The water resistance mechanism of the (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 = 0–9 mmol, n = 0–12 mmol, and h = 0–20 mmol) catalysts were prepared and applied to propylene combustion. (CoO)_7.5·(CuO)₃·(TiO₂)_6.3 could maintain a 90% propylene conversion rate for up to 500 hours under 4.2 vol% moisture, whereas (CoO)_7.5·(CuO)₃ remained active for only 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 analyses, 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 of 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.