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

Abstract

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.