Cyclic carbonate synthesis via cycloaddition of CO2 and epoxides catalysed by beta zeolites containing alkyl imidazolium ionic liquids used as structure-directing agents

Abstract

Cyclic carbonates were synthesized via CO2 cycloaddition and epoxides, allyl-glycidyl-ether (AGE) and propylene oxide (PO), using hybrid materials formed by beta zeolites and ionic liquids, 1‑butyl‑3-methylimidazolium chloride (BMI.Cl) or 1-decyl-3-methylimidazolium chloride (DMI.Cl), as structure-directing agents which remained in their porosity. The beta zeolites, β-BMI.Cl and β-DMI.Cl, were used to convert AGE to AGC (allyl-glycidyl-carbonate), and β-BMI.Cl was also used to convert PO to PC (propylene carbonate). The optimal condition for β-BMI.Cl in which there was the total CO2 conversion was 50 bar pCO2 at 145 °C using AGE and 30 bar pCO2 at 130 °C using PO, being better than the catalyst β-DMI.Cl. The reuse of β-BMI.Cl led to a 95% yield of AGC after 5 h of reaction at 145 °C, showing the good stability of this catalytic system. The activation energy (Ea) of 97 kJ/mol was obtained through kinetic experiments conducted with AGE and β-BMI.Cl. Comparing experiments performed only with ionic liquids and hybrid materials, the last ones enabled the CO2 conversion with higher efficiency and were thermally more resistant. The results demonstrate that the β-BMI.Cl and β-DMI.Cl hybrid materials are promising catalytic systems to produce cyclic carbonates through CO2 conversion.