Autocatalytic Decomposition Research Articles

Experimental Method on Rapid Identification of Autocatalysis in Decomposition Reactions

Many chemical substances will decompose in an autocatalytic manner, and such autocatalytic behavior can be identified through isothermal measurements, such as using differential scanning calorimetry(DSC) and microcalorimetry(C80). However, since it is difficult to predict the appropriate temperature for isothermal testing, it would be helpful to develop a simple and effective experimental method to distinguish autocatalytic decomposition. Based on the results of Roduit et al., a new technique for identifying autocatalysis is described herein, termed the"interruption and re-scanning"method. The decompositions of 2-ethylhexyl nitrate(EHN), 2,4-dinitrotoluene(2,4-DNT), dicumyl peroxide(DCP), and cumyl hydroperoxide(CHP) were assessed using both this new method and isothermal approach. Based on the results, the decompositions of EHN and DCP were found to proceed accord to the"nth order"law,whereas 2,4-DNT and CHP decomposed autocatalytically. We conclude that the interruption and rescanning method can be used to identify the characteristics of autocatalysis both quickly and effectively.

Barium peroxide nanoparticles: synthesis, characterization and their use for actuating the luminol chemiluminescence

Barium peroxide (BaO2) nanoparticles are prepared via microemulsion techniques, using concentrated hydrogen peroxide (perhydrol, 30%) as a polar micelle phase. The as-prepared BaO2 nanoparticles are characterized by SEM, STEM, XRD, and FT-IR to validate the particle size (40 nm in diameter) and phase purity (e.g., the absence of BaO, Ba(OH)2, and BaCO3). BaO2 nanoparticles are strong oxidizing agents due to in situ release of O2 as is proven by de-N-acetylation of Ampliflu Red and the strong red fluorescence of resorufin. Moreover, they can be used for luminol-driven chemiluminescence detection of Fe2+/Fe3+ (<0.05 mmol) as an alternative to H2O2. In comparison with conventional aqueous H2O2, BaO2 nanoparticles show a high storage stability (without autocatalytic decomposition) and a 5-times more intense chemiluminescence with luminol. Via fluorescence transfer, the chemiluminescence can also be shifted from blue (luminol) to green (fluorescein), which is at optimal eye sensitivity and therefore facilitates naked-eye detection. The newly prepared BaO2 nanoparticles as an active peroxide and strong oxidizing agent can be of potential interest for organic synthesis, CO2 adsorption, disinfection, wastewater treatment as well as for luminol-driven chemiluminescence detection of iron in analytical chemistry and criminology.

Estimation of the critical rate of temperature rise for thermal explosion of nitrocellulose using non-isothermal DSC

The expressions to calculate the critical rate of temperature rise of thermal explosion \( ({\text{d}}T / {\text{d}}t)_{{\text{T}_{\text{b}} }} \) for energetic materials (EMs) were derived from the Semenov’s thermal explosion theory and autocatalytic reaction rate equation of nth order, CnB, Bna, first-order, apparent empiric-order, simple first-order, Au, apparent empiric-order of m = 0, n = 0, p = 1 and m = 0, n = 1, p = 1, using reasonable hypotheses. A method to determine the kinetic parameters in the autocatalytic-decomposing reaction rate equations and the \( ({\text{d}}T / {\text{d}}t)_{{\text{T}_{\text{b}} }} \) in EMs when autocatalytic decomposition converts into thermal explosion from data of DSC curves at different heating rate was presented. Results show that (1) under non-isothermal DSC conditions, the autocatalytic-decomposing reaction of NC (12.97 % N) can be described by the first-order autocatalytic reaction rate equation dα/dt = 1016.00exp(−174520/RT)(1 − α) + 1016.00exp(−163510/RT)α(1 − α); (2) the value of \( ({\text{d}}T / {\text{d}}t)_{{\text{T}_{\text{b}} }} \) for NC (12.97 % N) when autocatalytic decomposition converts into thermal explosion is 0.354 K s−1.

