Influence of atmosphere, interparticle distance and support on the stability of silver on α-alumina for ethylene epoxidation

• Published in: Journal of catalysis Vol. 405; pp. 534 - 544
• Main Authors: Keijzer, Petra H., van den Reijen, Jeroen E., Keijzer, Claudia J., de Jong, Krijn P., de Jongh, Petra E.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.01.2022
• Subjects: Ethylene epoxidation; High surface area; Macroporous α-alumina; Ostwald ripening; Silver; Stability; Silver; Stability; High surface area; Ostwald ripening; Macroporous α-alumina; Ethylene epoxidation
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2021.11.016

[Display omitted] •Ostwald ripening dominates particle growth of supported silver particles.•Particle growth on α-alumina depends on atmosphere and temperature.•Restricting silver particle movement does not limit particle growth.•Intraparticle distance is a crucial parameter for silver particle stability.•Higher surface area α-alumina provides better silver catalyst stability. The stability of supported metal particles is an important parameter in heterogenous catalysis. For silver catalysts supported on α-alumina, industrially used in ethylene epoxidation, the loss of silver surface area as result of particle growth is one of the most important deactivation mechanisms. In this work, the growth of silver particles was investigated by exposing catalysts to thermal treatments. The presence of oxygen during heating strongly enhanced particle growth, and the interparticle distance was a crucial parameter. However, restricting movement of complete silver particles using cage-like α-alumina did not limit particle growth. These findings indicate that Ostwald ripening was the dominant mechanism behind particle growth, with the diffusion of oxidized silver species being a rate limiting factor. Finally, higher surface area α-alumina provided better silver stability during ethylene epoxidation, with only limited decrease in selectivity. This makes silver supported on high surface area α-alumina promising candidates for ethylene epoxidation catalysis.