Modeling of Secondary Alcohols Dehydration under Hydrothermal Conditions (Cis-3-tert Butyl Cyclohexanol to Trans-4-tert-Butylcyclohexene)

Abstract

Hydrothermal dehydration provides a catalyst-free route for converting cis-3-tert-butylcyclohexanol to trans-4-tert-butylcyclohexene while reducing the corrosion and downstream separation demands associated with conventional acid-catalysed processes. This study develops a kinetic–thermal model of the reaction using coupled material and energy balances for a continuous stirred-tank reactor. The reaction is represented as a reversible consecutive pathway in which the alcohol forms a carbocation intermediate before generating the alkene product. The governing equations were implemented in MATLAB-Simulink and solved using a variable-step stiff ordinary differential equation solver. The simulation showed that the alcohol concentration decreased from 2.5000 to 0.2500 mol m⁻³ as fractional conversion increased to 0.9000. A space time of 65.0289 h was required to reach 90% conversion, while the alkene concentration and yield reached 1.6016 mol m⁻³ and 0.6406, respectively. Most product formation occurred within approximately 30 h, after which additional residence time produced smaller gains in yield. The predicted reactor temperature decreased from 523.3934 K to a minimum of 523.0787 K at 80% conversion, followed by a slight increase to 523.0983 K at 90% conversion. The results demonstrate the model’s capacity to describe reactant depletion, intermediate behaviour, product formation, reactor-volume demand, and temperature variation. Experimental validation is required before the model is used for process design or scale-up.