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  • 1. Chen, Wenhua
    et al.
    Lu, Hua
    Pradier, Claire-Marie
    Paul, Jan
    Flodström, Anders
    Reduction of NO by C4 hydrocarbons on platinum in the presence of oxygen: influence of sulfur dioxide1997In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 172, no 1, p. 3-12Article in journal (Refereed)
    Abstract [en]

    The reduction of NO, in the presence of i-C4H10or i-C4H8and O2, catalyzed by a platinum foil, was studied in order to understand better the catalytic activity of platinum metal, free of any support or dispersion effects. The reaction products were analyzed by mass spectrometry, and the surface was characterized by X-ray photoelectron spectroscopy at different stages of the reaction. A correlation between the catalytic activity for NO conversion and the presence of adsorbed intermediates is demonstrated. The role of oxygen is interpreted as twofold: formation of active intermediates and deactivation of the surface. The effect of traces of sulfur dioxide in the reacting phase on the reduction of NO by isobutene was investigated. The influence of SO2is very much dependent upon its initial concentration in the gas phase. Low concentrations (<15 ppm) promote the reduction of NO, whereas higher levels poison the reaction by a surface site blocking effect.

  • 2.
    Creaser, Derek
    et al.
    Luleå University of Technology.
    Andersson, B.
    Chalmers University of Technology, Department of Chemical Reaction Engineering.
    Hudgins, R.R.
    Department of Chemical Engineering, University of Waterloo.
    Silveston, P.L.
    Department of Chemical Engineering, University of Waterloo.
    Transient kinetic analysis of the oxidative dehydrogenation of propane1999In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 182, no 1, p. 264-269Article in journal (Refereed)
    Abstract [en]

    Oxidative dehydrogenation of propane was studied using various transient techniques. Results support a redox mechanism in which propane reduces the catalyst, which is reoxidized by gas-phase oxygen. Only lattice oxygen participates in propene formation. Desorbable oxygen is a major source of poor selectivity, although lattice oxygen also causes total oxidation. Consequently, propene selectivity in the absence of gas-phase O2is superior to co-feed, steady-state selectivity at the same propane conversion. Propene selectivity is further improved by increasing the degree of catalyst reduction.

  • 3.
    Hedlund, Jonas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Zhou, Ming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Faisal, Abrar
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Öhrman, Olov G.W.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. RISE Energy Technology Center, Box 726, 941 28, Piteå, Sweden.
    Finelli, Valeria
    Department of Chemistry, NIS and INSTM Reference Centre, Università di Torino, Via G. Quarello 15, I-10135 and Via P. Giuria 7, I-10125, Torino, Italy.
    Signorile, Matteo
    Department of Chemistry, NIS and INSTM Reference Centre, Università di Torino, Via G. Quarello 15, I-10135 and Via P. Giuria 7, I-10125, Torino, Italy.
    Crocellà, Valentina
    Department of Chemistry, NIS and INSTM Reference Centre, Università di Torino, Via G. Quarello 15, I-10135 and Via P. Giuria 7, I-10125, Torino, Italy.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Controlling diffusion resistance, selectivity and deactivation of ZSM-5 catalysts by crystal thickness and defects2022In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 410, p. 320-332Article in journal (Refereed)
    Abstract [en]

    A systematic investigation of two sets of defect free and defective ZSM-5 crystals with controlled thickness (T) between 30 and 400 nm and of their performances in methanol conversion was reported for the first time in the present work. The defect free ZSM-5 crystals with a thickness of 35 nm are by far the smallest ever reported and displayed superior activity, stability and selectivity to slower diffusing compounds, which resulted in high yield of e.g. gasoline and the 1,2,4-trimethylbenzene isomer with high octane number, as compared to the other studied catalysts. Almost only products forming in the zeolite pores were detected and consequently, the external surface must be nearly inactive. Strong correlations between T and deactivation rate were observed. Thick crystals deactivated much faster than thin crystals, probably due to formation of carbon species in the zeolite pores, which results in pronounced percolation effects and faster deactivation of the former. At comparable thickness, crystals with defects deactivated much faster than defect free crystals, due to formation of additional small molecular coke species in the former. Strong correlations between T and selectivity were also observed and assigned to control of diffusion resistance by crystal thickness.

