Chemisorption of O2, H2, and H2O-Vapor at Cr2O3: Molar heat effects, rates, and mechanisms of chemisorption

Abstract

Molar heats and rates of chemisorption and sorption of H2, O2, H2O, and CO2 at porous Cr2O3 over the range 293–673 K are studied at different degrees of filling of this oxide with the adsorbates. Improved adsorption and calorimetric methods adapted for measurements of chemisorption of any adsorbate at samples filled with controlled amounts of other adsorbates are used. It is stated that H2 not only chemisorbs but also sorbs into sample bodies; after H2 sorption, Cr2O3 is able of sorbing O2 amounts in excess of the O2 amount inherent in the fully oxidized standard chromic oxide samples, sorption proceeding up to the stoichiometry Δ[O]/Δ[H] = 1. It is proved that Cr2O3 surface centers are homogeneous with respect to their adsorption ability. The mechanisms of chemisorption and sorption are discussed.