The preferential CO oxidation was performed in a fixed-bed flow reactor at atmospheric pressure. 0.2 g catalyst (20–40 mesh) was filled in a quartz tube reactor (6 mm outside diameter). The reacting stream consisted of 1% CO (by volume hereinafter), O2 with varying O2:CO molar ratio (k = 1–4), 10% H2O (when used), 10% CO2 (when used) and balanced H2. The parameter k is defined as the amount of oxygen present divided by the amount of oxygen
needed to completely oxidize all of the CO in the feed gas (k = 2[O2]/[CO]), where k = 1 is sufficient to provide for the complete oxidation of CO to CO2 in the absence of an oxygen consuming side reaction. The total flow rate was 30 ml min1, which was controlled by an independent thermal mass flow controller.On-line gas chromatograph (GC 7890II) with a TCD detector was employed to measure the reactor inlet and outlet effluent gas streams. TDX-01 column (2 m 4 mm) was used to separate oxygen, carbon monoxide and carbon dioxide. In this paper, the CO conversion was calculated from the change of the CO concentration