Study of the effects of regeneration of USY zeolite on the catalytic cracking of polyethylene

Abstract

In this work, a study of the deactivation and reuse of USY zeolite for the pyrolysis of polyethylene has been carried out in a batch reactor at 500 °C. From the different tested zeolite/plastic ratios, 1/10 is the optimal ratio which allows giving rise to a liquid product free of wax. Regeneration was established by heating at 500 °C for 3 h coked zeolite in presence of air. The liquid yield begins to increase from the 11th cycle of regeneration until reaching a maximum at the 14th cycle showing a lost in the zeolite activity producing a viscous product.The liquid fraction derived from the first eight cycles was a mixture of C4-C27 compounds with a maximum C5-C7 fraction. In the 14th cycle of regeneration, compounds having higher carbon number were obtained and the yield of linear compounds increases up to 29%. To explain the relative activity of the regenerated zeolite, the textural properties and the XRD patterns results of the zeolite recovered after the 1st and 14th cycles have been compared with those obtained with fresh catalyst. The study showed that after 14 cycles of regeneration, the zeolite is still active but its activity level has decreased.