Thermally Coupled Reactive Distillation System for the Separations of Cyclohexene/Cyclohexane Mixtures

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• 作者：Jieping Yu ; Li Shi ; Yang Yuan ; Haisheng Chen ; Shaofeng Wang ; Kejin Huang
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2016
• 出版时间：January 13, 2016
• 年：2016
• 卷：55
• 期：1
• 页码：311-322
• 全文大小：832K
• ISSN：1520-5045

文摘

Because of the very close boiling points of cyclohexene and cyclohexane, their separation is extremely difficult with conventional distillation systems and reactive separation with water as reactive entrainer offers great economic incentives. In the current work, the synthesis and design of a flow-sheet with two reactive distillation columns (i.e., the hydration and dehydration reactive distillation columns) in series (FSTRDC) is first conducted subject to the minimization of total annual cost (TAC), and this leads to a process design with an excessive use of water. Although the process design facilitates the hydration of cyclohexene into cyclohexanol, it gives rise to a serious remixing effect in the hydration reactive distillation column and poses an unfavorable effect to the decomposition of cyclohexanol into cyclohexene and water in the dehydration reactive distillation column. For the suppression of these deficiencies, the hydration reactive distillation column was then modified to be heated directly with a vapor flow from the reboiler of the dehydration reactive distillation column, and this gives rise to a novel thermally coupled reactive distillation system (TCRDS). The mass and thermal coupling between these two reactive distillation columns involved eliminates completely the remixing effect and reduces greatly the excessive use of water and enables the TCRDS to require substantially less capital investment (CI), operating cost (OC), and TAC than the FSTRDC. The implementation of the TCRDS in terms of a dividing-wall distillation column is finally highlighted and found to lead to further reductions in the CI and TAC. These striking outcomes demonstrate the great significance of including effective mass and thermal coupling to the two reactive distillation columns in series, reactively separating close boiling binary mixtures.