Spatially‐Resolved Insights Into Local Activity and Structure of Ni‐Based CO 2 Methanation Catalysts in Fixed‐Bed Reactors
Abstract On a Ni/Al 2 O 3 and a Ni−Fe/Al 2 O 3 catalyst spatial concentration and temperature profiles were determined that occur along the axial direction of the catalyst bed. They were correlated to structural gradients under reaction conditions to elucidate the local dependency of catalyst struct...
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| Published in: | ChemCatChem 2021-07, Vol.13 (13), p.3010-3020 |
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| Main Authors: | , , , , , , |
| Format: | Article |
| Language: | eng |
| Online Access: | Get full text |
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| Summary: | Abstract On a Ni/Al 2 O 3 and a Ni−Fe/Al 2 O 3 catalyst spatial concentration and temperature profiles were determined that occur along the axial direction of the catalyst bed. They were correlated to structural gradients under reaction conditions to elucidate the local dependency of catalyst structure on reaction‐induced changes of the gas phase. The quantitative concentration and temperature profiles revealed a hotspot in the first third part of the fixed‐bed, which led to by‐product formation of CO. Complementary structural information obtained by spatially‐resolved quick X‐ray absorption spectroscopy unraveled a strong impact of reaction‐induced gradients in gas phase on the oxidation state of Fe with a higher oxidation state towards the end of the catalyst bed, while Ni was only slightly affected. Diffuse reflectance infrared Fourier transform spectroscopy further revealed that addition of Fe to a Ni/Al 2 O 3 catalyst reduces the amount of adsorbed CO species. Hence, Fe hampers blocking of active Ni 0 sites by CO and preserves a high fraction of reduced Ni species. Furthermore, an alternative reaction pathway observed on Ni−Fe provided locally a higher activity for CO 2 hydrogenation. Overall, the importance of considering local gradients in catalytic reactors is demonstrated. |
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| ISSN: | 1867-3880 1867-3899 |