Extractive distillation of methylal/methanol mixture using the mixture of dimethylformamide (DMF) and ionic liquid as entrainers

BACKGROUND Benzene–methanol azeotrope can be formed at atmospheric pressure. Extractive distillation is widely used in the separation of azeotrope. The key factor for extractive distillation is the selection of entrainer. The minimal total annual cost of extractive distillation process can be used as objective function to evaluate the separation performance of ionic liquid entrainer. Intermolecular interaction energy can be used to analyze separation mechanisms. RESULT An Aspen Plus software database belonging to the three ionic liquids 1‐hexyl‐3‐methylimidazolium acetate, 1‐octyl‐3‐methylimidazolium acetate and 1‐decyl‐3‐methylimidazolium acetate was established. The minimal total annual costs of three extractive distillation processes for the separation of benzene–methanol mixture with different ionic liquids were obtained by sequential iterative method. The feed rate of entrainer was also obtained under the optimized conditions. Among the three extractive distillation processes with different ionic liquid, the total annual cost and the entrainer feed rate of the extractive distillation process with 1‐hexyl‐3‐methylimidazolium acetate as entrainer are the smallest. The intermolecular interaction energies in the ternary system of benzene–methanol–ionic liquid were obtained using the Gaussian 09 software package based on the density functional theory. The separation mechanisms and the extractive distillation process of benzene–methanol azeotrope with ionic liquid as entrainer was interpreted by the intermolecular interaction energy. CONCLUSION The results show that the separation ability of 1‐hexyl‐3‐methylimidazolium acetate is higher than that of 1‐octyl‐3‐methylimidazolium acetate or 1‐decyl‐3‐methylimidazolium acetate. Intermolecular interaction energy analysis can be used in the screening and design of ionic liquid entrainer. © 2019 Society of Chemical Industry

Section: Introductionmentioning

confidence: 85%

“…In addition, the study of intermolecular interaction between IL entrainer and substance to be separated is helpful to the selection and design of IL entrainer with high performance. The strength of intermolecular interaction was quantitatively indicated by interaction energy …”

Section: Introductionmentioning

confidence: 99%

Evaluation of ionic liquid separation ability for the benzene–methanol mixture by extractive distillation

Wang

Feng

et al. 2019

“…Ionic liquids (ILs) are innovative solvents due to their excellent properties such as negligible vapor pressure, 13 strong dissolving capacity and good thermal stability. 14 Moreover, it is convenient and easy to obtain a highly efficient IL through design and recombination of anions and cations. 15,16 However, due to the huge database of anions and cations, it is necessary to establish an efficient method to select suitable ILs.…”

Section: Introductionmentioning

confidence: 99%

COSMO‐RS based ionic liquid screening for the separation of acetonitrile and ethanol azeotropic mixture

Zhang

et al. 2020

BACKGROUND The selection of competent entrainer is very important for separating azeotrope systems by extractive distillation. Ionic liquids (ILs) are outstanding entrainers due to their excellent properties. However, it is time‐consuming to choose suitable ILs from the huge database of anions and cations. Herein, the selectivity and viscosity of ILs were combined as double standards to select suitable ILs for the separation of acetonitrile and ethanol mixture. RESULTS The selectivity and viscosity of 450 ILs (25 cations and 18 anions) were predicted based on Conductor‐like Screening Model for Real Solvents (COSMO‐RS). 1‐Butyl‐3‐methylimidazolium acetate [BMIM][Ac] was selected as a potential entrainer due to its higher selectivity and lower viscosity and [BMIM][Cl] was chosen as a comparison item as ILs with [Cl]− anion have separation performance next to [Ac]−‐based ILs. The vapor–liquid equilibrium (VLE) data of the acetonitrile + ethanol + ILs systems were determined at 101.3 kPa and correlated with the non‐random two‐liquid (NRTL) model. The result showed that the addition of the two ILs produced a salting‐out effect on acetonitrile and enhanced the relative volatility of acetonitrile to ethanol. Furthermore, [BMIM][Ac] exhibited better separation performance than [BMIM][Cl] and our previous reported ILs, which are consistent with the predicted results. The reduced density gradient (RDG) method indicated that hydrogen bonding dominated the interactions between ethanol and IL. CONCLUSION [BMIM][Ac] is a superior entrainer for the separation of acetonitrile–ethanol azeotrope. Compared to the previously studied ILs, there is a stronger hydrogen bond between ethanol and [BMIM][Ac]. This makes ethanol ‘bundled’ and acetonitrile more volatile, resulting in the superior separation performance of [BMIM][Ac]. © 2019 Society of Chemical Industry

“…Currently, special distillations such as extractive distillation (ED), heterogeneous azeotropic distillation (HAD), pressure‐swing distillation (PSD) and reactive distillation (RD) are adopted to separate such azeotropes. Arifin et al .…”

Section: Introductionmentioning

confidence: 99%

Thermal coupled extractive distillation sequences with three entrainers for the separation of azeotrope isopropyl alcohol + diisopropyl ether

Zhang

Gao

et al. 2020

BACKGROUND During the synthesis of isopropyl alcohol (IPA) by hydration of propylene, diisopropyl ether (DIPE) is usually produced as a by‐product. Because IPA and DIPE can form a binary homogeneous azeotrope with the minimum boiling temperature at atmospheric pressure, it is difficult to separate the binary mixture by simple distillation. RESULT For separating the azeotrope IPA + DIPE, side‐stream extractive distillation column (SSED) and extractive dividing wall column (EDWC) processes with three entrainers [2‐methoxyethanol (2‐MEA), 2‐ethoxyethanol and propylene glycol ethyl ether (PGEE)] were simulated and optimized based on the minimal total annual cost (TAC). Moreover, CO2 emissions of the six sequences were calculated and the impact on the environment evaluated. CONCLUSIONS The sequence of SSED with PGEE as entrainer can reduce TAC by ≤34.48%, but EDWC with PGEE can offer TAC reduction of ≤52.46%. The results demonstrate that the EDWC sequence with PGEE as entrainer is favourable for separating the binary azeotrope IPA + DIPE. © 2020 Society of Chemical Industry