## 3 Results
### CO Oxidation Performance of the Catalysts  
Oxygen concentration and temperature were varied in the range of 0.5-2.5 vol.% and 50-250 \({}^{\circ}\)C, respectively, in a series of CO oxidation experiments. The inlet concentration of CO was fixed at 2000 ppm. The conversion of CO into CO\({}_{2}\) obtained with as received \(\gamma\)-Al\({}_{2}\)O\({}_{3}\) (ALVIR) under steady state conditions showed a maximum of 5.6% at reactor temperature of 175 \({}^{\circ}\)C. The CO conversion percentages using the RAWOS and RAWS catalyst materials are shown in Figure 6a-c for oxygen \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Catalyst Name** & **Process** & **Surface Area (m\({}^{2}\)/g)** & **Pore Volume (cc/g)** & **Pore Radius (Mode Dv(r)) (Å)** \\ \hline \multirow{2}{*}{ALVIR} & Adsorption & 102.9 & 0.2322 & 30.72 \\ \cline{2-5}  & Desorption & 140.7 & 0.2480 & 28.18 \\ \hline \multirow{2}{*}{RAWOS} & Adsorption & 120.5 & 0.2475 & 30.58 \\ \cline{2-5}  & Desorption & 168.7 & 0.2694 & 24.40 \\ \hline \multirow{2}{*}{RAWS} & Adsorption & 119.0 & 0.2532 & 30.76 \\ \cline{2-5}  & Desorption & 164.8 & 0.2723 & 24.54 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Physisorption results of the catalysts measured by Barrett-Joyner-Halenda (BJH) method. Figure 5: Nitrogen adsorption-desorption isotherms (**a**)–(**c**) and the multipoint BET plots; (**d**)–(**f**) corresponding to ALVIR, RAWOS and RAWS catalysts. concentrations of 0.5. 1.5 and 2.5 vol.%. The plots clearly demonstrate a gradual increase in CO conversion from \(<\)10% at 50 \({}^{\circ}\)C to 100% at 200 \({}^{\circ}\)C. Generally, varying the oxygen content at low temperature did not affect the overall conversion process significantly but its influence at high temperature is clear. The RAWOS catalyst exhibits substantial activity above 100 \({}^{\circ}\)C. Similar behavior was observed on repeating the oxidation experiments with the PEG-stabilized RAWS catalyst, but the CO conversion percentage at each experimental temperature was notably higher. Moreover, total conversion was achieved at 175 \({}^{\circ}\)C as compared to 200 \({}^{\circ}\)C observed for the equivalent RAWOS catalyst. At low temperature (50 \({}^{\circ}\)C and 75 \({}^{\circ}\)C), the difference between the materials is almost negligible but when the temperature is increased, a remarkable difference can be noted. An increase in the CO conversion efficiency of about 33% by RAWS catalyst was observed in experiments at 125 \({}^{\circ}\)C with an O\({}_{2}\) concentration of 1.5%. Above and below this temperature, a gradual decrease in the conversion efficiency can be noted with a slight variation depending on the oxygen concentration. The stability of the catalysts was also confirmed by conducting the experiments continuously for 7 h at 125 \({}^{\circ}\)C. These extended experiments showed the repeatability of the performance observed above without any significant change. In order to investigate the performance of the catalysts under real working conditions, water vapor was added to the reactant gas (_i.e._, CO + H\(\mathrm{O}\) + O\(\mathrm{{}_{2}}\)). The experiments were thus performed in the presence of 2.5% and 5% water (by volume) at different temperature. The results of these CO oxidation experiments are represented in Figure 7. The CO conversion efficiency increased depending upon the temperature. For a water content of 2.5%, full conversion was achieved at 275 \({}^{\circ}\)C for the RAWOS catalyst. By contrast, the rod type RAWS catalysts exhibited 100% CO oxidation at a reduced temperature of 225 \({}^{\circ}\)C (Figure 7a). Increasing the water content from 2.5% to 5% resulted in the shift of temperature to 300 \({}^{\circ}\)C for the RAWOS material and 250 \({}^{\circ}\)C for the RAWS catalyst, respectively (Figure 7b). In addition, it is very clear that at every reaction temperature, the RAWS catalyst showed an improved conversion performance over the RAWOS equivalent.