Thermal decomposition mechanism of disilane

Thermal decomposition of disilane was investigated using time-of-flight (TOF) mass spectrometry coupled with vacuum ultraviolet single-photon ionization (VUV-SPI) at a temperature range of 675-740 K and total pressure of 20-40 Torr. Si(n)H(m) species were photoionized by VUV radiation at 10.5 eV (118 nm). Concentrations of disilane and trisilane during thermal decomposition of disilane were quantitatively measured using the VUV-SPI method. Formation of Si(2)H(4) species was also examined. On the basis of pressure-dependent rate constants of disilane dissociation reported by Matsumoto et al. [J. Phys. Chem. A 2005, 109, 4911], kinetic simulation including gas-phase and surface reactions was performed to analyze thermal decomposition mechanisms of disilane. The branching ratio for (R1) Si(2)H(6) --> SiH(4) + SiH(2)/(R2) Si(2)H(6) --> H(2) + H(3)SiSiH was derived by the pressure-dependent rate constants. Temperature and reaction time dependences of disilane loss and formation of trisilane were well represented by the kinetic simulation. Comparison between the experimental results and the kinetic simulation results suggested that about 70% of consumed disilane was converted to trisilane, which was observed as one of the main reaction products under the present experimental conditions.     

Thermal decomposition of poly(1,4-dioxan-2-one)

To evaluate the feasibility of poly(1,4-dioxan-2-one) (PPDO) as a feed stock recycling material, the pyrolysis kinetics of PPDO were investigated. The pyrolysis of PPDO exclusively resulted in the distillation of 1,4-dioxan-2-one (PDO). From thermogravimetric measurements conducted at different heating rates, the kinetic parameters of the pyrolysis: activation energy, E_a=127 kJ mol⁻¹; order of reaction, n=0; and pre-exponential factor, A=2.3×10⁹ s⁻¹, were estimated by plural analytical methods. The estimates show that the decomposition of PPDO proceeds by unzipping depolymerization as main reaction and random degradation process with lower E_a and A values. Equivalent isothermal degradation curves calculated from the thermogravimetric curves were supported by experimental isothermal degradation data. The calculation that PPDO is converted smoothly into PDO at 270°C agrees with the reported ceiling temperature of PPDO.     

Thermal decomposition mechanism of dimethyl(acetylacetonato)gold(III): Quantum chemical modeling

Different mechanisms of the thermal decomposition of the complex [(CH₃)₂Au(acac)] and the subsequent formation of Au particles are considered using density functional theory. The first decomposition step is the intramolecular reductive elimination of the methyl groups yielding ethane and the complex [Au(acac)], which dimerizes into the dinuclear complex [Au₂(acac)₂] with an energy gain. The presence of the coordinatively unsaturated center [Au(acac)] results in a considerable decrease in the activation energy of decomposition of the complex [(CH₃)₂Au(acac)]. The [Au₂(acac)₂] dimer undergoes association, again with an energy gain, to form linear polymer chains with short Au-Au bonds, which act as the nanoparticle nucleation centers.     

Thermal decomposition of trans-chloro(2-allylphenyl)bis(triethylphospine)nickel(II)

Thermolysis of trans-chloro(2-allylphenyl)bis(triethylphosphine)nickel(II), I, in tetrachloroethylene has afforded indene as the major hydrocarbon product along with lesser amounts of allylbenzene and trans-β-methylstyrene. Organonickel products were trans-chloro(trichlorovinyl)bis(triethylphosphine)nickel(II), II, chloro[2-(trans-propenyl)phenyl]bis(triethylphosphine)nickel(II), III, and trans-dichlorobis(triethylphosphine)nickel(II). Compound III was the major product from thermolysis of I in benzene. Chloro[2-(cis-propenyl)phenyl]bis(triethylphosphine)nickel(II), IV, and III could be synthesized independently by treatment of chloro-2-(cis-propenyl)benzene and chloro-2-(trans-propenyl)benzene, respectively, with nickel acetylacetonate and triethylaluminium in the presence of triethylphosphine. Thermolysis of I in benzene containing allylbenzene led to the formation of trans-β-methylstyrene. The thermolysis of I in benzene in the presence of cis-1,4-hexadiene caused the skeletal rearrangement of the diene to trans-2-methyl-1,3-pentadiene. A catalyst derived from ethylenebis(triphenylphosphine)nickel(0) and hydrogen chloride isomerized allylbenzene to trans-β-methylstyrene.     

