LTA zeolites as catalysts for transesterification of glycerol with dimethyl carbonate

Abstract

The objective of this study was to investigate the use of LTA-structured zeolites as catalysts for synthesizing glycerol carbonate through the transesterification of glycerol with dimethyl carbonate, under mild reaction conditions. To evaluate the catalysts, a range of characterization techniques, including XRD, AES, SEM, TPD-NH3, TPD-CO2, and FT-IR with probe molecules like pyridine and pyrrole, along with elemental analysis, were employed. The investigation focused on various forms of LTA-structured zeolites (with K, Na, and Ca cations) to assess their impact on transesterification activity, with particular attention to the type of ion utilized and their basicity. Among these zeolites, K-Na-LTA (3A) zeolites demonstrated the most promising performance, achieving glycerol conversion rates ranging from 55 % to 77 %. Moreover, increasing basicity in the 3A zeolites led to higher glycerol conversion and glycerol carbonate yield. Encouragingly, all tested samples exhibited 100 % selectivity, exclusively producing the desired glycerol carbonate. However, during catalyst recycling, the decrease in glycerol conversion was observed, likely due to the leaching of active sites from the catalyst into the reaction medium. Methanol, being a one of the products, was identified as a potential agent responsible for the removal of potassium ions, during this process.