| The demand for petroleum increased on the rapid development of the global economy. Petroleum is an unrenewable resource, so, developing renewable resources has important implication for substituting for petroleum. Diesel is one of petroleum products. It is shown that the research of alternative fuel focuses on transesterification reaction for preparation of biodiesel, and the limited research for catalytic hydrogenation of oil and fat. Green diesel is a new type fuel with oil and fat or illegal cooking oil as feedstocks, the properties of catalysts and modified of products are key factors in green diesel industry. This study achieved the transformation/utilization of used frying oil (UFO) through preparing green diesel by using hydrogenation catalyst with UFO as raw material.The UFO was collected, and the method of separation impurity removal, degumming, decoloration and dehydration were used for pretreating of UFO. Response surface methodology (RSM) based on single-factor experiments were applied for the optimization of oil decoloration process of UFO and the optimal scheme was obtained. The appropriate reaction condition:reaction temperature is 104℃, reaction time is 46min, stirring speed is 300r/min, decolorising agent is 16wt%, decolourization ratio of UFO is 75%. Comparing with the UFO and pretreatment UFO, the acid value from 18.7mg KOH/g to 15.2mg KOH/g, the moisture from 0.75% to trace, the phosphatide content from 1.47% to 0.12%, and the transparency from 92% to 98%, The test results showed that they can meet the requirements of reaction application.The reaction rule of the sulfided NiMo/Al2O3 and CoMo/Al2O3 catalysts and reaction conditions on the conversion and target yield of the Pretreating UFO were studied in laboratory-scale fixed-bed reactor. The chemical and physical properties of hydrogenated products were studied, the products showed high cetane numbers (>90) and good blending properties for using. The products showed high sulfur-content (>40 mg/Kg) and the cold filter plugging point (CFPP) didn’t meet EN590 standards, which should be processed further to modification.The use of sulfided catalyst results in sulfur-contaminated fuel, and the study of non-sulfided catalysts are necessary. The hydrodeoxygenation of pretreatment UFO over a reduced NiMo/Al2O3 and CoMo/Al2O3 catalysts were studied. The effects of reaction temperature, reaction pressure and liquid hourly space velocity (LHSV) on the conversion and target yield were investigated. The catalyst was activated by reduction.Through research of the reaction products, results showed that utilization of the reduced catalyst for coping with the lack of sulfided catalyst, the products showed low sulfur-content (<1 mg/Kg) and high isoparaffin ratio, the products obtained had better CFPP values.NiMoLa/Al2O3 catalyst was prepared by impregnation. The morphology, structure, and composition were investigated by series modern analysis technologies. The influences of reaction temperature, reaction pressure, liquid hourly space velocity (LHSV) and hydrogen/oil feed ratio (H2/oil) on the conversion and target yield were studied, they showed that pretreated UFO could be effectively hydrotreated over NiMoLa/Al2O3 catalyst to obtain high paraffinic products at a temperature range (340-360℃), pressure (4.0Mpa), LHSV (1.5h-1), and H2/oil (100Nm3/m3). Activity of catalyst kept high active during 200h reaction time. The reaction routes were studied depend on NiMoLa/Al2O3 catalyst, in the first step of this routes the triglyceride is saturation, in the second step of this routes the triglyceride is decomposing, in the third step of this routes the fat acid is hydrodecarboxylation, hydrodecarbonylation, and hydrodeoxygenation, the fourth step of this routes the paraffin is hydrocracking and isomerization. Furthermore, the methanation and WGS existed in gas products processes.The suitability and endurance of NiMoLa/Al2O3 catalyst was studied by using various type feedstocks. Products were analyzed by measuring chemical and physical properties, gas chromatography and infrared spectrum, it showed that catalyst was high endurance of fat acid, and had some catalytic effect in the presence of both alkali metals and phospholipid in the feedstocks, however, the catalyst was low endurance in the presence of either alkali metals or phospholipid in the feedstocks. The tests of catalytic reaction showed that NiMoLa/Al2O3 catalyst had good suitability on various type feedstocks.Finally, the chemical and physical properities of products were measured and improved, and then comparison with 0# diesel,-20#diesel and EN590 standard. The products showed high cetane numbers (93), low acid value (<0.1mg KOH/g) and low sulfur-content (<1 mg/Kg). Research result showed that the content of isoparaffin in products is 11.3-15.4%, the products obtained had poor low temperature characteristics and high CFPP values. The effects of the three different flow improvers (pour point depressant A, pour point depressant B and Keroflux 6226) and blends with fossil diesel on cold flow properties were investigated. The results showed that both methods respectively all had improvement effects against cold flow properties of the products. The condensation point (CP) of -20# diesel containing 5-30wt% hydrogenated diesel increased -14℃ from -20℃, and the CFPP values increased -3℃ from -14℃. The blended fuel containing 30wt% hydrogenated diesel was studied. The effects of the three different flow improvers on cold flow properties of the blended fuel were investigated. The results showed that the Keroflux 6226 had the best results, and the CP values of blended fuel with 0.25%o of addition decreased-30℃ from -14℃, the pour point depressant B had the worst results, and the CP values of blended fuel with 1.0%o of addition decreased -28℃ from -14℃. The effect of improving CFPP values was less obvious than improving CP values. |
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