Quenching the deactivation in the methanol-to-olefins reaction by using tandem fixed-beds of ZSM-5 and SAPO-18 catalysts

Abstract

We proved that the disposition of tandem fixed-beds of ZSM-5 with SAPO-18 catalysts could decrease the deactivation of the second catalytic bed during the methanol-to-olefins (MTO) reaction. For this purpose, we prepared two catalysts based on ZSM-5 zeolite and SAPO-18 zeotype; characterized them using XPS, XRD, 29Si NMR, N2 physisorption, NH3-TPD and FTIR; tested them individually, in mixed or tandem forms using a fixed-bed reactor or in-situ reactors monitored with UV-vis or FTIR spectroscopies; and characterized the catalyst during the reaction or after it. The catalytic beds (mixed or tandem) did not offer any significant enhancement or synergetic effect in product selectivity. However, the catalytic lifetime of the second bed in the tandem catalytic beds (particularly if that is made up of SAPO-18 catalyst) was prolonged because this bed receives less oxygenates (methanol and dimethyl ether) and more water, which slows down the deactivation of the second catalytic bed.