Modeling and Optimization of a Packed-Bed Tubular Reactor for Eco-Friendly Epichlorohydrin Production

A liquid-phase epoxidation process using hydrogen peroxide (HP) and titanium silicate (TS-1) is an eco-friendly process to produce epichlorohydrin because high conversion and selectivity can be obtained over the catalyst with reduced waste water discharge. In this work, a mathematical model was built to predict catalyst deactivation, temperature profile, as well as time-varying conversion and selectivity of a packed-bed tubular reactor using HP and TS-1. The first step toward this work is the kinetic modeling of this catalytic reaction which consists of reaction mechanism selection and kinetic parameter estimation. Based on published literatures on the titanium-silicate catalyzed epoxidation of olefins with HP, the reaction mechanism was selected as the Eley-Rideal mechanism and the kinetic parameters were estimated by a hybrid optimization technique combining the Levenberg-Marquardt algorithm and genetic algorithms. In addition to the kinetic modeling of the catalytic reaction, the characteristics of a commercial TS-1 catalyst pellet, such as time-varying catalytic activity and effectiveness factor, were also considered. To build the mathematical model of the pilot-scale reactor, the kinetic model and the characteristics of the TS-1 catalyst pellet were included in 2-dimensional dynamic mass and energy transport models for a packed bed tubular reactor. Therefore, the time-varying temperature and concentration profiles of the reactor were obtained by dynamic simulations. Based on the simulation results, the relationships between operating conditions and the conversion and selectivity of the tubular reactor are analyzed. To maximize catalyst activity in a long-term operation, the optimal operating temperature can be identified by controlling the hot spots of the reactor. Also, the optimal length of the reactor is determined to maintain desired conversion and selectivity. Simulation results show that the optimally-sized reactor operating at the optimal conditions may maintain both conversion and selectivity above 96% during 2,000 hours.

Acknowledgement: This work was supported by Hanwha Chemical R&D Center.