Hydrodeoxygenation of stearic acid over Co-Mg-Al-O mixed oxide catalysts

The influence of the Co/Mg molar ratio on the physicochemical and catalytic properties of Co-Mg-Al-O mixed oxides obtained by thermal treatment of layered double hydroxides (LDH) was investigated. Characterization of the mixed oxides by ICP, XRD, and TPR revealed that the catalysts form solid solutions with well-dispersed cobalt particles, where increasing cobalt content weakens the interaction between Co and spinel, promoting the formation of larger Co3O4 crystallites and decreasing the cobalt reduction temperature. With increasing Co/Mg ratio, the conversion of stearic acid and the yield of C15–C18 hydrocarbons increased. The conversion of stearic acid to hydrocarbons proceeds through the formation of intermediate products–1-octadecanol and stearyl stearate–whose proportion increases with higher catalyst calcination temperature, indicating the key role of the hydrogenation metal in the conversion pathway. Complete conversion of stearic acid with heptadecane as the main product is achieved using a catalyst with a Co/Mg molar ratio of 3 at 270 °C and 4 MPa hydrogen pressure. The possibility of oxidative regeneration of this catalyst and its multi-cycle reuse was demonstrated.