Havenga Edward A, Huang Yining
The Department of Chemistry, The University of Western Ontario, London, Ontario, Canada N6A 5B7.
J Phys Chem B. 2005 Sep 29;109(38):18031-6. doi: 10.1021/jp058159r.
In the present work, binary adsorption of p-xylene and toluene in completely siliceous zeolite ZSM-5 was examined by FT-Raman spectroscopy in combination with powder X-ray diffraction. The results indicate that at total loadings of < or = 4 molecules per unit cell (u.c.) both p-xylene and toluene molecules prefer to reside at the intersections of straight and zigzag channels. The structure of the sorbate/sorbent complexes likely belongs to orthorhombic. At high loadings of 7 and 8 molecules/u.c., the framework of the zeolite transforms to another orthorhombic phase. In this high-loaded phase, toluene molecules are distributed evenly in both the channel intersection and the midsection of straight channel. Although p-xylene has access to both the channel intersection and the zigzag channel, it does show a slight preference for the channel intersection. The adsorptive behavior of these aromatics at intermediate total loadings of 5 and 6 molecules/u.c. is more complicated because the zeolitic framework is a mixture of two different orthorhombic phases.
在本工作中，采用傅里叶变换拉曼光谱结合粉末X射线衍射对全硅ZSM-5沸石中对二甲苯和甲苯的二元吸附进行了研究。结果表明，在每晶胞（u.c.）总负载量≤4个分子时，对二甲苯和甲苯分子都倾向于位于直通道和之字形通道的交叉处。吸附质/吸附剂复合物的结构可能属于正交晶系。在7和8个分子/u.c.的高负载量下，沸石骨架转变为另一种正交晶相。在这个高负载相中，甲苯分子均匀分布在通道交叉处和直通道的中间部分。尽管对二甲苯可以进入通道交叉处和之字形通道，但它确实对通道交叉处表现出轻微的偏好。在5和6个分子/u.c.的中等总负载量下，这些芳烃的吸附行为更为复杂，因为沸石骨架是两种不同正交晶相的混合物。
