Modelling of Liquid-Liquid Equilibria Using NRTL and UNIFAC Equations in the Extraction of Bio-Oil-Based Phenolics Produced from the Pyrolysis of Sugarcane Bagasse

An exploration on renewable energy resources has been paid more attention due to the depletion of the fossil-based energy resource. In addition, their safe and environmentally friendly properties have attracted experts’ interest. One of the renewable energy resources is the bio-oil produced from sugarcane bagasse. The bio-oil was produced through a pyrolysis at 500°C. However, the produced bio-oil showed a high content of phenolics, c.a. 40-60%. A liquid-liquid extraction to remove the phenolics using methanol-chloroform solvents would be beneficial to improve the stability of the bio-oil as well as to obtain high purity phenolics. Modelling of the liquid-liquid equilibria in the extraction was then developed using NRTL and UNIFAC equations. The empirical quantitative data of phase equilibrium system were calculated on both the extract and raffinate phases. The lowest RMSD value of 0.043160 was obtained from the calculations using NRTL equation at an extraction temperature of 50°C. Thus, the most suitable model was achieved using NRTL equation.

Determination of chlorzoxazone crystal growth kinetics and size distribution under controlled supersaturation at 293.15 K

Background: Chlorzoxazone (CHZ) is a water-insoluble drug having bioavailability problems. The absorption rate of such drugs can be improved by reducing their particle size. In this work, the crystal growth kinetics of CHZ–ethanol for different degrees of supersaturation (SS) has been studied. Method: The equilibrium solubility data of CHZ in ethanol is determined by the shake-flask method within the 283.15–313.15 K temperature range. The mole fraction solubility of CHZ is calculated and correlated with the modified Apelblat equation, λh equation, van’t Hoff equation, Wilson, and non-random two liquid (NRTL) equation. Batch crystallization experiments are performed on three different degrees of SS-1.16, 1.18, and 1.20 at 293.15 K as a function of time. Results: The maximum root mean square difference (RMSD) and relative average deviation (RAD) values of 169.24 x10-6 and 0.699 x10-2, respectively, are observed in the NRTL equation model. The dissolution properties such as standard enthalpy, standard entropy, and Gibbs free energy are predicted using van’t Hoff equation. Using a simple integral technique, the average crystal growth rate constant KG is calculated as 1.58 (μm/min) (mg/ml)-1 and the order n=1 for CHZ–ethanol at 293.15 K. Conclusion: The obtained result concludes that the crystals growth size is found to be varied at different SS ratio in batch crystallization. The particle size control in batch crystallization can be achieved by optimizing the operating conditions to get the desired size crystals.

Effect of Cation Structure in Quinolinium-Based Ionic Liquids on the Solubility in Aromatic Sulfur Compounds or Heptane: Thermodynamic Study on Phase Diagrams

Experimental and theoretical studies on thermodynamic properties of quinolinium-based ionic liquids (ILs) based on bis(trifluoromethylsulfonyl)imide anion (namely N-butyl-quinoloinium bis(trifluoromethylsulfonyl)imide, [BQuin][NTf2], N-hexylquinoloinium bis(trifluoromethyl-sulfonyl)imide, [HQuin][NTf2], and N-octylquinoloinium bis(trifluoromethyl-sulfonyl)imide, [OQuin][NTf2]) with aromatic sulfur compounds and heptane, as a model compound of fuel were examined in order to assess the applicability of the studied ionic liquids for desulfurization of fuels. With this aim, the temperature-composition phase diagrams of 13 binary mixtures composed of organic sulfur compounds (thiophene, benzothiophene, or 2-methylthiophene) or heptane and ionic liquid (IL) were investigated at ambient pressure. A dynamic method was used to determine the (solid–liquid) equilibrium phase diagrams in binary systems over a wide composition range and temperature range from T = 255.15 to 365.15 K up to the fusion temperature of ILs. The immiscibility gap with an upper critical solution temperature (UCST) was observed for each binary system under study. The influence of the alkane chain length of the substituent on the IL cation and of the sulfur compounds (the aromaticity of the solvent) was described. The experimental (solid + liquid) phase equilibrium dataset were successfully correlated using the well-known NRTL equation.

Liquid-Liquid Extraction in Systems Containing Butanol and Ionic Liquids – A Review

Room-temperature ionic liquids (RTILs) are a moderately new class of liquid substances that are characterized by a great variety of possible anion-cation combinations giving each of them different properties. For this reason, they have been termed as designer solvents and, as such, they are particularly promising for liquid-liquid extraction, which has been quite intensely studied over the last decade. This paper concentrates on the recent liquid-liquid extraction studies involving ionic liquids, yet focusing strictly on the separation of n-butanol from model aqueous solutions. Such research is undertaken mainly with the intention of facilitating biological butanol production, which is usually carried out through the ABE fermentation process. So far, various sorts of RTILs have been tested for this purpose while mostly ternary liquid-liquid systems have been investigated. The industrial design of liquid-liquid extraction requires prior knowledge of the state of thermodynamic equilibrium and its relation to the process parameters. Such knowledge can be obtained by performing a series of extraction experiments and employing a certain mathematical model to approximate the equilibrium. There are at least a few models available but this paper concentrates primarily on the NRTL equation, which has proven to be one of the most accurate tools for correlating experimental equilibrium data. Thus, all the presented studies have been selected based on the accepted modeling method. The reader is also shown how the NRTL equation can be used to model liquid-liquid systems containing more than three components as it has been the authors’ recent area of expertise.

