Effect of hydrogen on carbon deposition from carbon monoxide on nickel catalyst

The role of hydrogen in carbon deposition on Ni has been studied at H2/CO < 1 and 698 K by determining the respective rates of the carbon-forming reactions: (1) CO + H2 →-C + H2O and (2) 2CO → C + CO2. The steady-state rate of reaction (1) increases in proportion to H2 pressure. On the other hand, reaction (2) is facilitated by the addition of an extremely small amount of H2, so that the rate becomes about eight times that for pure CO but hardly varies as more H2 is added. Similarly, there is a great difference in catalytic activity for ethylene hydrogenation between spent catalysts obtained in the deposition with and without H2. These findings suggest that hydrogen, even in a small amount, makes free Ni surface area larger than for pure CO.