Operando sulfur speciation during sulfur poisoning-regeneration of Ru/SiO 2 and Ru/Al 2 O 3 using non-resonant sulfur Kα 1,2 emission.

A periodic oxidative regeneration of a sulfur-poisoned methanation catalyst is an alternative to the expensive state-of-the-art process of syngas cleaning using wet scrubbers. Here we have employed operando X-ray emission spectroscopy (XES) to study sulfur speciation on Ru/SiO ₂ and Ru/Al ₂ O ₃ during methanation in the presence of H ₂ S and subsequent regeneration in dilute O ₂ at 360 °C. XES allowed us to obtain semi-quantitative sulfur speciation and to monitor changes in the absolute sulfur concentration. It was established that Al ₂ O ₃ , in contrast to SiO ₂ , forms sulfite/sulfate species by reacting with SO ₂ , which is released from the poisoned Ru surface upon oxidative treatment. The concentration of sulfite/sulfate species is reduced upon switching the feed to H ₂ /CO while no simultaneous increase in sulfide concentration is observed. For both catalysts, the regenerative treatment removes adsorbed sulfur as SO ₂ only partially, which we propose is the main reason for the incomplete activity recovery of the poisoned catalyst after regeneration.
Competing Interests: There are no conflicts to declare.
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