Measurement of the surface coverage of V/Al2O3 catalysts by infrared spectroscopy, CO2 chemisorption and ion scattering spectroscopy

Quantitative FTIR studies of alumina hydroxyl groups have been used to measure the surface coverage of V/Al₂O₃ catalysts. The IR spectra show a preferential consumption of the most basic hydroxyls (3769 cm^–1) with the initial V uptake. The integrated area of the hydroxyl region was used to calculate the surface coverage of the catalysts. The surface coverage increased to 0.63 as the V loading increased to 6.7 wt%. The surface coverage results obtained from IR were compared to those measured by ion scattering spectroscopy (ISS) and CO₂ chemisorption. The surface coverages measured by ISS were comparable to those obtained by IR. In contrast, CO₂ chemisorption appears to overestimate the surface coverage of the catalysts. The overestimation of the surface coverage by the CO₂ chemisorption method is attributed to the preferential adsorption of the V phase onto the most basic hydroxyls, the same sites which interact with CO₂.Dedicated to Professor Dr. Dieter Klockow on the occasion of his 60th birthday