Abstract

A series of extruded H-ZSM-5/alumina composite catalysts were prepared and characterized using N₂ sorption isotherm, transmission electron microscopy, scanning electron microscopy, infrared spectroscopy, X-ray diffraction, NH₃-TPD, and pyridine adsorption. The methanol conversion over the as-prepared catalyst as well as its components was studied at 500 °C. The catalysts with H-ZSM-5/alumina ratio 3/1 and 1/1 (by mass) catalyst exhibited the highest ethylene selectivity (up to 44%) and the ethylene/propylene ratio up to 10/1, whereas zeolite H-ZSM-5 demonstrated the propylene selectivity up to 30% and the ethylene/propylene ratio 1/8. In contrast, the catalyst with the H-ZSM-5/alumina ratio 1/3 demonstrated no activity toward olefins synthesis. The as-prepared H-ZSM-5/alumina catalysts have a long lifetime in the methanol-to-hydrocarbons conversion, which is several times higher compared to pure zeolite H-ZSM-5. The catalyst regeneration results in recovering the initial catalytic activity. The obtained findings reveal that embedding microporous zeolite in the mesoporous alumina matrix facilitates the mass transfer limitations and decreases the number of strong acid sites. These factors govern an essential performance of the as-prepared catalyst in the methanol-to-ethylene reaction.

摘要

_{采用N 2}吸附等温线、透射电镜、扫描电镜、红外光谱、X射线衍射、NH ₃等方法制备了一系列挤出H-ZSM-5/氧化铝复合催化剂并对其进行了表征。-TPD和吡啶吸附。在 500 °C 下研究了所制备的催化剂及其组分的甲醇转化率。H-ZSM-5/氧化铝比为 3/1 和 1/1（按质量计）的催化剂表现出最高的乙烯选择性（高达 44%）和乙烯/丙烯比高达 10/1，而沸石 H- ZSM-5 表现出高达 30% 的丙烯选择性和 1/8 的乙烯/丙烯比。相比之下，H-ZSM-5/氧化铝比例为 1/3 的催化剂对烯烃合成没有表现出活性。所制备的 H-ZSM-5/氧化铝催化剂在甲醇转化为烃的过程中具有较长的寿命，与纯沸石 H-ZSM-5 相比要高几倍。催化剂再生导致恢复初始催化活性。所获得的研究结果表明，在介孔氧化铝基质中嵌入微孔沸石有助于传质限制并减少强酸位点的数量。这些因素决定了所制备的催化剂在甲醇制乙烯反应中的基本性能。