中孔ZSM-5沸石的制备及其催化裂解性能

采用碱处理脱硅制备了中孔ZSM-5沸石，考察了不同碱处理方式对ZSM-5沸石的酸性质和孔结构的影响，采用XRD、NH3-TPD、SEM、N2吸附-脱附、FT-IR等手段对碱处理ZSM-5沸石进行表征，研究了碱处理ZSM-5沸石对裂解正构烷烃nC14、1,3,5-三异丙基苯和轻柴油裂化反应的催化性能。结果表明：碱处理ZSM-5沸石的中孔比表面积、中孔孔体积以及酸量均比工业ZSM-5沸石有所增加，在催化裂解nC14时，促进了己烷的进一步裂解，提高了产物中戊烷的选择性；在催化裂解1,3,5-三异丙基苯时加深了裂解程度，提高了初级裂解产物二异丙苯和深度裂解产物苯的选择性；在催化裂解轻柴油时，增加了汽油收率。并且，加入TPA+阳离子与NaOH的混合碱液比加入单一的NaOH碱溶液更能促进ZSM-5沸石表面脱硅，使得表面富铝，促进了中孔结构的形成，进一步增大了中孔比表面积和中孔孔体积，增加了酸量，提高了ZSM-5沸石的催化裂解性能。

Preparation of Mesoporous ZSM-5 Zeolites and Its Catalytic Cracking Performance

Desilication by alkali treatments was employed in industrial ZSM-5 zeolite preparation to create mesoporous structure. Effects of different alkali treatments on the acidity and pore structure of ZSM-5 zeolites were investigated. The treated samples were characterized by X-ray diffraction (XRD), ammonia temperature programmed desorption (NH3-TPD), N2 adsorption-desorption, scanning electron microscopy (SEM) and FT-IR. Moreover, the catalytic performance of the alkali treated ZSM-5 zeolites were evaluated by cracking reactions, with nC14,1,3,5-triisopropylbenzene(TIPB) or light diesel oil as feedstock. Results show that the alkali treated ZSM-5 zeolites enhance the area and volume of the mesopore, as well improve the acid amount with great efficiency to enhance the selectivity of C5 products in nC14 cracking, improve the TIPB cracking conversion with more production of the primary cracking product (diisopropylbenzene) and deep cracking product (benzene), increase the productivity of gasoline in light diesel cracking. Furthermore, the blended alkali solution with TPA+ and NaOH improve further desilication of ZSM-5 zeolite to form Al-rich surface, with higher efficiency to construct mesoporous structure, improving the area and volume of mesopore and the acid amount, thereby increasing the catalytic cracking performance of ZSM-5 zeolite.