(582m) Selective Dehydration of Polyols on Copper Modified BrøNsted Acid Support

Yan Cheng^1,2 and Brent H. Shanks^1,2

1. Department of Chemical and Biological Engineering, Iowa State University, Ames, IA
2. NSF Engineering Research Center for Biorenewable Chemicals (CBiRC)

Abstract

Polyols, derived from carbohydrates in biomass, are rich in hydroxyl groups, which typically need to be at least partially removed to produce commodity chemicals. In order to maintain the carbon from the starting material, dehydration is an important reaction. However, selective dehydration in the presence of multiple hydroxyl groups has received limited attention. While dehydration can be accomplished at relatively mild reaction conditions, the reaction systems tend to be challenged by rapid catalyst deactivation and low selectivity towards linear unsaturated structures compared with ether ring structures. Interesting catalysts to potentially overcome these issues are copper modified silica-aluminas, which are examined in the dehydration of model compounds. By comparing the conversion of 1,2-propanediol over a Brønsted acid, copper on silica and a copper supported Brønsted acid catalyst, we propose a reaction network for the overall dehydration reaction. The addition of copper on silica-alumina not only affects the reaction kinetics by manipulating catalyst acidity, but also introduces a new pathway for 1,2-propanediol conversion. In competition to the initial reaction step on Brønsted acid sites, this new pathway on copper reduces the interactions between hydroxyl groups, so as to inhibit the formation of ethers.