拉曼光谱快速跟踪二元液系气液相平衡组成

Fast tracking of gas-liquid phase equilibrium composition of binary liquid system by Raman spectroscopy

通过拉曼光谱技术结合空间角度转换算法,建立了在线快速分析多元液系气液相平衡组成的新方法。以环己烷-乙醇为研究对象,首先采集建模样本的拉曼光谱数据,求取样本光谱与纯环己烷光谱的角度方差值,建立环己烷组成与方差值的线性关联方程;将实验各平衡点下体系的拉曼光谱数据转换成方差值,代入线性方程可求出对应平衡点的环己烷含量,实现体系组成在线分析,并将拉曼光谱法测定结果进行了热力学一致性检验。结果表明:折光率法的数据与文献值接近;经过温度校正后,拉曼光谱法测定的气相环己烷含量与折光率法基本吻合,误差<5.81%;环己烷-乙醇二元相图中最低恒沸点为65.2℃,与文献[1]的值基本相同;实验结果符合热力学一致性检验。与经典的折光率法相比,此方法简便快捷,只需采集拉曼光谱即可快速分析二元液系各组成的含量,可以推广应用于蒸馏、吸收分离和精馏等单元操作过程中的多元体系分析。

A new method for online analysis of gas-liquid phase equilibrium composition of multiple liquid system was developed by combining Raman spectroscopy with spatial angle conversion algorithm.With cyclohexane-ethanol as the research object,firstly,Raman spectrum data of the modeling sample were collected;the angle variance values of the sample spectrum and the pure cyclohexane spectrum were obtained;the linear correlation equation between cyclohexane composition and variance values was established.Secondly,Raman spectral data of the system at each equilibrium point were converted into variance values,by substituting which into the linear equation,the cyclohexane content at the corresponding equilibrium point was obtained to realize online analysis of the system composition.Finally,the results of Raman spectroscopy were tested for thermodynamic consistency.The results show that the data of refractive index method are close to the literature value;after temperature correction,the results of gas phase cyclohexane composition determined by Raman spectroscopy are in good agreement with those by the refractive index method,and the error is within the range of 5.81%;the lowest constant boiling point in the cyclohexane-ethanol binary phase diagram is 65.2℃,which is basically the same as that in the literature.The experimental results accord with the thermodynamic consistency test.Compared with the classical refraction method,this method is simple and fast,and can be used to analyze the components of the binary liquid system quickly by collecting Raman spectrum.It can also be applied to the analysis of the multi-component system in the unit operation of distillation,absorption separation and rectification.