Analysis of Phase Equilibrium Diagrams of Cyclohexene + Water + Cyclohexanone + Solvent System

Abstract

Vapor−liquid and liquid−liquid equilibrium of quaternary systems that can form in the production of cyclohexanone by oxidation of cyclohexene in the presence of different solvents water + dimethylformamide (dimethyl sulfoxide, dimethylacetamide) were studied using mathematic modeling and NRTL model. The experimental and calculated data were found to be in a good agreement. The analysis of phase diagrams showed that the simplest diagram (two binary szeotropes and one distillation region) is observed for systems containing dimethyl sulfoxide and dimethylacetamide. It makes possible to separate cyclohexanone from catalyst and high boiling solvents by distillation.

Phase Equilibrium of Systems Cyclohexene + Water + Cyclohexanone + N-Methyl-2-pyrrolidone (+Acetonitrile)

“…(CHON of obtained quality can be used for the production of caprolactam) was proved using mathematical modeling in Aspen Plus. The advantages of NMP using are: a simple structure of the phase diagram (compared to a system that uses only AN , ), a high boiling point (compared to AN , ), thermal stability (compared to dimethylsulfoxide), a high value of relative volatility in the mixture with CHON (compared to dimethylsulfoxide), no limitations in the composition of the initial mixture for the flowsheet proposed. The reaction mixture with binary solvent NMP + AN can also be separated using this method, but there are limitations on the composition of the initial mixture, in particular, the reaction should be carried out in excess of AN with respect to NMP (3/1 and above) to get CHON of commercial quality.…”

“…Acetonitrile (AN) was used as solvent for reaction. However, the presence of AN complicates the separation flowsheet because of a number of azeotropes (three binary and one ternary) and region of three liquid phases (the distribution of catalyst between the liquid layers). − CHON having the highest boiling temperature (428.55 K) is always presented as a bottom product that negatively affects its purity. An attempt to replace AN with other solvents: dimethylsulfoxide, dimethylformamide, or dimethylacetamide were made .…”

“…However, the presence of AN complicates the separation flowsheet because of a number of azeotropes (three binary and one ternary) and region of three liquid phases (the distribution of catalyst between the liquid layers). − CHON having the highest boiling temperature (428.55 K) is always presented as a bottom product that negatively affects its purity. An attempt to replace AN with other solvents: dimethylsulfoxide, dimethylformamide, or dimethylacetamide were made . Despite the fact that dimethylsulfoxide has shown good results (this solvent has the high boiling temperature and doesnot form new azeotroped), the separation flowsheets will always contain the column (of CHON + dimethylsulfoxide mixture separation), operating at reduced pressure because of the thermal instability of the solvent.…”

“…It was suggested to use N -methyl-2-pyrrolidone (NMP) or binary mixture AN + NMP. NMP satisfies the requirements imposed on the solvent . Despite the fact that AN remains in the reaction system, we assume that the addition of heavy boiling NMP will solve the problem of isolation of the target product of the required quality.…”

“…The method of studying is mathematical modeling using Aspen Plus V.10.0. The parameters of the nonrandom two-liquid (NRTL) model were taken from literature. , The missing parameters were regressed on the basis of available experimental data and are presented in the paper.…”