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  • 1.
    Grahn, Mattias
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Faisal, Abrar
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. Department of Chemical Engineering, COMSATS University Islamabad, Lahore Campus, Lahore, Pakistan.
    Öhrman, Olov G.W
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik. RISE ETC - Energy Technology Center, SE-941 28 Piteå, Sweden.
    Zhou, Ming
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Signorile, Matteo
    Department of Chemistry, NIS and INSTM Reference Centre, Università di Torino, Torino, Italy.
    Crocellà, Valentina
    Department of Chemistry, NIS and INSTM Reference Centre, Università di Torino, Torino, Italy.
    Nabavi, Mohammad Sadegh
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Small ZSM-5 crystals with low defect density as an effective catalyst for conversion of methanol to hydrocarbons2019Inngår i: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This work presents the synthesis of nearly defect-free ZSM-5 nanosized crystals, prepared in fluoride medium by seeding with silicalite-1. This material was carefully characterized and its catalytic performances in the methanol to hydrocarbons (MTH) reaction were assessed. Such fluoride-based material was compared to a reference ZSM-5, produced through a conventional alkaline synthesis but from the same seeding. Despite both the materials show closely identical morphology and they have a comparable acid site population, the catalyst prepared using the fluoride route showed significantly longer lifetime in MTH compared to the catalyst prepared using conventional synthesis at high pH. The slower deactivation for the samples prepared using the fluoride route was ascribed, thanks to a thorough in situ IR spectroscopy study, to its lower density of internal defects. According to the UV-Raman characterization of coke on the spent catalyst, the fluoride-based ZSM-5 catalyst produces less molecular coke species, most probably because of the absence of enlarged cavities/channels as due to the presence of internal defects. On the basis of these observations, the deactivation mechanism in the ZSM-5 synthesized by fluoride medium could be mostly related to the deposition of an external layer of bulk coke, whereas in the alkali-synthesized catalyst an additional effect from molecular coke accumulating within the porous network accelerates the deactivation process.

  • 2.
    Hegedűs, Péter
    et al.
    Department of General and Inorganic Chemistry, Institute of Chemistry, University of Pannonia, Hungary.
    Szabó-Bárdos, Erzsébet
    Department of General and Inorganic Chemistry, Institute of Chemistry, University of Pannonia, Hungary.
    Horváth, Ottó
    Department of General and Inorganic Chemistry, Institute of Chemistry, University of Pannonia, Hungary.
    Szabó, Péter
    Department of Analytical Chemistry, Institute of Chemistry, University of Pannonia, Hungary.
    Horváth, Krisztián
    Department of Analytical Chemistry, Institute of Chemistry, University of Pannonia, Hungary.
    Investigation of a TiO2 photocatalyst immobilized with poly(vinyl alcohol)2017Inngår i: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 284, s. 179-186Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Immobilization of TiO2 photocatalyst was realized with application of poly(vinyl alcohol) (PVA). However, these PVA-based foils were too instable to be used for photocatalytic water cleaning. Their stability could be significantly enhanced by a thermal treatment, but this procedure generated various water-soluble derivatives such as aldehydes, ketones, and aromatic species. Photocatalytic pre-treatment of the foils proved to be suitable to remove these products from the surface of the composite. After three subsequent pre-treating cycles of irradiation and rinsing, the PVA-TiO2 foil became applicable for photocatalytic degradation of Triton X-100, a widely used non-ionic detergent. The composite catalyst kept its stability and efficiency even after some cycles of re-usage, while its surface underwent a perceptible, although quantitatively negligible degradation.

  • 3.
    Lassinantti, Magdalena
    et al.
    Luleå tekniska universitet.
    Jareman, Fredrik
    Luleå tekniska universitet.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Creaser, Derek
    Luleå tekniska universitet.
    Sterte, Johan
    Preparation and evaluation of thin ZSM-5 membranes synthesized in the absence of organic template molecules2001Inngår i: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 67, nr 1-3, s. 109-119Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Porous α-alumina supports with a pore size of 100 nm were seeded with colloidal TPA-silicalite-1 crystals with a size of 120 nm. The seeded supports were calcined and treated in a synthesis solution free from organic template molecules to form ZSM-5 films on the supports. According to SEM images, the films were about 2 μm thick and no defects could be found on the as-synthesized membranes. Single gas permeation data was collected and good quality membranes (defined as having a non-detectable permeance of SF6 after drying at 100°C) were further evaluated using binary/ternary gas mixtures. The selectivity for n-butane/i-butane had a maximum value of 17.8 at 220°C. Water was selectively separated from a helium-diluted vaporized water/ethanol azeotrope with a maximum selectivity of 12.4.

