Novel SPVA/g-C3N4-SA/PAN Pervaporation Membranes with Porous Catalytic Layers for Esterification Enhancement

Abstract

The pervaporation membrane technology integrated with catalytic function improves the conversion of esterification reactions by integrating reaction and separation processes in a single step. Optimizing the structure of the catalytic layer of the pervaporation membrane can effectively reinforce its enhancement effect on the esterification reaction. Here, a porous catalytic layer with high catalytic activity and low mass transfer resistance was successfully developed by the immersion phase inversion. The sulfonated poly(vinyl alcohol) (SPVA) catalytic layer prepared by cross-linking poly(vinyl alcohol) (PVA) with 5-sulfosalicylic acid (SSA) was coated on a graphitic carbon nitride-sodium alginate (g-C₃N₄-SA) membrane with polyacrylonitrile (PAN) as the support. The prepared pervaporation membranes with a porous catalytic layer were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). The membrane catalytic performance was evaluated in the esterification reaction of acetic acid with ethanol in a pervaporation catalytic membrane reactor (PVCMR). As a result, the acetic acid conversion was up to 98.4% in 12 h at 75 °C with 20% molar fraction of the catalyst. Compared with the batch reaction (BR) under the same operating conditions, the acetic acid conversion rate was greatly improved by 24.4%. After five runs, the membrane still maintained excellent stability. In addition, the resistance-in-series model was considered to analyze the mass transfer resistance of the membrane. The results indicated that the porous catalytic layer had a lower mass transfer resistance of 1.38 × 10⁵ s·m–¹, accounting for only 46.1% of the overall resistance, while the dense catalytic layer accounted for 66.9%. Therefore, the pervaporation membrane with a porous catalytic layer presented great ability for enhancing the esterification reaction of acetic acid with ethanol.