Extraction mechanism analysis and energy saving enhancement of extraction separation of methyl tert-butyl ether and methanol by ionic liquid based on molecular dynamics simulation

Process Simulation and Optimization on Ionic Liquids

Ionic liquids (ILs) are promising alternative compounds that enable the development of technologies based on their unique properties as solvents or catalysts. These technologies require integrated product and process designs to select ILs with optimal process performances at an industrial scale to promote cost-effective and sustainable technologies. The digital era and multiscale research methodologies have changed the paradigm from experiment-oriented to hybrid experimental-computational developments guided by process engineering. This Review summarizes the relevant contributions (>300 research papers) of process simulations to advance IL-based technology developments by guiding experimental research efforts and enhancing industrial transferability. Robust simulation methodologies, mostly based on predictive COSMO-SAC/RS and UNIFAC models in Aspen Plus software, were applied to analyze key IL applications: physical and chemical CO2 capture, CO2 conversion, gas separation, liquid-liquid extraction, extractive distillation, refrigeration cycles, and biorefinery. The contributions concern the IL selection criteria, operational unit design, equipment sizing, technoeconomic and environmental analyses, and process optimization to promote the competitiveness of the proposed IL-based technologies. Process simulation revealed that multiscale research strategies enable advancement in the technological development of IL applications by focusing research efforts to overcome the limitations and exploit the excellent properties of ILs.

Analysis of the microscopic interactions between processed Polygonatum cyrtonema polysaccharides and water

The dissolution and microscopic interactions of processed Polygonatum cyrtonema polysaccharides in water are extremely important because they strongly influence the process to extract these polysaccharides from water. In this paper, molecular dynamics simulation methods were used to analyse the influence of extraction temperature, concentration and molecular weight on the radial distribution function (RDF), mean square displacement (MSD), diffusion coefficient (D), radius of gyration (R_g), and microstructure of processed Polygonatum cyrtonema polysaccharides in water as well as the intrinsic viscosity (η), hydrogen bond characteristics and microscopic interactions in the solutions. The research results showed that the extraction temperature, concentration and molecular weight of the polysaccharides had important effects on the RDF, MSD, D, R_g, η, hydrogen bond characteristics and the microstructure of the polysaccharide molecules, but there were some major differences. The order of the influence of the factors affecting the dissolution of polysaccharides in water was temperature > concentration > molecular weight. Extraction temperature, material fluid ratio and molecular weight had greater influence on the fluidity and dissolution state of the polysaccharides in water. As the solute concentration and molecular weight increased, hydrogen bonds between polysaccharides and water inhibited their dissolution and diffusion. Properly increasing the temperature, reducing the concentration and selecting low molecular weight polysaccharides enhanced the dissolution and diffusion of the polysaccharides in the solution system. Molecular weight was the main factor affecting the η of the polysaccharide solutions. These results can provide theoretical guidance for the extraction or tea brewing process of Polygonatum cyrtonema polysaccharides in future work.

Binary Mixtures of Imidazolium-Based Protic Ionic Liquids. Extended Temperature Range of the Liquid State Keeping High Ionic Conductivities

Binary mixtures based on the two protic ionic liquids 1-ethylimidazolium triflate ([C2HIm][TfO]) and 1-ethylimidazolium bis(trifluoromethanesulfonyl)imide ([C2HIm][TFSI]) have been investigated, with focus on phase behavior, ionic conductivity, and intermolecular interactions as a function of composition (χTFSI indicating the mole fraction of the added compound). It is found that on addition of [C2HIm][TFSI] to [C2HIm][TfO], the melting temperature is first decreased (0 <χ≤ 0.3) and then suppressed (0.3 <χ≤ 0.8) resulting in mixtures with no phase transitions. These mixtures display a wide temperature range of the liquid state and should be interesting for use in devices operating at extreme temperatures. The ionic conductivity does not vary significantly across the composition range analyzed, as evidenced in the comparative Arrhenius plot. The activation energy, Ea, estimated by fitting with the Arrhenius relation in a limited temperature range (between 60 and 140 °C) varies marginally and keeps values between 0.17 and 0.21 eV. These marginal differences can be rationalized by the initially very similar values of the two neat protic ionic liquids. Vibrational spectroscopy, including both Raman and infrared spectroscopies, reveals weakening of the cation–anion interactions for increasing content of [C2HIm][TFSI], which is reflected by the blue shift of the average N-H stretching mode and the red shift of the S-O stretching mode in the TfO anion. These trends correlate with the higher disorder in the mixtures observed by DSC and are evidenced by the decrease and suppression of the melting temperature as the amount of [C2HIm][TFSI] is increased.