Thermal decomposition kinetics of bis(thiophene-2-carboxaldehyde thiosemicarbazonato) cobalt(II)

The thermal decomposition kinetics of thiophene-2-carboxaldehyde thiosemicarbazone complex of cobalt(II) has been studied using TG, DTG and DTA techniques. Its decomposition was subjected to critical evaluation using the equations of Freeman-Carroll, Horowitz-Metzger and Coats-Redfern and the kinetic parameters have been evaluated for each step of decomposition by the method of weighted least squares.

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Co(II) -2- , . -, - -. .

     

Thermal decomposition and carbonization mechanism of poly-para-phenyleneoxadiazole

Thermal decomposition and carbonization mechanism of poly-para-phenylene-1,3,4-oxadiazole were investigated using FT-IR, thermogravimetry, gas-analysis, XPS, ¹³C-CP/MASFT-NMR, and elemental analysis. At temperatures above 500°C, the decomposition reaction proceeds preferentially on the oxadiazole ring, eliminating p-aminocyanobenzene and p-dicyanobenzene. Formation of carbodiimide compounds and their coupling followed in residual compounds, whose products are important intermediates leading to a planar and polyconjugated nitrogen-containing (e.g., graphite-like) carbon precursor.     

Thermal decomposition mechanism of synthesized copper octoate

Present study describes the synthesis and characterization of copper octoate. Attenuated total reflectance–Fourier transformation infra red (ATR–FTIR) and energy dispersive X-ray (EDX) spectrometric techniques have been used for the characterization of the synthesized compound. The surface morphology of the compound has been studied using scanning electron microscopy (SEM). Thermal behavior and decomposition mechanism of copper octoate has been explained on the basis of simultaneous thermo-gravimetry–differential thermal analysis–evolved gas analysis (TG–DTA–EGA) and high temperature X-ray diffraction (HTXRD) measurements. Copper octoate is stable up to 250 °C. The decomposition process consists of two overlapping steps. A plausible decomposition mechanism is proposed and details of the studies carried out are being discussed here.     

Thermal decomposition of hydrazinium(2+) hexafluorozirconate(IV) and hexafluorohafnate(IV)

A study of the thermal decomposition of N₂H₆ZrF₆ and N₂H₆HfF₆ showed that in the first step N₂H₅ZrF₅ and N₂H₅HfF₅ are formed. In the second step the former gives NH₄ZrF₅ as an intermediate, but an analogous hafnium complex cannot be obtained in a pure state. The end products of the decompositions are the corresponding tetrafluorides. The intermediates were isolated and characterized by chemical analysis X-ray diffraction patterns and vibrational spectroscopy.     

Thermal decomposition of polystyrene-b-poly(2-vinylpyridine) coordinated to co nanoparticles

Direct pyrolysis mass spectrometry analyses of polystyrene-block-poly(2-vinylpyridne), PS-b-P2VP, indicated that the thermal degradation of each component occurred independently through the decomposition pathways proposed for the corresponding homopolymers; depolymerization for PS and depolymerization and loss of protonated oligomers for P2VP by a more complex degradation mechanism. On the other hand, upon coordination to cobalt nanoparticles, thermal decomposition of the P2VP blocks was initiated by loss of pyridine units, leaving an unsaturated and/or crosslinked polymer backbone that degraded at relatively high temperatures.     

