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The process intensification in carbonylation of formaldehyde by active and passive enhancement was investigated in stirred tank reactor and membrane contactor, respectively. The increase of rotational speed and decrease of reaction solution volume was advantageous to the yield of glycolic acid in active strengthening experiments, indicating that the reaction was greatly affected by the mass transfer of CO. In passive reinforcement mode, the membrane contactor composed of PTFE hollow fibers with inner diameter of 0.85 mm or 0.42 mm was used as a novel reactor to improve the process mass transfer. The effects of reaction temperature, operation pressure, reaction time and reactant concentration were systematically studied. The results showed that membrane contactor was an effective reactor for the carbonylation of formaldehyde compared to the conventional tank reactor. This study provided a reference for the process intensification of similar gas-liquid reactions. [ABSTRACT FROM AUTHOR]

The batch and continuous synthesis of glycolic acid via carbonylation of formaldehyde using high-temperature and high-pressure poly(tetrafluoroethylene) (PTFE) membrane contactor was demonstrated in this paper. The experiments in conventional stirred tank reactor were also conducted for comparison. The results showed that the yield of glycolic acid was significantly improved in membrane contactor system compared to the stirred tank reactor. At reaction temperature of 120 °C and reaction pressure of 5.0 MPa, the yield of glycolic acid was higher than 90% when the reaction time was 1 h, while it was only about 45% in the conventional stirred tank reactor. The enhancement of yield was due to the improvement of mass transfer or dispersion of CO in membrane contactor system, which could provide larger gas-liquid contact area and shorter mass transfer distance. The stability of PTFE hollow fibre membranes was also investigated by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), liquid entry pressure (LEP), bubble point (BP) and contact angle (CA) measurements. The characterizations indicated that PTFE membranes exhibited good chemical and thermal stability in this reaction system. This study provided new idea and reference for the carbonylation of formaldehyde and similar gas-liquid reactions. • Batch and continuous synthesis of glycolic acid via carbonylation of formaldehyde in membrane contactor was demonstrated. • Mass transfer of CO is greatly enhanced in membrane contractor system compared to the conventional tank reactor. • Membrane contactor can provide larger contact area and shorter diffusion path for gas-liquid reaction. • PTFE hollow fibers exhibited good stability under high temperature and high pressure conditions. [ABSTRACT FROM AUTHOR]