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(CnH2n+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

Thermal decomposition of heavy rare-earth butanoates, Ln(C₃H₇CO₂)₃ (Ln = Er, Tm, Yb and Lu) in argon

The thermal behaviour of Ln(C$_{3}$H$_{7}$CO$_{2})_{3}$ (Ln = Er, Tm, Yb or Lu) was studied in argon from room temperature by means of thermogravimetry and differential thermal analysis up to 1400 °C, by infrared spectroscopy, hot-stage optical microscopy and X-ray diffraction. Melting prior to decomposition was observed in all four compounds, but its course depends on the rare-earth element. Decomposition to sesquioxides proceeds via the formation of dioxymonocarbonates (Ln$_2$O$_2$CO$_3$) and release of 4-heptanone (C$_3$H$_7$COC$_3$H$_7$) as well as carbon dioxide (CO$_2$) without evidence for an intermediate oxobutanoate stage. During the decomposition of Ln$_2$O$_2$CO$_3$ into the respective sesquioxides (Ln$_2$O$_3$), an intermediate plateau extending from approximately 550 to 850 °C appears in the TG traces. The overall composition during this stage corresponds approximately to Ln$_2$O$_{2.8}$(CO$_3$)$_{0.2}$, but the state is more probably a mixture of Ln$_2$O$_2$CO$_3$ and Ln$_2$O$_3$. The stability of this intermediate state seems to decrease with the mass of the rare-earth elements. Complete conversion to Ln$_2$O$_3$ is reached at about 1100 °C. The overall thermal decomposition behaviour of the title compounds is different from previous reports for other rare-earth butanoates

Thermal decomposition of Yttrium(III) isovalerate in argon

The thermal behaviour of yttrium(III) isovalerate (Y(C$_4$H$_9$CO$_2$)$_3$) was studied in argon by means of thermogravimetry, differential thermal analysis, FTIR-spectroscopy, hot-stage optical microscopy and X-ray diffraction with a laboratory Cu-tube source as well as with a synchrotron radiation source. Two structural transitions take place in the solid state at 100 °C and 140 °C. They are followed by the decomposition of the isovalerate salt with release of gaseous products consisting of CO$_2$ and 2,6-dimethyl-4-heptanone and formation of Y$_2$O$_2$CO$_3$ between 320 °C and 440 °C. Above 440 °C, Y$_2$O$_2$CO$_3$ is slowly converted to Y$_2$O$_3$ with release of CO$_2$. The decomposition is complete at about 900 °C

Thermal decomposition of lanthanum(III) butyrate in argon atmosphere

The thermal decomposition of La(C3H7CO2)3·xH2O (x ≈ 0.82) was studied in argon during heating at 5 K/min. After the loss of bound H2O, the anhydrous butyrate presents at 135 °C a phase transition to a mesophase, which turns to an isotropic liquid at 180 °C. The decomposition of the anhydrous butyrate is associated to a solidification process. The final decomposition to La2O3 takes place via two intermediate products: La2O(C3H7CO2)4 and La2O2CO3 with release of CO2 and the symmetrical ketone C3H7COC3H7

Thermal decomposition of yttrium(III) hexanoate in argon

The thermal decomposition of yttrium(III) hexanoate (Y(C$_{5}$H$_{11}$CO$_{2}$)$_{3}$)·xH$_{2}$O in argon was studied by means of thermogravimetry, differential thermal analysis, IR-spectroscopy, X-ray diffraction at a laboratory Cu-tube source and in-situ experiments at a synchrotron radiation source as well as hot-stage optical microscopy. Dehydration occurs between 40 °C and 110 °C and is accompanied by a transition from solid to liquid crystalline state. At the onset of the main decomposition stage of the anhydrous Y(C$_{5}$H$_{11}$CO$_{2}$)$_{3}$), solidification takes place in the 315–335 °C range. Y(C$_{5}$H$_{11}$CO$_{2}$)$_{3}$) decomposes in a single step into Y$_{2}$O$_{2}$CO$_{3}$ with release of CO$_{2}$ and 6-undecanone between 280 °C and 490 °C. A side reaction appears to yield elemental carbon and volatile decane (C10H22). Y$_{2}$O$_{2}$CO$_{3}$ is converted to Y$_{2}$O$_{2}$CO$_{3}$ with release of CO$_{2}$ between 500 °C and 975 °C