Support effects in the Pd catalyzed dehydrogenation of terpene mixtures to p-cymene

The selective conversion of renewable and widely available feedstocks composed of mixed terpenes to commercially interesting p-cymene was studied in the presence of both Ce-promoted Pd catalysts supported on zeolites and pure silica impregnated with Pd. The examined mixtures of terpenes were Acintene DP-738 and Oulu 405, cheap by-products in pulp- and paper industry. An interpretation of the obtained results was a Pd-catalyzed reaction, in which silica and zeolites were used as carriers of the active metal. The results showed that pure silica impregnated with Pd yielded over 90% p-cymene whereas zeolitic catalysts yielded more than 70%. In addition, the service time behaviour over the most promising catalyst was examined over a total time-on-stream (TOS) of 100 h and delivered very satisfactory results. The catalyst showed no deactivation during the whole TOS and a constant yield of 90% was observed. (C) 1998 Elsevier Science B.V. All rights reserved.