The water resistance mechanism of (CoO)₇.₅·(CuO)₃·(TiO₂)6.3 catalyst in propylene combustion

Abstract

The design of water-resistant oxide catalysts is of significant importance in chemical processes. In this work, (CoO)m·(CuO)n·(TiO₂)h (m=0-9mmol, n=0-12mmol, h=0-20mmol) catalysts were prepared and applied to propylene combustion. Due to the synergistic effect of copper, cobalt, and titanium, (CoO)7.5·(CuO)3·(TiO₂)6.3 could maintain the 90% propylene conversion rate for up to 500 hours under 4.2 vol% moisture, whereas (CoO)7.5·(CuO)3 only survived for 47 hours. The abundant oxygen vacancies and excellent redox properties of (CoO)7.5·(CuO)3·(TiO₂)6.3, as revealed by O2-TPD, EPR, and H2-TPR analysis would explain its superior catalytic performance. C3H6-TPD results showed that (CoO)7.5·(CuO)3·(TiO₂)6.3 had a stronger adsorption capacity for propylene. H2O-TPD indicated weaker adsorption for water and In situ infrared results showed that water molecules were more difficult to adsorb on the surface of (CoO)7.5·(CuO)3·(TiO₂)6.3 compared to (CoO)7.5·(CuO)3, confirming the mechanism of water resistance. DFT calculations demonstrated weaker competitive adsorption between propylene and water in (CoO)7.5·(CuO)3·(TiO₂)6.3, and its higher hydrolysis dissociation energy suggested better hydrothermal stability compared to (CoO)7.5·(CuO)3, further providing theoretical support for the water resistance mechanism. This work will inspire the rational design of water-resistant catalysts.