KINETICS OF REDUCTION OF NICKEL OXIDE WITH HYDROGEN GAS IN THE 230-452°C RANGE

Abstract

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 k_c, deduced from the measured rates using nominal surface area, is found to be given by

In k_c= 14.770(±0.536)−11,673(±325) T⁻¹

where k_c 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.

Keywords:

• Hydrogen
• kinetics
• reduction
• nickel oxide
• morphology
• mass transfer