Selective Synthesis of Dimethyl Carbonate via Transesterification of Propylene Carbonate with Methanol Catalyzed by Bifunctional Li-Al Nano-composite

A series of binary mixed metal oxides (MMOs) were synthesized by combination of Mn+/Al3+ (Mn+= Li, Mg, Co, Ni, Zn) via co-precipitation method and screened for transesterification of propylene carbonate (PC) with methanol. The aim of this study was to understand the role of acid-base properties of MMOs on the activity and selectivity towards dimethyl carbonate (DMC) synthesis. The MMOs were characterized in detail by XRD, BET, TEM, NH3 and CO2-TPD techniques. Catalysts synthesized by various combination of Mn+/Al3+ showed different textural and surface properties and the strength of acid-base sites were also found to be significantly altered. These changes in physicochemical properties significantly affected the PC conversion and selectivity to DMC. Li+ incorporated in Al3+ showed the formation of octahedral alpha-LiAlO2 phase having more amounts of active sites (O2-) present on the edges and corner of the structure. This resulted in easy accessibility of active sites and higher activity compared to other catalysts screened. Furthermore the catalyst retained high activity and selectivity for six consecutive recycle experiments; which is highly desirable for large-scale application.