Propylene Oxide Cycloaddition with Carbon Dioxide and Homopolymerization: Application of Commercial Beta Zeolites

Abstract

The discovery of sustainable catalysts remains a key challenge in the advances of carbon dioxide utilization and polymer synthesis. Despite beta zeolites being widely used in industry as a kind of economical heterogeneous catalysts, their applications for carbon dioxide utilization and epoxides transformation remain relatively unexplored. Herein, we report the catalytic performance of commercial beta zeolites for the cycloaddition of carbon dioxide with epoxides as well as propylene oxide homopolymerization. The beta zeolites with different Si/Al ratios exhibit distinct properties in the reactions: (1) The one with high Si/Al ratio could catalyze the cycloaddition reaction with high selectivity to produce cyclic carbonate, and the reaction could be carried out even at ambient temperature and atmospheric pressure. Additionally, the zeolite is not sensitive to water or oxygen in the cycloaddition reaction, and it shows reusability with almost no change in activity. (2) The zeolite with low Si/Al ratio could catalyze the propylene oxide homopolymerization in the absence of CO₂ and a cocatalyst to produce polyether polyols. Interestingly, the polyether polyols obtained using this zeolite have similar molecular weights, irrespective of reaction conditions or conversion degrees of epoxide. The structural variety of the Si/Al ratio allows for switching the selectivity of zeolite in the reactions.