Hydroperoxidation of Tertiary Alkylaromatics Catalyzed By N‐Hydroxyphthalimide and Aldehydes under Mild Conditions

A metal‐free catalytic system consisting of an aldehyde and N‐hydroxyphthalimide (NHPI) for the selective oxidation of tertiary alkylaromatics with molecular oxygen has been developed. Cumene was oxidized efficiently to the corresponding hydroperoxide under mild conditions. The molecule‐induced homolysis between peracids generated in situ and NHPI ensured the formation of the phthalimide N‐oxyl (PINO) radical even at room temperature. Investigations on aldehyde, solvent and temperature effects allowed us to achieve good conversions with high selectivity in hydroperoxide. The optimized procedure was successfully extended to phenylcyclohexane, a valuable alternative for the production of phenol. The mechanism is discussed in detail.     

A Thermal Decomposition Model of Aminoguanidium 5,5′‐Azobis‐1H‐Tetrazolate and the Effect of Pressure and Particle Size on the Rate of Decomposition

The temperature histories of aminoguanidinium 5,5′‐azobis‐1H‐tetrazolate (C₄H₁₄N₁₈, AGAT) were measured in order to construct a thermal decomposition model of the compound. The effects of chamber pressure and AGAT particle size were also examined. The results of the study suggest that the thermal decomposition of AGAT occurs in three phases: solid phase, condensed phase, and residue. It was found that the condensed phase consists of decomposition zone I where dramatic temperature rise occurs, decomposition zone II where gradual temperature rise occurs, and the cooling zone where decomposition and temperature stop rising. It was also suggested that the temperature of the decomposition surface which is the interface of the solid phase and the condensed phase was ∼500 K, and that N₂ and NH₃ were suggested to occur in the vicinity of the decomposition surface of decomposition zone I. In addition, it was suggested that the thickness of the decomposition zones I and II decreases and that the maximum‐temperature‐reached increases with an increase in atmospheric pressure. The rate of decomposition of AGAT was found to follow Vieille's equation and the rate of decomposition increases with an increase in pressure. The rate of decomposition increased slightly with an increase in particle size.     

An Investigation on Thermal Decomposition of DNTF‐CMDB Propellants

The thermal decomposition of DNTF‐CMDB propellants was investigated by pressure differential scanning calorimetry (PDSC) and thermogravimetry (TG). The results show that there is only one decomposition peak on DSC curves, because the decomposition peak of DNTF cannot be separated from that of the NC/NG binder. The decomposition of DNTF can be obviously accelerated by the decomposition products of the NC/NG binder. The kinetic parameters of thermal decompositions for four DNTF‐CMDB propellants at 6 MPa were obtained by the Kissinger method. It is found that the reaction rate decreases with increasing content of DNTF.     

New High‐Nitrogen Materials Based on Nitroguanyl‐Tetrazines: Explosive Properties,Thermal Decomposition and Combustion Studies

This paper describes the explosive sensitivity and performance properties of two novel high‐nitrogen materials, 3,6‐bis‐nitroguanyl‐1,2,4,5‐tetrazine ( 1 , (NQ₂Tz)) and its corresponding bis‐triaminoguanidinium salt ( 2 , (TAG)₂(NQ)₂Tz)). These materials exhibit very low pressure dependence in burning rate. Flash pyrolysis/FTIR spectroscopy was performed, and insight into this interesting burning behavior was obtained. Our studies indicate that 1 and 2 exhibit highly promising energetic materials properties.     

Non‐Isothermal Kinetic Study of the Thermal Decomposition of Melamine 3‐Nitro‐1,2,4‐triazol‐5‐one Salt

Study on thermal behavior of 3‐nitro‐1,2,4‐triazol‐5‐one (NTO) salts was required to obtain important data for application purposes. These compounds have been shown to be useful intermediates for gun propellant ingredients, high energetic ballistic modifiers for solid propellants and other potential applications. In this paper, thermal decomposition and non‐isothermal kinetics of melamine 3‐nitro‐1,2,4‐triazol‐5‐one salt (MNTO) were studied under non‐isothermal conditions by DSC and TG methods. The kinetic parameters were obtained from analysis of the DSC and TG curves by Kissinger and Ozawa methods. The critical temperature of thermal explosion (T_b) was 574 K. The results show that MNTO is thermally more stable than NTO when compared in terms of the critical temperature of thermal explosion. Finally, the values of ΔS^#, ΔH^#, and ΔG^# of its decomposition reaction were calculated.     