Thermal stability evaluation of β-artemether by DSC and ARC

The thermal stability of β-artemether under dynamic, isothermal and adiabatic conditions were investigated by differential scanning calorimeter (DSC) and accelerating rate calorimeter (ARC), respectively. The dynamic DSC measurements at various heating rates (1, 2, 4 and 8°Cmin−1) displayed that β-artemether experienced polymorph transformation in the melting process. According to the isothermal DSC results at different temperatures 86, 88, 90 and 92°C, β-artemether decomposed after the completion of the melting and the polymorph transformation, and the thermal decomposition of β-artemether is hazardous for its characteristic of autocatalytic decomposition. The kinetics analysis dynamically and isothermally described by Friedman method indicated the thermal decomposition of β-artemether did not comply with a single mechanism. The ARC results showed that the pressure increased with the increase of temperature, and indicated obvious linear relationship. Based on the ARC data, the value of SADT of β-artemether in 50kg package was obtained.

Autocatalytic decomposition of carbonic acid

Long held to be unstable or metastable in the gas phase, carbonic acid has successfully been produced and identified in its gaseous form in recent decades. Theoretical studies have indicated that isolated carbonic acid in the gas phase may in fact be quite stable, its decomposition attributable to the catalytic effect of water molecules, either present or produced in a chain reaction by an initially slow decomposition. In this study, a previously unreported autocatalytic decomposition route is studied using high-accuracy ab initio quantum chemical methods. Results indicate that a carbonic acid dimer may react and decompose in a single-step, highly concerted reaction. The transition state of this reaction was characterized, and the reaction pathway was found to have significantly lower activation energy than the uncatalyzed decomposition, and comparable or lower energy than the water-catalyzed reaction. The results indicate that gaseous carbonic acid should be unstable even in the absence of water. © 2013 Wiley Periodicals, Inc.

A Window on Surface Explosions: Tartaric Acid on Cu(110)

Autocatalytic reaction mechanisms are observed in a range of important chemical processes including catalysis, radical-mediated explosions, and biosynthesis. Because of their complexity, the microscopic details of autocatalytic reaction mechanisms have been difficult to study on surfaces and heterogeneous catalysts. Autocatalytic decomposition reactions of S,S- and R,R-tartaric acid (TA) adsorbed on Cu(110) offer molecular-level insight into aspects of these processes, which until now, were largely a matter of speculation. The decomposition of TA/Cu(110) is initiated by a slow, irreversible process that forms vacancies in the adsorbed TA layer, followed by a vacancy-mediated, explosive decomposition process that yields CO2 and small hydrocarbon products. Initiation of the explosive decomposition of TA/Cu(110) has been studied by measurement of the reaction kinetics, time-resolved low energy electron diffraction (LEED), and time-resolved scanning tunneling microscopy (STM). Initiation results in a decrease...

Identification and Thermokinetics of Autocatalytic Exothermic Decomposition of 2,4-Dinitrotoluene

为研究2,4-二硝基甲苯（2,4-DNT）的热危险性及其分解反应的特征, 利用差示扫描量热仪（DSC）对该物质进行了动态扫描测试, 得到其起始分解温度T0范围为272.4-303.5℃, 分解热ΔHd约为2.22 kJ·g-1. 在此基础上, 采用瑞士安全技术与保障研究所提出的快速鉴别法（瑞士方法）及数值模拟技术, 对其分解反应的特性参数进行了推算, 结果表明其分解具有自催化性. 采用Malek法分析了该物质分解反应的最概然机理函数并得出了相关动力学参数, 表明其分解具有自催化性且符合Sestak-Berggren双参数自催化模型（SB模型）, 这与瑞士方法所得结论一致. 采用等温DSC测试获得了该物质的‘钟形’热解曲线, 从而验证了两种方法的结论.

