Measurement and prediction of isothermal vapor–liquid equilibrium of a-pinene+camphene/longifolene+abietic acid+palustric acid+neoabietic acid systems

The vapor–liquid equilibrium(VLE)data of a-pinene+camphene+[abietic acid+palustric acid+neoabietic acid]and a-pinene+longifolene+[abietic acid+palustric acid+neoabietic acid]systems at 313.15 K,333.15 K and 358.15 K were measured by headspace gas chromatography(HSGC).These data was compared with the predictions value by conductor-like screening model for realistic solvation(COSMO-RS).Moreover,the calculated data of COSMO-RS and Non-Random Two-Liquids(NRTL)models showed good agreement with the experimental data.It was found that the three resin acids inhibited the volatility of a-pinene,camphene and longifolene and resulted in the decrease of total pressure.Moreover,HE(HB)contributes the most to the excess enthalpy and the hydrogen bonding interaction is the dominant intermolecular force of a-pinene,camphene and longifolene with the three resin acids.In addition,the geometric structures optimization and binding energy were obtained by the DFT to further illustrate the hydrogen bonding interaction and the effects of the addition of the three resin acids on the isothermal VLE.

Application of vacuum distillation in refining crude indium

Vacuum distillation is a technique suitable for low boiling and melting point materials,to remove the heavy and low vapor pressure impurities at low level.As indium has low melting point and high boiling point,it is suitable for refining by vacuum distillation.First,saturation vapor pressure for major elements in crude indium was calculated by the Clausius–Clay Prang equation,which could approximately predict the temperature and pressure during vacuum distillation process.Second,the activity coefficients for In–Cd,In–Zn,In–Pb,In–Tl at 1373 K,and In–Sn at 1573 K were acquired by means of molecular interaction on volume model.Vapor–liquid equilibrium composition diagrams of those above systems in crude indium were drawn based on activity coefficients.These diagrams could estimate the compositions of products in each process during the refinement of crude indium.Finally,1.2–1.6 ton crude indium was used per day when vacuum distillation experiments were carried out,and experimental results are in good agreement with the predicted values of the vapor–liquid equilibrium composition diagrams.

Determination and correlation solubility of 4-nitroimidazole in twelve pure solvents from 278.15 K to 323.15 K

In this paper,the solubility of 4-nitroimidazole in twelve pure solvents(toluene,benzene,1,4-dioxane,acetonitrile,ethyl acetate,acetone,GBL,ethanol,methanol,n-butanol,DMF and NMP)were determined by using the laser monitoring system from 278.15 K to 323.15 K under 101.1 k Pa,which are 0.00018–0.00070,0.00021–0.00073,0.00034–0.00092,0.00038–0.00142,0.00047–0.00120,0.00126–0.00303,0.00225–0.00517,0.00310–0.00724,0.00467–0.00982,0.00453–0.01940,0.01947–0.04652,and 0.04670–0.07452,respectively.At constant temperature,the mole fraction solubility of 4-nitroimidazole were increased as the following order:toluene<benzene<1,4-dioxane<(ethyl acetate or acetonitrile)<acetone<GBL<ethanol<(methanol or nbutanol)<DMF<NMP,and the solubility of 4-nitroimidazole in(ethyl acetate,acetonitrile)and(methanol,n-butanol)had an intersection point at 297.55 K and 281.85 K,respectively.The solubility of 4-nitroimidazole could be increased with increasing temperature in twelve pure solvents.The ideal model,modified Apelblat equation,polynomial empirical equation,andλh equation were used to correlate the experimental values.The experimental solubility values were employed to calculate the standard dissolution enthalpy,standard dissolution entropy and Gibbs energy.The dissolution of 4-nitroimidazole could be an endothermic process in twelve pure solvents.The determination and fitting solubility of 4-nitroimidazole have important guiding significance for the purification and crystallization of its preparation process.

Separation of n-heptane and tert-butanol by ionic liquids based on COSMO-SAC model

In the process of liquid-liquid extraction,it is necessary to look for green solvents as extractants.Ionic liquids have been studied as extractants due to their green recyclability in recent years.The infinite dilution activity coefficients of 100 ionic liquids with a combination of 10 cations and 10 anions were calculated by COSMO-SAC model,and theσ-profiles were plotted.The distribution coefficient and separation coefficient of n-heptane+tert-butanol+ILs were determined.[OMIM][OTF],[HMIM][OTF]and[BMIM][OTF]were selected as solvents for this study.The interaction energy,bond length and charge density of ionic liquids with tert-butanol were calculated by quantum chemistry calculation method.According to these results,the rationality of selected ionic liquids as extractants could be analyzed from the molecular level.At 298.15 K and 101.325 kPa,the liquid-liquid equilibrium data of the ternary system{n-heptane+tert-butanol+[OMIM][OTF],nheptane+tert-butanol+[BMIM][OTF],n-heptane+tert-butanol+[HMIM][OTF]}were measured.The distribution coefficient and separation coefficient for judging the extraction effect were obtained.The NRTL model was used to correlate liquid-liquid equilibrium experimental data,and correlation result proved that the correlated and experimental data had a good correlation.The research on ionic liquids is of great significance to the development of green and sustainable chemical industry.

A New Excess Free Energy Mixing Rule for Representing Vapor-Liquid Equilibria of Mixed Refrigerants

A suitable mixing rule is important for vapor liquid equilibrium(VLE)investigations for mixed refrigerants.In this work,a new excess free energy mixing rule(MRv)was proposed at zero pressure based on the linear relationship between dimensionless parameter 1/(u-1)and a.MRv mixing rule was explicit adopted variable liquid molar volume.The applicable temperature range of MRv could be extended by means of an empirical method to estimate the liquid molar volume for components at high temperatures.Three mixing rules modified Huron-Vidal mixing rule(MHV1),Wong-Sandler mixing rule(WS),and MRv at two reference pressures were used to compare the VLE data in the calculation of 37 mixed refrigerants.Results demonstrated that MRv had a relatively similar accuracy to MHV1 and WS for component and pressure calculation.Moreover,the average excess Gibbs free energy using the MRv mixing rule for the 37 selected mixed refrigerants(0.0013)was much lower than those using the MHV1(0.0078)and WS(0.0809)mixing rules,which was very valuable for the design and optimization of thermodynamic systems using mixed refrigerants.

Development of mobile miniature natural gas liquefiers

With increasing consumption of natural gas(NG),small NG reservoirs,such as coalbed methane and oil field associated gas,have recently drawn significant attention.Owing to their special characteristics(e.g.,scattered distribution and small output),small-scale NG liquefiers are highly required.Similarly,the mixed refrigerant cycle(MRC)is suitable for small-scale liquefaction systems due to its moderate complexity and power consumption.In consideration of the above,this paper reviews the development of mobile miniature NG liquefiers in Technical Institute of Physics and Chemistry(TIPC),China.To effectively liquefy the scattered NG and overcome the drawbacks of existing technologies,three main improvements,i.e.,low-pressure MRC process driven by oil-lubricated screw compressor,compact cold box with the new designed heat exchangers,and standardized equipment manufacturing and integrated process technology have been made.The development pattern of"rapid cluster application and flexible liquefaction center"has been eventually proposed.The small-scale NG liquefier developed by TIPC has reached a minimum liquefaction power consumption of about 0.35 kW.h/Nm^(3).It is suitable to exploit small remote gas reserves which can also be used in boil-off gas reliquefaction and distributed peak-shaving of pipe networks.