A new and reliable method to obtain micropore volume in nanoporous solids by gas adsorption based on Dubinin works and the thickness of the adsorbed layer

IF 2.5 4区 材料科学 Q2 CHEMISTRY, APPLIED
Jhonny Villarroel-Rocha, José J. Arroyo-Gómez, Deicy Barrera, Karim Sapag
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Abstract

It is known that the use of the Dubinin–Radushkevich method in micro-mesoporous samples does not give adequate values of micropore volumes, unlike when the samples contain only microporous. Based on that, in this work, we propose an easy method to calculate a reliable micropore volume (VμP) of micro-mesoporous (nanopores) samples, separating the microporous region from the experimental isotherm. For this, the original isotherm is modified, estimating the thickness of the adsorbed layer (t) as a function of relative pressure and changing the external surface area (Sext) to obtain a Type I adsorption isotherm in the microporous region; then, the DR method can be applied to the modified isotherm. This proposal, named the DR_t method, allows the calculation of a reliable VμP of any nanoporous material using different adsorbates. Using this method, we analyzed adsorbents of distinct nature (i.e., carbons and silicas) with different adsorbates as N2 and O2 at 77 K, Ar at 87 K, and CO2 at 273 K. We used this method to calculate VμP in different samples and compare them with those obtained with the traditional DR method, highlighting that unlike the latter the DR_t method showed similar and consistent results with the different adsorbates. Therefore, the values of micropore volume calculated using the DR_t method demonstrate consistency across various adsorbates, not only for N2 but especially for CO2, which is suggested to analyze narrow micropore volumes.

Abstract Image

Abstract Image

基于杜宾工程和吸附层厚度的气体吸附纳米多孔固体微孔体积的可靠新方法
众所周知,在微多孔样品中使用 Dubinin-Radushkevich 方法无法获得足够的微孔体积值,这与样品仅含有微孔时的情况不同。在此基础上,我们在本研究中提出了一种简便的方法来计算微多孔(纳米孔)样品的可靠微孔体积(VμP),将微孔区域与实验等温线分开。为此,需要对原始等温线进行修正,将吸附层厚度 (t) 作为相对压力的函数进行估算,并改变外表面积 (Sext),以获得微孔区域的 I 型吸附等温线;然后,可将 DR 方法应用于修正后的等温线。这一建议被命名为 DR_t 方法,可以利用不同的吸附剂计算出任何纳米多孔材料的可靠 VμP。利用这种方法,我们分析了不同性质的吸附剂(即碳和硅)与不同的吸附剂,如 77 K 时的 N2 和 O2、87 K 时的 Ar 和 273 K 时的 CO2。我们利用这种方法计算了不同样品中的 VμP,并将其与传统 DR 方法得出的结果进行了比较,结果表明 DR_t 方法与后者不同,对不同吸附剂的计算结果相似且一致。因此,使用 DR_t 方法计算出的微孔体积值在各种吸附剂中显示出一致性,不仅适用于 N2,尤其适用于 CO2,建议用于分析狭窄的微孔体积。
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来源期刊
Journal of Porous Materials
Journal of Porous Materials 工程技术-材料科学:综合
CiteScore
4.80
自引率
7.70%
发文量
203
审稿时长
2.6 months
期刊介绍: The Journal of Porous Materials is an interdisciplinary and international periodical devoted to all types of porous materials. Its aim is the rapid publication of high quality, peer-reviewed papers focused on the synthesis, processing, characterization and property evaluation of all porous materials. The objective is to establish a unique journal that will serve as a principal means of communication for the growing interdisciplinary field of porous materials. Porous materials include microporous materials with 50 nm pores. Examples of microporous materials are natural and synthetic molecular sieves, cationic and anionic clays, pillared clays, tobermorites, pillared Zr and Ti phosphates, spherosilicates, carbons, porous polymers, xerogels, etc. Mesoporous materials include synthetic molecular sieves, xerogels, aerogels, glasses, glass ceramics, porous polymers, etc.; while macroporous materials include ceramics, glass ceramics, porous polymers, aerogels, cement, etc. The porous materials can be crystalline, semicrystalline or noncrystalline, or combinations thereof. They can also be either organic, inorganic, or their composites. The overall objective of the journal is the establishment of one main forum covering the basic and applied aspects of all porous materials.
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