La/HZSM-5催化剂上丙烷的芳构化反应研究

Aromatization of Propane over La/HZSM 5 Catalyst

采用浸渍法和离子交换法制备了La/HZSM 5分子筛催化剂 ,用于丙烷芳构化反应。利用XRD ,XPS ,FT IR ,NH3 TPD技术考察了La对HZSM 5分子筛结构和表面酸性的影响。引入La后能显著提高HZSM 5的丙烷芳构化活性 ,其中由离子交换法得到的催化剂效果最佳 ,在反应温度 5 5 0℃ ,空速 60 0h- 1 条件下 ,丙烷转化率和芳烃选择性分别达到 94 5 8% ,68 99%。在La/HZSM 5中分子筛结晶度下降 ,B酸中心减少 ,L酸中心增多。离子交换法制备的催化剂比浸渍法催化剂的这种变化更显著。同时更有利于La3+ 进入分子筛孔道内 ,并与分子筛产生强相互作用。

La/HZSM 5 zeolite catalysts for aromatization of propane were prepared by means of impregnation and ion exchange methods. The structure and acidity of the catalysts were investigated with XRD, XPS, FT IR, NH 3 TPD technologies. The behavior of catalyst is obviously improved when La is introduced into HZSM 5. Especially, under conditions of 550 ℃, 600 h -1 , propane conversion and aromatics selectivity over La Z E reach 94 58%, 68 99%, respectively. FT IR and NH 3 TPD results show that the amount of Brsted acid centers decrease, but Lewis acid centers increase in La modified HZSM 5 zeolite. A strong interaction between La species and zeolite is observed which might affect the structure of HZSM 5. The new Lewis acid centers are active for aromatization of propane.