MCM-22分子筛的酸性及在1-丁烯骨架异构化反应中的催化性能

 采用XRD,NH3-TPD及氘代乙腈吸附FT-IR等技术表征了静态水热合成法合成的MCM-22分子筛的晶相结构和酸性. 根据表征结果,Si/Al比为15和30的两个样品均为高纯度的MCM-22分子筛; 两个样品的Brnsted酸量基本相同,但Si/Al为15的样品上含有相对较高的Lewis酸量. MCM-22分子筛上1-丁烯骨架异构化反应的结果表明,Si/Al为30的样品具有较高的异丁烯选择性(74.8%)和稳定性, 而Si/Al为15的样品中存在的含量较高的Lewis酸位可能是导致异丁烯选择性(65.5%)下降的主要原因.

Acidity of MCM-22 Zeolites and Their Catalytic Performance for the Skeletal Isomerization of 1-Butene

MCM-22 zeolite samples with Si/Al molar ratios of 15 and 30 (denoted as MCM-22-15 and MCM-22-30, respectively) were synthesized by the hydrothermal method under static condition, and characterized by means of XRD, NH_3-TPD and FT-IR. Quantitative analysis of adsorbed d_3-acetonitrile on MCM-22 by IR spectra indicated that the concentration of Brnsted sites in these two samples was at the same level, while the concentration of Lewis acid sites in MCM-22-15 was higher than that of MCM-22-30. Both the two samples were active and selective for the skeletal isomerization of 1-butene. The MCM-22-15 sample showed relatively lower selectivity for isobutene (65.5%) than that of MCM-22-30 (74.8%), which might be explained by the happening of undesired side reactions when the density of Lewis sites increased in MCM-22-15.