# Nanosized Ni/SBA-15 Catalysts for CO\({}_{2}\) Reforming of CH\({}_{4}\)
## 1 Introduction  
Hydrogen is produced mostly by steam reforming of methane [1; 2; 3]. CO\({}_{2}\) reforming of methane can reduce the emissions of CO\({}_{2}\) and CH\({}_{4}\), the main greenhouse gases [1; 4; 5; 6]. Methane reforming is an interesting method for converting biogas (methane and carbon dioxide) to a mixture of CO and H\({}_{2}\) that is recognized as a synthesis gas (syngas) [1; 2; 3; 7; 8; 9; 10]. CO\({}_{2}\) reforming of methane produces equal amounts of carbon monoxide and hydrogen which can be converted into a variety of chemicals and fuels, such as methanol and liquid fuel, via the Fischer-Tropsch process [10; 11; 12]. However, CO\({}_{2}\) reforming of methane is an endothermic reaction; it requires high temperature levels as indicated by the following reaction [13; 14; 15]:  
\[CH_{4(gas)}+CO_{2(gas)}\leftrightarrow 2 CO_{(gas)}+2H_{2(gas)}\Delta H_{298}=261 \mathrm{kJ}\;\mathrm{mol}^{-1}. \tag{1}\]A catalyst is essential for converting the highly stable methane molecules into synthetic gas, and then into liquid fuels [4; 16; 17]. Due to the high reaction temperatures, the catalyst may suffer from deactivation due to sintering, and may also be deactivated by carbon deposition [5; 9; 13; 18]. Supported nickel and noble metal catalysts have been used successfully in research for catalyzing CO\({}_{2}\) reforming of methane [1; 6; 9; 13]. Although nickel catalysts are sensitive to coke formation and are less active, nickel is more economical and widely available [15; 19]. Adding Co to Ni improves dispersion and catalytic enactment due to the synergetic effect of Ni and Co [10; 13]. Developing stable nickel catalysts with higher resistance to coke formation and sintering is the key to commercializing the process [20; 21; 22]. The stability and performance of nickel catalysts can be improved by alloying them with another active metal. The support critically affects the catalyst stability and activity. Different factors should be considered when selecting a support material. The support surface area is considered a dominant factor [15; 18; 23; 24]. A higher surface area provides better dispersion for the metallic active sites, thereby reducing the sintering effect. Other factors should be considered in the selection of a support, including larger pores, thermal stability, chemical composition, and wall thickness [15; 25]. The support can be modified by doping other metal oxides that can provide oxygen for the formation of CO, which reduces the carbon deposition [26; 27]. Oxides with higher oxygen capacity and mobility, such as CeO\({}_{2}\), are preferred catalyst promoters for CO\({}_{2}\) reforming of methane [24]. SBA-15, referred to also as S15, is a mesoporous support distinguished by its thick walls and a narrow, well-ordered, two-dimensional hexagonal pore network that is stable even after reaction [12; 23]. The active sites are distributed within the high-surface-area pores of S15, leading to improved catalyst dispersion. Good interface between active sites and support should ensure reduced active site mobility and sintering which, in turn, decrease the extent of carbon deposition and catalyst deactivation [19; 27; 28; 29]. In addition, better dispersion should reduce the extent of carbon deposition, which is the main barrier to developing a stable catalyst in the CO\({}_{2}\) reforming of methane [6; 15; 19; 30; 31]. [PERSON] et al. [6] doped Ni/S15 with ceria and zirconia modifiers, resulting in a remarkable improvement in the stability of the doped catalysts. The authors reported better conversion with Ni/S15, which is credited to the availability of more nickel active sites for catalyzing the reaction. [PERSON] et al. [15] used a bimetallic catalyst (Co-Ni) supported on S15 for the CO\({}_{2}\) reforming of methane. They compared the performance of Co-Ni/S15 with that of Co-Ni/S15 doped with Mg, La, and Sc. The results indicated that Mg and Sc are excellent support dopants. Adding Mg and Sc increased the CH\({}_{4}\) conversion achieved using Co-Ni/S15 by 28% and 26%, respectively.