Ni(OH)x/Ni-Catalyzed In Situ Hydrogenation and Ethanol Ethoxylation of 2-Methylfuran for Renewable Biofuel Co-Upgrading.

Bioethanol and furanics are currently prevailing additives to fossil-based transportation fuels. With the objective to lift the longstanding limitations of these biofuel additives, this work reports for the first time the synthesis of 2-ethoxy-2-methyltetrahydrofuran (2-EO-2-MTHF) as a co-upgraded fuel by reacting ethanol with 2-methylfuran (2-MF). The formation of 2-EO-2-MTHF is achieved through ethanol ethoxylation of 2-MF, enabled by a reverse Ni(OH)x/Ni catalyst under hydrogen pressure. Nickel hydroxide species over the Ni nanoparticles play a crucial role in activating ethanol and polarizing the partially hydrogenated dihydrofuran intermediates, favorably steering the reaction selectively toward the ethoxylation product. The reaction conditions, including pressure and temperature, are systematically optimized to enhance the yield of 2-EO-2-MTHF, and provide a means to beneficially tune the fuel compositions consisting mainly of 2-EO-2-MTHF and 2-MTHF, both are high energy density molecules. Importantly, the reverse Ni(OH)x-Ni catalyst allows a one-pot process to accomplish consecutive partial hydrogenation of 2-MF and ethanol ethoxylation. This work provides a practical strategy for upgrading biomass-derived polar primary fuel molecules into more versatile fuels and chemicals.