Thermal decomposition mechanism of tenofovir disoproxil fumarate

Tenofovir disoproxil fumarate (TDF) is an antiretroviral medication widely used to prevent and treat HIV/AIDS and to treat chronic hepatitis B. In this paper, thermal decomposition processes of TDF were measured with thermogravimetry, differential scanning calorimetry and thermogravimetric analysis coupled with Fourier transform infrared spectroscopy. The IR spectra, high-performance liquid chromatography and liquid chromatography mass spectrometry of TDF and the residues of its thermal decomposition at various temperatures were determined. The molecular bond orders were calculated using an ab initio method from the GAMESS program of quantum chemistry. The mechanism of thermal decomposition was discussed. The results indicated that the thermal decomposition of TDF is a three-step process, the initial step of thermal decomposition of TDF is the decomposition of carboxylic ester, the first stage mainly is the decomposition of the phosphoric disoproxil section, and the second stage mainly is the decomposition of the tenofovir section and partially goes through adenine stage. The initial decomposition temperature in either nitrogen or air is 138 °C, and the thermal stability of TDF is not very good under routine temperature.

     

Thermal and electron-induced decomposition of 2-butanol on Pt(111)

The adsorption, thermal evolution, and electron irradiation of 2-butanol on Pt(111) were investigated with reflection absorption infrared spectroscopy (RAIRS). A simulated vibrational spectrum of a single 2-butanol molecule was calculated using density functional theory to facilitate vibrational assignments. Exposures of 0.2 Langmuir (L) and lower result in both isolated 2-butanol molecules with minimal lateral interactions and hydrogen-bonded clusters. The thermal evolution following a 4.0 L exposure shows that the hydrogen-bonded multilayer desorbs around 170 K, leaving a 2-butanol monolayer where hydrogen bonding still exists. At 190 K, a new feature at 1699 cm(-1) is attributed to the formation of butanone. Irradiation with 750 or 100 eV electrons leads to 2-butanol desorption and partial conversion to butanone, as indicated by the appearance of a peak at 1709 cm(-1).     

Thermal decomposition of Cu(II) adipate

The kinetics of isothermal decomposition of Cu(CH₂CH₂COO)₂ were studied at 483–503 K. The end-product was identified as CuO by X-ray diffraction and chemical analysis. The kinetics follow the Prout-Tompkins equation with an activation energy of 191 ± 10 kJ/moIe. The activation energies and the order of reaction were also evaluated from analysis of the DTG, DTA and TG curves of the sample.     

Thermal decomposition of ammonium fluoromanganates(III)

The thermal decomposition of ammonium fluoromanganates (III) has been investigated in air and argon by simultaneous thermogravimetry and differential thermal analysis. Chemical analysis, X-ray powder data, and infrared spectra have been employed to characterise the intermediate and final products. The thermal decomposition can be described by the sequence (NH₄₃MnF₆ → (NH₄)₂MnF₅ → NH₄MnF₄ → MnF₂. Although penta- and tetra-fluoromanganates are well-defined compounds, the intermediate states could not be separated. In addition, a high temperature form of ammonium hexafluoromanganate has been observed.     

Thermal decomposition of potassium carbonatooxoperoxovanadate(V)

The thermal decomposition of K₃[V(CO₃)O(O₂)₂] was studied under isothermal, dynamic and quasi-isobaric-isothermal condition. A mixture of K₄V₂O₇ and K₂CO₃ was identified as the primary product of thermal decomposition. Under experimental conditions not allowing a continuous loss of volatile products, the reaction of K₄V₂O₇ with CO₂ gives KVO₃ and K₂CO₃.

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Zusammenfassung Unter isothermen, dynamischen und quasi-isobaren Bedingungen wurde die thermische Zersetzung von K₃[V(CO₃)O(O₂)₂] untersucht. Als Primärprodukt der thermischen Zersetzungsreaktion wurde ein Gemisch aus K₄V₂O₇ und K₂CO₃ festgestellt. Wird unter experimentellen Bedingungen das Entweichen flüchtiger Produkte verhindert, so gibt die Reaktion von K₄V₂O₇ mit CO₂ die Produkte KVO₃ und K₂CO₃.

