Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Ethanol and Water Adsorption in Conventional and Hierarchical All-Silica MFI Zeolites

Published

Author(s)

Swagata Pahari, Matheus Dorneles de Mello, Mansi Shah, Tyler Josephson, Huong Giang Nguyen, Limin Ren, Roger D. van Zee, Michael Tsapatsis, J. Ilja Siepmann

Abstract

Hierarchical zeolites containing both micro- (<2 nm) and mesopores (2−50 nm) have gained increasing attention in recent years because they combine the intrinsic properties of conventional zeolites with enhanced mass transport rates due to the presence of mesopores. The structure of the hierarchical self-pillared pentasil (SPP) zeolite is of interest because all-silica SPP consists of orthogonally intergrown single-unit-cell MFI nanosheets and contains hydrophilic surface silanol groups on the mesopore surface while its micropores are nominally hydrophobic. Therefore, the distribution of adsorbed polar molecules, like water and ethanol, in the meso- and micropores is of fundamental interest. Here, molecular simulation and experiment are used to investigate the adsorption of water and ethanol on SPP. Vapor-phase single-component adsorption shows that water occupies preferentially the mesopore corner and surface regions of the SPP material at lower pressures (P/P0 < 0.5) while loading in the mesopore interior dominates adsorption at higher pressures. In contrast, ethanol does not exhibit a marked preference for micro- or mesopores at low pressures. Liquid-phase adsorption from binary water−ethanol mixtures demonstrates a 2 orders of magnitude lower ethanol/water selectivity for the SPP material compared to bulk MFI. For very dilute aqueous solutions of ethanol, the ethanol molecules are mostly adsorbed inside the SPP micropore region due to stronger dispersion interactions and the competition from water for the surface silanols. At high ethanol concentrations (CEtOH > 700 g L−1), the SPP material becomes selective for water over ethanol.
Citation
ACS Physical Chemistry Au

Keywords

adsorption, hierarchical zeolite, singe-unit-cell, self-pillared pentasil

Citation

Pahari, S. , Dorneles de Mello, M. , Shah, M. , Josephson, T. , Nguyen, H. , Ren, L. , van Zee, R. , Tsapatsis, M. and Siepmann, J. (2021), Ethanol and Water Adsorption in Conventional and Hierarchical All-Silica MFI Zeolites, ACS Physical Chemistry Au, [online], https://doi.org/10.1021/acsphyschemau.1c00026 (Accessed April 20, 2024)
Created November 16, 2021, Updated May 9, 2023