逆向法测定酮洛芬对映体在Chiralpak AD柱上的吸附等温线

模拟移动床（SMB）色谱分离与纯化的操作过程复杂,对其进行设计与优化需要使用数值模拟方法,准确测定竞争型吸附等温线具有重要意义。采用逆向法确定了25℃下酮洛芬对映体在直链淀粉手性固定相（Chiralpak AD）上的竞争吸附等温线,先用高效液相色谱测得酮洛芬对映体在Chiralpak AD 柱上的过载流出曲线,再通过拟合实验测得的流出曲线确定吸附等温线模型及其参数。研究中采用平衡扩散模型描述酮洛芬对映体在色谱柱上流出的瞬态过程。参数拟合过程中,首先用非支配基因算法（NSGA-Ⅱ）在较广的参数空间内搜索吸附等温线模型参数,再以所得结果作为初值,使用Levenberg-Marquardt 算法（LMA）对参数进一步优化。比较了4种不同竞争吸附等温线模型对实验测得的流出曲线的拟合结果,其中五参数的Bi-Langmuir 模型拟合程度最好。测量了不同进料浓度和进料量条件下的流出曲线,并通过与模型预测结果的对照验证了所确定吸附等温线模型和参数。     

逆向法测定氨氯地平在色谱柱Chiralpak OD-H上的竞争吸附等温线

使用逆向法测定氨氯地平在色谱柱Chiralpak OD-H上的竞争吸附等温线,先用泵进样的方式在高效液相色谱上测定氨氯地平的过载流出曲线,再选用5参数Bi-langmuir吸附等温线模型对过载流出曲线进行拟合,确定吸附等温线模型及模型参数,并验证参数准确性。     

逆向法确定色氨酸对映体竞争型吸附等温线

引言 吸附等温线测定是研究色谱分离过程的关键,其准确性直接影响到色谱分离过程的准确程度,因此,选择适当的实验方法和数学模型来模拟吸附等温线是模拟色谱分离过程的一个重要环节.常用的几种方法包括:前沿分析法、特征点洗脱法、特征点前沿分析法以及扰动法[1-2].其中前沿分析法是最常用的方法,该方法简单,准确性高,可用于多组分竞争型吸附等温数据的测定,但其数据采集过程非常耗时,对原料的需求量大,且需要考察单组分吸附等温模型与吸附数据的拟合程度.     

程序升温脱附测定难挥发性有机物吸附相平衡

提出一种采用少量程序升温脱附实验就能计算挥发性有机物在不同温度下吸附等温线的方法.该方法以拟平衡吸附动力学为基础,建立难挥发性有机物从吸附剂表面程序升温脱附的模型,采用数值方法对该模型进行求解.采用该模型对程序升温脱附实验测定的图谱进行模拟,获得难挥发性有机物在吸附剂上的吸附相平衡参数,从而确定吸附等温线.运用所提出的...     

迎头色谱法测定人参皂苷Rg1和Re的吸附量

制备色谱分离条件优化的基础是吸附等温线的测定及保留时间的预测。本文以人参皂甙Rg₁、Re为研究对象，用色谱单柱制备了人参粗粉中的人参皂甙Rg₁、Re,以迎头法测定了人参皂甙Rg₁、Re在C₁₈球形固定相中的吸附等温线，在竞争Langmuir模型基础上确定了吸附参数G和b，并应用非线性色谱理论的结果预测了人参皂甙Re的保留时间，上述结果与实验值进行了比较，平均相对误差为3.68%。在实验中发现了运用竞争Langmuir模型进行拟合的一些问题并进行了讨论。     

槲皮素粗品吸附特性的测定与保留时间的预估

吸附等温线表示了组分在固定相和流动相两相之间浓度平衡的状态,对工艺设计和色谱过程模拟也有很重要的作用。前沿分析法是测定吸附等温线的较为准确、快速和经济的方法之一。该文的主要目的是利用前沿分析法测定槲皮素粗品的吸附等温线,并以此为基础,计算出保留时间,再与实验中的保留时间进行比较。实验中,选择了测定吸附等温线的条件,在选定条件的基础上,测定了3种不同槲皮素样品的吸附等温线,将它们的吸附特性进行了比较。结果表明,用单组分近似处理槲皮素粗品的吸附等温线是合理的,与标品及生化试剂测定的结果比较,符合多组分吸附竞争特性,合理地反映了杂质对吸附特性的影响。结果表明,在制备条件下通过计算得到的保留时间与实验测得的保留时间基本相符。因此,该文的方法可以作为优化槲皮素分离条件的基础。     

