Preparation Of Titania Based Solid Acid Catalyst And Its Application In Viscosity Reduction Of Heavy Oil

Heavy oil has a large proportion of the oil and gas resources in the world, and the total resource reservoirs are approximately 1000×108 tons, which is three times more than conventional crude oil resources. With the increasing depletion of conventional crude oil reserves, heavy oil which is difficult to exploit will become the main oil resources in the future. Due to its high density and high viscosity, heavy oil is difficult to recover, transport and process. Therefore, reducing its viscosity has become one of those major technologies of solving the efficient and economic utilization of heavy oil. The aquathermolysis reaction of heavy oil, with proper catalyst added under heavy oil reservoir conditions, can reduce the viscosity underground in-situ, which not only reduces the viscosity of heavy oil permanently and irreversibly, but also upgrades heavy oil at the same time.In this paper, a series of hydrophobic metatitanic acids(H2TiO3, SiO2/H2TiO3) and zirconium doped metatitanic acids(Zr/H2TiO3, SiO2/Zr/H2TiO3) nanocatalysts are prepared by using surface modified Si O2 as the carrier. Moreover their catalytic effects on viscosity of heavy oil are investigated, and before and after reaction, the viscosity and four components(SARA) of heavy oil after aquathermolysis reaction are analyzed. Meanwhile some solid super acids(SO42-/TiO2 and SO42-/Zr/TiO2) are synthesized with traditional precipitation and impregnation method, and their catalytic performance to heavy oil is also investigated preliminarily. The main research contents and results of this paper are as follows:1. Preparation and characterization of nanocatalystsThe SiO2 supported metatitanic acids and Zr doped metatitanic acids are prepared with homogeneous precititation and hydrothermal method respectively, by using titanyl sulfate, zirconium nitrate and surface modified silica as the crude materials, also solid super acids(SO42-/TiO2 and SO42-/Zr/Ti O2) are preparedwith precipitation and impregnation method, and the formation mechanism of nanocomposite is discussed.The structure of prepared catalysts is characterized by TEM, XRD, FTIR. The supported catalysts SiO2/H2TiO3 and Si O2/Zr/H2TiO3 are hydrophobic, which are formed by H2TiO3 or Zr/H2TiO3 depositing on the surface of modified SiO2, and have better dispersion than H2TiO3 and Zr/H2TiO3. The XRD results show that all the prepared catalysts are anatase crystal, and there is no influence on the crystal structure of metatitanic acid doped with a certain amount of zirconia.2. The effect of catalyst type on catalytic reducing viscosity of heavy oilFrom the viscosity changes of heavy oil before and after the catalytic aquathermolysis reaction, what can be inferred are as follows: The viscosity reduction rate is improved with the catalyst amount increased after catalytic aquathermolysis at 150℃, while it decreases instead after the concentration of catalyst beyond 0.5%. Based on the viscosity reduction rate of heavy oil after aquathermolysis reaction at 150℃,it’s concluded that the catalytic effect of different catalysts on the viscosity reduction of heavy oil is:SiO2/Zr/H2TiO3-2> SiO2/Zr/H2TiO3-3> SO42-/TiO2> H2TiO3> SiO2/H2 Ti O3-2> SO42-/Zr/TiO2>SiO2/H2TiO3-3> Zr/H2 Ti O3. The supported catalytic SiO2/Zr/H2TiO3 composites perform better than SiO2/H2TiO3 and Zr/H2 Ti O3, which indicates that the catalytic effect of H2TiO3 can be improved by doping zirconia, and the supported catalysts have better catalytic effect compared with the unsupported catalysts.While catalytic performance of metatitanic acid don’t change obviously after supported by SiO2 carrier. The catalytic performance of solid super acid SO42-/TiO2 is stronger than SO42-/Zr/TiO2, and the SiO2/Zr/H2TiO3-2 has the best catalytic effect and makes viscosity reduction rate by 68.97% at 150℃.3. The influence of reaction conditions on catalytic viscosity reduction of heavy oilThe effects of different reaction temperature(120℃, 150℃, 180℃) and reaction time(12~72 h) on catalytic viscosity reduction of heavy oil are discussed. The results show that the H2 Ti O3 catalyst exhibitssome catalytic activity at 120℃, and has about 14% viscosity reduction rate enhanced compared with the blank experiment. The viscosity reduction rate is improved as the temperature increases, and all the catalysts have the highest reduction rate at 180℃. After aquathermolysis reaction by H2TiO3,SiO2/Zr/H2TiO3-2 and SO42-/TiO2 at 180℃, the viscosity reduction rate of heavy oil is 68.97%, 75.86% and68.97% respectively. When the reaction time is different, the viscosity reduction rate is improved as the time prolongs, and finally tends to balance. The viscosity reduction rate has little changed and reaches72.41% after 36 h reaction at 150℃ by SiO2/Zr/H2TiO3, while the viscosity reduction rate is still increasing after 72 h and reaches 68.97% catalyzed by SiO2/H2TiO3-2 and SO42-/TiO2.Meanwhile the influence of H2TiO3 and Zr/H2TiO3 catalysts on the changes of heavy oil compositions before and after the reaction at 150℃ is analyzed.The results show that the heavy components(resin and asphaltene) of original heavy oil reduce from 52.14% to 45.41% after catalytic aquathermolysis by H2TiO3.Besides, Zr/H2TiO3 and SiO2/Zr/H2TiO3-2 decrease the heavy components of heavy oil to 41.97% and41.90% respectively. SiO2/Zr/H2TiO3-2 has much better effect on viscosity reduction than Zr/H2TiO3, in spite of the approximate heavy components decomposition. This may be caused by the different cracking productions of heavy components. The content of saturated and aromatic hydrocarbons increase by 3.58%and 6.59% after being catalyzed by Zr/H2TiO3. It’s proved that catalyst Zr/H2TiO3 mainly tends to produce the aromatic hydrocarbon, while catalyst SiO2/Zr/H2TiO3-2 mainly produces the saturated hydrocarbon.And after the catalysis, the saturated hydrocarbon increases by 8.15%, while the aromatic hydrocarbon only increases by 2.09%.