Functionalized GO Membranes for Efficient Separation of Acid Gases from Natural Gas: A Computational Mechanistic Understanding

Abstract

Membrane separation technology is applied in natural gas processing, while a high-performance membrane is highly in demand. This paper considers the bright future of functionalized graphene oxide (GO) membranes in acid gas removal from natural gas. By molecular simulations, the adsorption and diffusion behaviors of several unary gases (N2, CH4, CO2, H2S, and SO2) are explored in the 1,4-phenylenediamine-2-sulfonate (PDASA)-doped GO channels. Molecular insights show that the multilayer adsorption of acid gases evaluates well by the Redlich-Peterson model. A tiny amount of PDASA promotes the solubility coefficient of CO2 and H2S, respectively, up to 4.5 and 5.3 mmol·g−1·kPa−1, nearly 2.5 times higher than those of a pure GO membrane, which is due to the improved binding affinity, great isosteric heat, and hydrogen bonds, while N2 and CH4 only show single-layer adsorption with solubility coefficients lower than 0.002 mmol·g−1·kPa−1, and their weak adsorption is insusceptible to PDASA. Although acid gas diffusivity in GO channels is inhibited below 20 × 10−6 cm2·s−1 by PDASA, the solubility coefficient of acid gases is certainly high enough to ensure their separation efficiency. As a result, the permeabilities (P) of acid gases and their selectivities (α) over CH4 are simultaneously improved (PCO2 = 7265.5 Barrer, αCO2/CH4 = 95.7; P(H2S+CO2) = 42075.1 Barrer, αH2S/CH4= 243.8), which outperforms most of the ever-reported membranes. This theoretical study gives a mechanistic understanding of acid gas separation and provides a unique design strategy to develop high-performance GO membranes toward efficient natural gas processing.

Editorial for the Special Issue “Preparation and Application of Advanced Functional Membranes”

“…Liu et al's article [61] presents a computational mechanistic study that was conducted to understand how to remove acid gases from natural gas by using new functionalized GO membranes. They studied the adsorption and diffusion of several gases in 1,4-phenylenediamine-2-sulfonate (PDASA)-doped GO membrane channels, providing new insights into the solubility coefficient of CO 2 and H 2 S. They estimated, for these two gases, a binding affinity that is higher than that computed for CH 4 and N 2 .…”

CFD Simulation of Hydrogen Sulfide (H2S) Desulfurization Using Ionic Liquids and Graphene Oxide Membrane

“…1-ethyl-3-methylimidazolium (emim)-based ionic liquids with bis-(trifluoromethyl) sulfonylimide (NTf2) anion were selected due to their high H 2 S diffusion coefficient. The diffusion coefficients of the H 2 S inside the water (D H2S-water ), ionic liquid and the functionalized graphene oxide (GO) membrane (D H2S-GO ) and ionic liquid (D H2S-IL ) are shown in Table 1 [14][15][16]. It should be noted that the H 2 S diffusion coefficient inside graphene oxide (GO) is much higher than the H 2 S diffusion coefficient inside Nafion112 [17].…”

“…Table 1. Diffusion coefficients of hydrogen sulfide in the water (D H2S-water ), in the functionalized graphene oxide (GO) membrane (D H2S-GO ) and the ionic liquid (D H2S-IL ) [14][15][16].…”

“…phene oxide (GO) membrane (DH2S-GO) and the ionic liquid (DH2S-IL) [14][15][16]. The GO membrane offers several advantages such as:…”