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/Al₂O₃ 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 × 10⁴ J mol^–1) and the isosteric heat of adsorption are in good agreement with previous calorimetric data.