硅铝比对HZSM-5分子筛催化正丁烷裂解反应性能的影响研究

利用原位红外光谱法对不同硅铝比的HZSM-5分子筛催化剂进行表征，并在微反评价装置上对不同硅铝比分子筛催化正丁烷高温裂解活性进行评价，揭示了HZSM-5分子筛“硅铝比-活性位性质-催化性能”三者之间的关系。结果表明，硅铝比［n（SiO2）/n（Al2O3）］分别为38和200的HZSM-5分子筛表面活性位类型、数目和强度均存在巨大差异。HZSM-5-38分子筛表面存在较多的强酸性的硅铝桥键羟基和非骨架铝羟基，而HZSM-5-200分子筛表面仅存在少量的弱酸性或不具酸性的微孔内邻位孤立硅羟基和外表面孤立硅羟基。HZSM-5-200分子筛表现出更高的低碳烯烃收率，因而较低的酸密度和酸强度有利于多产烯烃。

STUDY ON EFFECTS OF SiO2/Al2O3 RATIO OF HZSM-5 ZEOLITES ON n-BUTANE CRACKING

The HZSM-5 zeolites with different mole ratio of SiO2/Al2O3 were characterized by in-situ FT-IR and their n-butane cracking activities were investigated in a continuous flow fixed-bed micro-reactor to reveal the relationship between Si/Al ratio, active sites and catalytic behavior. The results indicated that the kind，number， and strength of active sites of HZSM-5 zeolites with Si/Al ratio of 38 and 200 were significantly different. HZSM-5-38 zeolites have more acid bridging Si-O（H）-Al groups and non-skeleton aluminum hydroxyl with strong acidity, while，HZSM-5-200 zeolites only show several isolated hydroxyl groups with small amount of weakly acidic or non-acidic neighbouring silica hydroxyl groups in microporous. HZSM-5-200 zeolites result in higher yield of light olefins, indicating that lower acid density and strength is suitable for producing more olefins.