Sustainable Production of Emerging Diesel Additive from Butene by Palladium-Catalyzed Alkoxycarbonylation

Pentanoic esters are a new class of biofuels (additives) and are typically produced from biomass-derived levulinic acid/esters via hydrogenation-cyclization/ring-opening/hydrogenation three-step transformations. Here, a one-step and atom-economic alkoxycarbonylation route is developed to produce pentanoic esters from widely available 1-butene. Based on the screening of 21 monophosphine and 26 diphosphine ligands, a Pd/diphosphine ligand (bis(2-diphenylphosphinophenyl) ether, DPEphos) system gives 91% yield of linear and branched ethyl pentanoate (78/22 ratio) with a turnover number (TON) up to 26100 and demonstrates outstanding recycle potential. The apparent activation energy (Ea) of 1-butene alkoxycarbonylation in the presence of this catalytic system was estimated to be 89.4 kJ/mol via kinetic measurements. More importantly, homogeneously blending 10 vol % of the resultant esters in pure diesel can improve the low-temperature fluidity and pumpability of diesel and decrease the emission of exhaust pollutants of diesel without affecting the power performance of diesel engines. Compared with pure diesel, the CO, NOx, HC, and soot emission of blend diesel at 2500 rpm are reduced by 28%, 9%, 6%, and 42%, respectively. This work provides a promising route to produce high-performance fuel additive and simultaneously broadens the comprehensive utilization of C4 olefin.