US-20260126363-A1 - METHODS AND APPARATUS FOR CHARACTERIZATION OF POROUS MATERIALS

US20260126363A1US 20260126363 A1US20260126363 A1US 20260126363A1US-20260126363-A1

Abstract

Embodiments described herein generally relate to new methods and apparatus for characterizing porous materials, such as nanoporous materials. In an embodiment, a gravimetric method for characterizing a nanoporous material is provided. The gravimetric method includes contacting a nanoporous material with an adsorbate gas, the nanoporous material positioned inside a core holder. The gravimetric method further includes collecting adsorption data, desorption data, or combinations thereof, the adsorption data and desorption data comprising gravimetric data. The gravimetric method further includes plotting an adsorption isotherm from the adsorption data, a desorption isotherm from the desorption data, or combinations thereof. The gravimetric method further includes converting the gravimetric data from gravimetric values to volumetric values. The gravimetric method further includes selecting a pore geometry for the nanoporous material. The gravimetric method further includes determining one or more characteristics of the nanoporous material.

Inventors

Omer A. SALIM
Sagar Hussain SABUZ
Mohammad Piri

Assignees

UNIVERSITY OF WYOMING

Dates

Publication Date: 20260507
Application Date: 20251031

Claims (20)

1 . A gravimetric method for characterizing a nanoporous material, comprising: contacting a nanoporous material with an adsorbate gas, the nanoporous material positioned inside a core holder; collecting adsorption data, desorption data, or combinations thereof, the adsorption data and desorption data comprising gravimetric data; plotting an adsorption isotherm from the adsorption data, a desorption isotherm from the desorption data, or combinations thereof; converting the gravimetric data from gravimetric values to volumetric values; selecting a pore geometry for the nanoporous material; and determining one or more characteristics of the nanoporous material.
2 . The gravimetric method according to claim 1 , wherein, prior to contacting the nanoporous material with the adsorbate gas, the gravimetric method further comprises: disposing a nanoporous material inside the core holder, the core holder positioned inside of a chamber of a characterization apparatus; applying a vacuum to one or more components of the characterization apparatus; and setting a temperature at which the adsorption data, desorption data, or combinations thereof are collected.
3 . The gravimetric method according to claim 1 , wherein collecting adsorption data, desorption data, or combinations thereof comprises: collecting mass readings from a mass comparator operationally connected to an exterior of the core holder.
4 . The gravimetric method according to claim 1 , wherein the adsorbate gas comprises H 2 , CO 2 , a hydrocarbon, natural gas, He, N 2 , or combinations thereof.
5 . The method according to claim 1 , wherein the one or more characteristics of the nanoporous material comprise surface area, pore volume, pore size, pore size distribution, or combinations thereof.
6 . The gravimetric method according to claim 1 , wherein converting the gravimetric data from the gravimetric values to the volumetric values comprises: converting absolute adsorbed mass data into adsorbed volume at standard temperature and pressure conditions by Eq. 1(a): Volume ⁢ of ⁢ adsorbate ⁢ gas ⁢ adsorbed = mass ⁢ of ⁢ adsorbate ⁢ gas ⁢ adsorbed Density ⁢ of ⁢ adsorbate ⁢ gas ⁢ at ⁢ STP ; ( Eq . 1 ⁢ ( a ) ) and converting an absolute pressure of the adsorbed gas inside the core holder into a relative pressure (relative P) of the adsorbed gas by normalization with a saturation pressure of the adsorbate gas at the temperature at which the adsorption data, desorption data, or combinations thereof are collected according to Eq. 1(b): Relative ⁢ pressure ⁢ of ⁢ adsorbed ⁢ gas = Absolute ⁢ pressure ⁢ of ⁢ adsorbed ⁢ gas Saturation ⁢ pressure ⁢ of ⁢ adsorbate ⁢ gas . ( Eq . 1 ⁢ ( b ) )
7 . The gravimetric method according to claim 1 , wherein determining the one or more characteristics of the nanoporous material comprises: determining a BET specific surface area of the nanoporous material.
8 . The gravimetric method according to claim 1 , wherein determining the one or more characteristics of the nanoporous material comprises: determining a specific pore volume of the nanoporous material by Eq. 3(a): specific ⁢ pore ⁢ volume ⁢ ( SPV ) = V S ⁢ T ⁢ P * M g ⁢ a ⁢ s M ⁢ V * ρ L , ( Eq . 3 ⁢ ( a ) ) wherein: V STP is adsorbed volume of the adsorbate gas at standard temperature and pressure; M gas is molar mass of the adsorbate gas; ρ L is liquid density of the adsorbate gas at the temperature at which the adsorption data, desorption data, or combinations thereof are collected; and MV is molar volume of the adsorbate gas.
9 . The gravimetric method according to claim 1 , wherein determining the one or more characteristics of the nanoporous material comprises: determining a specific surface area of the nanoporous material by Eq. 3(b): specific ⁢ surface ⁢ area = 2 * V p r p , ( Eq . 3 ⁢ ( b ) ) wherein: V p is specific pore volume; and r p is corresponding radius of the pores.
