STUDIES ON MUTUAL SOLID-SOLID INTERACTIONS IN RELATION TO PHYSICOCHEMICAL AND CATALYTIC PROPERTIES OF CHROMIUM OXIDES/ALUMINA SYSTEM

Abstract

Five chromium-aluminium mixed oxides samples containing amounts of CrO, were prepared by mechanical mixing of finelly• powdered of AI(OH)y solid with calculated amounts of CrO, dried at 100C to constant weight then heating the obtained mixed solids at temperatures varying between 400-1000'C. The concentration of Cr0, was varied between 4.3 to 42.7 wt%. The thermal behaviour of the prepared uncalcined mixed solids was studied using TG, DTA and dDTA analysis. The crystalline phases produced at different calcination temperature were characterized using XRD technique. The surface properties of the thermal products of the different prepared mixed solids were studied using N-adsorption measurments carried out at- 196C. The investigated surface characteristics were specific surface area (SBrr), total pore volume (Vp) and mean pore radius (r). The catalytic activity of the produced solids was determined via following up the kinetics of CO-oxidation by O, over the prepared solids preheated at 400-1000'C. The catalytic reaction was. conducted under static conditions at a pressure of about 2 torr at temperatures between 300• 400'C. The effects of Li,O- doping (0.75-6 mol %) on surface and catalytic properties of chromium -aluminium mixed oxides solids were studied. The doping process was carried out at 700 and 800C.