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

Abstract

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-SiO 2 /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 SiO 2 layer that was anchored onto the SS-fiber surface by a dip-coating method using self-crosslinking Nafion-SiO 2 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.React. Chem. Eng. This journal is

Catalytic distillation for esterification of acetic acid with ethanol: promising SS‐fiber@HZSM‐5 catalytic packings and experimental optimization via response surface methodology

“…The high total yield (95.9%) and actual yield (90.9%) of ethyl acetate with a high STY of 1.25 g g zeolite ‐1 h ‐1 could be achievable for our microfibrous‐structured SS‐fiber@HZSM‐5 (50) catalyst in CD process using the molar ratio of acetic acid to ethanol in the flask of 1:1.2 (Fig. S9), which is consistent with our previous work using Nafion‐SiO 2 /SS‐fiber CD packings . The experimental values were in good agreement with the ones predicted from the models, and hence the projected statistical models were suitable to predict the yield and purity of ethyl acetate in CD process.…”

“…S9), which is consistent with our previous work using Nafion-SiO 2 /SS-fiber CD packings. 39 The experimental values were in good agreement with the ones predicted from the models, and hence the projected statistical models were suitable to predict the yield and purity of ethyl acetate in CD process.…”

“…Such microfibrous support can be made into thin sheets of large area and/or a pleated sheet structure to control pressure drop and improve the efficiency of contact between reactant and catalyst, different from other traditionally employed contacting schemes such as honeycomb monoliths, wovens, and grids . Recently, a microfibrous‐structured Nafion‐SiO 2 /SS‐fiber catalyst was designed and tailored for the CD process, which demonstrates high separation and reaction efficiency as CD packing for esterification to produce ethyl acetate from acetic acid and ethanol. However, the solid acid Nafion suffers from excessive exfoliation after experiencing a long time reaction, and therefore, it is hoped to monolithically structure stable solid acids (such as HZSM‐5) onto metal microfibers to fabricate structured catalysts of Nafion‐SiO 2 /SS‐fiber.…”

Response Surface Methodology Optimization of Friedel–Crafts Acylation Using Phosphotungstic Acid Encapsulation in a Flexible Nanoporous Material

“…The Friedel–Crafts acylation of phenols and acyl chlorides yields ortho - and para -hydroxy acetophenones (2-HAP and 4-HAP), which are very valuable precursors in the pharmaceutical industry. − Lewis acids (AlCl 3 , BF 3 ) or mineral acids (HF or H 2 SO 4 ) as conventional homogeneous catalysts, which have been widely used in such reactions, have serious drawbacks. , In homogeneous catalyst systems, the purification of products and separation and recovery of the catalyst at the end of the reaction are very difficult, time-consuming, and costly. − It is worth mentioning that the replacement of these conventional catalysts by heterogeneous reusable acid catalysts is promising . The heterogeneous catalysts have advantages such as easy separation of the catalyst from the reaction mixture, reusability of the catalyst, environmental protection, and economic efficiency. − Zeolite, , sulfonic acid-modified mesostructured SBA-15 materials, and other acidic heterogeneous catalysts such as the sulfonic resin Nafion have been studied as catalytic systems in the Friedel–Crafts acylation. In this sense, rapid deactivation of zeolites and limited specific surface areas for sulfonic resin Nafion and SBA-15 encourage researchers to find more applicable catalysts.…”

Facile Synthesis of Homogeneous Catalyzed Esterification of Medium-Chain-Length Fatty Acids and Kinetic Study

“…The drawbacks of using solid acid catalyst are pessimistic expectations (large interconnected pores reducing the diffusion rate of molecules) and unfavorable side reactions . Owing to the fact that the esterification reaction is reversible, efficient strong homogeneous catalysts (sulfuric acid, hydrochloric acid, or organic acids) are required to shift the equilibrium to get the desired products. − Although there are considerable drawbacks to using homogeneous catalyst, i.e., corrosion to the equipment and difficulty of catalyst separation, they are preferred due to being inexpensive, more active, and more efficient, giving a higher conversion of esters.…”