Nano-structured gold catalysts supported on CeO2 and CeO2-Al2O3 for NOx reduction by CO:: Effect of catalyst pretreatment and feed composition

Gold catalysts supported on ceria and ceria-alumina were studied in NOx reduction by CO. Gold was loaded using deposition-precipitation method. The ceria-alumina (20 wt% alumina) support was synthesized by co-precipitation. The average size of gold and ceria nano-particles was bellow 10 nm. It was established that the type of pretreatment do not have a substantial effect on the catalytic activity. The presence of O-2 in the feed leads to a high conversion of CO to CO2 but no NO conversion was registered. Both NO and CO conversion was increased adding H-2 to the feed. The catalytic activity became higher upon adding higher amount of H-2. Supplementary to the main reaction parallel reactions took place. Bellow 200 degrees C N2O formation and at 250 degrees C and above the NH3 formation was detected. At around 200 degrees C it was established 100% selectivity to N-2. The addition of water to the feed influenced positively the CO conversion and did not influence negatively the conversion of NO. The selectivity to N-2 at around 200 degrees C remained 100% independent of the presence of moisture. Alumina in the mixed support prevents the sintering of both gold and ceria nano-particles. The results obtained make the catalysts containing gold supported on ceria-alumina promising for practical application.