纳米薄层HZSM-5分子筛催化甲醇制丙烯

在合成系列硅铝比纳米薄层HZSM-5分子筛的基础上,研究了纳米薄层HZSM-5分子筛催化甲醇制丙烯(MTP)的反应性能.在固定床微反装置上详细考察了工艺条件对纳米薄层HZSM-5分子筛催化性能的影响,同时与纳米HZSM-5分子筛对MTP反应的催化性能进行了比较.结果表明,纳米薄层HZSM-5分子筛具有较高的目的产物选择性和较长的催化寿命.在适宜硅铝比(n(SiO2)/n(Al2O3)=213)和反应条件下(温度470°C,甲醇质量空速为3 h-1),丙烯的选择性达到46.7%,三烯(乙烯、丙烯和C4烯烃)选择性达到78.7%.其中,丙烯/乙烯的质量比可达到6.5,是纳米HZSM-5分子筛的2倍,而芳烃的选择性比纳米分子筛明显降低.这是因为纳米薄层HZSM-5分子筛比纳米HZSM-5分子筛具有较宽的(010)晶面、较大的外比表面积和介孔孔容.

Methanol to Propylene over Nanosheets of HZSM-5 Zeolite

Nanosheets of HZSM-5 zeolite with different SiO₂/Al₂O₃ molar ratios were synthesized, and their catalytic behavior in the methanol-to-propylene (MTP) reaction was evaluated in a fixed bed reactor. The effect of reaction conditions on catalytic performance was studied in detail. The catalytic performance of nanosheets of HZSM-5 zeolites in the MTP reaction was compared with that of the nanosized HZSM-5 zeolite. The nanosheets of HZSM-5 zeolite had higher propylene selectivity, total three olefins' selectivity (ethylene, propylene, C₄ alkenes) , and a longer catalytic lifetime than the nanosized HZSM-5 zeolite. The nanosheets of HZSM-5 zeolite with a SiO₂/Al₂O₃ molar ratio of 213 yielded a propylene selectivity of 46.7%, total three olefins' selectivity of 78.7% at 470 ℃, and a methanol weight hourly space velocity (WHSV) of 3 h^-1. It also yielded a propylene/ethylene mass ratio of 6.5, which was double that of the nanosized HZSM-5 zeolite. The nanosheets of HZSM-5 zeolite had a lower aromatic selectivity than the nanosized HZSM-5 zeolite. The good MTP catalytic performance of the nanosheets of HZSM-5 zeolite was attributed to their wide (010) surface, high external surface area, and large mesoporous volume.