双功能WC/HZSM-5催化剂上正己烷芳构化反应性能

Catalytic Performance of Bi-functional WC/HZSM-5 Catalysts for n-Hexane Aromatization

以HZSM-5(SiO2/Al2O3=38)为载体,偏钨酸铵为钨源制备了双功能催化剂WC/HZSM-5,考察了其催化正己烷芳构化反应性能,并采用X射线衍射、扫描电子显微镜、X射线能量散射谱和程序升温氨脱附等手段对催化剂进行了表征,探讨了制备方法和WC含量对WC/HZSM-5催化剂性能的影响.结果表明,采用原位还原碳化法制备的WC/HZSM-5(RC)催化剂上正己烷芳构化反应性能优于浸渍法制备的WC/HZSM-5(IP).5%WC/HZSM-5(RC)样品在反应初始阶段芳烃选择性为10.28%,而HZSM-5上的仅为2.56%.WC/HZSM-5(RC)催化剂上反应产物中轻质芳烃(苯、甲苯和二甲苯)含量增加,重质芳烃C9+含量降低,其催化性能优于Pt/HZSM-5催化剂.产物分布的变化可能是由于WC与分子筛间的协同作用所致.

Bi-functional tungsten carbide （WC） supported on HZSM-5 （WC/HZSM-5） catalyst samples were prepared and studied in n-hexane aromatization. Two series of catalyst samples with varying WC loadings were synthesized by insitu reduction-carbonization （WC/HZSM-5（RC）） and impregnation methods （WC/HZSM-5（IP））. The catalyst samples were characterized by NH3 temperature-programmed desorption, X-ray diffraction, and scanning electron microscopy combined with energy dispersive spectroscopy. The results showed that WC/HZSM-5（RC） has much higher catalytic activity than WC/HZSM-5（IP）. The aromatic selectivity on 5%WC/HZSM-5（RC） was 10.28%, which was much higher than that of HZSM-5 （2.56%）. The aromatics （benzene, toluene, and xylene） content in liquid products was 85.07%, much higher than that of HZSM-5 （67.71%）. These results are interpreted by the bi-functional mechanism due to the synergistic action between the HZSM-5 and WC.