介孔HZnZSM-5分子筛的合成及其甲醇芳构化性能

Synthesis of Mesoporous HZnZSM-5 Zeolite and Its Catalytic Performance in Methanol Aromatization

直接将Zn物种引入碱及表面活性剂溶液,制备了HZnZSM-5介孔分子筛。采用X射线衍射、NH_3程序升温脱附、N_2吸附-脱附、扫描电镜及透射电镜表征所制备的样品,并考察了其催化甲醇芳构化的反应性能。结果表明,未添加Zn物种制得的介孔HZSM-5的结晶度、强酸量及强度均比传统HZSM--5有所降低,其外表面积及介孔孔容显著增加;Zn物种的引入对样品形貌影响不大,但降低了其强酸量、外表面积及介孔孔容,且介孔分布减少。HZnZSM--5在甲醇芳构化反应中具有明显高于介孔HZSM--5的苯、甲苯及二甲苯(BTX)选择性,且其催化稳定性显著高于HZSM--5。

Zn-containing mesoporous HZSM-5 （mesoporous HZnZSM-5） zeolite was synthesized by introducing Zn species directly into alkaline and surfactant solution, and characterized by powder X-ray diffraction, NH3-temperature programmed desorption, Nz adsorption-desorption, scanning electron microscopy and transmission electron microscopy techniques. Compared to conventional HZSM-5, the crystallinity, the amount and strength of strong acid sites of mesoporous HZSM-5 obtained without Zn species showed an evident decrease, whereas the external surface area and mesopore volume increased obviously. The introduction of Zn species had a little effect on the morphology, but reduced the amount of strong acid sites, the external surface area and mesopore volume. At the same time, the mesopore distribution decreased. Mesoporous HZnZSM-5 showed the evidently improved the selectivity to benzene, toluene and xylene （BTX）, compared with mesoporous HZSM-5 in methanol aromatization. Moreover, the selectivity of BTX was also increased with the decrease of mass hourly space velocity and the increase of reaction temperature. Furthermore, the catalytic stability of mesoporous HZnZSM-5 was much higher than that of HZSM-5.