Surface modifications of cobalt Fischer Tropsch catalyst followed by operando DRIFT and chemometrics

Abstract : Operando DRIFT analysis of the surface species observed on Fischer Tropsch catalysts at work has beenperformed under H2/CO syngas at 503 K. Decomposition of the evolution in the IR operando spectra hasbeen done by chemometric analysis in order to depict the modifications occurring on the surface ofthe nanoparticles as a function of time on stream. Results obtained on three catalysts with differentreducibility determined from temperature programmed reduction experiments are confronted in orderto correlate the spectral observations to the cobalt surface atoms speciation. Attribution of the IR com-ponents in the 2100–1750 cm−1range is confirmed on the basis of the chemometric decomposition.The component falling in the 2068–2064 cm−1range is assigned to CO sorbed onto Co◦surface atomsof partially H2-reduced nanoparticles. This component is found to progressively decrease as a functionof catalyst time on stream which indicates a progressive reduction of the nanoparticles under syngas at503 K.