Catalytic distillation for ethyl acetate synthesis using microfibrous-structured Nafion-SiO₂/SS-fiber solid acid packings

Catalytic distillation (CD) offers a unique integration of distillation and catalysis to selectively separate products in situ while making a positive shift of chemical equilibrium and has therefore been well received as an inviting avenue to green chemical processing. Rendering novel structured catalytic packings is particularly desirable but remains challenging. Herein, we present a microfibrous-structured Nafion-SiO₂/SS-fiber solid acid catalyst and demonstrate its separation and reaction efficiency as CD packings for esterification to produce ethyl acetate from acetic acid and ethanol. A thin-sheet microfibrous structure with 15 vol% 20 μm stainless steel fibers (SS-fiber) and 85 vol% void volume was shaped into θ-ring analogues. Nafion was then firmly locked into the SiO₂ layer that was anchored onto the SS-fiber surface by a dip-coating method using self-crosslinking Nafion-SiO₂ sol-gel prepared by Nafion-catalyzed hydrolysis of tetraethylorthosilicate (TEOS). Such micro-structured Nafion catalysts worked effectively and efficiently in the CD for esterification of acetic acid with ethanol as the result of a unique combination of high catalyst performance (stability, adequate acidic sites and high mass/heat transfer) and instantaneous distillation. For instance, high total (93.6%) and actual (91.6%) yields of ethyl acetate with 96.2% purity were achievable at a high space-Time yield (4.3 g mmol^-1 h^-1) while the high CD efficiency was maintained for 40 h over 5 consecutive batch runs.