Comparisons of Recycle Chromatography and Simulated Moving Bed for Pseudo-binary Separations

The simulated moving bed (SMB) process has been extensively used in industrial separations for binary and pseudo-binary separations. In pseudo-binary mixtures because the desired component is the most or least retained, the other components do not have to be separated. The UOP Parex process for p-xylene purification is an example. When non-target components have similar adsorption behaviors, the SMB has higher productivity and requires less desorbent compared to batch chromatography. However, these advantages are dependent on the difference of adsorption behaviors of the non-target components. When the most retained component is the target, productivity and desorbent consumption is related to the retention behaviors of the most and least retained non-target components, respectively. In this research, the performance of batch chromatography with a single recycle stream is compared to a SMB process for pseudo-binary separations with competitive Langmuir isotherms. A ternary nucleoside separation was used as a model system for the simulation of batch and SMB processes. To determine the optimized operating condition of the SMB process, a multi-component hodograph transformation was numerically calculated to obtain the separation region in the mII-mIII plane and the regeneration region in the mI-mIV plane. To compare the performances of SMB and recycle batch chromatography, each process was simulated with the optimized operating conditions with detailed Aspen Chromatography simulations.