摘要
用XRD,IR,XPS和TPD等方法,考察了用CF_3Cl处理的一系列含氟量不同的HZSM-5,HM分子筛的结构和表面性质的变化。结果表明,改性后催化剂的表面与体相有脱铝现象,并有新物相生成。少量氟的掺入可提高酸中心的强度,使中等强度B酸中心数增加。改性后的HZSM-5和HM对甲苯歧化反应的活性和稳定性都有所改善。
The physical and chemical changes of HZSM-5 and HM zeolites treated with CF3C1 for different times were studied by using XRD, XPS, TPD and IR methods. The catalytic behavior of F/HZSM-5 and F/HM for toluene disproportionation was also studied.The experimental results showed that the structure of HZSM-5 and HM was changed by fluorina-tion. On the surface of zeolite, F atom was bound with Al and Si atom, and combined with Al atom to form many kinds of fluorine species.De-alumination occurred in the bulk and on the surface, and a new phase was discovered on the surface when zeolite was fluorated. The unit cell was contracted. After the treatment of zeolites with CF3C1 for a short time, the strength of the acid sites enhanced and the fraction of B sites increased. For HZSM-5 treated with CF3C1, the conversion of toluene disproportionation increased, first, then decreased with increasing the time of fluorination. But the value of disproportionation ratio was just in reverse. HM showed improved activity and stability when it was treated with CF3C1.
基金
国家自然科学基金
