Nonideality in the Adsorption of Ethanol/Ethyl Acetate/Water Mixtures On ZIF-8 Metal Organic Framework

Abstract

Fisher esterification of acetic acid (or acetic anhydride) with ethanol (EtOH) is the main industrial process for the synthesis of ethyl acetate (EA). Nonetheless, the separation of the produced ester from ethanol is challenging since these volatile organic compounds (VOCs) form an azeotropic mixture. In this work, the adsorption and separation EtOH/EA/water mixtures on the ZIF-8 metal−organic framework is studied. The present study aims to characterize the adsorptive behavior of ZIF-8 with non-ideal EtOH/EA/ water mixtures. Single and multicomponent adsorption isotherms, obtained by gravimetry and breakthrough experiments, show high adsorption capacity and selectivity toward ethyl acetate. Pulse chromatography experiments confirm the higher interaction strength between EA and ZIF-8 in the low-pressure range at a low degree of pore filling (Henry's region). The breakthrough profiles show development of intermediate plateaus in specific concentration ranges, with complex breakthrough evolution that has been modeled using a combined ideal and real adsorption solution theory model to accounts for deviations from ideality.

Inherent Ethyl Acetate Selectivity in a Trianglimine Molecular Solid

“… [15] The IAST‐predicted selectivity is shown in Figure 2 b for binary mixtures of EA‐EtOH with compositions of 50 : 50 and 5 : 95 at 298 K. For equimolar mixtures, the initially predicted selectivity was 39.4, and then gradually decreased to 10.6 at 0.1 bar; this is much higher than the selectivity reported for ZIF‐8 (1.7–8.3) under the same conditions calculated by the same method. [3] Even for the 5 : 95 EA‐EtOH binary mixture, EA is still predicted to be preferentially captured by TAMC (Figure 2 b, solid dots).…”

“…Fisher esterification of ethanol (EtOH) is the main industrial process for synthesizing EA. The subsequent separation of EA from EtOH is difficult because they have similar boiling points (78.5 °C and 77.1 °C, respectively); also, EA and EtOH form azeotropic mixtures [3] . Current purification techniques include extractive distillation, [4] azeotropic distillation using ionic liquids, [5] and membrane separation, [6] but these can be inefficient and energy‐intensive.…”

“…The subsequent separation of EA from EtOH is difficult because they have similar boiling points (78.5 °C and 77.1 °C, respectively); also, EA and EtOH form azeotropic mixtures. [3] Current purification techniques include extractive distillation, [4] azeotropic distillation using ionic liquids, [5] and membrane separation, [6] but these can be inefficient and energy‐intensive. There is potential to find alternative separation processes based on selective adsorption using microporous materials that can operate under atmospheric conditions.…”

Metal-Organic Frameworks Characterization via Inverse Pulse Gas Chromatography

“…In another study [70], the adsorption and separation of ethanol/ethyl acetate (EA)/water mixtures, formed during an industrial process for the synthesis of EA, were studied on ZIF-8. Single-and multicomponent isotherms of adsorption, acquired via gravimetric and breakthrough experiments, showed high adsorption ability and selectivity to EA.…”

Evaluation of ZIF-8 and ZIF-90 as Heat Storage Materials by Using Water, Methanol and Ethanol as Working Fluids

“…However, the ZIF-8 monolith using a single modulating ligand and both ZIF-67 monoliths showed a significant improvement in the uptake of methanol and toluene, favouring toluene [10]. Many studies have examined the alcohol adsorption of ZIFs for applications such as organic vapour recovery, indoor air cleaning, adsorption-based heat pumps and separation/selectivity in alcohols [6,10,[15][16][17][18][19].…”