Reactivation Of Spent Catalytic Cracking Catalysts

The fluid catalytic cracking(FCC)is the core technology to obtain light oil,and also the secondary processing of crude oil with the the largest amount of catalyst consumed and wasted.The treatment of spent FCC catalysts becomes imminent because of the potential hazards of spent catalysts to the environment.And reactivation is the ideal path for disposal of spent catalysts.Currently,the magnetic separation method does not has a high reactivation efficiency.Besides,the high cost limits its use in application.As for chemical reactivation,it has the disadvantage of using a large amount of organic acids.Therefore,exploring new methods to reactive spent catalysts is of great significance to the environmentally friendly production of FCC.In this thesis,the reactivation of spent FCC catalysts is based on chemical reactivation method using less organic reagents,and its catalytic activity recovered through the structural reconstruction of the spent catalyst.The pore structure,acidity,and activity of the spent catalysts were recovered in a inorganic acid system.The effect of concentration of inorganic acid,reaction temperature,and reaction time on the porosity and acidity is characterized by means of nitrogen adsorption/desorption,X-ray diffraction,ammonia temperature programmed desorption,and pyridine adsorption infrared spectroscopy.The experimental results show that the inorganic acid reactivation method can reconstruct the structure of spent catalysts,increase specific surface area and pore volume,but the acid properties of the catalyst are difficult to control.In view of the limitations of the inorganic acid reactivation method,a single organic acid and inorganic-organic acid composite system is used to reactive the spent catalysts and optimize the conditions of reactivation.The experimental results show that the organic acid can reconstruct the structure of spent catalysts,increase specific surface area and pore volume.Compared to inorganic reactivation,the concentration of medium acid sites increases.In order to reduce the amount of organic acids used to reduce the cost of reactivation,this thesis use inorganic-organic acid composite system to reactive the spent catalysts.The use of the compound acid to reactive not only increases the specific surface area and pore volume of the reactivated samples,but also increases the proportion of medium acid significantly compared with the samples obtained by inorganic acid reaction method.Reactivated catalysts have high specific surface area,well-developed pore structure,and rich medium acid site because of structural reconstruction of the spent catalysts.In addition,hydrothermal stability increases.It is worth mentioning that the cracking performance of the reactivated samples is significantly improved.Compared with the samples obtained by the inorganic acid reactivation method,the catalysts reactivated by organic acid or composite acid have higher conversion of VGO and total liquor yield.Moreover,the samples reactivated by composite acid have better selectivity of light oil,the yield of light oil approach 58.3 %.