AN IMPROVED PENG-ROBINSON EQUATION OF STATE WITH A NEW TEMPERATURE DEPENDENT ATTRACTIVE TERM

An improved form of the Peng-Robinson cubic equation of state has been proposed. The temperature dependence of the attractive term has been modified so as to accurately represent vapor pressures of several fluids with large acentric factors from triple point to close to the critical point. The prediction of saturated liquid volume is also improved by introducing volume translation term in the equation of state. Comparisons of theoretical results with experimental data are made for the vapor/liquid phase equilibria of 44 pure fluids including nonpolar, polar and associating fluids. Our results show that the modified Peng-Robinson equation of state can represent accurately saturated vapor pressures of the fluids investigated in this paper, and it is more accurate than the Peng-Robinson equation of state and its earlier modifications due to Stryjek and Vera (1986) and Twu et al. (1995rpar;. Incorporation of the volume translation term in the equation of state has been found to improve the accuracy of saturated liquid volume significantly.     

基团对应状态法(CSGC)用于纯物质饱和蒸气压的估算

将对应态原理与基团贡献法相结合,引入拟临界性质的概念,提出基团对应状态法(Correspounding State with Group Contribution,简称CSGC)。并将其与Riedel方程相结合用于饱和蒸气压的估算,提出新的蒸气压估算方程(CSGC-PR方程)。88种基团的参数由包括饱和烃、不饱和烃、环烃、芳烃、含氧化合物、含硫化合物、含氮化合物、含卤化合物等350种物质5255个饱和蒸气压实验数据关联获得。新模型的估算精度优于现有的对应状态法,不仅对于高碳数分子有良好的估算精度,并对非极性物质能较好地外推高压下的饱和蒸气压。     

Estimation of solid vapor pressures from supercritical CO2 + biomolecule systems using a PSO algorithm

A method to estimate the solid vapor pressures of biomolecules using a biologically deriver algorithm is presented. The solid vapor pressure is usually small for most solid compounds and in many cases available experimental techniques cannot be used to obtain accurate values. Therefore, estimation methods must be used to obtain these data. Five binary gas-solid phase systems of supercritical CO₂ + biomolecule containing caffeine, artemisinin, capsaicin, cholesterol, and β-carotene are considered in this study. Particle swarm optimization is used for minimize the difference between calculated and experimental solubility. Then, the solid vapor pressures of biomolecules are calculated from solubility data. The Peng-Robinson equation of state with the Wong-Sandler mixing rules are used to evaluate the fugacity coefficient on the systems. The results show that the method presented is reliable enough and can be used with confidence to estimate the solid vapor pressure of any organic biomolecule.     

Vapor pressures of heavy liquid hydrocarbons containing nitrogen or sulfur

The extended SWAP (Smith-Winnick-Abrams-Prausnitz) correlation for vapor pressure has been applied in the region 1300-266,000 Pa to a large number of hydrocarbon derivatives containing either nitrogen or sulffur as heteroatoms. With a minimum of experimental information including approximate characterization of molecular structure and one vapor pressure datum, vapor pressures can be estimated within ± 10%.     

Complete carbon analysis of sulfur‐containing mixtures using postcolumn reaction and flame ionization detection

Quantitative analysis of complex mixtures containing hundreds‐to‐thousands of organic compounds rich in heteroatoms, including oxygen, sulfur, and nitrogen, is a major challenge in the fuel, food, and chemical industries. In this work, a two‐stage (oxidation and methanation) catalytic process in a 3‐D–printed metal microreactor was evaluated for its capability to convert sulfur‐containing organic compounds to methane. The microreactor was inserted into a gas chromatograph between the capillary column and flame ionization detector. Catalytic conversion of all sulfur‐containing analytes to methane enabled carbon quantification without calibration, by the method identified as “quantitative carbon detection” or QCD. Quantification of tetrahydrothiophene, dimethyl sulfoxide, diethyl sulfide, and thiophene indicated complete conversion to methane at 450°C. Long‐term performance of a commercial microreactor was evaluated for 2000 consecutive injections of sulfur‐containing organic analytes. The sulfur processing capacity of the microreactor was identified experimentally, after which reduced conversion to methane was observed. © 2017 American Institute of Chemical Engineers AIChE J, 63: 5438–5444, 2017     

