Column optimization study

Extensive design and optimization studies have been carried out for this sequence (108). The principal optimization variables, ie, the design variables that have the largest impact on the economics of the process, are the redux ratio in the azeo-column the position of the tie-line for the mixture in the decanter, determined by the temperature and overall composition of the mixture in the decanter the position of the decanter composition on the decanter tie-line (see Reference 104 for a discussion of the importance of these variables) and the distillate composition from the entrainer recovery column. 

In the case of the distillation column under study, several options are available within the environment of the VAX cluster, for both simulation and optimization studies. PROCESS and SPEEDUP simulation programs were used throughout these studies. 

Chiralpak AD-RH column was studied by Kazusaki et al. [95], and the results are shown in Figure 21b. The chiral resolution of flubiprofen on Chiralpak AD-RH columns was studied by Aboul-Enein and Ah [92], They observed that the best resolution occurred at 25°C. Finally, the influence of temperature on enantios-electivity differs from one analyte to another. Thus researchers have an ideal tool for optimizing throughput per unit time in preparative chromatography or a possibility for improving the sensitivity of analytical methods. 

Several investigations addressing these issues were performed in process-optimization experiments [71]. With regard to efficient recovery and re-use of the catalyst, use of chloroform is suitable, because of the insolubility of L-proline. Although the ee obtained was somewhat lower (61% ee for (R)-38b in CHCI3 compared with 76% ee in DMSO), the organocatalyst was quantitatively recovered by simple filtration and re-use of the catalyst indicated there was no loss of activity. As an alternative method, immobilization of L-proline on a silica gel column was studied but resulted in less satisfactory results [71]. 

Jiang, G. B., M. Ceulemans, and F.C. Adams. 1996. Optimization study for the speciation analysis of organotin and organogermanium compounds by on-column capillary gas chromatography with flame photometric detection using quartz surface-induced luminescence. J. Chromatogr. A 727 119-129. 

Optimization studies undertaken to influence the ratio of products, including temperature, reagent stoichiometry, and solvents were unsuccessful. It was decided that for early evaluation of maraviroc the use of DAST was acceptable. Within the discovery setting, the inseparable mixture of the difluoro and vinyl fluoro cyclohexyl esters 20 and 21 was subjected to Upjohn conditions for dihydroxylation of vinyl fluoro side product 21. After an overnight reaction, the required difluorocyclohexyl ester 20 could be isolated in high purity by flash column chromatography. Saponification gave the acid 11, which could be recrystallized from cyclohexane to furnish analytically pure material. 

Szepesi and Gazdag studied the separation of 22 eburnane alkaloids on an octyl and octadecyl type of column. Optimal results were obtained on both columns with the mobile phase acetonitrile - 0.01 M aqueous ammonium carbonate (3 2). The octadecyl stationary phase gave better resolution than the octyl packing (Table 8.3, Fig. 8.3). The reversed-phase system was capable of separating the three different groups of eburnane alkaloids as well as separating... 

Optimization of an existing SMBR system Maximizing the purity of a fraction and the yield of a compormd and minimizing the solvent consumption are chosen as the three objective functions. Six decision variables were used in this optimization study, the switching time (fj), the number of columns in sections II, III, and IV, the amormt of raffinate produced, and the eluent consumed. Since the optimization of an existing system is considered, the number of columns, their lengths and their diameters were kept fixed, but the sensitivity of the results to the number of columns on the Pareto shift was studied. The flow rate in section II and the temperature of the columns were also kept constant in order to allow a comparison of the optimum results at constant operation cost. Of the two throughput parameters, the raffinate flow rate (j3) was selected as a decision variable, in order to determine the optimum raffinate flow rate for a constant feed flow rate. 

An unusual feature of the CD process for MTBE production is that it is recovered from the bottom of the CD column even though its normal boiling point (55°C) is less than the boiling point of methanol (64.5°C). This observation is attributed to the formation of a minimum boiling azeotrope from methanol and MTBE. Apparently, if sufficient quantities of MTBE were accumulated in the CD column, it would lift the methanol into the reaction zone of the column resulting in a higher methanol conversion. This unusual behavior is believed to be responsible for the multiple steady states observed in the MTBE synthesis shown in process simulation and optimization studies and verified experimentally. ... 

Many industrial processes which employ bubble column reactors (BCRs) operate on a continuous liquid flow basis. As a result these BCR s are a substantially more complicated than stationary flow systems. The design and operation of these systems is largely proprietary and there is, indeed a strong reliance upon scale up strategies [1]. With the implementation of Computational Fluid Dynamics (CFD), the associated complex flow phenomena may be anal)rzed to obtain a more comprehensive basis for reactor analysis and optimization. This study has examined the hydrodynamic characteristics of an annular 2-phase (liquid-gas) bubble column reactor operating co-and coimter-current (with respect to the gas flow) continuous modes. 

In this study, chromatographic experiments were 10 times faster with the monolithic column and results were equivalent to those obtained with the silica-based columns. This approach could be further optimized with faster gradient since flow rate should be increased by a factor 3 or 7 compared to conventional Cig supports [61, 62] and gradient time reduced by the same factor [63] to fully exploit the potential of monolithic supports. 

Once the resolution has been optimized as a function of gradient rate, one can continue to fine-tune the separation, raising flow rate and temperature. In a study of temperature and flowrate variation on the separation of the tryptic peptides from rabbit cytochrome c, column performance doubled while analysis time was reduced by almost half using this strategy.97 Commercially available software has been developed to aid in optimization. As a final note, in an industrial laboratory optimization is not completed until a separation has been shown to be rugged. It is a common experience to optimize a separation on one column, only to find that separation fails on a second column of identical type. Reproducibility and rigorous quality control in column manufacture remains a goal to be attained. 

Since many ion exchange columns exhibit mixed-mode interactions with analytes, factor analysis has been found to be useful in optimization.84 A 3-year, comprehensive review of inter-laboratory errors in determinations of the anions chloride, nitrate, and sulfate and the cations sodium, potassium, magnesium, and calcium suggested that multipoint calibration is essential and nonlinear calibration desirable.102 The need for nonlinear calibration was confirmed by an extended quality assurance study of chloride, sulfate, and nitrate in rainwater.103... 

Amperometric parameters have been studied and optimized for sugar separations.57236 The orcinol reaction has also been used as a post-column detection system for sugars.237... 

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