Catalytic coproduction of renewable lubricant base oils and diesel fuels from bio-lipids and aromatics via alkylation and hydrodeoxygenation

Abstract

The production of alkane-based lubricants and diesel fuels from bio-lipid resources represents a promising and sustainable pathway toward achieving carbon neutrality. In this study, we propose a novel catalytic strategy for the co-production of renewable lubricant base oils and diesel fuels from palm oil and aromatic compounds through a tandem process involving alkylation and hydrodeoxygenation (HDO), achieving a high total product yield of up to 77 wt%. HY(30) exhibited excellent performance in the alkylation of palm oil with aromatics to form aryl palm oil intermediates, which can be attributed to its large specific surface area, suitable pore size distribution, and the presence of an optimal density of Brønsted acid sites. Subsequently, a Ni-ReO_x/SiO₂ catalyst was developed for the HDO of the aryl palm oil, yielding C₂₃–C₂₇ cycloalkyl branched alkanes (CBALs) as lubricant base oils and C₁₅–C₁₈ linear alkanes as diesel fuels. Structural characterization studies revealed that the Ni-ReO_x/SiO₂ catalyst features ReO_x species partially covering the Ni-Re alloy and also dispersed on the support. The outstanding HDO activity of the Ni-ReO_x/SiO₂ catalyst is primarily attributed to the synergistic interaction between the partially reduced ReO_x species and the Ni–Re alloy phase, which enhances the adsorption, activation, and cleavage of C–O bonds during the reaction. Mechanistic studies elucidated that the dominant reaction pathway for the HDO of aryl esters involves benzene ring hydrogenation and acyl C–O bond hydrogenolysis, followed by decarbonylation, leading to the formation of alkanes with one fewer carbon atom. Both the HY(30) and Ni-ReO_x/SiO₂ catalysts demonstrated good recyclability. The proposed catalytic strategy for synthesizing renewable lubricant base oils and diesel fuels offers a viable and sustainable alternative to conventional petroleum-derived products, contributing to the reduction of greenhouse gas emissions.