Abstract
In this work, plasma-catalytic removal of H2S over LaxMnO3 (x = 0.90, 0.95, 1, 1.05 and 1.10) has been studied in a coaxial dielectric barrier discharge (DBD) reactor. The non-stoichiometric effect of the LaxMnO3 catalysts on the removal of H2S and sulfur balance in the plasma-catalytic process has been investigated as a function of specific energy density (SED). The integration of the plasma with the LaxMnO3 catalysts significantly enhanced the reaction performance compared to the process using plasma alone. The highest H2S removal of 96.4% and sulfur balance of 90.5% were achieved over the La0.90MnO3 catalyst, while the major products included SO2 and SO3. The missing sulfur could be ascribed to the sulfur deposited on the catalyst surfaces. The non-stoichiometric LaxMnO3 catalyst exhibited larger specific surface areas and smaller crystallite sizes compared to the LaMnO3 catalyst. The non-stoichiometric effect changed their redox properties as the decreased La/Mn ratio favored the transformation of Mn3+ to Mn4+, which contributed to the generation of oxygen vacancies on the catalyst surfaces. The XPS and H2-TPR results confirmed that the Mn-rich catalysts showed the higher relative concentration of surface adsorbed oxygen (Oads) and lower reduction temperature compared to LaMnO3 catalyst. The reaction performance of the plasma-catalytic oxidation of H2S is closely related to the relative concentration of Oads formed on the catalyst surfaces and the reducibility of the catalysts.
Highlights
The emission of odors from various sources including wastewater treatment and municipal solid waste (MSW) treatment facilities have become a public concern due to their negative effect on air quality and human health, especially on sensitive or sick people [1]
A series of non-stoichiometric Lax MnO3 catalysts were evaluated in the plasma-catalytic oxidative removal of hydrogen sulfide (H2 S) using a non-thermal plasma dielectric barrier discharge (DBD) reactor in terms of H2 S removal and sulfur balance of the plasma process
H2 S removal and sulfur balance compared to the plasma process without using a catalyst
Summary
The emission of odors from various sources including wastewater treatment and municipal solid waste (MSW) treatment facilities have become a public concern due to their negative effect on air quality and human health, especially on sensitive or sick people [1]. In the last three decades, the combination of non-thermal plasma and heterogeneous catalysis, known as “plasma-catalysis” has been demonstrated as a promising emerging process for the removal of low concentration gas pollutants including odors with reduced formation of by-products and enhanced process performance [14,15,16,17]. Reported that the removal of trichloroethylene was increased by 13.9% when packing a Pd/LaMnO3 catalyst into a negative DC corona discharge reactor at a specific energy density (SED) of 460 J·L−1 compared to the plasma reaction without a catalyst They found that the coupling of the plasma-catalyst coupling significantly reduced the formation of major by-product CHCl3 [23]. Brunauer-Emmett-Teller (BET) surface measurement, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature programmed reduction of H2 (H2 -TPR) to understand the structure-activity relationships between the Lax MnO3 catalysts and the plasma-catalytic process and the role of these catalysts in the plasma-catalytic process
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