Process intensification in catalytic wet air oxidation of phenol via coupling gas-liquid microdispersion with trickle bed reactors

Intensified trickle bed reactors were developed for catalytic wet air oxidation (CWAO) of phenol, by generating microbubbles before gas/liquid fluid flows along catalyst packed-beds. By coupling gas-liquid microdispersion module, phenol disappearance rate significantly increases under the same operating conditions and phenol conversion reaches 92% in 22 seconds at 160°C and 1000 kPa. Effects of operating conditions were studied systematically and results demonstrated characteristics of high-interaction regime at low Reynolds number. Comparison of effects among mass transfer and reaction steps shows CWAO reaction is controlled by resistance to liquid-solid mass transfer of phenol in most cases, while gas-liquid mass-transfer-resistance is ignorable. A dimensionless correlation, Sh = 2.29φ^−0.91(Re_L + Re_G)^0.04, was established, by considering influences of liquid film thickness and fluid flow situations on liquid-solid mass transfer coefficient in microbubble-in-liquid/catalyst-particle system. The study would provide an effective method for intensifying CWAO and other liquid-solid-mass-transfer-resistance-controlled gas/liquid/solid catalytic reactions and help understand mass transfer mechanism in new gas/liquid/solid system.