Alkylaromatic charge hydrocarbons such as toluene are steam dealkylated in the presence of catalyst which typically contains oxides of nickel, chromium, and potassium on an activated high-purity alumina. It is a feature of this invention that the high-purity alumina is activated by calcining followed by addition thereto of alkaline earth metal such as calcium or magnesium. A test is disclosed according to which it may be determined which high-purity aluminas are suitable for use.