ZSM-34分子筛的合成及其催化甲醇转化制烯烃反应性能

Synthesis of ZSM-34 and Its Catalytic Properties in Methanol-to-Olefins Reaction

以氯化胆碱为模板剂,采用水热合成法在较短的晶化时间内合成了OFF/ERI共晶体ZSM-34,考察了各种合成条件对产物的影响.通过调变合成参数可以获得不同ERI含量的ZSM-34.用X射线衍射、扫描电子显微镜和X射线荧光分析等对合成产物进行了表征.吸附实验显示,所合成的分子筛具有较大的孔容,其对正己烷的吸附容量为11.4%.HZSM-34分子筛对甲醇转化制烯烃(MTO)反应具有良好的催化活性和高的乙烯选择性,低碳烯烃(乙烯+丙烯)选择性高达86.0%,并且在反应过程中始终维持在较高的水平,不受甲醇转化率降低的影响.高温水蒸气处理后的分子筛酸性降低,大大抑制了MTO初始反应中丙烷的选择性,而初始低碳烯烃的选择性则明显提高.

ZSM-34 （OFF/ERI intergrowth） was synthesized using choline chloride as the template in a shorter crystallization time under hydrothermal conditions. Many factors that may influence the synthesis were investigated. The ERI content in ZSM-34 could be adjusted by selecting different synthesis conditions. The synthesized products were characterized by X-ray diffraction, scanning electron microscopy, and X-ray fluorescence spectroscopy. Adsorption experiments showed that ZSM-34 possessed high pore volume, and the adsorption amount of n-hexane reached 11.4%. In the methanol-to-olefins reaction, HZSM-34 exhibited high selectivity for ethylene. The maximum selectivity for total olefins （C2H4 ＋ C3H6） over HZSM-34 was 86.0% , and it nearly did not change even when the methanol conversion decreased. High-temperature steam treatment increased the framework Si/AI ratio and thus decreased the acidity of HZSM-34, which led to the obvious decrease in propane selectivity and the increase in initial olefins selectivity.