Increased Silver Activity for Direct Propylene Epoxidation via Subnanometer Size Effects

Abstract

Silver Cluster Catalysts for Propylene Oxide The formation of ethylene oxide—in which an oxygen atom bridges the double bond of ethylene—can be made directly and efficiently from ethylene and oxygen with the aid of silver catalysts (typically comprising a small silver cluster on aluminum oxide). Similar approaches are not so successful for making propylene oxide—an important starting material for polyurethane plastics, which are made from chlorinated intermediates. Lei et al. (p. 224 ) report that silver trimers, Ag 3 , deposited on alumina are active for direct propylene oxide formation at low temperatures with only a low level of formation of CO 2 by-product, unlike larger particles that form from these clusters at higher temperatures. Density functional calculations suggest that the open-shell nature of the clusters accounts for the improved reactivity.

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Affiliated Institutions

• Fritz Haber Institute of the Max Planck Society DE
• Argonne National Laboratory US
• University of Illinois Chicago US
• Yale University US

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