Plasma-assisted catalytic reduction of SO2 to elemental sulfur: Influence of nonthermal plasma and temperature on iron sulfide catalyst

Herein, we report on low-temperature sulfur dioxide (SO2) reduction to elemental sulfur via the coupling of nonthermal plasma (NTP) with supported transition metal sulfide catalysts in a dielectric barrier discharge (DBD) reactor. The transition metals include Mo, Fe, Co, Ni, Cu, and Zn. Combining NTP with supported metal sulfide catalysts significantly promotes low-temperature reduction of SO2 by 148-200%, with over 98% selectivity to elemental sulfur. Over FeS2/Al2O3 catalyst at low temperatures (<250 degrees C), temperature does not influence SO2 conversion in the plasma catalytic process, whereas at higher temperatures, the reaction follows a similar trend as thermal catalysis. Strong synergistic effects are attained, as the sulfur yield is about 47-82% higher than the sum of the yield when using DBD-plasma and thermal catalysis separately. The physico-chemical properties of fresh and spent FeS2/Al2O3 catalysts after thermal and plasma reactions are evaluated by N-2 physisorption, FESEM, XPS, XRD, HRTEM, STEM/EDS, and EELS to understand plasma and thermal effects on the catalyst. Our investigations reveal that running the reaction under plasma preserves the surface FeS2 active phase, preventing its oxidation that otherwise occurs in the thermal catalysis process. Furthermore, plasma inhibits the thermal agglomeration of iron sulfide nanoparticles under reaction conditions. (C) 2020 Elsevier Inc. All rights reserved.