改进SRK方程提高正构烷烃饱和蒸气压和液体体积预测精度

<正>引言 在化学工程和油藏工程的相平衡和其他热力学性质计算中,两参数立方型SRK方程应用最为广泛。然而,在某些情况下由SRK方程预测的饱和蒸气压出预测的液体体积偏差较大,无法满足工程计算的需要,必须改进方程,提高其预测精度。1 饱和蒸气压的改进 SRK方程可以写为 p=RT/（V-b）-(a(T)）/V(V+b) （1）     

立方型状态方程用于液体过量体积的计算

用 SRK、PR 和 YU-LU 三个立方型状态方程对常压下的液体混合过量体积进行了关联计算,涉及的体系包括非极性、弱极性、水及羧酸等强极性混合物。对于对称的非极性、弱极性、极性流体混合物获得了良好的结果,但这种计算方法不适用于含水或羧酸的体系。     

超临界CO2-共溶剂二元体系溶质的偏摩尔体积及分子间的相互作用

在313.5～323.5 K、7～14 MPa范围内测定了CO₂及CO₂-甲醇、CO₂-乙醇、CO₂-正丁醛、CO₂-异丁醛二元混合流体的表观密度,讨论了压力、第2组分的种类和加入量对CO₂表观密度的影响,在此基础上计算了溶质的偏摩尔体积,讨论了温度、压力和第2组分的性质对溶质偏摩尔体积的影响规律.实验发现：CO₂-共溶剂二元体系在临界点附近溶质的偏摩尔体积出现较大的负值,反映了CO₂与共溶剂之间存在较强的相互作用,使CO₂分子发生聚集现象;CO₂分子聚集程度与共溶剂分子大小及空间结构有关,分子越大或越规则,CO₂分子聚集程度越强.     

异丙醇铝在超临界丙烷中的溶解度与粒子制备

选用丙烷作溶剂在不同条件下进行超临界溶液快速膨胀（Rapid Expansion of Su-percritical Solution-RESS）制备异丙醇铝超细粒子的实验研究。同时用流动法装置测定了温度为388.15K和403.15K、压力为（21.5～30.5）MPa条件下异丙醇铝在超临界丙烷中的溶解度,并对其进行了关联计算。     

ON THE FLEXIBILITY AND LIMITATIONS OF CUBIC EQUATIONS OF STATE

Cubic equations of state have received much attention during the last decade^1-10 due to their simplicity and practical success. In particular, Abbott² has discussed a general form of the cubic equation of state and shown that cubic equations of state commonly used for chemical engineering calculations^11,12 are specializations of the generic form. The purpose of this work is to further study the flexibility and limitations of the generic form so as to enhance the understanding of recent developments and to provide a guide for future search of better specializations.     

COMMENTS ON CUBIC EQUATIONS OF STATE BASED UPON THE INFINITE PRESSURE LIMIT

We examine a recently proposed modification to equations of state of the Van der Waal's type that involves using an infinite pressure limit of the equation to derive new mixing rules for the attractive term parameter. Results on some example systems including both vapor-liquid and solid-supercritical fluid equilibria show that the proposed modification does not appear to enhance the equation over its conventional one-fluid form. It appears that the fundamental inadequacy of the repulsive force term in such equations, for dense fluids, cannot be easily overcome by added complexity for the attractive term expression. Hard sphere reference systems on the other hand provide a more accurate repulsive force term.     

立方型状态方程用于蒸发热的计算

推导出立方型状态方程计算纯流体蒸发热的新公式,该计算式的特点是式中含有能量参数对温度的导数 da/dT,而与 a(T)无关。根据这一公式对立方型状态方程推算蒸发热进行了比较分析,提出a(T)与 da/dT 相互独立的计算方法,并用 Peng-Robinson 方程对70多种物质(包括烃、醇、卤代烃、酮、无机气体等)进行了关联计算,蒸汽压和蒸发热的平均相对误差分别为0.70%和1.33%。     

ON THE COMPOSITION-DEPENDENT INTERACTION PARAMETERS IN EQUATIONS OF STATE

Composition-dependent interaction parameters have been applied to the calculation of vapor-liquid equilibria (VLE) in mixtures containing components of different chemical nature. Binary VLE have been correlated and ternary VLE have been predicted from binary data using five different mixing rules. Binary data can be accurately correlated for systems with moderate deviations from ideality using mixing rules with two binary parameters. For very strongly nonideal mixtures three binary parameters are needed. For the prediction of ternary VLE from binary information only the mixing rules of Panagiotopoulos and Reid (1986) and Schwartzentruber et al. (1987) are reliable. For most systems the quality of predicting ternary data is comparable to the quality of correlating binary data. Significant deviations are noted only for strongly nonideal systems close to phase separation. In these cases it is recommended to use models incorporating association in an explicit form. KEYWORDS Equations of state Mixing rules Multicomponent Vapor-liquid equilibria.     

