Olivier Ludemann-Hombourger

The “VARICOL” Process: A New Multicolumn Continuous Chromatographic Process

A new continuous chromatographic process is presented. This is in contrast to the known simulated moving bed (SMB) process which employs a synchronous shift of inlet/outlet lines. The basic principle of the new VARICOL process is based on a non-synchronous shift of the inlet/outlet valves in a multicolumn system. A numerical example compares the performances of the new VARICOL process to the well-known SMB process. This study shows that the VARICOL performances can be better than those of the SMB process. For example, a 5-columns VARICOL permits the same purities to be reached as a 6-columns SMB with the same productivity. Interest in the process is also validated experimentally. Both SMB and VARICOL are optimized to reach the highest achievable productivity for given outlet purities. The productivity of a 5-columns system can be improved 18.5% by using the VARICOL process.

Application of the "VARICOL" process to the separation of the isomers of the SB-553261 racemate.

A new continuous chromatographic process (VARICOL) has been presented recently. The basic principle of the new VARICOL process consists of an asynchronous shift of the inlet/outlet lines in a multi-column system on a recycle loop. This process has been used to perform the separation of the optical isomers of the SB-553261 racemate. In this paper, we illustrate that for this specific separation, the VARICOL process is more efficient than the well-known SMB process.

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.

Optimization of simulated moving bed and Varicol processes

A new continuous chromatographic process (Varicol) has been presented recently. Its basic principle consists, in contrast to the traditional simulated moving bed (SMB) technology, of an asynchronous shift of the inlet/outlet lines in a multi-column system with a recycle loop. Due to the stronger influence of the discrete dynamics on the plant behavior, the design of a Varicol process requires the use of model-based optimization to take advantage of the very high flexibility of this process. The equilibrium theory which has been successfully applied to SMB by many practitioners fails to predict the region of complete separation accurately. In this paper, we present a rigorous model-based optimization framework, which can handle the SMB and the novel Varicol process in a systematic manner. The feasibility of the approach is demonstrated by the separation of a mixture of propranolol isomers which exhibits a highly non-linear multi-component adsorption behavior. Experimental results are presented and discussed.

Design of a Simulated Moving Bed: Optimal Particle Size of the Stationary Phase

The influence of the particle size on simulated moving bed (SMB) design is studied using the chiral separation of methyl mandelate on Chiralcel OD. The theoretical model of the pressure drop and band dispersion is validated with experimental results obtained with two different particle sizes (20 and 50 μm) using linear adsorption isotherms. The influence of the particle size on the SMB column size and productivity shows that the optimum particle size is 20–25 μm when working with an acceptable column length and a minimum amount of stationary phase. Due to the high cost of the coated silica stationary phases used for chiral separation, the separation cost is thus minimized.

The M3C Process: A New Multicolumn Chromatographic Process Integrating a Concentration Step. I—The Equilibrium Model

Abstract A new Multicolumn Chromatographic process, called M3C, is introduced. The originality of this process relies on the integration of a concentration loop at the extract level on the recycling stream of a Multicolumn Continuous Process (Simulated Moving Bed, Varicol…). Thanks to the tools of the equilibrium theory applied to an equivalent True Moving Bed integrating a concentration step, the working parameters of this new process are estimated in the case of multicomponent competitive Langmuir adsorption isotherms. The performances of this process are compared to those of the classical True Moving Bed in terms of productivity and eluent consumption, and exhibit significant improvement.