Effect of combining palladium, iridium or rhenium with platinum supported on H-ZSM-5 zeolite on their cyclohexene hydroconversion activities

Cyclohexene (CHE) hydroconversion was investigated using catalysts containing 0.35 wt.% Pt combined with 0.35 wt.% of Pd, Ir or Re supported on H-ZSM-5 zeolite as a support in a flow-type reactor and using a current of hydrogen gas throughout a temperature range of 50-400 °C. First, CHE was hydrogenated to cyclohexane (CHA) at relatively low temperatures, and dehydrogenated at relatively high temperatures to benzene passing through the formation of 1,3- and 1,4-cyclohexadienes (CHDEs). Moreover, CHE isomerises at intermediate temperatures to methylcyclopentenes (MCPEs), followed by their hydrogenation to methylcyclopentane (MCPA). Still at higher temperatures, CHE (and/or other products) suffer from hydrocracking to lower molecular weight hydrocarbons, beside alkylation of a portion of the formed benzene to toluene and xylenes. The kinetic parameters: activation energy and entropy were calculated to throw light on the nature of most important non-intermixing reaction (hydrogenation of CHE to CHA) using the monometallic and bimetallic catalysts.