Insight into the influence of Re and Cl on Ag catalysts in ethylene epoxidation.

Autor: Keijzer CJ; Materials Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University The Netherlands P.E.deJongh@uu.nl., Weide PT; Materials Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University The Netherlands P.E.deJongh@uu.nl., Helfferich KH; Materials Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University The Netherlands P.E.deJongh@uu.nl., Zieciak J; Shell Global Solutions International Amsterdam The Netherlands., de Ridder M; Shell Global Solutions International Amsterdam The Netherlands., Dalebout R; Materials Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University The Netherlands P.E.deJongh@uu.nl., Lohr TL; Shell Catalysts & Technologies Houston Texas USA., Lockemeyer JR; Shell Global Solutions US Inc. Houston Texas USA., van den Brink P; Shell Global Solutions International Amsterdam The Netherlands., de Jongh PE; Materials Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University The Netherlands P.E.deJongh@uu.nl.
Jazyk: angličtina
Zdroj: Catalysis science & technology [Catal Sci Technol] 2024 Nov 06. Date of Electronic Publication: 2024 Nov 06.
DOI: 10.1039/d4cy00858h
Abstrakt: Commercial ethylene epoxidation catalysts consist of α-alumina supported Ag particles and usually contain a mixture of promoters. High selectivity catalysts typically include a small amount of rhenium species. We studied a series of Ag catalysts promoted with Re loadings up to 4 at% (Re/(Re + Ag)), which is intentionally higher than in optimized commercial catalysts to facilitate characterization and to amplify the influence on catalysis. Sequential impregnation brought Re and Ag in such close contact that they formed a new characterized phase of AgReO 4 . Chemisorption experiments showed that both ReO x and AgReO 4 species act as a reversible reservoir for O 2 . Ethylene epoxidation was performed without and with the industrially crucial ethyl chloride promoter in the feed. Without the chloride (Cl), the ethylene oxide selectivity increased when Re was present, whereas the combination of Re and Cl decreased the ethylene oxide selectivity at higher Re loadings. Systematic ethylene oxide isomerization experiments revealed that Re and Cl individually inhibit the isomerization on the Ag surface. However, Re and Cl combined increased the isomerization, which can be explained by the surface becoming overly electrophilic. This hence shows the importance of studying promoters both individually and combined.
Competing Interests: There are no conflicts to declare.
(This journal is © The Royal Society of Chemistry.)
Databáze: MEDLINE
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