【摘要】 对比研究了SSZ-13(CHA拓扑结构)和RUB-50(LEV拓扑结构)硅铝分子筛笼大小对甲醇制烯烃反应性能的影响,并采用X射线衍射、N2吸附-脱附、固体核磁共振、热重和紫外-可见光谱等技术对催化剂的结构及反应后的碳物种进行了表征.结果表明,笼尺寸较大的SSZ-13分子筛在反应中的稳定性和产物丙烯选择性均较高;而笼尺寸较小的RUB-50分子筛中乙烯的选择性较高.酸洗可以除去分子筛中大部分非骨架Al,且在一定程度上改变了分子筛的酸性,但没有显著改变产物中乙烯和丙烯的相对比例.另外,分子筛笼的大小决定了碳物种的体积,较小笼径的分子筛上可能生成较多的乙烯.因此,用于甲醇制烯烃的分子筛笼径大小对调变产物中乙烯和丙烯选择性十分重要.更多还原

【Abstract】 The effect of cage size on the catalytic performance of SSZ-13 with CHA structure and RUB-50 with LEV structure has been comparatively investigated in the methanol-to-olefin(MTO) reaction. The zeolite structure and coke deposit were characterized by X-ray diffraction,N2 adsorption-desorption,solid-state NMR,thermogravimetry and UV-Vis spectroscopy. It is found that SSZ-13 zeolite with larger cage size has better stability and higher propylene selectivity in the MTO reaction,while RUB-50 zeolite with smaller cage size has higher ethylene selectivity. Most of nonframework Al can be extracted,and the acidity is altered to some extent after the zeolites were washed with dilute acid. However,this would not obviously change the ratio of propylene to ethylene in the products. In addition,the volume of carbonaceous species is dependent on the zeolite cage size. More ethylene would be produced in the zeolite with smaller cage size. Thus,the zeolite cage size is very important in altering the ethylene and propylene selectivity in the MTO reaction.更多还原