摘要
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.
The cracking characteristics of C_3～C_10 alkanes over HZSM-5 zeolites with different strength acid sites were investigated by poisoning method. The IR spectra of chemisorbed pyridine at different temperatures showed that the weak acid sites on the HZSM-5 zeolite are mostly Lewis-acid sites (80.4%). With the gradually increased acid strength of active sites on HZSM-5 zeolite,the number of B-acid sites increase rapidly (up to 91.4%) for strong and ultrastrong acid sites. The product distribution from conversion of alkanes depends closely on the acidity and strength of acid sites on HZSM-5 zeolite as well as the chain length of reactants. The shorter the chain length of alkanes, the stronger the acid sites on HZSM-5 zeolite are needed to initiate the reaction. With the same strength of acid sites of HZSM-5, the longer the chain length of reactants, the greater the conversion. The addition of small amount alkene into the alkanes can enhance the conversion of the latter. The promotion effect of alkene occurs significantly only on strong acid sites or at lower temperatures (400～ 500℃). The reaction mechanism for catalytic conversion of alkanes over HZSM-5 zeolite is discussed.
出处
《石油学报（石油加工）》
EI
CAS
CSCD
北大核心
1990年第2期10-18,共9页
Acta Petrolei Sinica(Petroleum Processing Section)
基金
国家自然科学基金资助课题
