Chemically selective gas sweetening without thermal-swing regeneration

Abstract

Natural gas purifications using chemically selective hydrogen sulfide (H₂S) sorbents could be more efficient if chemical selectivity for H₂S could be maintained without thermal regeneration of the sorbent. We used tertiary alkanolamines to reversibly capture H₂S in the absence of water to produce hydrosulfide-based ionic liquids in high yield. These alkanolammonium hydrosulfide ionic liquids release H₂S by exposure to inert gas or by mild heating. H₂S can be rapidly and nearly quantitatively released at ambient temperature from the alkanolammonium hydrosulfide ionic liquids by the addition of nonpolar antisolvents, some of which naturally phase separate from the spent alkanolamine. The antisolvent-induced regeneration of the alkanolamine potentially allows an efficient H₂S gas scrubbing process that is chemically selective and can be operated continuously at or near ambient temperature.