| 1. |
- Aad, G, et al.
(författare)
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- 2015
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swepub:Mat__t
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| 2. |
- Kirilin, Alexey V., et al.
(författare)
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Aqueous-phase reforming of xylitol over Pt/C and Pt/TiC-CDC catalysts : catalyst characterization and catalytic performance
- 2014
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Ingår i: Catalysis Science & Technology. - : RSC Publishing. - 2044-4753. ; 4:2, s. 387-401
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Tidskriftsartikel (refereegranskat)abstract
- The aqueous phase reforming (APR) of xylitol was studied over five Pt/C catalysts. The correlation between physico-chemical properties of the catalysts and catalytic performance was established. The Pt/C catalysts have different textural properties as well as different mean Pt cluster sizes and surface acidity. The average Pt cluster size was investigated by means of CO chemisorption as well as by TEM. The reaction was found to be structure sensitive and TOF linearly increases with increasing average Pt cluster size in the studied domain. The catalysts which possess higher surface acidity favoured higher rates of hydrocarbon production. On the contrary the Pt/C materials with lower acidities generated hydrogen with high selectivity and TOF.
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| 3. |
- Arve, Kalle, et al.
(författare)
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Did Chemisorption Become an Obsolete Method With Advent of Tem? Comparison of Mean Particle Size and Distribution of Silver on Alumina
- 2011
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Ingår i: Catalysis Letters. - : Springer Science and Business Media LLC. - 1572-879X .- 1011-372X. ; 141:5, s. 665-669
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Tidskriftsartikel (refereegranskat)abstract
- Silver particle size and dispersion on a Ag/Al2O3 for HC-SCR were examined by means of chemisorption and TEM. Experimental results showed that determination of the accurate mean particle size (mps) is challenging and that the both applied methods have specific characteristics increasing the inaccuracy in the results which has to be taken into account in evaluation of catalytic activity. The results from TEM imaging were found to depend highly on the mode in which the surface was scanned (bright field versus dark field). Generally the point resolution was higher in dark field but the obtained mps did not increased along with the increasing silver loading. The main limitation with the O-2-chemisorption was related to the choice of the stoichiometric factor between the adsorbent and silver atoms. However, together these techniques support each other and help to give a more realistic picture of the mean silver particle size, distribution and indications of the oxidation states on the alumina support.
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| 4. |
- Behravesh, Erfan, et al.
(författare)
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Synthesis and characterization of Au nano particles supported catalysts for partial oxidation of ethanol : Influence of solution pH, Au nanoparticle size, support structure and acidity
- 2017
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Ingår i: Journal of Catalysis. - : Elsevier. - 0021-9517 .- 1090-2694. ; 353, s. 223-238
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Tidskriftsartikel (refereegranskat)abstract
- Partial oxidation of ethanol to acetaldehyde was carried out over gold catalysts supported on various oxides and zeolites by deposition precipitation. The special focus of this work was on the influence of H-Y zeolite surface charge on Au cluster size and loading linking it to activity and selectivity in ethanol oxidation and comparing with other studied catalysts. The catalysts were characterized by nitrogen physisorption, transmission electron microscopy (TEM), scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDXA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and zeta potential measurements. pH of the solution governed the Au NPs size within the range of 5.8–13.2 nm with less negatively charged surfaces leading to formation of smaller clusters. Au loading on H-Y zeolite with silica to alumina ratio of 80 was increased by raising the pH. In fact, H-Y-12 and H-Beta-25 were selective towards diethyl ether while acetaldehyde was the prevalent product on less acidic H-Y-80. The results demonstrated strong dependency of the catalytic activity on the Au cluster size. Namely turn over frequency (TOF) decreased with an increase in metal size from 6.3 to 9.3 nm on H-Y-80. Selectivity towards acetaldehyde and ethyl acetate did not change significantly on H-Y-80 within 6.3–9.3 nm Au particle size range. On Al2O3 support, however, selectivity towards acetaldehyde increased considerably upon diminishing Au average particle size from 3.7 to 2.1 nm.
