High-temperature sulfur capture by a Mn-Mo sorbent: An investigation of regeneration conditions and SO<inf>2</inf> formation and prevention

Abstract

The regeneration performance of a solid sorbent (alumina-supported 15Mn8Mo) for sulfur capture at high temperature has been studied. The regeneration of the sulfided sorbent was performed by oxidizing at different temperatures (400 – 800 °C) and O2 concentrations (0.21 – 21 %). Temperature had a larger impact on the regeneration than O2 concentration. An unwanted side reaction during sulfur capture is SO2 formation. Two pathways to SO2 formation were identified, either via sulfate formation and decomposition or via oxidation of H2S. A new regeneration method which avoids SO2 formation and achieves low residual H2S level in the gas phase involves adding an extra H2 pre-reduction step between the regular O2 -regeneration and the subsequent sorption step, i.e., a O2 – H2 regeneration. The stability of the sorbent was verified by 10 repeated sorption/regeneration cycles, with the sorbent regenerated either via the oxidative method or the new O2 – H2 regeneration method.