# Pentane Depletion by a Surface DBD and Catalysis Processing
## 5 Conclusions  
In this work, an SDBD reactor was employed for the decomposition of pentane, at different plasma discharge power levels (16.9 W and 44.2 W), gas concentrations in air, and plasma treatment time. It was found that pentane could be totally depleted in a few (about 5) minutes at 44.2 W, where the efficiency reaches the value of 1.3 g/kWh for the initial pentane concentration of 1200 ppm. The maximum efficiency of 1.8 g/kWh was found at 16.9 W, also for the initial pentane concentration of 1200 ppm. The efficiency increased with the pentane concentration, suggesting that plasma effects are volume-dependent because the reactions occurred in the gas phase. The fact that efficiency decreased with power suggests that plasma energy was either not well-distributed in the reactor or that the plasma produced a larger amount of by-products such as ozone, thus limiting other chemical reactions [28].  
The analysis of the temporal evolution of pentane and the associated concentrations of the intermediate reaction products allowed us to quantitatively describe the kinetics of VOC depletion in the plasma hybrid system. In an SDBD-catalyst reactor, the plasma primarily acts to decompose pentane, while the catalyst mostly concerns the intermediate reaction products. During the first minutes of treatment in a single experiment, gas processing is dominated by plasma decomposition of pentane, followed by the generation of the intermediate products, which are progressively depleted by the catalytic processes acting on longer time scales.  
Worthy of note is the fact that plasma dynamics depends on both the pentane concentration and applied power. It is faster at higher power and lower concentrations, where pentane is abated in less than 1 min. The typical time scale varies between 0.7 and 1.7 min for 300 ppm and 1200 ppm initial pentane concentrations, respectively. At extremely low powers, e.g., at 11 W, the pentane is not totally dissociated, and the time scale for abatement is longer, well above two minutes and roughly in the range of 2.5-5.3 min; this may be addressed by varying the concentrations between 300 ppm and 1200 ppm.  
Different metal catalysts have been investigated in single-stage plasma-catalytic gas cleaning processes for the oxidation of VOCs. Transition metal oxide catalysts in combination with plasma have attracted growing interest for pollution abatement because of their comparable performance and low cost. In our previous work, we found that the TiO\({}_{2}\) and/or WO\({}_{3}\) catalysts alone are not able to efficiently remove propane [31], while here, we managed to increase the pentane depletion by using plasma together with a catalyst, thus yielding an efficient abatement of the intermediate reaction products.  
Conceptualization, C.R., C.P. and M.D.; methodology, C.R., C.P. and M.D.; software, C.P. and H.E.R.; validation, C.P.; formal analysis, C.P. and H.E.R.; investigation, C.P.; resources, C.R.; data curation, C.P.; writing--original draft preparation, C.R., C.P., H.E.R. and M.D.; writing--review and editing, C.R., C.P., H.E.R., M.D. and M.S.; visualization, C.P.; supervision, C.R.; project administration, C.R.; funding acquisition, C.R. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The data that support the findings of this study are available from the corresponding author upon reasonable request.  
The authors gratefully acknowledge technical support from Alessandro Mietner and Alessandro Bau' in device development and experiment execution.  
The authors declare no conflict of interest.