Improvement of Ethanol Guerbet Condensation by Acetal Hydrolysis

The Guerbet condensation of bio-ethanol is a green route to the synthesis of n-butanol. However, this route suffers from its by-product water which not only affects adversely the condensation reaction performance, but also causes the deactivation of the catalyst. Hence, the water by-product should be removed. This goal is achieved by integrating the Guerbet condensation of ethanol with acetal hydrolysis in this work. First, the Guerbet condensation of ethanol and the integrated reaction of ethanol Guerbet condensation with acetal hydrolysis were thermodynamically analyzed. The results showed that acetal hydrolysis can promote the Guerbet condensation of ethanol. Then the performance of the two reaction systems was compared experimentally using Ni–Cu/TiO2 catalyst. The selectivity of n-butanol reached 44.4% at an ethanol conversion of 47.9% in ethanol Guerbet condensation while the selectivity of n-butanol increased to 50.4% at an ethanol conversion of 50.2% in the integrated reaction with an ethanol/acetal molar ratio of 20. Finally, the two reaction systems were kinetically analyzed, and the results showed that acetal hydrolysis can lower the activation energy of the ethanol dehydrogenation step and acetaldehyde aldol self-condensation step, thus effectively promoting the Guerbet condensation of ethanol.