ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Differential heats of adsorption

J. Juliš

Department of Physical Chemistry, Institute of Chemical Technology, 166 28 Prague

Abstract:  The meaning of the isosteric heat q_st, which follows from its definition and the used thermodynamic models, was discussed and the dependences of g_st on the occupancy of the adsorbed layer (at T ≤ T_v) were derived for an adsorbate with both ideal and non-ideal behaviour on an energetically homogeneous adsorbent. With the assumption that the energetic heterogeneity of the surface can be described by a single distribution curve, the general form of the dependence of the integral and differential adsorption heat on the occupancy of the adsorbed layer was derived both without and with the presence of a lateral interaction between the adsorbed molecules at higher occupancies  Θ of the adsorbed layer. The maximum on the q_st—  Θ  dependence at high values of Θ  is shown to be a consequence of the properties of differential quantities in the adsorption systems with either an energetically heterogeneous surface or the presence of a lateral interaction, or with both these properties.

Full paper in Portable Document Format: 295a653.pdf

Chemical Papers 29 (5) 653–659 (1975)