STUDY OF ACID-BASE INTERACTIONS BETWEEN SOME METALLIC OXIDES AND MODEL ORGANIC-MOLECULES

Inverse gas chromatography technique at infinite dilution was used to calculate the acidic and basic surface characteristics of three oxides (Monogal, MgO and ZnO). We determined the specific interactions betwe en them and model organic molecules and showed the amphoteric feature of such oxides. It was observed that MgO is more basic than the others . We also proved that the usual relation giving the specific enthalpy of adsorption (Delta H-sp) of a polar molecule adsorbed on a solid: (- Delta H-sp)=(KADN +K(D)AN) was not correct. We proposed a new relation ship by adding a third parameter K reflecting the amphoteric character of the solid according to: (-Delta Hsp) = K(D)AN + K(D)AN - KANDN We proved that our model gives the best results relatively to those obtai ned by the classical equation. Another relationship was also proposed: (-Delta Hsp) = w(KADN + K(D)AN) where w is the weighing factor of the exchanging interactions between adsorbed molecule and solid substrate . (C) 1997 Elsevier Science B.V.