Thermal decomposition of the oxo-diperoxo-molibdenum (VI)-potassium oxalate
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Thermal decomposition of the oxo-diperoxo-molibdenum (VI)-potassium oxalate Dorina-Rodica Chambre´ • Adina-Maria Bodescu Cecilia Sıˆrghie
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Received: 30 November 2011 / Accepted: 17 August 2012 / Published online: 18 September 2012 Ó Akade´miai Kiado´, Budapest, Hungary 2012
Abstract The oxo-diperoxo-molibdenum(VI)-potassium oxalate, K2[MoO(O2)2(C2O4)] was synthesized using an adapted version of the method suggested by Dengel. The thermal behavior of the synthesized complex was investigated by simultaneous thermal analysis TG/DTG/DTA, in air or nitrogen atmosphere, to identify and characterize the mass-loss decomposition processes. In addition, for the characterization of the observed decomposition steps, the FT-IR spectra for the initial complex, evolved gaseous compounds and isolated complex at 230 and 430/383 °C in air/nitrogen atmosphere, were recorded. On the 35–500 °C temperature range, the K2[MoO(O2)2(C2O4)] complex presented three main decomposition steps, accompanied by mass-loss. The first degradation step is due to the elimination of one oxygen molecule, by the breaking of the peroxo groups, with the formation of an intermediary, like [MoO3L]. The other two degradation steps can be attributed to the decomposition of the organic ligand, with the final formation of a stable metallic oxide. Keywords Oxo-diperoxo-molibdenum(VI)-potassium oxalate Synthesis Thermal decomposition TG/DTG/DTA analysis FT-IR spectra
D.-R. Chambre´ C. Sıˆrghie (&) Research Development Innovation in Natural and Technical Sciences, Institute of ‘‘Aurel Vlaicu’’ University, Elena Dra˘goi 2, 310330 Arad, Romania e-mail: [email protected] A.-M. Bodescu Faculty of Food Engineering, Tourism and Environmental Protection, ‘‘Aurel Vlaicu’’ University, Elena Dra˘goi 2, 310330 Arad, Romania
Introduction During the last years, the transition metal complexes with peroxo and peroxo-carboxylate groups were synthesized and characterized due to their catalytic efficiency in oxidation reactions of organic compounds with double bonds between carbon atoms [1–3]. Peroxo complexes of molybdenum (VI), of [MoO(O2)L] and [MoO(O2)2L] types, where L-organic ligand, have a wide applicability in various areas (textiles and paper industry, etc.) [4, 5]. The oxo-diperoxo-molibdenum (VI)-potassium oxalate compound, proves to be a good catalyst for cellulose pulp bleaching [6]. In this context, the thermal behavior investigation of this complex is necessary. Recently, the thermoanalytical methods TG/DTG/DTA were frequently used to characterize the thermal decomposition of various types of Mo (VI) complexes [3, 7, 8]. These methods provide data that are important for practical use of the complexes, such as thermal stability and initial decomposition temperature. Sheikh et al. [7, 9] studying the thermal behavior of the oxo-diperoxo-molibdenum (VI) complexes with different organic ligand have reported that, in air atmosphere on 35–850 °C temperature range, all compounds have shown three degradation stages due to the breaking of peroxo groups and dec
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