Operando sulfur speciation during sulfur poisoning-regeneration of Ru/SiO2 and Ru/Al2O3 using non-resonant sulfur Kα1,2 emission

摘要

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.