Balamurali Sreedhar

Systematic optimization and experimental validation of ternary simulated moving bed chromatography systems.

Over the past several decades, many modifications have been proposed in SMB chromatography in order to effectively separate a binary mixture. However, the separation of a multi-component mixture using SMB is still one of the major challenges. Recently, a computational study was performed which compared various existing isocratic ternary separation operating schemes (including the JO process) in terms of the maximum throughput attained, and Generalized Full Cycle strategy was proposed based on a systematic design, which was found to have significant improvement over existing strategies [Agrawal and Kawajiri (2012)]. Nevertheless, the operating strategies were not experimentally validated. In this study, we validate both JO and Generalized Full Cycle SMB systems experimentally. A simultaneous optimization and model correction scheme has been implemented to arrive at the optimal operating condition which satisfies the optimal productivity as well as the desired purity and recovery of products experimentally.

Optimization of reactive simulated moving bed systems with modulation of feed concentration for production of glycol ether ester

In this article, we extend the simulated moving bed reactor (SMBR) mode of operation to the production of propylene glycol methyl ether acetate (DOWANOL™ PMA glycol ether) through the esterification of 1-methoxy-2-propanol (DOWANOL™ PM glycol ether) and acetic acid using AMBERLYST™ 15 as a catalyst and adsorbent. In addition, for the first time, we integrate the concept of modulation of the feed concentration (ModiCon) to SMBR operation. The performance of the conventional (constant feed) and ModiCon operation modes of SMBR are analyzed and compared. The SMBR processes are designed using a model based on a multi-objective optimization approach, where a transport dispersive model with a linear driving force for the adsorption rate has been used for modeling the SMBR system. The adsorption equilibrium and kinetics parameters are estimated from the batch and single column injection experiments by the inverse method. The multiple objectives are to maximize the production rate of DOWANOL™ PMA glycol ether, maximize the conversion of the esterification reaction and minimize the consumption of DOWANOL™ PM glycol ether which also acts as the desorbent in the chromatographic separation. It is shown that ModiCon achieves a higher productivity by 12-36% over the conventional operation with higher product purity and recovery.

Transesterification of propylene glycol methyl ether in chromatographic reactors using anion exchange resin as a catalyst

Reactive chromatography using an anion exchange resin is proposed for a transesterification reaction of propylene glycol methyl ether (DOWANOL™ PM) with ethyl acetate to produce propylene glycol methyl ether acetate (DOWANOL™ PMA). This reaction is studied in batch and chromatographic reactors catalyzed by an anion exchange resin. Several anion exchange resins are tested and compared based on the performance of resin as an adsorbent and a catalyst. A chromatographic column is packed with a selected catalyst, AMBERLITE™ IRA904, and both reaction and chromatographic elution are studied at different temperatures and feed concentrations. The resulting chromatograms are fitted to a mathematical model to obtain adsorption equilibrium and reaction kinetic parameters by the inverse method. Compared to esterification investigated in a previous study, transesterification has advantages such as a higher conversion at lower temperature and easy removal of the byproduct which may lead to higher productivity. Deactivation of anion exchange resins is observed and potential solutions are suggested.

Evaluation of tertiary pyridine resin for the separation of lanthanides by simulated moving-bed chromatography

Lanthanide separation by simulated moving-bed chromatography was studied as a model system for separating lanthanide fission products and minor actinides from used nuclear fuels. The simulated moving-bed system was modeled for a tertiary pyridine anion-exchange resin supported on silica particles as the stationary phase and a mixture of methanol and 1 M nitric acid as the mobile phase. Pulse injection tests using a single packed column were used to obtain chromatographic parameters for mathematical modeling of the simulated moving-bed system. Higher concentrations of methanol improved the separation, but the chromatograms showed evidence of nonlinearity of the isotherms. The mathematical model of the simulated moving-bed process predicted a production rate of purified samarium and neodymium at 118 g solute/L resin/day and a purity of 99.5%. The optimal methanol ratio for the production rate for various product purities was determined from the model. The excellent separation of Nd and Sm suggests that the simulated moving-bed system could be applied to the separation of minor actinides such as americium and curium.

Transesterification of propylene glycol methyl ether by reactive simulated moving bed chromatography using homogeneous catalyst

A reactive chromatography process was investigated for a transesterification reaction of propylene glycol methyl ether (DOWANOL™ PM) using a homogeneous catalyst, a sodium alkoxide. In the proposed process, fresh catalyst is supplied with desorbent, which allows independent optimization of the adsorption properties of the stationary phase. Deactivation of catalytic activity can be avoided, which had been found to be the bottleneck in our previous study for heterogeneous catalysis. To model and optimize this process, a series of batch reaction experiments, and pulse injection tests with a chromatographic column with and without reaction were carried out. From the experimental data, equilibrium and kinetic parameters were estimated using the inverse method. Using this model, a simulated moving bed reactor was designed that achieves a conversion of 95% using the homogeneous catalysis concept.