ALKOXYLATION OF LIMONENE AND ALPHA-PINENE OVER BETA-ZEOLITE AS HETEROGENEOUS CATALYST

The heterogeneously catalyzed alkoxylation of limonene and alpha-pinen e with C-1-C-5 alcohols to 1-methyl-4-[alpha-alkoxy-isopropyl]-1-cyclo hexene in the presence of beta zeolite in liquid phase has been studie d in both a discontinuous batch reactor and a continuous flow-type app aratus with a fixed bed reactor.In both reactor types, methanol and li monene as feedstock react to 1-methyl-4-[alpha-methoxy-isopropyl]-1-cy clohexene with a yield of about 85%. Thus, the beta zeolite seems to b e more active and selective for methoxylation of limonene than other c atalysts described in the literature for this reaction type. For the m ethoxylation of alpha-pinene, however, the highest yield of the corres ponding alpha-terpinyl methyl ether is only up to 50% in both reactor types, as several bicyclic and double addition products are formed in parallel. The selectivity for all addition products together can reach values of about 85%. The other zeolites and solid acids applied for t he methoxylation of alpha-pinene reveal considerably lower conversion and selectivity. We discuss the dependencies of conversion, selectivit y and product distribution on temperature, WHSV, TOS, pressure and the starting material ratio. The possibility for a regeneration of beta z eolite with air or oxygen is shown as well. Different linear and branc hed alcohols (C-1-C-5 alcohols) are compared in relation to their acti vity for the heterogeneously catalyzed alkoxylation of limonene and al pha-pinene.