带压水热处理对HZSM-5沸石结构和性质的影响

EFFECT OF HYDROTHERMAL TREATMENT WITH HIGHERWATER VAPOR PRESSURE ON THE STRUCTUREAND PROPERTIES OF HZSM5 ZEOLITE

利用ＸＲＤ，２７ＡｌＭＡＳＮＭＲ，ＮＨ３ＴＰＤ和吡啶吸附ＩＲ等技术考察了带压水热处理温度对直接法ＨＺＳＭ５沸石骨架铝的迁脱和表面酸性质的影响规律．实验发现，随着水热处理温度的升高，沸石骨架铝的迁脱量增加．在带压水热处理条件（４００～６００℃）下，直接法ＨＺＳＭ５的骨架结构稳定，其骨架铝不能大量迁脱．对ＨＺＳＭ５（３８），于５００℃和水蒸气压力为１０ＭＰａ条件下水热处理１２ｈ后，只能使３００％的骨架铝迁脱．高真空吡啶吸附ＩＲ表明，先经６００℃带压水热处理２ｈ，然后再用１ｍｏｌ／Ｌ的ＨＣｌ溶液除去非骨架铝的ＨＺＳＭ５（３８）样品中存在较大量的Ｌ酸中心．

The migration of framework aluminium and the surface acidity of HZSM5 zeolite synthesized with direct method after steaming at different temperatures (400～600℃) with higher water vapor pressure (10 MPa) and then washed with HCl (1 mol/L) were examined by using XRD, 27Al MAS NMR, NH3TPD and IR spectroscopy techniques. It is discovered that with the increase of the steaming temperature, the dealumination degree of HZSM5 is increased. Under the experimental conditions, the structure of HZSM5 synthesized with direct method is stable, and its framework aluminium can not be removed largely. For HZSM5(38) zeolite, only 300% framework aluminium can be removed from framework after steaming at 500℃ with water vapor pressure of 10 MPa for 12 h. High vacuum IR spectra of pyridine adsorption shows that HZSM5(38) zeolite after steaming at 600℃ with water vapor pressure of 10 MPa for 2 h and then being removed nonframework aluminium with HCl (1 mol/L) contains a large number of Lewis acid sites.