Preparation And Application Of High Si/Al Raio Y/Kaolin Composit

In recent years, the crude oil price hikes and the feedstocks of FCC being heavier, poorer in quality. FCC is the most important secondary processing operation for the crude oil. The key to reduce production costs and improve product quality is FCC catalysts. The in situ synthesized Y zeolites can reduce production costs, but the framework Si/Al ratio of Y zeolites produced is low, which affect its catalytic performance. So investigation synthesizing high Si/Al ratio Y zeolites using kaolin is significant for industry and economics.At present, the high framework Si/Al ratio in-situ Y zeolites synthesized from kaolin microspheres as raw material are rarely reported. In this paper, both static state hydrothermal crystallization and dynamic hydrothermal crystallization were used for in situ synthesizing Y zeolites.The results show that, the poor static method leads to kaolin microspheres into powder for its bad mass transfer. And it's easy for the formation of complex crystal, such as P zeolites. The dynamic method enhanced the mass transfer, so the problems as the kaolin microspheres into powder and mixed crystal formation were solved. In the experiment, the initial Si/Al ratio, alkali dosage, the amounts of directing agent and distilled water, crystallization temperature, crystallization time were chosen to study their impacts on the framework Si/Al ratio of in-situ Y zeolites. The results show that initial feed Si/Al ratio and alkali are the most important parameters affecting the Si/Al ratio of Y zeolites. The amount of directing agent and distilled water have little affects on the the framework Si/Al ratio of Y zeolites, but have important influences on the relative crystallization of Y zeolites synthesized.Under the optimal conditions got by the orthogonal experiments, the high silica Y of Si/Al ratio up to 5.2 was synthesized. 1L amplification experiments show that the results have a good repeatability. The structure of zeolites synthesized by in-situ on kaolin microspheres such as surface topography, acidic property, pore structure was characterized by using SEM, NH3-TPD, pyridine-IR and N2 adsorption. The in-situ high silica Y zeolites were ion-exchanged by rare earth, then aging at 800℃in 100% steam for 4h. The results showed that when the framework Si/Al ratio over 4.9, the hydrothermal stability significantly improved. Kaolin matrix also played some role in the hydrothermal stability of in-situ Y zeolites. It improved the hydrothermal stability.The reaction performances of as-prepared catalysts were investigated on the micro fixed-bed reactor. The results showed that the in-situ Y zeolites with a higher framework Si/Al ratio were in favor of fluid catalytic cracking reaction. The yield of gasoline, diesel increased as the Si/Al ratio increased, and the coke and gas reduced as the Si/Al ratio increased.