Recent Advances of Pervaporation Separation in DMF/H2O Solutions: A Review

N,N-dimethylformamide (DMF) is a commonly-used solvent in industry and pharmaceutics for extracting acetylene and fabricating polyacrylonitrile fibers. It is also a starting material for a variety of intermediates such as esters, pyrimidines or chlordimeforms. However, after being used, DMF can be form 5–25% spent liquors (mass fraction) that are difficult to recycle with distillation. From the point of view of energy-efficiency and environment-friendliness, an emergent separation technology, pervaporation, is broadly applied in separation of azeotropic mixtures and organic–organic mixtures, dehydration of aqueous–organic mixtures and removal of trace volatile organic compounds from aqueous solutions. Since the advances in membrane technologies to separate N,N-dimethylformamide solutions have been rarely reviewed before, hence this review mainly discusses the research progress about various membranes in separating N,N-dimethylformamide aqueous solutions. The current state of available membranes in industry and academia, and their potential advantages, limitations and applications are also reviewed.

Evaluation of the possibility of separating commercial phenol from the phenolic fraction of coal tar

This article is about the possibility of concentrating commercial coal phenol with a concentration of 99% by the weight method of rectification from the phenolic fraction of coal tar. The sufficiency of phenol is ensured by the kumol method, however, the consumption of phenol increases. Modeling of the vapor-liquid equilibrium of double and triple mixtures of components using the NRTL model showed the presence of the following positive homogeneous azeotropic mixtures: phenol-indane, phenol-indene. Modeling of the vapor-liquid equilibrium of double and triple mixtures of components using the NRTL model showed the presence of the following positive homogeneous azeotropic mixtures: phenol-indane, phenol-indene. The compositions and temperatures of these azeotropes are determined. The authors propose the isolation of phenol from the fraction and its purification from indane and indene by a clear rectification method. The technological scheme consisting of four devices is based on the analysis of the component composition of the initial mixture and the existing azeotropes. Modeling of the technological scheme showed that this scheme provides the release of phenol by 99% of the mass, which meets the requirements for coal phenol. After optimizing the technological parameters of the distillation columns, the estimated extraction costs will amount to 5.64 Gcal per ton of commercial phenol.

FORMATION OF AZEOTROPIC MIXTURES OF N-METHYLPYRROLIDONE WITH HYDROCARBONS

Using the limiting activity coefficients of the components of binary systems of N-methylpyrrolidone with n-alkanes and the conditions for the formation of azeotropes, it is found that N-methylpyrrolidone forms azeotropic mixtures with n-alkanes С9 - С 15, with alkylbenzenes С 10 - С 12 and with naphthalene. The formation of azeotropes with saturated hydrocarbons with a boiling point of 230-270 ° C must be taken into account when developing a technological scheme for the N-methylpyrrolidone regeneration unit, and also not to use this extractant for extraction purification of raw materials with a boiling point below 230 ° C

Fabrication and characterization of polyamide thin-film composite membrane via interfacial polycondensation for pervaporation separation of salt and arsenic from water

Pervaporation, mainly utilized to separate azeotropic mixtures, has been paid much attention for desalination in recent years due to its numerous advantages.

New structure-based models for the prediction of normal boiling point temperature of ternary azeotropes

Recently, development of the QSPR models for mixtures has received much attention. The QSPR modeling of mixtures requires the use of appropriate mixture descriptors. In this study, 12 mathematical equations were considered to compute mixture descriptors from the individual components for the prediction of normal boiling points of 78 ternary azeotropic mixtures. Multiple linear regression (MLR) was employed to build all QSPR models. Memorized_ACO algorithm was employed for subset variable selection. An ensemble model was also constructed using averaging strategy to improve the predictability of the final QSAR model. The models have been validated by a test set comprised of 24 ternary azeotropes and by different statistical tests. The resulted ensemble QSPR model had R2training, R2test, and q2 of 0.97, 0.95, and 0.96, respectively. Mean absolute error (MAE) as a good indicator of model performance were found to be 3.06 and 3.52 for training and testing sets, respectively.

Energy and Thermal Conductivity Assessment of Dimethyl-Ether and its Azeotropic Mixtures as Alternative Low Global Warming Potential Refrigerants in a Refrigeration System

Substituting Hydrofluorocarbons with natural refrigerants in domestic refrigerators will significantly reduce the direct contributions of fluorinated gases to global warming which will be of great environmental benefit. In this study, the performances of dimethyl-ether (RE170) and its azeotropic mixtures (R510A and R511A) in a refrigeration system were assessed theoretically and compare with that of conventional refrigerant. The study revealed that the three investigated alternative refrigerants exhibited significantly good heat transfer characteristics, low pressure ratio, high latent heat in the liquid phase which resulted in their high thermal conductivity and Volumetric Cooling Capacity (VCC). The thermal conductivity of the refrigerants reduces while the evaporating temperature rises and the value obtained for RE170 was the highest among the four refrigerants studied. The Coefficient of Performance (COP) for RE170, R510A and R511A were higher than that of R134a by 6.20, 10.06 and 3.02 % respectively while their power consumptions per ton of refrigeration were lower than that of R134a by 6.99, 11.04 and 1.47 % respectively. In conclusion, dimethyl-ether and its azeotropic mixtures performed better than R134a in that they have higher thermal conductivity, refrigerating effect, VCC, COP, lower power consumption per ton of refrigeration and hence, they can be considered as suitable replacements for R134a in domestic refrigerator.

Alcohol Dehydration by Extractive Distillation with Use of Aminoethers of Boric Acid

Aminoethers of boric acid (AEBA) were studied as potential extractants for the separation of aqueous–alcoholic azeotropic mixtures by extractive distillation. The conditions of vapor–liquid equilibrium in aqueous solutions of ethanol and isopropanol in the presence of AEBA were studied. The division of AEBA molecules into group components was proposed, and previously unknown geometric parameters of the boron group and the energetic pair parameters of the boron group with the alkane group, ether group, amine-3d group, and alcohol group were determined within the framework of the Universal Functional Group Activity Coefficient (UNIFAC) model. The modeling of the extractive rectification process of an ethanol–water mixture with AEBA as extractant has been carried out. The dependences of the cost function on the extractant flow rate, the residual water content in it and the number of theoretical trays were obtained. A technological scheme for ethanol dehydration has been proposed, and its technological characteristics have been calculated.