Carboxylation of glycerol in a biodiesel plant

The US production of biodiesel is expected to grow with a target of 400 million gallons by the year 2012 and produce around 3.5 million gallons of crude bioglycerol. Refining crude bioglycerol is expensive, hence 50% of it is disposed of and the remaining is sold at a minimal price. Conversion of bioglycerol into value-added products has emerged in recent years as a result of bioglycerol's availability and for reducing the overall cost of biodiesel plants. Besides that reusing existing carbon dioxide as a feedstock for producing chemicals has received much attention recently. In a direct carboxylation process, glycerol reacts with carbon dioxide to produce bioglycerol carbonate and water. Bioglycerol carbonate is an intermediate chemical with many potential areas of application, such as reactive protic solvent, substitute for ethylene carbonate, propylene carbonate, cyclocarbonate derivatives, solvent for battery electrolyte, filming lubricants, filming plastifiers, ingredients for cosmetics, and monomers for polycarbonates. This study presents a conceptual process design for the production of glycerol carbonate using glycerol and carbon dioxide. The carboxylation reaction uses 1 mol% of n-dibutyltinoxide (n-Bu₂SnO) as catalyst and methanol as solvent at 3.5 MPa pressure and 80oC. A 35% conversion is assumed. The unreacted reactants and catalysts were recycled and 99.6 wt% pure glycerol carbonate is obtained in the process.