Compact SMB chromatography for binary separation

A thesis submitted for the degree of Doctor of Philosophy

This thesis consists essentially of theoretical and experimental developments in the field of continuous chromatography using small-scale units. Continuous chromatographic separation processes based on the Simulated Moving Bed (SMB) technology were first patented and applied in 1961 for a large number of separations in the petrochemical industry and later for sugar separation. However, in the last two decades,due to the patent expiration, the process has been gaining great interest in the separation/purification of products in fine chemical and pharmaceutical industries. The conventional SMB comprises several identical columns which are serially connected in either a closed- or open-loop configuration. In order to simulate the movement of a solid bed in opposite direction to the fluid, the positions of the input and output streams are shifted downstream by one column, at fixed intervals, in the direction of fluid flow. With the development of new and efficient equipment and stationary phases, several new schemes of operating that differ from the conventional one have emerged. These include new concepts such as Varicol, ModiCon and PowerFeed processes, which rely on the periodic modulation of certain process parameters during the switching interval to enhance the efficiency of the separation. These advances are pushing the trend for units with a small number of columns, since the overall setup is more economical. However, when these newly schemes are applied in practice the process becomes more complex, because of the increased degrees of freedom that must be optimized. It is also less robust and more difficult to operate because it is more demanding on hardware. This additional complexity requires highly versatile SMB equipment, advanced optimization tools and robust control procedures. Experimental tools to experimentally reproduce the periodic state of multicolumn countercurrent chromatography with just one column are developed; they are economic and fast methods of experimentally exploring different column configurations and cyclic operation policies,ideally suited for applied research studies but may also be useful in the early stages of development, optimization, and validation of a new chromatographic separation. The feasibility of the proposed single-column system is experimentally demonstrated for several different column configurations, which include both synchronous and asynchronous port switchings and flow modulated schemes. Following the potentialities of these new operating schemes, a novel SMB system for binary separation that employs only two-columns is developed. The designed two-column process uses both the port switching and the flow rates modulation procedure. The process is very versatile since the cycle itself is optimized and adapted to the difficulty of the separation and process specifications. Furthermore, a simplified extension of the two-column setup which relies on a minimum pump number configuration and on a uniform flowrate scheme is built-up; additionally a further development on these simplified setup is applied which effectively enhances the process with only the cost of a small increase on the setup equipment. Potentialities of this new unit are illustrated comparing it to setups using the same amount of stationary phase.

Fundação para a Ciência e Tecnologia (FCT/MCTES)