Etherification Reactions of Furfuryl Alcohol in the Presence of Orthoesters and Ketals: Application to the Synthesis of Furfuryl Ether Biofuels

Strategies for the efficient transformation of abundant and sustainable bioderived molecules, such as furfuryl alcohol (FAlc), into higher value products are currently a vibrant research area. Herein, we demonstrate that furfuryl ethers, which are of significant interest as biorenewable fuel additives, are efficiently produced employing an etherification reaction of furfuryl alcohol and short chain alkyl alcohols in the presence of a recyclable ZSM-5 catalyst and an orthoester, such as trimethyl orthoformate (TMOF) or triethyl orthoformate (TEOF), used as a sacrificial reagent. These etherification reactions proceed at temperatures significantly lower than those of the previous etherification procedures, and they provide the furfuryl ether products in high yield. Importantly, the low temperature employed improves the selectivity by minimizing the formation of hydrolysis products and the competing polymerization reactions leading to humin byproducts. By carrying out the reaction in higher alcohol solvents, such as ethanol, 1-propanol, and 1-butanol, we are able to capitalize on the ability of ZSM-5 to catalyze the orthoester exchange reaction of TMOF or TEOF to produce the corresponding furfuyl ethers in a novel, telescoped orthoester exchange–etherification reaction sequence. Finally, we also demonstrate that the etherification reaction proceeds efficiently in the presence of acetals and ketals, such as dimethoxypropane and diethoxypropane. This latter development is highly significant given the greater scope for the regeneration of acetal and ketal reagents.