Mass Transfer Characteristics and Scale-Up of Cumene Oxidation in Continuous-Flow Reactors

Technological upgrades and safe production are critical for cumene oxidation to produce phenol. Despite advancements in continuous-flow synthesis using microfluidics, scalability and productivity remain uncertain. Herein, we propose a strategy to maintain a consistent mass transfer coefficient in scaled-up coiled-tube and pipes-in-series reactors through flow pattern control. The relationship between flow characteristics and mass transfer coefficients under scaled-up conditions were explored, thereby validating the accuracy of mass transfer predictions based on flow pattern, flow velocities, and slug lengths. Reaction conversion and selectivity were confirmed to remain unaffected by a mass transfer coefficient greater than 0.001 m/s. Even in a scaled-up reactor with alternating 4 and 16.05 mm i.d. sections, mass transfer was also effectively accomplished within smaller tubes (4 mm i.d.) by controlling the flow pattern, ensuring sufficient liquid residence time and efficient gas dissolution. A conversion of approximately 64.0%, a yield of 57.3%, and a selectivity of 89.5% were maintained, while productivity increased 132-fold compared to the 0.6 mm i.d. reactor, reaching 88.4 t/a. The operational stability of the high-throughput pipes-in-series reactor was also verified.