Direct determination of effective BET-area of Xe, Kr, and CH{sub 4}

Journal Article · Tue Aug 01 04:00:00 EDT 1995 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1995.1199· OSTI ID:111009

Suzuki, Isao; Kiuchi, Humihito; Saitou, Kazumi ^[1]

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1. Utsunomiya Univ. (Japan)

The surface area by adsorption is obtained by multiplying the product of the number of adsorbed molecules and the effective area per molecule. The absolute value of the effective area of Xe or Kr is important because the surface area estimated from the gas uptake of Xe or Kr can be compared with the geometrical surface area to give the roughness factor. The effective area of the adsorbed molecules could be estimated from the density of the adsorbate in the bulk liquid or solid state. However, there is no certainty that the monolayer packing will be the same as in the bulk. The effective area can be larger than the value expected from the van der Waals size of the adsorbed molecule, if the interaction energy between the adsorbed molecule and the surface is periodic across the surface and is larger than RT. For example, the one-dimensional expansion coefficient of Xe adsorbed on NaCl was found to be strongly increasing above 55 K and exceeded by far the value for bulk Xe at these temperatures using LEED and AES techniques. The purpose of the present paper is to determine the effective area {sigma} of adsorbates such as Xe, Kr, and CH{sub 4} by using the known area S of steel balls in the equation {sigma} = (22414/V{sub m}) (S/N{sub O}), where V{sub m} and N{sub O} are the BET monolayer volume in STP cm{sup 3} and Avogadro`s constant respectively. 10 refs., 2 figs., 1 tab.

• OSTI ID: 111009
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 1 Vol. 155; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
ADSORPTION
KRYPTON
METHANE
SURFACE AREA
XENON