Location of water and xylene molecules adsorbed on prehydrated zeolite BaX. A low-temperature neutron powder diffraction study

The structure of partially hydrated zeolite BaX containing adsorbed deutera ted molecules of p- or m-xylene was studied at low temperature by neutron p owder diffraction, The powder patterns were refined with the GSAS software package using the Rietveld method. The adsorption sites for water? p-xylene , and m-xylene were characterized. There are two adsorption sites for water molecules located in the sodalite cage and in the supercage, respectively. The isomers of xylene were found near the cations in the supercage in agre ement with the literature data, but in addition, one "noncationic" site was found for p-xylene. The adsorption of these molecules dramatically influen ces the distribution of the cations. The influence of the water preadsorpti on on xylene adsorption selectivity is discussed.