Transformations of cyclohexene oxide over silica-supported Cu, Pd, and Rh catalysts in H-2/D-2 atmosphere

Transformations of cyclohexene oxide were studied in a recirculation reacto r and a flow system over silica-supported transition and early transition m etal catalysts. Hydrogen pressure dependence of the transformations was mea sured over Cu/SiO2 at 403 K in the 0-98.7 kPa range. Deuterium distribution in the reactant and products were determined at 20 kPa D-2 pressure. The r eactions were studied in the flow reactor under D-2 stream over Cu/SiO2 (37 3 K, 403 K, 443 K, 523 K), Pd/SiO2 (403 K), and Rh/SiO2 (403 K) catalysts t oo. Deuterium distributions were determined at the commonly used 403 K. Ove r each catalyst, in both reactor types three main transformation pathways w ere found. Single C-O scission occurred via isomerization and hydrogenation . Double C-O cleavage, that is, deoxygenation was also found to be importan t. Product distribution varied from catalyst to catalyst and it was influen ced by the conditions, as well as the reactor types. Deuterium distribution revealed significant differences in the elementary surface processes over the catalysts. Detailed mechanistic interpretation of the transformations i s offered. (C) 1999 academic Press.