色谱法测定葡萄糖果糖在制备柱上的传质和扩散系数

色谱模型对研究色谱分离过程中的传质动力学具有重要的意义。根据物料守恒原理,结合传质扩散模型推导色谱分离连续方程。假设吸附过程相平衡是线性,连续性方程推导出理论板数与流速和色谱模型参数有关。在多组不同流速条件下测定色谱柱参数,计算得到两组分的传质系数和扩散系数。分别用测定模型参数模拟脉冲实验,结果表明拟合较好。     

基于微孔过滤板的蛋白吸附高通量筛选方法

针对色谱分离过程优化,建立了基于微孔过滤板的蛋白吸附高通量筛选方法,用于介质初筛、吸附性能考察、吸附等温线和吸附动力学测定、吸附和洗脱条件优化等。首先优化了96孔过滤板的操作参数,以2种离子交换介质和2种混合模式介质为典型代表,采用微孔过滤板方法考察了不同介质和液相条件下牛血清白蛋白的吸附,得到结合载量分布图,确定了合适的蛋白吸附和解吸条件。进一步测定了4种介质在特定吸附条件下的吸附等温线和吸附动力学曲线,获得吸附相关参数。最后,采用微孔过滤板进行了洗脱条件优化,并与填充柱色谱分离进行比较,验证了方法的可靠性。结果表明,基于微孔过滤板的蛋白吸附高通量筛选是切实可行的,可以快速筛选色谱介质和液相,优化蛋白分离条件,具有资源消耗小、实验通量大、研发周期短、适用性广、稳定性高的特点,是蛋白色谱分离过程优化的一种新方法。     

基于微孔过滤板的蛋白吸附高通量筛选方法

针对色谱分离过程优化,建立了基于微孔过滤板的蛋白吸附高通量筛选方法,用于介质初筛、吸附性能考察、吸附等温线和吸附动力学测定、吸附和洗脱条件优化等。首先优化了96孔过滤板的操作参数,以2种离子交换介质和2种混合模式介质为典型代表,采用微孔过滤板方法考察了不同介质和液相条件下牛血清白蛋白的吸附,得到结合载量分布图,确定了合适的蛋白吸附和解吸条件。进一步测定了4种介质在特定吸附条件下的吸附等温线和吸附动力学曲线,获得吸附相关参数。最后,采用微孔过滤板进行了洗脱条件优化,并与填充柱色谱分离进行比较,验证了方法的可靠性。结果表明,基于微孔过滤板的蛋白吸附高通量筛选是切实可行的,可以快速筛选色谱介质和液相,优化蛋白分离条件,具有资源消耗小、实验通量大、研发周期短、适用性广、稳定性高的特点,是蛋白色谱分离过程优化的一种新方法。     

吸附热预测吸附等温线

实验测定了N2 在沸石分子筛、C2 H6 在活性炭、CO2 在硅胶上的吸附等温线 ,研究用Clausius Clapeyron方程求得等量吸附热、再利用所得的吸附热预测其它温度的吸附等温线数据的方法。将吸附热预测的等温线与实验值及插值法内插得到的吸附等温线数据进行了比较 ,结果表明吸附热预测值与实验值吻合较好。此外还对文献数据利用等量吸附热预测较高压力 ( 65 0kPa)下的等温线 ,均与文献中的实验值一致。为吸附工业操作需要不同温度下的等温线数据和吸附过程的模拟与设计提供了简便、准确的计算方法     

Separation of p-xylene from binary xylene mixture over silicalite-1 membrane: Experimental and modeling studies

The permeation of single component and binary mixture containing p-xylene and o-xylene through silicalite-1 membrane was studied experimentally in the temperature range of 150–250 °C at feed partial pressure of 0.26 kPa for p-xylene and 0.22 kPa for o-xylene. The model for single component flux based on the combination of dual-site Langmuir isotherm and Maxwell–Stefan formulation was derived. The adsorption parameters were estimated by minimizing the difference between the experimental flux and simulated flux. The heat of adsorption and entropy values obtained were in good agreement with the reported values. The effect of feed partial pressure in the range of 0.20–1.50 kPa on xylene flux was predicted using the adsorption parameters and compared with the experimental values. The Maxwell–Stefan diffusion model, in combination with the ideal adsorbed solution (IAS) theory and single-component adsorption parameters was used to predict the permeation flux of p-xylene and o-xylene for binary xylene mixture through the silicalite-1 membrane. The simulated results were in good agreement with the experimental data. The simulated adsorption isotherm in higher temperature range of 150–250 °C using the model and derived adsorption parameters could provide useful information for adsorption of xylene molecules on silicalite-1 membrane at a higher operating temperature.     

