Rationally control the path of hydrodeoxygenation of palmitic acid over Ni/red-mud catalysts by surface decoration of oxophilic MoOx species

Abstract

Red mud supported Ni (Ni/RM) catalysts have been explored to the hydrodeoxygenation (HDO) of palmitic acid, however, the decarbonylation (DCO)/decarboxylation (DCO2) is dominant. Therefore, the modification the oxophilic nature of catalysts can significantly impact their path of HDO and selectivity to aim products. Herein, MoOx-decorated Ni-Mo/RM catalysts with a hierarchical flower-like micro/nanostructure were prepared and applied in the HDO of palmitic acid. The effect of MoOx addition was investigated to control the path of HDO, resulting in the changing of carbon number distribution of the product. Combined with several comprehensive structural characterizations and catalytic HDO test, it is shown that the surface defective MoOx species and FeOx species near the metallic sites could significantly facilitate the C-O bond weakening, generated more direct deoxygenation product (hexadecane). Whereas the excessive Mo loading leads to clear altering of surface chemistry (i.e., decrease of specific surface area, pore volume and Mo0 species, increase of reduction temperature and CO2 adsorption, uneven dispersion, and agglomeration of Ni species), resulting in the decrease of palmitic acid conversion. As the main oxide in RM, Fe2O3, Al2O3 and SiO2 were used as supports to load Ni-Mo bimetals respectively to explore the contribution of different components in RM to the distribution of hydrodeoxygenation products of palmitic acid.