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/Nimole 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.

Niz prekursora Ni katalizatora, na silikatnom nosaču je sintetisan sa različitim SiO 2/Ni molskim odnosima, između 0,2 i 1,15. Redukcija svih pripremljenih uzoraka je proučavana termogravimetrijski (TG) u protoku vodonika. Na rezultate TG analiza je primenjena „metoda fitovanja modelima iz višestruke termalne istorije” sa nelinearnom regresijom. Energije aktivacija su određene za proces redukcije na svim uzorcima. Statistički F-test je korišćen za diskriminaciju među modelima. Nađeno je da povećanje SiO2/Ni molskog odnosa vodi promeni reakcionog mehanizma redukcije Ni, što na kraju dovodi do promene kinetike od reakcije drugog reda do reakcije reda 3/2.