In situ X-ray diffraction (XRD) and NMR methods were used to follow the structural changes that occur during the dismutation reaction of hydrochlorofluorocarbon-22 (CHClF(2)) over gamma-alumina. Use of a flow cell allowed diffraction patterns to be recorded, while the reaction products were simultaneously monitored downstream of the catalyst bed, by gas chromatography. No visible structural changes of gamma-Al(2)O(3) were observed at 300 degrees C, the temperature at which this material becomes active for catalysis. A new phase began to form at 360 degrees C, which by 500 degrees C completely dominated the XRD powder pattern. (19)F/(27)Al cross-polarization (CP) experiments of gamma-Al(2)O(3) activated at 300 degrees C showed that AlF(3) had already begun to form at this temperature. By 400 degrees C, resonances from a phase that resembles alpha-AlF(3) dominate both the (19)F and (27)Al NMR spectra of the used catalyst. In situ XRD experiments of the catalytically inactive alpha-AlF(3) phase were performed to investigate the structural changes of this material, associated with the extent of tilting of the AlF(6) octahedra in this ReO(3)-related structure, as a function of temperature. Structural refinements of this sample, and the catalytically active phase that grows over gamma-Al(2)O(3), demonstrate that the catalyst is structurally similar to the rhombohedral form of alpha-AlF(3). Differences between the two phases are ascribed to defects in the catalyst, which limit the flexibility of the structure; these may also be responsible for the differences in the catalytic behavior of the two materials.

Three ethylene adducts to CuAlCl(4) have been characterized by single crystal and/or powder X-ray diffraction, (13)C, (27)Al and (63)Cu MAS NMR and diffuse reflectance UV-vis spectroscopy. (C(2)H(4))(2)CuAlCl(4), a = 7.1274(5) b = 12.509(1) c = 11.997(3) beta = 91.19 degrees, Pc, Z = 4; alpha-(C(2)H(4))CuAlCl(4), a =7.041(3) b = 10.754(8) c =11.742(9) beta = 102.48(6), P2(1), Z = 4 and beta-(C(2)H(4))CuAlCl(4), a = 7.306(2), b = 16.133(3), c = 7.094(1), Pna2(1), Z = 4. Up to 2 equiv of ethylene ( approximately 200 cm(3)/g relative to stp) are sorbed at room temperatures and pressures as low as 300 Torr. The ethylene ligands are bound to copper (I) primarily through a sigma-interaction, because the AlCl(4)(-) groups also bound to copper prevent any significant pi-back-bonding. The olefin binding is reversible and has been characterized by gravimetric and volumetric adsorption analysis and by time and pressure resolved synchrotron powder X-ray diffraction. Comparison of the parent crystal structure to those of the adduct phases provide an atomistic picture of the sorptive reconstruction reactions. These are proposed to proceed by a classic substitution mechanism that is directed by the van der Waals channels of the parent crystalline lattice.

Solid-state MAS NMR and synchrotron X-ray powder diffraction have been used to study the reactivity and structure of Zn2+-exchanged NaX. Dehydrated ZnX with a Zn:Na ratio of 3.6:1 was refined in the space group Fd3m. The zinc cations were located in four distinct positions all along the [111] direction. Residual sodium cations were found in the supercage at the site II position. A tetrahedral extraframework aluminum species, AlO4 5-, was refined in the center of the sodalite cage; this anion was also observed by 27Al MAS NMR. The reactions of hydrochlorofluorocarbon (HCFC)-124a (CF2HCF2Cl) over NaX, and two Zn2+-exchanged NaX samples, were studied with NMR and a mass spectrometry (MS)-equipped catalysis unit. The products of both the dehydrofluorination and dehydrochlorination reactions are observed over all zeolites:  the unsaturated products (CF2CF2 and CF2CFCl) desorb from the zeolites and are detected by MS. In contrast, saturated products are primarily observed when the reaction is followed with 19F NMR in sealed ampules. Both CF2CF2 and HFC-125 (CF3CF2H) are observed for reactions over NaX, while on Zn2+ exchange, CF2CF2 is no longer observed. Instead, a resonance is observed at −123 ppm, which is tentatively assigned to (CF2) n groups. No evidence is seen by 27Al and 19F NMR for attack of the zeolite framework when the reactions are performed at low temperatures. An in situ X-ray diffraction study of HCFC-124a loaded ZnX shows significant structural changes at the same temperature as the onset of HCFC reactivity.