ESTIMATION OF VAPOR PRESSURES OF ORGANIC NITROGEN AND SULFUR COMPOUNDS BY A GROUP-CONTRIBUTION METHOD

The group-contribution method for vapor pressures of hydrocarbons and organic compounds containing nitrogen or sulfur, based on the kinetic theory of fluids, is revised and extended to include new groups containing nitrogen or sulfur. Good representation is obtained for vapor pressure data in the region 1.30-270 kPa. The method may be used to estimate vapor pressures and enthalpies of vaporization for those organic fluids containing nitrogen or sulfur, where no experimental data are available.     

液体内压的预测和新溶解度参数值

引　言在作者先前的工作[1]中 ,已由液体混合的热力学模型导得一个比Ｓｃａｔｃｈａｒｄ -Ｈｉｌｄｅｂｒａｎｄ正规溶液理论更加严格的过量Ｇｉｂｂｓ自由能表达式 .据此 ,定义了一个新的溶解度参数Δ =λ/ｍ =δ2 /λ (1 )式中　δ2 =ΔＶａｐ Ｕｍ/Ｖｍ,为液体的内聚能密度 ;λ =ｐ1/2ｉ ,为液体内压的平方根 ;ｍ =ｐｉＶｍ/ΔＶａｐＵｍ,为Ｈｉｌｄｅｂｒａｎｄ参数 .不难看出 ,当ｍ =1时 ,Δ =δ ,故传统的Ｈｉｌｄｅｂｒａｎｄ溶解度参数δ只是式( 1 )的一种特殊情况 ,由于一般液体的ｍ不等于1 ,故Ｈｉｌｄｅｂｒａｎｄ溶解度参数必须…     

超临界溶液快速膨胀法制备二氯二茂钛微粒及催化乙烯聚合

为克服茂金属催化剂得到的聚合物形态难以控制、表观密度较低、易粘釜和不适于气相淤浆聚合等缺点,以超临界溶液快速膨胀过程为手段,以期制得颗粒分布均匀的细微催化剂颗粒,继而得到形态良好的聚合物.作为超临界流体技术的基础,首先测定了二氯二茂钛在超临界丙烷中的溶解度.在此基础上,用RESS方法制得了均匀的超细催化剂颗粒,且系统考察了溶液浓度、预膨胀温度、喷嘴结构和接收距离对沉析颗粒粒径的影响.最后,将RESS所制得的催化剂颗粒进行乙烯淤浆聚合,并分析聚合物形态结构.实验结果表明,在温度为383.15～408.15 K和压力为10～35 MPa范围内,溶解度随温度的增加而增加,随压力的升高而增加,说明在该操作范围内,不存在反向区.RESS操作的结果显示,二氯二茂钛颗粒粒径随溶液浓度的增大而减小,随预膨胀温度的升高而增大,而喷嘴直径的减小和喷嘴长度的增加将使得颗粒粒径增大,而收集距离的增加将使得颗粒粒径先增加后减缓,直至不再变化.通过对原始的催化剂颗粒和RESS制得的催化剂颗粒进行乙烯淤浆聚合表征发现,相比于原始催化剂,由于烯烃催化剂的复制原理,RESS制得的催化剂颗粒的聚合物具有良好的形态.     

A CRITICAL EVALUATION OF THREE EQUATIONS OF STATE FOR DENSE GASES AGAINST OBSERVED DATA

The van der Waals, the Benedict-Webb-Rubin, and a virial equation of state predictions for dense gases are evaluated against observed “integral” properties (p, ρ, T) and “slope” properties like the speed of sound [(∂p/∂p)^1/2₃], isothermal compressibility coefficient [(∂ In ρ /∂p)_T], and few other thermodynamic properties directly derived from the observed data. The documented procedure thus constitutes a stringent test methodology to evaluate the applicability of these equations of state to dense gases which may also be followed for appraising any other equation of state. The graphical comparisons between the predictions and the observed data are presented and discussed critically     

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。     

石英晶体微平衡法测定CO2在聚合物中的溶解度

将石英晶体微平衡法(QCM)用于气体在聚合物中溶解度的测定, 实测的CO₂在尼龙66、天然橡胶和聚氯乙烯中的溶解度与文献值符合较好.测定了CO2在聚苯乙烯、聚甲基丙烯酸甲酯和聚甲基丙烯酸正丁酯3种均聚物及苯乙烯-甲基丙烯酸甲酯共聚物、苯乙烯-丁二烯-苯乙烯共聚物、甲基丙烯酸正丁酯-甲基丙烯酸二甲基氨基乙酯共聚物和甲基丙烯酸正丁酯-丙烯酸全氟烷基乙基酯共聚物等嵌段共聚物中的溶解度, 并用链状流体状态方程对实验数据进行了关联，结果令人满意.     

