Hydride-mediated chemoselective C–H bond formation during benzoic acid hydrodeoxygenation on anatase TiO2

Abstract

The chemoselective hydrogenation of benzoic acid to aromatic products such as benzaldehyde, benzyl alcohol, toluene, and benzene is studied on anatase TiO₂ (001) using density functional theory (DFT) and microkinetic modeling (MKM). Oxygen vacancy (O_vac) sites are more active for benzoic acid hydrogenation than fully oxidized surface regions, with a nearly 2.5 eV lower energy for the first C–H bond formation reaction to occur near O_vac. This favorable C–H bond formation mechanism on anatase TiO₂ occurs between hydrides (H⁻) and monoanionic intermediates coadsorbed in O_vac. A steady-state microkinetic model is constructed using computed reaction energies and activation barriers to determine rates of product formation at different reaction temperatures. Product selectivities differ in distinct temperature ranges, caused by competition among reaction and product desorption steps. Sensitivity analysis shows which elementary steps significantly affect the overall benzoic acid hydrogenation activity and selectivity.