(115f) Influence of Column Efficiency On Process Performance in Steady-State Recycling Chromatography

Besides SMB systems, several single-column techniques, such as closed-loop recycling and peak shaving, have been suggested to enhance the yield of chromatographic separation by recycling the chromatogram partially or as a whole. Steady state recycling (SSR) chromatography is a further development of these concepts. In an SSR process, in addition to collecting the leading and trailing parts of the elution profile, a constant amount of fresh feed is added to each recycle fraction, which causes the process to attain a periodic steady state.

Recently, we have presented a method for analysis and design of SSR chromatography with arbitrary purity or yield requirements at the limit of infinite column efficiency [1]. The approach applies to SSR processes in mixed-recycle operation and allows for the direct prediction of the steady state and the design parameters without performing dynamic simulations. Therefore, it simplifies optimal design of SSR processes and simultaneously enables evaluation of process performance.

It was also shown theoretically, that the productivity of SSR chromatography is necessarily lower than that of an optimized batch process. On the other hand, the SSR process always outperforms batch chromatography in terms of eluent consumption and product concentrations.

In the present work, separation of cycloketones on a hydrophobic polystyrene adsorbent XAD-16 is used as a model system. We present experimental data and numerical simulations that demonstrate the influence of limited column efficiency of the process performance (i.e., eluent consumption, specific productivity, product concentrations). A short-cut method for predicting the steady state of the SSR process from a single overloaded injection is presented and applied to the model system. In addition, we demonstrate how the short-cut method can be utilized to intensify the start-up phase of the SSR process.

References

[1] Sainio, T., Kaspereit, M., Analysis of steady state recycling chromatography using equilibrium theory, Sep. Purif. Technol., 66(2009), 9?18