| 1. |
- Abdelaziz, Omar Y., et al.
(författare)
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Oxidative Depolymerisation of Lignosulphonate Lignin into Low-Molecular-Weight Products with Cu–Mn/δ-Al2O3
- 2019
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Ingår i: Topics in Catalysis. - : Springer Science and Business Media LLC. - 1022-5528 .- 1572-9028. ; 62, s. 639-648
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Tidskriftsartikel (refereegranskat)abstract
- Lignin depolymerisation receives great attention due to the pressing need to find sustainable alternatives to fossil sources for production of fuels and chemicals. In this study, alumina-supported Cu–Mn and Ni–Mo catalysts were tested for oxidative depolymerisation of a technical lignin stream—sodium lignosulphonates—to produce valuable low-molecular-weight aromatics that may be considered for applications in the fuels and chemicals sector. The reactions were performed at elevated temperature and oxygen pressure, and the product mixtures were analysed by size exclusion chromatography, two-dimensional nuclear magnetic resonance spectroscopy and supercritical fluid chromatography mass spectrometry. The best performance was obtained with Cu–Mn/δ-Al 2 O 3 , which was thoroughly characterised before and after use by nitrogen physisorption, scanning electron microscopy, energy dispersive spectroscopy, powder X-ray diffraction, thermal gravimetric analysis, inductively coupled plasma optical emission spectrometry and X-ray photoelectron spectroscopy. Major products identified were vanillin, p-hydroxybenzaldehyde, vanillic acid and p-hydroxybenzoic acid as well as smaller aliphatic aldehydes, acids and lactones.
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| 2. |
- Abdulhamid, Hussam, 1974, et al.
(författare)
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Influence of the type of reducing agent (H2, CO, C3H6 and C3H8) on the reduction of stored NOX in a Pt/BaO/Al2O3 model catalyst
- 2004
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Ingår i: Topics in Catalysis. - 1572-9028 .- 1022-5528. ; 30-31:1-4, s. 161-168
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Tidskriftsartikel (refereegranskat)abstract
- In this investigation, a comparative study for a NOx storage catalytic system was performed focusing on the parameters that affect the reduction by using different reductants (H2, CO, C3H6 and C3H8) and different temperatures (350, 250 and 150 degrees C), for a Pt/BaO/Al2O3 catalyst. Transient experiments show that H2 and CO are highly efficient reductants compared to C3H6 which is somewhat less efficient. H2 shows a significant reduction effect at relatively low temperature (150 degrees C) but with a low storage capacity. We find that C3H8 does not show any NOx reduction ability for NOx stored in Pt/BaO/Al2O3 at any of the temperatures. The formation of ammonia and nitrous oxide is also discussed.
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| 3. |
- Adams, Emma, 1989, et al.
(författare)
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Passive SCR: The effect of H2 to NO ratio on the formation of NH3 over alumina supported platinum and palladium catalysts
- 2016
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Ingår i: Topics in Catalysis. - : Springer Science and Business Media LLC. - 1572-9028 .- 1022-5528. ; 59:10-12, s. 970-975
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the relationship between the H2:NO ratio and NH3 formation over alumina supported Pt and Pd catalysts. By kinetic studies and in situ infrared spectroscopy, we report that NH3 formation is not only sensitive to the catalyst formulation but equally dependent on the feed gas composition and tem- perature. Specifically, we identify that hydrogen plays an important role in the dissociation of NO at low tem- perature. We also show that the support material itself plays a vital role in the ammonia formation mechanism due to the redox behaviour of NO adsorption at low temperature. This was unexpected as the noble metal is generally considered to be the active phase for the reaction of NO and H2.
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| 4. |
- Albertazzi, Simone, et al.
(författare)
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Deactivation of a Ni-Based Reforming Catalyst During the Upgrading of the Producer Gas, from Simulated to Real Conditions
- 2011
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Ingår i: Topics in catalysis. - : Springer Science and Business Media LLC. - 1022-5528 .- 1572-9028. ; 54:10, s. 746-754
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Tidskriftsartikel (refereegranskat)abstract
- The deactivation of a nickel reforming catalyst during the upgrading of the producer gas obtained by gasification of lignocellulosic biomass was studied. The research involved several steps: the selective deactivation of the catalyst in a laboratory scale; the streaming of the catalyst with the producer gas of a downdraft and an oxygen/steam circulating fluidized bed (CFB) gasifier; and tests in a reformer placed in a slipstream of the CFB gasifier. The information obtained allowed to elucidate the catalyst deactivation mechanisms taking place during the reforming of the producer gas: physical deactivation by deposition of fine ashes, aerosol particulate or carbon; poisoning by H2S and HCl present in the gas phase and thermal sintering because of the high operation temperatures required to avoid the chemical deactivation. These physical and chemical effects depended on the composition of the biomass fuel.
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| 5. |
- Andersson, Mike, et al.
(författare)
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Investigations on the possibilities of a MISiCFET sensor system for OBD and combustion control utilizing different catalytic gate materials
- 2004
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Ingår i: Topics in catalysis. - 1022-5528 .- 1572-9028. ; 30-31:1, s. 365-368
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Tidskriftsartikel (refereegranskat)abstract
- Different catalytic materials, like Pt and Ir, applied as gate contacts on metal insulator silicon carbide field effect transistors — MISiCFET—facilitate the manufacture of gas sensor devices with differences in selectivity, devices which due to the chemical stability and wide band gap of SiC are suitable for high temperature applications. The combination of such devices in a sensor system, utilizing multivariate analysis/modeling, have been tested and some promising results in respect of monitoring a few typical exhaust and flue gas constituents, in the future aiming at on board diagnostics (OBD) and combustion control, have been obtained.
