Advanced diesel from ethanol: a pathway to produce sustainable and high-quality drop-in biofuels

Abstract

In this work, we develop a novel technology for the transformation of ethanol into diesel via Guerbet coupling and etherification. Our strategy overcomes the limitations of previous studies, namely, the low yield of diesel #2, and the complex separation network required. To overcome these limitations, we rely on the use of hydrogenolysis for the removal of esters, and the implementation of butanol recycling. Herein, we present a thorough analysis of this strategy integrating the experimental evaluation of catalysts for the involved reactions, process synthesis, technoeconomic analysis, lifecycle analysis, fuel property modelling, and characterization of the fuels produced in a diesel engine. In contrast to other catalytic strategies, in this work diesel #2 constitutes the main product (92% of the produced fuels). The diesel produced has excellent cold flow properties (cloud point ∼ −28 °C) and a very high cetane number (∼94) while satisfying flash point requirements. A technoeconomic analysis leads to a minimum fuel selling price (MFSP) between $4.6–8.4 per GDE for ethanol prices between $1.5 per gal and $3.4 per gal (in 2021 dollars). Depending on the carbon intensity of the ethanol used as feedstock, and the energy consumption of the process, we found that reductions >70% in GHG emissions are feasible in comparison with fossil diesel. The diesel fuel can become carbon negative if an ethanol feedstock with a sufficiently low carbon footprint is used and the ethanol upgrading biorefinery uses renewable hydrogen and produces steam using renewable natural gas.