Modification And Catalytic Performance Evaluation Of Small-size NaY Zeolite With High Silicon Aluminium Ratio

Fluid catalytic cracking (FCC) is the main method of secondary deep processing of crude oil. As the supplied crude oil has recently experienced a trend of becoming heavier and poorer in quality, the conventional FCC catalyst with Y zeolite as the active component could not meet the demand of heavy oil cracking. Therefore, small-size Y zeolites with high silicon aluminium ratio (HSY) which have shown high activity and stability has become the focus of the new FCC catalyst development. In the present paper, HSY samples (silicon aluminum ratio ranged from 5.5 to 6.5, the particle size of 200-400 nm) under the different synthesis scale were ultra-stable treated, modified with lanthanum, mixed rare earth and phosphorus. The effects of the modification conditions were deeply investigated and the materials' catalytic performances were evaluated by using micro-activity test and triisopropylbenzene cracking reaction. The results show that:(1) The HSY-USY sample prepared by dynamic hydrothermal plus calcination treatment had the highest hydrothermal stability and the proper range of silicon aluminum ratio. The optimized condition of hydrothermal ultra-stable treatment is as follows:steam amount of 240 gram per hour; temperature of dynamic hydrothermal plus calcination of 500?.(2) The optimized condition of Lanthanum modification is as follows:exchange time of 1 hour; lanthanum iron concentration of 20%; lanthanum impregnation amount of 4wt%. After La ion exchange, the samples showed increased strength and roughly the same number for the weak acid sites while decreased strength and number for medium strong acid sites. With increasing La impregnation content, the numbers of the weak acid and the medium strong acid sites of modified samples both increased while the strength kept roughly the same.(3) The introduction of cerium improved the hydrothermal stability of the modified samples; Cerium impregnated samples gave more weak acid and strong acid sites and the strength became stronger; The introduction of phosphorus further modulated the acid distribution and improved the hydrothermal stability of the modified samples.(4) The catalytic activity of the modified samples was improved by rare earth and phosphorus. Among them, the mixed rare earth impregnated samples (REUSY-I) showed the highest light oil micro-activity (85.2%) and the highest TIPB cracking rate (98.4%); Phosphorus introduction can reduce the coke yield of light oil micro reaction.