Designing CuO–SiO2 and Cu0–SiO2 Monolithic Ceramics Bearing Hierarchical Porosity Toward Robust and Cycling CO Oxidation Properties

In the general context of environmental air remediation, copper-oxide-based self-standing porous catalysts (MUB-103­(x)) and their reduced homologues (Red MUB-103­(x)) have been synthesized and studied for the thermoconversion of CO to CO2. Catalytic experiments under dry air conditions reveal that for nonreduced catalysts, increasing the Cu content diminishes the light-off temperature T 50 (corresponding to 50% conversion). The catalytic performances exhibited by the CuO phase dispersed in the silica pores of MUB-103­(x) samples are the highest reached to date despite the limitations of the experimental conditions used. After reduction with H2, the native Red MUB-103­(x) catalysts offer CO conversion efficiencies significantly more increased, leading to a lowering of the T 50 values equal to at least 100°C. As such, the CO conversion reaches a T 50 value of 160 °C for Red MUB-103(2) with 1.81 wt % Cu; this catalyst displays a specific rate of 8.6 mmolCO gCu –1 s–1 at 175 °C, largely higher than those observed to date. The performances of the Red MUB-103(2) sample were evaluated for CO oxidation under humid conditions with the addition of 5 vol % water vapor in the feed during four cycles, leading to the same efficiency when compared with that under dry experimental conditions, revealing robustness. A drastic increase in the CO conversion temperature was observed for the 4th cycle, i.e., after 8 h under humid conditions. Analyses of the spent Red MUB-103(2) catalyst after four cycles reveal a slight oxidation of copper, leading to Cu2O species. Importantly, after four cycles, the deactivated catalyst was able to partially recover its performance when reactivated through a 2 h reducing treatment under H2 at 400 °C.