Decomposition of Potent Greenhouse Gas Sulfur Hexafluoride (SF₆) by Kirschsteinite-dominant Stainless Steel Slag

Abstract

In this investigation, kirschsteinite-dominant stainless steel slag (SSS) has been found to decompose sulfur hexafluoride (SF6) with the activity higher than pure metal oxides, such as Fe2O3 and CaO. SSS is mainly made up of CaO·FeO·SiO2(CFS)/MgO·FeO·MnO(RO) phase conglomeration. The SF6 decomposition reaction with SSS at 500-700 °C generated solid MF2/MF3 and gaseous SiF4, SO2/SO3 as well as HF. When 10 wt % of SSS was replaced by Fe2O3 or CaO, the SF6 decomposition amount decreased from 21.0 to 15.2 or 15.0 mg/g at 600 °C. The advantage of SSS over Fe2O3 or CaO in the SF6 decomposition is related to its own special microstructure and composition. The dispersion of each oxide component in SSS reduces the sintering of freshly formed MF2/MF3, which is severe in the case of pure metal oxides and inhibits the continuous reaction of inner components. Moreover, SiO2 in SSS reacts with SF6 and evolves as gaseous SiF4, which leaves SSS with voids and consequently exposes inner oxides for further reactions. In addition, we have found that oxygen significantly inhibited the SF6 decomposition with SSS while H2O did not, which could be explained in terms of reaction pathways. This research thus demonstrates that waste material SSS could be potentially an effective removal reagent of greenhouse gas SF6.

The Decomposition Products of Sulfur Hexafluoride (SF6) with Metals Dissolved in Liquid Ammonia

“…The reaction between SF 6 and caesium in liquid ammonia at −61 • C gave several good hints as to the formation of CsF and Cs 2 S [10].…”

“…Sulfur hexafluoride, SF 6 , is a colorless, nonflammable and highly inert gas with an extremely high global warming potential (GWP) [1,2]. Because of its excellent electric characteristics and high chemical stability, it is used as a dielectric medium in high-voltage circuit breakers, transformers, capacitors and many more industrial applications [3].…”

“…Because of its excellent electric characteristics and high chemical stability, it is used as a dielectric medium in high-voltage circuit breakers, transformers, capacitors and many more industrial applications [3]. Since the search for a replacement material that is less harmful to the environment or that is easier to dispose of has not yet been successful, the decomposition of sulfur hexafluoride remains a current field of research [4][5][6].…”

“…The activation of SF 6 was first shown in the literature in 1900 by Moissan and Lebeau [7]. They described the reaction between sulfur hexafluoride and hydrogen sulfide to sulfur and hydrogen fluoride.…”

“…They described the reaction between sulfur hexafluoride and hydrogen sulfide to sulfur and hydrogen fluoride. Furthermore, reactions with elemental sodium at 200 • C and several catalytic activations with nickel-or rhodium-complexes of SF 6 have been published [4,5,8].…”