Acidic mesoporous silica for the acetylation of glycerol: Synthesis of bioadditives to petrol fuel

Expected increasing biodiesel production during the next few years will lead to an overproduction of glycerol, which is the main byproduct. The use of glycerol-based additives to improve petrol fuel properties is one of the possibilities currently being explored to utilize this renewable feedstock. In this context, sulfonic acid functionalized mesostructured materials have demonstrated an excellent catalytic behavior in the esterification of glycerol with acetic acid to yield acetylated derivates. Diacetylglycerol (DAG) and triacetylglycerol (TAG, also called triacetin) have been shown to be valuable petrol fuel additives leading to either enhanced cold and viscosity properties when blended with diesel fuel or antiknocking properties when added to gasoline. The activities and selectivities achieved using sulfonic acid functionalized mesostructured materials as catalysts are comparable or even superior to those displayed by conventional acid catalysts, providing values up to 90% of glycerol conversion and over 80% of combined selectivity toward DAG and TAG after 4 h of reaction. The acid strength of the sulfonic acid site has also been found to be an important factor affecting the catalytic performance of these materials. Moreover, these sulfonated mesostructured materials have been reused in repeated catalytic runs after a mild solvent-washing regeneration step yielding similar catalytic performance to that of the fresh catalyst. Expected increasing biodiesel production during the next few years will lead to an overproduction of glycerol, which is the main byproduct. The use of glycerol-based additives to improve petrol fuel properties is one of the possibilities currently being explored to utilize this renewable feedstock. In this context, sulfonic acid functionalized mesostructured materials have demonstrated an excellent catalytic behavior in the esterification of glycerol with acetic acid to yield acetylated derivates. Diacetylglycerol (DAG) and triacetylglycerol (TAG, also called triacetin) have been shown to be valuable petrol fuel additives leading to either enhanced cold and viscosity properties when blended with diesel fuel or antiknocking properties when added to gasoline. The activities and selectivities achieved using sulfonic acid functionalized mesostructured materials as catalysts are comparable or even superior to those displayed by conventional acid catalysts, providing values up to 90% of glycerol conversion and over 80% of combined selectivity toward DAG and TAG after 4 h of reaction. The acid strength of the sulfonic acid site has also been found to be an important factor affecting the catalytic performance of these materials. Moreover, these sulfonated mesostructured materials have been reused in repeated catalytic runs after a mild solvent-washing regeneration step yielding similar catalytic performance to that of the fresh catalyst.