## 3 Results and Discussion
### GC of the Exhaust Gas
The highest growth of the energy efficiency is produced when the gas flow varies. The energy efficiency of the designed reactor increased from 1.1 to 6.7 mmol/kj when the gas flow varied from 1 to 5 sLm at the applied voltage of 14 kV and a power electrode rotation frequency of 18,000 rpm. Although the LPG conversion decreased with the flow due to the formation of less shocks in the plasma, higher inlet flows produced a greater amount of LPG treated by the time unit. For a fixed applied voltage and LPG gas flow, Figure 5b shows the dependence of energy efficiency on the frequency of the rotating power electrode. As shown, the rotation electrode produced a more energy efficient conversion of LPG. It is possible to treat a larger amount of LPG gas with less energy consumption and the highest number of filaments produced in the reactor when the electrode started to rotate (see Figure 3), produced a better LPG conversion with a small variation of the consumed power. The energy efficiency at the static configuration had a maximum value of 1.65 mmol/kj in this work which was more than the 1.21 mmol/kj in ref. [14]. Moreover, the maximum value of the energy efficiency was 6.7 mmol/kj in the applied voltage of 14 kV, rotational  
Figure 5: The energy efficiency of hydrogen production versus (**a**) different voltages applied on the stationary power electrode at 1 sLm gas flow rate, (**b**) rotational frequencies of power electrode at 14 kV applied voltage and 1 sLm gas flow rate, and (**c**) gas flow rates at 14 kV applied voltage and 18,000 rpm rotational frequency of power electrode. frequency of 18,000 rpm, and gas flow rate of 5 sLm, which is higher than the efficiency peak of 1.46 mmol/k] in the ref. [14]. In hydrogen production applications, it is very relevant to know the ability of the reactor to produce hydrogen and its subproduct carbon molecule when the C4H10/C3H8 species are decomposed. The selectivities of H2 and C2 species are defined with this purpose:  
\[ \begin{split}\text{H}_{2}\text{ Selectivity}=\frac{\text{ moles of H}_{2}\text{ formed}}{5\times\text{moles of C}_{4}\text{H}_{10}\text{ converted }+4\times\text{moles of C}_{3}\text{H}_{8}\text{ converted}}\\ \text{C}_{2}\text{ Selectivity}\\ =\frac{\text{ moles of C}_{2}\text{ formed}}{2\times\text{moles of C}_{4} \text{H}_{10}\text{ converted }+1.5\times\text{moles of C}_{3}\text{H}_{8}\text{ converted}}\end{split}  \tag{4}\]  
The selectivities depend on the reactions responsible for the hydrogen and carbon production from the dissociation of the C4H10/C3H8 molecules and their derivatives. A detailed study of the possible reactions that occur inside the filamentary is presented in Section 3.1. Figure 6 plots the dependence of the H2 selectivity on the applied voltage, the electrode rotation frequency, and the gas flow rate. Figure 6a shows that selectivity grows with the applied voltage for the stationary power electrode, and that means that the increase of the C4H10/C3H8 conversion is accompanied by a more effective H2 formation when the voltage grows. The selectivity raises also with the electrode rotation frequency in the range from 9000 to 18,000 rpm (Figure 6b), being the maximum value of this factor equal to 98% for 18,000 rpm. It is shown that, in the designed reactor, the rotation of the power electrode allows for improving the H2 formation with a low power consumption. Conversely to the other parameters, when the gas flow rate increases in the range from 1 to 5 sLm, the hydrogen selectivity decreases from 98 to 84% (Figure 6c), and that means that the hydrogen released when the C4H10/C3H8 molecules are decomposed by forming other species are different to H2 molecules. Therefore, despite the improvement of energy efficiency with the gas flow, the conversion factors and efficiency of the H2 formation decrease. Figure 6 also shows the variations of C2 selectivity as a function of voltage applied on the electrode, rotation frequency of the power electrode, and the gas flow rate.