Plasma-Catalytic Oxidation of n-Butane over $\alpha $-MnO$_{2}$ in a Temperature-Controlled Twin Surface Dielectric Barrier Discharge Reactor

Volatile organic compounds (VOCs) are detrimental for the environment. Therefore, an efficient removal of VOCs from exhaust gases is necessary. The removal by plasma-assisted catalysis may be a promising replacement for energy-demanding techniques. Dielectric barrier discharges (DBDs) have already shown promising results for VOC conversion in atmospheric pressure plasmas. A combination of plasma with well-known oxidation catalysts can lead to synergistic effects. The applied twin surface DBD geometry has the advantage of a thin catalyst layer which can be deposited in a well-controlled distance to the plasma-ignited area. The thermal oxidation of n-butane has been performed in synthetic air (20.5\% O$_2$, 79.5\% N$_2$) over MnO$_2$ as catalyst up to 450 $^\circ$C. MnO$_2$ achieves conversion of 5\% at 180 $^\circ$C and 95\% at 319 $^\circ$C with closed carbon balance. For the plasma operation n-butane was oxidized in synthetic air. Degrees of conversion of up to 36\% without catalyst and 46\% with mask-coated catalyst were reached. The presence of the catalyst increased both CO$_2$ selectivity and carbon balance. By heating the reactor to 140 $^\circ$C in the presence of the catalyst, conversion increased further to 58\% demonstrating synergistic plasma-catalyst interactions.