Final Decomposition Products Research Articles

An in situ structural study of the thermal decomposition reactions of the ammonium thiomolybdates, (NH4)2Mo2S12·2H2O and (NH4)2Mo3S13·2H2O

A combined in situ Mo K-edge extended X-ray absorption fine structure (EXAFS) and X-ray powder diffraction study has been carried out to follow the evolution of structure in the thermal decomposition of the ammonium thiomolybdates, (NH4)2Mo3S13·2H2O and (NH4)2Mo2S12·2H2O, under nitrogen. Additional information on the course of the decomposition reactions has been obtained from thermogravimetric and differential thermal analysis, and from IR spectroscopy. Molybdenum–molybdenum bonded triangular units are found to persist in all the amorphous intermediate decomposition products of (NH4)2Mo3S13·2H2O, and are also formed during the decomposition of (NH4)2Mo2S12·2H2O. Structural models for the intermediates are presented. The final decomposition product in both cases is poorly crystalline MoS2.

Products of the Radiation-Chemical and Thermal Decomposition of Mercury Fulminate

The products of the radiation-chemical and thermal decomposition of mercury fulminate were examined by IR spectroscopy and X-ray diffraction analysis. Upon radiolysis to 20% conversion, the fulminate ion underwent decomposition (G (decomposition) = 20 molecule/100 eV) with the formation of HgO (G = 9 ± 1 molecule/100 eV), CN– ions, and CO2. The final solid products of the radiolysis are Hg(CNH)2, a cyanide complex, the mercury carbonate oxide HgCO3 · 3HgO, the mercury cyanide oxide Hg(CN)2 · HgO, and paracyanogen (CN)n. In the thermolysis, the final solid products of decomposition are the mercury carbonate oxide HgCO3 · 2HgO, a cyanide complex, and the cluster HgnCmNoOp.

Thermoanalytical and IR-spectral Investigation of Mg(II) Complexes with Heterocyclic Ligands

Thermogravimetry (TG), differential thermal analysis (DTA) and other analytical methods have been applied to the investigation of the thermal behaviour and structure of the complexes Mg(pc)(na)3⋅3H2O (I), Mg(pc)(py)2⋅2H2O (II),Mg(pc)(pic)2⋅2H2O (III) and Mg(pc)(caf)2⋅4H2O (IV), where pc=2,6- pyridinedicarboxylate, na=nicotinamide,py=pyridine, pic=γ-picoline and caf=caffeine. The thermal decomposition of these compounds is multi-stage processes. The chemical composition of the complexes, the solid intermediates and the resultant products of thermolysis have been identified by means of elemental analysis and complexometric titration. Schemes of destruction of these complexes are suggested. Heating of these compounds first resulted in a release of water molecules. In complexes I, II and IV the loss of the molecular ligands (na, py and caf) occur (on the TG curves) in one step (-2na, -2py and -2caf) and in complex III in two steps (-pic, -pic). The final product of the thermal decomposition was MgO. The thermalstability of the complexes can be ordered in the sequence: IV<I<III<II. Nicotinamide, pyridine, γ-picoline and caffeine were co-ordinated to Mg(II) through the N atom of the respective heterocyclic ring. IR data suggested a unidentate co-ordination of carboxylates to Mg(II) in complexes I–IV.

TG and DTA Evaluation of Cobalt Salts and Complexes Mixed with Activated Carbon

The thermal decomposition process of mixtures of CoC2O4⋅2H2O (COD) or Co(HCOO)2⋅2H2O (CFD) or [Co(NH3)6]2(C2O4)3⋅4H2O (HACOT) with activated carbon was studied with simultaneous TG–DTG–DTA measurements under non-isothermal conditions in argon and argon/oxygen admixtures. The results show that the thermal decomposition of the studied mixtures in Ar proceeds in the same manner. It begins with the salt decomposition to Comet+CoO mixture followed by (T>680 K) the simultaneous reduction of CoO to Cometand carbon degasification. The final product of the thermal decomposition of COD-C and CFD-C mixtures, identified by XRD, is β-Co. Cobalt contents determined in the final products fall in the range 71–78 mass%. The rest is amorphous residual carbon. In Ar/O2 admixtures the end product is Co3O4 with ash admixture.