     

Thermal decomposition of barium(II) tetraphenylborate

Barium(II) tetraphenylborate, Ba(Bph₄))₂·4H₂O was prepared, and its decomposition mechanism was studied by means of TG and DTA. The products of thermal decomposition were examined by means of gas chromatography and chemical methods. A kinetic analysis of the first stage of thermal decomposition was made on the basis of TG and DTG curves and kinetic parameters were obtained from an analysis of the TG and DTG curves using integral and differential methods. The most probable kinetic function was suggested by comparison of kinetic parameters. A mathematical expression was derived for the kinetic compensation effect.     

Thermal decomposition of copper(II) benzenedicarboxylates

The conditions and products of thermal decomposition of copper(II) benzenedicarboxylates in air atmosphere were studied at heating rates of 10 and 5 deg · min^–1. At a heating rate of 10 deg · min^–1, the o- and p-phthalate of copper(II) lose the crystallization water in two steps and the anhydrous complexes then decompose directly to CuO. Copper(II) m-phthalate loses crystallization water in one step to give the dihydrate, which then decomposes directly to CuO. When heated at 5 deg · min^–1 the m- and p-phthalates of copper(II) decompose in the same way, whereas the anhydrous o-phthalate decomposes to CuO through Cu₂O.

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Zusammenfassung Die Umstände und Produkte der thermischen Zersetzung von Kupfer(II)-benzoldicarboxylaten wurden in Luftatmosphäre bei einer Aufheizgeschwindigkeit von 10 bzw. 5 grd/min untersucht. Bei einer Aufheizgeschwindigkeit von 10 grd/min geben Kupfer(II)-o- und pphthalat ihr Kristallwasser in zwei Stufen ab, die wasserfreien Komplexe zerfallen anschliessend unmittelbar zu CuO. Kupfer(II)-m-phthalate geben Kristallwasser in einem Schritt ab und bilden dabei ein Dihydrat, was anschliessend direkt zu CuO zerfällt. Bei einer Aufheizgeschwindigkeit von 5 grd/min zeigt das m- und p-Phthalat des Kupfers(II) die gleichen Zersetzungserscheinungen, wogegen wasserfreies o-Phthalat sich zu CuO über die Zwischenstufe Cu₂O zersetzt.

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10 5 . 10 - - , . - , , . 5 - - , - .

     

Thermal decomposition of poly(tert-butyl N-vinylcarbamate)

Pyrolysis of poly(tert-butyl N-vinylcarbamate) at 185–200°C in bulk yields a rigid foam containing cyclic urea units, primary amine units, and a small amount of urea crosslinks. The yield of primary amine units (ca. 13%) and the yields of carbon dioxide (ca. 57%), isobutylene (ca. 57%), and tert-butanol formed in this reaction indicate that it involves pairwise decomposition of adjacent carbamate units to form cyclic urea units, tert-butanol, carbon dioxide, and isobutylene. The vinyl amine units are formed from carbamate units that become flanked by urea units. The amounts of amine units and residual carbamate units were determined as a function of degree of pyrolysis by an ion-exchange technique and agreed with values expected for a random cyclization process. The pyrolyzed polymers are useful as ion-exchange resins and as rigid foams having good thermal stability.     

Thermal decomposition of cerium(III) perchlorate

Thermal decomposition of Ce(ClO₄)₃ ? 9H₂O and Ce(ClO₄)₃ to give cerium(IV) dioxide in the temperature range 240–460°C was studied by DSC–TGA, X-ray powder diffraction, IR and mass spectroscopy. The thermolysis of these salts was shown to proceed through the stage of formation of intermediate product supposedly cerium oxoperchlorate. The thermal decomposition of cerium(III) perchlorate hydrate at 460°C leads to formation of nanocrystalline cerium dioxide with particle size of 13 nm.     

Thermal decomposition of Ammonium paramolybdate (APM)

Journal of Thermal Analysis and Calorimetry - The course of the thermal decomposition of APM was studied in vacuo and in air or argon atmosphere. The differences between vacuum and atmospheríc...