The Synthesis of SAPO-34 at Different Crystallization Temperature and its Catalytic Performance for Methanol to Olefins Reaction

In order to enhance the catalytic performance of SAPO-34 for the reaction of methanol to light olefins (MTO), three different crystallization temperatures were used to synthesize SAPO-34. The catalysts were synthesized hydrothermally with molar composition as 1 Al2O3: 1 P2O5: 0.4 SiO2: 1 TEAOH: 0.5 TEA: 0.5 MOR: 70 H2O. The effects of the crystallization temperature on the phase purity, morphology and functional groups of SAPO-34 were characterized by XRD, SEM and FTIR techniques. The relative crystallinity was decreased by increasing crystallization temperature andsome impurities appeared at high crystallization temperature. All samples showed cubic morphology with different crystal size. The catalytic performance of synthesized SAPO- 34 was investigated in a fixed-bed reactor at 410C. For the MTO reaction, all synthesized catalysts showed similar product distribution and methanol conversion, but light olefins selectivity was greatly dependent on the crystallization condition. The sample was synthesized at 170C and 24 h, possessed the highest light olefins due to highest amount of acid sites, relative crystallinity and smallest mean crystal size.