(77b) Reactive Distillation Process for Glycerol Ethers Production

Glycerol is produced as by-product of biodiesel production in amounts that are equivalent to approximately 10 % wt. of the total product. As a result to the increasing availability, the market price of glycerol has dropped rapidly and new uses for glycerol need to be found. Di- and tri-ethers of glycerol are compounds soluble in diesel and biodiesel, improving the quality of the fuel. They diminish the emissions of particulate matter, carbon oxide and carbonyl compounds and decrease the cloud point of diesel fuel when combined with biodiesel. Therefore, ethers of glycerol are interesting alternatives to commercial oxygenate additives.

In this contribution, we demonstrate the feasibility of a reactive distillation process for production of glycerol ethers by etherification of glycerol with iso-butene catalyzed by heterogeneous acid catalysts, such as Amberlist 35. The process is performed in a reactive distillation column, with few un-reactive trays placed above and below the reactive zone. Glycerol is fed as liquid at the top of the reactive zone. Iso-butene enters in the column as a vapor stream at the bottom. The bottom product contains the di- and tri-ethers of glycerol which are the main products. The vapor outlet stream contains the mono-ether and the excess of iso-butene, which are separated in a decanter. The mono-ether is returned as reflux, while the excess of iso-butene is recycled. The detailed design is performed using AspenPlus. The stability and robustness in operation is checked using rigorous dynamic simulation in AspenDynamics.