## 2 Materials and Methods
### Catalytic Pyrolysis
#### 3.3.4 Characterization of Syngas Fraction  
The overall composition of the syngas product is presented in Table 8. Hydrocarbons constitute most of pyrolysis gases. The gases derived from thermal and catalytic pyrolysis of both surgical and FFP2 masks had average hydrocarbon contents between 77.8 and 85.5%. In all tests, the major compound was methane (CH\({}_{4}\)) with an average content of 47.9%. The highest volumetric content of CH\({}_{4}\) was observed in gases produced from catalytic pyrolysis of FFP2 masks with values between 50.9% and 52.5% in the function of the number of runs after the regeneration of sepiolite. Another relatively abundant hydrocarbon is ethane, with averages values of 16.0% and 13.2% for gases produced from the pyrolysis of surgical and FFP2 marks, respectively. Especially significant was the decrease in ethane (C\({}_{2}\)H\({}_{6}\)) content in the catalytic pyrolysis of FFP2 masks and the increase in methane content. Another important hydrocarbon is propane. It was found in low concentrations, while in some catalytic pyrolysis experiments it was not detected. These results agree with some previous \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Biochar Samples**} & \multicolumn{6}{c}{**Elements, wt. \%**} & \multirow{2}{*}{**C/N**} & \multirow{2}{*}{**C/H**} & \multirow{2}{*}{**HHV,**} \\ \cline{2-2} \cline{5-6}  & **N** & **C** & **H** & **S** & & & **O \({}^{*}\)** & **MJ/kg** \\ \hline FFP2 mask biochar & 5.37 & 59.81 & 9.35 & 0.00 & 25.47 & 11.13 & 6.40 & 32.88 \\ \hline FFP2 mask (5\% sepiolite 1 st run) biochar & 3.39 & 56.72 & 3.25 & 0.00 & 36.64 & 16.73 & 17.45 & 23.22 \\ \hline FFP2 mask (5\% sepiolite 2 nd run) biochar & 3.34 & 56.24 & 3.17 & 0.00 & 37.23 & 16.84 & 17.71 & 22.95 \\ \hline FFP2 mask (5\% sepiolite 3 rd run) biochar & 3.30 & 55.77 & 3.10 & 0.00 & 37.83 & 16.90 & 17.99 & 22.69 \\ \hline Surgical mask biochar & 1.13 & 50.01 & 7.53 & 0.00 & 41.34 & 44.26 & 6.64 & 27.08 \\ \hline Surgical mask (5\% sepiolite 1 st run) biochar & 2.81 & 70.92 & 3.92 & 0.00 & 22.35 & 25.24 & 18.09 & 28.82 \\ \hline Surgical mask (5\% sepiolite 2 nd run) biochar & 3.31 & 69.84 & 4.16 & 0.00 & 22.69 & 21.13 & 16.79 & 28.81 \\ \hline Surgical mask (5\% sepiolite 3 rd run) biochar & 3.80 & 68.76 & 4.40 & 0.00 & 23.04 & 18.09 & 15.63 & 28.80 \\ \hline \hline \end{tabular} \({}^{*}\) by difference between 100% and CNHS content, %.  
\end{table} 
Table 7: Solid biochar elemental analysis. studies [20; 23; 46] at similar operating conditions. However, other authors determined that the major component in their investigations was propene (C\({}_{3}\)H\({}_{6}\)) [25; 30] and other heavier components [6]. Regarding carbon dioxide (CO\({}_{2}\)), it was present in all gases at an average concentration of 11.0% and 10.4% for the gases of the pyrolysis of surgical and FFP2 marks, respectively. It has a negative effect, since it reduces the energy quality of the syngas. Furthermore, carbon monoxide (CO) was present in all gases, although in lower concentrations (between 3.6% and 9.6%). Variations were observed in the function of the type of mask, if the pyrolysis was thermal or catalytic and, in catalytic pyrolysis, the number of runs performed, but a clear tendency was not determined. The presence of oxygenated compounds in the gases may be due to the small amount of oxygen present in the masks, which can be attributed to the presence of other unidentified compounds constituting the different layers of the masks [40]. In addition, it could also be due to the air that inevitably enters during the loading of the material into the reactor. [PERSON] et al. [25] also found CO\({}_{2}\) and CO in the gases produced in the pyrolysis of masks at different temperatures. These authors attribute the presence of CO\({}_{2}\) and CO to the thermal cracking of the pyrolytic vapor and the oxygen content in the feed wastes.