## 3 Results and Discussion  
Table 1 shows the elemental composition of metallic tubes, according to their grades. For titanium, the main impurities are iron, silicon, carbon, nickel-iron, manganese, and copper. Table 2 shows the main properties of the corundum tube (MKR-95). The content of Al\({}_{2}\)O\({}_{3}\) in the corundum tube is no less than 95%. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & \multicolumn{3}{c}{**Mass Fraction, \%**} \\ \cline{2-3}
**Chemical Element** &
\begin{tabular}{c} **Stainless Steel** \\ **(10 Ch18N10T)** \\ \end{tabular} & **Titanium (VT 1-0)** & **Nickel (NP2)** \\ \hline Fe & 63–67 & \(\leq\)0.15 & \(\leq\)0.1 \\ \hline Cr & 17–19 & – & – \\ \hline Ni & 10–11 & – & \(\geq\)99.5 \\ \hline Ti & – & 99.58–99.9 & \\ \hline Mn & 1–2 & – & \(\leq\)0.1 \\ \hline Si & \(\leq\)0.8 & \(\leq\)0.08 & – \\ \hline C & \(\leq\)0.1 & \(\leq\)0.05 & \(\leq\)0.1 \\ \hline P & \(\leq\)0.035 & – & \(\leq\)0.002 \\ \hline S & \(\leq\)0.02 & – & \(\leq\)0.005 \\ \hline Cu & – & – & \(\leq\)0.1 \\ \hline Pb & – & – & \(\leq\)0.02 \\ \hline Sn & – & – & \(\leq\)0.002 \\ \hline Sb & – & – & \(\leq\)0.002 \\ \hline Zn & – & – & \(\leq\)0.007 \\ \hline As & – & – & \(\leq\)0.002 \\ \hline Bi & – & – & \(\leq\)0.002 \\ \hline Cd & – & – & \(\leq\)0.002 \\ \hline N & – & \(\leq\)0.04 & – \\ \hline O & – & \(\leq\)0.1 & – \\ \hline H & – & \(\leq\)0.008 & – \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Elemental composition for metallic tubes. \begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{1}{c}{**Parameter**} & **Value** \\ \hline Content of Al\({}_{2}\)O\({}_{3}\), no less than, \% & 95 \\ \hline Density, g/cm\({}^{3}\) & \(\geq\)3.7 \\ \hline Maximum working temperature, \({}^{\circ}\)C & 1600 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The main properties of the corundum tube (MKR-95). The composition of the gaseous product of methane pyrolysis at 1100 \({}^{\circ}\)C depending on the material of the reaction tube is shown in Table 3. It can be seen that the main pyrolysis product is hydrogen. In addition, compounds such as C\({}_{2}\)H\({}_{6}\), C\({}_{2}\)H\({}_{4}\), C\({}_{3}\)H\({}_{8}\), C\({}_{3}\)H\({}_{6}\), (CH\({}_{3}\))\({}_{3}\)CH, C\({}_{4}\)H\({}_{10}\), C\({}_{4}\)H\({}_{8}\), n-pentane, and hexane are also present in gaseous products. Ethylene shows the highest content--from 0.7 to 2.2 vol. %. The content of ethane is about 0.1 vol %. A comparison of the obtained results with previous studies is presented in Table 4. It shows the methane conversion values reported in various papers. When comparing, \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Component**} & \multicolumn{4}{c}{**The Content of the Component in the Gas Sample, vol. \%**} \\ \cline{2-5}  & \
\begin{tabular}{c} **Stainless Steel** \\ **(10 CH18N10T)** \\ \end{tabular} & **Titanium (VT 1-0)** & **Nickel (NP2)** &
\begin{tabular}{c} **Corundum** \\ **(MKR-95)** \\ \end{tabular} \\ \hline H\({}_{2}\) & 27.7523 & 41.5071 & 71.2657 & 73.3455 \\ \hline CH\({}_{4}\) & 71.4343 & 57.7904 & 26.7872 & 24.3096 \\ \hline C\({}_{2}\)H\({}_{6}\) & 0.0866 & 0.0587 & 0.1260 & 0.1026 \\ \hline C\({}_{2}\)H\({}_{4}\) & 0.6606 & 0.4833 & 1.7000 & 2.1650 \\ \hline C\({}_{3}\)H\({}_{8}\) & 0.0003 & 0.0003 & 0.0010 & 0.0009 \\ \hline C\({}_{3}\)H\({}_{6}\) & 0.0650 & 0.0344 & 0.0580 & 0.0764 \\ \hline (CH\({}_{3}\))\({}_{3}\)CH & \(-\) & 0.1116 & \(-\) & \(-\) \\ \hline C\({}_{4}\)H\({}_{10}\) & 0.0005 & \(-\) & 0.0168 & \(-\) \\ \hline C\({}_{4}\)H\({}_{8}\) & 0.0004 & 0.0002 & 0.0264 & \(-\) \\ \hline n-pentane & \(-\) & 0.0134 & 0.0189 & \(-\) \\ \hline hexane & \(-\) & 0.0005 & \(-\) & \(-\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The composition of gaseous product of methane pyrolysis at 1100 \({}^{\circ}\)C depending on the material of the reaction tube. Figure 2: The contents of CH\({}_{4}\) and H\({}_{2}\) in the gaseous product of methane pyrolysis at 1100 \({}^{\circ}\)C in tubes of different materials.