## 3 Results and Discussion
### Catalytic Performance  
Since CSMR is an endothermic reaction, the conversion of CH\({}_{4}\) increases with an increase in the reaction temperature. According to Figure S7, the CH\({}_{4}\) conversion was gradually growing with the increasing temperature (from 600 \({}^{\circ}\)C to 850 \({}^{\circ}\)C). This is consistent with the literature data [59; 60; 61] and indicates that the concentration of Ni\({}^{0}\) active centers in the CSMR reaction increases with an increasing temperature. The conversion of CH\({}_{4}\), CO\({}_{2}\), and the yields of H\({}_{2}\) and CO increased with the increasing temperature of the reaction. The H\({}_{2}\)/CO ratio was less than the calculated one (1.64 at a given value of CO\({}_{2}\) + H\({}_{2}\)O/CH\({}_{4}\)). We can explain this fact by the water gas conversion reaction; as a result, H\({}_{2}\) was consumed, and CO was formed (Figure S8). Moreover, the decrease in the H\({}_{2}\)/CO ratio at higher temperatures may be owing to a preferable course of DRM. As shown in Table 5, the indicators of the CSMR reaction at 750 \({}^{\circ}\)C depended on the method of preparing the catalysts. For the Ni/CeMg samples, the hydrogen yield increased in the series of the support precursor C \(<\) A, and for samples from series A, in the series A-P-O \(<\) A-S-O-A-S-V, which was not similar to the dispersion row of the reduced catalysts A-S-P \(<\) A-S-O \(<\) A-S-V (Table 3). The initial activity of the A-S-O and A-S-V catalysts was very close. Therefore, we can conclude that the size effect (d) estimated by XRD on the initial catalytic activity was weak. It was shown in [62; 63] that coordinative unsaturated surface atoms, which predominate in small crystallites (d \(<\) 10 nm), are much more active in methane reforming reactions than atoms in planes with low crystallographic indices in large crystallites. When d is greater than 12 nm, the fraction of active Ni\({}^{0}\) species will not significantly change. Figure 5: O1s X-ray photoelectron spectra of the catalysts reduced at 800 \({}^{\circ}\)C. 1—Ni/CeMg-C-S-O; 2—Ni/CeMg-A-S-O; 3—Ni/CeMg-A-S-V-500; 4—Ni-Pd/CeMg-A-S-V, 5—Ni/CeMg-A-P-O. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \multicolumn{1}{c}{\multirow{2}{*}{**Sample**}} & \multicolumn{6}{c}{**TA Data after**} \\  & \multicolumn{6}{c}{**Indictors of the Reaction at 750 \({}^{\circ}\)C**} & \multicolumn{6}{c}{**XRD Data**} & \multicolumn{6}{c}{**Reaction**} \\ \cline{2-13}  & \multicolumn{6}{c}{**L**\({}_{\text{CH4}}\)**} & \multicolumn{1}{c}{**X**\({}_{\text{CO2}}\)**} & \multicolumn{1}{c}{**Y**\({}_{\text{H2}}\)**} & \multicolumn{1}{c}{**Y**\({}_{\text{CO}}\)**} & \multicolumn{1}{c}{**H\({}_{2}\)/CO**} & \multicolumn{1}{c}{**a**\({}_{\text{CO2}}\)**} & \multicolumn{1}{c}{**d**\({}_{\text{NiO}}\)**} & \multicolumn{1}{c}{**m**\({}_{\text{NH}}\)**} & \multicolumn{1}{c}{**m**\({}_{\text{NH}}\)**} & \multicolumn{1}{c}{**\({}_{\text{NH}}\)**} & \multicolumn{1}{c}{**\({}_{\text{NH}}\)**} & \multicolumn{1}{c}{**\%**} & \multicolumn{1}{c}{**\%**} \\ \hline Ni/CeMg-C-S-O & 12 & 22 & 0 & 8 & 0 & 5.402 & 39 & 51 &
\begin{tabular}{c} No \\ phase \\ \end{tabular} & 0.04 & \(-\)0.09 \\ Ni/CeMg-A-S-V & 72 & 87 & 67 & 77 & 1.2 & 5.399 & 31 & ND 1 & 31 & \(-\)3.0 & \(-\)0.76 \\ Ni/CeMg-A-S-O & 74 & 75 & 65 & 72 & 1.3 & 5.402 & 35 & ND 1 & 46 & 0.71 & \(-\)0.15 \\ Ni-Pd/CeMg-A-S-V & 57 & 64 & 55 & 62 & 1.4 & 5.399 & 26 & 21 & 16 & 0.6 & \(-\)0.36 \\ Ni/CeMg-A-P-O & 51 & 71 & 49 & 59 & 1.1 & 5.400 & 47 & ND 1 & 83 & 0.69 & 0.59 \\ \hline \hline \end{tabular}  
* Not determined due to low intensity of the peak.  
\end{table} 
Table 5: Initial activity in CSMR at 750 \({}^{\circ}\)C, XRD and thermal analysis data after 24 h on stream in CSMR at 750 \({}^{\circ}\)C.  
Figure 6 shows data on the stability of catalysts in CSMR depending on the synthesis method and the composition of the active component.