Thermal behavior and decomposition of cerium(III) butanoate, pentanoate and hexanoate salts upon heating in argon

The thermal behavior and decomposition of Ce-butanoate monohydrate (Ce(C₃H₇CO₂)₃·H₂O), Ce-pentanoate (Ce(C₄H₉CO₂)₃) and Ce-hexanoate (Ce(C₅H₁₁CO₂)₃) were studied in a flow of argon while heating at 5 °C/min. By means of several techniques such as simultaneous TG-DTA, FTIR evolved gas analysis, in-situ x-ray diffraction using a synchrotron source and hot-stage microscopy, it was found that all three compounds undergo melting transitions prior to decomposition and that decomposition involves intermediate stages including at least a Ce₂O(C_nH_2n+1CO₂)₄ intermediate (n = 3, 4 or 5 for Ce-butanoate, pentanoate or hexanoate respectively). The final decomposition product consists of CeO₂, which is formed through a Ce-oxycarbonate. The Ce³⁺ → Ce⁴⁺ oxidation seems to proceed via Ce₂O₃ that first results from the decomposition of the oxycarbonate phase. During the whole decomposition process, the evolved gas species consist of CO₂ and symmetrical ketones.