Ga改性的HZSM-5分子筛甲醇芳构化催化反应性能

Property of HZSM-5 catalysts promoted by Ga in methanol aromatization

以浸渍法和水热合成法向ZSM-5分子筛中引入Ga助剂对其进行改性。采用XRD、XPS、NH3-TPD和SEM等技术对改性前后的分子筛进行了表征。结果表明,采用两种不同引入方式引入Ga助剂对分子筛的晶体结构、孔径及形貌影响均很小,而对分子筛酸性的影响与Ga的引入方式有关。其中,浸渍法引入Ga对分子筛的酸性影响不明显,只是其中的强酸位略有减少。而水热合成法引入Ga会显著增加分子筛的弱酸及强酸的酸量。在固定床反应器上考察了Ga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,水热合成法引入Ga较浸渍法引入Ga更能提高甲醇芳构化反应的活性和芳烃选择性。此外,Ga改性HZSM-5分子筛对其甲醇芳构化反应中积炭反应的抑制起到积极作用。

ZSM-5 catalysts were modified by the addition of Ga through impregnation and hydrothermal methods respectively.X-ray diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）,temperature-programmed desorption of ammonia（NH3-TPD）and scanning electron microscopy（SEM）techniques were employed to analyze the property of catalyst.The results show that two methods for Ga addition has little influence on the skeletal structure,pore structure of catalysts and morphology of catalyst particles,but they did have impact on the catalyst acidity.Ga modification by impregnation method has less influence on the surface acidity,and only slightly reduce the number of strong acid sites.Ga introduced by hydrothermal method increases the number of both weak and strong acid sites apparently.The catalytic performance of catalysts for methanol aromatization was studied in a fixed bed reactor.It can be found that the catalytic property of the HZSM-5 modified by Ga through hydrothermal method are better than that of the HZSM-5 modified by Ga through impregnation method.In addition,Ga has a positive effect to suppress the carbon deposition of HZSM-5 in methanol aromatization.