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用脉冲微反技术研究了临氢条件下正十六烷在硅铝比为31.4—137.1的HZSM-5分子筛上的裂解,发现随Al/u.c.的减小,裂解活性下降,当Al/u.c.<3.64时,活性下降缓慢,表明除了B酸和L酸中心是裂解的活性中心外,非铝酸中心(可能是硅羟基)亦有活性,改变反应条件和表面的酸性质可控制产物的分布,随反应温度增加,产物中非芳烃的平均分子量减小,芳烃增加,烯烃量出现极大值,而液收几乎不变;随接触时间的增加,芳烃量增加,液体产物显著下降;另外产物中芳烃量与形成芳烃的活性中心——B酸的浓度呈线性关系;强的B酸中心被积炭覆盖有利于芳烃的形成,水蒸汽处理可使裂解活性下降,液收提高,芳烃减少,烯烃显著增加,同时可提高HZSM-5分子筛的抗积炭能力。
The effect of n-hexadecane cracking on HZSM-5 molecular sieve with Si / Al ratio of 31.4-137.1 was studied by pulsed micro-inversion technique. It was found that the cracking activity decreased with the decrease of Al / uc. When Al / uc < 3.64, the activity decreased slowly, indicating that in addition to the B acid and L acid center is the active center of cleavage, the non-aluminic acid center (which may be silanol) also have activity, changing the reaction conditions and surface acid properties can control the product distribution, With the increase of the reaction temperature, the average molecular weight of non-aromatic hydrocarbons in the product decreases, while that of aromatics increases, the maximum of olefins and the change of liquid yield almost remain unchanged. With the increase of contact time, the amount of aromatics increases and the liquid products decrease significantly. Aromatics content and the formation of aromatics active center - B acid concentration was linear; strong B acid center is covered by coke is conducive to the formation of aromatics, steam treatment can reduce the cracking activity, increased liquid collection, aromatics decreased, olefins A significant increase, while improving the HZSM-5 molecular sieve capacity of anti-carbon.