Determination of the surface coverage of Mo/Al 2 O 3 catalysts

The surface coverage of a series of Mo/Al 2 O 3 catalysts prepared by the equilibrium adsorption method was measured by CO 2 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 Å 2 Mo −1 (CO) and 20 Å 2 Mo −1 (ISS). The Mo coverages obtained by CO adsorption and ISS were compared with those estimated from CO 2 chemisorption. The resuls indicated that, irrespective of the approach used to measure the coverage from CO 2 chemisorption (volumetric method or from the decrease of the IR peaks attributed to bicarbonate and ‘free’ carbonate species), the CO 2 ‐based method signficantly overestimates the coverage.