An efficient Sn-modified Pd-Cu/Al2O3 catalyst for H2 purification through preferential oxidation of CO at low temperature

A series of Pd-Cu-xSn/Al2O3 catalysts with the low tin content (Sn/Cu atomic ratio = 0.1, 0.25, 0.5) is obtained by the facile impregnation routes and employed for low-temperature CO preferential oxidation (CO-PROX) in H2-rich stream. The catalytic performance tests show that the suitable addition of Sn possesses the positive effects on Pd-Cu/Al2O3 for CO-PROX, that is, PC-0.25Sn-Al (Sn/Cu atomic ratio = 0.25) exhibits better catalytic activity and stability at 30 °C. The systematic characterization results demonstrate the moderate incorporation of SnCl4 to Pd-Cu/Al2O3 drives the generation of SnO2, which promotes the strong interaction between Sn species and Pd-Cu/Al2O3. And it is conductive to improving the structure stability of active Cu2Cl(OH)3 species and the better water resistance of PC-0.25Sn-Al. Furthermore, the doping of Sn in PC-0.25Sn-Al may retard the reduction of active Pd species, promoting the absorption/activation and oxidation of CO on active Pd species. Meanwhile, the appropriate amount of Sn in PC-0.25Sn-Al readily provides more electron-rich active Cu+ species in the reaction stream, which is favorable to the reoxidation of Cu+ species by O2/active oxygen to Cu2+ species. These will favour the durative catalytic recycle of Pd and Cu species in PC-0.25Sn-Al and the enhancement of its catalytic activity and stability.