(709d) Heat Integrated Reactive Distillation for the Indirect Hydration of Cyclohexene to Cyclohexanol

Cyclohexanol is an important bulk chemical feedstock for the polymer industry, primarily as a precursor to nylon, but also as a plasticizer component and solvent. The conventional process for cyclohexanol synthesis is either cyclohexane partial oxidation, hydrogenation of phenol, or the direct hydration of cyclohexene.  The direct hydration route of cyclohexene to form cyclohexanol, which is the simplest in principle, suffers from limited solubilities of the cyclohexene-water pair, thus requiring large amounts of catalyst and high residence times with intense mixing, and process chilling.

An alternative to the direct hydration of cyclohexene is the two-stage indirect hydration process employing heat-integrated reactive distillation.  The justification for a two-stage operation employing (1) esterification and (2) hydrolyzation builds upon the earlier studies by Sundmacher, et al., [1]   Here acetic acid is used as the reactive entrainer in a reactive distillation operation.  In the first stage of this process cyclohexene from the inlet mixture of cyclohexene and cyclohexane reacts with acetic acid to form cyclohexyl acetate, which is then hydrolyzed with water to form cyclohexanol in the second stage.  In this study, the heat-integration will improve yields from the operation.

We present the results of a reaction of cyclohexene in a mixture of cyclohexene and cyclohexane with acetic acid to form cyclohexyl acetate.  This reaction is carried out using the MSU pilot scale reactive distillation column packed with Katapak-SP11 structured packing.   The effect of flow rates, reflux ratio, and column geometry has been experimentally investigated.  Column performance is predicted using RADFRAC in Aspen Plus process simulation software with appropriate kinetic parameters derived from experimental batch kinetic studies.  Kinetic parameters have been estimated using a LHHW model.  Reactive residue curve maps have been presented along with plant scale simulations.

[1] Steyer, Frank and Kai Sundmacher, Cyclohexanol Production via Esterification of Cyclohexene with Formic Acid and Subsequent Hydration of the Esters Reaction Kinetics, Ind. Eng. Chem. Res. 2007, 46, 1099-1104