Lanza, Roberto
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Effect of potassium electrochemical promotion in biomass-tar reformingManuscript (preprint) (Other academic)
  • 40.
    González Arcos, Angélica Viviana
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Rostrup-Nielsen, J.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Pettersson, Lars J.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Promoted RhPt bimetallic catalyst supported on δ-Al2O3 and CeO2-ZrO2 during full-scale autothermal reforming for automotive applications: Post-mortem characterization2015In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 491, p. 8-16Article in journal (Refereed)
    Abstract [en]

    The influence of sulfur and coke formation on the steam reforming of diesel was evaluated for two promoted RhPt bimetallic catalysts, composed of 1:1 Rh:Pt/10:10 La2O3: CeO2/ δ-Al2O3 (CAT 1) and 1:1 Rh:Pt/4:5 MgO: Y2O3/CeO2 − ZrO2 (CAT 2). The intrinsic activity is related to the total Rh and Pt area observed after the exposure to sulfur. Therefore, the degree of deactivation is related to the amount of sulfur deposited on the active metal sites. Sulfur analysis on the aged catalyst washcoat showed a decreasing sulfur concentration in the axial direction of the reformer. The estimated sulfur coverage related to metal surface area after 40 h on stream reached values of 0.145 in CAT 2, below the equilibrated sulfur coverage of 0.19 after tests with DIN 590. Thus, showing a partial deactivation due to sulfur poisoning. Further catalyst characterization on carbon deposits and thermal aging was performed by TPO, TGA, BET, CO chemisorption, and TEM analysis.

  • 41. Gołda, M.
    et al.
    Brzychczy-Włoch, M.
    Faryna, M.
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Kotarba, A.
    Oxygen plasma functionalization of parylene C coating for implants surface: Nanotopography and active sites for drug anchoring2013In: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 33, no 7, p. 4221-4227Article in journal (Refereed)
    Abstract [en]

    The effect of oxygen plasma treatment (t = 0.1-60 min, pO2 = 0.2 mbar, P = 50 W) of parylene C implant surface coating was investigated in order to check its influence on morphology (SEM, AFM observations), chemical composition (XPS analysis), hydrophilicity (contact angle measurements) and biocompatibility (MG-63 cell line and Staphylococcus aureus 24167 DSM adhesion screening). The modification procedure leads to oxygen insertion (up to 20 at.%) into the polymer matrix and together with surface topography changes has a dramatic impact on wettability (change of contact angle from θ = 78 ± 2 to θ = 33 ± 1.9 for unmodified and 60 min treated sample, respectively). As a result, the hydrophilic surface of modified parylene C promotes MG-63 cells growth and at the same time does not influence S. aureus adhesion. The obtained results clearly show that the plasma treatment of parylene C surface provides suitable polar groups (C = O, C-O, O-C = O, C-O-O and O-C(O)-O) for further development of the coating functionality.

  • 42.
    H. Moud, Pouya
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology. KTH.
    Kantarelis, Efthymios
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    J. Andersson, Klas
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Biomass pyrolysis gas conditioning over an iron-based catalyst for mild deoxygenation and hydrogen production2017In: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 211, p. 149-158Article in journal (Other academic)
    Abstract [en]

    Bio-crude is a renewable source for production of valuable energy carriers. Prior to its utilization, a conditioning step of the raw pyrolysis gas can be beneficial before the bio-crude is converted via catalytic hydrodeoxygenation (HDO) into liquid hydrocarbon products, or via steam reforming (SR) to synthesis gas/hydrogen. An experimental small industrial scale study for the chemistry of atmospheric pressure pyrolysis gas conditioning resulting in bio-crude deoxygenation and a hydrogen-rich gas using an iron-based catalyst without addition of hydrogen or steam is presented and discussed. Following a short catalyst stabilization period with fluctuating bed temperatures, the catalyst operated near 450°C at a space velocity of 1100 h-1 for 8 hours under stable conditions during which no significant catalyst deactivation was observed. Experimental results indicate a 70-80% reduction of acetic acid, methoxy phenols, and catechol, and a 55-65% reduction in non-aromatic ketones, BTX, and heterocycles. Alkyl phenols and phenols were least affected, showing a 30-35% reduction. Conditioning of the pyrolysis gas resulted in a 56 % and a 18 wt% increase in water and permanent (dry) gas yield, respectively, and a 29 % loss of condensable carbon. A significant reduction of CO amount (-38 %), and production of H2 (+1063 %) and CO2 (+36 %) over the catalyst was achieved, while there was no or minimal change in light hydrocarbon content. Probing the catalyst after the test, the bulk phase of the catalyst was found to be magnetite (Fe3O4) and the catalyst exhibited significant water gas shift (WGS) reaction activity. The measured gas composition during the test was indicative of no or very limited Fischer-Tropsch (FT) CO /CO2 hydrogenation activity and this infers that also the active surface phase of the catalyst during the test was Fe-oxide, rather than Fe-carbide. The results show that iron-based materials are potential candidates for application in a pyrolysis gas pre-conditioning step before further treatment or use, and a way of generating a hydrogen-enriched gas without the need for bio-crude condensation.

