State-of-Art of Homogeneous Molecular Catalysis for the Guerbet Upgradation of Bio-Ethanol to Fuel-Grade Bio-Butanol

Abstract

The upgradation of ethanol to n-butanol marks a major breakthrough in the field of biofuel technology, which has advantages of being compatible with existing infrastructure while simultaneously offering potential benefits in terms of transport efficiency and energy density. With its lower vapour pressure and reduced corrosiveness compared to ethanol, n-butanol is easier not only to manage but also to transport, eliminating the need for costly infrastructure changes which leads to improved fuel efficiency and reduced fuel consumption. These features positions n-butanol as a promising alternative to ethanol in the future of biodiesel. This review article delves into the cutting edge advancements in upgrading ethanol to butanol, highlighting the critical importance of this transformation in enhancing the value and practical application of biofuels. While traditional ways to make butanol rely heavily on fossil fuels, methods that employ ethanol as starting materials are dominated by heterogeneous catalysis which are limited by the requirement of high temperature and lack of selectivity. Homogeneous catalysts have been pivotal in enhancing the efficiency and selectivity of this conversion, owing to their unique mode of operation at molecular levels. A comprehensive review of the various homogeneous catalytic processes employed in the trasformation of feed-agnostic bio-ethanol to fuel-grade bio-n-butanol is provided here with a major focus on the key advancements in the catalyst design, reaction conditions and mechanism that have significantly propelled the efficiency and selectivity of these Guerbet reactions.