Chitosan/MCM-41-SO3H composites as catalyst of the etherification of limonene

Abstract

Etherification of limonene with methanol, ethanol, 1-propanol, 2-propanol, 1-butanol and 2-butanol to ethers were performed using a mesostructured silica with sulfonic groups, like MCM-41-SO3H, immobilized in chitosan (CHT), as composite catalyst (MCM-41-SO3H/CHT). The main product of limonene etherification in the present of MCM-41-SO3H/CHT composites was the α-terpinyl ether, which can be used in pharmaceutical and fine industry.

Composite materials with different amounts of catalyst were prepared. These materials were used in methoxylation of limonene. It was observed that the catalytic activity of composite materials increased with the loading of MCM-41-SO3H dispersed in chitosan. The composite catalyst with highest activity was [MCM-41-SO3H]3/CHT.

Composite material, [MCM-41-SO3H]3/CHT, can be recovered and reused in reaction of limonene with methanol.

As [MCM-41-SO3H]3/CHT composite showed the highest catalytic activity in methoxylation of limonene, this material was applied in etherification of limonene with ethanol, 1-propanol, 2-propanol, 1-butanol and 2-butanol. An increased of activity with a decrease of the carbon number of alcohols was observed. A possible explanation is the presence of some internal limitations in channelling of composite catalyst.

Selectivity of [MCM-41-SO3H]3/CHT to ethers was studied. When the carbon number of alcohol chain increase, a decrease of selectivity of composites is verified.