Experimental investigation and molecular simulations of adsorption of MeOH-DMC Azeotrope onto α-Al2O3 (0 0 1) Surface

Abstract

In this paper, the adsorption behaviours of the MeOH-DMC azeotropic system onto α-Al2O3 were investigated from both practical and theoretical aspects for the first time. The experimental results showed that the static MeOH- and DMC-adsorption capacities of α-Al2O3 were 325.52 and 70.32 mg·g−1, respectively. The selectivity S was 4.63 and the dynamic separation factor α was 4.2. Then, density functional theory (DFT) was used to reveal possible interactions between the constructed azeotrope clusters and the α-Al2O3 (0 0 1) surface. Molecular simulation results indicated that although there were different azeotropic clusters in the bulk liquid, most of the H-bonds were destroyed when they approached the solid surface. The MeOH dimers were adsorbed onto both Al and O sites via chemisorption and H-bonds, while DMC monomers mainly occupied the Al sites. Thus, chemisorption on Al sites and multi-layer adsorption played a critical role in selective adsorption. Moreover, the competition between MeOH and DMC for adsorption sites might also cause a big difference between the MeOH- and DMC-adsorption capacities of α-Al2O3.