Method to Determine the Kinetic Parameters of the Autocatalytic Decomposition Reaction and Critical Rate of Temperature Rise of Thermal Explosion of Energetic Materials from DSC Curves

Method to Determine the Kinetic Parameters of the Autocatalytic Decomposition Reaction and Critical Rate of Temperature Rise of Thermal Explosion of Energetic Materials from DSC Curves

Synthesis of nanosize and sintered Mn0.3Ni0.3Zn0.4Fe2O4 ferrite and their structural and dielectric studies

Mn0.3Ni0.3Zn0.4Fe2O4 ferrite nanoparticles were synthesized by thermally initiated autocatalytic decomposition of metal fumarato-hydrazinate complex. The chemical phase analysis has been carried out by X-ray powder diffraction method. The formation of complete ferrite phase occurred when the sample was annealed at 1100°C. The physical properties such as lattice parameter, bulk density and porosity were studied. The infra red spectra displayed two bands characteristics of spinel ferrite due to M–O stretching vibrations in tetrahedral and octahedral sites. The X-ray photoelectron and Mössbauer spectroscopy were used to study the valence and distribution of cations in tetrahedral (A) and octahedral [B] sites of the spinel. The frequency dependence of the dielectric properties such as dielectric constant, ε′, complex dielectric constant, ε″ and dielectric loss factor, tan δ, were studied at variable temperatures and reported in this paper.

Nano-crystalline Mn0.3Ni0.3Zn0.4Fe2O4 obtained by novel fumarato-hydrazinate precursor method

Carboxylate hydrazinate complex involving mixed metals have been synthesized and used as precursor for preparing the nanocrystalline Mn–Ni–Zn ferrite. Chemical composition of complex was fixed from chemical analysis results, infrared studies, thermogravimetric and differential scanning calorimetric analysis and isothermal weight loss studies. Nano-crystalline Mn–Ni–Zn ferrite particles obtained by thermal autocatalytic decomposition were characterized using X-ray diffraction studies, infrared spectral studies and TEM measurement. Two peaks in the region of 340–420 and 550–660 cm−1 observed in the infrared spectrum of “as synthesized” oxide are characteristics of spinel ferrites. Average particle size of “as synthesized” Mn–Ni–Zn ferrite was found to be 10 nm. “As synthesized” Mn–Ni–Zn ferrite showed Curie point at 313 °C. Saturation magnetization (44.7 emu/g) observed for “as synthesized” Mn–Ni–Zn ferrite is lower than bulk material which is indicative of its nano-crystalline nature. Seebeck coefficient measurement has shown that the material exhibits n-type semiconducting behavior.

光塩基発生反応と塩基増殖反応を用いた高感度光反応性材料の開発

Only a few articles have mentioned photoreactive materials relying on base-catalyzed transformations have been reported. This is probably due to relatively low quantum yields for photobase generation and weaker basicity of photogenerated bases, leading to low photosensitivity of photoreactive materials sensitized with photobase generators (PBGs). We report here novel PBGs to release organic strong bases with high quantum yields and a novel concept of base proliferation to improve the photosensitivity of the photoreactive materials. The concept involves the base-catalyzed decomposition of an organic compound termed a base amplifier (BA) which produces a newborn base molecule, leading to its autocatalytic decomposition. The addition of BAs to the photoreactive materials resulted in the marked improvement of photosensitivity because the number of photogenerated base molecules increases markedly as a result of the base proliferation reaction of the doped BA.

Dynamic Monte Carlo simulation of the [formula omitted] reaction on Pt(100): TPR spectra

The catalytic reduction of nitric oxide by hydrogen over a Pt surface is studied using a dynamic Monte Carlo (MC) method on a square lattice under low pressure conditions. Using a Langmuir–Hinshelwood reaction mechanism, a simplified model with only four adsorbed species (NO, H, O, and N) is constructed. The effect on the NO dissociation rate, the limiting step in the whole reaction, is inhibited by co-adsorbed NO and H2 molecules and is enhanced both by the presence of empty sites and adsorbed N atoms at nearest neighbors. In these simulations, several experimental parameter values are included, such as: adsorption, desorption and diffusion of the reactants. The phenomenon is studied while varying the temperature over the 300–550 K range. The model reproduces well-observed TPD and TPR experimental results. For the whole NO+H2 reaction, the phenomena of “surface explosion” is observed and can be explained as the result of the abrupt production of N2 due to both the autocatalytic NO decomposition favored by the presence of vacant sites and the development of inhomogeneous fluctuations. MA simulations also allow a visualization of the spatial development of the surface explosion as heating proceeds.

