Catalyst Effect of Transition Metal Nano Oxides on the Decomposition of Lanthanum Oxalate Hydrate: A Thermogravimetric Study

A study on the thermal decomposition of the mixtures of lanthanum oxalate hydrate and transition metal nano oxide compounds (TMNOCs) viz. CuO, Fe2O3, TiO2 and Cr2O3 of 5 mole % ratio has been carried out employing Thermogravimetry (TG), Differential Thermal Analysis (DTA) and chemical analysis. The results reveal that other than CuO the oxides have a retarding effect on the decomposition rate. There is a competition of rate between Fe2O3 and TiO2 mixture up to 696K after which the trend is reversed and Fe2O3 becomes relatively more catalytic than TiO2. The best explanation for catalytic activities of the oxides is made by taking the former as a function of electronic configuration of the metal rather than the electronic properties of the oxides. Abnormal behaviour of Cr2O3 may be attributed to an irreversible change in oxidation state of Cr3+ during which it is oxidised to Cr6+ prior to decomposition. The kinetic and thermodynamic parameters are evaluated in the light of F3 mechanism in two differ-ent regions of s and the rate follows the order: S1 less than S2 greater than S3 less than S4 greater than S5 (0.1 less than less than 0.5) S1 less than S2 greater than S3 greater than S4 greater than S5 (0.5