Simulated moving bed chromatography for the separation of ethyl esters of eicosapentaenoic acid and docosahexaenoic acid under nonlinear conditions

In this study, ethyl esters of eicosapentaenoic acid and docosahexaenoic acid were separated with simulated moving bed (SMB) chromatography, where the stationary phase was C18 silica gel with particle size of 10 μm packed in eight columns, and the mobile phase was pure methanol. The Henry constants, transport parameters and total porosity were measured from pulse response chromatographic experiments using a single column. The Henry constants were obtained from the first moment analysis. The transport parameters including axial dispersion coefficients and effective mass transfer coefficients were obtained from the second moment analysis. Nonlinear adsorption equilibrium isotherms for the pure components and their mixture were determined from adsorption-desorption method. The Langmuir model was used to fit the experimental data, and the corresponding parameters were further used to predict the competitive adsorption equilibria of the mixture. The validity of mathematical model parameters was checked by a frontal chromatography experiment. The simulated results of the SMB process using these parameters agreed well with the experimental results. At the feed concentration of 100 g/L, the SMB separation was able to produce both solutes with relative purity above 99%, productivity of 13.11 g/L adsorbent/h, and solvent consumption of 0.46 L/g.