Theoretical and Experimental Study on Residue Curve Maps of Propyl Acetate Synthesis Reaction

Residue curve maps of propyl acetate synthesis reaction in the batch reactive distillation process are studied. In order to adapt the model equations of residue curve maps to a practicable heating policy, the theoretical analysis and experimental measurements in this paper are carried out isothermally instead of the autonomous heat policy first introduced by Venimadhavan et al. (1994). The chemical equilibrium constant of this reaction is determined by experiments to be 20 within the temperature range 80 °C ~ 110 °C. Using this equilibrium constant, the RCMs predicted by simulation are in good agreement with the experimental measurements. The results show that there is an unstable node branch emerging from the propyl acetate-water edge, moving toward the chemical equilibrium surface with the increasing Damköhler number (Da), and eventually reaches the quaternary reactive azeotrope when Da approaches infinity. Residue curves are measured with initial compositions around the unstable node, and thus the results verify the existence of this reactive azeotrope. Further bifurcation analysis shows that different heat policies will influence the singular points and topology of kinetically controlled RCMs, but not the cases when Da = 0 or Da approaches infinity. © 2005 Elsevier B.V. All rights reserved. [accessed 2013 November 27th

Potential of Chiral Solvents for Enantioselective Crystallization. 1. Evaluation of Thermodynamic Effects

It can be expected that a chiral solvent possesses a certain potential to discriminate between two enantiomers by creating specific weak interactions and forming diastereomeric complexes which have different physical properties. Thus, for chiral solvents, there might be an asymmetry in the solubility phase diagrams that could be employed for resolution purposes. In this work, investigations were carried out to identify appropriate chiral solvents for the discrimination of enantiomers with the aid of nuclear magnetic resonance (NMR) spectroscopy and Raman spectroscopy. The 1H NMR and Raman spectra results of mandelic acid in the chiral solvents did not show any significant chiral recognition. The effect of (S)-ethyl lactate and (2R, 3R)-diethyl tartrate on solubility was examined by measuring the ternary phase diagrams of mandelic acid and N-methylephedrine. The phase diagrams determined at different temperatures were symmetric indicating again that the used chiral solvents have less or no influence on the thermodynamics of solution. However, in additional experiments, it was found that there can be significant differences in the nucleation behavior of the two enantiomers in a chiral solvent. Copyright © 2008 American Chemical Society [accessed October 8, 2008