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 °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 (C2–C4), longer lifetime and lower carbon deposition rate.

The SAPOs catalyst was synthesized with TEAOH/TEA = 0 (a), 0.05 (b), 0.1 (c), 0.2 (d), 0.4 (e), and 2 (f). Changing TEAOH/TEA can affect the chemical composition, morphology, crystal sizes and Si incorporation of SAPO-34. For the MTO reaction, SAPO-34 synthesized with TEAOH/TEA = 0.1 exhibits more excellent catalytic performance.Figure optionsDownload as PowerPoint slideHighlights
► SAPO-34 was synthesized with a mixture template of TEA and TEAOH.
► TEAOH/TEA affects the physicochemical and catalytic performance of SAPOs sample.
► SAPO-34 prepared with TEAOH/TEA = 0.1 has very high catalytic performance for MTO.