Mo/HZSM-5催化剂上丙烷的芳构化反应

Studies of Aromatization of Propane over Mo/HZSM-5 Zeolite Catalysts

采用浸渍法、机械混合法和水热法制备了Mo/HZSM 5分子筛催化剂 ,考察了Mo含量和在线反应时间对丙烷芳构化反应的影响 ,并以IR ,XRD ,NH3 TPD和XPS等表征手段研究了Mo物种对HZSM 5分子筛结构和酸性的影响 .结果表明 ,水热法制备的催化剂丙烷芳构化活性最高 ,且具有较高的活性稳定性 ,在焙烧过程中Mo物种易在HZSM 5分子筛上分散 ,且比浸渍法更多地进入分子筛孔道内 ,并与分子筛产生强相互作用 ,使B酸中心减少 ,L酸中心增多 .而浸渍法制备的催化剂的芳构化性能比相应的水热法催化剂低 ,活性稳定性较差 ,经焙烧后在分子筛外部形成结晶 ,进入孔道内的数量较少 。

Three Mo/HZSM 5 catalysts used for propane aromatization are prepared by means of impregnation, mechanical mixing and hydrothermal methods. The influence of Mo content, reaction time on stream are examined. The catalyst structure and surface acidity are studied by means of XRD, FT IR, NH 3 TPD and XPS. The results show that the performance of the catalyst made by hydrothermal method is much better than that of the other two catalysts. The propane conversion and aromatics selectivity over this catalyst can respectively reach 89 17% and 78 56% under the conditions of 550 ℃ and 600 h -1 (GHSV). MoO 3 species in this catalyst is highly dispersed on the surface of HZSM 5, and more of them can penetrate into HZSM 5 channel than the other two catalysts, which may be responsible for the high aromatization performance. The results from IR and NH 3 TPD show that the acidity change of the catalyst is favorable to the enhance of aromatics formation.