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Solubilities Of Cholesterol And Desmosterol

Posted on:2011-12-07Degree:MasterType:Thesis
Country:ChinaCandidate:W ChenFull Text:PDF
GTID:2121360302481271Subject:Applied Chemistry
Abstract/Summary:PDF Full Text Request
The by-product in the purification of cholesterol has a high content of desmosterol.Desmosterol is a highly active steroid and has a similar structure as cholesterol.The solubility study is very important for the separation of the two steroids and the solvents of extraction and crystallization process can be optimized by using the solubility prediction model.The melting points and fusion enthalpies of cholesterol and desmosterol were measured by DSC.The solubilities of cholesterol and desmosterol in single solvents and binary mixtures of n-hexane+ethanol from 293.2 K to 323.2 K were measured by a static method combined HPLC.The solubilities of cholesterol and desmosterol in binary mixtures of n-hexane+n-butanol,n-hexane+n-hexanol,n-hexane+n-octanol, n-hexane+acetone,n-hexane+ethyl acetate,ethanol+ethyl acetate,ethanol+water, DMSO+ethanol,DMSO+methanol,ethyl acetate+acetonitrile and 1,4-dioxane + methanol at 298.2 K were determined using a static method.Above all,the solubilities of cholesterol and desmosterol increase with the increase of temperature.The solubilites of two steroids in highly polar solvents like DMSO and acetonitrile are much lower than solubilities in hydrophobic solvents such as n-hexane,1-hexene, 1-octene,n-hexanol,ethyl acetate,2-butanone and 1,4-dioxane.The solubility profiles of steroids in the binary mixtures vary with the characteristic of the binary mixture.A solubility peak can be observed in binary solvents systems which contain a hydrophobic solvent and a hydrophilic or polar solvent.The existence of highly polar moleculars like water,DMSO and acetonitrile in the binary mixtures may lead to a decrease of the steroids solubility and the solubility profiles in binary mixtures containing such polar solvent do not have a peak.The solubilities were well correlated by the modified Apelblat equation and the AADPs were all less than 10%.The solubilities of steroids can be qualitatively judged by the Hansen model,and the AADPs of correlation results are 157%and 155%for cholesterol and desmosterol,respectively.The solubilities of cholesterol and desmosterol in binary mixtures of n-hexane+ethanol at different temperatures were well correlated by Wilson,NRTL and UNIQUAC models,and the correlated AADPs are 1.03%,0.89%and 1.84%for cholesterol and 1.52%,1.72%and 1.35%for desmosterol,respectively.Based on a limited set of experimental data,the newly developed NRTL-SAC model was first used to predict the solubilities of natural steroids with the AADPs for the prediction being 11.5%and 9.6%for cholesterol and desmosterol,respectively.A new steroid group was indentified in UNIFAC and the group interaction parameters were obtained from available experiment data.As a result,the solubilities of structurally similar steroids in single solvents can be well predicted by UNIFAC model,and the AADP of the predition is 209%.However,the solubilities in binary solvents were much better predicted by NRTL-SAC than UNIFAC.Furthermore,the models used here were all built in Aspen Properties and MATLAB.In conclusion,NRTL-SAC and UNIFAC models are useful in Selecting good solvents for industrial separation processes.
Keywords/Search Tags:cholesterol, desmosterol, solubility, model, NRTL-SAC, UNIFAC
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