Study on the deactivation and regeneration of the ZSM-5 catalyst used in methanol to olefins

ZSM-5 zeolite catalyst modified by a trace of metal cations shows high activity and high selectivity for the reaction of methanol to olefins (MTO), but it inclines to deactivate during the reaction. In this paper, the mechanism of the catalyst deactivation and the regeneration method were studied by X-ray diffraction (XRD), N(2) adsorption-desorption, infrared spectra (IR), and infrared spectra coupled with NH(3) molecular probes (IR-NH(3)). These characterizations indicated that coke formation was the main reason for the catalyst deactivation. To regenerate the deactivated catalyst, two methods, i.e., calcination and methanol leaching, were used. N(2) adsorption-desorption, IR and IR-NH(3) characterizations showed that both methods can eliminate coke deposited on the catalyst and make the catalyst reactivated. XRD showed that the structure of the catalyst did not change after regeneration. Interestingly, the regenerated catalyst even showed better catalytic performance of the MTO reaction than the fresh one. Besides, the calcination regeneration can eliminate coke more completely, however, the methanol leaching method can be more easily carried out in situ in the reactor.