Thermal Behaviour of Ammonium Oxofluorotitanates(IV)

The thermal behaviour of ammonium oxofluorotitanates (NH4)3TiOF5, (NH4)2TiOF4 and NH4TiOF3 was investigated by thermoanalytical, X-ray and IR spectroscopic methods. The first decomposition stages under quasi-isobaric conditions are characterized by the formation of (NH4)2TiF6 and ammonium oxofluorotitanate with the less content of ammonium and fluorine than in the initial compound. The decomposition process is accompanied by the Ti(IV) reducing due to ammonia evolved. The new ammonium oxofluorotitanate of high volatility was isolated and characterized. Ammonium-containing non-stoichiometric titanium oxyfluorides are the final products of thermal decomposition of ammonium oxofluorotitanates.

Synthesis, Characterization and Thermal Decomposition of Hydroxylammonium Uranyl Acetate

The synthesis of hydroxylammonium uranyl acetate is described. The identity of the synthesized compound was confirmed by chemical and infrared analysis. The intermediates and final products of the thermal decomposition were identified by means of thermogravimetric analysis, differential thermal analysis and X-ray diffraction. The thermal decomposition of hydroxylammonium uranyl acetate involves several steps. Two of them are due to decomposition of this compound to UO2 via UO2(CH3COO)2, and the third to the partial oxidation of UO2 to UO3 and the formation of U2O8 in the solid state at higher temperature.

Syntheses, Structures, and Thermal Expansion of Germanium Pyrophosphates

α-Ge(HPO4)2·H2O has been hydrothermally prepared and its thermal behavior has been studied by DTA and thermodiffractometry. Three pyrophosphates can be obtained on heating at high temperature. α-GeP2O7 is protocrystalline with a layered structure related to that of the pristine material. α-GeP2O7 transforms to β-GeP2O7 above 950°C and this yields γ-GeP2O7 above 1000°C. However, γ-GeP2O7 could not be prepared as single phase at high temperature and ambient pressure because P2O5 is partly released leading to a contamination with Ge5O(PO4)6 which is the final thermal decomposition product. γ-GeP2O7 has been synthesized as a single phase by heating α-GeP2O7 at 20 kbar and 1000°C. γ-GeP2O7, previously reported as cubic, is monoclinic with a=22.8647(4) Å, b= 22.8783(4) Å, c=22.9429(4) Å, β=90.328(1)°, V=12001.3(4) Å3 and symmetry P21/c or lower. γ-GeP2O7, with a simple stoichiometry, crystallizes in a very large unit cell with at least 26 Ge, 54 P, and 190 O crystallographically independent atoms. This complex superstructure is caused by the ordered pattern of the P–O–P bent groups. The 31P MAS-NMR profiles of γ-GeP2O7, β-GeP2O7, and Ge5O(PO4)6 are reported and discussed. The thermal expansion of γ-GeP2O7 is also described.

Decomposition of rhodium and iridium complexes of tripodal phosphine derivatives studied by thermal analysis

Thermal behaviour of five or six-coordinate rhodium and iridium complexes of two tripodal phosphines, CH 3C(CH 2PPh 2) 3 and CH 3C{CH 2P( m-CF 3C 6H 4) 2} 3, and their mixed-ligand complexes containing Cl, CO and MeCN was studied by TG, DTA and DTG in dynamic nitrogen atmosphere. The plain complexes exhibit very high thermal stability and degradation of the phosphine ligands follow a complicated process, while the first stage of the mixed-ligand complexes corresponds to removal of CO or MeCN and decomposition of the phosphine ligands occurs in the subsequent stages. All complexes undergo complete decomposition to form the respective metals as the final decomposition product. It was found that iridium complexes showed much higher thermal stability than their rhodium analogues.

Dissociation of nitrogen oxides under the action of pulsed electron beams

The decomposition of nitrogen oxides NOx in model gas mixtures ionized by microsecond pulsed electron beams was studied. The main decomposition mechanism is the dissociation of oxides caused by the interaction with atomic nitrogen. The final decomposition products are molecular oxygen and nitrogen.

