Hydrotreatment of Vegetable Oils to Produce Bio-Hydrogenated Diesel and Liquefied Petroleum Gas Fuel over Catalysts Containing Sulfided Ni–Mo and Solid Acids

Biohydrogenated diesel (BHD) and liquefied petroleum gas (LPG) fuel were produced by the hydrotreatment of vegetable oils over Ni–Mo-based catalysts in a high-pressure fixed-bed flow reaction system at 350 °C under 4 MPa of hydrogen. Because triglycerides and free fatty acids underwent the hydrogenation and deoxidization at the same time during the reaction, various vegetable oils (jatropha oil, palm oil, and canola oil) were converted to mixed paraffins by the one-step hydrotreatment process although they contained quite different amounts of free fatty acids. Ni-Mo/SiO 2 formed n -C 18 H 38, n -C 17 H 36, n -C 16 H 34, and n -C 15 H 32 as predominant products in the hydrotreatment of jatropha oil. These long normal hydrocarbons had high melting points and thus gave the liquid hydrocarbon product over Ni-Mo/SiO 2 a high pour point of 20 °C. Either Ni-Mo/H-Y or Ni-Mo/H-ZSM-5 was not suitable for producing BHD from jatropha oil because a large amount of gasoline-ranged hydrocarbons was formed on the strong acid sites of zeolites. When SiO 2 -Al 2 O 3 was used as a support for the Ni-Mo catalyst, the pour point of the liquid hydrocarbon product decreased to −10 °C by converting some C 15 –C 18 n -paraffins to iso -paraffins and light paraffins on SiO 2 -Al 2 O 3 . Because SiO 2 -Al 2 O 3 had a proper solid acidic strength, both the chemical composition and the pour point of liquid hydrocarbon product over Ni-Mo/SiO 2 -Al 2 O 3 were similar to those of a normal diesel bought from a petrol station. Meanwhile, the glycerin groups in the vegetable oils were converted to propane over Ni-Mo/SiO 2 -Al 2 O 3 by the hydrogenation and deoxidization. Therefore, the liquid hydrocarbon product can be directly used as a BHD fuel for the current diesel engines, and the gas hydrocarbon product can be used as a liquefied petroleum gas (LPG) fuel in the hydrotreatment of vegetable oils over Ni-Mo/SiO 2 -Al 2 O 3 .