One-Pot Synthesis of Valeric Biofuels via Esterification–Hydrogenolysis

The production of valerate esters, a class of transportation biofuels (additives), usually undergoes alternate hydrogenation and acid-catalysis dehydration processes that suffer from inevitable coke deposition and undesirable side reactions. We report a one-pot esterification–hydrogenolysis reaction pathway for valeric biofuels synthesis from biomass-derived 2-furoic acid, which was proceeded over the elaborate CoPtX@Co3O4-NC (X = 0.01, 0.02, 0.05, and 0.1) catalysts. The catalysts were constructed through a MOF-engaged etching-pyrolysis-replacement strategy to obtain mesoporous pocket cube nanoboxes-in-nanobox morphology and uniform CoPtX@Co3O4 core–shell nanoparticles with Pt moieties in tunable content and size (from single-atom scale to 2.4 nm). The obtained acid-free CoPtX@Co3O4-NC catalyst achieved an average 92.2% yield of ethyl valerate at a complete conversion of 2-furoic acid, and the reaction ran steadily in a microchannel continuous flow reactor for at least 200 h, which also inhibited the byproduct generation and coke deposition. A mechanistic study suggested that 2-furoic acid was preferably adsorbed on the oxyphilic Co3O4 shell for esterification initially; then the generated esters underwent sequential and exclusive hydrogenolysis steps over the CoPt core to yield valerate esters. The high industrial application prospect of this reaction pathway was additionally highlighted by producing 12 kinds of valeric biofuels from 2-furoic acid and the corresponding C1 ∼ C7 primary, secondary, and tertiary alcohols.