Effects of olefins on the thermal decomposition of propane part V. Effect of butene-2-Cis

The thermal decomposition of butene-2-cis at low conversion and its effect on the pyrolysis of propane have been studied in the temperature range 779-812 K. It was established that 2-butene decomposes in a long-chain process, with the chain cycle (Besides the radical path, the molecular reaction can also play a role in the formation of the products.) The thermal decomposition of propane is considerably inhibited by 2-butene, which can be explained by the fact that the less reactive radicals formed in the reactions between the olefin and the chain-carrying radicals regenerate the chain cycle more slowly than the original radicals in the above chain cycle or in the reactions The reactions of the 2-propyl radical are further initiation steps. The ratios of the rate coefficients of the elementary steps of the decomposition (Table III) have been determined via the ratios of the products. Estimation of the radical concentrations indicated that only the methyl, 2-propyl and methylallyl radicals are of importance in the chain termination. On the basis of the inhibition-influenced curves, the role of the bimolecular initiation steps. could be clarified in the presence of 2-butene.     

Effect of olefins on the thermal decomposition of propane part I. The model reaction

Study of the thermal decomposition of propane at very low conversions in the temperature range 760–830 K led to refinement of the mechanism of the reaction. The quotient V/V characterizing the two decomposition routes connected with the 1- and 2-propyl radicals proved to depend linearly on the initial propane concentration. This suggested the occurrence of intermolecular radical isomerization: in competition with decomposition of the 2-propyl radical: The linearity led to the conclusion that the selectivity of H-abstraction from the methyl and methylene groups by the methyl radical is practically the same as that by the H atom. The temperature-dependence of this selectivity ( μ = kCH₃/kCH₂) was given by Further evaluation of the dependence gave the Arrhenius representation for the ratio of the rate coefficients of the above isomerization and decomposition reactions. Steady-state treatment resulted in the rate equation of the process, comparison of which with measurements gave further Arrhenius dependences.     

Effects of alkenes on the thermal decomposition of propane part II. Influence of ethylene

Experiments with propane-ethylene mixtures in the temperature range 760–830 K resulted in refinement of the role of ethylene inhibition in the decomposition of propane. The source of the rate-reducing effect of ethylene is the reaction This replaces the decomposition chains more slowly by means of the reactions than H-atoms do by direct H-abstraction from propane. Analysis of the ratios of the product formation rates showed that the selectivity of the ethyl radical for the abstraction of hydrogen of different bond strengths from propane was practically the same as that of the H-atom. The ratio of the rate constants of hydrogen addition to ethylene and methyl-hydrogen abstraction from propane by the H-atom (3) was determined as was that of the decomposition and the similar H-abstraction of the ethyl radical Interpretation of the influence of ethylene required the completion of the mechanism with further initiation of the reaction besides termination via ethyl radicals.     

High temperature thermal decomposition of propane

The thermal decomposition of propane has been studied by pulse chromatographic method within the temperature range of 975–1083 K. The kinetic parameters of the reaction have been determined.

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- 975–1083 . .

     

General remarks on the thermal decomposition of some drugs

The thermal decomposition of antituberculous, local anaesthetic and calcium salts of organic acids used as the drugs has been studied by differential thermal and thermogravimetric techniques. General characteristics of their thermal decomposition has been made. The effect of sample size over the range 20–200 mg and heating rate over the range 3–15 deg·min^?1 on the thermal degradation has been investigated. The values of the kinetic parameters has been also determined.     

Solvent effect on the kinetics and mechanism of the thermal decomposition oftris-oxalactocobaltate(III) complex

Summary The kinetics of the thermal decomposition of thetris-oxalactocobaltate(III) complex has been investigated in the presence of EtOH and (CH₂OH)₂ spectrophotometrically in the 50–70 ± 0.1 ° C range. The rate of the reaction decreases upon the addition of either of the alcohols to the reaction medium, whereas the activation energy increases. The thermodynamic parameters were calculated and are discussed in terms of the solvation effects. The influence of the dielectric constants of the solvent mixtures on the rate has been studied. A free radical mechanism is proposed and discussed.     

