Low-temperature CO preferential oxidation in H2-rich stream over Indium modified Pd-Cu/Al2O3 catalyst

The impact of Indium (In) doping upon the catalytic performance of Pd-Cu/Al 2 O 3 for carbon monoxide preferential oxidation (CO-PROX) in hydrogen (H 2 ) rich atmosphere at low temperature has been studied. A series of catalysts with extremely low palladium (Pd) loading (0.06 wt%) are synthesized by the facile co-impregnation method. When the In/copper (Cu) atomic ratio equals 0.25, Pd-Cu-In 0.25 /Al 2 O 3 can keep 40% CO conversion and 100% carbon dioxide (CO 2 ) selectivity at least 120 min at 30 °C, which is significantly superior to the catalytic performance of Pd-Cu/Al 2 O 3 . The elaborate characterization findings reveal that the added In species to Pd-Cu/Al 2 O 3 causes Indium oxide (In 2 O 3 ) to generate, which produces the interaction of In 2 O 3 with Pd-Cu/Al 2 O 3 , further promoting the dispersion of copper chloride hydroxide (Cu 2 Cl(OH) 3 ). Moreover, the modification of In facilitates the re-oxidation of Pd 0 to Pd + through reducing the formation of palladium hydride (PdH x ) during the CO-PROX reaction. Meanwhile, the addition of In leads to the decrease of Cu + electron cloud density, making it easier to be oxidized to Cu 2+ . Collectively, the easy re-oxidation of Pd 0 and Cu + is favorable to fulfill the Wacker cycle between Pd and Cu species, thus improving the catalytic performance for CO-PROX.