Surface structural evolution during the thermal decomposition of a PdO(101) thin film

We used scanning tunneling microscopy (STM) to characterize PdO(101) thin films grown on Pd(111), and the structural changes that occur during isothermal decomposition. We find that the PdO(101) thin films have high-quality surface structures that are characterized by large, crystalline terraces with low concentrations of point defects. Small domains of single-layer oxide are also present on the top layer of relatively thick PdO(101) films grown at 500 K. The thinner PdO(101) films exhibit negligible quantities of such domains, apparently because new domains agglomerate rapidly as the film thickness decreases. We find that the isothermal decomposition rate of a PdO(101) film at 720 K exhibits an autocatalytic regime in which the rate of oxygen desorption increases as the oxide decomposes. Our STM results demonstrate that reduced sites created during oxide decomposition catalyze further PdO decomposition, and reveal strong kinetic anisotropies in the decomposition. The kinetic anisotropies produce one-dimensional reaction fronts that propagate preferentially along the atomic rows of the PdO(101) surface, resulting in the formation of long chains of reduced sites. We also find that reduced sites promote oxygen recombination in neighboring rows of the Pd(101) structure, causing loops and larger aggregates of reduced sites to form. The promotion of decomposition across the atomic rows can qualitatively explain the autocatalytic desorption kinetics. Finally, the STM images provide evidence that underlying PdO(101) layers transfer oxygen to reduced surface domains, thus producing large domains of PdO(101) islands that coexist with reduced domains as well as the larger PdO(101) terraces of the initial surface. Re-oxidation of the surface acts to sustain the autocatalytic decomposition kinetics, and provides a mechanism for oxygen atoms to ultimately evolve from the subsurface of the PdO(101) film.

Kinetic analysis of thermal decomposition in liquid and solid state of 3-nitro and 4-nitro-benzaldehyde-2,4-dinitrophenylhydrazones

A kinetic study on the thermal decomposition of 3-nitro and 4-nitro-benzaldehyde-2,4-dinitrophenylhydrazones was carried out. The isothermal and dynamic differential scanning calorimetric curves were recorded for solids and melts, respectively. The standard isoconversional analysis of the obtained curves from both isothermal and nonisothermal analysis suggests an autocatalytic decomposition mechanism. This mechanism is also supported by the temperature dependence of the observed induction periods. Based on the results of the model-free method from nonisothermal regime, the kinetic model was derived and the kinetic parameters were obtained by means of a multivariate nonlinear regression.

Synthesis and characterization of Ni0.6Zn0.4Fe2O4 nano-particles obtained by auto catalytic thermal decomposition of carboxylato-hydrazinate complex

Ni0.6Zn0.4Fe2O4 nano-particles have been synthesized by self-propagating auto-combustion of nickel zinc ferrous fumarato-hydrazinate complex. The precursor complex has been characterized by chemical analysis, IR, AAS, thermal analysis and isothermal mass loss studies. The precursor on ignition undergoes self-propagating auto combustion to give Ni0.6Zn0.4Fe2O4. The X-ray diffraction studies confirmed the single phase formation of nano-size ‘as synthesized’ Ni0.6Zn0.4Fe2O4. TEM observation showed the average particle size to be 20 nm. Infrared and magnetization studies were also carried out on the ‘as synthesized’ Ni0.6Zn0.4Fe2O4. The lower value of saturation magnetization and higher Curie temperature of ‘as synthesized’ ferrite also hint at the nano size nature.

Synthesis and characterization of Co0.8Zn0.2Fe2O4 nanoparticles

Cobalt zinc ferrite, Co0.8Zn0.2Fe2O4, nanoparticles have been synthesized via autocatalytic decomposition of the precursor, cobalt zinc ferrous fumarato hydrazinate. The X-ray powder diffraction of the ‘as prepared’ oxide confirms the formation of single phase nanocrystalline cobalt zinc ferrite nanoparticles. The thermal decomposition of the precursor has been studied by isothermal, thermogravimetric and differential thermal analysis. The precursor has also been characterized by FTIR, and chemical analysis and its chemical composition has been determined as Co0.8Zn0.2Fe2(C4H2O4)3·6N2H4. The Curie temperature of the ‘as-prepared oxide’ was determined by AC susceptibility measurements.

