Macroscopic and Microscopic View of Competitive and Cooperative Adsorption of Alcohol Mixtures on ZIF-8

Abstract

While in most adsorptive separations different mixture components tend to compete for different adsorption sites, we report the existence of cooperative effects in the adsorption of alcohols (ethanol and 1-butanol) from the vapor phase on ZIF-8. The presence of these molecules in binary mixtures leads to an increase in their equilibrium capacities, compared to the pure component isotherms. These effects were first observed when predicting the mixture equilibrium capacities using the ideal adsorbed solution theory (IAST) and were also observed via grand canonical Monte Carlo (GC MC) simulations. GC MC simulations showed that the interaction between adsorbate molecules leads to the cooperative effect predicted by IAST. The predicted cooperative adsorption could be confirmed via breakthrough experiments. In these experiments, a "roll-up" of 1-butanol was observed during the regeneration of a ZIF-8 packed column. A dynamic breakthrough model employing IAST was developed and used to explain the effect of the adsorption equilibrium on the dynamic breakthrough profiles.

Recycling Plastic Waste for Environmental Remediation in Water Purification and CO2 Capture

“…To predict the adsorption behavior of a mixed gas, the ideal CO 2 /N 2 selectivity was calculated based on the framework of the ideal adsorbed solution theory (IAST) developed by Myers and Prausnitz . This model has been widely utilized in process simulation and adsorbent selection. − The equations used can be found in the Supporting Information.…”

Water/Alcohol Mixture Adsorption in Hydrophobic Materials: Enhanced Water Ingress Caused by Hydrogen Bonding

“…In the production of bioalcohols by fermentation of biomass, the desired products such as bioethanol and biobutanol are available in low concentrations in the fermentation broth; consequently, distillation separations are infeasible. One separation strategy is to use fixed bed adsorption devices packed with hydrophobic microporous materials, such as all-silica MFI (also called silicalite-1), ZIF-8, ZIF-71, and MOFs. − The separation efficacy of fixed bed adsorbers is dictated by a combination of mixture adsorption equilibrium and intracrystalline diffusion of guest molecules.…”

3D-Printed ZIF-8 Monoliths for Biobutanol Recovery

“…To investigate this phenomenon more closely, single component breakthrough experiments were carried out with a fixed partial pressure of n- butanol and a varying flow rate, of which the results are shown in Figure . For both monoliths, the typical double step breakthrough profile can be observed, which has been reported before ,,, and is a consequence of the type V isotherm shape of alcohols on ZIF-8: the breakthrough profile consists of the combination of a “dispersive” and “shock” wave. Due to the difference in experimental conditions (temperature, n- butanol partial pressure, pure component vs mixture) between the breakthrough curves presented in Figure and Figure , this step is much less pronounced in the mixture breakthrough experiments (Figure ) but is visible when zooming-in on the breakthrough curves (Figure S15).…”