OP-II-3

OP-II-4REPEATED OPTIMIZATION OF A FIXED-BED REACTOR FORETHYLENE EPOXIDATIONXing-Gui Zhou, Xi-Yuan Qian, Ai-Hua PanState-Key Laboratory of Chemical Engineering, East China University of Science andTechnology, Shanghai 200237, China, E-mail: xgzhou@ecust.edu.cnEthylene epoxidation is one of the largest hydrocarbon partial oxidationprocesses in chemical process industry. Because of the typical wall-cooled reactorused for the reaction and the huge scale of the production, optimization of the reactorwill bring in significant profit for the industry by lowing ethylene consumption or byincreasing the ethylene peroxide productivity.Optimization of ethylene epoxidation is difficult because the performance of thereactor is related to a number of factors. Apart from the six main components, i.e.,ethylene, oxygen, ethylene oxide, carbon dioxide, water, and methane (as balancegas) that have effects on the catalytic reaction by competitive adsorption or bychanging the explosive limit of the gas mixture, and the contacting time that changesethylene conversion, chlorine is also introduced to adjust the activity and selective ofthe catalyst [1] . The most complicating factor in optimizing this process is catalystdecay which leads to a continuously decreasing catalyst performance. Accordinglythe optimal operating conditions, especially the reaction temperature, should bechanged with time.In this communication, an approach for repeated optimization of the process ispresented. A steady-state one-dimensional plug-flow model is used for the reactor,and a generalized power law expression [2] is used to account for the catalystdeactivation. The reactor is repeatedly optimized in the following way:(1) Determine the temperature profile from the present time to the end of thecatalyst operation, under the constraints of constant daily productivity and maximumallowable catalyst-bed temperature;(2) Optimize the inlet composition (outside the explosive envelope) and the spacevelocity to maximize (a) the productivity, or (b) the selectivity (with a presetproductivity);(3) Repeat the first step with the optimized inlet composition, the space velocityand the maximized or preset productivity.104