Sythesis Of Macroporous Alumina And Its Application In Catalytic

Macroporous alumina is a kind of widely used material with various crystal structure and high scientific value.The most common material is used as catalyst carrier and adsorbent.The results show that in the hydrocracking process of waste lubricating oil,the control step is the macromolecule passing through the pore to the active center,so the large pore structure of the catalyst is the key to improve the catalytic cracking reaction.Therefore,the design of alumina structure is an important way to improve the catalytic performance.In this paper,a variety of preparation methods of macroporous alumina were investigated.Finally,the sol-gel method was determined as the best preparation method and the synthesis conditions were optimized.Its hydrogenation performance was tested in a microreactor during the hydrogenation of waste lubricating oil.Macroporous alumina was prepared by hydrothermal synthesis,template,precipitation and sol-gel methods.The synthesized macroporous aluminas were characterized by XRD,N₂physisorption-desorption,TG-DTG and H₂-TPD.The results show that these four synthesis methods have successfully prepared the macroporous alumina;and the synthesis process of the sol-gel method is relatively simple and economic in the four preparation methods.The synthetic conditions of the sol-gel method were investigated experimentally,and the optimal preparation conditions were determined:50ml deionized water,12.07g aluminum trichloride,4.41g polyethylene oxide?PEO?,50ml Propylene oxide and the calcination temperature was550?;The characterization results indicate that:the BET surface area of the macroporous alumina prepared by the sol-gel method can reach 352.58cm²/g.With a capacity of 1.879cm³/g,the average pore size can reach 57.54nm.It has some features such as larger specific surface area,average pore size,and more suitable pore size distribution.The Ni-Mo-Al₂O₃ catalyst was synthesized by distributed impregnation method,which using themacroporous alumina prepared by the sol-gel method as carrier.The catalyst was characterized by XRD,N₂ physisorption-desorption and other.In addition,the performance of Ni-Mo-Al₂O₃ catalyst for hydrogenation and upgrading of waste lubricating oil was investigated on a self-constructed fixed-bed microhydrogenation reactor.The results show that when the reaction temperature is 300?,the reaction pressure is 6MPa,the hydrogen-oil ratio is 300,and the airspeed is 2h^-1,the indexes of the regenerated oil reach the requirements of the lubricant and the indexes are optimal at this time.Under the optimum reaction conditions,the viscosity of the regenerated lubricating oil?40??,the freezing point and the pour point were reduced from 68.86mm²/s,-20?,and-18?to 50.3 mm²/s,-31?,and-28?.After the regeneration of waste lubricating oil,the lubricating oil has been greatly improved compared with the indexes of the waste lubricating oil after decompression distillation,indicating that the Ni-Mo-Al₂O₃ catalyst with the macroporous alumina as the carrier has good reaction performance for the hydrogenation and upgrading of waste oils.