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较系统地研究了质子化方法、硅铝比、焙烧温度和水热处理条件对HZSM-5沸石的酸性和芳构化活性的影响,比较了不同方法合成的ZSM-5芳构化性能。结果表明:用直接法合成的ZSM-5氢型的芳构化活性较高,且Si/Al 越低,芳构化活性越高。质子化方法对HZSM-5芳构化活性影响不大。B酸量和L酸量均随HZSM-5的Si/Al降低而增加,酸性羟基的稳定性则随Si/Al增加而提高。红外光谱上以1547cm~(-1)表征的B酸量和以3610cm~(-1)表征的羟基量随HZSM-5的焙烧温度升高而近似平行地下降。L 酸量则随焙烧温度升高开始增加,然后迅速下降。水热处理在一定的温度和水汽量范围内,对HZSM-5的酸强度分布和芳构化活性影响不大,超过这个范围,酸性和活性迅速降低。Si-OH-Al 基酸强度不均匀,将最强B酸与芳构化活性相关联,表明最强B酸位是HZSM-5芳构化的活性中心。
The effects of protonation method, the ratio of Si / Al, calcination temperature and hydrothermal treatment on the acidity and aromatization activity of HZSM-5 zeolite were systematically studied. The aromatization properties of ZSM-5 zeolite synthesized by different methods were compared. The results show that the ZSM-5 hydrogen form synthesized by the direct method has a higher aromatization activity, and the lower the Si / Al ratio, the higher the aromatization activity. The protonation method has little effect on the aromatization activity of HZSM-5. Both the amount of acid and the amount of L acid increased with the decrease of Si / Al of HZSM-5, while the stability of acidic hydroxyl increased with the increase of Si / Al. The amount of B acid characterized by 1547cm -1 and the amount of hydroxyl group characterized by 3610cm -1 in the infrared spectrum decreased with the increase of the calcination temperature of HZSM-5, and decreased in parallel. L acid content with the calcination temperature began to increase, and then decreased rapidly. Hydrothermal treatment at a certain temperature and moisture content within the HZSM-5 acid strength distribution and aromatization activity has little effect, beyond this range, the rapid decline in acidity and activity. The intensity of Si-OH-Al acid is not uniform, and the strongest B acid is related to the aromatization activity, indicating that the strongest B acid site is the active center of HZSM-5 aromatization.