Effects of H2S and H2O on carbon deposition over La0.4Sr0.5Ba0.1TiO3/YSZ perovskite anodes in methane fueled SOFCs

Direct methane oxidation on La1−Sr Cr1FeyO3− perovskite-type oxides as potential anode for intermediate temperature solid oxide fuel cells

“…Nevertheless, it is necessary to outline that the ability to oxidize hydrogen sulphide is conditioned by CH 4 /H 2 S molar ratio [3]. Taking into account that 150 ppm H 2 S is a reliable condition for CH 4 -rich renewable fuels, two significant results should be emphasized: (i) the production of SO 2 between 250 • C and 600 • C; (ii) the consecutive selectivity towards total and partial methane oxidations in the presence of H 2 S. Actually, H 2 S is mainly oxidized to SO 2 , but this process does not inhibit the total methane oxidation that starts in any case at ∼450 • C, like in the absence of H 2 S. This finding suggests that the presence of H 2 S leaves unaltered the active sites of the catalyst, or at least has a promoting effect on methane conversion, as proposed in literature for other oxides [2,3,8].…”

“…The gas phase reaction between CH 4 and H 2 S coupled up to CS 2 formation, as well as the thermal decomposition of H 2 S are both endothermic reactions, and therefore, take place at high temperatures [2,3]. The main problem of carbon disulfide is that it easily decomposes forming sulphur poisoning, and in fact Danilovic et al and Vincent et al [3,10] reported CS 2 formation under electrochemical regime.…”

“…∼500-850 • C. These fuels, however, contain traces of H 2 S, a sulphur poison font, able to negatively affect the overall performance of the fuel cell. As a matter of fact, both sulphur and carbon deposits over the surface of anode material are considered the major limiting factors for the development of IT-SOFC fuelled with biogas or natural gas [2][3][4].…”

“…(1) and (2) might occur upon the surface of the anode catalyst, for instance methane steam and dry reforming reactions leading to syngas [5]. However, the main risk for the lifetime of the anode catalyst is represented by the cracking of methane, Eq.…”

“…Water production during the total methane oxidation may reduce carbon coke formation occurring at high temperature [2,5]. On the whole, carbon deposition may be avoided, or at least limited, by the continuous incoming to the anode of oxide ions transferred from the cathode.…”