Framework water capacity and infiltration pressure of MFI zeolites

Thomas Humplik; Rishi Raj; Shalabh C. Maroo; Tahar Laoui; Evelyn N. Wang

doi:10.1016/j.micromeso.2014.01.026

Framework water capacity and infiltration pressure of MFI zeolites

Thomas Humplik, Rishi Raj, Shalabh C. Maroo, Tahar Laoui, Evelyn N. Wang^*

^*Corresponding author for this work

King Fahd University of Petroleum & Minerals

Research output: Contribution to journal › Article › peer-review

24 Scopus citations

Abstract

The high specific surface area and sub-nanometer to nanometer pore dimensions of microporous materials (pores <2 nm) can be exploited to improve a variety of applications such as separation technologies, energy storage, and fuel cells. For example, the ≈5.5 Å diameter pore of MFI (Mobil Five) zeolites has been proposed as a molecular sieve for water-based separation techniques. However, results from past experimental and simulation studies have been inconsistent, even for basic quantities such as the framework water capacity and the pressure at which the MFI zeolite pores become water-saturated (infiltration pressure). In this work, we elucidate the underlying mechanisms behind such discrepancies via combined water adsorption and high-pressure infiltration (or intrusion) experiments on various MFI zeolites where the characteristic crystal dimension was varied from nano (≈10 nm) to micro (≈10 μm) scales. Detailed characterization techniques were utilized to demonstrate the presence of non-crystalline silica regions in <100 nm zeolites. Accordingly, an estimated decrease of up to 50% in the framework water capacity was observed for these zeolites when compared to the fully-crystallized larger zeolites, where 35 ± 2 water molecules were required to saturate a unit cell. On the other hand, the water infiltration pressure for all of the zeolites was ≈95-100 MPa despite the differences in the synthesis procedure, indicating uniformity in the crystallized pore structure and surface chemistry. These results are an essential first step towards investigating water transport mechanisms within the sub-nanometer pores and can be used to validate and improve upon existing molecular simulations in order to obtain design guidelines for practical applications such as water-based separation technologies.

Original language	English
Pages (from-to)	84-91
Number of pages	8
Journal	Microporous and Mesoporous Materials
Volume	190
DOIs	https://doi.org/10.1016/j.micromeso.2014.01.026
State	Published - 15 May 2014

Bibliographical note

Funding Information:
We thank Prof. Michael Tsapatsis (University of Minnesota) and Prof. Rohit Karnik (MIT) for helpful discussions and advice. We also thank Dr. Sonjong Hwang of the Solid State NMR group at the California Institute of Technology for performing the NMR experiments and analysis and Dr. Machteld Mertens (ExxonMobil, Belgium) for providing the large MFI 12,000 zeolite sample. Additionally, we thank Pierce Hayward of the Mechanical Engineering Department at MIT, the staff at the Center for Materials Science and Engineering at MIT, and the staff at the Institute for Soldier Nanotechnologies at MIT for the training and use of equipment. This work was performed in part at the Center for Nanoscale Systems (CNS), a member of the National Nanotechnology Infrastructure Network (NNIN), which is supported by the National Science Foundation under NSF award no. ECS-0335765. CNS is part of Harvard University. This work was funded by the King Fahd University of Petroleum and Minerals in Dhahran, Saudi Arabia through the Center for Clean Water and Clean Energy at MIT and KFUPM. R.R. acknowledges fellowship support from Battelle’s National Security Global Business.

