日本ゼオライト学会　刊行物 Publication of Japan Zeolite Association

Zeolite Catalysts has micro pores within their crystallites, the diameters of which are almost equal to molecular sizes of lighter hydrocarbons. Therefore, the catalysts show high shape selectivity. The deactivation mechanisms of the catalysts are largely different from those of usual metal-oxide catalysts. In this paper, the deactivations of the zeolite catalysts caused by coke deposition and sintering are reviewed concerning with the pore structures of the zeolite catalysts. In the deactivation due to the coke formation, the deactivation is described in view of the coking reaction, the effects of temperature and acidic properties, the location of coke deposition, the mechanisms, models for the deactivation and the during reaction of coked catalysts. Coked catalysts are usually regenerated by burning off the coke. During this regneration, the catalysts are exposed to high temperature and steam atmosphere. Under these conditions, the sintering proceeds and the dealumination is accelerated, leading to irreversible deactivation. This paper referrs to the sintering mechanisms and methods for reducing the sintering rates.