含FeCl_3光学戊醇和异戊醇蒸汽压的测定和关联

采用静态法,分别测定了质量分数在5.0%—9.6%范围中3种不同浓度FeCl3加入后光学戊醇和异戊醇在100—140℃范围内的饱和蒸汽压,发现随着盐质量分数的增大,2种戊醇的蒸汽压在相同温度下的降低有较明显差异。压力测量采用水银U型管压差计,误差为±0.07 kPa,温度测量采用精密温度计,误差为±0.01℃。实验结果进一步用Antoine方程进行了关联,得到Antoine方程的3个参数A,B,C,关联值与实验测定值吻合得很好(对于光学戊醇和异戊醇,其平均偏差均在1%以内)。这些数据的测得为今后进一步研究加盐精馏分离2种戊醇提供了基础物性数据。     

定位分布贡献方法估算有机物正常沸点

A new position group contribution model is proposed for the estimation of normal boiling data of organic compounds involving a carbon chain from C2 to C18. The characteristic of this method is the use of position distribution function. It could distinguish most of isomers that include cis- or trans-structure from organic com-pounds. Contributions for hydrocarbons and hydrocarbon derivatives containing oxygen, nitrogen, chlorine, bro-mine and sulfur, are given. Compared with the predictions, results made use of the most common existing group contribution methods, the overall average absolute difference of boiling point predictions of 417 organic com-pounds is 4.2 K; and the average absolute percent derivation is 1.0%, which is compared with 12.3 K and 3.2% with the method of Joback, 12.1 K and 3.1% with the method of Constantinou-Gani. This new position contribution groups method is not only much more accurate but also has the advantages of simplicity and stability.     

Solubilities of solids in supercritical fluids

The solubilities of several low-volatility compounds in supercritical fluids were measured. The fluids used were pure carbon dioxide or carbon dioxide modified with small amounts of organic liquids. Some enthalpies of solution of solids in carbon dioxide at a density of 0.80 g/mL are presented. The enthalpy of solution of fluoranthene in carbon dioxide was found to be less endothermic at higher CO₂ density. The order of solubilities in the modified fluids was the same as that in the pure liquid modifiers. The same apparatus was used to measure vapor pressures of some substances as well as solubilities.     

KINETICS OF OXYDESULFURIZATION OF MINSHALL, INDIANA COAL

The kinetics of the oxidation of pyritic sulfur, organic sulfur and carbon for the Minshall, Indiana coal was investigated. Experiments were conducted in a semi-batch manner. The experimental data were taken in the temperature range of 19O-23O°C, oxygen partial pressure range of 0.86-3.44 MPa and for the batch times up to 3600 s.

The rate of organic sulfur removal was observed to be second order with respect to sulfur and first order with respect to the partial pressure of oxygen, and this reaction was found to have an activation energy of 75,000 kJ/kg-mole. The pyritic sulfur removal was observed to be much more rapid, and the experimental data fitted the continuous reaction model with second order dependence on pyritic sulfur. However, the coal combustion loss in the case of this coal was relatively high, probably because of the presence of larger amounts of oxygen containing compounds, and this coal did not meet the EPA standards for the heating value losses.     

混合溶剂-盐体系的汽液平衡

以扰动理论为基础建立了含电解质混合溶剂体系的状态方程。用其计算了五个甲醇-水-盐体系的汽液平衡。参数由拟合蒸汽压、密度和离子平均活度系数数据获得。当应用到三元体系时(只用一个可调二元参数),状态方程预测蒸汽压的平均相对误差小于2.3％,汽相组成的平均绝对误差小于0.017。     

