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Ambient temperature adsorption isotherms have been determined for methyltert-butyl ether (MTBE) in aqueous solutions on high silica ZSM-5 and Y zeolites which differ from each other in framework topology and pore window apertures.

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Adsorption equilibria of methyl tert-butyl ether (MTBE)/toluene (TOL), and 1,2-dichloroethane (DCE)/MTBE binary mixtures in aqueous solution on ZSM-5 were measured over a wide range of concentrations. In comparison with the single-component data, the loading of all of the three compounds was reduced in the presence of a second component in the mixture. The binary system was described by a competitive dual site Langmuir adsorption isotherm. The model was chosen on the basis of the results obtained from X-ray diffraction studies of the adsorbent material loaded with equimolar binary mixtures. Rietveld structure refinements provide information about the relative position of molecules inside the structure after TOL-MTBE and DCE-MTBE mixture adsorption. The short intermolecular distances between the adsorption sites of MTBE, DCE and TOL inside the zeolite framework clearly prevent the simultaneous occupancy of one site by more than one component, when these compounds are adsorbed from binary mixtures

Abstract:The temperature-induced desorption of methyl tert-butyl ether (MTBE) from aqueous solutions onto hydrophobic ZSM-5 was studied by in situ synchrotron powder diffraction and chromatographic techniques. This kind of information is crucial for designing and optimizing the regeneration treatment of such zeolite. The evolution of the structural features monitored by full profile Rietveld refinements revealed that a monoclinic (P2 1 /n) to orthorhombic (Pnma) phase transition occurred at about 100 • C. The MTBE desorption process caused a remarkable change in the unit-cell parameters. Complete MTBE desorption was achieved upon heating at about 250 • C. Rietveld analysis demonstrated that the desorption process occurred without any significant zeolite crystallinity loss, but with slight deformations in the channel apertures.