Thermal and IR properties of Mg(II) complexes with heterocyclic ligands

Thermogravimetry (TG), differential thermal analysis (DTA) and other analytical methods have been applied to the investigation of the thermal behavior and structure of the compounds Mg(pc)(na) 2·2H 2O ( I), Mg(pc)(Et 2na) 2·3H 2O ( II), Mg(pc)(mpc) 2·H 2O ( III) and Mg(pc)(ron)·2H 2O ( IV), where pc=2,6-pyridindicarboxylate, na=nicotinamide, Et 2na= N, N-diethylnicotinamide, mpc=methyl-3-pyridyl carbamate and ron=3-pyridylcarbinol (ronicol). Thermal decomposition of these compounds are multi-stage processes. The composition of the complexes and the solid state intermediate and resultant products of thermolysis had been identified by means of elemental analysis and complexometric titration. The possible scheme of destruction of the complexes is suggested. Heating the compounds first results in a release of water molecules. In complexes I, II and IV the loss of the molecular ligands (na, Et 2na and ron) occur (on the TG curves) in one step (−2na, −2Et 2na and −ron) and in complex III in two steps (−mpc, −mpc). The final product of the thermal decomposition was MgO. The thermal stability of the complexes can be ordered in the sequence: II< III< I< IV. Et 2na, na, and ron were coordinated to Mg(II) through the nitrogen atom of the respective heterocyclic ring. IR data suggest to a unidentate coordination of carboxylates to Mg(II) in complexes I– IV.

Monitoring of radical thermocatalyzed breakdown of polychlorinated compounds

Disposal of polychlorobiphenyls (PCBs) is a current problem still far from a really satisfactory solution. Because of the wide use and the chemical inactivity, the PCB amount to be treated is considerably large. In this paper, the setting-up of a methodical catalytic pyrolysis of polychlorinated compounds is proposed. The monitoring of the final decomposition products by analytical techniques, such as GC and coupled TG-FTIR, allowed to optimize the reaction temperature: the encouraging results, the lower operative temperatures with respect to previous systems and the favourable prospects regarding the environmental impa ct make this methodology open to practical applications at a relative low cost.

Thermal Studies on Solid Complexes of Uracil With Some Divalent Transition Metal Ions

The thermal behaviour of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pd(II) complexes of uracil was studied by TG, DTG and DTA in a dynamic nitrogen atmosphere. Two processes occur in the isolated uracil complexes: dehydration and pyrolytic decomposition. In the hydrated complexes, the first stage observed was the loss of water molecules, which was followed by decomposition of the uracil. The thermal dehydration of the complexes occurred in from one to three steps. The final decomposition products were found to be the respective metal oxides, except in the cases of the Co(II) and Pd(II) complexes, which produced metallic cobalt and palladium, respectively. The order of reaction and energy of activation for the dehydration stage were evaluated.

Kinetics And Mechanism of The Non-isothermal Decomposition. Some Ni(II)-carboxylate-imidazole ternary complexes

The thermal decomposition of some Ni(II)-carboxylate-imidazole complexes in a nitrogen atmosphere was studied non-isothermally. From the non-isothermal thermoanalytical data, it was found that these complexes decompose through a stepwise release of imidazole molecules and/or CO ones forming unstable intermediates which produce metal oxide or the metal as a final decomposition product. TG in conjunction with DTG were used to evaluate the kinetic and thermodynamic parameters of the decomposition reaction. The kinetic studies were performed employing a computer-oriented kinetic analysis of each set of W-T data obtained under constant heating rate. The diffusion processes are the decisive mechanisms for the decomposition. The values of ΔE, A, ΔH, ΔS and ΔG for activation were calculated for the complexes and correlated to variation in their structure.

Formation and surface characterization of thulium oxide catalysts

Thulium oxide, Tm2O3, was obtained as a final product of the thermal decomposition of Tm(CH3COO)3·4H2O. The decomposition steps up to 800°C were characterized by TG, DTA, XRD, SEM, GC-MS and gas- and solid-phase IR spectroscopy. The results showed that Tm(CH3COO)3 ·4H2O dehydrates completely in two overlapping steps at 90 and 110°C and decomposes to Tm2O3 at 540°C through a non-crystalline intermediate Tm(OH)(CH3COO)2 at 350°C, Tm(O)(CH3COO) at 375°C and Tm2O2CO3 at 400°C. The oxides obtained at 600 and 800°C were subjected to texture analysis and pyridine adsorption. The results revealed that the oxide obtained at 600°C has a higher surface area of 49.7 m2 g−1 with larger pores than that obtained at 800°C (SBET=32.8 m2 g−1). On the other hand, the oxide obtained at 600°C has a basic surface character and contains at least two different Lewis acid sites as indicated from pyridine adsorption. The gaseous decomposition products as identified by gas-phase IR and GC-MS are water vapour, acetic acid, ketene, acetone and methane.

