Mo₂C/graphene nanocomposite as a hydrodeoxygenation catalyst for the production of diesel range hydrocarbons

Carbon-supported Mo₂C nanoparticles were synthesized and used as catalysts for the deoxygenation of oleic acid and soybean oil to produce diesel-range hydrocarbons. Various carbon materials, such as reduced graphene oxide (RGO), glassy spherical carbon (SC), activated carbon (AC), and mesoporous carbon (MC), were used as supports to determine the effects of RGO in the deoxygenation reactions. The effects of the flow rate, Mo content of the catalyst, and the structure of the carbon support on the conversion and product selectivity were investigated. The morphology analysis revealed that Mo₂C nanoparticles were well-dispersed onto the RGO (Mo₂C/RGO). Under moderate reaction condition (T = 350 °C, P = 5.0 MPa, H₂/oil ratio = 4.5, LHSV = 2 h^-1), oleic acid was efficiently deoxygenated using the Mo₂C/RGO catalyst, which produced hydrocarbons with ≥85% yield and ≥90% hydrocarbon selectivity. This value was much higher than those obtained using the Mo₂C/SC, Mo₂C/AC, and Mo₂C/MC catalysts (yields = 18.5-50.3%) under identical conditions. The higher catalytic activity of the RGO-supported catalyst originated from its large pore size, which facilitated transport of the reactants, and uniform deposition of the Mo₂C nanoparticles on the RGO surface. Even over a short contact time (LHSV = 8 h^-1) and using natural triglyceride as a reactant, the Mo₂C/RGO catalyst exhibited ≥40% yield of hydrocarbons, whereas a commercial CoMoS_x/Al₂O₃ catalyst produced ≥10% yield under identical conditions. The Mo₂C/RGO catalyst was highly selective toward C-O bond scission in the hydroxyl group, which produced water and hydrocarbons without truncating the carbon skeleton of the starting material. Mo₂C/RGO exhibited a prolonged catalyst lifetime for the deoxygenation of soybean oil (13% decrease in conversion after 6 h), compared with the commercial CoMoS/Al₂O₃ catalyst (42% decrease).