链状流体的分子热力学模型(Ⅰ)──纯物质

实际链状流体的分子热力学模型表示为参考流体（硬球链流体）的贡献与一微扰项之和.作者先前建立的硬球链流体的状态方程用于计算参考流体的性质,用Alder等人对方阱流体的计算机模拟结果计算微扰项的贡献,从而建立了实际链状纯流体的分子热力学模型.该模型具有非常简单的形式,用三个与温度无关的分子参数（分子的链数,链节的直径和链节间的方阱位能阱深）可以较好地关联从球形小分子到链状高分子、分子间没有氢键作用的流体的饱和蒸汽压、饱和液体体积和pVT关系     

Molecular thermodynamic model for fluids containing associated molecules

With the statistical mechanical theory for square-well-chain fluids as the basic princi-ples,a molecular thermodynamic model including expressions for the Helmholtz function and thecompressibility factor for associated square-well-chain fluids has been developed.Employment ofthe shield-sticky concept enables the corporation of association bonds between in the model.Good agreement with computer-simulation results for dimer-linear quadrimer systems is obtained.Satisfactory correlation for vapor pressures and saturated liquid volumes of pure substances con-taining associated molecules(such as carboxylic acids,alcohols,amines,water,etc.)with four mo-lecular parameters indicates the applicability of the model.     

THE APPLICATIONS OF A GENERALIZED EQUATION OF STATE TO THE CORRELATION AND PREDICTION OF PHASE EQUILIBRIA∗

Two methods of generalizing an equation of state are demonstrated and their limitations are outlined. One method involves the correlation of the equation of state constants and the second method involves a recently proposed Generalized Corresponding States Principle based on the properties of two (nonspherical) reference fluids. The PVT properties of pure fluids are represented by a new cubic equation of slate with four parameters which are obtained from vapor pressure and saturated liquid density data. It is demonstrated how a limited amount of data on key components may be used to obtain phase equilibria in mixtures.     

THE VAPOR-LIQUID EQUILIBRIUM OF ETHANOL-WATER MIXTURE IN THE PRESENCE OF BENZYLTRIETHYLAMMONIUM CHLORIDE SALT AT ATMOSPHERIC PRESSURE

The phase transfer catalysis reaction is gaining more and more attention in chemical industry. Usually, the chemicals used as phase transfer catalyst are organic salts. Unfortunately, the effect of an organic salt on the vapor-liquid equilibrium (VLE) of a mixture has hardly been reported in literature. In this study, the effect of the benzyltriethylammonium chloride organic salt on the VLE of ethanol-water mixture was obtained experimentally. It is observed that this organic salt can shift and even break away the azeotrope of ethanol -water mixture as an inorganic salt does. The experimental data were correlated with the models or Tan (1987, 1990) and Ohe (1991). The results were not satisfactory probably due to the complicated interactions among ions and molecules and the big different particle sizes or ion, solvent molecule, and salt molecule.

The vapor pressures of benzyltriethylammonium chloride-ethanol mixtures needed in this study for determining solvent-salt interaction parameters in the correlation model were also measured and regressed by the Patil model (1990).     

THE APPLICATIONS OF A GENERALIZED EQUATION OF STATE TO THE CORRELATION AND PREDICTION OF PHASE EQUILIBRIA*

Two methods of generalizing an equation of state are demonstrated and their limitations are outlined. One method involves the correlation of the equation of state constants and the second method involves a recently proposed Generalized Corresponding States Principle based on the properties of two (nonspherical) reference fluids. The PVT properties of pure fluids are represented by a new cubic equation of slate with four parameters which are obtained from vapor pressure and saturated liquid density data. It is demonstrated how a limited amount of data on key components may be used to obtain phase equilibria in mixtures.     

ANALYSIS OF GASES DISSOLVED IN GLASS AND GASES PRESENT IN SEEDS*

A method of analysis for gases dissolved in glass has been developed which gives more reproducible results than those previously reported. The problem of the volatilization of alkali from the sample during the course of analysis appears to have been satisfactorily solved through the use of an auxiliary furnace. A number of commercial glasses have been analyzed for dissolved gases. Water vapor, sulfur dioxide, and oxygen are the principal gases found in flint glass. Water vapor seems to be the principal constituent of the gases found in amber glass. A method for the analysis of gases present in seeds in glass has been developed which gives fairly satisfactory quantitative results on samples containing more than 1 cu. mm. of gas. The results obtained on samples containing less than 1 cu. mm. of gas are qualitative only. The procedure consists (1) in the determination of the temperatures at which gases present in the seeds undergo a change of state and (2) in the microchemical analysis of these same gases. Seeds have been found that contained entrapped air, sulfur dioxide, and also carbon dioxide. Some seeds, especially those in amber glass, appear to be vacuum seeds, and these frequently contain a deposit on the inside which has been identified as a sulfite or a sulfate.     

