Valorization of glycerol into glycerol carbonate using the stable heterogeneous catalyst of Li/MCM-41

Abstract

The present study explored the catalytic activity of the heterogeneous catalyst for transesterification of glycerol into glycerol carbonate, a versatile compound. Transesterification of glycerol was investigated with different active metals (Li, La, Ce, Mg, K) impregnated on MCM-41 (Mobil Composition of Matter No. 41) framework. Among these, lithium incorporated MCM-41 proved the better catalytic activity towards the formation of glycerol carbonate. The shortening of a long-range hexagonal array was observed with active metal incorporation due to the accumulation of non-framework Li species in the MCM-41 structure. BET study revealed that Li/MCM-41 possess type IV hysteresis loop according to IUPAC standards. The average pore diameter was increased from 25.43 Å to 62.02 Å with active metal incorporation in the MCM-41 framework. The catalytic activity of Li/MCM-41 was observed by varying different weight ratios of active metal and the calcination temperature. The results demonstrated that 5 wt% Li impregnated on MCM-41, calcined at 450 °C, appeared to have a maximum yield of glycerol carbonate. Additionally, the influence of reaction operating parameters was also investigated. The results showed that 99 ± 1.89% glycerol conversion and 93.14 ± 2.52% glycerol carbonate yield was achieved at dimethyl carbonate-to-glycerol molar ratio of 3, catalyst dosage of 4 wt% (relative to glycerol mass) and a reaction temperature of 90 °C in 3 h. The recyclability and stability of the screened catalyst was also studied under optimized conditions. The activation energy of the catalyst was determined by solving the differential equation using MATLAB ODE15s tool, and the obtained value was 53.77 ± 3.26 kJ/mol. The E-factor and PMI (Process mass intensity) values of glycerol carbonate synthesis were determined as 1.16 and 2.16, respectively, which demonstrate the less waste generation during the process.