Synthesis course and surface properties of praseodymium oxide obtained via thermal decomposition of praseodymium acetate: Impacts of the decomposition atmosphere

摘要

The decomposition course, intermediates and final products of praseodymium acetate monohydrate Pr(CH_3COO)_3·H_2O in different gas atmospheres (O_2, N_2 or H_2) were characterized using thermal analysis, X-ray diffractometry and infrared spectroscopy. Praseodymium acetate decomposes in five mass loss events leading to the formation of the intermediate products Pr(OH)(CH_3COO)_2, PrO(CH_3COO) and Pr_2O_2CO_3. Results obtained indicate that praseodymium acetate decomposes into a number of intermediate products whose chemical structure is independent on the gas atmosphere applied, but the kinetics of their formation and subsequent decomposition is considerably enhanced in O_2 atmosphere. The final product at 700℃ was found to be praseodymium oxide Pr_6O_(11) in O_2 and N_2, but mixed with minority Pr_2O_3 in H_2 atmosphere. Surface texture and 2-propanol decomposition activity of the final products at 700℃ were determined by means of N_2 sorptiometry and in situ IR spectroscopy. The final products in O_2 and N_2 were slightly more active catalysts toward 2-propanol decomposition the latter was of higher selectivity toward the alcohol dehydration, which is suggested to be correlated with the evolution of a narrower mesoporous structure on its surface.