ANALYSIS OF THERMALLY-INDUCED SOLID-SOLID INTERACTIONS IN VANADIA-ALUMINA SYSTEM

V2O5/Al2O3 solids of varying compositions were prepared, dried at 100 degrees C and calcined in air at 400-1000 degrees C. The solid-solid i nteractions between the mixed oxides were investigated by means of DTA , TG and XRD techniques.The results revealed that ammonium metavanadat e and aluminium hydroxide decomposed at 260 and 290 degrees C, respect ively, to yield an ammonium vanadium intermediate compound and Al2O3 a s solids. The intermediate compound readily decomposed at 360 degrees C to give V2O5. Solid V2O5 generally catalyses the crystallization of Al2O3 to an extent proportional to its amount present. The solid-solid interactions between Al2O3 and V2O3 to produce AlV2O4 and A1VO(4) too k place at 750 and 900 degrees C. These solids decomposed entirely at 1000 degrees C, producing V2O5 and alpha-corundum. The pure Al2O9 samp les employed existed as amorphous solids even when heated in air at 75 0 degrees C, but in the presence of V2O5 (7-18 wt. %) they crystallize d to theta-alumina at 600 degrees C. The pure solid alumina crystalliz ed at 1000 degrees C to a mixture of theta and kappa-alumina. In the p resence of V2O5, alpha-corundum together with kappa and theta phases w as obtained on heating at 900 degrees C.