Study of the deactivation of a commercial catalyst for ethylbenzene dehydrogenation to styrene

The catalytic performance and characteristics of an industrial catalyst, fresh and spent, i.e. downloaded from an industrial reactor after a normal lifetime cycle, were compared. Some different causes of catalyst deactivation, such as loss or redistribution of promoters, active phase modification, Fe3+ reduction, coke deposition on catalyst surface and physical modifications, were evidenced by means of several techniques. All the mentioned causes of deactivation showed strictly interconnected and concurred to the decrease of conversion. However, the key factors leading to irreversible deactivation showed potassium migration towards the inner part of the extrudate particle, its agglomeration into concentrated spots and its volatilisation from the surface, together with the progressive Fe3+ reduction to Fe2+. These modifications led to the enhancement of coking activity and to the loss of mechanical properties, so making deactivation irreversible.