THERMODYNAMIC STUDY ON THE ADSORPTION OF SOME ORGANIC ACIDS FROM AQUEOUS SOLUTIONS BY UNMODIFIED AND MODIFIED MONTMORILLONITE CLAYS

In this study, the adsorption of some organic acids from aqueous solutions on modified and unmodified montmorillonite clays was carried out as a function of temperature and initial concentration of the adsorbate, through adsorption isotherms and their thermodynamic parameters (ΔS, ΔH, and ΔG). The results showed that the adsorption capacity of the adsorbents increased with the concentration, at constant temperature, and decreased with the increase of temperature, at constant concentration. The negative values of ΔG and ΔH showed that the adsorption was a spontaneous and exothermic process. In general the experimental data were well represented by the Langmuir and Freundlich isotherms models.     

一个非局部组成型活度系数方程

根据前文提出的液体混合的通用Gibbs自由能模型,导得了一个两参数非局部组成型活度系数方程.它适用于各种小分子液体混合物和高分子溶液,并能由二元参数预测多元系汽液平衡.对小分子液体混合物的泡点计算结果表明,除了醇/烃系统外,计算准确度不逊于局部组成型活度系数方程.它对高分子溶液的适用性则明显地优于UNIQUAC等方程.     

多相多组分化学反应平衡和相平衡计算的遗传算法

引　言多相多组分化学反应平衡和相平衡的计算是热力学研究的基础问题 ,同时也是化工流程模拟的重要环节 ,建立快速、稳定的求解方法具有特别重要的理论和现实意义 早期的以及目前应用较多的平衡常数法 (K值法 )的缺点是要预先知道体系的组分数、相态和具体反应 ,不适用于相态和反应未知的复杂体系 .Gibbs自由能最小法虽然具有通用性 ,然而需要求解多变量和复杂约束的非线性规划问题 对于非理想体系 ,涉及逸度、逸度系数的计算 ,这还是一个含有大量局部最优解的非凸问题[1,2 ] ,所以传统的数学规划算法不能保证得到全局最优解 文献 [3]…     

A THERMODYNAMIC EQUILIBRIUM ANALYSIS OF GLUCOSE CONVERSION TO HYDROCARBONS

Deoxygenation, or removal of oxygen from oxygenates, is an important element in the hydrocarbon fuel production process from biorenewable substrates. A thermodynamic equilibrium analysis gives valuable insights on the theoretical limits of desired products when a substrate is reacted under a given set of conditions. Here we report the equilibrium composition of glucose-to-hydrocarbon system by minimizing the total Gibbs energy of the system. The system was treated as a mixture of 11 components comprised of C₆H₆, C₇H₈, C₈H₁₀ (ethyl benzene), C₈H₁₀ (xylenes), C₆H₅ –OH, CH₄, H₂O, C, CO₂, CO, and H₂. Equilibrium compositions of each species were analyzed between temperatures 300 and 1500 K and pressures 0–15 atm. It was observed that at high temperature, CO and H₂ dominate the equilibrium mixture with mole fractions of 0.597 and 0.587 respectively. At low temperatures the equilibrium mixture is dominated by CH₄, CO₂, H₂O, and carbon. The aromatic hydrocarbon composition observed at thermodynamic equilibrium was extremely small.     

基于无限稀释活度系数模型的状态方程

发展了一种从纯物质的性质参数预测混合物汽液平衡的方法,它是以立方状态方程的过量吉布斯自由能 g~E结合型混合规则和无限稀释活度系数 MOSCED模型为基础,由MOSCED模型预测得到活度系数方程的相互作用参数,从而得到混合规则中的g~E,使得状态方程能在较大温度和压力范围内预测汽液平衡.用此法预测了含极性组分体系常压到较高压力的汽液平衡,结果良好,与UNIFAC基团贡献状态方程的结果相当.     

PREDICTION OF THE ASYMMETRIC PEAK PROFILE USING A MATHEMATICAL METHOD WITH A COMPETITIVE LANGMUIR ISOTHERM

The adsorption characteristics of a single component and a binary component in the stationary phase using preparative chromatography were investigated with a six-adsorption isotherm model. These analyses were based on the Langmuir model. Each parameter of the adsorption isotherm was obtained with the adsorption raw data that was calculated by frontal analysis (FA). The experimental data and the values calculated using the adsorption isotherm model were compared. The bi-Langmuir model showed good agreement for phenol while the tri-Langmuir model showed good agreement for caffeine. Each characteristic of adsorption was obtained from these results. The effect of competitive adsorption was investigated using the parameters of the adsorption isotherm model with a single component. There was good agreement between the experimental data and the calculated values.     

