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采用吡啶中毒方法研究了HZSM-5沸石表面不同强度酸中心上C_3～C_(10)直链烷烃裂解反应特征.吡啶吸附的红外光谱研究表明HZSM-5沸石表面的弱酸中心主要是L酸中心(80.4%),随表面酸强度增加,B酸中心比例迅速增大.烷烃转化反应的产物分布与沸石表面酸性、酸中心强度和反应物分子链长有密切关系.烷烃碳链越短则越需在更强的酸中心上才能开始反应;同一强度酸中心上烷烃碳链越长,反应速率越快.加入少量烯烃可以增加烷烃反应的转化率.烯烃的催速作用只有在强酸中心上或是在低温下(<400～500℃)才显示出来.对HZSM-5表面上烷烃裂解存在的两种反应机理进行了讨论.
Pyridine poisoning was used to study the cleavage characteristics of C_3 ~ C_ (10) linear paraffins on the acid sites of HZSM-5 zeolite with different intensities.The results of FTIR spectroscopy showed that the weak acid sites on the surface of HZSM- 80.4%), with the increase of surface acidity, the proportion of B acid center increases rapidly.The product distribution of alkane conversion reaction is closely related to the surface acidity, acid center strength and reactant molecular chain length of alkane. The reaction can be started at a stronger acid center; the longer the carbon chain of the alkane on the same strength acid center, the faster the reaction rate. The addition of a small amount of olefins can increase the conversion of the alkane reaction. At low temperature (<400 ~ 500 ℃), the reaction mechanism of paraffin cracking on HZSM-5 surface is discussed.