Direct growth of SAPO-34 crystals on ɣ-Al2O3 microspheres: A designated catalyst for fluidized-bed reactors of methanol conversion to light olefins

Although intense research has been allocated to improve the SAPO-34 catalyst and mitigate its fast deactivation, the catalyst shaping for fluidized-bed application has rarely been studied. The conventional spray drying method (SiO2 as the binder) downgraded the properties of the parent catalyst (i.e., caused 35% loss in active sites and 17% reduction in micropore surface area) and displayed an almost 30% shorter lifetime. Hence, a novel technique for in-situ growth of SAPO on the ɣ-Al2O3 microspheres was developed utilizing hydrothermal microwave heating. SAPO loadings of 31 and 44 wt% with different morphologies (cubic and sheet-like particles) were achieved using two different templates (TEAOH and TEA). Both SAPO-mounted ɣ-Al2O3 catalysts illustrated longer lifetimes (10.5 h and 22 h) during the MTO reaction at 425 °C with good light olefin selectivity (LOS ~ 75%) compared to their parent SAPO counterparts (9.5 h and 15 h) and spray dried catalyst (7 h with LOS = 73%). The results are promising and serve as a basis for further investigation of the applicability of the new catalyst material in circulating fluidized bed reactors with simultanious regeneration.