Separation of azeotrope acetone-methanol mixture at high-concentration conditions: Experimental and theoretical perspective of the molecular packing effects in mesopores

Abstract

The recycling and concentration of acetone-methanol mixture organic solvents are very important to the chemical industry and biologically related processes. Hence, the separation properties of microporous and mesoporous activated carbons (MIC and MEC) for the acetone-methanol mixture were investigated for the first time by combining experiments and theoretical calculations. The results showed that the calculated dynamic acetone (methanol) adsorption capacities of MIC and MEC are 1.60 (10.66) and 5.15 (6.01) mmol/g at high pressures, respectively. MEC exhibited a greater methanol/acetone selectivity (6.66) than MIC (1.17). Subsequent theoretical calculations studied the adsorption behaviors of acetone and methanol molecules from the perspective of the adsorbate-framework as well as adsorbate–adsorbate interactions and found the different molecular structure of acetone and methanol was the main factor in their different separation preferences. Notably, the molecular packing effects associated with three molecular packing steps in the separation were further clarified by the radical distribution functions and self-created slit model. The 2.0–3.0 nm mesopore had more unfilled pore spaces after adsorbing a layer of acetone molecules, and thus had a significant selectivity towards methanol molecules.