Design and optimisation of a simulated moving bed unit: role of deviations from equilibrium theory.

The design of a simulated moving bed involves thermodynamic, kinetic and hydrodynamic aspects and requires the optimisation of several variables: plant design variables, such as the column length and diameter, and operating variables, among them four independent flow-rates, the feed concentration and the switch time. In this work we develop an algorithm to design both the unit and its operating conditions, with an overall view on equilibrium properties, efficiency and hydrodynamics, using a simple equilibrium stage model. In this way we determine the parameters leading to the highest possible productivity for a given separation, only requiring the knowledge of the equilibrium isotherms, the Van Deemter equation and a correlation for pressure drop. The algorithm has been used to investigate the effect on the separation performance of some parameters, such as particle size and required product purity, which are not considered by equilibrium theory. The results have been compared with the predictions of equilibrium theory and the observed deviations have been put in evidence and discussed.

Enantiomer separation of alpha-ionone using gas chromatography with cyclodextrin derivatives as chiral stationary phases.

The gas chromatographic enantiomer separation of alpha-ionone was studied with three different chiral stationary phases using as chiral selectors: (1) heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin, dissolved in polysiloxane PS-086, (2) octakis(2,6-di-O-pentyl-3-O-trifluoroacetyl)-gamma-cyclodextrin and (3) octakis(2,6-di-O-pentyl-3-O-butanoyl)-gamma-cyclodextrin, both dissolved in polysiloxane SE-54. The influence of the concentration of the chiral selector in the polysiloxane, coated on Chromosorb P AW-DMCS 80-100 mesh, is described and discussed, as well as the effect of Chromosorb loading. The feasibility of the preparative gas chromatographic separation of the enantiomers of alpha-ionone is considered; in order to provide a term of comparison, the estimated performances are compared with those achieved in the separation of the enantiomers of the inhalation anaesthetic enflurane.