碳四液化气在离子浸渍改性纳米HZSM-5沸石上的转化反应研究

Effect of Ion-impregnation Treatment on the Transformation of C_4 LPG over Modified Nano-sized HZSM-5 Zeolite

在小型常压固定床反应器中研究了不同离子浸渍改性对纳米ZSM-5固体酸催化剂上丁烷和丁烯转化的影响.结果表明,混和碳四中异丁烷比正丁烷易转化,丁烯异构体的转化与其在原料中的含量有关.在贫烯烃原料中,丁烯倾向于生成.在富丁烯原料中,丁烯倾向于转化.但在两种情况下,产物中各丁烯含量大体上按异丁烯、顺反-丁烯-2和丁烯-1顺序递减.采用锌离子改性时异丁烷转化率提高、正丁烷转化率降低.锌离子改性有利于芳烃选择性,但是副产物甲烷和乙烷的产率也较高;铁离子改性对丁烷和丁烯的转化影响不大,但能减少甲烷和乙烷的生成,并提高芳烃选择性;与锌改性相比,锌钠双离子改性降低了异丁烷、正丁烷和丁烯-1的转化率,减少了芳烃产率,但能明显促进丙烯和丁烯的生成.上述结果为碳四液化气综合利用提供了有益信息.

By impregnating ions onto nano-sized HZSM-5 zeolite and carrying out the catalytic cracking of C4 liquefied petroleum gas （LPG） over the modified catalysts in a small fixed-bed reactor,the effect of different ions modification on the conversion of the butane and butene was investigated. Results show that,in the mixed C4 hydrocarbon feed,iso-butane is more active than normal-butane. However,the transformations of butene isomers are strongly related to their content in the feed. When the content of butenes in the feed is low,the total butene content tends to increase by formation. On the other hand,when the content of butenes in the feed is high,the total butene content tends to decrease by transformation. However,under any of these conditions,the content of butene isomers in products was seen generally increase at the sequence of butene-1,trans（cis）-butene-2,and iso-butene. The impregnation of the HZSM-5 zeolite with Zn2＋ increases the conversion of iso-butane,but decrease the conversion of normal-butane. Zn^2＋ modified catalysts also show high aromatics selectivity at the cost of generating more methane and ethane. The impregnation of the HZSM-5 zeolite with Fe^3＋ has little impact on the conversion of butane and butane,but has large effect on increasing the aromatics selectivity and decreasing the productivity of methane and ethane by-products. The combination of Zn^2＋ impregnation with Na^＋ reduces the conversion rate of iso-butane,normal-butane and 1-butene,and the selectivity of aromatics. However,it favors the productivity of ethylene and propylene obviously. The above-mentioned results provide beneficial information for the comprehensive utilization of C4 liquefied petroleum gas （LPG）.