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.