SPECTROTHERMAL INVESTIGATION OF THE DECOMPOSITION COURSE OF LANTHANUM ACETATE HYDRATE

Thermogravimetry, differential thermal, X-ray diffraction and infrared spectroscopy analyses showed La(CH3COO)3.1.5H2O to decompose completely at 700-degrees-C yielding La2O3. The results revealed that the compound dehydrates in two steps at 130 and 180-degrees-C, and recrystallizes at 210-degrees-C. Water thus produced hydrolyzes surface acetates (at 310-degrees-C), releasing acetic acid into the gas phase. At 334-degrees-C, the anhydrous acetate releases gas phase CH3COCH3 to give La2(CO3)3 residue, which decomposes to La2O2(CO3) via the intermediate La2O(CO3)2. On further heating up to 700-degrees-C, La2O3 is formed. IR spectroscopy of the gaseous products indicated a chemical reactivity at gas/solid interfaces formed throughout the decomposition course. As a result, CH3COCH3 was involved in a surface-mediated, bimolecular reaction, releasing CH4 and C4H8 (isobutene) into the gas phase. Non-isothermal kinetic parameters, the rate constant k, frequency factor A, and activation energy DELTAE, were calculated on the basis of temperature shifts experienced in the thermal processes encountered, at various heating rates (2-20 deg.min-1).