Powder neutron diffraction, zeolite studies

G. Vitale, C. F. Mellot, and A. K. Cheetham,/. Phys. Chem. B, 101, 9886 (1997). Localization of Adsorbed Cyclohexane in the Acid Form of Zeolite Y. A Powder Neutron Diffraction and Computational Study. 

A.N. Fitch, H. Jobic A. Renouprez (1986). J. Phys. Chem., 90, 1311-1318. localisation of benzene in sodium Y zeolite by powder neutron diffraction. (Somewhat less detailed is R. Goyal, A.N. Fitch, H. Jobic (2000). J. Phys. Chem., B104, 2878-2884. Powder neutron and X-ray diffraction studies of benzene adsorbed in zeolite ZSM-5.)... 

Neutron scattering techniques are increasingly being used to study the structure and dynamics of molecules adsorbed in nanoporous materials. The most prominent example is neutron diffraction, which is complementary to X-ray diffraction to solve structural problems in zeolites and other microporous materials [1]. While the use of powder neutron diffraction is well established in the zeolite community, the spectroscopic applications of neutron scattering are less familiar. However, the constant amelioration of the neutron instrumentation and of the theoretical models provides unprecedented insights into the dynamics of the framework and of adsorbed molecules, at the atomic and... 

Chem., 106, 66 (1993). Powder Neutron Diffraction and Si MAS NMR Studies of Siliceous Zeolite-Y. 

The resurgence of interest in the field of zeolite chemistry, which has been stimulated by the appreciation of their enormous potential as catalysts, has led to the application of several sophisticated physical methods in the study of their structural properties. Important advances have already been made using high resolution, solid state NMR (1,2) and electron microscopy (3), and in this paper we discuss the scope and limitations of neutron diffraction studies with powder samples, with some specific applications to zeolite-A and synthetic faujasite. 

Understanding of the modification from bulk liquid water behavior when water is introduced into pores of porous media or confined in the vicinity of metallic surfaces is important in technological problems such as oil recovery from natural reservoirs, mining, heterogeneous catalysis, corrosion inhibition, and numerous other electrochemical processes. Water in porous materials such as Vycor glass, silica gel, and zeolites has been actively under investigation because of their relevance in catalytic and separation processes. In particular, the structure of water near layer-like clay minerals [11,12], condensed on hydroxylated oxide surface [13], confined in various types of porous silica [14-22] or in carbon powder [23] has been studied by neutron and/or x-ray diffraction. 

A High Resolution Silicon-29 NMR and Neutron Powder Diffraction Study of Na-A Zeolite Loewenstein s Rule Vindicated... 

Vitale G., Bull L. M., Morris FL E. and Cheetham A. K., Combined neutron and X-ray powder diffraction study of zeolite CaLSX and a H NMR study of its complex with benzene. J. PAys. Chem. 99 (1995) pp. 16087-16092... 

J.B. Parise, L. Abrams, T.E. Gier, D.R. Corbin, J.D. Jorgensen E. Prince (1984). J. Phys. Chem., 88, 2303-2307. Flexibility of the framework of zeolite rho-structural variation from 11 to 573 K-a study using neutron powder diffraction data. 

By the 1980s most of the aluminosilicate zeolites currently used industrially were known, and the emphasis shifted to the study of these materials using a range of powerful new techniques that came of age at this time. These included, in particular, solid state NMR, X-ray and neutron powder diffraction analysis, high resolution electron microscopy and computational methods. All were ideal for the study of structural details of solids that were rarely available, and never used in industrial applications, other than as microcrystalline powders. All these techniques are applicable to the bulk of the solid - this in turn makes up the (internal) surface, which is accessible to adsorbed molecules. Since the techniques are able to operate under any conditions of gas pressure, they may be used to extract structural details in situ under the operating conditions of ion exchange, adsorption and catalysis. In particular, zeolitic systems have proved ideal for the study, understanding and subsequent improvement of solid acid catalysts. 

Diffraction studies have been used in a small number of cases to determine the minimum energy positions of adsorbed moleeules within cationic zeolites. These difficult and relatively expensive experiments have been used to establish computational simulation as a reliable method to predict such interactions without recourse to experimentation. Crystallographic X-ray studies of the adsorption of small moleeules sueh as CO and NO on cationic forms of zeolite are of particular relevance to study of eation-molecule interactions, as are neutron powder diffraction studies of the location of pyridine, coordinatively bound to potassium ions in zeolite K-L, and of benzene, bound to sodium ions in zeolite Na-X. ... 

---