Synthesis, characterization, infrared studies, and thermal analysis of Mn0.6Zn0.4Fe2(C4H2O4)3·6N2H4 and its decomposition product Mn0.6Zn0.4Fe2O4

Manganese zinc ferrous fumarato–hydrazinate precursor, Mn0.6Zn0.4Fe2(C4H2O4)3·6N2H4 was synthesized for the first time and characterized by chemical analysis, infrared spectral studies, and thermal analysis. Infrared studies show band at 977 cm−1 indicating bidentate bridging nature of the hydrazine in the complex. Thermogravimetric (TG) studies show two steps dehydrazination followed by two steps total decarboxylation. The precursor on touching with burning splinter undergoes self propagating autocatalytic decomposition yielding ultrafine Mn0.6Zn0.4Fe2O4. XRD studies confirms single phase formation as well as nanosize nature of “as prepared” Mn0.6Zn0.4Fe2O4. The saturation magnetization of the “as prepared” Mn0.6Zn0.4Fe2O4 was found to be 31.46 emu gm−1, which is lower than the reported, confirms the ultrafine nature of the oxide.

Central Role of Phenanthroline Mono-N-oxide in the Decomposition Reactions of Tris(1,10-phenanthroline)iron(II) and -iron(III) Complexes

1,10-Phenanthroline mono-N-oxide (phenO) is a product of the decomposition of tris(1,10-phenanthroline)iron(III), Fe(phen)(3)(3+), and has a slight autocatalytic effect on the overall reaction. The mechanism is proposed to involve Fe(phen)(3)(4+) as a minor intermediate. The addition of phenO significantly influences the kinetic features of the decomposition of Fe(phen)(3)(3+) and the oxidation of Fe(phen)(3)(2+) by HSO(5)(-). The autocatalytic decomposition explains the difficulties in the preparation of Fe(phen)(3)(3+) and may contribute to exotic kinetic phenomena studied using Fe(phen)(3)(3+)/Fe(phen)(3)(3+) as a supposedly innocent indicator.

COMU: A third generation of uronium‐type coupling reagents

COMU is a third generation of uronium-type coupling reagent based on ethyl 2-cyano-2-(hydroxyimino)acetate (Oxyma) as well as a morpholino carbon skeleton. The presence of the morpholino group has a marked influence on the solubility, stability and reactivity of the reagent. COMU performed extremely well in the presence of only 1 equiv. of base, thereby confirming the effect of the hydrogen bond acceptor in the reaction. The by-products of COMU are water soluble and easily removed, making it an excellent choice of coupling reagent for solution-phase peptide synthesis. Finally, COMU shows a less hazardous safety profile than benzotriazole-based reagents, such as HATU and HBTU, which in addition exhibit unpredictable autocatalytic decompositions and therefore a higher risk of explosion. Furthermore, in contrast to benzotriazole-based reagents, COMU is significantly less likely to cause allergic reaction.

The mechanism of solid-state decompositions in a retrospective

This is an overview of the early investigations into the mechanism of solid decompositions since the fundamental studies by Ostwald on catalysis during 1890–1902 and the first experimental study of the autocatalytic decomposition of Ag2O by Lewis in 1905. In order to explain the formation mechanism of the solid product, Volmer suggested in 1929 that the decomposition of Ag2O includes two sequential stages: first, a thermal decomposition of the oxide into gaseous silver atoms and oxygen molecules and second, the condensation of the supersaturated silver vapor. This revolutionary idea was immediately used by Schwab to explain the autocatalytic peculiarity of solid-state decomposition reactions. However, this mechanism did not receive the acceptance of the scientific community. On the contrary, as can be seen from the results presented at the conference “Chemical reactions involving solids” in Bristol in 1938, this model was dismissed as unrealistic and, as a result, was since forgotten. Instead, considerable attention at this conference was devoted to the disorder theory proposed earlier by Wagner and Schottky, and to the mechanism of ion transport in the solid crystals. During the subsequent 70 years, decomposition mechanisms have been interpreted, without visible progress, on the latter basis. The mechanism of congruent dissociative vaporization proposed independently in 1990 turned out to be in complete agreement with the Volmer–Schwab model. It has been treated with the same distrust. These historical events, in the author’s opinion, are responsible for the prolonged stagnation in the development of solid-state decomposition theory.