A high-vacuum cell attached to the external part of a BOMEM DA3 FTIR instrument is used for in situ transmission experiments on self-supporting zeolite wafers of 15-20 µ thickness, in the spectral range between 20 and 13800 cm"1 11. Results on zeolites Linde 4A and Linde 5A and on different Ag+-exchanged zeolites A in presence of reactants such as H20, D20, H2, D2, CO, and C02 demonstrate the high-quality information achieved by this technique. We have been able to obtain clear evidence for the appearance of Evans holes in the H20 and D20 stretching vibration on a zeolite A. Furthermore the stretching plus bending bands, the bending plus librational combination bands, and new OH stretching frequencies have been observed. Far-IR spectra of the silver species, the development of new structural OH and OD groups, and the overall transmission have been followed during the reduction of Ag-A zeolites with H2 and D2. At different stages of reduction, interaction of CO and C02 has been probed and revealed interesting information on structural changes and kinetics under different conditions.The method and data reported open a wide field for detailed investigations on the interaction of metal exchanged zeolites with gaseous reactants.
We show an iterative algorithm that allows to obtain accurate Compton profiles J(q) from Compton scattering spectra I2 (ω2), if the excitation radiation is not strictly monochromatic. It requires knowledge of the spectral distribution of the primary radiation I1(ω1), validity of the impulse approximation and dominance of a monochromatic part in I1(ω1) over the polychromatic rest. Conversely, the primary spectrum is often experimentally not directly accessible. In such a situation it is possible to evaluate the primary spectrum I1(ω1) from the spectrum of scattered photons, I2(ω2), with a similar iterative algorithm. We use a scattering target of high atomic number in order to ensure that the elastically scattered photons dominate the inelastically scattered ones. From the scattered spectrum we get a model for the Compton profile that allows us to separate the inelastic part of the scattered spectrum from the elastic part, which, in turn, is proportional to the spectral distribution of the primary radiation.
A new FTIR technique covering the spectral range 20‐13800 cm‐1 is used for detailed investigations of the interaction of metal exchanged zeolites with gaseous reactants such as H2O, D2O, CO, CO2, H2, and D2.
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