Zn对HZSM-5分子筛催化剂物化及甲醇芳构化反应性能的影响

Physicochemical and methanol aromatization property of HZSM-5 catalyst promoted by Zn

分别以浸渍法和水热合成法向HZSM-5分子筛中引入Zn助剂对其进行改性。采用XRD、SEM、NH3-TPD和XPS等技术对改性前后的分子筛进行了表征。结果表明,采用两种不同方式引入Zn助剂对分子筛的晶体结构、孔径及形貌影响均很小,但能明显改变分子筛的表面酸性。两种方式引入Zn均使分子筛表面的强酸酸量明显降低,而弱酸酸量有所增大。最后,考察了Zn的引入对HZSM-5催化剂甲醇芳构化催化性能的影响。结果表明,两种方法引入Zn虽然均能提高甲醇芳构化反应的初始活性和芳烃选择性,但容易导致分子筛表面积炭而使催化剂快速失活。

HZSM-5 catalysts were modified by the addition of Zn through impregnation and hydrothermal methods respectively.X ray diffraction（XRD）,X ray photoelectron spectroscopy（XPS）,nitrogen adsorption,temperature-programmed desorption of ammonia（NH3-TPD）and scanning electron microscopy（SEM）techniques were used to characterize the catalysts.The results showed that the addition of Zn by the two methods had little influence on the skeletal structure,pore structure and morphology of catalyst particles,but could change the surface acidity of catalysts.The addition of Zn by the two methods could lead to a reduction of the amounts of strong acid sites apparently,causing an increase of the amounts of weak acid sites slightly.In addition,the catalytic performance of catalysts for the aromatization of methanol were studied.The initial catalytic properties and selectivities of aromatization products over the HZSM-5 modified by Zn through the two methods were superior to those of HZSM-5.But the addition of Zn could lead to carbon deposition on the surface of HZSM-5 catalyst and result in quick deactivation.