Adsorption on siliceous zeolites with perfect framework - II. Adsorption heat of ethylamine, n-pentane and ethanol on FAU zeolite

The adsorption heat of ethylamine, n - pentane and ethanol was measured bas ed upon the determination of adsorption isotherms at different temperatures on high silica FAU type zeolite with perfect Si - O framework. Calculated with Clapeyron - Clausious equation, the isosteric heat of adsorption Q(st) (C) (adsorption heat at certain coverage, which is defined as the numbers of adsorbed molecules per unit cell) and average isosteric heat of adsorpti on Q(st)* (the average adsorption heat with various coverage determined in a certain temperature range) were obtained for the adsorbates investigated. DeltaH(I) - the difference of Q(st)* and DeltaH(V)(the heat of vaporizatio n of certain adsorbate), was defined as interaction strength for characteri zing the interaction between Si - O framework of the zeolite and the adsorb ed organic compound. The order of DeltaH(I) for the adsorbed organic compou nds is as follows: DeltaH(I)(ethylamine) > DeltaH(I)( n - pentane) > > Delt aH(I)(ethanol), which is consistent with the order of A(T) value (affinity index, was defined as A(T) = T-d - T-b, where T-d is the temperature of the weight loss peak of the DTG curve, and T-b is the boiling point of a certa in adsorbate). The strong interaction between Si - O framework and the adso rbed ethylamine, which was observed from the desorption behavior on FAU zeo lite, is thermodynamically proved in this study by the high interaction str ength of DeltaH(I)(ethylamine) determined quantitatively.