A Priori Prediction of Dissociation Phenomena and Phase Behaviors of Ionic Liquids

Insight into the inhibitory mechanism of soluble ionic liquids on the transport of TiO2 nanoparticles in saturated porous media: Roles of alkyl chain lengths and counteranion types

Column experiments were carried out to investigate the transport of TiO₂ nanoparticles (nTiO₂) in water-saturated porous media in the presence of various imidazolium-based ionic liquids (ILs) with different alkyl chain lengths and counteranions. The results indicated that the effects of ILs on nTiO₂ transport were considerably dependent upon IL species. In general, the transport-inhibition effects increased with the increasing length of branched alkyl chain on the ILs (i.e., [C₆mim]Cl > [C₄mim]Cl > [C₂mim]Cl). The trend was dominated by the hydrophobicity effects of ILs. Meanwhile, the inhibitory effects of ILs were strongly related to the counteranions and followed the order of [C₄mim]Cl > [C₄mim][TOS] > [C₄mim][PF₆], mainly due to different electrostatic repulsion force between nanoparticles and porous media in the presence of various ILs. Furthermore, the inhibitory role of [C₄mim][TOS] in nTiO₂ transport under acidic conditions (i.e., pH 6.5) was greater than that under alkaline conditions (i.e., pH 8.0). The dominant mechanism was that the differences in the extent of electrostatic repulsion between sand grains and nTiO₂ with or without ILs at pH 6.5 were larger than that at pH 8.0. Moreover, two-site kinetic retention model and DLVO theory provided good descriptions for the transport behaviors of nTiO₂ with different ILs.

A priori prediction of complex liquid-liquid-liquid equilibria in organic systems using a continuum solvation model

Liquid-liquid-liquid equilibria (LLLE) is usually observed in many industrial processes primarily linked to enhanced oil recovery techniques. However their measurements are complex and so are their computations. An inherently predictive tool is often useful for elucidating their distribution ratios and phase compositions. In the present work, the phase behavior of nine ternary and two quaternary LLLE systems were predicted employing the quantum chemical based COnductor like Screening MOdel-Segment Activity Coefficient (COSMO-SAC) model. The methodology namely, Rachford-Rice LLLE (RRL3E) algorithm and Henley-Rosen LLLE (HRL3E) algorithm were used to predict the triphasic compositions in each system. In the RRL3E approach, the triphasic systems were assumed into two co-existing biphasic liquid-liquid equilibria systems, whereas in the HRL3E approach, all three phases were considered to be in equilibrium with each other simultaneously. Apart from predicting the local compositions, the HRL3E algorithm was also used to predict the individual phase splits and phase fractions of the LLLE region. Average overall root mean square deviation (rmsd (%)) values considering all 42 datasets and corresponding to 414 data points were recorded as 4.65% and 4.83% using the RRL3E and HRL3E algorithms respectively. Further, the RRL3E algorithm was extended to correlate the LLLE data for all systems using the Genetic Algorithm (GA) based NRTL (GA-NRTL) and UNIQUAC (GA-UNIQUAC) models.

A Benchmark Open-Source Implementation of COSMO-SAC

The COSMO-SAC modeling approach has found wide application in science as well as in a range of industries due to its good predictive capabilities. While other models for liquid phases, as for example UNIFAC, are in general more accurate than COSMO-SAC, these models typically contain many adjustable parameters and can be limited in their applicability. In contrast, the COSMO-SAC model only contains a few universal parameters and subdivides the molecular surface area into charged segments that interact with each other. In recent years, additional improvements to the construction of the sigma profiles and evaluation of activity coefficients have been made. In this work, we present a comprehensive description of how to postprocess the results of a COSMO calculation through to the evaluation of thermodynamic properties. We also assembled a large database of COSMO files, consisting of 2261 compounds, freely available to academic and noncommercial users. We especially focus on the documentation of the implementation and provide the optimized source code in C++, wrappers in Python, and sample sigma profiles calculated from each approach, as well as tests and validation results. The misunderstandings in the literature relating to COSMO-SAC are described and corrected. The computational efficiency of the implementation is demonstrated.

Green chemical engineering in China

In China, the rapid development greatly promotes the national economic power and living standard but also inevitably brings a series of environmental problems. In order to resolve these problems fundamentally, Chinese scientists have been undertaking research in the area of green chemical engineering (GCE) for many years and achieved great progresses. In this paper, we reviewed the research progresses related to GCE in China and screened four typical topics related to the Chinese resources characteristics and environmental requirements, i.e. ionic liquids and their applications, biomass utilization and bio-based materials/products, green solvent-mediated extraction technologies, and cold plasmas for coal conversion. Afterwards, the perspectives and development tendencies of GCE were proposed, and the challenges which will be faced while developing available industrial technologies in China were mentioned.

Concentration Dependence of Ion Pairing in Imidazolium-Based Ionic Liquid Solutions

Infrared vibrational spectroscopy was used to probe concentration-dependent ion pair dissociation of imidazolium-based ionic liquids with three different halide anions (I^- , Br^- , and Cl^- ) in deuterated chloroform. Dissociation of the ion pairs at low concentrations of ionic liquids was found to be the easiest for ionic liquid with Cl^- anion, the most electronegative anion among the three investigated. This anomalous trend of ion pair dissociation was explained in terms of varying interaction strength between the solvent (CDCl₃ ) and the anions investigated.

Explicit consideration of spatial hydrogen bonding direction for activity coefficient prediction based on implicit solvation calculations

Directional hydrogen bonding is introduced to implicit solvation calculations for improved prediction of solvation properties and phase equilibria of associating fluids.