Dry reforming - from understanding the elementary steps to better catalysts
Zusammenfassung der Projektergebnisse
We have studied the effect of nature and geometrical properties of metal particles and their interaction with the support on the activity for dry reforming of methane (DRM). The activity of Ni/ZrO2 catalysts for DRM can be significantly enhanced and catalyst’s thermal stability can be improved by activation and regeneration in presence of CO2 above 873 K. This is caused by maximizing the support metal interface, and by a fast, but thermally less taxing oxidation of carbon deposits in comparison to exposure to O2. After reduction in H2, Ni particles were partly covered with Zr-suboxides. The exposure to CO2 reduces the coverage by Zr-suboxides and creates a larger Ni-ZrO2 interface. Being equilibrated with the metal surface, the Zr-suboxide acts as catalyst by accepting and later transferring one oxygen of CO2 to Ni surface releasing CO in the decomposition of transiently formed carbonates. This leads to an additional channel of CO2 dissociation in addition to the direct CO2 dissociation on Ni. The higher kinetically controlled availability of atomic oxygen on Ni is hypothesized to reduce the carbon concentration on the surface, leading to less refractory carbon deposition. Using this knowledge guided us to develop a strategy to synthesize stable catalysts for DRM reaction. The new method uses Ni colloids as metal precursor on a metal-oxide as support. Ni particles with a size between 1 and 5 nm were dispersed on ZrO2, Al2O3 and SiO2. ZrO2 supported Ni catalysts exhibited stable activities for more than 2 days of DRM reaction at 873 K, with only small amounts of coke deposited on the catalysts. The strong interaction of the metal particles with the ZrO2 support allowed to stabilize small particle sizes during the DRM reaction, which have large metal-support interface and kinetically inhibit the deposition of inactive coke. We conclude that three elements have to be combined to stabilize base metal catalysts for dry reforming, (i) a partially reducible support that lowers the rate of coke formation and (ii) stabilizes small metal particles as well as (iii) a less exothermic regeneration of coked catalyst. In the future, we plan to further improve these methods to meet the requirement for industrial application including higher reaction temperature and pressure. Furthermore, combination of these two methods to synthesize a CO2 treated catalyst with small metal particles to reach a higher activity and stability is under development.
Projektbezogene Publikationen (Auswahl)
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Dry reforming – from understanding the elementary steps to better catalysts, 47. Jahrestreffen Deutscher Katalytiker, Weimar 2014
Y.Lou, A. Jentys, J.A. Lercher
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Development of stable nickel and platinum catalysts for dry reforming of methane, 48. Jahrestreffen Deutscher Katalytiker, Weimar 2015
Y. Lou, M. Steib, A. Jentys, J.A. Lercher
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Influence of the active metal on the product gas composition for Dry Reforming of Methane, Synthesis Gas Chemistry DGMK Conference 2015
M. Steib, A. Jentys, J.A. Lercher
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CO2 induced formation of highly active surface species on Ni/ZrO2 in methane dry reforming studied by operando XAFS, International Conference on Catalysis 2016
A. Jentys, Y. Lou, M. Steib and J. A. Lercher
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Formation of highly active surface species induced by CO2 on Ni/ZrO2 in methane dry reforming, ACS Meeting 2016
Y. Lou, M. Steib, A. Jentys and J. A. Lercher
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Influence of the active metal on the product gas composition for Dry Reforming of Methane, 49. Jahrestreffen Deutscher Katalytiker, Weimar 2016
M. Steib, A. Jentys, J.A. Lercher
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Ni and Pt colloids as metal precursor for highly stable methane dry reforming catalysts, 49. Jahrestreffen Deutscher Katalytiker, Weimar 2016
Y. Lou, A. Jentys, J.A. Lercher
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On the role of the support on the structural and catalytic properties of metal particles during CH4 reforming reactions, International conference on X-ray absorption fine structure 2016
M. Steib, A. Jentys, J.A. Lercher
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Enhanced Activity in Methane Dry Reforming by Carbon Dioxide Induced Metal‐Oxide Interface Restructuring of Nickel/Zirconia. ChemCatChem, 9,20, October 23, 2017, Pages 3809-3813
Y. Lou, M. Steib, A. Jentys and J. A. Lercher
