# Nanosized Ni/SBA-15 Catalysts for CO\({}_{2}\) Reforming of CH\({}_{4}\)
## 3 Results and Discussion
The catalyst doped with CeO\({}_{2}\) showed better activity than the catalyst doped with ZnO, as CeO\({}_{2}\) has a greater oxygen capacity and mobility than ZnO, which improves the activity and carbon capacity [36]. Higher oxygen mobility facilitates CO\({}_{2}\) conversion and reduces the extent of carbon formation on the catalyst. As shown in Figure 2, Co-Ni/Zn-S15 has a high concentration of acidic sites, which reduces CO\({}_{2}\) adsorption on the catalyst surface, leading to lower reaction rates [7; 36; 37]. In addition, the low adsorption of CO\({}_{2}\) on Co-Ni/Zn-S15 may affect CO\({}_{2}\) reforming of the methane reaction, leading to different side reactions owing to the unbalanced availability of CH\({}_{4}\) and CO\({}_{2}\) on the catalyst surface, as presented in Figure 6. The lower H\({}_{2}\)/CO ratio for Co-Ni/Zn-S15 and Co/S15 indicates lower catalyst selectivity, as displayed in Figure 6. However, the low activity of Co/S15 can be attributed to the Co oxidation state. The TPR data showed that reduction of Co in Co/S15 started after 800 \({}^{\circ}\)C, whereas the employed reduction temperature was 500 \({}^{\circ}\)C.  
To provide extra details about the characteristics of the fresh S15 and loaded fresh Ni/S15 catalysts, TEM images were acquired, as displayed in Figure 7. It is clear that S15 had a well-ordered mesoporous  
Figure 1:0 The molar H\({}_{2}\)/CO ratio of the product stream. structure of S15 supports (long-parallel channels in hexagonal array), as shown in Figure 7a,b. Higher magnification showed that the metal catalyst nanoparticles were homogeneously distributed on S15 with a fine particle size of around 6-10 nm, as shown in Figure 7b. After using the catalyst, the metal nanoparticles maintained their particle size (6-10 nm) with the appearance of larger carbon nanoparticles (20 nm), as shown in Figure 7c,d. Figure 6 presents the molar H\({}_{2}\)/CO ratio of the product stream for each catalyst. Thus, it is postulated that the side reaction pathways led to the same reaction products, since no other reaction products have been detected. CeO\({}_{2}\) addition should confer strong basic sites, leading to enhanced CO\({}_{2}\) adsorption and improved carbon gasification. ZnO supported over S15 has shown remarkable catalytic activity in the cyclic addition of CO\({}_{2}\) to hydrocarbons [37]. Thus, it is expected that Zn-doping should support carbon/hydrocarbon deposition. To investigate the amount of carbon formed over each catalyst, the deposited carbon was subjected to a temperature-programmed oxidation (TPO) test, using air, in TGA. The weight loss against the temperature is displayed in Figure 8 for the Co-Ni/S15 and Co/S15 catalysts, and an analogous trend was seen for the other catalysts. When the temperature was raised to 1000 \({}^{\circ}\)C, almost no weight loss was detected for the catalysts under study. The small weight changes illustrated in Figure 8 are attributed to noise in the TGA instrument. Figure 8 shows that no carbon was deposited over the catalyst samples. Carbon deposition is considered to be the main cause for catalyst deactivation. As shown in Figures 4-6, all catalysts exhibited stable performance throughout the 8 h test. The stable performance is assigned to the high catalytic surface area, ensuring better catalyst distribution and a lower thermal aging rate. In addition, the detection of almost no carbon deposition indicates that carbon fouling does not influence the catalyst performance. Figure 8 indicates that the prepared catalysts show excellent resistance to carbon deposition and a higher selectivity for CO\({}_{2}\) reforming of methane. Thus, such catalysts, especially Ni/S15, are potentially applicable in the commercial CO\({}_{2}\) reforming of methane. Figure 1:1 TEM image of fresh S15 and used Ni/S15 catalyst ((**a,b**) for fresh S15, (**c,d**) for loaded Ni/S15 catalyst).