SiO2-Al2O3 catalysts for methanol to olefins: Comparative study with SAPO34 and ZSM5

Abstract

The conversion of methanol to olefins (MTO, T = 400 and 450 °C, WHSV=4 h-1) was studied using ZSM5, SAPO34 and amorphous silica-aluminas (different percentages of SiO2, 40%, 60% and 70%) (commercial catalysts) treated or not by HCl. All the catalysts studied present type IV adsorption/desorption isotherms of N2. The incorporation of HCl decreased the surface area, increased the pore size, the total acidity and the quantity and strength of Brønsted acid sites. The increase in the reaction temperature favors the yield of ethylene to a greater extent than that of propylene. The highest light olefins yield was obtained with catalysts containing 60% SiO2 at 400ºC. Its good performance is attributed to the combination of adequate acidity, high specific surface area, and small pore size. Catalysts with 40% SiO2 are not suitable for MTO. The addition of HCl to the aluminosilicates cause further deactivation.