PNNL

Abstract

Natural gas purifications to reactivate chemically selective hydrogen sulfide (H2S) sorbents could be far 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 allows an efficient H2S gas scrubbing process that is chemically selective and can be operated continuously at ambient temperature.