CATALYSTS ON THE BASIS OF ACTIVATED ALUMINUM-ALLOYS .3. FORMATION OF OXIDE ALUMINA CATALYSTS

The formation of the bulk and surface of a new generation of oxide alu mina catalysts, prepared by the interaction of metallic aluminum (Al-m et) activated with Ga and In with water, is studied by XRD, thermal an alysis, adsorption, and IR spectroscopy. At the stage of hydroxide for mation, pseudoboehmite (PB) and bayerite (B) are produced, with the ra tio between these phases dependent on the temperature of the interacti on between Al-met and water and on the concentration of the activating additive. Thermolysis of PB and B leads to various low-temperature mo difications of Al2O3. The In concentration at the surface is lower tha n in the bulk. Unlike indium, gallium is uniformly distributed between the surface and the bulk and cannot be revealed as a separate phase b y XRD. The oxide alumina catalysts exhibit a developed surface area (u p to 320 m(2)/g) and diverse porous structures. Three types of non-ass ociated OH groups, characterized by the different number of adjacent A l atoms, as well as OH groups with a strong hydrogen bond are found at the surface. Lewis, but not Bronsted, acidic properties (revealed by pyridine adsorption) are inherent to the catalyst surface. The number of Lewis acid sites increases from 1.0 to 2.2 mu mol/m(2) with an incr easing concentration of activating agents from 2 to 20 wt %.