Kinetic study of nickel carbide oxidation

Abstract

Nickel carbide reacted with gaseous oxygen to yield nickel oxide and carbon dioxide as main products. The carbon dioxide formation reaction was deceleratory throughout and obeyed the equation [1–(1–α)^⅓]²=kt, 0.1 <α <0.8, where α was the fractional reaction at time t. The activation energy was 30 kcal mole^–1 and the index of oxygen pressure dependency of reaction rate was ∼0.15. Both carbidic and non-carbidic forms of carbon were oxidized in the reaction; relatively small changes in rate were caused by removal of the carbidic phase by (i) reduction with hydrogen or (ii) thermal decomposition. The kinetic characteristics of oxidation of the nickel-carbon mixtures resulting from nickel phthalate decomposition were closely similar to those found for a sample which was largely nickel carbide. Carbon oxidation occurs at an interface, between product nickel oxide and the metallic phase, which progresses through the reactant particles. Carbon dioxide formation shows some similarity with the nickel oxidation reaction; oxidation of both elements occurs at a single interface.