Highly selective absorption separation of H2S and CO2 from CH4 by novel azole‐based protic ionic liquids

Abstract

AbstractRecently, the selective removal of H2S and CO2 has been highly desired in natural gas sweetening. Herein, four novel azole‐based protic ionic liquids (PILs) were designed and prepared through one‐step neutralization reaction. The solubility of H2S (0–1.0 bar), CO2 (0–1.0 bar), and CH4 (0–5.0 bar) was systematically measured at temperatures from 298.2 to 333.2 K. NMR and theoretical calculation were used to investigate the reaction mechanism between these PILs and H2S. Reaction equilibrium thermodynamic model (RETM) was screened to correlate the H2S solubility. Impressively, 1,5‐diazabicyclo[4,3,0] non‐5‐ene 1,2,4‐1H‐imidazolide ([DBNH][1,2,4‐triaz]) shows the highest H2S solubility (1.4 mol/mol or 7.3 mol/kg at 298.2 K and 1.0 bar) and superior H2S/CH4 (831) and CO2/CH4 (199) selectivities compared with literature results. Considering the excellent absorption capacity of H2S, high H2S/CH4, and CO2/CH4 selectivity, acceptable reversibility, as well as facile preparation process, it is believed that azole‐based PILs provide an attractive alternative in natural gas upgrading process.