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

Abstract

CuO-CeO 2 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, N 2 adsorption-desorption at −196 • C, H 2 thermoprogrammed reduction (H 2 -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 CO 2 and H 2 O 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 CeO 2 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.

Influence of the Incorporation of Basic or Amphoteric Oxides on the Performance of Cu-Based Catalysts Supported on Sepiolite in Furfural Hydrogenation

“…However, 1CuMgOSep was more resistant to the increase in temperature, achieving a conversion of 80% under similar experimental conditions ( Figure 1A). These catalytic behaviors are in agreement with those shown in the literature, since several authors have predicted a volcano profile when the reaction temperature is increased, due to desorption of FUR molecules from active sites at higher reaction temperature before the hydrogenation process [35,39].…”

Ru–Pd Bimetallic Catalysts Supported on CeO2-MnOX Oxides as Efficient Systems for H2 Purification through CO Preferential Oxidation

“…In particular, the Ru/CeO 2 -MnO x catalyst appears the most suitable for PEM fuel cells (operating temperature range of 80-120 • C) while the Ru-Pd/CeO 2 -MnO x system can be considered best for the AFC fuel cells (operating temperature range of 100-140 • C). It is interesting to note that the catalytic performances of these catalysts were comparable or even better, in terms especially of CO 2 selectivity, with respect to ceria and ceria-manganese oxide-based catalysts reported in the literature for CO-PROX (see Table 2) [12,[78][79][80][81][82], even though it must stressed that a realistic comparison is very difficult due to the different operative conditions of the various works. As displayed in Figure 7, the Ru/CeO 2 -MnO x and Ru-Pd/CeO 2 -MnO x catalysts were quite stable after 14 h of streaming both at 100 • C and 120 • C, whereas the monometallic Pd sample began to deactivate at 120 • C after 8 h. The higher selectivity to CO 2 found on the Ru-Pd system, which reduces the undesired H 2 consumption, represents a promising result of this research, being one of the key aims of the design of CO-PROX catalysts.…”

Catalytic Behaviour of Flame-Made CuO-CeO2 Nanocatalysts in Efficient CO Oxidation

“…Shang et al [13] founded that the impregnation method offered more highly dispersed CuO and stronger synergistic interaction between CuO and CeO 2 to promote the reduction of CuO to Cu + species at the Cu-Ce interface, resulting in the highest catalytic activity, whereas the catalyst prepared by the co-precipitation method suppressed the formation of the Cu-Ce interface, where the adsorbed CO would react with active lattice oxygen to form CO 2 to exhibit a lower catalytic performance. Besides, the water resistive property of CuO-CeO 2 catalytic systems is also affected by preparation methods [14]. Flame spray pyrolysis (FSP) is a comparatively simple, one-step synthesis for mixed metal oxides [15].…”