AO<i><sub>x</sub></i>–MnO<i><sub>x</sub></i> (A = Ni, Cu, Fe, or Co) Nanocatalysts Fabricated by the Mechanochemical Preparation Method for Lean Methane Catalytic Combustion Assisted by a DBD Plasma Reactor
Ehsan Akbari, Seyed Mehdi Alavi, Mehran Rezaei, Zahra Montazeri
Abstract
A series of AO x (10)–MnO x (A: Ni, Cu, Fe, and Co) nanocatalysts were prepared by the solid-state mechanochemical preparation method, and a combination of the catalytic system contains a fixed bed, and a dielectric barrier discharge (DBD) reactor was used for lean CH 4 catalytic combustion over these samples at low temperature. Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), and H 2 temperature-programmed reduction (TPR) analyses were applied for catalyst characterization. The structural features of the as-calcined samples showed that the CuO(10)–MnO x nanocatalyst possessed the highest specific surface area (23 m 2 ·g –1 ) and supreme reduction properties at low temperatures. The activity results demonstrated that applying a DBD reactor remarkably improved the catalytic combustion efficiency of all studied catalysts. Methane combustion performs only when the operating temperature was higher than 300 °C typically, but in the presence of a weak plasma, the methane combustion reaction was improved overall, and the processing temperature was significantly reduced to lower than 100 °C. DBD could improve the component reduction to release the lattice oxygen, promoting methane oxidation. Also, the results presented that the catalyst composition remarkably influences the CH 4 conversion. Among the surveyed samples, the highest activity belonged to the CuO(10)–MnO x nanocatalyst and the CH 4 conversion was about 70% at 100 °C under the combined catalytic system. Moreover, the results confirmed that plasma could reduce the content of active metal to some extent while keeping the same performance. The results showed that the CuO(10)–MnO x has high stability at 350 °C for a 15 h reaction time. Furthermore, the influence of gas hourly space velocity (GHSV) and O 2 /CH 4 molar ratio was evaluated on the CH 4 conversion of the selected catalyst under two catalytic systems.