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Siting of copper ions in Cu^I−Y zeolite, prepared by gas-phase exchange of NH4−Y with CuCl, has been investigated employing XRPD, XAS and IR spectroscopies. An X-ray powder diffraction study of the zeolite in a vacuum shows that 23.4(2) cuprous ions are located at site I*, 6.1(3) at site II, and 11.5(3) at site II* (sites I* and II* are at the center of the plane of the six-membered ring connecting the hexagonal prism with the sodalite and the sodalite with the supercage, respectively). Addition of CO induces a relevant migration of copper ions from sites II and II* to a more exposed type II. EXAFS analysis shows that Cu^I ions in the outgassed zeolite are surrounded by 2.8(3) oxygen atoms of the zeolite framework, the average Cu^I−O distance being 1.99(2) Å. Both X-ray measurements and FTIR spectroscopy show that CO is adsorbed on the zeolite at room temperature with formation of carbonyl adducts. At liquid-nitrogen temperature and low CO pressure, two types of monocarbonyl species are observed, corresponding to CO adsorbed on copper ions located at sites II and II*. On increase of the CO pressure and subsequent formation of polycarbonylic species, cations at site II* move to the more exposed position II, and a single kind of tricarbonyl adducts is observed. IR spectroscopy also provides evidence for the interaction of NO with copper ions located at sites II and II*, which are the first sites able to adsorb up to two molecules of NO, whereas cations at site II*, because of their lower coordinative unsaturation, can only form Cu^I(NO) adducts. NO proves to be a sensitive probe not only for cuprous but also for cupric ions.

The effect of aging and heating treatments up to 500 K on alumina-supported CuCl2, i.e., the base catalyst for ethylene oxychlorination, has been investigated by UV–vis spectroscopy, a solubility test, EXAFS, XRD, and EPR in a wide range (0.25–9 wt%) of Cu concentration. It is shown that the catalyst undergoes significant changes with both time and thermal treatments, so accounting for some contradictory results reported in the literature. While the surface Cu aluminate (formed during impregnation) does not change upon aging and heating, supported CuCl2 (precipitated from impregnating solution during the drying process) undergoes a slow hydrolysis reaction with the formation of paratacamite and HCl. The HCl formed during the hydrolysis reacts with the alumina surface with the formation of >Al–Cl species. Upon heating, the initially formed paratacamite can react with surface >Al–Cl species with nearly total restoration of CuCl2, which is consequently the main species present on the catalyst at the beginning of the oxychlorination reaction. The obtained picture is able to explain the results emerging from activity tests on the whole set of catalysts, indicating that surface aluminate is not active and that the active phase is CuCl2.

High-quality powder XRD data of a dehydrated Na−Rb−Y zeolite with Si/Al = 2.7, collected at the ESRF beam line BM16, are analyzed. The quality of the Rietveld refinement is very satisfactory, as confirmed by the low Rwp and Rp values of 7.77% and 6.02%, respectively, and by the comparison of the Rb⁺/Na⁺ ratio (1.36(6)) with the experimental one (1.38) obtained by analytical methods. We have found that 9.3(3) Na⁺ cations are located in site SI, 8.3(6) Na⁺ and 5.4(6) Rb⁺ cations in site SI‘, and 2.9(6) Na⁺ and 22.4(6) Rb⁺ cations in site SII. No cations have been observed in site SIII. Less than 4 cations out of 51.8 remain to be located in the unit cell, which has a cell parameter of a = 24.7673(4) Å, (V = 15192.8(7) ų). The low occupancy by Na⁺ of sites in the supercage (site SII) is confirmed by a parallel IR study of CO and N2 adsorbed at low temperature, where carbon monoxide and dinitrogen have been found to interact mainly with the Rb⁺ cations. The spectroscopic study of the stretching vibrations of Na⁺···CO and Na⁺···N2 adducts allows the estimation of a Rb⁺/Na⁺ ratio of approximately 9 in site SII, in close agreement with the ratio obtained from the Rietveld refinement, 8(2).