Studies on Hydrodecyclization of Methylcyclopentane and Benzene in the Presence of a Reforming Catalyst

Abstract

Hydrodecyclization reaction of methylcyclopentane (MCP) and benzene was studied under normal reforming conditions, in the presence of a platinum-alumina reforming catalyst poisoned by coke and/or thiophene.Ring-opening reaction of five-membered ring of MCP takes place competitively on two different kinds of active sites. One of them is highly active, but is easily poisoned by small amount of thiophene added to the feed or moderate amount of coke deposited on the catalyst, while the other site is relatively less active, but is little affected by those poisons. The former site is on the surface of the platinum, and the latter is perhaps acidic site of alumina. And this acid-catalyzed reaction may be explained by so called dual function theory.Rate of hydrodecyclization (including a small amount of hydrocracking) of MCP, which was catalyzed by each site mentioned above, was nearly of the first order with respect to the partial pressure of MCP. And the rate of isomelization of MCP to six-membered ring compound was also observed to be of the first order with respect to the partial pressure of MCP. Activation energies of all the reaction mentioned above-hydrodecyclization of MCP on both sites, and isomerization of MCP to six-membered ring-were observed to be in the range of 30∼35kcal/g-mol.According to kinetic discussions of hydrodecyclization of MCP and benzene, it is concluded that the rate constant of cyclization of n-hexane to MCP is higher than that of n-hexane to six-membered ring, and the rate constant of MCP to six-membered ring is much higher than that of n-hexane to MCP, under the conditions close to commercial reforming processes, using the catalyst moderately poisoned by coke and sulphur compounds.