Production of Highly Symmetrical and Branched Biolubricants from Lignocellulose-Derived Furan Compounds

Abstract

With the aim to prepare a high-performance biolubricant equivalent to poly-α-olefin, we created a T-shaped biolubricant base oil by multisite C–C coupling of small molecules containing furan rings. The aldehyde and hydroxyl groups on cellulose-derived 5-hydroxymethylfurfural (HMF) were used as active functional groups. Activated carbocations were generated via solvent-free protonation of the aldehyde and hydroxyl groups on the acid. Then, one-pot triple C–C couplings were achieved to extend the carbon chain through hydroxyalkylation/alkylation with hemicellulose-derived C8–C10 2-alkylfuran. Highly branched C30, C33, and C36 precursors with furan rings were obtained (yield: 91–93%). Side reactions included self-polymerization of alkylfuran and ring-opening isomerization of furan rings. In situ Fourier transform infrared spectroscopy and kinetic studies showed that the reaction between HMF and alkylfuran conformed to first-order reaction kinetics, with a reaction constant (k) of 0.2 min–1 and an activation energy (Ea) of 61.2 kJ/mol. The obtained precursor either underwent selective hydrogenation of the furan rings to yield a highly branched epoxy ether biolubricant or was converted into a highly branched and symmetric T-shaped full-carbon biolubricant by complete hydrodeoxygenation. This strategy provides a simple and feasible solution for the ingenious design of long-chain symmetrical biolubricant alkanes through one-pot multisite C–C coupling of small furan ring molecules starting from lignocellulose. In addition, the proposed route for the development of high-quality biolubricant base oil is highly innovative and economically feasible.

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