DETERMINATION OF THE SURFACE COVERAGE OF MO/AL2O3 CATALYSTS

The surface coverage of a series of Mo/Al2O3 catalysts prepared by the equilibrium adsorption method was measured by CO2 chemisorption, low-temperature CO adsorption and ion scattering spectroscopy (ISS). Comparable values were obtained from ISS and CO adsorption. The results correspond to Mo cross-sections of 22.2 Angstrom(2) Mo-1 (GO) and 20 Angstrom(2) MO(-1) (ISS). The Mo coverages obtained by CO adsorption and ISS were compared with those estimated from CO2 chemisorption. The resuls indicated that, irrespective of the approach used to measure the coverage from CO2 chemisorption (volumetric method or from the decrease of the IR peaks attributed to bicarbonate and 'free' carbonate species), the CO2-based method significantly overestimates the coverage.