The adsorption equilibria relevant to the production of fructooligosaccharides were measured on Dowex Monosphere
99CA/320, Amberlite CR1320Ca, Lewatit S 2568, and Diaion UBK 530. The single-component isotherms of
glucose, fructose, and sucrose and multicomponent isotherms of fructooligosaccharides (kestose, nystose, and
fructofuranosylnystose) were obtained at a temperature of 60 °C and saccharide concentrations up to about 450
g·L-1. All but sucrose equilibrium data were described with a linear isotherm. The adsorption data of sucrose
were successfully fitted using a concave isotherm. The capacities and selectivities of the adsorbents were compared.
They showed that their separation effect was based on the size exclusion mechanism accompanied by complexation,
which depended significantly on the resin's ionic form.
Enantioseparation through liquid extraction technology is an emerging field, e.g., enantioseparations of amino acids (and derivatives thereof), amino alcohols, amines, and carboxylic acids have been reported. Often, when a new selector is developed, the versatility of substrate scope is investigated. From an industrial point of view, the problem is typically approached the other way around, and for a target racemate, a selector needs to be found in order to accomplish the desired enantioseparation. This study presents such a screening approach for the separation of the enantiomers of DL-α-methyl phenylglycine amide (DL-α-MPGA), a model amide racemate with high industrial relevance. Chiral selectors that were reported for other classes of racemates were investigated, i.e., several macrocyclic selectors and Pd-BINAP complexes. It appeared very challenging to obtain both high extraction yields and good enantioselectivity for most selectors, but Pd-BINAP-based selectors performed well, with enantioselectivities up to 7.4 with an extraction yield of the desired enantiomer of 95.8%. These high enantioselectivities were obtained using dichloromethane as solvent. Using less volatile chlorobenzene or 1-chloropentane, reasonable selectivities of up to 1.7 were measured, making these the best alternative solvents for dichloromethane.
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