The direct epoxidation of propene in the explosive regime in a microreactor - A study into the reaction kinetics

The usage of a microreactor system for the direct epoxidation of propene over a gold-titania-based catalyst system using a mixture of hydrogen, oxygen, and propene allows for the safe operation of the reaction in the explosive regime. A kinetic study was performed on the effect of the concentration of hydrogen, oxygen, and propene on the reaction rate as well as the catalyst deactivation and reactivation. A simple algebraic expression was developed, based on published kinetics, which provided the three reaction rate constants as a function of the feed gas concentrations. It is shown that the propene concentration does not influence the propene oxide formation rate; however, higher propene concentrations significantly reduce the catalyst deactivation rate. Hydrogen increases the rate of the epoxidation reaction, while it only has a minor influence on the rate of deactivation and reactivation. Oxygen has a beneficial effect on the epoxidation reaction: it slightly decreases the deactivation rate and is beneficial for the catalyst reactivation. It is shown that, for the gold on titania dispersed on a silica catalyst used in this study, it is advantageous to perform the direct propene epoxidation in a microreactor system at the highest possible feed concentrations for each of the reactants. This results in the highest propene oxide productivity and the lowest deactivation rate.