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| 6. |
- Andonova, Stanislava, 1977, et al.
(författare)
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Enhanced Low Temperature NOx Reduction Performance Over Bimetallic Pt/Rh-BaO Lean NOx Trap Catalysts
- 2013
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Ingår i: Topics in Catalysis. - : Springer Science and Business Media LLC. - 1572-9028 .- 1022-5528. ; 56:1-8, s. 68-74
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Tidskriftsartikel (refereegranskat)abstract
- The overall NSR operation was tested over a bimetallic Pt/Rh-BaO lean NO (x) trap (LNT) catalyst in the range of 473-673 K with simulated diesel exhausts and compared to monometallic 1 wt% Pt/BaO/gamma-Al2O3 and 0.5 wt% Rh/BaO/gamma-Al2O3 samples. The results showed the beneficial effect of the simultaneous presence of 0.5 wt% Pt and 0.25 wt% Rh on the catalytic performance under lean-burn conditions at low temperatures. It was observed that both Pt/BaO/gamma-Al2O3 and Rh/BaO/gamma-Al2O3, which both were mildly aged, have limited NO (x) reduction capacity at 473 K. However, combining Pt and Rh in the NO (x) storage catalyst assisted the NO (x) reduction process to occur at lower temperatures (473 K). One possible reason could be that the combined Pt and Rh sample was more resistant to aging. In addition, the NO2-TPD data showed that the presence of Rh into the Pt/BaO/gamma-Al2O3 system has a considerable effect on the spill-over process of NO (x) , accelerating the release of NO (x) at lower temperatures. These results were in a good agreement with the observed higher rate of oxygen release of the bimetallic Pt/Rh catalyst, leaving a significant number of noble metal sites available for adsorption at lower temperatures than that of the monometallic Pt sample. The superior NSR performance of the bimetallic Pt/Rh/BaO/gamma-Al2O3 catalyst under lean-burn conditions suggested the existence of synergetic promotion effect between the Pt and Rh components, increasing the NO (x) reduction efficiency in comparison with that of the monometallic Pt and Rh-BaO LNT catalysts.
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| 7. |
- Barrientos, Javier, et al.
(författare)
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Deactivation of Ni/gamma-Al2O3 Catalysts in CO Methanation : Effect of Zr, Mg, Ba and Ca Oxide Promoters
- 2017
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Ingår i: Topics in catalysis. - : Springer. - 1022-5528 .- 1572-9028. ; 60:17-18, s. 1276-1284
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Tidskriftsartikel (refereegranskat)abstract
- Catalyst deactivation is one of the major concerns in the production of substitute natural gas (SNG) via CO methanation. Catalysts in this application need to be active at low temperatures, resistant to polymeric carbon formation and stable at high temperatures and steam partial pressures. In the present work, a series of alumina-supported nickel catalysts promoted with Zr, Mg, Ba or Ca oxides were investigated. The catalysts were tested under low temperature CO methanation conditions in order to evaluate their resistance to carbon formation. The catalysts were also exposed to accelerated ageing conditions at high temperatures in order to study their thermal stability. The aged catalysts lost most of their activity mainly due to sintering of the support and the nickel crystallites. Apparently, none of these promoters had a satisfactory effect on the thermal resistance of the catalyst. Nevertheless, it was found that the presence of Zr can reduce the rate of polymeric carbon formation.
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| 8. |
- Barrientos, Javier, et al.
(författare)
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Fischer-Tropsch Synthesis Over Zr-Promoted Co/gamma-Al2O3 Catalysts
- 2017
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Ingår i: Topics in catalysis. - : SPRINGER/PLENUM PUBLISHERS. - 1022-5528 .- 1572-9028. ; 60:17-18, s. 1285-1298
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Tidskriftsartikel (refereegranskat)abstract
- Two Zr-modified alumina supports were synthetized containing the same amount of Zr but a different distribution of this modifier over the alumina surface. These supports, together with the unmodified alumina carrier, were used to prepare three cobalt-based catalysts which were characterized and tested under relevant Fischer-Tropsch conditions. The three catalysts presented very similar porosity and cobalt dispersion. The addition of Zr nor its distribution enhanced the catalyst reducibility. The catalyst activity was superior when using a carrier consisting of large ZrO2 islands over the alumina surface. The use of a carrier with a homogeneous Zr distribution had however, a detrimental effect. Moreover, a faster initial deactivation rate was observed for the Zr-promoted catalysts, fact that may explain this contradictory effect of Zr on activity. Finally, the addition of Zr showed a clear enhancement of the selectivity to long chain hydrocarbons and ethylene, especially when Zr was well dispersed.
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| 9. |
- Becker, Elin, 1981, et al.
(författare)
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Methane oxidation over alumina and ceria supported platinum
- 2009
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Ingår i: Topics in Catalysis. - : Springer Science and Business Media LLC. - 1572-9028 .- 1022-5528. ; 52:13-20, s. 1957-1961
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Tidskriftsartikel (refereegranskat)abstract
- Oxidation of methane over Pt/Al(2)O(3) and Pt/CeO(2) catalysts was studied by transient gas-flow reactor and in situ FTIR spectroscopy experiments. The Pt/CeO(2) catalyst is generally more active, indicating more efficient CH(4) dissociation, especially during oxygen pulsing, which likely is connected to the higher oxygen storage capacity/mobility of ceria.
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| 10. |
- 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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