PREDICTION OF THE ASYMMETRIC PEAK PROFILE USING A MATHEMATICAL METHOD WITH A COMPETITIVE LANGMUIR ISOTHERM

The adsorption characteristics of a single component and a binary component in the stationary phase using preparative chromatography were investigated with a six-adsorption isotherm model. These analyses were based on the Langmuir model. Each parameter of the adsorption isotherm was obtained with the adsorption raw data that was calculated by frontal analysis (FA). The experimental data and the values calculated using the adsorption isotherm model were compared. The bi-Langmuir model showed good agreement for phenol while the tri-Langmuir model showed good agreement for caffeine. Each characteristic of adsorption was obtained from these results. The effect of competitive adsorption was investigated using the parameters of the adsorption isotherm model with a single component. There was good agreement between the experimental data and the calculated values.     

固定化青霉素酰化酶生产6-APA的流程设计

针对本组研制的一种新型固定化青霉素酰化酶,以动力学方程为基础,分别进行了批式反应和连续反应的计算．对于批式反应,计算了不同浓度底物的水解过程和各种抑制因子对反应过程的影响;对于连续反应,计算了不同级数下的需酶量、转化率和成本消耗。结果表明,三、四级连续反应是可行的,有工业应用的前景。     

SIMULATING VARIOUS SCHEMES OF THE CLAUS PROCESS

An interactive program based on the Gibbs free energy minimization and the FLOWTRAN system analysis was written to simulate various schemes of the Claus process. Dew point calculation and feedback control loops were provided. Certain species are treated as inerts in units like condensers, reheaters, and the waste heat boiler, Simulation of the Claus process air demand and simulation of two Claus plants (including a commercial one) were presented and the results analyzed.     

CALCULATION OF VAPOR LIQUID EQUILIBRIUM AND EXCESS ENTHALPY WITH THE UNIQUAC EQUATION

The UNIQUAC equation was used for calculation of vapor liquid equilibrium (VLE)as well as excess enthalpy (h^E). Four sets of binary interaction parameters were applied: first, parameters estimated only from VLE data, then parameters from h^E data for both the original UNIQUAC equation and the Anderson modification, and finally parameters estimated from h^E and VLE data simultaneously. Calculations were performed for seven binary systems with polar components, representing different h^E behavior. The cross-prediction of h^E from VLE data works better than the reversed prediction. The model with parameters estimated simultaneously to both kinds of data can be applied successfully to both kinds of calculations, but it is a compromise between the models estimated from one kind of data.     

CALCULATION OF VAPOR LIQUID EQUILIBRIUM AND EXCESS ENTHALPY WITH THE UNIQUAC EQUATION

The UNIQUAC equation was used for calculation of vapor liquid equilibrium (VLE)as well as excess enthalpy (h^E). Four sets of binary interaction parameters were applied: first, parameters estimated only from VLE data, then parameters from h^E data for both the original UNIQUAC equation and the Anderson modification, and finally parameters estimated from h^E and VLE data simultaneously. Calculations were performed for seven binary systems with polar components, representing different h^E behavior. The cross-prediction of h^E from VLE data works better than the reversed prediction. The model with parameters estimated simultaneously to both kinds of data can be applied successfully to both kinds of calculations, but it is a compromise between the models estimated from one kind of data.     

回归方程在标准加入法测高岭土中铜的应用

用原子吸收光谱法测定高岭土中铜,分别用标准曲线法及标准加入法定量分析铜元素含量,比较了作图法和回归方程法处理标准加入法数据。结果表明,随铜元素变量,标准曲线法及标准加入法均有较好的线性关系,但测定的结果有差异。标准加入法因可消除基体干扰,测得铜结果准确度高。标准加入法适合基体复杂的试样的分析。作图法及回归方程均适用于标准加入法测铜的数据处理,作图法误差大,而回归方程法是快捷,误差小的简便方法。     

拟抛物面规则在氧化物陶瓷相图中的应用

运用三元系拟抛物面规则：（１）分析了氧化物三元系中热力学数据的正误；（２）判断了复杂氧化物的稳定性；（３）初步估计或预报一些复杂氧化物的热力学数据。     

用修正的Polanyi-Dubinin方程描述有机蒸气-水蒸气在活性炭上的吸附平衡

活性炭吸附法用于低浓度有机废气的治理,具有脱除率高、可以回收有机溶剂等优点。但由于废气中或多或少混有水蒸气,导致吸附能力降低,这种情况在相对湿度较高的南方地区尤为严重。定量地估计水蒸气对活性炭吸附容量的影响,对吸附装置的设计和操作,具有重要的指导意义。     

