Infrared rhenium oxide

The kinetics of the metathesis of propene over a rhenium oxide-alumina catalyst (5.8% Rea07) have been studied by Kapteijn and Mol. The data correlate with a model based on the carbene mechanism and are in agreement with infrared and adsorption studies. Hsu has developed a kinetic model to express the time-on-stream profile of activity during catalyst break-in and deactivation. 

K. I. Petrov, V. V. Kravchenko, D. V. Drobot, and V. A. Aleksandrova, Russ.J. Inorg. Chem., 16, 928 (1971). Infrared Absorption Spectra of Rhenium Oxide Chloride. 

Papile, C. X, and Gates, B. C., Rhenium subcarbonyls on magnesium oxide Identification of the surface oxo and hydroxo ligands by infrared spectroscopy. Langmuir 8,74 (1992). 

The NO + MF, (except NO -f WF,) reactions proceed spontaneously at 20°. The reactions were followed tensimetrically. Gaseous products were identified by infrared spectroscopy and the solid products were examined by. y-ray powder-photography. Both ReF, and OsF, formed NO+[MF,] (cub.) salts and neither salt could be induced to combine with more NO to yield the quadrivalent (NO),MF, compound. In their reactions with nitrosyl fluoride at 20°, however, the rhenium and osmium fluorides are clearly differentiated ReF, readily forms a thermally stable 2 1 adduct, which is isomorphous with (NOjjWFg, whereas the OsF, -i- ONF reaction is complex. The identification of small quantities of nitrogen oxide trifluoride, in the gaseous product of the reaction, indicate the existence of an... 

The influence of the support is undoubted and spillover was further confirmed by the excess of hydrogen chemisorbed by a mechanical mixture of unsupported alloy and TJ-A1203 above that calculated from the known values for the separate components. It was also observed that the chemisorption was slower on the supported than on the unsupported metal and that the greater part of the adsorbate was held reversibly no comment could be made on the possible mediation by traces of water. On the other hand, spillover from platinum-rhenium onto alumina appears to be inhibited for ratios Re/(Pt Re) > 0.6. In an infrared investigation of isocyanate complexes formed between nitric oxide and carbon monoxide, on the surface of rhodium-titania and rhodium-silica catalysts, it seems that the number of complexes exceeded the number of rhodium surface atoms.The supports have a pronounced effect on the location of the isocyanate bond and on the stability of the complexes, with some suggestion of spillover. 

Oxidation tests have been carried out under xenon lamp heating and natural convection of air, where weight loss under constant temperature was monitored. The temperature was monitored by an infrared thermo-viewer and was calibrated with that of the tungsten-rhenium or platinum-rhodium thermo-couples. Temperature range examined was from 600 to 2300°C. Main features of this apparatus are that a large size specimen can be exposed and equilibrium constant temperature is rapidly attained (about 20s). 

The most serious disadvantage of CH3Re03-catalyzed oxidations is the problem of catalyst recovery. As can be easily seen by flic color of the reaction mixture or by infrared (lR)-spectra, CH3Re03 decomposes during flic reaction. Although the rhenium content may be recovered, total turnover would have to be much higher to ren-... 

There is a broad agreement that carbene species developed on partly oxidized transition metal ions are necessary to bring about the metathesis reaction. The data reported earlier provide support that the environment of the active site does possess acid properties. It has been proposed that there is a relationship between the Brpnsted acidity of the rhenium-based catalysts and the metathesis activity [52], and that the activity is not related to their Lewis acidity. Dynamic infrared spectroscopic experiments were conducted by poisoning a Re207/Al203 catalyst (8.0 wt% Re) under a propene flow [53], Ammonia adsorption gave rise to coordinated NH3 species, characterized by the bands at 1618, 1326, and... 

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