Thermal decomposition of nickel fumarate

Abstract

Nickel fumarate decomposed in vacuum at 300–340°C to yield carbon dioxide and nickel carbide as the principal products, smaller amounts of carbon monoxide, methane and hydrocarbons. The reactant did not melt during pyrolysis. Some 2 % of the gaseous products were evolved in an initial deceleratory reaction. This was rapidly followed by, and partially overlapped with, the acceleratory period of the main reaction which was a typical sigmoid-shaped (fractional decomposition (α), time) relation, characteristic of decomposition reactions of solids which involve nucleation and growth of a product phase. Kinetic analyses showed that the activation energy of this reaction was 208±8 kJ mol^–1, the reaction frequency factor was estimated to be 3 × 10³⁵ mol.m^–2 s^–1 and the acceleratory region of the reaction obeyed the power law, n= 2, 0.03< α< 0.5.

Electron micrographs showed that reactant crystallites did not disintegrate during decomposition and there was evidence that reaction occurred at nuclei established within the crystals. A reaction mechanism is proposed to account for these observations. It is suggested that catalytic type decomposition of the fumarate anion was the rate-controlling process. This reaction proceeded at the surfaces of approximately cylindrical nuclei, initially established at lines of dislocation within the reactant crystallites, and which grew thereafter into the undecomposed material.