硅-金属氧化物改性ZSM-5分子筛对碳八芳烃异构化反应性能的影响

Effect on isomerization of carbon octaaromatic hydrocarbons using ZSM-5 modified by silicon and metal oxide

采用硅-金属氧化物对ZSM-5分子筛的结构与酸性进行了组合改性,制备出高选择性碳八芳烃脱烷基异构化催化剂,利用X射线衍射法、氨气吸附-程序升温脱附法等对制备催化剂的性质进行了表征,考察了氧化硅、氧化镁、氧化镧的负载量对碳八芳烃脱烷基型异构化反应中乙苯转化率、二甲苯收率、异构化率等的影响。结果表明:负载物均未影响改性ZSM-5分子筛催化剂的晶型结构,且分散均匀;金属氧化物的加入有助于调节催化剂的酸量,同时可降低催化剂表观活化能,使反应更易进行,降低芳烃损失;当氧化硅、氧化镁负载质量分数分别为2.5%,1.0%时,异构化反应中的二甲苯收率、异构化率、乙苯转化率依次为97.4%,24.4%,78.3%,改性催化剂综合性能最优。

The structure and acidity of ZSM-5 zeolite were modified by liquid silicon deposition modification combined with metal oxide loading modification. A highly selective catalyst for decalkylation of C8 aromatic hydrocarbons was prepared. The properties of the catalyst were characterized by X-ray diffraction, ammonia adsorption temperature programmed desorption, etc. The effects of silicon deposition and MgO,La2O3 loading amount on the isomerization of C8 aromatic hydrocarbons were investigated. The results showed that the deposition did not affect the crystal structure of the modified ZSM-5 zeolite catalyst, and the catalyst was well dispersed;the addition of the deposition of metal oxides were helpful to adjust the acid content of the catalyst, reduce the apparent activation energy of the catalyst, make the reaction easier and reduce the loss of aromatics. When SiO2 deposition was 2.5% and MgO loading was 1.0%, the catalyst had the best comprehensive performance, the yield of xylene was 97.4%, the isomerization rate was 24.4% and the conversion of ethylbenzene was 78.3%.