氢氧化镁分解动力学的研究

以硼泥为原料与硫酸反应制备出七水硫酸镁,以氢氧化钠为沉淀剂制备出符合标准HG/T 3607-2000的氢氧化镁.利用XRD,SEM和TEM对氢氧化镁进行了表征,DTA-TG对氢氧化镁的热分解动力学进行了研究.XRD结果表明:制备粉体为单一Mg(OH)2.SEM和TEM结果表明:样品为片状或针状纤维,片直径大小不一,在20～50 nm之间,针状纤维形状不规则,大小不一致,长度在20～100 nm之间.利用Kissinger法和Ozawa法计算出的氢氧化镁热分解反应活化能分别为135.14和141.61 kJ·mol-1.利用Coats-Redfern法和Dolye法判断氢氧化镁热分解反应机理函数为A1.5.     

Investigation of thermal decomposition kinetics of taurine

The non-isothermal thermal decomposition of taurine was investigated by means of thermogravimetric analysis (TG) and differential thermal analysis (DTA). The experimental data were treated using Flynn–Wall–Ozawa, Doyle, Kissinger, and ?atava–?esták methods, respectively. The results show that the non-isothermal thermal decomposition mechanism of taurine is classified as phase boundary reaction, and the mechanism function is the Mampel Power law with n = 1. The forms of both integral and differential for the mechanism function are $ G(\alpha ) = \alpha $ and $ f(\alpha ) = 1 $ , respectively. The activation energy and the pre-exponential factor are 167.88 kJ mol^?1 and 1.82 × 10¹³min^?1, respectively.     

A study on the kinetics of thermal decomposition of CaCO3

By means of TG, the thermal decomposition of the powdered CaCO₃ was tested with its various dispersities, range of size, and the different content of CO₂ in flowing nitrogen. Formulae for calculating the rate and time of decomposition were obtained.     

Phenomenological kinetics of the thermal decomposition of sodium hydrogencarbonate

Aiming to find rigorous understanding and novel features for their potential applications, the physico-geometrical kinetics of the thermal decomposition of sodium hydrogencarbonate (SHC) was investigated by focusing on the phenomenological events taking place on a single crystalline particle during the course of the reaction. The overall kinetics evaluated by systematic measurements of the kinetic rate data by thermogravimetry under carefully controlled conditions were interpreted in association with the morphological studies on the precursory reaction, mechanism of surface reaction, structure of the surface product layer, diffusion path of evolved gases, crystal growth of the solid product, and so on. The precursory reaction was identified as the decomposition of impurity, taking place at the boundary between the surface of the SHC crystal and the adhesive small SHC particles deposited on the surface. In flowing dry N(2), the thermal decomposition of SHC proceeds by two-dimensional shrinkage of the reaction interface controlled by chemical reaction with the apparent activation energy of about 100 kJ mol(-1), after rapid completion of the surface reaction and formation of porous surface product layer. Atmospheric CO(2) and water vapor influence differently on the overall kinetics of the thermal decomposition of SHC. Added gas phase of CO(2) slightly inhibits the overall rate because of the increasing contribution of the surface reaction. Under higher water vapor pressure, the physico-geometrical mechanism of the surface reaction changes drastically, indicating the preliminary reformation of reactant surface and the formation of needle crystals of solid product on the surface. The mechanistic change and extended contribution of the surface reaction result in the deceleration of the surface reaction and acceleration of the established reaction.     

Synthesis and thermal decomposition kinetics of Er(III) complex with unsymmetrical Schiff-base ligand

A new unsymmetrical, solid, Schiff base (H₂LLi) was synthesized using L-lysine, o-vanillin and salicylaldehyde. An Er(III) complex of this ligand [Er(H₂L)(NO₃)](NO₃)?·?2H₂O was prepared and characterized by elemental analysis, IR, UV and molar conductance. The thermal decomposition kinetics of the complex for the second stage was studied under non-isothermal conditions by TG and DTG methods. The kinetic equation may be expressed as, dα/dt?=?A?·?e^?E/RT ?·?1/2(1???α)[?ln(1???α)]^?1. The kinetic parameters (E,?A), activation entropy S ^≠ and activation free-energy G ^≠ were also determined.     