Simulation of N-Propanol Dehydration Process Via Heterogeneous Azeotropic Distillation Using the NRTL Equation

Numerical values of the NRTL equation parameters for calculation of the vapour - liquid - liquid equilibria (VLLE) at atmospheric pressures have been presented for 5 ternary mixtures. These values were fitted to the experimental VLLE and vapour - liquid equilibrium (VLE) data to describe simultaneously, as accurately as possible, the VLE and the liquid - liquid equilibria (LLE). The coefficients of this model called further NRTL-VLL were used for simulations of n-propanol dehydration via heterogeneous azeotropic distillation. The calculations performed by a ChemCAD simulator were done for 4 mixtures using hydrocarbons, ether and ester as an entrainer. In majority simulations the top streams of the azeotropic column had composition and temperature similar to the corresponding experimental values of ternary azeotropes. The agreement between the concentrations of both liquid phases formed in a decanter and the experimental values of the LLE was good for all four simulations. The energy requirements were the most advantageous for the simulation with di-npropyl ether (DNPE) and isooctane. Simulations were performed also for one mixture using the NRTL equation coefficients taken from the ChemCAD database. In that case the compositions of the liquid organic phases leaving the decanter differed significantly from the experimental LLE data.

Flash point of organic binary mixtures containing alcohols: experiment and prediction

The flash points of three organic binary mixtures containing alcohols were measured in the present work. The experimental data was obtained using the Pensky-Martens closed cup tester. The experimental data were compared with the values calculated by the Liaw model. Activity coefficients were calculated by the Wilson equation and NRTL equation. The accuracy of predicted flash point values is dependent on the thermodynamic model used for activity coefficient.

Design calculations of an extractor for aromatic and aliphatic hydrocarbons separation using ionic liquids

The study concentrates on the separation of aromatic hydrocarbons from aliphatic hydrocarbon mixtures using ionic liquids as a new alternative of extraction solvents. Influence of the phase equilibrium description accuracy on the separation equipment design using different thermodynamic models was investigated. As a model system, a heptane-toluene binary mixture was chosen, employing 1-ethyl-3-methylimidazolium ethyl sulfate (EMIES) ionic liquid as an extractive solvent. Liquid-liquid equilibrium (LLE) data of the ternary system were calculated using NRTL equations with different quality model parameters. Model 1 corresponds to the NRTL equation with the original binary parameters evaluated independently from the respective binary equilibrium data. Model 2 is represented by an NRTL equation extended by the ternary correction term (with the original binary parameters and ternary correction term parameters evaluated from the ternary tie-lines). Model 3, i.e. the NRTL equation with binary model parameters determined via ternary LLE data regression using ASPEN Plus, was taken from Meindersma et al. (2006). Continuous-flow liquidphase extraction was simulated considering a cascade of mixer-settler type extractors according to the Hunter-Nash scheme (Hunter & Nash, 1934). Based on the simulation results, for a preset separation efficiency criterium, different accuracies of the equilibrium description caused serious discrepancies in the separation equipment design, e.g. in the number of theoretical stages, solvent to feed ratio, and product purity.

Calculation of vapour - liquid - liquid – equilibria in quaternary systems

A method of parameters fitting to the experimental vapour - liquid - liquid equilibrium (VLLE) data is presented for the NRTL and the Uniquac equations for six quaternary mixtures. The same equations but with coefficients taken from the simulator Chemcad database were also used for calculation of the VLLE for the same mixtures. The calculated equilibrium temperatures and compositions for all the three phases were compared with the experimental data for these four cases. The investigated models were also applied for calculation of the compositions and temperatures of ternary azeotropes occurring in the considered quaternary mixtures. The computed values were compared with the experimental ones to appreciate the model's accuracy and to confirm whether the model correctly predicts the presence of homo- or heteroazeotrope. The NRTL equation with coefficients fitted to the VLLE data proved to be the most accurate model. For the mixtures containing water, ethanol and two different hydrocarbons this model shows particularly high accuracy. In three cases the mean deviations between the calculated and measured temperatures do not exceed 0.25 K, and for the fourth mixture the difference equals 0.33. Besides, the mean deviations between the calculated and the measured concentrations in the gas and liquid phases, with one exception do not exceed 1 mole %.