The synthesis of SAPO-34 with mixed template 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 olefins (MTO), a mixture template of triethylamine (TEA) and tetraethyl ammonium hydroxide (TEAOH) was used to synthesize SAPO-34. The effects of the composition of the mixed template on the chemical composition, morphology and surface acidity of SAPO-34 were characterized by XRD, SEM, XRF, Si MAS NMR and NH3-TPD techniques. The catalytic performance of prepared SAPO-34 was investigated in a fixed-bed reactor at 450 degrees C for the MTO reaction. The results show that the chemical composition, morphology, crystal size and Si incorporation of SAPO-34 are affected greatly by the molar ratio of TEAOH/TEA. For the MTO reaction, all catalysts prepared show similar methanol conversion and product distribution, but their olefins selectivity and lifetime are greatly dependent on the ratio of TEAOH/TEA in the synthesis solution. Comparing with the SAPO-34 synthesized with single template. SAPO-34 synthesized with TEAOH/TEA = 0.1 possesses larger surface area, mild acidity and small crystal size and exhibits higher selectivity to light olefins (C-2(=)-C-4(=)), longer lifetime and lower carbon deposition rate. (C) 2011 Elsevier Inc. All rights reserved.