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| 5. |
- Bernas, Andreas, et al.
(författare)
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Catalytic transformation of abietic acid to hydrocarbons
- 2012
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Ingår i: Topics in catalysis. - : Springer Science and Business Media LLC. - 1022-5528 .- 1572-9028. ; 55:7-10, s. 673-679
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Tidskriftsartikel (refereegranskat)abstract
- Catalytic and thermal conversion of abietic acid was investigated in a laboratory scale high-pressure autoclave. Fractionation of crude tall oil produces rosin acids of which abietic acid is the main compound. Tall oil rosin acid, a forest product industry residue, is an abundant, inexpensive and chemically desirable feedstock for production of lighter hydrocarbons that can be used as diesel fuel additives. The carboxylic acid functionality of the main reactant, abietic acid, must first be removed, followed by double bond hydrogenation of the remaining aromatic rings. In this study, a number of catalytic and non-catalytic reaction steps in the conversion of abietic acid were investigated. The aim was to study hydrogenation and decarboxylation reactions of abietic acid in order to produce lighter hydrocarbons. The experiments were performed by using toluene as a solvent as well as with neat abietic acid, in the absence of any solvent. Hydrogenation of abietic acid to tetrahydroabietic acid in toluene was successfully performed over palladium on carbon catalyst at the temperature range of 100-200 A degrees C and at 30 bar hydrogen pressure. Thermal non-catalytic decarboxylation of abietic acid in toluene takes place at 200-300 A degrees C resulting in one main product. The hydrocarbon products were further hydrogenated under hydrogen pressure. Catalytic decarboxylation of abietic acid in toluene was achieved over 5 wt% Ru/C, giving a wider product distribution than thermal decarboxylation.
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| 6. |
- Birgersson, Henrik, et al.
(författare)
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An investigation of a new regeneration method of commercial aged three-way catalysts
- 2006
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Ingår i: Applied Catalysis B. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 65, s. 93-100
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Tidskriftsartikel (refereegranskat)abstract
- The ability to modify aged three-way catalysts (TWC) by regaining part of the fresh catalyst surface structure has been verified by both bulk and surface-sensitive characterisation techniques. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM/EDX) techniques were applied to fully evaluate the efficiency of a regeneration procedure of commercial three-way catalysts targeting the washcoat surface. The regeneration comprised combined thermal and liquid chlorine treatments. Structural changes of the washcoat were further investigated with nitrogen adsorption-desorption (BET) and Laser Ablation methods. The investigation showed that the regeneration treatments resulted in an enrichment of the washcoat surface with palladium, thereby increasing the number of catalytically active surface sites. Furthermore, the observed removal of phosphorous and sulphur contaminants resulted in an increase of the relative amount of small pores between 1 and 10 nm and washcoat surface area. An increased catalytic activity regarding CO, NOx, and HC emissions was observed after regeneration. providing proof of the proposed concept.
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| 7. |
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| 8. |
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| 9. |
- Eta, Valerie, et al.
(författare)
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Synthesis of dimethyl carbonate from methanol and carbon dioxide : Circumventing thermodynamic limitations
- 2010
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society. - 0888-5885 .- 1520-5045. ; 49:20, s. 9609-17
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis of dimethyl carbonate from methanol and CO2 catalyzed by ZrO2 doped with KCl was investigated using chemical traps for water to circumvent thermodynamic limitations. The reaction, promoted by magnesium, occurred via the formation of carbonated magnesium methoxide (CMM) which adsorbed on the surface of ZrO2. The surface migration of the oxygen atom of ZrO2 to the surface methoxy groups of CMM resulted in the formation of dimethyl carbonate. The resulting MgO then reacted with methanol forming water and regenerating magnesium methoxide. The water formed reacted with the dehydrating agent, thus shifting the equilibrium toward a higher yield of DMC. The yield of 7.2 mol % DMC and 13.6 mol % conversion of methanol was obtained when methanol reacted with CO2 at 150 °C and 9.5 MPa for 8 h. The plausible reaction pathway is described.
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| 10. |
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