Single-crystal Structure of Cd2+-exchanged Zeolite Y (FAU, Si/Al = 1.56), |Cd27.5(Cd8O4)2.5|[Si117Al75O384]-FAU

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Zeolite framework contains channels and windows and interconnected voids which are occupied by the cations and water molecules. The cations are quite mobile and may usually be exchanged by other cations. Ion exchange is the most important method for the modification of the physical and chemical properties of zeolites for use as catalysts, sorbents, and molecular sieves. The results of ion exchange into zeolites from aqueous solution are usually not simple. Often only a fraction of the original cations can be replaced, and attempts to overcome this may reveal a relatively sharp upper limit to exchange. When acetate salt of metal cations dissolves in water for exchange solution, metal hydroxide ions occurred. It can be exchanged for Na ions into zeolite framework, leading to over exchange. The catalytic activity of Cd-exchanged zeolite Y for the formation of acetonitrile was studied for comparison with activated alumina (Al2O3) and also examined for the formation of acetonitrile from ethane and ammonia. Its catalytic activity had much higher than that of Al2O3. It was found to be essentially inactive for the formation of acetonitrile from ethylamine. When zeolite Y (Si/Al = 1.69) was ion exchanged in aqueous stream 0.05 M in Cd (0.025 M Cd(NO3)2 and 0.025 M Cd(C2H3O2)2) for 5 days and dehydrated at 723 K and 2 × 10 Torr for 2 days, the resulting composition, |Cd27.5(Cd8O4)2| [Si121Al71O384]-FAU, indicated that eight molecules of Cd(OH)2 had been imbibed per unit cell. With eight nonframework oxides, two Cd8O4 clusters had formed per unit cell. It was stated that the ability of Cd ions to hydrolyze at pH 7 facilitated this process, as did the ability of the sodalite unit to host and stabilize Cd4(OH)4 clusters. This study was done to investigate the behavior of Cd in Cd-exchanged zeolite Y (Si/Al = 1.56) prepared at high ion-exchange temperature (353 K), with the expectation of forming more cadmium oxide cluster, Cd8O4. Synchrotron X-ray diffraction data were collected at 100 (1) K using an ADSC Quantum 210 detector at Beamline 6B MXI at the Pohang Light Source. Crystal evaluation and data collection were done using λ = 0.90000 A radiation with a detector-to-crystal distance of 60 mm. Preliminary cell constants and an orientation matrix were determined from 72 sets of frames collected at scan intervals of 5 with an exposure time of 1 second per frame. The basic scale file was prepared using the program HKL 2000. The reflections were successfully indexed by the automated indexing routine of the DENZO program. The 87,989 reflections were harvested by collecting 144 sets of frames with 5 scans and an exposure time of 1 second per frame. These highly redundant data sets were corrected for Lorentz and polarization effects, and (negligible) corrections for crystal decay were also applied. The cubic space group was determined by the program XPREP. The summary of the experimental and crystallographic data is presented in Table 1. Full-matrix least-squares refinement (SHELXL97) was done on Fo using all data. Refinement was initiated with the atomic parameters of the framework atoms [(Si,Al), O(1), O(2), O(3), and O(4)] in dehydrated |Tl75| [Si117Al75O384]-FAU. Initial refinement used anisotropic thermal parameters and Fd3m