Kinetics of Reduction of Nickel Oxide With Hydrogen Gas in the 230-452°c Range

The kinetics of reduction with hydrogen of thin, dense strips of NiO in the 230-452°C temperature range were measured by the thermogravimetric technique. Pure hydrogen gas at 1 atm was used as the reducing agent. The fractional conversion-time curves were sigmoid-shaped, indicative of the autocatalytic nature of the reduction process. As relatively thin (54 μm thick) specimens were employed, the pore-diffusion of gases offered only negligible resistance. The topochemical-reaction-rate constant kc, deduced from the measured rates using nominal surface area, is found to be given by In kc= 14.770(±0.536)−11,673(±325) T−1 where kc is in cms−1. The activation energy for the reduction process appears to be 23.2 (±0.65) kcal mole−1 in the 230-452°C range.