Study On Separating Cholesterol And Desmosterol With Simulated Moving Bed

Introduced by Broughton and Gerhold in the early 1960s,the Simulated Moving Bed (SMB) appeared predominantly in large scale separations in the petrochemical industry without any attention from fine chemical industry.This changed 15 years ago, when SMB was introduced as a novel technique to separate racemates in early drug development.The role of SMB in pharmaceutical industry has changed dramatically since then.Although SMB is now on its way from an emerging technology to a classical unit operation,the greatest task for the future will be to show that SMB technology is not a sophisticated,technically demanding and unreliable method for separating racemates,but an easy to master tool that can be applied both in early development and in scale-up production.This paper took cholesterol and desmosterol,valuable resources of intermediate for steroids,as study object.The adsorption equilibrium constants of desmosterol and cholesterol were determined as 7.86 and 10.02,respectively,by separating of cholesterol and desmosterol with fixed-bed chromatography.The porosity of chromatograhy columns was 0.68.With these parameters,the region leading to complete separation predicted by triangle theory was able to be drawed out for the choosing of the initiative operating variables.A general multicomponents rate model based on differential mass balance equations is adopted for simulating SMB.According to the outlined numerical solution,results of the simulation program in MATLAB^(?) are shown.Separation of desmosterol from cholesterol by SMB was simulated.The effects of flow rate in section 2(Q₂) and 3(Q₃),switching time,feed flow rate and feed concentration were studied on the operating performance parameters as purity, recovery,productivity and desorbent consumption.And Operating conditions leading to more than 90%purity in both outlet streams had been identified,together with those achieving optimal performance.Comparison between the results of simulations and the experimentation indicates that the present model describes very well the dynamic behavior of the systems under study.A simple optimization procedure was runned for the choosing the optimal SMB operatingg conditions.Under temperature column of 35℃,switch time 9min,with flow rate of Q₁=6.5ml/min,Q₂=4.4ml/min for,Q₃=4.65ml/min,Q₄=3.0ml/min, cholesterol and desmosterol are separated completely.