改性HZSM-5分子筛催化二甲醚转化制汽油馏分烃研究

Catalytic conversion of dimethyl ether to gasoline-range hydrocarbons over modified HZSM-5

在连续流动固定床反应器上考察了不同孔径尺寸的微、介孔ZSM-5分子筛的二甲醚催化转化反应性能,采用N2吸附-脱附、NH_3-TPD、XRD、TGA,TPO-MS和GC-MS等表征技术研究了分子筛改性对其结构性能的影响,同时关联其反应性能,探讨了分子筛的催化反应机制。研究结果表明,控制后处理条件可有效调控分子筛的孔径尺寸,HZSM-5分子筛具有适当的介孔尺寸有助于反应产物汽油馏分烃的生成,但孔径过大将失去分子筛对产物分布调控意义;介孔孔径在7.0nm左右时,二甲醚转化反应可获得富含异构烷烃(质量分数高达55.2%)的汽油,同时联产高附加值化工品均四甲苯,这可为清洁油品改质和高附加值化工品的生产提供一条可能的新路线。研究结果还表明介孔结构的形成有利于多甲基苯碳物种向生成反应产物的方向进行,进而抑制反应过程中积炭的形成。

The catalytic performances of modified ZSM-5 zeolite catalysts with different sizes of micro-and meso-pores in DME to gasoline-range hydrocarbons were investigated in a continuous fixed bed reactor, and N2 sorption-adsorption, NH3-TPD, XRD,TGA, TPO-MS and GC-MS were used to characterize the catalysts to study the effect of modification on the structure and catalytic performance of the catalyst and understand the reaction mechanism. The results show that the pore size of zeolites can be effectively adjusted by changing the conditions in post-treatment of zeolites. HZSM-5 with appropriate mesopores contributes to the formation of gasoline-range hydrocarbons, while the oversize apertures of HZSM-5 can not control the product distribution. When the pore size of zeolite is 7.0 nm, the high selectivity of isoparaffins（55.2% by mass） was obtained in the reaction, and the high value-added durene was also produced in the meantime. A possible new route for the reforming of clean fuel and the production of high value-added chemicals was provided. The results also show that mesoporous structure of zeolite is beneficial to converse polymethylbenzene to the target products instead of the coke.