NaCl-Promoted CuO–RuO 2 /SiO 2 Catalysts for Propylene Epoxidation with O 2 at Atmospheric Pressures: A Combinatorial Micro-reactor Study

A combinatorial approach is used to investigate several alkali metals promoted Cu-Ru binary oxide cata- lysts with improved catalytic performance in the propylene partial oxidation. 2 %Cu/5 %Ru/c-SiO2 catalyst had the best yield with high propylene conversion and propylene oxide (PO) selectivity. Among the promoters screening in the study, NaCl promotion significantly increased the PO selectivity accompanied by some attenuation in the total propylene conversion. It was proposed that binary oxide catalysts revealed a greater number of exposed catalytically active adsorption sites as compared to monometallic oxide counterparts according to XPS and FTIR results. Besides NaCl addition alters the structure, yielding a significantly improved PO selectivity without any change in the particle size of Cu and Ru oxide according to XRD analysis.