Implementation of gas-phase kinetic model for the optimization of the ethylene oxide production

The direct epoxidation of light olefins is a key process of the chemical industry. However, several concerns regarding industrial and safety aspects, such as the occurrence of runaway reactions and the relevance of side reactions reducing process selectivity, are still under investigation. To this aim, a reactor operation diagram was obtained under process relevant conditions, allowing for the identification of runaway, hot spots and pseudo adiabatic operation regions by using several criteria and kinetic models. Indeed, catalytic only or complete (catalytic + non-catalytic) kinetic mechanisms were adopted to this aim. The selection of different runaway criteria was found to be negligible on the region boundaries. On the contrary, significant discrepancies were observed for hot spot region boundaries and between catalytic and complete models. An in-depth analysis, based on thermodynamic and kinetic models, was performed to individuate the optimized operative conditions. Flammability limits were estimated by applying the limiting laminar burning velocity theory, in case of different inert composition and initial temperature. The results indicate that a decrease in the operative temperature has the potential to either reduce the capital costs or increase process safety. Furthermore, the proposed approach can be intended as a supporting procedure for the selection of process alternatives and reactor design