Infrared studies of carbon monoxide and hydrogen adsorbed on silica-supported nickel catalysts. [Effects of temperature]

The interaction of CO and H/sub 2/ on silica-supported nickel was studied using infrared spectroscopy. The products occurring in the gas phase, as well as adsorbed CO spectra of the surface species in the frequency range 2300-1700 cm/sup -1/ for different order of addition of the two reactants was examined. It was found that: (i) CH/sub 4/ formation occurred at temperatures above 190 +- 5/sup 0/C. (ii) A band attributed to linearly held adsorbed CO, at 2080 cm/sup -1/ when at room temperature, was correlated with CH/sub 4/ formation. (iii) Gaseous Ni(CO)/sub 4/ was formed at room temperature when only CO was present or providing the catalyst was pretreated with CO before the addition of H/sub 2/. (iv) A band which occurred at 2055 cm/sup -1/ was correlated with the formation of Ni(CO)/sub 4/. (v) Heating the system caused bands attributed to adsorbed CO to shift to lower frequencies. On cooling, the frequency shift occurred in the opposite direction but followed a different path. On further heating and cooling this shift became temperature reversible.