Lubricants
Research goal: This thrust focuses on innovative technologies that target new performance-advantaged bio-products. We develop sustainable, durable and high-performance bio-lubricants from inexpensive and sustainable renewables, including non-food biomass and fat, natural oils or waste cooking oils.
Approach: Develop various selective C-C coupling reaction chemistries via a slate of catalysts to build the carbon chain length starting from furans and long-chain functionalized molecules, such as fatty acids or their derivatives. Control with precision the number of carbons, the degree of branching and the stereospecificity of the resulting molecules. Scale up production. Evaluate typical performance metrics, such as viscosity index, pour point, volatility, and stability, of virgin (without additives) bio-lubricants relative to those of commercial, high-performance, additives-containing lubricants.
Learn more about lubricants
Lubricants represent a ~$61 billion global market at an annual consumption of 40 million tons. They have numerous applications in industrial machineries, automotive engines, agricultural equipment, aviation machinery, hydraulic fluids, hydropower, and transformers. Petroleum-based lubricants consist of C20-C50 molecules and are formulated with additives. The high volatility of low-carbon fractions causes thickening over time, requiring frequent lubricant replacements. High-performance applications under extreme conditions (e.g., in gas turbines and nuclear reactors) demand rigid specifications (e.g., low pour point, high thermal stability, low volatility, and high viscosity index). Synthetic, branched poly-alpha-olefin lubricants produced by olefin oligomerization meet some specifications, but selectively tuning their size and architecture is challenging. Use of less expensive, sustainable, and versatile carbon feedstocks to produce lubricants with controlled size and molecular architecture, and a narrow molecular weight distribution can improve lubricant properties and avoid complex formulations and high cost.
Research highlights
We have developed novel synthesis strategies to produce three broad classes of bio-lubricants from inexpensive and sustainable non-food biomass and natural oils or waste cooking oils. Yields ranging from 80 to over 90% have been achieved. These molecules contain furan rings, or fully saturated furan rings, or fully deoxygenated branched alkanes. Importantly, we can control with precision the number of carbons, the molecular structure, the degree of aromaticity and the oxygen level. Our carbon-carbon coupling synthesis strategies include: (1) acylation of furan; (2) hydroxyalkylation/alkylation of 2-alkylfurans with aldehydes; (3) conjugate addition-hydroxyalkylation/alkylation (CA-HAA) of 2-alkylfurans with enals; and (4) ketonic decarboxylation of fatty acids followed by aldol condensation. The derived furan-based lubricants can be further upgraded via hydrogenation or hydrodeoxygenation. New, inexpensive metal oxide on metal hydrodeoxygenation catalysts have been developed. The properties of these bio-lubricants are on par with or better than those of commercial mineral oils and synthetic lubricants.
We have introduced a novel, two-step strategy to synthesize benzene and branched cyclic alkane lubricant base-oils from lignin-derived guaiacol and lauryl aldehyde (produced from natural oils or biomass). The reaction pathway involves carbon–carbon coupling through Brønsted acid-catalyzed hydroxyalkylation/alkylation (HAA), followed by hydrodeoxygenation (HDO). We optimized the reaction conditions to achieve a maximum guaiacol conversion of 90%, with a product consisting of 70% benzene lubricant, 22% aldol condensation side products, and 8% unreacted guaiacols. Subsequent HDO of the products over Ir-ReOx/SiO2 produced a lubricant-ranged mixture of cyclic and branched alkanes (C24), at 82% yield, and small fractions of dodecyl cyclohexane and C-C cracked alkanes with carbon numbers between C15 and C10. Quantification of viscosity properties (kinematic viscosity, viscosity index, and Noack volatility) indicated that the synthesized biobased lubricant base-oil was comparable to commercial petroleum-derived poly α-olefin Group III, IV, and refrigerant base oils. This approach provides a unique pathway for upgrading lignin-derived monomers into replacements of petroleum-derived base oils. We are expanding to additional lignin-based paths to lubricants and replace fatty acids with sugar-derived molecules.
