Enantio-separation of racemic pindolol on α1-acid glycoprotein chiral stationary phase by SMB and Varicol

Research Progress on the Typical Variants of Simulated Moving Bed: From the Established Processes to the Advanced Technologies

Simulated moving bed (SMB) chromatography is a highly efficient adsorption-based separation technology with various industrial applications. At present, its application has been successfully extended to the biochemical and pharmaceutical industrial sectors. SMB possesses the advantages of high product purity and yield, large feed treatment capacity, and simple process control due to the continuous operation mode and the efficient separation mechanism, particularly for difficult separation. Moreover, SMB performs well, particularly for multi-component separation or complicated systems’ purification processes in which each component exhibits similar properties and low resolution. With the development of the economy and technology, SMB technology needs to be improved and optimized to enhance its performance and deal with more complex separation tasks. This paper summarizes the typical variants or modifications of the SMB process through three aspects: zone variant, gradient variant, and feed or operation variant. The corresponding modification principles, operating modes, advantages, limitations, and practical application areas of each variant were comprehensively investigated. Finally, the application prospect and development direction were summarized, which could provide valuable recommendations and guidance for future research in the SMB area.

Multi-Objective Optimisation of Biodiesel Synthesis in Simulated Moving Bed Reactor

In this work, multi-objective optimisation study was performed to determine the performance improvement in a simulated moving bed reactor (SMBR) for biodiesel synthesis. The selection of the operating parameters such as switching time, liquid flow rates in various sections, as well as the length and number of columns is not straightforward in an SMBR. In most cases, conflicting requirements and constraints influence the optimal selection of the decision (operating or design) variables. A mathematical model that predicts single-column experimental results well was modified and verified experimentally for multiple-column SMBR system. In this article, a few multi-objective optimisation problems were carried out for both existing set-up as well as at the design stage. A non-dominated sorting genetic algorithm (NSGA) was used as the optimisation tool for the optimisation study. Due to conflicting effect of process parameters, the multi-objective optimisation study resulted in non-dominated Pareto optimal solutions. It was shown that significant increase in yield and purity of biodiesel in SMBR was possible both for operating and at design stage.

Multi-Objective Optimizations of Non-Isothermal Simulated Moving Bed Reactor: Parametric Analyses

Simulated moving bed reactor (SMBR), a multicolumn multifunctional integrated reactor system, which can be exploited with on-site adsorptive separation to enhance conversion of equilibrium-limited reversible chemical reaction. In this article, for generality, a dimensionless SMBR model was developed and effects of five representative temperature distributions among different zones on the performance of an SMBR for reversible reaction in the general form of a reactant decomposed to two products were evaluated based on simultaneous maximization of unit throughput and product purity. Multipliers were applied to adjust some of the model parameters such that different operation modes can be compared under various conditions in the parametric space. The multiobjective optimization problems were solved using the non-dominated sorting genetic algorithm. All simulations were carried out using FORTRAN codes. The results showed that both kinetics and adsorptive separation play important roles in SMBR. When kinetics is fast or adsorptive potency of the reactant is higher than the desired product (B) but lower than byproduct (C), non-isothermal operation can significantly improve unit throughput. On the contrary, feed concentration and reaction enthalpy have minor effects on the optimal solutions. Decision variables based on flow rate ratios and internal concentration profiles were used to explain the trends of Pareto optimal solution.

Progress in the Enantioseparation of β-Blockers by Chromatographic Methods

β-adrenergic antagonists (β-blockers) with at least one chiral center are an exceedingly important class of drugs used mostly to treat cardiovascular diseases. At least 70 β-blockers have been investigated in history. However, only a few β-blockers, e.g., timolol, are clinically marketed as an optically pure enantiomer. Therefore, the separation of racemates of β-blockers is essential both in the laboratory and industry. Many approaches have been explored to obtain the single enantiomeric β-blocker, including high performance liquid chromatography, supercritical fluid chromatography and simulated moving bed chromatography. In this article, a review is presented on different chromatographic methods applied for the enantioseparation of β-blockers, covering high performance liquid chromatography (HPLC), supercritical fluid chromatography (SFC) and simulated moving bed chromatography (SMB).

Development of a fourth-order compact finite difference scheme for simulation of simulated-moving-bed process

A fourth-order compact finite difference scheme was developed to solve the model equation of simulated moving bed, which has a boundary condition that is updated along the calculation process and cannot be described as an explicit function of time. Two different methods, direct method and pseudo grid point method, were proposed to deal with the boundary condition. The high accuracy of the two methods was confirmed by a case study of solving an advection-diffusion equation with exact solution. The developed compact finite difference scheme was then used to simulate the SMB processes for glucose-fructose separation and enantioseparation of 1,1′-bi-2-naphtol. It was found that the simulated results fit well with the experimental data. Furthermore, the developed method was further combined with the continuous prediction method to shorten the computational time and the results showed that, the computational time can be saved about 45%.

Enantioseparation of racemic aminoglutethimide using asynchronous simulated moving bed chromatography

The separation of aminoglutethimide enantiomers by the continuous multicolumn chromatographic processes were investigated experimentally and theoretically, where the columns were packed with cellulose tris 3,5-dimethylphenyl-carbamate stationary phase (brand name Chiralcel OD) and mobile phase was a mixture of n-hexane and ethanol with monoethanolamine additive. The continuous enantioseparation processes included a synchronous shifting process (SMB) and an asynchronous shifting process (VARICOL), which allowed reducing the column number (here from six-column SMB to five-column VARICOL process). Transport-dispersive model with the consideration of both intraparticle mass transfer resistance and axial dispersion was adopted to design and optimize the operation conditions for the separation of aminoglutethimide enantiomers by SMB process and VARICOL process. According to the optimized operation conditions, experiments were carried out on VARICOL-Micro unit using five-column VARICOL process with 1/1.5/1.5/1 configuration and six-column SMB process with 1/2/2/1 configuration. Products of R-aminoglutethimide (R-AG) enantiomer and S-aminoglutethimide (S-AG) enantiomer with more than 99.0% purity were obtained continuously from extract stream and raffinate stream, respectively. Furthermore, the experiemntal data obtained from five-column VARICOL process were compared with that from six-column SMB process, the feasibility and efficiency for the separation of guaifenesin enantiomers by VARICOL processes were evaluated.