Solvent-Free Methods for Making Acetals Derived from Glycerol and Furfural and Their Use as a Biodiesel Fuel Component

Abstract

The increased production of biodiesel has resulted in the overproduction of glycerol. Many researchers have begun investigating new uses for glycerol, including its conversion to fuel additives. In this paper, glycerol has been reacted with furfural to yield the corresponding acetal. This condensation reaction is carried out under neat conditions with 5-fold excess of furfural, and a number of homogeneous Lewis acids and heterogeneous solid acids as catalysts. Reactions are routinely carried out at 100 °C, allowing for yields up to 90%. The addition of a dry stream of nitrogen gas purging the headspace was found to improve yields and allowed for a reduction in the excess amount of furfural. These reaction methods are applicable to crude glycerol, affording up to 80% yield with short reaction times. The isolated acetal products can be hydrogenated, and the free hydroxyl group can subsequently be acetylated. The resulting materials have been investigated as additives to biodiesel, aiming to improve the low temperature properties. While there was no benefit to the low temperature properties, we have no evidence that would preclude the use of these materials as biodiesel additives.