Non-isothermal kinetic characterisation of a gas-solid reaction by TG analysis

Abstract

A series of silica-supported Ni-catalyst precursors was synthesized, with different SiO2/Ni mole ratios between 0.2 and 1.15. The reduction of all the prepared samples was studied by thermogravimetry (TG) in a hydrogen flow. The results of the TG analysis were analyzed by the multi-thermal history model-fitting method, with non-linear regression. The activation energies for the reduction of each sample were determined. The statistical F-test was performed to discriminate between various models. It was found that increasing the SiO2/Ni mole ratio leads to a change in the reaction mechanism of the nickel reduction, resulting finally in a change from second order reaction kinetics to three halves order reaction kinetics.