  • 43.
    Haghighi Moud, Pouya
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Andersson, Klas J.
    Lanza, Roberto
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Engvall, Klas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Equilibrium potassium coverage and its effect on a Ni tar reforming catalyst in alkali- and sulfur-laden biomass gasification gases2016In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 190, p. 137-146Article in journal (Refereed)
    Abstract [en]

    Biomass conversion to syngas via gasification produces certain levels of gaseous by-products, such as tar and inorganic impurities (sulfur, potassium, phosphorus etc.). Nickel, a commonly used catalyst for hydrocarbqn steam reforming, suffers reduced reforming activity by small amounts of sulfur (S) or potassium (K), while resistance against deleterious carbon whisker formation increases. Nevertheless, the combined effect of biomass derived gas phase alkali at varying concentrations together with sulfur on tar reforming catalyst performance under realistic steady-state conditions is largely unknown. Prior to this study, a methodology to monitor these effects by precise K dosing as well as K co-dosing with S was successfully developed. A setup consisting of a 5 kW biomass fed atmospheric bubbling fluidized bed gasifier, a high temperature hot gas ceramic filter, and a catalytic reactor operating at 800 degrees C were used in the experiments. Within the current study, two test periods were conducted, including 30 h with 1 ppmv potassium chloride (KCl) dosing followed by 6 h without KCl dosing. Besides an essentially carbon-free operation, it can be concluded that although K, above a certain threshold surface concentration, is known to block active Ni sites and decrease activity in traditional steam reforming, it appears to lower the surface S coverage (theta(s)) at active Ni sites. This reduction in theta(s) increases the conversion of methane and aromatics in tar reforming application, which is most likely related to K-induced softening of the S-Ni bond. The K-modified support surface may also contribute to the significant increase in reactivity towards tar molecules. In addition, previously unknown relevant concentrations of K during realistic operating conditions on typical Ni-based reforming catalysts are extrapolated to lie below 100 mu K/m(2), a conclusion based on the 10-40 mu K/m(2) equilibrium coverages observed for the Ni/MgAl2O4 catalyst in the present study.

  • 44. Hagström, Magnus
    et al.
    Engvall, Klas
    Pettersson, Jan B. C.
    Desorption Kinetics at Atmospheric Pressure: Alkali Metal Ion Emission from Hot Platinum Surfaces2000In: Journal of Physical Chemistry B, Vol. 104, no 18, p. 4457-4462Article in journal (Refereed)
  • 45. Hernandez, Asbel
    et al.
    Andersson, Klas J.
    Topsoe A/S.
    Engvall, Klas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Kantarelis, Efthymios
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology. KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Preferential adsorption of K species and the role of support during reforming of biomass derived producer gas over sulfur passivated Ni/MgAl2O42020In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 34, no 9, p. 11103-11111Article in journal (Refereed)
    Abstract [en]

