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 MUB103(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 H-2, the native Red MUB103(x) catalysts offer CO conversion efficiencies significantly more increased, leading to a lowering of the T(50 )values equal to at least 100?. As such, the CO conversion reaches a T-50 value of 160 ? 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 ?, largely higher than those observed to date. The performances of the Red MUB103(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 ?.

Automated summary

Copper-oxide-based self-standing porous catalysts show high efficiency in the thermoconversion of CO under dry air conditions, and their efficiency further increases after reduction treatment, demonstrating robustness.