# Exploring CeO\({}_{2}\)-Doped Co/SBA-15 Catalysts for Acetic Acid Oxidative Steam Reforming
## 1 Introduction  
Traditional fuels have been the starting point of industrial and energy development worldwide. However, burning fossil fuels significantly contributes to the release of greenhouse gases, driving climate change. CO\({}_{2}\) emissions and other pollutants increase global temperatures, leading to extreme climate, melting glaciers, and rising sea levels [1, 2]. Given this alarming reality, it is imperative to implement robust environmental policies to lessen emissions and promote the transition in the direction of more sustainable sources of energy. To address these challenges, the established aim is to limit the global temperature increase to 1.5 \({}^{\circ}\)C until the end of the century [3, 4, 5]. Consequently, governments have implemented environmental policies that promote the utilization of renewable energies, the development of energy efficiency, and the integration of clean technologies [6]. In these circumstances, hydrogen has risen as a promising alternative, considering its high energetic potential and environmental advantages [7]. Hydrogen production from renewable resources, such as biomass, will be a sustainable alternative for managing organic waste and reducing the dependency on fossil fuels, playing a potentially key role in the industrial and transport sectors' decarbonization [7, 8]. Thermochemical processes, such as pyrolysis, use biomass to generate valuable products such as syngas, bio-char, and bio-oil. The pyrolysis bio-oil could be composed of organic as well as aqueous phases [8; 9; 10]. The organic phase consists of high-energy compounds, which could be further enhanced through hydrotreating to produce biofuels. However, the aqueous phase has a lower energy potential than the organic phase, given that it consists mainly of water and several oxygenated compounds with low and high molecular weight [8]. Despite having a lower energy value, the bio-oil aqueous phase could be revalorized via catalytic steam reforming, producing hydrogen [9; 10; 11; 12; 13]. Given the heterogeneity of the bio-oil aqueous phase composition, many authors focus their investigation on representative compounds, such as acetic acid, since it represents approximately 20 wt.% of these organic compounds [14; 15; 16; 17]. In acetic acid steam reforming, steam reacts with this organic compound at high temperatures to produce hydrogen, as represented in Equation (1). This process is highly endothermic, requiring high energy consumption to maintain the high temperatures required. \[\mathrm{C_{2}H_{4}O_{2}+2H_{2}O\leftrightarrow 4\;H_{2}+2 CO_{2}} \tag{1}\]  
In this scenario, some authors have reported that the inclusion of oxygen in the feed stream leads to oxidative steam reforming [18; 19]. The primary advantage of this configuration is that exothermic oxidation reactions provide part of the energy requirements to drive forward the endothermic steam reforming reactions. An oxidizing environment would also reduce the coke deposited on the catalyst by its combustion. However, hydrogen generation will be slightly reduced, as shown in Equation (2). \[\mathrm{C_{2}H_{4}O_{2}+\left(\frac{n}{2}\right)O_{2}+\left(2-n\right)\;H_{2}O \leftrightarrow\left(4-n\right)\;H_{2}+2 CO_{2}} \tag{2}\]  
Apart from the main reaction, secondary reactions can occur, such as a water-gas shift (Equation (3)), the thermal decomposition of acetic acid (Equation (4)), ketonization (Equation (5)), acetone steam reforming (Equation (6)), methane steam reforming (Equation (7)), coke formation (Equations (8) and (9)), and the Boudouard reaction (Equation (10)) [20].