Keywords

Adsorption
Hydrophobicity
MFI zeolite
Textural porosity
Water infiltration

ASJC Scopus subject areas

General Chemistry
General Materials Science
Condensed Matter Physics
Mechanics of Materials

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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10.1016/j.micromeso.2014.01.026

Cite this

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title = "Framework water capacity and infiltration pressure of MFI zeolites",

abstract = "The high specific surface area and sub-nanometer to nanometer pore dimensions of microporous materials (pores <2 nm) can be exploited to improve a variety of applications such as separation technologies, energy storage, and fuel cells. For example, the ≈5.5 {\AA} diameter pore of MFI (Mobil Five) zeolites has been proposed as a molecular sieve for water-based separation techniques. However, results from past experimental and simulation studies have been inconsistent, even for basic quantities such as the framework water capacity and the pressure at which the MFI zeolite pores become water-saturated (infiltration pressure). In this work, we elucidate the underlying mechanisms behind such discrepancies via combined water adsorption and high-pressure infiltration (or intrusion) experiments on various MFI zeolites where the characteristic crystal dimension was varied from nano (≈10 nm) to micro (≈10 μm) scales. Detailed characterization techniques were utilized to demonstrate the presence of non-crystalline silica regions in <100 nm zeolites. Accordingly, an estimated decrease of up to 50\% in the framework water capacity was observed for these zeolites when compared to the fully-crystallized larger zeolites, where 35 ± 2 water molecules were required to saturate a unit cell. On the other hand, the water infiltration pressure for all of the zeolites was ≈95-100 MPa despite the differences in the synthesis procedure, indicating uniformity in the crystallized pore structure and surface chemistry. These results are an essential first step towards investigating water transport mechanisms within the sub-nanometer pores and can be used to validate and improve upon existing molecular simulations in order to obtain design guidelines for practical applications such as water-based separation technologies.",

keywords = "Adsorption, Hydrophobicity, MFI zeolite, Textural porosity, Water infiltration",

author = "Thomas Humplik and Rishi Raj and Maroo, \{Shalabh C.\} and Tahar Laoui and Wang, \{Evelyn N.\}",

note = "Funding Information: We thank Prof. Michael Tsapatsis (University of Minnesota) and Prof. Rohit Karnik (MIT) for helpful discussions and advice. We also thank Dr. Sonjong Hwang of the Solid State NMR group at the California Institute of Technology for performing the NMR experiments and analysis and Dr. Machteld Mertens (ExxonMobil, Belgium) for providing the large MFI 12,000 zeolite sample. Additionally, we thank Pierce Hayward of the Mechanical Engineering Department at MIT, the staff at the Center for Materials Science and Engineering at MIT, and the staff at the Institute for Soldier Nanotechnologies at MIT for the training and use of equipment. This work was performed in part at the Center for Nanoscale Systems (CNS), a member of the National Nanotechnology Infrastructure Network (NNIN), which is supported by the National Science Foundation under NSF award no. ECS-0335765. CNS is part of Harvard University. This work was funded by the King Fahd University of Petroleum and Minerals in Dhahran, Saudi Arabia through the Center for Clean Water and Clean Energy at MIT and KFUPM. R.R. acknowledges fellowship support from Battelle{\textquoteright}s National Security Global Business. ",

year = "2014",

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day = "15",

doi = "10.1016/j.micromeso.2014.01.026",

language = "English",

volume = "190",

pages = "84--91",

journal = "Microporous and Mesoporous Materials",

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T1 - Framework water capacity and infiltration pressure of MFI zeolites

AU - Humplik, Thomas

AU - Raj, Rishi

AU - Maroo, Shalabh C.

AU - Laoui, Tahar

AU - Wang, Evelyn N.

N1 - Funding Information: We thank Prof. Michael Tsapatsis (University of Minnesota) and Prof. Rohit Karnik (MIT) for helpful discussions and advice. We also thank Dr. Sonjong Hwang of the Solid State NMR group at the California Institute of Technology for performing the NMR experiments and analysis and Dr. Machteld Mertens (ExxonMobil, Belgium) for providing the large MFI 12,000 zeolite sample. Additionally, we thank Pierce Hayward of the Mechanical Engineering Department at MIT, the staff at the Center for Materials Science and Engineering at MIT, and the staff at the Institute for Soldier Nanotechnologies at MIT for the training and use of equipment. This work was performed in part at the Center for Nanoscale Systems (CNS), a member of the National Nanotechnology Infrastructure Network (NNIN), which is supported by the National Science Foundation under NSF award no. ECS-0335765. CNS is part of Harvard University. This work was funded by the King Fahd University of Petroleum and Minerals in Dhahran, Saudi Arabia through the Center for Clean Water and Clean Energy at MIT and KFUPM. R.R. acknowledges fellowship support from Battelle’s National Security Global Business.

