Smectite molecular sieves. Part 2.—Expanded fluorhectorite sorbents

Abstract

Sorption equilibria have been measured for O₂, N₂, Ar, Kr, CO₂, CH₄, CH(CH₃)₃ and C(CH₃)₄ in cobaltic tris-(ethylenediamine) ion-exchanged forms of fluorhectorites having exchange capacities of ca. 90 (FH90) and ca. 150 (FH 150) meq per 100 g. The sorbents provide a small external area and a large interlamellar free area. The two kinds of sorbent have very different molecule sieving characteristics, dependent upon different free distances between pairs of adjacent interlamellar cations in relation to the shape and size of the potential guest molecules. At low temperatures the sorbents from FH150 distinguished between O₂ and N₂ or Ar as sensitively as zeolite Na-A. The sorbents based on FH90 readily intercalated CH(CH₃)₃ and C(CH₃)₄, but these molecules were excluded from the sorbents based on FH150. Calculated interlamellar free areas, allowing for the areas excluded by the cations, are in reasonable agreement with these areas derived from amounts intercalated.