Process Optimization and Reaction Kinetic Study of Propylene Glycol Butyl Ether Synthesis from Propylene Oxide in a Microreactor

Abstract

Propylene glycol butyl ether (PNB) is an important environmentally friendly solvent widely used in coatings, inks, and cleaning agents. Its industrial production typically relies on batch processes that suffer from low efficiency and safety concerns. This study proposes a continuous-flow etherification reaction of propylene oxide (PO) with n-butanol in a microreactor to achieve process intensification and improved safety. First, a Bayesian optimization method based on Gaussian processes was employed to systematically optimize key reaction parameters, including temperature, residence time, and reactant molar ratio. An apparent kinetic model of the reaction was further established. By coupling the kinetic model with the heat balance equation, the temperature distribution and yield variation under different channel dimensions and materials were simulated and predicted. The results indicate that under optimal conditions, the yield of PNB can reach 92.75%. Kinetic studies showed that the reaction follows first-order kinetics with respect to propylene oxide, with an activation energy of 42.16 kJ·mol^–1. In a 1/8-in. FEP microchannel, the temperature rise was only 1.0 °C, confirming near-isothermal operation. However, increasing the channel diameter to 1/2 in. led to a temperature rise of 25.8 °C, introducing significant thermal risk. Replacing FEP with high-thermal-conductivity materials such as stainless steel effectively suppressed the temperature rise, though with a slight reduction in yield. This work demonstrates that microreactors offer excellent heat transfer control for exothermic etherification reactions. The integrated approach combining Bayesian optimization, kinetic modeling, and thermal simulation provides a useful framework for developing safe and efficient continuous-flow processes. The findings also offer practical guidance for reactor design and scale-up.