Novozym 435 (Candida antarctica lipase B immobilized on polyacrylic resin) is used to generate perlauric acid directly from lauric acid and hydrogen peroxide. This generated perlauric acid was then applied for both in situ and ex situ epoxidation of styrene to styrene oxide. The reactions were carried out by using conventional heating as well as microwave heating. Various kinetic parameters affecting the conversion and initial rates of styrene to styrene oxide were studied including mass transfer, mechanism, kinetic modeling, and deactivation. Under microwave irradiation, there was an increase in the frequency factor resulting from enhanced collision of molecules, which can in turn be attributed to the increasing entropy of the system. The values of activation energy for the conventional and microwave heating are almost the same. The enzyme is deactivated by hydrogen peroxide and perlauric acid and also at high temperature under conventional heating. In the presence of microwaves, the deactivation of Novozym 435 was substantially reduced. (c) 2005 American Institute of Chemical Engineers.