Conversion of lipid into high-viscosity branched bio-lubricant base oil

Abstract

To produce a high-quality bio-lubricant with similar properties compared to poly-α-olefins (PAO) lubricants, we reported herein a novel approach using sustainable and cheap lipids as a raw material, and the process involved the following tandem steps: selective hydrogenation to fatty alcohols (99% yield), dehydration of fatty alcohols to C₁₂–C₁₈ α-olefins (90% yield), and subsequent coupled polymerization–hydrogenation reactions (93% yield). A comb-type C₃₂–C₃₆ bio-lubricant was produced with an overall carbon utilization of ca. 90%. Ru₃Sn₇ alloy nanoclusters favored the adsorption of acids and esters, thereby allowing hydrogenation of the lipids to the corresponding fatty alcohols. The mixture of Lewis solid acids, such as Al₂O₃ and ThO₂, allowed for the selective dehydration of the alcohols to α-olefins. Al₂O₃ catalyzed alcohol dehydration, while ThO₂ selectively adsorbed α-olefins avoiding further isomerization. The polymerization of α-olefins and the subsequent hydrogenation steps were catalyzed by AlCl₃ and Pd/C, respectively, resulting in a branched fully-synthetic C₃₂–C₃₆ bio-lubricant. The main properties of the as-prepared bio-lubricant from coconut oil were similar to those of ExxonMobil 4T—a commercial high-viscosity PAO lubricant. This process provides a highly competitive and economic route for the conversion of abundant lipids into relevant bio-lubricant base oils.