Growth of ε-caprolactam crystals from the melt: The influence of cyclohexanone on the {111̄} and {110} forms

Berg, E. P.; Bögels, G.; Arkenbout, G. J.

doi:10.1016/s0022-0248(98)00113-4

Cited by 3 publications

(2 citation statements)

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“…The impact of water on the melt crystallization of ε-caprolactam has been studied , as this is another important impurity that affects the performance of the resulting crystalline product but, more particularly, because melt crystallization as a route for purification is greatly preferable to the existing, energy-intensive, multistage distillation process for the purification of caprolactam. The effect of cyclohexanone as an impurity has also been studied. − …”

Section: Resultsmentioning

confidence: 99%

“…The differential binding energies for the forms {200}, {110}, and {111̄}, as reported in Table , are very similar. In the case of cyclohexanone as an impurity in the growth of ε-caprolactam from the melt, experimentally measured segregation coefficients are available for the {110} and {111̄} forms . The value of the equilibrium segregation coefficient calculated for the {110} form at 298 K is 4.2 × 10 -3 and at 342 K (the melting point of pure ε-caprolactam) is 8.4 × 10 -3 .…”

Section: Resultsmentioning

confidence: 99%

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Molecular and Solid-State Modeling of the Crystal Purity and Morphology of ε-Caprolactam in the Presence of Synthesis Impurities and the Imino-Tautomeric Species Caprolactim

2003

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A study of impurity incorporation into host crystal surfaces, using molecular modeling techniques, is presented for -caprolactam, illustrating a rapid method for predicting the effects of additives on the purity and shape of particles formed through crystallization. Optimum positions, in terms of calculated lattice energy, were located for the impurity molecules within the host crystal lattice. Differential binding energies and modified attachment energies were calculated using the program HABIT95 (Clydesdale, G.; Roberts, K. J; Docherty, R. Quantum Chemistry Program Exchange 1996, 16, 1) for each impurity molecule for all the important growth forms. From the differential binding energies, values were calculated for the equilibrium segregation coefficients. The impact of the impurities cyclohexane, cyclohexanol, cyclohexanone, and the imino-tautomeric form of -caprolactam (or caprolactim) was considered in the study. Excellent agreement was found between calculated equilibrium segregation coefficients for the impurity cyclohexanone in the {110} and {111 h} forms of -caprolactam and reported experimental values for crystals grown from the melt in the presence of a wide range of cyclohexanone impurity concentrations, 0.1-30 mol %, for supersaturations of the melt, 2 × 10 -3 to 6 × 10 -3 (van den Berg, E. P. G.; Bögels, G.; Arkenbout, G. J. J. Cryst. Growth 1998, 191, 169-177). It was calculated that the incorporation of cyclohexanol into -caprolactam would be most significant for the {110} form and that the extent of partitioning of cyclohexane into the most important growth forms is 10-100 times smaller than those in the cases of cyclohexanol and cyclohexanone. The effect of impurity incorporation on the habit of -caprolactam crystals was calculated from the modified attachment energies.

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