Changes in the hydrogenative ring-opening mechanism of cyclohexene oxide over Cu/SiO₂ resulting from the addition of cyclohexene, a major product

Abstract

The ring-opening mechanism influencing effect of a major product in the cyclohexene oxide–D₂ system was investigated over a Cu/SiO₂ catalyst. This product is cyclohexene, thus, the hydrogenative ring opening of a 1:1 cyclohexene oxide–cyclohexene mixture was studied in the presence of D₂ at 403 K in a closed circulation reactor. It was found that the mechanism of single C–O scission was not affected, but that of the double C–O scission was changed. Simultaneous bond cleavage was the major route of ring opening in the additive-free system and it became consecutive on cyclohexene addition. Added cyclohexene was hydrogenated with a very low rate, but it transformed the surface of the catalyst and, thus, facilitated the change in the mechanism. An explanation concerning the seemingly anomalous lack of deuterium in a product (cyclohexane) not seen in the additive-free system is also suggested.