费托合成反应体系的热力学计算与分析

利用Benson基团贡献法和ABWY法估算了费托合成产物的标准生成焓、标准熵和摩尔定压热容,对费托合成反应体系的热力学性质进行了详尽的计算,得到不同反应温度下的反应焓、吉布斯自由能以及反应平衡常数等热力学性质。分析了不同反应步骤的热力平衡与限度,对反应生成烷烃、烯烃、含氧有机化合物的热力学可能性与生成顺序进行了判断,考察了温度和H2与CO摩尔比对合成气平衡转化率的影响。结果表明:费托合成反应是放热反应,低温时大部分反应在热力学上都能够自发地进行,并运行到很高的程度;高温时(大于635 K)生成烷烃、烯烃、醇及酸的大部分反应在热力学上不能自发进行;随着温度的升高,平衡转化率降低,随着H2与CO摩尔比的增大,平衡转化率升高;且所获的热力学数据对费托合成工艺研究及相关催化剂研发等具有重要的参考价值。     

AN EVALUATION OF ISOTHERMS IN THE DESCRIPTION OF COMPETITIVE ADSORPTION EQUILIBRIA

Since adsorption isotherm equations are widely used in the industry to model adsorption on substances like activated carbon, an investigation was done to determine the applicability of three of these equations, viz, the multi-component Freundlich, multi-component Langmuir and the isotherm equation proposed by Fritz and Schluender. Based on statistical thermodynamic principles a discrete adsorption model was recently proposed. This model was used to create sets of binary adsorption data with some non-ideal characteristics. These data sets were used to evaluate the isotherm equations

It was found that the Langmuir isotherm gave the best fits, except where the visible adsorption energy changes with the surface loading or where selective adsorption occurs. Under these conditions, the Freundlich equation or that proposed by Fritz and Schluender should be used. It is recommended that these equations should be used to model low coverage-low concentration regions, while the high coverage-high concentration regions should be modelled using the Langmuir isotherm if possible

Some recommendations are made in connection with the procedure to estimate parameters for these isotherm equations.     

碳酸二甲酯与苯酚酯交换合成碳酸二苯酯热力学分析

用分子模拟软件M aterial stud io、工艺过程模拟软件ChemCAD结合Benson基团贡献法,计算了碳酸二甲酯与苯酚酯交换合成碳酸二苯酯的反应焓变、反应熵变、吉布斯自由能变及平衡常数。结果表明,该反应为吸热反应,升高温度有利于DPC的生成。反应的热力学平衡常数很小,为了提高DPC收率,必须及时移走副产物甲醇。     

MATLAB(SIMULINK)在造纸浆水平衡计算中的仿真应用

造纸浆水平衡计算是既重要又比较复杂的过程。计算时容易出错,如果不及时检查修正,会影响整个过程。作者利用MATLAB提供的动态系统仿真工具SIMULINK对浆水平衡进行仿真,大大减轻了计算复杂度,并可方便的进行检验,同时可更改工艺流程,具有较强的通用性、灵活性和方便的扩充性。     

最概然Malek法分析TDE 85/MeNA环氧树脂体系固化机理

 采用非等温DSC法对三官能团环氧树脂TDE 85与甲基纳迪克酸酐（MeNA）固化体系进行了放热特性分析,升 温速率分别为5k/min、10k/min、15k/min、20k/min、25k/min及35k/min。在此基础上重点提出最概然Malek Flynn Wall Ozawa分析法,对其固化反应机理进行固化动力学参数分析,建立了能够正确描述固化反应过程的机 理模型。该方法求得固化体系反应表观活化能为E=67.05kJ/mol,表观指前因子为A=5.05×109s 1,反应机理函数 为f(a)=22.24(1-a)1.76。最后通过实验数据对最概然Malek Flynn Wall Ozawa分析法进行验证,证明该方法 能够精确的描述固化反应过程和机理特征。     

THE MASTER EQUATION FOR LINEAR ADSORPTION AND DESORPTION OF GASES ON SOLID SURFACES

A Markovian model has been derived for a process involving reversible physisorption and irreversible chemical adsorption of simple gaseous molecules on a solid surface, which obey linear rate laws. The model is written in terms of the conditional probability of transition between two populations, physisorbed and chemisorbed molecules. The resultant expression, the master equation of the process, has given rise to the governing differential equations for the mean and variance of the coverage of the solid surface by the gaseous molecules; these equations have been solved analytically. The variance or coefficient of variation, expressing the magnitude of fluctuations, is substantial for a small-size system, e.g., a highly evacuated and/or dilute system. It is not uncommon to find such a system at the commencement and conclusion of any process; these periods are the most critical from the standpoint of operation, monitoring and control.