Use of velocity of sound in predicting thermodynamic properties of dense fluids from cubic equations of state

In this paper it has been shown that velocity of sound data may be used to obtain constants of a cubic equation of state and then thermodynamic properties can be accurately calculated through the constants extracted from sonic velocity data. Results are presented for estimation of heat capacities, enthalpies, vapor pressures and compressibility factors of some pure vapor and liquid compounds as well as some binary mixtures for pressures up to 100 MPa and temperatures up to 600 K for hydrocarbons from methane to hexadecane. The method will be useful for those mixtures containing heavy compounds for which accurate data on critical constants are not available, but for which the sonic velocity can be measured.     

七种有机物极微蒸气压数据的测定

建立了一套用Knudsen质量损失隙透法的极微蒸气压数据测定装置,用正十六烷作为标准物对设备进行了校验。测定了正十八烷、1-十八烯、邻苯二甲酸二乙酯、对苯二甲酸二甲酯、二异丙基萘、邻苯二甲酸二环己酯和芘在298～373K的极微蒸气压数据。并给出了各自的Antoine系数。     

A SEMI-EMPIRICAL CORRLATION OF EQUILIBRIUM PROPERTIES FOR NONSTOICHIOMETRIC TRANSITION METAL + SULFUR SYSTEMS

Transition metal sulfides have received much interest in their thermodynamic properties essential for understanding the nature of phase transformation. The order-disorder transformation of the vanadium + sulfur system has been studied by several investigators. However, its experimentally observed equilibrium properties cannot be adequately correlated.

In this paper, a statistical thermodynamic approach to the equilibrium properties of these nonstoichio-metric compounds was attempted by considering three kinds of interaction energies among various vacancy-vacancy and metal-vacancy pairs. Both composition- and temperature-dependences of the short-range interlayer interaction energy for metal-vacancy pairs were taken into account to fit the experimental data.

By applying the proposed semi-empirical model, equilibrium sulfur vapor pressures of the vanadium-sulfur system at seven temperatures, those of the niobium-sulfur system at four temperatures and those of the tantalum-sulfur system at three temperatures were calculated for a wide range of nonstoichiometric compositions. Results were compared to corresponding experimental data with good agreements.     

Determination of the vapor pressures of select polychlorinated dibenzo-p-dioxins and dibenzofurans at 75-275 °C

Vapor pressures were determined for several polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) at 75-275 °C, extending the available literature data to more relevant temperature regions and providing the first experimental data for 2,3,7-trichlorodibenzo-p-dioxin (2,3,7-TriCD). A modification of the effusion technique, based upon controlling the diffusion of the target compound and subsequent high resolution gas chromatography/low resolution mass spectrometry (HRGC/LRMS) analysis, was proven comparable to other accepted methods for determining the vapor pressures of semi-volatile organic compounds (SVOCs). Vapor pressures for octachlorodibenzo-p-dioxin (OCDD) and octachlorodibenzofuran (OCDF) were in excellent agreement with those reported in literature. The application of the current method for the vapor pressure determinations of eight polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/PCDFs) in the extended temperature range (up to 275 °C) is reported. The extension of the vapor pressures to such temperatures, unprecedented for the PCDDs/Fs, is important for vapor-particle partitioning modeling in regions relevant to PCDD/F formation and control. Estimates for the melting temperatures and enthalpies of sublimation and vaporization are also reported, the latter for which no experimentally determined values have been found in the literature. The use of the method to deliver reproducible, trace concentrations (ppt-ppb) of targets was applied to the calibration of the jet-REMPI/TOFMS as an online detector for low chlorinated PCDDs/Fs.