  • 4. Pradier, C.M.
    et al.
    Chen, W.
    Lu, H.
    Paul, Jan
    NO reduction by isobutene, in the presence of oxygen, on platinum and copper: a comparative study1996Inngår i: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 29, nr 1-4, s. 59-65Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The reaction of NO, oxygen and isobutene was studied under conditions close to stoichiometric, on a platinum and on a copper disk in order to better understand the role of each metal, free of any support and dispersion effects. The products of the reaction were analysed by mass spectrometry and an XPS characterization of the surface was carried out at different stages of the reaction. A correlation between the catalytic activity for NO conversion and the presence of adsorbed intermediates has been clearly demonstrated on platinum. On copper, a redox cycle of the metal is necessary to activate the catalyst. On platinum, oxygen is necessary to initiate the reaction, clean the surface and form reactive intermediates; the reaction is strongly sensitive to oxygen concentration, whereas on copper, oxygen does not directly participate in the reaction mechanism.

  • 5.
    Sjöberg, Erik
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Sandström, Linda
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Membrane processes for effective methanol synthesis in the forest based biorefinery2010Inngår i: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 156, nr 3-4, s. 87-92Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    ZSM-5 membranes were prepared and their performance for methanol separations from synthesis gas was evaluated. The experimentally observed permeances at room temperature for the ZSM-5 membranes were 0.3, 1, 12 and 18 × 10-7 mol m-2 s-1 Pa-1 for H2, CO2, CH3OH and H2O, respectively, which resulted in a separation factor α methanol/H2 of about 30. For a stoichiometric feed, the one pass COx -conversion for a traditional methanol process is about 26% per pass, which requires a recirculation loop with the associated disadvantages. By assuming that the same membrane performance could be obtained at industrial conditions, it was shown by mathematical modeling that a ZSM-5 membrane reactor could reach 97% COx -conversion per pass, while a ZSM-5 membrane module process could reach 81% conversion per pass for a stoichiometric feed. As a result of the high conversion per pass for the membrane processes, one pass design with the associated advantages is possible for these processes. A membrane module based system is preferable over a membrane reactor of practical reasons. However, similar performance to the membrane processes can of course be achieved with a one pass process comprised of a series of methanol reactors, reactor effluent heat exchangers, coolers and condensers

  • 6.
    Stephanidis, S.D.
    et al.
    Chemical Process Engineering Research Institute, CERTH.
    Nitsos, Christos
    Laboratory of General and Inorganic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki.
    Kalogiannis, Konstantions G.
    Chemical Process Engineering Research Institute, CERTH.
    Iliopoulou, Eleni F.
    Chemical Process Engineering Research Institute, CERTH.
    Lappas, Angelos A
    Chemical Process and Energy Resources Institute, Centre for Research and Technology-Hellas (CPERI/CERTH), 57001 Thessaloniki, Greece, Chemical Process Engineering Research Institute, CERTH.
    Triantafyllidis, Kostas
    Laboratory of General and Inorganic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, Chemical Process and Energy Resources Institute, Centre for Research and Technology-Hellas (CPERI/CERTH), 57001 Thessaloniki, Greece.
    Catalytic upgrading of lignocellulosic biomass pyrolysis vapours: Effect of hydrothermal pre-treatment of biomass2011Inngår i: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 167, nr 1, s. 37-45Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The main objective of the present work was the study of the effect of hydrothermal pretreatment of lignocellulosic biomass (beech wood) on the product yields and bio-oil composition produced from biomass flash pyrolysis as well as from the catalytic upgrading of the biomass pyrolysis vapours. The hydrothermal pretreatment of lignocellulosic biomass was performed at a severity factor (Ro) of 3.55 leading to ∼35 wt.% loss of solids, mainly due to solubilization and removal of hemicellulose. The production of sugars (mainly levoglucosan) was significantly increased by the use of the hydrothermally pretreated biomass instead of the untreated biomass in the non-catalytic flash pyrolysis experiments. On the other hand, the concentration of carboxylic acids, ketones and phenols was decreased in the bio-oil derived from the pretreated biomass. The catalysts tested in the upgrading of the biomass pyrolysis vapours were the strongly acidic zeolites H-ZSM-5 and silicalite (with very low number of acid sites) and the mildly acidic mesoporous aluminosilicate Al-MCM-41. The effect of catalysts on product yields and composition of bio-oil in the upgrading of pyrolysis vapours, was similar for both the pretreated and untreated biomass. The use of zeolite H-ZSM-5 decreased the total liquid yield (bio-oil) via decreasing the organic phase of bio-oil and increasing its water content, accompanied by increase of gases and moderate formation of coke on the catalyst. The zeolite silicalite and the Al-MCM-41 induced similar effects with those of H-ZSM-5 but to a less extent, except of the significantly higher coke that was deposited on Al-MCM-41. With regard to the composition of the bio-oil, all the catalysts and mostly the strongly acidic H-ZSM-5 zeolite reduced the oxygen content of the organic fraction, mainly by decreasing the concentration of acids, ketones and phenols in the untreated biomass pyrolysis oil or the concentration of sugars in the pretreated biomass pyrolysis oil. Aromatics and polycyclic aromatic hydrocarbons (PAHs) were significantly increased by the use of all catalysts, for both types of biomass feed. A substantial increase in the concentration of phenols was observed in the upgraded bio-oil derived by the hydrothermally pretreated biomass, using the less acidic silicalite and Al-MCM-41 catalysts

