The Adsorption of Nitrogen, Oxygen, and Argon by Graphite

Abstract

'I'he a d s o r p t i o~~ of nitrogen, oxygen, and argon b?. three '\cheson graphites ha-; been n~easured a t liquid nitrogen and liquid oxygen temperatures. The isotherru~ were 'Sype I1 in the B.E.T. classilication and displayed two kinds of hysteresis.The first kind was attributed to the presence of pores ill the graphite and the seco~lcl kind to illtercrystalline swelling. This paper describes an i~~vestigation of three artificial graphites m a~~u f a ctured by the Acheson Colloids Corporation. V e r~. little detailed adsorp~iol~ work has been done with graphites of this type with a view to elucidati~~g their structure. Barrer (2) has measured the adsorption of nitrogen, argoll, ar~cl hydrogen by an Acheson graphite over a considerable temperature range ancl has calculated isosteric heats from the isotherms. He found that the graphite was energetically heterogeneous to all three gases and that the heats in the case of nitrogen were unaffected by the addition of chemisorbed oxygen to the surface of the graphite. He concluded therefore that the heterogeneity was a property of the carbon structure. In the opinion of the authors, the tvealiness of this work lies in the fact that very few adsorption points were measured a t each temperature and no desorption points a t all were determined. Bartell and Dodd (4) measured the adsorption of nitrogen a t liquid nitrogen temperatures by a number of carbons which included two Acheson graphites. The purpose of the work was to measure the surface area of the carbons so that only a small number of points were determined and only i l l the case of the diamond powder were desorption points talien. I t is stated that 110 d e s o r p t i o~~ points were measured for the graphite because reversibility for nitrogen adsorption had been established a t liq~lid oxygen telnperatures. Bartell and Dodd do not indicate to what pressures these measurements were carried, but it will be shown in the present paper that reversibilitl. of the nitrogen isotherm a t 90°1<. is by no means a criterion for reversibility unless pressure measurements are extended to well over an atmosphere. Because of the lack of d a t a on these graphites, it was decided to undertake a detailed s t~~d y of three typical artificial graphites. The first step was to measure isotherms a t low temperatures using as adsorbates ~~i t r o g e n , oxygen, ancl argoll. Uliusual hysteresis effects were encou~~tered and therefore a detailed study was made on one graphite usi~ig nitrogen as the adsorbate. For comparative purposes the nitrogen isotherm of a nonporous carbon black I V~S also determined.

The Structure of Artificial Graphites as Revealed by X-Ray, Electron Microscope, and Adsorption Studies

“…They were designated as G-3, G 5 , and GF-5. G 3 has been described in two previous papers (4,5). G 5 was an Acheson graphite of high surface area.…”

“…The apparatus and procedures are exactly as described previously (4). Isotherms for the adsorption of nitrogen by G-3, G-5, and GF-5 are presented in Fig.…”

“…Two previous papers (4,5) on the adsorption of gases by graphite have shown that the artificial graphites studied were porous adsorbents which displayed Type I1 isotherms in the B.E.T. classification.…”

The Adsorption of Nitrogen by Brominated Graphite and Carbon Black

“…The gl-apliites used \\-ere artificial graphites manufactured b3-Acheson Colloids 1,tcl. and have been described previously by McDermot and Arnell (5). For the purpose of this worl;, they have been designated as G-1, G-2, and G-3.…”

Development of a sorption-based Joule-Thomson cooler for the METIS instrument of E-ELT

“…A large number of experimental hydrogen isotherms on various adsorbents, such as activated carbon, carbon nanotubes and graphite measured for storage purposes have been reported [50][51][52]. Isotherm data of other working fluids such as nitrogen, neon, and krypton, can also be found in literatures [53][54][55]. These literature data are certainly useful in a preliminary design phase.…”