不同硅铝比ZSM-5分子筛作为助催化剂在渣油裂化中的应用

采用不同方法表征了硅铝比(SiO2/Al2O3)为33、266和487的质子型ZSM-5分子筛，并研究了ZSM-5分子筛作为助催化剂在渣油裂解中的应用。与USY分子筛基催化剂混合后，在固定流化床上，评价了ZSM-5分子筛助催化剂的催化裂化性能。研究发现，提高ZSM-5分子筛硅铝比，可以有效抑制混合催化剂对汽油烯烃的裂解，从而避免了汽油烷烃的大量损失。加入ZSM-5助催化剂后，伴随着液化气(LPG)产率的增加，异丁烷和异戊烷产率增加，这可能是由USY基催化剂和ZSM-5助催化剂的综合效应引起的。汽油烷烃和芳烃含量的变化，引起了汽油辛烷值的增加。高硅铝比ZSM-5分子筛(硅铝比为266和487)不仅可以显著改善汽油的辛烷值，而且有效避免了汽油的大量损失。催化汽油辛烷值的改善主要是由于高硅铝比ZSM-5分子筛具有适宜的芳构化和异构化活性，这些变化主要源于高硅铝比ZSM-5分子筛小的孔道直径和适宜的酸性。

ZSM-5 zeolites with different SiO2/Al2O3 ratios as fluid catalytic cracking catalyst additives for residue cracking

Three proton-type ZSM-5 zeolites with different SiO2/Al2O3 ratios (SARs) of 33, 266, and 487 were characterized and examined as fluid catalytic cracking catalyst additives for residue oil cracking. The catalytic performance of the ZSM-5 additives was evaluated using an ultra-stable Y-zeolite (USY)-based fluid catalytic cracking catalyst in a fixed fluid bed unit. As observed, the cracking of primary olefins over the hybrid catalysts consisting of USY-based catalyst and ZSM-5 additive was considerably inhibited by increasing the SAR of the ZSM-5 zeolite, thus avoiding substantial loss of gasoline paraffins. The introduction of ZSM-5 additives led to higher liquid petroleum gas yields as well as higher isobutane and isopentane yields. The improved yields were attributed to the com-bined effects of the ZSM-5 additives and USY-based catalyst. The variations of gasoline paraffins and aromatics both accounted for the enhancement in the octane number values. The use of ZSM-5 with higher SARs (266 and 487) led to an enhancement in the octane number with minimal loss of gaso-line. This enhancement was mainly attributed to the moderate aromatization and isomerization reactivity of the ZSM-5 additives that mainly originated from their relatively small pores and suita-ble acidic properties with higher SARs.