| 1. |
- Chaoquan, Hu, 1981, et al.
(författare)
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Activity of Pd/C for hydrogen generation in aqueous formic acid solution
- 2014
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Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199. ; 39:1, s. 381-390
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Tidskriftsartikel (refereegranskat)abstract
- A commercial Pd/C catalyst was found to exhibit high activity for formic acid (HCOOH) decomposition into CO2 and H2 in aqueous solution at near ambient temperatures. The performance of the catalyst toward HCOOH decomposition in aqueous solution was investigated in a batch reactor at temperatures between 21 and 60 C and HCOOH concentrations between 1.33 and 5.33 M. The apparent activation energy of the overall reaction for the production of H2 from aqueous HCOOH was determined to be 53.7 kJ/mol on the heterogeneous Pd/C catalyst. This is in good agreement with the previously reported theoretical energy barrier (∼52 kJ/mol) for H2 evolution on a Pd surface. Under the present experimental conditions, the catalyst lost activity continuously over time and the apparent deactivation energy was estimated to be 39.2 kJ/mol. Furthermore, the deactivated and spent catalyst was studied by temperature-programmed desorption experiments to reveal the possible species that caused the loss of the activity. Combining the results of our previous DFT calculations and the present experimental results, elementary steps of HCOOH decomposition on Pd in aqueous solution were proposed and discussed. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
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| 2. |
- Chaoquan, Hu, 1981, et al.
(författare)
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Catalytic hydrogenation of C=C and C=O in unsaturated fatty acid methyl esters
- 2014
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Ingår i: Catalysis Science and Technology. - : Royal Society of Chemistry (RSC). - 2044-4753 .- 2044-4761. ; 4:8, s. 2427-2444
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Forskningsöversikt (refereegranskat)abstract
- Biodiesel derived from edible and non-edible oils has received much attention as a chemical feedstock or as a raw fuel alternative to the traditional diesel due to its renewability and biodegradability. However, the crude biodiesel containing large amounts of polyunsaturated fatty acid methyl esters (FAMEs) is susceptible to oxidation upon exposure to heat, light, and oxygen. Catalytic hydro-genation of biodiesel has been considered as a feasible and powerful technique to improve the oxidative stability of biodiesel and hence to provide stable raw materials for industrial applications. The catalytic hydrogenation of FAMEs is a complex process but basically consists of hydrogenation of C=C or C=O, depending on the desirable properties of final products. In this review, we summarize recent developments in hydrogenation of C=C and C=O in FAMEs with focus on catalysts, reaction mechanisms, and reactor conditions. The features of hydrogenation of FAMEs are generalized and the opportunities for future research in the field are outlined.
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| 3. |
- Chaoquan, Hu, 1981, et al.
(författare)
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Methyl crotonate hydrogenation over Pt: Effects of support and metal dispersion
- 2016
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Ingår i: Applied Catalysis A: General. - : Elsevier BV. - 1873-3875 .- 0926-860X. ; 511, s. 106-116
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Tidskriftsartikel (refereegranskat)abstract
- Gas-phase hydrogenation of methyl crotonate (MC) has been studied over Pt supported on Al2O3, C, SiO2,and TiO2. The physicochemical properties of the catalysts were characterized by use of N2 physisorption,transmission electron microscopy and CO chemisorption. The effects of Pt dispersion and nature of the support on the catalytic properties of the catalysts were determined by measurements of the kinetic parameters for MC hydrogenation. The results clearly display MC inhibition effects on the hydrogenation over the catalysts. However, the degree of MC-inhibition is found to depend on both the Pt dispersion and the support used. For alumina a high Pt dispersion can promote the resistance of the catalyst against MC-inhibition, and even allow hydrogen adsorption to become equilibrated on the Pt surface. Compared to SiO2 and C supports, Al2O3 improves the resistance of the Pt surface against MC inhibition, whereas TiO2reduces the resistance. Possible reasons are suggested to understand the positive effect of Al2O3 on Pt against MC inhibition.
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| 4. |
- Chaoquan, Hu, 1981, et al.