10 . The gravimetric method according to claim 1 , wherein determining the one or more characteristics of the nanoporous material comprises determining a pore size distribution of the nanoporous material, wherein determining the pore size distribution of the nanoporous material comprises: converting a relative pressure of the adsorbed gas into a Kelvin radius by Eq. 4: r k = γ * V l R * T * ln ⁡ ( P P o ) ( Eq . 4 ) wherein: r k is Kelvin radius of the pores at the corresponding relative pressure of the adsorbed gas; γ is surface tension of the adsorbate gas; V l is molar volume of liquid adsorbate; R is universal gas constant; T is Kelvin temperature; ln is natural logarithm; and P P o is relative pressure of the adsorbed gas.
11 . The gravimetric method according to claim 10 , wherein determining the pore size distribution of the nanoporous material further comprises: plotting the Kelvin radius with the volume of the adsorbate gas adsorbed; and plotting a differentiation of the adsorbed volume with respect to a pore size (2×r k ) of the nanoporous material (dVp/dwp) against the pore size (2×r k ) of the nanoporous material to determine the pore size distribution of the nanoporous material.
12 . A gravimetric method for characterizing a nanoporous material, comprising: disposing a nanoporous material inside a core holder of a characterization apparatus; applying a vacuum to one or more components of the characterization apparatus; setting a temperature at which the adsorption data, desorption data, or combinations thereof are collected; contacting the nanoporous material with an adsorbate gas; collecting adsorption data, desorption data, or combinations thereof, the adsorption data and desorption data comprising gravimetric data; plotting an adsorption isotherm from the adsorption data, a desorption isotherm from the desorption data, or combinations thereof; converting the gravimetric data from gravimetric values to volumetric values; selecting a pore geometry for the nanoporous material; and determining one or more characteristics of the nanoporous material.
13 . The gravimetric method according to claim 12 , wherein collecting adsorption data, desorption data, or combinations thereof comprises: collecting mass readings from a mass comparator operationally connected to an exterior of the core holder.
14 . The gravimetric method according to claim 12 , wherein the adsorbate gas comprises H 2 , CO 2 , a hydrocarbon, natural gas, He, N 2 , or combinations thereof.
15 . The method according to claim 12 , wherein the one or more characteristics of the nanoporous material comprise surface area, pore volume, pore size, pore size distribution, or combinations thereof.
16 . The gravimetric method according to claim 12 , wherein determining the one or more characteristics of the nanoporous material comprises: determining a BET specific surface area of the nanoporous material.
17 . The gravimetric method according to claim 12 , wherein determining the one or more characteristics of the nanoporous material comprises: determining a BJH specific pore volume of the nanoporous material; determining a BJH specific surface area of the nanoporous material; or a combination thereof.
18 . The gravimetric method according to claim 12 , wherein determining the one or more characteristics of the nanoporous material comprises determining a pore size distribution of the nanoporous material, wherein determining the pore size distribution of the nanoporous material comprises: converting a relative pressure of the adsorbed gas into a Kelvin radius; plotting the Kelvin radius with the volume of the adsorbate gas adsorbed; and plotting a differentiation of the adsorbed volume with respect to a pore size (2×r k ) of the nanoporous material (dVp/dwp) against the pore size (2×r k ) of the nanoporous material to determine the pore size distribution of the nanoporous material.
19 . A gravimetric nanocondensation apparatus for characterizing a nanoporous material, the gravimetric nanocondensation apparatus comprising: a core holder; a pressure sensor coupled to the core holder, the pressure sensor configured to sense a pressure within the core holder and produce a pressure signal; a mass comparator operationally connected to an exterior of the core holder; a valve configured to control flow of adsorbate gas into the core holder and configured to control pressure within the core holder; a controller coupled to the pressure sensor, the valve, and the mass comparator, the controller configured to: cause flow of the adsorbate gas into the core holder to contact the nanoporous material by opening the valve; and cause collection of adsorption data, desorption data, or combinations thereof, the adsorption data and desorption data comprising gravimetric data by logging data from the pressure sensor and the mass comparator.