PREDICTION OF PHASE EQUILIBRIA IN BINARY MIXTURES USING AN IMPROVED EQUATION OF STATE AND A THEORETICALLY CONSISTENT MIXING RULE

Prediction of thermodynamic properties and phase equilibria in fluid mixtures using a simple cubic equation of state is still a challenging problem. In this paper, we have predicted vapor/ liquid phase equilibria of several binary fluid mixtures using our previously developed improved Peng-Robinson equation of state and a theoretically consistent mixing rule. Our mixing rule combines the mixing rule of Wong-Sandier with a physically based combination rule. Mixtures are composed of nonpolar, nonassociating polar and associating polar fluids. Comparisons of theoretical predictions with experimental data show a very good performance of our approach in describing vapor/liquid phase equilibria of several mixtures, namely, carbon dioxide/ propane, ethane/hexane, butane/methanol, benzene/methanol, acetone/methanol, methanol/ ethanol, methanol/1-butanol, methanol/water and ethanol/water.     

COMPARISON OF FIFTEEN GENERALIZED EQUATIONS OF STATE TO PREDICT GAS-PHASE ENTHALPY

Fifteen generalized equations of state were compared on the ability to predict gas-phase enthalpy of pure compounds. All equations were tested against a set of 12006 literature data points. The accuracy varied with the equation and the range of temperature and pressure.     

双流体配位状态方程在共聚物及共混物体系中的应用

采用双流体配位模型状态方程,对三个共聚物体系P(VAC/E)、P(S/MMA)及P(EP),两个共混物体系PVME/PS、PPO/PS进行了关联,精度较好.提出了共聚物的共混物假设的新设想.在关联中发现共聚物及共混物体系的二元模型参数具有一定的加和性,本文采用一个较为简单的混合规则,用均聚物的模型参数估算二元模型参数,进行了pVT数据预测,并与实验数据比较,具有良好的预测效果.     

液态聚合物的内压与状态方程

由热力学关系建立了一个液态聚合物的状态方程.聚合物的热压力由对应状态原理得到,内压力由Lennard-Jones(6,12)势能函数导得.状态方程包含3个有明确物理意义的特性参数,能够满意地关联各种液态聚合物的pVT数据.对18个均聚物和4个共聚物的比体积关联结果表明,总的平均绝对偏差在0～50 MPa压力范围内为0.00042 cm³&#8226;g^-1,在全部实验压力范围内为0.00063 cm³&#8226;g^-1,优于Simha-Somcynsky方程算得的结果.     

IMPROVING CUBIC EQUATIONS OF STATE FOR HEAVY RESERVOIR FLUIDS AND CRITICAL REGION

It is shown that by considering the “b” parameter in a cubic equation of state (EOS) as acentric factor/temperature-dependent, liquid densities especially for heavy compounds and the region near the critical point can be estimated more accurately. The proposed equation can also be used for accurate estimation of critical compressibility factors of different compounds, Although the method is applied to Peng-Robinson equation of state (PR-EOS), it can be used for any other cubic equation of state. The proposed method is particularly useful for phase equilibrium calculations of reservoir fluids. The proposed equation requires critical temperature, critical pressure and acentric factor as the input parameters. The proposed equation of stale estimates properties of liquids, vapor-pressure and critical compressibility factors with greater accuracy for pure compounds and mixtures as well as light and heavy compounds found in reservoir fluids.     

EQUATIONS OF STATE FOR HARD-SPHERE CHAIN FLUIDS AND SQUARE-WELL CHAIN FLUIDS

Based on the statistical theory for chemical association,equations of state for hard-spherechain fluids(HSCFs)and square-well chain fluids(SWCFs)can be derived through the n-particlecavity correlation function(CCF)of the corresponding reference system,where n is the chain lengthor the number of segments of a chain molecule.The reference system is a fluid composed of only cor-responding monomers.In this work,the n-particle CCF is approximated by a product of effectivetwo-particle CCFs which accounts for correlations in nearest-neighbour and next-to-nearest-neighboursegment pairs.The CCFs for SWCFs may be expressed by a product of the corresponding functionfor HSCFs and a perturbation term originated from the square-well attractive potential.All these ef-fective two-particle CCFs and perturbation terms are density dependent.The dependence is determinedmainly by using computer-simulation results.The obtained equations can excellently describecompressibility factors and second Virial coefficients for HSCFs