Si(CH3)3Cl修饰的HZSM-5酸性及正己烷芳构化的催化性能研究

随着芳烃需求量的增加,低分子烃的芳构化受到广泛重视.由于HZSM-5的独特骨架结构及酸性,使其对低分子烃有良好芳构化性能~1～3],但研究工作大多放在HZSM-5本身的硅铝比调变及加入某些金属(如Ga,Zn)来提高其芳构化性能~4～7],而以非金属对其进行改性处理则很少见.本文以Si(CH_3)_3CI对HZSM-5进行CVD处理,并对其酸性及对正已烷芳构化能力进行了考察,研究了催化剂的结焦情况.

Studies on Acidity of HZSM-5 Modified by Si(CH_3)_3Cl and Its Catalytic Behaviour in n-Hexane Aromatization

The surface properties of HZSM-5 zeolite modified by Si(CH3)3Cl were studied by TPD,IR,27A1 MAS NMR.Catalytic reaction of n-hexane aromatization was investigated by continuous-reaction.The coke of catalysts was measured by DSC.It was found that the concentration of the strong Bronsted acid sites decreased and that of the stronger Lewis acid sites increased after modification by Si(CH3)3Cl.The TPD peaks of NH3,which were presumally attributed to the stronger acid sites,were decreased by the deposition of Si(CH3)3Cl on the surface of the zeolite.The conversion of n-hexane and selectivities of aromatic compounds were controlled by changing the concentration of the stronger acid sites.But aromatic compounds distribution can be attained by controlling the pore opening and channel of the zeolite.