Tetrabutylphosphonium bromide catalyzed dehydration of diols to dienes and its application in the bio-based production of butadiene

We report the use of the ionic liquid tetrabutylphosphonium bromide as a solvent and catalyst for dehydration of diols to conjugated dienes. This system combines stability, high reaction rates and easy product separation. A reaction mechanism for the model compound 1,2-hexanediol is proposed and experimentally corroborated. This particular mechanism allows for the selective formation of conjugated dienes, in contrast with purely acidic catalysis. Next, the reaction is also performed on various other diols. As a first application, we assessed the bio-based production of 1,3-butadiene. Starting from 1,4-butanediol, a 94% yield of butadiene was reached at 100% conversion.status: publishe