Catalytic oxidation of crotonaldehyde to crotonic acid in a gas-liquid-solid mini-fluidized bed

Abstract

Oxidation of crotonaldehyde to crotonic acid is an important chemical reaction process because crotonic acid, its derivative and copolymer are ubiquitous in the productions of chemical, cosmetic, and medicines. However, the reactor safety and process efficiency are still not satisfactory. In order to solve such problems, a novel reactor of gas-liquid-solid mini-fluidized bed with bed inner diameter of 3 mm was developed to carry out the selective catalytic oxidation reaction. The effects of operation conditions and solid particle properties on the conversion rate of reactant crotonaldehyde and the selectivity of product crotonic acid were investigated. The causes of these effects are explained from the standpoint of residence time and gas-liquid mass transfer flux. Moreover, the comparison of reactor performance between the three-phase mini-fluidized bed and the batch stirred tank reactor as a traditional one was made to evaluate the performance of such a reactor. Experimental results show that the average reaction or conversion rate of the mini-fluidized bed is about 30 times much higher than that of batch stirred tank reactor to evaluate the improved performance. But the selectivity is less affected by the operation conditions and solid particle bed properties. The size reduction of three-phase mini-fluidized bed decreases the mass transfer distance of molecular diffusion, and the solid particles and mini-bubbles not only provide the higher specific interface area but also cause hydrodynamics changes that is to intensify the interface disturbance, which effectively accelerate the mass transfer.