Preparation Of Zr Modified Small Particle Y Zeolite And Its Application In Hydrocracking

As an effective means of lightening heavy oil,hydrocracking has played an increasing role in the petrochemical industry.The cracking active component of hydrocracking catalysts commonly used in industry is Y zeolite,but Y zeolite has the problems of large acid density and narrow pores,which leads to many problems such as poor stability of hydrocracking catalyst activity and poor product selectivity.Therefore,the preparation and optimization of small particle Y zeolites were proposed to provide a material basis for the preparation of highly active and selective hydrocracking catalysts.Firstly,Y zeolites with different ratios of silicon to aluminum and different average particle sizes were prepared by adjusting the alkalinity in the Y zeolite synthesis system and the aging time of the directing agent.The experimental results show that the alkalinity in the Y zeolite synthesis system has a greater impact on the silicon-aluminum ratio of the Y zeolite.Under the condition of the synthesis system's alkalinity of 6.6,the siliconaluminum ratio of the synthesized Y zeolite is 5.1.At the same time,the aging time of the directing agent is closely related to the average particle size of the Y zeolite.The aging time of the directing agent is between 12 and 24 h,and the average particle size of the Y zeolite is 400 to 800 nm.The hydrocracking reaction results of the catalyst prepared by using Y zeolite as the acidic component show that the Y zeolite catalyst with higher ratio of silicon to aluminum and smaller particle size has higher hydrocracking activity(conversion rate)and liquid product yield.The selectivity of middle distillate product is significantly higher than that of comparative industrial Y-based zeolite catalyst.Secondly,the effect of Y zeolite modification method on its related physical and chemical properties and catalyst performances was further investigated.Based on Y zeolites with different Zr modification methods(impregnation method,ion exchange method and in-situ synthesis),the effects of Zr modification methods and Zr contents on the acidity and pore structure of Y zeolites were investigated,and using Zr Y-ASA as the carrier,a series of supported Ni W hydrocracking catalysts were prepared,and the results of hydrocracking reaction using n-hexadecane as raw material show that the acid contents and pore structures of Zr-modified Y zeolites have great changes,the Zr-modified Y zeolite catalysts have greatly improved the selectivity of intermediate components compared with industrial Y-based zeolite catalyst.Among them,the in-situ modified Y zeolite catalyst has improved the selectivity of intermediate products by nearly 14% under the same reaction conditions.