Insight into a catalytic process for simultaneous production of biodiesel and glycerol carbonate from triglycerides

Abstract

Biodiesel, a renewable liquid fuel derived from triglycerides, is a promising alternative to compensate for the increasing demand of petro-diesel. However, 10% w/w glycerol is co-produced in the biodiesel production process which reduces the efficiency. The present work deals with the one-pot simultaneous co-production of biodiesel and glycerol carbonate from in-situ coproduced glycerol using hydrotalcite as a catalyst. Uncalcined hydrotalcite, calcined hydrotalcite and rehydrated hydrotalcite were screened for their activity towards the reaction in terms of conversion of soybean oil triglycerides and selectivity of glycerol carbonate. Uncalcined hydrotalcite served best for this purpose. At oil to methanol mole ratio of 1:90 and oil to DMC mole ratio of 1:30, the reaction gave 97.3% conversion of triglycerides and 93.2% selectivity of glycerol carbonate at 150°C in 3h at a catalyst loading of 0.0125g/cm3. The virgin and reused catalysts were well characterized using various analytical techniques which reveals the presence of basic as well as acidic sites with high surface area and ordered pore-size distribution. Effects of various experimental parameters on the conversion of triglycerides and selectivity to glycerol carbonate were studied to interpret the reaction kinetics. The kinetic rate constants and the activation energies were calculated. Reusability study of the catalyst was done up to two cycles and the catalyst was found to be robust and reusable.