Cycled Storage-Discharge Plasma Catalytic Degradation of Toluene Using Metal Oxide Loaded MS-13X and Glass Beads Packed Bed Dielectric Barrier Discharge Reactor

Abstract

In this study, a cycled storage-discharge (CSD) plasma catalytic system packed with MOx/MS-13X (M = Cu, Mn, or Cu–Mn) and glass beads was investigated for the abatement of toluene in dry air. The total amount of adsorbed toluene, the catalytic performance of MOx/MS-13X, the energy cost, and the energy yield of the CSD plasma catalysis process were investigated for the different metal-loaded MS-13X samples under study. The metal loading on MS-13X enhanced the mineralization efficiency and reduced the energy cost to remedy 1 m3 of air when compared to unloaded MS-13X. The lowest energy cost (0.25 kWh <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot \text{m}^{-3}$ </tex-math></inline-formula> ) and the highest energy yield (4.37 g/kWh) were obtained using CuMnOx/MS-13X as an adsorbent and catalyst. The influence of the amount of toluene initially adsorbed on CuMnOx/MS-13X on the mineralization efficiency of the CSD plasma catalysis process was studied. The highest COx selectivity (82%) was obtained for the adsorption of 0.23 mmol/g of toluene on CuMnOx/MS-13X, which corresponded to an adsorption time of 2 h. The stability and regenerability of the CuMnOx/ MS-13X catalyst were examined during four cycles of CSD plasma catalytic abatement of 0.23 mmol/g of adsorbed toluene by comparing: 1) the amount of adsorbed toluene; 2) breakthrough time; 3) carbon balance; and 4) the bulk and surface properties of fresh and nonthermal plasma (NTP) regenerated CuMnOx/ MS-13X. The crystallinity, textural properties, elemental composition of the CuMnOx/MS-13X zeolite, and the oxidation state of the metals loaded on the zeolite did not change upon NTP exposure during four cycles of CSD plasma catalysis. Moreover, in this work, NTP exposure also showed to be successful in the regeneration of the CuMnOx/MS-13X zeolite for the CSD plasma catalytic abatement of toluene.