Photocatalyst converts fatty acids to diesel and jet-fuel molecules selectively

Industrial waste containing bioderived long-chain fatty acids could serve as sustainable feedstocks for diesel and jet fuels, which today are produced by refining petroleum sources. But several of the methods for removing oxygen from fatty acids to convert them to long-chain alkanes, the principal components of these fuels, require temperatures above 250 °C and high-pressure hydrogen, making them expensive and energy intensive. Decarboxylation methods, which convert fatty acids to alkanes by stripping carbon dioxide groups, run under milder conditions. But these methods tend to suffer from low selectivity: they generate a distribution of desirable and undesirable products. Now, Zhipeng Huang, Zhitong Zhao, and Feng Wang of the Dalian Institute of Chemical Physics and coworkers report that under mild conditions (30 °C and 0.2 MPa hydrogen) and in the presence of ultraviolet light, a Pt-TiO₂ catalyst decarboxylates fatty acids selectively (Nat. Catal. 2020, DOI: 10.1038/s41929-020-0423-3). For example, the method converted pure stearic and linoleic acids to n-heptadecane in greater than 90% yield. In tests of crude soybean and tall-oil fatty acids, which are inedible by-products of soybean processing and the pulp industry, respectively, the method produced mixtures of long-chain alkanes at up to roughly 90% yield.