Catalytic Behaviour of CuO-CeO2 Systems Prepared by Different Synthetic Methodologies in the CO-PROX Reaction under CO2-H2O Feed Stream

Abstract

CuO-CeO2 catalysts, with 6 wt % of Cu, have been synthesised by different preparation methods (calcination of nitrate precursors, thermal urea-nitrate combustion, freeze-drying method, using polymethyl metacrylate PMMA microspheres as template and precipitation using NaOH or the decomposition of urea as precipitating agents). The obtained materials have been characterised by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, N2 adsorption-desorption at −196 °C, H2 thermoprogrammed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The catalysts displayed high dispersion of copper oxide, obtaining CO conversion values of 90–100% at 115 °C in the CO preferential oxidation in excess of hydrogen (CO-PROX) and maintaining this activity even after 48 h of time on stream. The incorporation of CO2 and H2O in the feed stream (simulating a PROX unit) caused a decrease in the CO conversion, except for the catalyst synthesised using PMMA microspheres as a template which maintained a CO conversion of 95% at 115 °C. This catalyst exhibits an excellent catalytic performance, also under real operating conditions, thanks to many and concomitant factors, such as the very small CeO2 particle size (5.6 nm), the surface being rich in copper (atomic ratio Cu/Ce = 0.35) that is easily reducible, and the peculiar morphology and porosity of the material.