Nitrogen-rich carbon-supported ultrafine MoC nanoparticles for the hydrotreatment of oleic acid into diesel-like hydrocarbons

Abstract

The hydrotreatment of lipids is regarded as a renewable and promising approach to produce green diesel to confront environmental issues. The molybdenum carbide catalyst displays noble metal-like activity for lipid hydrotreatment; however, the active sites on the catalyst typically have a large particle size and are unevenly dispersed, thereby severely limiting its catalytic performance. Herein, ultrafine MoC nanoparticles supported on nitrogen-rich carbon (MoC/CN) were prepared, and their activity for the hydrotreatment of oleic acid was compared with that of Mo2C supported on mesoporous carbon (Mo2C/MC). In the hydrotreatment test, the MoC/CN catalyst exhibited remarkable activity with 94.3% conversion and 90.3% selectivity at 310 °C; these values were much higher than those of the Mo2C/MC catalyst (84.8% and 70.1%, respectively), even at 350 °C. The excellent performance of MoC/CN is ascribed to the sufficient amounts of pyridinic N and pyrrolic N in nitrogen-rich carbon, which provide anchoring sites for the molybdenum precursor, leading to the fine particle sizes of the active sites and a uniform dispersion. The density functional theory (DFT) calculations show that MoC/CN can better facilitate the dissociative adsorption of hydrogen than Mo2C/MC, which explains the high activity of the Mo2C/MC catalyst in the hydrotreatment reaction. The carburization temperature and Mo loading content have a considerable effect on the MoC formation and surface area of the MoC/CN catalyst and thus greatly influence the catalytic activity. Moreover, the hydrotreatment conditions, including the reaction temperature and hydrogen pressure, were also investigated.