Infra-red Determination of the Isotherm of Hydrogen Adsorption on a Pt/Al2O3 Catalyst

Abstract

Of the various forms of hydrogen adsorbed on platinum only hydrogen weakly and reversibly adsorbed is detected by an infra-red band at 2120 cm-1. The preparation of a well dispersed sample of Pt/ALO? catalyst containing 10 % platinum allows us to determine accurately the hydrogen adsorption isotherm of this weakly adsorbed species. Only a dissociative Langmuir model fits the experimental results in the pressure range of 10'1 to 700 Torr and temperature range of 27 to 95°C. The heat of adsorption (—5 x 104 J mol-1) and the isosteric heat of adsorption are in good agree ment with previous calorimetric data.