摘要
用x-射线粉末衍射法研究了两种ZSM-5沸石的晶体结构。两者同属Pnma空间群,晶胞参数分别为:5001—a=20.118(?),b=19.923(?),c=13.410(?);5020—a=20.048(?),b=19.884(?),c=13.352(?)。两者基本结构形貌相近,但与5001相比,5020的骨架结构内存在更大的“应力”,因而较易遭到破坏,两种样品的孔道开口直径分别为:5001-正弦形通道5.080—5.650(?),平均5.367(?),直通道5.207—5.390(?),平均5.307(?);5020—正弦形通道5.111—5.655(?),平均5.368(?),直通道4.993—5.404(?),平均5.226(?)。两者正弦形通道开口尺寸和形状十分接近,而直通道开口尺寸和形状有一定差异,这种孔道结构上的差异是二者性能差别的一个不可忽视的原因。
The crystal structure of two ZSM- 5 zeolites has been investigated by means of X- ray powder diffraction method. They all belong to Pnmaspace group. Cell parameters are. 5001-a=20. 118A , b = 19. 923A, c=13. 410A; 5020-a = 20. 048A, b= 19. 884 A, c=13. 352A. The structural topology of these two samples are essentially identical, but the framework of 5020 is more 'strained' and thus can be deforme'd more easily as compared to that of 5001. The average opening sizes of the sinusoidal channels are 5. 367A (5.080-5. 650A) and 5. 368A (5. 111 - 5. 655A) for 5001 and 5020 respectively; and those of straight ones are 5. 307A (5. 207 - 5. 390A) and 5. 226A (4. 993 - 5. 404 A ). The opening sizes and shapes of sinusoidal channels of two zeolites are very similar, but those of straight ones are more distinct. The difference of channel geometry may be one of the factors responsible for the discrepances between their properties. For example, the straight channel of 5020 is smaller and is distorted more seriously than that of 5001, so the number of irreversible adsorbed cyclohexane molecules in a unit cell of 5020 is less than that of 5001, and the intra-crystal diffusion is more difficult for 5020.
出处
《分子催化》
EI
CAS
CSCD
1992年第2期104-112,共9页
Journal of Molecular Catalysis(China)
基金
山西省自然科学基金资助课题
关键词
吸附
XSM-5沸石
晶体结构
衍射
ZSM -5 zeolites, Crystal structure, X-ray powdew diffraction.