Synthesis and thermal decomposition kinetics of La(III) complexwith unsymmetrical Schiff base ligand

A new unsymmetrical solid Schiff base (LLi) was synthesized using L-lysine, o-vanillin and 2-hydroxy-l-naphthaldehyde. Solid lanthanum(III) complex of this ligand [LaL(NO₃)]NO₃·2H₂O have been prepared and characterized by elemental analyses, IR, UV and molar conductance. The thermal decomposition kinetics of the complex for the second stage was studied under non-isothermal condition by TG and DTG methods. The kinetic equation may be expressed as: dα/dt=Ae^−E/RT(1−α)². The kinetic parameters (E, A), activation entropy ΔS ^# and activation free-energy ΔG ^# were also gained.     

The thermal decomposition of azomethane. III. Kinetics of the noninhibited reaction

The thermal decomposition of azomethane (A) has been studied in a static system at temperatures between 250° and 320°C and at pressures between 5 and 402 torr, with particular attention to identification of products. Major products, in decreasing order of importance, were nitrogen, methane, ethane, methylethyldiimide, dimethylhydrazone, propane, tetramethylhydrazine, ethylene, methylpropyldiimide, and methylethylhydrazone. Carbon balance at the lowest pressure and highest temperature was 92%, but decreased with increasing pressure and decreasing temperature owing to the formation of a polymer. A fairly simple mechanism accounts reasonably well for a short chain in the decomposition, propagated by the radical CH₃N₂CH₂ (B), and for the five most abundant products, except ethane. It turns out that there is a second source of ethane, arising by C₂H₅ + A → C₂H₆ + B; this explains an anomalously high apparent activation energy for the reaction CH₃ + A → CH₄ + B. Ethyl radicals are also shown to be responsible for the formation of propane, ethylene, methylethylhydrazone, and methylpropyldiimide. The radical B decomposes to CH₃ + CH₂ + N₂, and the methylene radical (probably both singlet and triplet) is shown to yield C₂H₅ at low pressure and high temperature, and mostly polymer at high pressure and low temperature.     

The kinetics of thermal decomposition of bismuth oxohydroxolaurate

The bismuth salt of lauric (dodecanic) acidBi₆O₄(OH)₄(C₁₁H₂₃COO)₆ was studied earlier. This salt has layer structure (the interlaminardistance=37.50 Å), under heating this liquid-crystalline state has themesomorphic transformation, turns to the amorphous state, decomposes stepwisewith the formation of well-ordered layers of bismuth nanoparticles. DSC-curveswere used for the study of the decomposition kinetics in the area of decompositionwith small mass loss and exothermic effect (423–483 K).     

Mechanism and kinetics of the thermal decomposition of 5-aminotetrazole

The kinetics of 5-aminotetrazole thermal decomposition in the condensed phase at high heating rates (∼100 K/s) was studied by the dynamic mass spectrometric thermal analysis using a molecular beam sampling system, and the product composition was determined. Two routes of 5-aminotetrazole decomposition were distinguished, one yielding HN₃ and NH₂CN (route 1), and the other N₂ and CH₃N₃ (route 2). The activation energy and rate constant of 5-AT decomposition were determined for each route.     

Studies on the thermal decomposition kinetics and mechanism of ammonium niobium oxalate

Ammonium niobium oxalate was prepared and characterized by elemental analysis, XRD and FTIR spectroscopy analysis, which confirmed that the molecular formula of the complex is NH₄(NbO(C₂O₄)₂(H₂O)₂)(H₂O)₃. Dynamic TG analysis under air was used to investigate the thermal decomposition process of synthetic ammonium niobium oxalate. It shows that the thermal decomposition occurs in three stages and the corresponding apparent activation energies were calculated with the Ozawa–Flynn–Wall and the Friedman methods. The most probable kinetic models of the first two steps decomposition of the complex have been estimated by Coats–Redfern integral and the Achar–Bridly–Sharp differential methods.     

Effect of the solvent on the kinetics of thermal decomposition of acetylcyclohexylsulfonyl peroxide

The kinetics of the decomposition of acetylcyclohexylsulfonyl peroxide (ACSP) in CCl₄, benzene, toluene, ethylbenzene, cumene, acetonitrile, ethanol, and 2-propanol in an atmosphere of O₂ were studied at 40–70 °C. The rate constants (k ₀) and activation parameters of the monomolecular decomposition of ACSP were determined. A linear dependence between logA ₀ and activation energyE ₀ (compensation effect) was established. The dependence ofk ₀ on the nature of a solvent is described by the four-parameter Koppel-Palm equation. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 935–937, May 1997.