ZSM-5催化剂水蒸汽处理对甲苯选择性歧化性能的影响

Effects of Hydrothermal Treatment on Selective Toluene Disproportionation

考察了不同条件下水蒸汽处理对ZSM -5催化剂上进行的甲苯歧化反应活性和选择性的影响 ,并对制得的催化剂进行NH3-TPD、XRD、2 7AlMASNMR和约束指数的测定。结果表明 ,在较低温度下处理 ,ZSM -5分子筛骨架脱铝较少 ,而且孔道得到了疏通 ,催化活性提高 ,选择性下降 ;高温时 ,由于骨架脱铝严重 ,活性位大量减少 ,转化率下降 ,同时由于孔道内非骨架铝的堆积 ,扩散阻力变大 ,催化剂的对位选择性有较大提高 ,达到 70 %以上 ;水蒸汽处理是改善ZSM

Toluene disproportionation was carried out on ZSM-5 catalyst previously treated with steam at different temperatures.The catalysts were also characterized by using NH 3-TPD,XRD, 27 Al MAS NMR and constraint index techniques.With increase in steaming temperature,the cell volume of the zeolite contracts gradually which indicates increase in the dealumination degree of ZSM-5At low temperature,although with slight dealumination,the smoothness of the channel causes the acitivity of ZSM-5 to increase.If the catalyst is treated at rather high temperature,the removed aluminium species will block the channel,decrease the activity and increase the selectivity of the catalyst.The experiment results reveal that hydrothermal treatment is effective in improving the catalytic performance of ZSM-5 in toluene disproportionation.