Effect of calcination temperatures and precipitant on the catalytic performance of Au/ZnO catalysts for CO oxidation at ambient temperature and in humid circumstances

摘要

Various Au/ZnO catalysts have been prepared by a coprecipitation method and have been for CO oxidation at ambient temperature and in the presence of water in the feed stream. It was found that Au/ZnO catalysts exhibited excellent CO oxidation activity and stability, and the catalytic performance was greatly dependent on the calcination temperatures and on the kind of precipitants. The most stable catalyst was obtained using Na_2CO_3 as precipitant and calcining at 240 deg C; it can completely oxidize CO to CO_2 for more than 1700h under the following conditions: 0.5% CO, 10% O_2, 1.8% H_2O, balanced with Ar, GHSV = 12,000h~(-1). The XRD, BET, TEM and TG-DTA investigations of the catalysts revealed that the particle size of Au and ZnO, the S_(BET) and the type of zinc species were the primary factors influencing the stability of Au/ZnO catalysts. Furthermore, sintering of metallic gold and the accumulation of carbonate-like species during CO oxidation were observed; these processes may be responsible for the deactivation of the Au/ZnO catalysts.