Promotion of activation of CH4 by H2S in oxidation of sour gas over sulfur tolerant SOFC anode catalysts

Hydrogen sulfide, usually considered to be an anode catalyst poison, strongly promotes methane oxidation over sulfur resistant catalysts. The role of H2S in oxidation of sour CH4 feed over a sulfur resistant SOFC anode catalyst at 850 °C has been determined through thermodynamic and experimental studies. The anode material was an intimately mixed 50/50 mass ratio composite of La0.4Sr0.6TiO3−δ and YSZ. The power density improved dramatically from 2 mW cm−2 with pure CH4 as fuel to more than 450 mW cm−2 for CH4 containing 20% H2S. However, H2S was not the only fuel converted, and its interaction with CH4 was the key factor in enhancement of performance. The anode effluent gas mixture included H2S, SO2, H2 and CS2 consistent with thermodynamic predictions. The role of H2S in the CH4 oxidation mechanism was determined, and showed that CH4 and H2S must be considered together as a fuel and not as two separate fuels. The types of electrochemical reactions that occurred in the fuel cell were strongly dependent on potential.

Figure optionsDownload as PowerPoint slideHighlights
► H2S promotes methane activation on LST.
► The methane/H2S electrocatalytic oxidation selectivity depends on applied voltage.
► The fuel mixture methane H2S, provides a very high power density compared to the respective single gases.
► The major components of a mechanism are proposed.