The effects of SiO2/Al2O3 and H2O/Al2O3 molar ratios on SAPO-34 catalysts in methanol to olefins (MTO) process using experimental design

•Silicon and water content effects on SAPO-34 synthesis and MTO reaction were studied in this paper.•High total light olefins selectivity was obtained (71.45%).•High crystallinity, surface area as well as small crystal size of SAPO-34 catalysts improved the production of light olefins.•Water content in SAPO-34 synthesis gel had no significant effect on the performance of catalyst in MTO process.•Catalyst with small crystal size and relatively high crystallinity had the highest light olefins selectivity.

To investigate the effects of silicon and water content on SAPO-34 catalyst, a number of experiments by using response surface methodology of molar ratios of SiO2/Al2O3 = 0.1–0.6 and H2O/Al2O3 = 50–120 were performed. The catalytic performances of prepared SAPO-34 samples at 410 °C and 30 wt.% methanol in water for MTO process were investigated. Due to relatively high crystallinity and small crystal size (1.3 μm); SiO2/Al2O3 = 0.17 and H2O/Al2O3 = 109.75 catalyst showed high total light olefins selectivity (71.45%). ANOVA results indicated that the light olefins selectivity was influenced more by changing of SiO2/Al2O3 molar ratio rather of H2O/Al2O3 molar ratio.

Graphical abstractSynthesis and performance of SAPO-34 catalysts with different SiO2/Al2O3 and H2O/Al2O3 molar ratios in MTO process were investigated. Catalyst with molar ratios of SiO2/Al2O3 = 0.17 and H2O/Al2O3 = 109.75 showed the highest value of total light olefins selectivity because of its small crystal size and proper crystallinity.Figure optionsDownload full-size imageDownload as PowerPoint slide