Catalysis

Ultrasound and Microwave-assisted Enzymatic Catalysis of Xylitol Monooleates

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Abstract

The increasing social and political pressures related to the environmental problems generated by traditional chemical processes involving the use of toxic solvents, strong acids, and high energy demand suggest utilization of clean methodologies that follow the precepts established by green chemistry. Enzymatic catalysis promotes enantioselective syntheses operating under mild condi-tions of temperature and pressure. The process, however, requires elevated times of reactions and the use of high-cost immobilized derivatives. These consequences usually become obstacles to industrial application of such syntheses. Using of ultrasound and microwaves as alternative heat-ing sources in the enzymatic catalysis, it is possible to overcome these problems besides leading to satisfactory yields and allowing the reduction of solvent volume. In this work, esterification reactions of oleic acid were performed to obtain xylitol monooleate by using alternative method-ologies which agree with the precepts of green chemistry. Yield of 96,5% employing microwave heating and 74,6% with ultrasound were obtained, both using the amount of 2,5 mL of solvent, half of the previous reports. In microwave heating, the reuse of the immobilized enzyme was pos-sible till the third use, retaining yields above 77%. The results showed that was possible to reduce the mass of the catalyst, the volume of the solvent, and the energy consumed in the process with-out significant loss related to the reaction yield.

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