Abstract
The non-isothermal dehydration and decomposition of manganese malonate dihydrate (C 3H 2O 4Mn·2H 2O) were studied from ambient temperatures up to 450°C. Thermal analyses, TG, DTG, DTA and DSC, were carried out in dynamic atmospheres of N 2, H 2 and in air (except for DSC, where air was excluded). Solid decomposition products were identified using IR spectroscopy and X-ray diffractometry. MnO was found to be formed in N 2 and in H 2 atmospheres, while Mn 3O 4 was identified as the final solid product in air. Gas chromatography was used to identify the gaseous decomposition products (in N 2) as CO 2 and acetone, together with traces (≤2%) of acetic acid. Above 300°C, two other unidentified products were detected, which suggested that a catalytic gas-phase reaction took place on the surface of the MnO product. Using IR spectroscopy, manganese acetate (or basic manganese acetate (CH 3COO) 2Mn·OH) was identified, as a reaction intermediate. Kinetic (Δ E and ln A) and thermodynamic (Δ H, C p and Δ S) parameters of the dehydration and the decomposition processes are given. The mechanism of the decomposition is also discussed.
Published Version
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