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
Jhonny Villarroel-Rocha, José J. Arroyo-Gómez, Deicy Barrera, Karim Sapag
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引用次数: 0
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.
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.