Effect of the presence of CO2 on the stability of the methanol-to-olefins reaction catalyzed by Zn/SAPO-34 zeolite

Abstract

The methanol-to-olefins reaction is a viable and promising technological route to replace increasingly scarce petroleum resources. SAPO-34 zeolite is an ideal catalyst for the methanol-to-olefins reaction due to its suitable acidity and pore structure. However, a single zeolite catalyst has limited performance, and in this work, metal species were introduced on SAPO-34 molecular sieves to achieve higher low-carbon olefin selectivity through the modulation of acidity. However, since the introduction of metals promotes aromatic cycling, it allows the creation of carbonaceous precursors and reduces the catalyst lifetime. Therefore, the introduction of CO₂ into the carrier gas inhibited the generation of carbonaceous precursors and thus prolonged the catalyst life. The presence of the metal species and their effects on SAPO-34's pores and structure were characterized by XPS, the change in acid amount was determined by NH₃-TPD, and the adsorption strength of the catalyst for CO₂ was determined by CO₂-TPD, revealing the active sites of the catalyst. High low-carbon olefin selectivity and long catalyst life were also achieved, with low-carbon olefin selectivity of 88.0%.