  • 7. Sterte, Johan
    Hydrothermal treatment of hydroxycation precursor solutions1988Inngår i: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 2, nr 2-3, s. 219-231Artikkel i tidsskrift (Fagfellevurdert)
  • 8. Sterte, Johan
    et al.
    Hedlund, Jonas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Industriell miljö- och processteknik.
    Creaser, Derek
    Luleå tekniska universitet.
    Öhrman, Olov
    Wang, Zheng
    Luleå tekniska universitet.
    Lassinantti, Magdalena
    Li, Quinghua
    Luleå tekniska universitet.
    Jareman, Fredrik
    Luleå tekniska universitet.
    Application of the seed-film method for the preparation of structured molecular sieve catalysts2001Inngår i: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 69, nr 1-4, s. 323-329Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The seed-film method has been applied for the preparation of various materials of potential interest as structured molecular sieve catalysts. The method has proven to be very flexible and allows for the reproducible preparation of a number of molecular sieve–substrate combinations as well as the control of the materials’ properties of importance in catalytic applications such as zeolite loading, film thickness, film density and crystal orientation. The preparation of thin molecular sieve films on ceramic foams, α-alumina pellets and porous alumina supports as well as various metal surfaces is described. The preparation of zoned coatings with a compositional gradient is also discussed.

  • 9.
    Szabo, Peter
    et al.
    Department of Analytical Chemistry, University of Pannonia.
    Zsirka, Balázs
    Institute of Environmental Engineering, University of Pannonia.
    Fertig, Dávid
    Department of Analytical Chemistry, University of Pannonia.
    Horváth, Erzsébet
    Institute of Environmental Engineering, University of Pannonia.
    Csizmadia, Tamás
    Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University.
    Kristóf, János
    Institute of Environmental Engineering, University of Pannonia.
    Delaminated kaolinites as potential photocatalysts: Tracking degradation of Na-benzenesulfonate test compound adsorbed on the dry surface of kaolinite nanostructures2017Inngår i: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 287, nr Supplement C, s. 37-44Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract Based on their bandgap values, kaolins can have semiconductive and photocatalytic properties enabling them to use as potential photocatalysts. Kaolinite nanostructures (Knano) and silver-coated kaolinite nanohybrids (Knano(Ag)) were made of ordered (Hinkley Index, HI=1.4) and disordered (HI=0.3) kaolins via intercalation/deintercalation. The book-type kaolin built up from tetrahedral(T)-octahedral(O) double layers has very low photocatalytic activity. At the same time the nanostructures made of individual TO layers show photochemical activity in spite of the fact that their bandgap values are comparable to those of the book-type ones. The presence of Ag on the surface significantly reduced the bandgap and shifted the excitation wavelength towards the visible range. This phenomenon supports the supposition that kaolinite has some semiconductive character. This work presents the connection between photocatalytic activity and morphology for the first time. The surface activity of kaolinite nanostructures and their Ag-hybrids was studied through the decomposition of sodium-benzenesulfonate (BS) test compound with attenuated total reflection Fourier transform infrared spectroscopy (FT-IR/ATR). BS decomposition can be detected on the Knano surface but with low efficiency. The presence of silver can significantly improve the mineralization efficiency. No correlation was found between the activity and the quantity of Ti and Fe contaminants and the amount of Ag on the surface. However, the activity could be correlated with the order-dependent morphology (mixture of semi-hexagonal and nanoscroll-type structures), the pore size and with the increase of the surface coverage.

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