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Surface area measurements by nitrogen and argon adsorption

1975; Elsevier BV; Volume: 52; Issue: 3 Linguagem: Inglês

10.1016/0021-9797(75)90282-9

1095-7103

Raouf Sh. Mikhail, Stephen Brunauer,

Ammonia Synthesis and Nitrogen Reduction

Surface areas measured by nitrogen and argon are discussed. The greatest difficulty with argon adsorption is that the area covered by an argon atom is determined primarily by the adsorbent-adsorbate interaction, with a negligible adsorbate-adsorbate interaction between the argon atoms. As a result, various investigators reported areas occupied on different adsorbent surfaces by an argon atom ranging from 13.7–18.2 Å2. In the case of nitrogen adsorption, the lateral interaction is probably not negligible; in fact, in the vicinity of the completion of a monolayer, where the adsorbent-adsorbate interaction is the weakest and the adsorbate-adsorbate interaction is at its maximum, the lateral interaction of nitrogen molecules on the surface may be able to pull them together to form a close-packed liquid-like monolayer. This is why a constant area of 16.2 Å2 can be used for nitrogen in the overwhelming majority of adsorbents. An exception is discussed, which confirms the above hypothesis.