# Study of Soot Deposits during Continuous Methane Pyrolysis in a Corundum Tube
## 3 Results and Discussion
### Impurity Composition of Carbon Black  
Table 3 shows the impurity composition of soot obtained in different parts of experimental plant (in reactor tube and in filter) after the pyrolysis experiment at 1200 \({}^{\circ}\)C and a methane flow rate of 1 L/min. Soot samples in the form of a powder, shown in Figure 8B,C, were transferred for chemical (impurity composition) analysis.  
From Table 3 it is seen that the soot extracted from the tube has higher content of such elements as Mg (89 ppm), Ca (332 ppm), Al (94 ppm), Cu (2,7 ppm) as opposed to soot taken from a filter where the same elements have lower content: Mg (10 ppm), Ca (250 ppm), Al (81 ppm), Cu (0,51 ppm). This may be due to the fact that these elements are part of the tube and mix with the precipitated technical carbon during the pyrolysis process.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**N n/a**} & \multirow{2}{*}{**The Element**} & \multicolumn{2}{c}{**Element Content in a Soot Sample,**} & \multirow{2}{*}{**The Element Element**} & \multirow{2}{*}{**From the Filter**} \\ \cline{3-3} \cline{5-8}  & & & **Sample, ppm** & & & **ppm** \\ \cline{3-3} \cline{5-8}  & & & **From the Tube** & & & **Filter** \\ \hline
1 & Na & 5.0 \(\pm\) 0.2 & 6.7 \(\pm\) 0.5 & 27 & Tl & \textless{}0.002 & \textless{}0.04 \\ \hline
2 & Mg & 89 \(\pm\) 2 & 10 \(\pm\) 4 & 28 & Bi & \textless{}0.07 & 0.0088 \(\pm\) 0.0002 \\ \hline
3 & Al & 94 \(\pm\) 4 & 81 \(\pm\) 6 & 29 & Th & 0.043 \(\pm\) 0.006 & \textless{}0.002 \\ \hline
4 & K & \textless{}2 & \textless{}14 & 30 & U & 0.063 \(\pm\) 0.004 & \textless{}0.0003 \\ \hline
5 & Ca & 332 \(\pm\) 16 & 250 \(\pm\) 30 & 31 & Ru & \textless{}0.00004 & \textless{}0.0007 \\ \hline
6 & Cr & 1.3 \(\pm\) 0.4 & 16 \(\pm\) 3 & 32 & Rh & \textless{}0.00004 & \textless{}0.0003 \\ \hline
7 & Mn & 6.1 \(\pm\) 0.5 & 1.3 \(\pm\) 0.2 & 33 & Pd & 0.0008 \(\pm\) 0.0002 & \textless{}0.004 \\ \hline
8 & Fe & 12 \(\pm\) 4 & 63 \(\pm\) 9 & 34 & Ir & \textless{}0.0001 & \textless{}0.005 \\ \hline
9 & Ni & 0.87 \(\pm\) 0.01 & 11 \(\pm\) 1 & 35 & Pt & 0.0065 \(\pm\) 0.0005 & \textless{}0.001 \\ \hline
10 & Zn & 2.1 \(\pm\) 0.4 & 4.3 \(\pm\) 0.3 & 36 & Sc & 0.21 \(\pm\) 0.02 & \textless{}0.002 \\ \hline
11 & Ba & 1.8 \(\pm\) 0.1 & 1.1 \(\pm\) 0.3 & 37 & Y & 0.63 \(\pm\) 0.04 & 0.0034 \(\pm\) 0.0009 \\ \hline
12 & Pb & \textless{}0.5 & 9 \(\pm\) 1 & 38 & In & 0.0004 \(\pm\) 0.0001 & \textless{}0.0003 \\ \hline
13 & Li & 0.04 \(\pm\) 0.01 & 0.18 \(\pm\) 0.03 & 39 & La & 0.07 \(\pm\) 0.01 & 0.0020 \(\pm\) 0.0002 \\ \hline
14 & Be & 0.0052 \(\pm\) 0.0004 & \textless{}0.007 In turn, the composition of soot sampled in the filter is dominated by such elements as Pb (9 ppm), K (14 ppm), Cr (16 ppm), Fe (63 ppm), Ni (11 ppm). For comparison, the same elements in carbon black from the tube are Pb (0.5 ppm), K (2 ppm), Cr (1.3 ppm), Fe (12 ppm), Ni (0.87 ppm). This is due to the fact that the carbon black passes through the experimental plant, including the steel pipelines, at high temperature, interacting with them before reaching the filter. The total amount of impurities in the soot from the tube was 552 ppm, and in soot from the filter, 469 ppm. This means that the purity of the produced carbon black is about 99.95%.