164.    BAUKLOH, W., AND HENKE, G.  [Effect of Metals and Metal Oxides on the Decomposition of Carbon Monoxide and Its Technical Significance.]  Metallwirtschaft, vol. 19, 1940, pp. 463-470; Chem. Abs., vol. 36, 1942, p. 317.

                  At 500°-600°, Fe oxides and cast Fe cause decomposition of CO accompanied by deposition of C according to 2CO=CO₂+C, by strong loss of Fe from the oxides, and by destructive action on cast Fe.  Fe-containing ceramic materials are also destroyed.  The harmful effects occur only in the temperature and pressure range in which Fe, Fe oxides, C, CO, and CO₂ coexist.  The maximum effect on decomposition of CO is shown at 500°.  The oxides have virtually no effect on the decomposition; Fe metal itself is the catalytic agent.  Decomposition occurs in the adsorption layer and is proportional to the amount of CO adsorbed.  H₂O vapors retard CO decomposition by preventing formation of metallic-Fe surfaces.  When CO is passed over Fe₂O₃ at 550°, the maximum rate of decomposition is reached at a streaming velocity of about 1 cm. or 2 cc./sec.; a marked maximum rate of decomposition at 1 atm. pressure occurs around 500°; below 400° and above 800°, virtually no deposition of C was observed.  The maximums are eventually the same whether Fe, Fe₂O₃, FeO, or Fe₃O₄ is used; the initial activity is greater the lower the temperature at which reduction to Fe took place.  Sintering is rapid above 600°.  Addition of 1% (CN)₂, NH₃, or H₂S reduces the deposition of C by as much as 95%.  Near 500° the oxides of Fe, Co and Ni cause deposition of C; the maximum effects are at 500° for Fe₂O₃ and at 700° for NiO and CoO Mg, Ca and Ba oxides and Fe₂SiO₅ are weak catalysts; the oxides of Cu, Ag, Zn, Al, Ti, Si, V, Cr, Mo, W, U, Mn, C, SiC, and FePO₄ are inert.  Of the free metals, only Fe, Co, and Ni are strongly active; Mg, Al, Ce alloys, and Ti, Cr, and Mn react with CO and cause deposition of C.  Ag, Cu, Zn, Si, Mo, W, Pd, and Pt are inert.  The destructive action of CO on various materials as firebricks can be prevented by avoiding the harmful-temperature and pressure limits, by removal of Fe, Co, and Ni, by conversion of the oxides of Fe, Co, and Ni to compounds such as the silicates or phosphates, which are not reduced to the metal, or by protective glazes.  Experiments on the destructive action show that it is due to very strong mechanical forces of crystallization of the deposited C.