(författare)
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Selectivity and kinetics of methyl crotonate hydrogenation over Pt/Al2O3
- 2015
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Ingår i: Catalysis Science and Technology. - 2044-4753 .- 2044-4761. ; 5:3, s. 1716-1730
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Tidskriftsartikel (refereegranskat)abstract
- The hydrogenation of gas-phase methyl crotonate (MC) over Pt/Al2O3 was investigated with the aim to understand C=C hydrogenation in unsaturated methyl esters. Three Pt/Al2O3 catalysts with different Pt dispersions were prepared by varying calcination temperature and evaluated for MC hydrogenation. The main products were found to be methyl butyrate (MB) and methyl 3-butenoate (M3B), resulting from hydrogenation and shift of the C=C bond in MC, respectively. The measured activity for both hydrogenation and shift of the C=C in MC was found to depend on the Pt dispersion where higher Pt dispersion favors the C=C hydrogenation reaction. The effect of reactant concentrations on the activity and selectivity for MC hydrogenation over the Pt/Al2O3 catalyst was examined in detail. Under the investigated conditions, the C=C hydrogenation was found to have a negative reaction order with respect to MC concentration but a positive H2 order. Further understanding of the MC hydrogenation was provided from H2 chemisorption experiments over the catalyst with and without pre-adsorbed MC and from transient experiments using alternating MC and H2 feeds. Based on the present experimental results, a reaction pathway was proposed to describe gas-phase MC hydrogenation over Pt/Al2O3. In order to gain more insight into the reaction, a kinetic analysis of MC hydrogenation was performed by fitting a power-law model to the kinetic data, moreover, dissociative H2 adsorption on the catalyst was found to be the rate-determining step by comparing the power-law model with the overall rate expressions derived from mechanistic considerations.
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| 5. |
- Heard, Christopher, 1988, et al.
(författare)
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Kinetic Regimes in Ethylene Hydrogenation over Transition-Metal Surfaces
- 2016
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Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; 6:5, s. 3277-3286
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Tidskriftsartikel (refereegranskat)abstract
- A first-principles microkinetic model has been developed and applied to ethylene hydrogenation over close-packed transition-metal surfaces of Ru, Rh, Pd, Os, Ir, and Pt. The model is based on density functional theory calculations, which have been used to determine the activation energies of the elementary steps of the reaction according to the Horuiti-Polanyi mechanism. A sensitivity analysis of the activity with respect to the kinetic parameters reveals distinctly different kinetic regimes across the periodic table. For Ru and Ir, the activity is controlled by the activation energy for ethylene to ethyl hydrogenation, whereas the other metals also have a sensitivity to the second hydrogenation step. The analysis shows, furthermore, that the activity could be enhanced considerably with minor reductions of the hydrogenation barriers.
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| 6. |
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| 7. |
- Ojagh, Houman, 1976, et al.
(författare)
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Effect of Thermal Treatment on Hydrogen Uptake and Characteristics of Ni-, Co-, and Mo-Containing Catalysts
- 2015
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 54:46, s. 11511-11524
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Tidskriftsartikel (refereegranskat)abstract
- Nonsulfided alumina supported Ni, Co, Mo, NiMo, and CoMo hydrotreating catalysts were synthesize. The TEM results indicated low dispersions of the active metals for Mo, NiMo, and CoMo, samples but significantly higher dispersion for the Ni sample. The effect of calcination and reduction on the hydrogen uptake capacity of the samples was investigated. The H-2-chemisorption and XPS results together showed that the precalcination step had a detrimental effect on the hydrogen absorption of the Ni sample formation of stable metal oxides. The XPS results revealed that the metal oxides of all calcined samples reached with the alumina support to form very stable spinels. Futher, the positive effects of a hydrogen atmosphere during the reduction, on the hyderogen uptake of the samples were cinfirmed by H-2-chemisorption measurements. Finally, the heats of adsorption (Delta H) of hydrogen for the Ni and Co samples were calculated to be 140 and 98 kJ mol(-1), respectively.
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| 8. |
- Xiao, Y., et al.
(författare)
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NiCo2O4 3 dimensional nanosheet as effective and robust catalyst for oxygen evolution reaction
- 2015
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 5:76, s. 61900-61905
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Tidskriftsartikel (refereegranskat)abstract
- Water electrolysis plays a fundamental role in the development of a sustainable energy system. In practice the efficiency of water electrolysis is severely limited by the sluggish kinetics of the oxygen evolution reaction. We reported a kind of integrated 3 dimensional oxygen evolution reactions (OER) catalyst by growing NiCo2O4 nanosheet arrays directly on conductive substrates. Such self-supported NiCo2O4 nanosheet electrodes exhibit high catalytic activity, good durability and nearly 100% faradic efficiency (FE) in alkaline electrolyte due to the enlarged electrochemical surface area and reduced electron transference resistance.
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