DETERMINATION OF THE KINETICS OF ETHENE EPOXIDATION

Several problems and pitfalls in the use of laboratory reactors for th e determination of the kinetics of ethene epoxidation over industrial silver on or-alumina catalyst are discussed. Also, commonly used metho dologies for kinetic studies are dealt with because of the general nat ure of some problems. Some advice is given in choosing and using the a ppropriate reactor type. Further, a method is discussed to determine k inetics in a cooled tubular reactor without having to use heat transpo rt relations. The activation and deactivation of the silver catalyst h ave been studied in a Berty-type reactor, in a novel internal recycle reactor and in a cooled tubular reactor. It was found necessary to act ivate the silver catalyst for approximately 170 reaction hours under r eaction conditions to obtain a stable and reproducible catalyst activi ty. Thermal sintering was probably of importance in experiments at the maximum temperature of 543 K. Deliberate addition of small amounts of 1,2-dichloroethane resulted in rapid deactivation of the catalyst. Th e activity could be restored by addition of small amounts of ethane to the feed. Also, fluorine and silica have been shown to poison the cat alyst. Differences in the behaviour of the catalyst in the three react ors may be attributed to the sensitivity of the catalyst towards tiny amounts of poisons present in the reactors and feed mixtures used.