Studies On The Catalyst Of Two-Stage Riser Catalytic Pyrolysis For Maximizing Propylene Yield

Propylene inferior to ethylene is an important basic feedstock of petrochemical industry. In recent years, the growth rate of global demand for propylene has been higher than that for ethylene. We should vigorously carry on new technology research on FCC propylene production and pay attention to the deep integration of the catalyst and the FCC process. The two-stage riser catalytic cracking for maximizing propylene yield process required relative high-HZSM-5, low-Y or USY zeolite content catalyst. So far, LTB-2 and other catalysts with high heavy oil cracking ability are mixed, such as LTB-2 and LCC-2, and then supplemented with TMP process better.For matching TMP process, the catalyst with enhanced propylene selectivity and lower hydrogen transfer activity is needed. We discuss active component and matrix of the catalyst. The effect of the catalyst to oil weight ratio and temperature on product distribution is also studied. It can be concluded that alkali treatment to ZSM-5 affects strong acidity and causes propylene/ethylene ratio increase and the yield of dry gas decrease. The results show that the propylene selectivity in LPG reach 46.22%, with conversion of 91.55% over the catalyst which is comprised of USY (600℃, 1ml/min) with low hydrogen transfer activity and high propylene selectivity and ZSM-5. When the USY content is 7%, the propylene selectivity in LPG reaches 47.59%, with conversion of 89.57%.The matrix modified by Zr,W presents strong acidity, resulting in sharp increase in coke yield. Amorphous silica/alumina mainly increases gasoline yield, while part substitution of kaolin with vermiculite and that under acid treatment brings cut increase in gases and decrease in diesel oil, which is related to its effect on the acidity and pore distribution of catalyst. Compared to other industrial aged catalysts, the performance of the catalyst is better. The conversion and the yield of light oil are more than those of LTB-2. The propylene selectivity in LPG is high as LTB-2. The conversion on MMC-2, LCC-2 is still better. The TMP process with high catalyst to oil ratio (C/O) can make up for that shortcoming. For such a catalyst, the conversion has markedly improved with high C/O. The selectivity of propylene in LPG drops to 45.72% under 540℃when the catalyst to oil ratio gradually increases to 8. It should be suitable for TMP.