Catalytic effects of magnesium chromite spinel on the decomposition of lanthanum oxalate

A study on the thermal decomposition of mixtures of lanthanum oxalate hydrate and magnesium chromite spinel, MgCr2O4 of different molar ratios has been carried out employing thermogravimetry, differential thermal analysis, chemical analysis, infrared spectroscopy and X-ray diffraction analysis. It is evident from the data that lanthanum oxalate in the presence of mixed oxide starts to decompose at a temperature higher than the pure salt. The results reveal that chromium oxide has a retarding effect on the decomposition rate and addition of magnesium oxide leads to an observable increase in the catalytic behaviour of Cr2O3 towards the decomposition below 440 °C, above which it increases significantly with increasing percentage of MgCr2O4. The induced defects during the formation of solid solution alters the conductive properties of the oxide, due to generation of more holes within the catalyst, consequently increasing its, activity towards decomposition. The kinetic and thermogravimetric parameters are evaluated in the light of D3 mechanism. The reaction occurs through three different stages and the rate constant, k is found to follow the order: stage I>stage IILO2>LO3 (653–713 K), LO1