Adsorption of methanol as a probe for surface characteristics of zirconia-, alumina-, and zirconia/alumina-supported chromia catalysts

The aim of our study was to improve the supported chromia dehydrogenation catalysts by combining the beneficial properties of the industrially used chromia/alumina (CrAl) catalyst with those of the more active chromia/zirconia (CrZr) catalysts. We report here the results on the surface characteristics, the surface composition and the type of the functional surface species, of chromia/zirconia/alumina (CrZrAl) catalysts that were studied by methanol adsorption–desorption. The measurements were carried out using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and operando Raman spectroscopy. The performance of CrZrAl catalysts was compared with CrZr and CrAl catalysts. The CrZrAl catalysts resembled more the CrAl catalysts than the CrZr catalysts in their behavior. Lewis acidity of the alumina support was detected even with the highest used Zr loading of approximately one monolayer. The similar performance of the CrZrAl and the CrAl catalysts was assigned to a strong interaction between zirconia and alumina. Cr on the catalysts activated methanol at low temperatures to form formates, induced basic properties and promoted hydrogen formation.