# Exploring CeO\({}_{2}\)-Doped Co/SBA-15 Catalysts for Acetic Acid Oxidative Steam Reforming
## 3 Results and Discussion
### Oxidative Steam Reforming of Acetic Acid  
The effect of the CeO\({}_{2}\) content on the catalytic activity of Co/xCeO\({}_{2}\)-SBA-15 catalysts in AAOSR was evaluated in the range of 400 to 700 \({}^{\circ}\)C. In this regard, Figure 6a,b display the results of catalytic activity concerning H\({}_{2}\) yield and acetic acid conversion as a function of the reaction temperature, respectively. As predicted, given the endothermic characteristics of the reforming reactions, an increase in the reaction temperature led to an improvement in the catalytic activity for all the catalysts [53]. Concerning the H\({}_{2}\) yield, low values were achieved at temperatures below 500 \({}^{\circ}\)C. However, increasing the reaction temperature from 500 \({}^{\circ}\)C to 550 \({}^{\circ}\)C significantly enhanced the H\({}_{2}\) yield, with values around 30% higher reached for the catalysts supported over modified CeO\({}_{2}\)-SBA-15. Beyond this temperature, ceria-containing samples considerably increased the H\({}_{2}\) yield as compared to Co/SBA-15, reaching H\({}_{2}\) yields up to 70-75% in all cases, near thermodynamic equilibrium values. Therefore, the effect of Ce content was less remarkable with further temperature rises. To analyze the efficacy of the incorporation of CeO\({}_{2}\) into the Co/SBA-15 catalysts, concerning acetic acid conversion, it is required to focus on temperatures below 550 \({}^{\circ}\)C. Over this range, the Co/5 CeO\({}_{2}\)-SBA-15 catalyst achieved approximately 5% greater acetic acid conversion than Co/SBA-15. Similarly, the acetic acid conversion increased by almost 20% for Ce contents over 10 wt.% in the catalyst formulation. Likewise, acetic acid conversion increased by over 40% when increasing the temperature from 500 to 550 \({}^{\circ}\)C, reaching almost complete acetic acid conversions for catalysts Co/10 CeO\({}_{2}\)-SBA-15 and Co/20 CeO\({}_{2}\)-SBA-15. At temperatures above 600 \({}^{\circ}\)C, almost complete conversion was reached for all catalysts. These findings align with those mentioned by [PERSON] et al. [26], who stated that cerium's incorporation onto Co/SBA-15 catalysts for CO oxidation activated the oxygen in the surface lattice of SBA-15 (Ce\({}^{3+/4+}\)-O-Si) and generated oxygen vacancies. In this way, the  
Figure 6: Effect of the CeO\({}_{2}\) addition on the H\({}_{2}\) yield (**a**) and the acetic acid conversion (**b**) at different temperatures (400–700 \({}^{\circ}\)C). Reaction conditions: S/C molar ratio = 2, O\({}_{2}\)/C molar ratio = 0.0375, WHSV = 30.2 h\({}^{-1}\), P = 1 atm. behavior of CeO\({}_{2}\)-based materials has been related to ceria redox properties, which can release, capture, and store oxygen according to the following redox reaction:  
\[\text{CeO}_{2}\leftrightarrow\text{CeO}_{2-\text{x}}+\text{O}_{\text{x}} \tag{15}\]  
where O\({}_{\text{x}}\) is the lattice oxygen at the CeO\({}_{2}\) surface [51]. This fact can promote the activity performance toward reactions such as the WGS (Equation (3)), which may increase the hydrogen yield [34]. Moreover, this lattice oxygen could induce a decrease in carbon deposition, promoting coke gasification [16; 51]. During the AAOSR tests, the Co/10 CeO\({}_{2}\)-SBA-15 and Co/20 CeO\({}_{2}\)-SBA-15 samples showed similar H\({}_{2}\) yield and acetic acid conversion values. In contrast, the Co/30 CeO\({}_{2}\)-SBA-15 catalyst showed a slightly lower catalytic performance than the latter ones. The catalytic activity observed in the Co/30 CeO\({}_{2}\)-SBA-15 catalyst can be attributed to its textural properties, and lower oxygen vacancy. The Co/30 CeO\({}_{2}\)-SBA-15 catalyst exhibits the smallest BET surface area (240 m\({}^{2}\)/g) and pore volume (0.50 cm\({}^{3}\)/g), thus indicating a partial blockage of the mesoporous structure, which may hinder the diffusion of reactants and products and limit the accessibility to active sites in comparison with Co/10 CeO\({}_{2}\)-SBA-15 and Co/20 CeO\({}_{2}\)-SBA-15.