  • 4.
    Khasevani, Sepideh G.
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Nikjoo, Dariush
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Ojwang, Dickson O.
    Department of Chemistry – Ångström Laboratory, Uppsala University, Box 538, SE-751 21, Uppsala, Sweden.
    Nodari, Luca
    Dipartimento di Scienze Chimiche, Università degli Studi di Padova, 35131 Padova, Italy; Istituto di Chimica della Materia Condensata e di Tecnologie per l’Energia, ICMATE-CNR, 35127 Padova, Italy.
    Sarmad, Shokat
    Technical Chemistry, Department of Chemistry, Chemical-Biological Centre, Umeå University, SE-90871 Umeå, Sweden.
    Mikkola, Jyri-Pekka
    Technical Chemistry, Department of Chemistry, Chemical-Biological Centre, Umeå University, SE-90871 Umeå, Sweden; Industrial Chemistry & Reaction Engineering, John Gadolin Process Chemistry Centre, Åbo Akademi University, Biskopsgatan 8, Fl-20500 Åbo-Turku, Finland.
    Rigoni, Federica
    Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, 30170 Venezia-Mestre, Italy.
    Concina, Isabella
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    The beauty of being complex: Prussian blue analogues as selective catalysts and photocatalysts in the degradation of ciprofloxacin2022In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 410, p. 307-319Article in journal (Refereed)
    Abstract [en]

    We investigate the performance of four Prussian blue analogues (PBAs) as catalysts for the selective degradation of ciprofloxacin in water, under both dark and illumination conditions. We show that no light is actually needed to induce a selective degradation of the molecular target, while light irradiation spurs the process, without, however, resulting in the commonly reported photolysis-supported breaking down. We present a systematic characterization of the PBAs aiming at interpreting the catalytic outcomes in the light of a classic coordination chemistry analysis, empowered by the most recent findings in literature. We show that varying the transition metal binding the N atom of the cyanide bridge is key to promote photoinduced charge generation and transfer, which effectively disrupts the molecular target. The analysis of the materials before and after the irradiation with solar simulated light results in a change of the lattice parameters, indicating the possibility of a light-induced spin cross-over.

  • 5. Paul, Jan
    et al.
    Rosén, A.
    Cluster calculations of intermediate states in the catalyzed conversion of CH3OH to CH2O on a Cu(100) surface1983In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 84, no 2, p. 288-296Article in journal (Refereed)
    Abstract [en]

    The Hartree-Fock-Slater (HFS) calculations of a CH3OCu5 cluster symbolizing methoxide bound to a Cu(100) surface are presented. Adsorption geometry, molecular orbitals, and symmetry properties of the CH3O group in terms of one-electron energies, charge distributions, and partial densities of states (PDOS) are discussed. A comparison of calculated ionization energies and measured binding energies supports the occupation by methoxide of the hollow adsorption site. The electron distribution of the hydrogen atoms has been analyzed for different geometries and is shown to be a sensitive probe of the oxidation from methoxide (CH3O)/methyl (CH3) to formaldehyde (CH2O)/methylene (CH2).

  • 6.
    Perdana, Indra
    et al.
    Chalmers University of Technology, Department of Chemical Engineering and Environmental Science.
    Creaser, Derek
    Chalmers University of Technology, Department of Chemical Engineering and Environmental Science.
    Öhrman, Olov
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    NOx adsorption over a wide temperature range on Na-ZSM-5 films2005In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 234, no 1, p. 219-229Article in journal (Refereed)
    Abstract [en]

    NOx adsorption over a wide temperature range (30–350 °C) on monolith supported Na-ZSM-5 films were studied with a gas flow reactor. The nature of the adsorbed species was further investigated by in situ infrared spectroscopy. Depending on the adsorption temperature, three different ranges of thermally stable species were observed on Na-ZSM-5 films. In addition to the role of cationic sites and residual hydroxyl groups in zeolite frameworks, it was found that the formation of nitric acid plays an important role in NO2 adsorption. Nitrate species were formed during adsorption by two mechanisms. The nitrates formed via nitric acid and involving NO formation had lower thermal stability than those formed through an NO2 disproportionation reaction

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