Specific interactions and steric effects on “beidellite type” interlamellar complexes

Summary

The gas chromatographic behaviour of some olefinic, diolefinic and alicyclic hydrocarbons was investigated on columns containing dimethyldioctadecylammonium derivatives of phyllosilicates. The beidellite type complexes proved to be more effective for the separation of the isomers investigated. On the basis of the retention indices it was tried to separate the effect of the specific interactions, between sample and adsorbent, from the steric effects. It was shown that strong specific interactions result in great retentivity and steric effects facilitate the separation of the strongly retained molecules having a different geometry. The separation of saturated hydrocarbons takes place on the external surface which acts as a paraffinic one. Between 30 and 50°C exists a transition temperature for the interlamellar complexes and below this point both the efficiency and separating power drop down.