    Biomass gasification is a sustainable way to convert biomass residues into valuable fuels and chemicals via syngasproduction. However, several gas impurities need to be removed before thefinal synthesis. Understanding of the interactions andeffects of biomass-derived producer gas contaminants (S and K) on the performance of reforming catalysts is of great importancewhen it comes to process reliability and development. In the present study, the steam reforming activity at 800°C of a sulfur-equilibrated nickel catalyst during controlled exposure to alkali species (∼2 ppmv K) and in its absence was investigated using realproducer gas from a 5 kWthO2-blownfluidized-bed gasifier. Conversions of CH4,C2H4, and C10H8were used to evaluate theperformance of the Ni/MgAl2O4catalyst and MgAl2O4support. A significant and positive effect on the catalyst activity is observedwith addition of gas-phase KCl. This is assigned primarily to the observed K-induced reduction in sulfur coverage (θS)onNianeffect which is reversible. The catalytic contribution of the K-modified pure MgAl2O4support was found to be significant in theconversion of naphthalene but not for light hydrocarbons. The product and catalyst analyses provided evidence to elucidate thepreferential adsorption site for S and K on the catalyst as well as the role of the support. Whereas S, as expected, was found topreferentially adsorb on the surface of Ni particles, forming S-Ni sites, K was found to preferentially adsorb on the MgAl2O4support.A low but still significant K adsorption on S−Ni sites, or an effect on only the fraction of exposed Ni surface area near the metal−support interface, can, however, not be excluded. The result suggests that an improved Ni/MgAl2O4catalyst activity and anessentially carbon-free operation can be achieved in the presence of controlled amount of gas-phase potassium and high sulfurcoverages on Ni. Based on the results, a mechanism of the possible K−S interactions is proposed

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  • 46.
    Hohmann, Lea
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Marks, Kess
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Chien, Tzu-En
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Ostrom, Henrik
    Stockholm Univ, Dept Phys, Fysikum, S-10691 Stockholm, Sweden..
    Hansson, Tony
    Stockholm Univ, Dept Phys, Fysikum, S-10691 Stockholm, Sweden..
    Muntwiler, Matthias
    Paul Scherrer Inst, CH-5232 Villigen, Switzerland..
    Engvall, Klas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Göthelid, Mats
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Harding, Dan James
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Process Technology.
    Effect of Coadsorbed Sulfur on the Dehydrogenation of Naphthalene on Ni(111)2023In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 128, no 1, p. 67-76Article in journal (Refereed)
    Abstract [en]

    There are several difficulties when experimentally determined reaction mechanisms are applied from model systems to real catalysis. Besides the infamous pressure and material gaps, it is sometimes necessary to consider impurities in the real reactant feedstock that can act as promoters or catalyst poisons and alter the reaction path. In this study, the effect of sulfur on the dehydrogenation of naphthalene on Ni(111) is investigated by using X-ray photoelectron spectroscopy and scanning tunneling microscopy. Sulfur induces a (5 root 3 x 2) surface reconstruction, as previously reported in the literature. The sulfur does not have a strong effect on the dehydrogenation temperature of naphthalene. However, the presence of sulfur leads to a preferred formation of carbidic over graphitic carbon and a strong inhibition of carbon diffusion into the nickel bulk, which is one of the steps of destructive whisker carbon formation described in the catalysis literature.

  • 47. Holmlid, Leif
    et al.
    Engvall, Klas
    Aman, Carina
    Menon, P. Govind
    A new approach to loss of alkali promoter from industrial catalysts: Importance of excited states of alkali1993In: Studies in Surface Science and Catalysis, Vol. 75, no C, p. 795-807Article in journal (Refereed)
  • 48. Kotarba, Andrzej
    et al.
    Engvall, Klas
    Pettersson, Jan B. C.
    Svanberg, Marcus
    Holmlid, Leif
    Angular resolved neutral desorption of potassium promoter from surfaces of iron catalysts1995In: Surface Science, Vol. 342, no 1-3, p. 327-340Article in journal (Refereed)
  • 49. Kotarba, Andrzej
    et al.
    Hagström, Magnus
    Engvall, Klas
    Pettersson, Jan B. C.
    High pressure desorption of K+ from iron ammonia catalyst migration of the promoter towards Fe active planes2004In: Catalysis Letters, Vol. 95, no 1-2, p. 93-97Article in journal (Refereed)
  • 50. Kotarba, Andrzej
    et al.
    Hagström, Magnus
    Engvall, Klas
    Pettersson, Jan B. C.
    In situ characterization of an iron catalyst by potassium ion desorption and electron emission measurements1998In: Reaction Kinetics and Catalysis Letters, Vol. 63, no 2, p. 219-224Article in journal (Refereed)
123 1 - 50 of 108
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