Membrane contactor is regarded as a promising method for reaction and process intensification. The feasibility of formaldehyde carbonylation to synthesize glycolic acid using polytetrafluoroethylene (PTFE) membrane contactor has been proved in our previous study. In this paper

the effect of membrane microstructure on process performance was further investigated. Three porous PTFE hollow fibers with different pore sizes and one polydimethylsiloxane (PDMS)/PTFE composite membrane with dense layer were fabricated for comparison. The physical and chemical properties of four membranes

including chemical composition

morphology

contact angle

liquid entry pressure

thermodynamic analysis and gas permeability

were systemically characterized. Experiments of formaldehyde carbonylation under different reaction conditions were conducted. The results indicated that the yield of glycolic acid increased with decreasing pore size for porous membranes

which was due to the improvement of wetting behavior. The dense layer of PDMS in composite hollow fiber could effectively prevent the solvent from entering membrane pores

thus the membrane exhibited the best performance. At reaction temperature of 120 ℃ an

d operation pressure of 3.0 MPa

the yield of glycolic acid was always higher than 90% as the mass ratio of trioxane and phosphotungstic acid increased from 0.2:1 to 0.8:1. The highest turnover frequency was up to 26.37 mol·g

-1

·h

-1

. This study provided a reference for the understanding and optimization of membrane contactors for the synthesis of glycolic acid using solvent with low surface tension.