Heterogeneously-catalyzed hydroalkoxylation of limonene and alpha-pinene in the presence of beta zeolite

Abstract

The heterogeneously-catalyzed hydroalkoxylation of limonene and alpha-pinene to the 1-methyl-4-[alpha-alkoxy-isopropyl]-1-cyclohexenes with C 1 -C 5 alcohols in the presence of beta zeolite has been studied in a continuous flow-type apparatus with a fixed bed reactor. The great advantage of the reaction in this reactor type is the easy separation of the products from the catalyst and, on the other hand, a higher productivity can be expected in a continuous process. Using methanol and limonene as feedstock, yields to 1-methyl-4-[alpha-methoxy-isopropyl]-1-cyclohexene of about 81% can be achieved. For the methoxylation of alpha-pinene, however, the highest yield to the corresponding alpha-terpinyl methyl ether is only up to 47%, because several bicyclic and double addition products are formed, too. The selectivity of all addition compounds together reaches values of about 75%. The dependencies of conversion, selectivity and product distribution upon temperature, WHSV, TOS, pressure and the starting material ratio will be discussed. Different linear and branched alcohols (C 1 -C 5 alcohols) have been compared considering their activities for the zeolite-catalyzed hydroalkoxylation of limonene and alpha-pinene.