20 . The gravimetric nanocondensation apparatus of claim 19 , wherein the adsorbate gas comprises H 2 , CO 2 , a hydrocarbon, natural gas, He, N 2 , or combinations thereof.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims benefit of and priority to U.S. Provisional Patent Application No. 63/715,334, filed on Nov. 1, 2024, which is incorporated herein by reference in its entirety. FIELD Embodiments of the present disclosure generally relate to new methods and apparatus for characterizing porous materials, such as nanoporous materials. BACKGROUND Nanoporous materials offer a wide range of applications across industries due to their distinctive characteristics. For example, nanoporous materials are used in various applications, including gas storage and separation, enabling hydrogen storage and carbon dioxide capture. In catalysis, nanoporous materials function as catalyst supports in automotive emissions control and chemical synthesis. Nanoporous materials play a role in water purification systems, drug delivery for controlled release, and energy storage devices such as supercapacitors and batteries. Additionally, nanoporous materials find application in sensing technologies for environmental monitoring and medical diagnostics, as well as in membrane technology for filtration and separation processes. The thermal insulation characteristics of nanoporous materials render them advantageous for electronic device thermal management. Overall, nanoporous materials contribute significantly to advancements in technology and sustainable solutions across various sectors. Therefore, accurate characterization of nanoporous materials is beneficial for identifying performance parameters and expanding applications across technology sectors. Precise characterization enables researchers and engineers to understand the structural properties, such as pore size distribution, surface area, and pore volume, which directly influence their functionality in such applications. Conventional technologies for studying pore characteristics of nanoporous materials typically involve nitrogen adsorption or desorption experiments at low pressures (up to 1 atm). However, the size of nitrogen molecules prohibit their entry into certain pores and the inability to perform high pressure experiments prevents detailed determination of pore characteristics under various environmental conditions. Further, conventional technologies rely on imprecise volumetric measurements and make use of equations of state to estimate the adsorbed volumes, which is an indirect estimation of volumetric parameters, leading to low reproducibility and accuracy. There is a need for new methods and apparatus for characterizing porous materials. SUMMARY Embodiments of the present disclosure generally relate to new methods and apparatus for characterizing porous materials, such as nanoporous materials. Unlike conventional technologies, embodiments described herein utilize a novel gravimetric method for accurately characterizing nanoporous materials by estimating various characteristics (quantitative and qualitative parameters) of the nanoporous materials. Quantitative parameters that may be estimated or determined include specific surface area, pore size, pore size distribution, specific pore volume, or combinations thereof using any suitable theoretical method such as Brunauer-Emmett-Teller (BET), Barrett-Joyner-Halenda (BJH), density functional theory (DFT), or non-local DFT (NLDFT), among others. Qualitative parameters that may be estimated or determined include pore networks, texture, and combinations thereof, among others. In contrast to conventional technologies, embodiments described herein eliminate errors inherent with traditional methods through the use of, for example, high-precision balances (mass comparators), ensuring reliable estimation of, for example, specific surface area, pore size distribution, and/or specific pore volume, among other characteristics due to the use of direct measurement of the adsorbed mass (gravimetric technique). Embodiments of the present disclosure may also be compatible with a wider range of temperatures and pressures relative to conventional technologies, enabling characterization of nanoporous materials under various environmental conditions to capture their diverse properties. Unlike conventional technologies, embodiments of the present disclosure enable the characterization of nanoporous materials using different types of adsorbates such as hydrogen (H2), helium (He), carbon dioxide (CO2), nitrogen (N2), hydrocarbons (for example, methane, ethane, etc.), and natural gas, enabling comprehensive analysis of material properties across various applications and research domains. Moreover, gravimetric methods described herein overcome the inherent limitation of the other conventional gravimetric methods which utilize buoyancy corrections due to placement of the sample, mass balance, and gas collectively in the same settings. In contrast, and in the various embodiments described herein, the placement of the sample and gas remains isolated inside a core holder and the core holder is kept hangi