ORIGINAL PAPER Elimination of the azeotropic point of acetone and methanol by 1,3-dimethylimidazolium dimethylphosphate: an ab initio calculation study Guangren Yu 1 & Xiaomin Liu 2 & Xiaochun Zhang 2 & Xiaochun Chen 1 & Zhiping Liu 1 & Ahmed A. Abdeltawab 3 Received: 16 September 2016 /Accepted: 11 January 2017 # Springer-Verlag Berlin Heidelberg 2017 Abstract 1,3-Dimethylimidazolium dimethylphosphate ([C 1 mim][DMP]) was observed experimentally to be able to eliminate the atmospheric azeotropic point of acetone and methanol, which is an important azeotrope generally en- countered in furfural production and the Fischer-Tropsch process. Here, we employed ab initio calculation to under- stand the underlying mechanism of [C 1 mim][DMP] in elim- inating the azeotropic point of acetone and methanol. Structure, energy and interaction in binary-, ternary- and quaternary-clusters composed of methanol, acetone, [C 1 mim] + or/and [DMP]‾ were calculated. The σ-hole, AIM and NBO analyses were performed to understand in- termolecular interaction with electron density, electron occu- pancy, charge transfer and molecular orbital interaction. Hydrogen bond interaction plays a key role in azeotropic point elimination; due to the much stronger hydrogen bond interaction between methanol and [C 1 mim][DMP] than that between acetone and [C 1 mim][DMP], [C 1 mim][DMP] pre- fers to interact with methanol rather than acetone, and the original interaction between methanol and acetone is sepa- rated by [C 1 mim][DMP]. The hydrogen bond is from the orbital interaction between O lone-pair-electron orbitals of the hydrogen bond acceptor and σ * (C-H) or σ * (O–H) anti-bonding orbitals of the hydrogen bond donor, where remarkable electron or charge transfer occurs. These theoret- ical calculation results are in agreement with the experimen- tal observation that [C 1 mim][DMP] eliminates the azeotropic point of methanol and acetone. This work shows that ab initio calculation may be employed to rationalize the design or synthesis of ionic liquids for separating azeotropes. Keywords Azeotropic point elimination . Ionic liquid . Ab initio . Hydrogen bond Introduction Separation of an azeotropic system, for which simple distilla- tion is impossible, is a very challenging industrial process. Extractive distillation, in which an entrainer is added to alter relative volatility and eliminate azeotropic point through interacting with one component, is generally employed to separate such azeotropic systems. Organic solvents, inorganic salts or some hyperbranched polymers are common entrainers, e.g., CaCl 2 or KCH 3 COO for ethanol + water [ 1 ]; butoxypropanol for 2-propanol + water and propyl butyrate for 1-propanol + water [2]; hyperbranched polyesteramide, NaCl or CaCl 2 for water + tetrahydrofuran [3, 4]; 3-pentanone, acetophenone, 2,4-pentanedione or ethylacetoacetate for methanol + acetone [5]; LiCl, CaCl 2 , CaNO 3 , KCH 3 COO or NaI for chloroform + methanol [6]. There are, however, still some challenges in extractive distillation, e.g., erosion of the sieve plate, precipitation of solid salt in towers employing inorganic salt entrainer; contamination of distillate with Electronic supplementary material The online version of this article (doi:10.1007/s00894-017-3218-y) contains supplementary material, which is available to authorized users. * Zhiping Liu liuzhp@mail.buct.edu.cn 1 College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, People’ s Republic of China 2 Beijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex Systems, Key Laboratory of Green Process and Engineering. Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, People’ s Republic of China 3 Department of Chemistry, College of Science, King Saud University, Riyadh 11451, Saudi Arabia J Mol Model (2017) 23:74 DOI 10.1007/s00894-017-3218-y