| Popis: |
We have studied the effect of different supports (CeO2, ZrO2, SiC, SiO2 and Al2O3) on the catalytic performance and phase stability of Co3O4 nanoparticles during the preferential oxidation of CO (CO-PrOx) under different H2-rich gas environments and temperatures. Our results show that Co3O4/ZrO2 has superior CO oxidation activity, but transforms to Co0 and consequently forms CH4 at relatively low temperatures. The least reduced and least methanation active catalyst (Co3O4/Al2O3) also exhibits the lowest CO oxidation activity. Co-feeding H2O and CO2 suppresses CO oxidation over Co3O4/ZrO2 and Co3O4/SiC, but also suppresses Co0 and CH4 formation. In conclusion, weak nanoparticle-support interactions (as in Co3O4/ZrO2) favour high CO oxidation activity possibly via the Mars-van Krevelen mechanism. However, stronger interactions (as in Co3O4/Al2O3) help minimise Co0 and CH4 formation. Therefore, this work reveals the bi-functional role required of supports used in CO-PrOx, i.e., to enhance catalytic performance and improve the phase stability of Co3O4. |
