A mathematical model for a tubular reactor producing epichlorohydrin (ECH) over titanium silicate-1 (TS-1) catalyst is proposed in this work. The Eley−Rideal mechanism is selected to describe the catalytic reaction, and pertinent kinetic parameters are estimated by a genetic algorithm combined with the Levenberg−Marquardt algorithm. The time-varying catalytic activity and effectiveness factor of a commercial TS-1 catalyst pellet are additionally included in the two-dimensional dynamic mass and energy transport model for the packed-bed tubular reactor. In a case study, the optimal length of the tubular reactor is determined by simulations using the developed model to maintain both conversion and selectivity above 96% during 90 days. The proposed model will contribute to effective design of industrial ECH production processes.