Sustainable and Rapid Preparation of the High-Performance MOR Zeolite Membrane for Acetic Acid Dehydration under Fluoride-Free Conditions via a Hydroxyl Radical-Promoted Strategy

Abstract

The rapid preparation of high-performance MOR zeolite membranes for the dehydration of high-concentration acetic acid under fluoride-free conditions remains a significant challenge. In this study, a hydroxyl radical-promoted strategy was successfully applied to fabricate high-performance MOR zeolite membranes on macroporous mullite supports within only 3 h, under fluoride-free and organic-template-free conditions. The formation process of MOR zeolite membranes in the presence of hydroxyl radicals was systematically investigated. Furthermore, the roles of hydroxyl radicals and hydroxide ions in the synthesis mechanism of MOR zeolite membranes were discussed in detail using characterization methods such as SEM, XRD, EPR, and fluorescence spectroscopy. Compared with the synthesis system without hydroxyl radical participation, the hydroxyl radical-promoted MOR zeolite membranes not only exhibited a significantly shortened crystallization time but also enabled a reduction in the alkalinity of the reaction system. The membrane prepared under optimal conditions demonstrated excellent separation performance in a 90 wt % acetic acid/water mixture at 75 °C, with a permeation flux as high as 1.37 kg m^–2 h^–1 and a water content in the permeate exceeding 99.4 wt %. Moreover, the MOR zeolite membranes prepared using the hydroxyl radical-promoted strategy showed excellent reproducibility. This hydroxyl radical-promoted approach provides an efficient and environmentally friendly route for the rapid preparation of high-performance zeolite membranes under fluoride-free, template-free, and low-alkalinity conditions.