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

A microreactor system was used for a kinetic study into the direct epoxidation of propene over a gold-titania based catalyst system using a mixture of hydrogen, oxygen, and propene. The small dimensions of a microreactor allow for the safe operation of the reaction in the explosive regime. The effect of the concentration of hydrogen, oxygen, and propene on the reaction rate was determined as well as the effect on 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 composition. It is shown that propene does not influence the epoxidation rate; however, higher propene concentrations significantly reduce the catalyst deactivation rate. Hydrogen significantly increases the rate of the epoxidation, while it has a minor influence on the deactivation and reactivation of the catalyst. Oxygen has a threefold beneficial effect on the reaction: it increases the epoxidation rate; it slightly decreases the deactivation rate, and increases the rate of the catalyst reactivation. Performing the direct propene epoxidation in a microreactor system inside the explosive regime at optimized high feed concentrations can increase the propene oxide formation rate by a factor of three, while at the same time lowering the deactivation rate.