Study Of Catalytic Conversion Of Waste Oil To Fuel Oil Over Composite Solid Acid Catalysts

In this study, solid acid catalysts NiMo/?-Al2O3/?-zeolite were prepared by the mechanically mixing method and conventional impregnation method, and their chemical and physical properties were characterized. Then stearic acid was used as model compound to investigate the hydrodeoxgenation activity of these catalysts. The composition of catalysts were further optimized. The optimized catalyst was used for catalytic hydrogenation of stearic acid and waste cooking oil to produce fuel oil. The optimum conditions (temperature, H2 pressure and reaction time, etc) were investigated. Studies mainly contain the following parts:Firstly, the composite carriers were prepared by mechanically mixing commercial ?-Al2O3 (A) and ?-zeolite (Si/Al=25) (b) with different A/b mass ratio and subsequent calcination process. Different amounts of NiO and MoO3 were supported on carrier by the conventional impregnation method. Then the samples were dried, tablet compressed and calcined to complete the preparation of NiMo/?-Al2O3/?-zeolite. The chemical components and physical properties of self-made catalysts were characterized by XRD, FT-IR, NH3-TPD and BET. Hydrodeoxgenation experiments of stearic acid were carried out at 350 ?,5 MPa H2 pressure for 2 h over self-made catalyst to investigate the effects of catalyst properties (A/b ratio, active sites content, acid amounts, acid strength distribution, specific surface area, etc) on hydrodeoxgenation activity of catalysts. The results reveal that the acid amounts of composite catalysts increase with increasing the content of ?-zeolite. Acid strength distribution of catalysts is affected by the content of metal oxide fraction (NiO+MoO3) (M) and the Ni/Mo ratio. The increase of acid amount results in more isomerized products. To obtain high conversion and more isomerized products, the optimized catalyst can be obtained when the A/b mass ratio is 6:4, Ni/Mo molar ratio is 3:7 and M is 20 wt%.Secondly, the effects of temperature (300 ?-350 ?), pressure (0.8-5 MPa) and reaction time (1-3 h) on catalytic conversion of stearic acid in tetralin were studied over self-made optimized catalyst (A/b mass ratio is 6:4, Ni/Mo molar ratio is 3:7 and M is 20 wt%). The results reveal that the conversion of stearic acid is significantly affected by reaction temperature. High conversions exceeding 80% were obtained when the reaction were carried out at a temperature higher than 320 ? and H25 MPa for 2h. Conversion reached to 96% at 350 ?, H2 2 MPa and 2h, and the total yield of C15-C18 alkanes and alkenes was more than 98% in products, which contained 40% isomerized compounds.Furthermore, the effects of catalytic reaction conditions (temperature, H2 pressure and reaction time) on conversion of waste cooking oil to fuel oil in tetralin, dodecane and mixture solvent (mass ratio of tetralin and dodecane was 1:1) were studied over self-made optimized catalysts (A/b mass ratio is 6:4, Ni/Mo molar ratio is 3:7 and M is 20 wt%). The results reveal that a condition: temperature at 350 ?, H2 pressure> 3 MPa and time> 3 h, is useful for transforming waste cooking oil to fuel oil. Conversion reached 99% when experiment was carried out at 350?, H23 MPa for 3h. The products mainly contained C15-C18 alkanes and alkenes, including 15% isomerized compounds. Among the three tested solvents, the mixed solvent shows better catalytic effects. High reaction temperature and low pressure are essential for tetralin to exert hydrogen donating ability.