CHEMICAL CHARACTERIZATION OF MOLECULES ADSORBED ON A FOREIGN SOLID.
Final rept. 1 Nov 64-31 Oct 68,
VIRGINIA INST FOR SCIENTIFIC RESEARCH RICHMOND DEPT OF CHEMISTRY
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Spectroscopic techniques have been applied to the study of surface structures of catalysts of supported transition metals. Infrared, visible ultraviolet and Mossbauer spectroscopy have been used, but Mossbauer spectroscopy was found to be the most powerful one for investigation of the adsorbent using iron and its compounds supported on silica gel and alumina. Microcrystallite size of ferric oxide on silica gel and alumina was calculated by Kundigs method from Mossbauer spectra of the catalysts. It was found that reproducible results could be obtained with the silica gel samples, but that the method was severely limited for the alumina samples because of compound formation between the ferric oxide and the alumina. In addition to the compound formed with the alumina support, a ferrous oxide species was observed on reduction of both silica gel and alumina samples. This species did not have the Mossbauer parameters of wustite and could not be observed by x-ray diffraction analysis. For catalyst samples having the smallest crystallite size, 30 to 50 A, two distinct species could be resolved in the spectra of the reduced state. The compounds could be classified in an order of decreasing ability to affect the intensity of the spectrum as follows ammonia, trimethylamine, methanol acetonitrile carbon monoxide, hydrogen.
- Atomic and Molecular Physics and Spectroscopy