Thermal Decomposition of Mg(II) Complexes with Ronicol

Abstract The thermal decomposition of the complexes Mg(Clac)2 (ron)2 3H2 O(I), Mg(Cl2 ac)2 (ron)2 3H2 O(II) and Mg(Cl3 ac)2 (ron)2 3H2 O(III), where Clac =ClCH2 COO- , Cl 2 ac =Cl2 CHCOO- , Cl 3 ac =Cl3 CCOO- and ron =3-pyridylcarbinol (ronicol) had been investigated in air atmosphere in temperature range 20–1000C by means of TG and DTA. The composition of the complexes and the solid state intermediate and resultant products of thermolysis had been identified by means of elemental analysis and complexometric titration. The possible scheme of destruction of the complexes is suggested. The final product of the thermal decomposition was MgO. The thermal stability of the complexes can be ordered in the sequence: I<III<II. IR data suggest that ronicol was coordinated to Mg(II) through the nitrogen atom of its heterocyclic ring.

NO-Mediated aromatic nitration during decomposition of phenolic S-nitrosothiols in non-aqueous aerobic medium.

Five novel S-nitrosothiol compounds (6-10) derived from L-cysteine were generated in solution and their decomposition rate was followed by UV spectroscopy. In acetonitrile, compounds 9 and 10 were the most stable of this series with a half-life of 24 h. The final organic decomposition products of the five S-nitrosothiols were also analysed. Derivatives 8, 9, and 10, possessing a phenolic hydroxyl group, afforded an unexpected decomposition pathway, with nitration of aromatic ring occurring in non-aqueous media. A mechanism involving a phenoxy radical seems to be implicated.

Thermal and spectral properties of Mg(II) and Cu(II) complexes with heterocyclic N-donor ligands

The thermal decompositions of the complexes Mg(pc)·H 2O ( I), Mg(pc)·3H 2O ( II), Mg(pc)·4H 2O ( III), Mg(ac) 2·(na) 3.4H 2O ( IV) and Cu(pc)·5H 2O ( V), (where pc=2,6-pyridinedicarboxylate, ac=CH 3COO − and na=nicotinamide) have been investigated in an atmosphere of air in the temperature range 20–1000°C by means of TG and DTA. Though complexes I–III are similar (differ only in the number of water molecules), the kinetics of their thermal decomposition were different. The chemical composition of the complexes, the solid intermediates and the resultant products of thermolysis have been identified by means of elemental analysis and complexometric titration. Schemes of destruction of these complexes are suggested. Heating of these compounds first resulted in a release of water molecules. The thermal stability of these complexes can be ordered in the sequence: II=IV<III<I=V. The final products of the thermal decomposition were MgO (from complexes I–IV) and CuO (from complex V). Nicotinamide was coordinated to Mg(II) through the nitrogen atom of its heterocyclic ring. IR data suggested a unidentate coordination of carboxylates to Mg(II) and to Cu(II) in complexes I–V.

Novel donors of nitric oxide derived of S-nitrosocysteine possessing antioxidant activities.

Novel S-nitrosothiols possessing a phenolic function were investigated as nitric oxide (NO) donors. A study of NO release from these derivatives was carried out by electron spin resonance (ESR). All compounds gave rise to a characteristic three-line ESR signal in the presence of the complex [Fe(II)(MGD)2], revealing the formation of the complex [Fe(II)(MGD)2(NO)]. Furthermore, tests based on cytochrome c reduction were performed in order to study the ability of each phenolic disulfide, the final organic decomposition product of S-nitrosothiols, to trap superoxide radical anion (O2-). This study revealed a high reactivity of 1b and 3b towards O2-. For these two compounds, the respective inhibitory concentration (IC) 50 values were 92 microM and 43 microM.

Kinetics of hydrogen induced diffusion phase transformation in intermetallic compound TbFe 2

The effect of temperature on the rate of isothermal diffusion phase transformation in the intermetallic compound TbFe 2 in hydrogen atmosphere has been investigated by means of magnetic and powder X-ray diffractometry methods. It was shown, that in the temperature range of 450–580°C the rate of decomposition was increased with increasing temperature. The final products of decomposition were TbH 2 and α-Fe.

Thermal properties of mixed-ligand bis(hydrazine) and bis(ethylenediamine) complexes of cobalt, nickel and copper saccharinates

The thermal decomposition of mixed-ligand complexes of cobalt, nickel and copper saccharinates with hydrazine and ethylenediamine were studied in static air atmosphere. The first decomposition stage usually corresponds to dehydration, dehydrazination or deethyleneamination. Kinetic analysis of data indicates that these stages follow a low energetic process. All complexes form metal saccharinates as intermediates and the final decomposition products are found to be the respective metal oxides.