OP-II-3

OP-II-4In the second step optimization, if the productivity is set, the set productivity canbe increased until the temperature profile determined in the first step optimizationviolates the maximum allowable catalyst-bed temperature constraint. Simulationstudies show that maximizing the selectivity with step-wise increased productivity isequivalent to maximizing the productivity.This optimization approach has been integrated in a software package and appliedon an industrial fixed-bed reactor. The amount of chlorine addition was not used as amanipulated variable because it was added according to the variation of ethaneconcentration in the gas mixture. The kinetics of ethylene epoxidation, combustion andcatalyst deactivation were determined off-line by using the plant data collected over aperiod of time, and the optimization package was then used to find the best operatingvariables, which were then applied to the reactor. The reactor was repeatedlyoptimized for a year, which increased the average selectivity of about 0.5%.References:[1]. D. Torres, F. Illas, R.M. Lambert, Towards an understanding of promoter action inheterogeneously catalyzed ethane epoxidation: Why chlorine is the best halogen, J. Catalysis,260 (2008) 380-383.[2]. C. H. Bartholomew, Mechanisms of catalyst deactivation. Appl .Catal. A: General, 212 (2001)17-60.Acknowledgements:The authors are grateful for the financial support by Sinopec.105