PY - 2014/5/15

Y1 - 2014/5/15

N2 - The high specific surface area and sub-nanometer to nanometer pore dimensions of microporous materials (pores <2 nm) can be exploited to improve a variety of applications such as separation technologies, energy storage, and fuel cells. For example, the ≈5.5 Å diameter pore of MFI (Mobil Five) zeolites has been proposed as a molecular sieve for water-based separation techniques. However, results from past experimental and simulation studies have been inconsistent, even for basic quantities such as the framework water capacity and the pressure at which the MFI zeolite pores become water-saturated (infiltration pressure). In this work, we elucidate the underlying mechanisms behind such discrepancies via combined water adsorption and high-pressure infiltration (or intrusion) experiments on various MFI zeolites where the characteristic crystal dimension was varied from nano (≈10 nm) to micro (≈10 μm) scales. Detailed characterization techniques were utilized to demonstrate the presence of non-crystalline silica regions in <100 nm zeolites. Accordingly, an estimated decrease of up to 50% in the framework water capacity was observed for these zeolites when compared to the fully-crystallized larger zeolites, where 35 ± 2 water molecules were required to saturate a unit cell. On the other hand, the water infiltration pressure for all of the zeolites was ≈95-100 MPa despite the differences in the synthesis procedure, indicating uniformity in the crystallized pore structure and surface chemistry. These results are an essential first step towards investigating water transport mechanisms within the sub-nanometer pores and can be used to validate and improve upon existing molecular simulations in order to obtain design guidelines for practical applications such as water-based separation technologies.

AB - The high specific surface area and sub-nanometer to nanometer pore dimensions of microporous materials (pores <2 nm) can be exploited to improve a variety of applications such as separation technologies, energy storage, and fuel cells. For example, the ≈5.5 Å diameter pore of MFI (Mobil Five) zeolites has been proposed as a molecular sieve for water-based separation techniques. However, results from past experimental and simulation studies have been inconsistent, even for basic quantities such as the framework water capacity and the pressure at which the MFI zeolite pores become water-saturated (infiltration pressure). In this work, we elucidate the underlying mechanisms behind such discrepancies via combined water adsorption and high-pressure infiltration (or intrusion) experiments on various MFI zeolites where the characteristic crystal dimension was varied from nano (≈10 nm) to micro (≈10 μm) scales. Detailed characterization techniques were utilized to demonstrate the presence of non-crystalline silica regions in <100 nm zeolites. Accordingly, an estimated decrease of up to 50% in the framework water capacity was observed for these zeolites when compared to the fully-crystallized larger zeolites, where 35 ± 2 water molecules were required to saturate a unit cell. On the other hand, the water infiltration pressure for all of the zeolites was ≈95-100 MPa despite the differences in the synthesis procedure, indicating uniformity in the crystallized pore structure and surface chemistry. These results are an essential first step towards investigating water transport mechanisms within the sub-nanometer pores and can be used to validate and improve upon existing molecular simulations in order to obtain design guidelines for practical applications such as water-based separation technologies.

KW - Adsorption

KW - Hydrophobicity

KW - MFI zeolite

KW - Textural porosity

KW - Water infiltration

UR - https://www.scopus.com/pages/publications/84894495108

U2 - 10.1016/j.micromeso.2014.01.026

DO - 10.1016/j.micromeso.2014.01.026

M3 - Article

AN - SCOPUS:84894495108

SN - 1387-1811

VL - 190

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EP - 91

JO - Microporous and Mesoporous Materials

JF - Microporous and Mesoporous Materials

ER -

Framework water capacity and infiltration pressure of MFI zeolites

Abstract

Bibliographical note

Keywords

ASJC Scopus subject areas

UN SDGs

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