Competitive Adsorption of Methanol–Acetone on Surface Functionalization (−COOH, −OH, −NH2, and −SO3H): Grand Canonical Monte Carlo and Density Functional Theory Simulations

The capture and separation properties of surface-functionalized activated carbons (AC-Rs, R= -COOH, -OH, -NH₂, and -SO₃H) for the methanol-acetone mixture were investigated for the first time by grand canonical Monte Carlo simulation (GCMC) and density functional theory (DFT). The effects of surface functional groups and structural characteristics of AC-Rs on the adsorption and separation behaviors of methanol and acetone were clarified. The surface functional group with strong electron-donating or electron-accepting capacity (i.e., -NH₂, -OH, and -SO₃H) was a crucial factor for the methanol-acetone capture and separation performance at the lower pressure range, and the accessible surface area was found to be another determinative factor. AC-NH₂ with the relatively large accessible surface area (4497 m²/g) exhibited an efficient capture performance for the single component (15.7 mol/kg for methanol and 6.7 mol/kg for acetone) and the highest methanol/acetone selectivity (∼23) at 0.02 kPa. At high pressures, the surface functionalization and available pore volume of AC-Rs played pivotal roles in the adsorptive separation process. This study provided mechanistic insights on how the surface functional groups affected the capture and separation properties of ACs, which would further provide a rational alternative strategy in the preparation and synthesis of ACs for the effective gas mixture separation.