A study on the adsorption of carbon monoxide on silica supported Ru-Fe alloy

We have investigated the infrared spectra for CO adsorbed on silica supported Ru/Fe alloys at various CO partial pressures and varying mole fractions of Ru and Fe within the frequency range of 1500 cm/sup -1/ /spl sim/ 2500 cm/sup -1/. Four bands (2080.0 cm/sup -1/, 2028.0 cm/sup -1/, 1934.0 /spl sim/ 1970.9 cm/sup -1/, 1621.8 cm/sup -1/) were apparently observed for the 4% Ru/Fe-SiO/sub 2/ sample below 70 mole % Ru in the supported alloys as varying CO partial pressures at 25 . Five bands (2138.7 /spl sim/ 2142.5 cm/sup -1/, 2067.3 /spl sim/ 2073.1 cm/sup -1/,1988.3 /spl sim/ 2030.7 cm/sup -1/,1774.2 /spl sim/ 1799.3 cm/sup -1/,1623.8 cm/sup -1/) were apparently observed for the 4% Ru/Fe-SiO/sub 2/ sample above 95 mole % Ru in the supported alloys as varying CO partial pressures at 25 . The 1988.3-2030.7 cm/sup -1/ band due to CO molecules lineally bonded to the ruthenium atoms and the 1934.0 /spl sim/ 1970.9 cm/sup -1/ band due to CO molecules lineally bonded to the iron atoms for the 4 % Ru/Fe-SiO2 sample showed comparatively large blue shifts as CO pressures were gradually increased. The absorbances of the 1934 /spl sim/ 1970.9 cm/sup -1/ band gradually increased with the increases of ruthenium contents from 0% ruthenium mole fraction to 60% unexpectedly. This phenomena may be explained due to the increases of the CO band extinguishing coefficients with the increases of ruthenium contents, CO being bonded to iron atoms on Ru/Fe-SiO/sub 2/ samples or due to the increases of the number of iron atoms on Ru/Fe alloy cluster surface.