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.     

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.     

Modeling and simulation of a simulated moving bed for adsorptive para-xylene separation

A multi-cell model was developed to analyze the behavior of a simulated moving bed process for adsorptive para-xylene separation from other xylene isomers. A novel technology for a semi-batch mode adsorption experiment was developed and used for fast and accurate data collection. Interaction parameters between different species for a multi-component extended Langmuir isotherm were estimated from single and multi-component adsorption experiments and implemented into the model. The parameters such as porosities, particle density and mass transfer coefficients were obtained from adsorbent analysis and commercial plant operation. To resolve the problem of high dimensionality, a cell-by-cell approach was proposed to solve the model. The recovery and purity of para-xylene as well as the concentration profile calculated from the model were in good agreement with the actual data. The effects of channeling and feed composition change were simulated, and they turned out to be physically meaningful. The simulation model will be used for operation condition optimization, trouble shooting, and productivity enhancement including a configuration change.     

Adsorption of Naphthol Green B on unburned carbon: 2-and 3-parameter linear and non-linear equilibrium modelling

The study deals with adsorption of Naphthol Green B on two unburned carbons and the parent coal,from which the UCs have been created in a fluidised-bed power station.Particular attention has been paid to the adsorption equilibrium modelling:experimental data has been analysed using 2-parameter(Langmuir,Freundlich) and3-parameter(Redlich-Peterson) isotherms — both linear and non-linear regressions have been used for the estimation of the isotherm parameters.In the case of both UCs,the Langmuir isotherm model provides the worst fit,whereas 2-parameter Freundlich and 3-parameter Redlich-Peterson models are both good,from which 3-parameter Redlich-Peterson isotherm provides slightly better results(despite the penalty used for the higher number of parameters).In the case of both UCs,the linear regression of Freundlich and Redlich-Peterson models provides good results(comparable with non-linear regressions).Unlike both UCs,the best fit of the experimental data from the adsorption on the coal has been achieved by the Langmuir isotherm model.The results based on the Freundlich or Redlich-Peterson model were(in this case) somewhat worse.     

改性活性炭对甲基橙的吸附

用盐酸和氨水对活性炭进行改性获得改性活性炭,将其用于处理甲基橙废水,考察了改性条件、振荡速度和温度等因素对甲基橙吸附性能的影响,采用吸附等温模型和吸附动力学模型进行拟合,并分析吸附过程的热力学特征. 结果表明,盐酸改性活性炭对甲基橙的吸附效果优于氨水改性活性炭,在甲基橙初始浓度60 mg/L、溶液体积50 mL、温度20℃、振荡速度100 r/min、盐酸改性活性炭投加量0.2 g时,24 h基本达到吸附平衡,甲基橙去除率为93.7%. 不同温度下,盐酸改性活性炭对甲基橙的吸附符合Langmuir(RC2>0.95)和Freundlich(RC2>0.97)吸附等温模型,饱和吸附量达112.7 mg/g. 热力学参数DG0<0,DH0>0,DS0>0,表明盐酸改性活性炭对甲基橙的吸附是自发吸热反应,其吸附动力学可用准二级动力学方程描述,随振荡速度增加,吸附速率常数增加.     

Nitrogen rejection from low quality natural gas by pressure swing adsorption experiments and simulation using dynamic adsorption isotherms

In order to remove N₂ from low quality natural gas, a mathematical model has been established by Aspen adsorption, using the CH₄-selective sorbent silicalite-1 pellets. The dynamic adsorption isotherm was first simulated by breakthrough simulation of a CH₄/N₂ mixture at different adsorption pressures and feed flow rates based on breakthrough experiments. The resulting simulated CH₄ dynamic adsorption amounts were very close to the experimental data at three different adsorption pressures (100, 200, and 300 kPa). Moreover, a single-bed, three-step pressure swing adsorption (PSA) experiment was performed, and the results were in good agreement with the simulated data, further corroborating the accuracy of the gas dynamic adsorption isotherm obtained by the simulation method. Finally, based on the simulated dynamic adsorption isotherm of CH₄ and N₂, a four-bed, eight-step PSA process has been designed, which enriched 75% (vol) CH₄ and 80% (vol) CH₄ to 95% (vol) and 99% (vol), and provided 99% (vol) recovery.