The crystal structure of hydrated thallium-exchanged zeolite X

Abstract

The crystal structure of hydrated TP-exchanged zeolite X has been determined by single-crystal X-ray diffraction techniques. The compound crystallizes in space group FdSm (o = 25.089 (5) A). Reflection data were collected with Cu ( 1.54182 A) radiation using a synthetic crystal with a maximum dimension of approximately 0.1 mm. A total of 281 observed reflections was obtained by counter methods and the structure was refined by least-squares techniques to a final conventional R factor of 0.13. TP ions are located inside the sodalite cages in front of the hexagonal prisms (site ) and in front of the six-membered ring face of the sodalite cage on the supercage side (site II). No water molecules and only 52% of the cations could be located. Unlocated cations and water molecules were included as uniformly distributed spheres.The shortest TP-0 distancés are 2.64 (5) and 2.79 (5) A.

Neutron Diffraction and Computational Study of Zeolite NaX: Influence of SIII‘ Cations on Its Complex with Benzene

“…However, in the case of monovalent cation forms of zeolite X, a significant proportion of the cations are often undetected in X-ray studies. In hydrated NaX, KX, and TlX, for example, the proportion of undetected cations is almost 50%, leading Baur to conclude that many of the water molecules and exchangeable cations in faujasite zeolites move freely through the aluminosilicate framework. The dehydrated forms of zeolites find utility in a number of commercial separation processes, including air − and hydrocarbon separations, and a comprehensive determination of the cation positions in such materials is an important prerequisite for understanding their properties. , It is surprising to find, therefore, that in the prototypical system, NaX, where the numbers of cations in the SI, SI‘, and SII sites (Figure ) appear to be well-established, the precise location of the remaining cations remains uncertain.…”