Mass transfer - reaction coupling simulation study of lower aliphatic carboxylic aldehyde oxidation process in gas-liquid reactor

Abstract

This paper takes the oxidation of lower aliphatic carboxylic aldehydes, such as n-butyraldehyde, as a representative example and establishes a mass transfer-reaction coupling model for the oxidation process in a gas-liquid reactor. The dynamic balance between oxygen supply and reaction consumption is described using volumetric mass transfer coefficient, oxygen partial pressure, Arrhenius kinetics, and competing side reactions. Furthermore, the average bubble diameter, gas holdup, and pressure drop parameters of the gas distribution material are introduced to simulate the effects of single-hole stainless steel distributors, ceramic microporous plates, PVDF hydrophobic membranes, and SiO2-Al2O3 micro/nano distributors on reaction performance. The results show that under baseline conditions, the aldehyde conversion rate is 77.2%, the target acid selectivity is 86.4%, and the target acid yield is 66.8%. When k L a increases from 0.25 min -1 to 1.40 muri, the target acid yield increases from 37.1% to 68.8%, but the gain decreases significantly after further increasing the mass transfer capacity. Increasing the temperature can enhance the conversion, but above 80 °C, side reactions accelerate and selectivity decreases. Materials simulations show that the SiO2-Al2O3 micro/nano distributor achieves a k L a of 1.46 min -1 and a target acid yield of 68.9% due to bubble refinement and increased gas holdup, but the pressure drop also increases simultaneously.