Advanced Reactive Distillation Concepts for the Indirect Hydration of Cyclohexene to Cyclohexanol

Cyclohexanol is a very important bulk chemical feedstock for the polymer industry, primarily as a precursor to nylon but also a plasticizer component and solvent. The conventional process for cyclohexanol synthesis is either cyclohexane oxidation, hydrogenation of phenol, or the direct hydration of cyclohexene.  The direct hydration route, 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.

An alternative to the direct hydration of cyclohexene is the indirect hydration process where acetic acid is used as the reactive entrainer.  In the first step of this process cyclohexene from the inlet mixture of cyclohexene and cyclohexane reacts with acetic acid to form cyclohexyl acetate, which is hydrolyzed with water to cyclohexanol in the second step.

In this paper we present the reaction of cyclohexene from a mixture of cyclohexene and cyclohexane with acetic acid to form cyclohexyl acetate in the MSU pilot scale reactive distillation column packed with Katapak-SP11 structured packing.   Effect of flow rates, reflux ratio and column geometry have 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.  Additionally, single- and two-phase flow through a Katapak-SP11 structured packing was modeled using ANSYS FLUENT 12.1.  The purpose of this analysis is to determine the liquid flow distributions interior and exterior to the catalyst baskets, catalyst wetting, and hence reaction effectiveness.  Advanced concepts such as heat integration are incorporated into experimental and simulation results.  Plant scale simulations are presented.