Preparation Of Modified Bentonite-Based Acid And Its Catalytic Hydrogenation Of Jatropha Oil To Biodiesel

With gradual improvement of global economy and ever increasing material needs of the masses, human beings demand for fossil energy is growing, which causes shortage of petrochemical energy in the worldwide. Faced with the shortage of fossil energy and environmental pollution caused by the use of fossil energy, human begin to study and pay close attention to the clean and renewable new energy. The research about biodiesel which is extensive, renewable and environment-friendly, is conducive to reduce the dependence of fossil energy. Therefore, biodiesel has became a hot spot to scientists today. The molecular structure and performance of the second generation biodiesel is similar to traditional petrochemical diesel. Preparation of the second generation biodiesel through hydrodeoxygenation of grease, has the merits of low pollutants emission, high calorific value, etc. The second generation biodiesel is a green energy owning broad development prospective.With modified bentonite used as supporter, sulfurated NiMo/activated clay catalyst and reduced Ni/Al2O3/ZrO2/bentonite catalyst were prepared. Their catalytic performance was investigated through catalytic hydrogenation of jatropha oil. The load amount of active components and optimum process conditions for preparation of above catalysts were determined, and the reaction mechanisms of catalysts were discussed. Catalysts were characterized by N2 adsorption and desorption, XRD, SEM, EDS, NH3-TPD, Py-FTIR for studying their struction characteristics. Finally, to ascertain the best reaction conditions, sulfurated NiMo/activated clay catalyst and reduced Ni/Al2O3/ZrO2/bentonite catalyst were applied to catalyze hydroprocess reaction of jatropha oil. The main results of research were as follwos:(1) Under the conditions of NiO load 12% and MoO3 load 14%, sulfurated NiMo/activated clay catalyst showed the best catalytic activity, and catalyst’s optimum preparation conditions were as follows:calcination time was 175 min; calcination temperature was 450 ℃; sulfuration temperature was 320 ℃; sulfuration time was 60 min; dosage of vulcanizer was 16 mol·mol-1; initial hydrogen pressure of sulfide was 3 MPa. The reaction pathway of sulfurated NiMo/activated clay catalyzing hydrogenation process of jatropha oil could be proceed in four steps:(a) hydrogenation of triglyceride’s C=C bonds (b) successive P-elimination and hydrogenation of saturated triglyceride generating propane and free fatty acids (c) decarbonylation/decarboxylation of fatty acids generating straight-chain paraffins (d) through isomerization, cracking and cyclization of straight-chain paraffin forming isoolefine, shorter hydrocarbons, cyclane and other compounds. Through N2 adsorption and desorption, SEM, EDS, XRD, Py-FTIR, NH3-TPD, it was observed that compared with activated clay, the pore volume and specific surface area of NiMo/activated clay significantly reduced, N2 isothermal adsorption and desorption curve of NiMo/activated clay belonged to the type IV, the hysteresis loop type belonged to the type H3. NiMo/activated clay with rough surface arranged disorderly and closely, the particle diameter of NiMo/activated clay was 0.5～2 μm, NiO and MoO3 were successfully loaded on supporter, Bronsted acid and Lewis acid both existed on the NiMo/activated clay surface, weak acid site and medium acid site both existed on the NiMo/activated clay surface, and the amount of weak acid was slightly larger than medium acid. The optimal process conditions of sulfurated NiMo/activated clay catalyzing hydrogenation process of jatropha oil were as follows:reaction temperature was 300℃; catalyst dosage was 7.5 wt%; initial hydrogen pressure of reaction was 3.5MPa; reaction time was 60 min. Under the best conditions, the conversion of jatropha oil was 95.19% and the selectity of C15-C18 was 84.53%. The effectively regeneration way of deactivated sulfurated NiMo/activated clay was roasting-sulfide method.(2) Under the conditions of Ni load 19%, Al2O3 load 5% and ZrO2 load 13%, Ni/Al2O3/ZrO2/bentonite catalyst showed the best catalytic activity, and optimum preparation conditions for catalyst were as follows:CTAB dosage was 6%; calcination time was 240 min; calcination temperature was 550℃; reduction temperature was 400 ℃; reduction time was 180 min. The reaction pathway of Ni/Al2O3/ZrO2/bentonite catalyzing hydrogenation process of jatropha oil could be proceed in four steps:(a) hydrogenation of triglyceride’s C=C bonds (b) successive β-elimination and hydrogenation of saturated triglyceride generating propane and free fatty acids (c) hydrodeoxygen and decarbonylation/decarboxylation of fatty acids generating straight-chain paraffin (d) cracking and cyclization of straight-chain paraffin forming shorter hydrocarbons, cyclanes and other compounds. Through N2 adsorption and desorption, SEM, EDS, XRD, Py-FTIR, NH3-TPD, it was observed that compared with organobentonite, the pore volume and specific surface area of NiO/Al2O3/ZrO2/bentonite markedly increase, N2 isothermal adsorption and desorption curve of NiO/Al2O3/ZrO2/bentonite belonged to the type IV, the hysteresis loop type belonged to the type H3, NiO/Al2O3/ZrO2/bentonite was fragmented material with smooth surface and lossen structure, NiO were successfully loaded on supporter; Bronsted acid and Lewis acid both existed on the NiO/Al2O3/ZrO2/bentonite surface; weak acid site and medium acid site both existed on the NiO/Al2O3/ZrO2/bentonite surface, and the amount of medium acid was larger than weak acid. The optimal process conditions of Ni/Al2O3/ZrO2/bentonite catalyzing hydrogenation process of jatropha oil were as follows:reaction temperature was 300℃; catalyst dosage was 7.5 wt%; initial hydrogen pressure of reaction was 3MPa; reaction time was 120 min. Under the best conditions, the conversion of jatropha oil was 78.61% and the selectity of C15-C18 was 73.61%. Ni/Al2O3/ZrO2/bentonite regenerated by calcination-reduction method has better catalytic activity than that regenerated by calcination method.