Enhanced photocatalytic alkane production from fatty acid decarboxylation via inhibition of radical oligomerization

Abstract

The decarboxylation of bio-derived fatty acids provides a sustainable pathway for the production of alkane products under mild conditions; however, products are generally obtained in low selectivity due to the uncontrollable reactivity of radical intermediates. Here we demonstrate that photogenerated radicals can be rapidly terminated by surface hydrogen species during photocatalytic decarboxylation of fatty acids on a hydrogen-rich surface that is constructed by the interactions between H2 and Pt/TiO2 catalyst, thereby greatly inhibiting oligomerization; Cn–1 alkanes can therefore be obtained from bio-derived C12–C18 fatty acids in high yields (≥90%) under mild conditions (30 °C, H2 pressure ≤0.2 MPa) and 365 nm light-emitting dode irradiation. Industrial low-value fatty acid mixtures (namely, soybean and tall oil fatty acids) can be transformed into alkane products in high yields (up to 95%). Our research introduces an efficient biomass-upgrading approach that is enabled by subtle control of the radical intermediate conversion on a heterogeneous surface. The photocatalytic decarboxylation of fatty acids affords alkanes under mild conditions, albeit with limited selectivity due to radical-mediated side reactions. Now, a hydrogenated Pt/TiO2 catalyst is introduced for the selective conversion of C12–C18 fatty acids into Cn–1 alkanes in quantitative yields.