Mesoporous ceria-zirconia supported cobalt oxide catalysts for CO preferential oxidation reaction in excess H2
Mesoporous Co3O4/CexZr1−xO2 (x = 0.75, 0.85, 0.95, 1) catalysts were synthesized by surfactant-assisted co-precipitation with subsequent incipient wetness impregnation (SACP-IWI) method. The prepared mesoporous ceria-zirconia supported cobalt oxide catalysts were used to catalyze CO preferential oxidation (PROX) reaction to eliminate the trace CO from H2-rich gases. The effects of structure-directing agent (SDA) type, atomic ratio of Ce/(Ce + Zr), cobalt oxide loading and reaction parameters on the catalytic properties for CO PROX reaction in excess H2 were investigated. Moreover, the various characterization techniques like N2 adsorption/desorption, X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR), NH3 temperature-programmed desorption (NH3-TPD), Fourier-Transform infrared spectroscopy (FT-IR) were employed to study the relationship between catalyst nature and catalytic properties. The results of N2 adsorption/desorption and X-ray diffraction patterns indicate that catalysts prepared by using cationic surfactant cetyltrimethylammonium bromide (CTAB) as SDA possess an ordered mesoporous architecture and exhibit much better catalytic activity compared with those prepared by using anionic surfactant ammonium dodecylbenzenesulfonate (ADBS) as SDA. The residual sulfur from ADBS was demonstrated to be the main reason for the much worse catalytic performance by the characterization results of FT-IR and NH3-TPD. Results show that the developed Co3O4/meso-Ce0.85Zr0.15O2 catalysts by SACP-IWI method with CTAB as SDA show an outstanding catalytic performance for CO PROX reaction, which mainly depends on the redox behavior of catalyst and cobalt oxide dispersion affected by the ceria-zirconia support feature, atomic ratio of Ce/(Ce + Zr) of support and cobalt oxide loading.
Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Mesoporous ceria-zirconia is an appropriate support to stabilize high-valence Co3+. ► The high-valence cobalt is the main active species for CO PROX in excess H2. ► Residual sulfur from ADBS significantly affects catalytic properties for CO PROX. ► It is a robust and effective catalyst for CO PROX even with CO2 and H2O in the feed. ► Catalytic properties highly depend on the dispersion of Co3O4 and redox of catalyst.
Journal: Applied Catalysis B: Environmental - Volume 110, 2 November 2011, Pages 154–163