EVALUATION OF MODES OF CATALYST DEACTIVATION BY COKING FOR CUMENE CRACKING OVER ZEOLITES

The deposition of coke deactivates a catalyst by the suppression of active sites and/or by choking of pores. The so-called Constant-Coke Arrhenius Plot technique can assess the magnitudes of these two modes of deactivation using reaction experiments under process conditions. For cumene cracking over REY zeolite, a TGA has been used as a continuous-flow microreactor to monitor coke levels, with activity measured by an on-line GC. Using modifications described previously for small-pore catalysts, we show that both temperature and coke level influence the relative importance of site suppression and pore choking in the deactivation of the zeolite. At relatively high temperatures, site suppression is predominant at all coke levels studied here. At lower temperatures, pore choking is more important at low levels of coke, with site suppression increasing in importance at the higher coke levels. The results are consistent with a physical model developed. © 1993 Academic Press, Inc.