不同硅铝比Al-ITQ-13分子筛的甲醇制丙烯反应催化性能

Catalytic performances of Al-ITQ-13 zeolites with different SiO2/Al2O3 ratios in the conversion of methanol to propene

    摘要
  • 摘要: 采用晶种法直接合成了硅铝比（SiO2/A12O3物质的量比）为137、224和309的三种Al-ITQ-13分子筛，并采用粉末X射线衍射（XRD）、扫描电镜（SEM）、N2吸附-脱附、固体核磁共振（MAS NMR）和NH3-程序升温脱附（NH3-TPD）等分析方法对不同硅铝比分子筛进行了表征，并在固定床微型反应评价装置上，考察了硅铝比对甲醇转化制丙烯反应性能的影响。结果表明，不同硅铝比Al-ITQ-13分子筛呈现出相似的织构性质，酸量及酸强度随着硅铝比的升高逐渐下降。硅铝比对甲醇转化反应的产物分布存在较大的影响；随着硅铝比的升高，氢转移反应和芳构化反应活性降低，使得乙烯选择性下降，而丙烯和丁烯的选择性升高。硅铝比由137提高到309，丙烯的选择性（质量分数）由46.04%增加到55.52%，而丙烯/乙烯比由3.39提高到6.57。

     

    Abstract: Al-ITQ-13 zeolites with different SiO2/Al2O3 molar ratios were synthesized by using seeds in the gel and characterized by XRD, SEM, N2 physisorption, MAS NMR and NH3-TPD. The effect of SiO2/Al2O3 molar ratio on the catalytic performance of Al-ITQ-13 in the conversion of methanol to propene (MTP) was investigated in a fixed-bed micro-reactor. The results showed that the Al-ITQ-13 zeolites with different SiO2/Al2O3 molar ratios are similar in their textural properties; however, the amount and strength of acid sites decrease with the increase of SiO2/Al2O3 molar ratio. Moreover, the SiO2/Al2O3 molar ratio has a significant influence on the catalytic behavior of Al-ITQ-13 in MTP. As the hydrogen transfer and aromatization reactions were suppressed over the Al-ITQ-13 zeolite with high SiO2/Al2O3 molar ratio, with the increase of SiO2/Al2O3 molar ratio, the selectivity to propene and butene is increased at the expense of the selectivity to propene; that is, with the increase of SiO2/Al2O3 molar ratio from 137 to 309, the selectivity to propene is increased from 46.04% to 55.52% and meanwhile, the propene/ethene ratio is increased from 3.39 to 6.57.

     

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