Rare earth oxides, such as Nd.sub.2 O.sub.3 disperse onto the surface of SiO.sub.2 /Al.sub.2 O.sub.3 and act as weakly basic titrants. This lowers the acidity of SiO.sub.2 /Al.sub.2 O.sub.3 to close to that of chlorided alumina, as shown by model compound reaction tests. This support also disperses a noble metal such as Pt much better than undoped SiO.sub.2 /Al.sub.2 O.sub.3 and similar to chlorided alumina. Platinum on the rare earth modified silica alumina can function as a hydrocarbon conversion catalyst in reactions where Pt/chlorided Al.sub.2 O.sub.3 is used, such as in reforming, and isomerization, especially wax isomerization.