Decomposition of Epoxy Model Compounds in Near‐Critical Water

Two tpyes of epoxy resin model compounds, one containing an ether bond and bisphenol‐A structure (compound I) and the other comprising ether and tertiary amine bonds (compound II), were prepared and then decomposed in near‐critical water (NCW). In the case of model compound I, at low temperatures the water molecules behave as nucleophilic reagent reacting with the terminal ether group of the model compound. When the temperature is increased, the middle ether bond of the model compound molecule can be broken down. As to model compound II, at lower temperatures, cleavage of the ether bond happens more easily than that of the tertiary amine bond because of higher positive charge density centered at the carbon atom in the ether group. At higher temperatures, the energy required to break down the ether bond is reduced dramatically after being protonated by H⁺, and therefore, the bond can be cleaved more readily than the tertiary amine bond. The decomposition products in both model compounds were found unstable and could react with each other to generate other compounds. Decomposition mechanisms were also proposed based on the decomposition products for the model compounds.     

Preparation and Characterization of JP‐10 Gel Propellants with Tris‐Urea Low‐Molecular Mass Gelators

The preparation and characterization of high‐energy density hydrocarbon fuel JP‐10 supramolecular gel propellants are reported. The low‐molecular mass gelator 1,1′,1′′‐((2,4,6‐trioxo‐1,3,5‐triazinane‐1,3,5‐triyl)tris(hexane‐6,1‐diyl))tris(3‐octadecylurea) (HDIT‐18) shows powerful gelation ability for JP‐10, the critical gelator concentration for JP‐10 is as low as 0.0638 wt‐%. The JP‐10 supramolecular gel propellants exhibit high thermal stability. Scanning electron microscopy (SEM) studies reveal that the gelator molecules self‐assemble into 1–3 μm fibers in JP‐10. Rheological studies show the JP‐10 supramolecular gels are thixotropic and shear‐thinning (for a shear rate range from 0.3 to 30 s⁻¹), the dynamic strain sweep test shows that the critical strain percentage of the gel materials is 1 %. The studies reported herein provide a potential fuel material for gel propellants.     

Thermal Decomposition of Energetic Materials 84: Pyrolysis of 5‐Substituted 1,3,5‐Trinitrohexahydropyrimidines

Results of slow and fast pyrolysis were compared for 1,3,5‐trinitrohexahydropyrimidine compounds in which the 5‐position was substituted by H, CH₃, NO₂, CH₂ONO₂, and CH₂N₃. IR and Raman spectroscopy were used to identify and quantify all of the gaseous products. The decomposition process appears to be initiated by reactions at the 5‐position of the ring. The gases produced are rather similar for all of the compounds, however the different functional groups impart their own signature on the concentrations of several products.     

Decomposition and Ignition of the High‐Nitrogen Compound Triaminoguanidinium Azotetrazolate (TAGzT)

The high‐nitrogen compound triaminoguanidinium azotetrazolate (TAGzT) belongs to a class of C, H and N compounds that are free of both oxygen and metal, but retain energetic material properties as a result of their high heat of formation. Its decomposition thus lacks secondary oxidation reactions of carbon and hydrogen. The fact that TAGzT is over 80% nitrogen makes it potentially useful as a gas generant and energetic material with a low flame temperature to increase the impulse in gun or rocket propellants. The burning rate, laser ignition and flash pyrolysis (T‐jump/FTIR spectroscopy) characteristics were determined. It was found that TAGzT exhibits one of the fastest low‐pressure burning rates yet measured for an organic compound. Both the decomposition and ignition behavior of TAGzT are dominated by condensed phase reactions. T‐Jump/FTIR spectroscopy indicates that condensed phase reactions release about 65% of the energy, which helps to explain the high burning rate at low pressure.     

Performance Assessment of Some Isomers of Saturated Polycyclic Hydrocarbons for Use as Jet Fuels

The performance of jet fuel depends on the density (ρ), condensed phase heat of formation (▵_fH°(c)), and specific impulse (I_SP). Exo‐tricyclo[5.2.1.0(2,6)]decane (C₁₀H₁₆) or JP‐10 is now used as a suitable synthetic liquid jet fuel because it has the approximated values of ρ=1.1 g cm⁻³ and ▵_fH°(c)=− 123 kJ mol⁻¹ and a broad range between the melting and boiling points, i.e. T_bp–T_mp=196.2 K. This work introduces a suitable pathway for calculation of the values of ρ, ▵_fH°(c), and I_SP of 13 well‐known isomers of JP‐10 and a series of saturated polycyclic hydrocarbons with general formula of C_nH_n′ (5≤n≤12) in order to specify high performance jet fuels. Although 13 compounds have larger values of I_SP*ρ than JP‐10, only two compounds, tetraspiro[2.0.0.0.2.1.1.1]undecane and tetracyclo[3.2.0.0(2,7).0(4,6)]heptane, are suitable as jet fuels.     

1‐Amino‐1‐hydrazo‐2,2‐dinitroethene – a Hazard Warning

1‐Amino‐1‐hydrazo‐2,2‐dinitroethene ( 2 ) has been observed to spontaneously decompose with considerable violence during storage. Its preparation and handling should be regarded as potentially hazardous.     

Thermal Decomposition of Organic Peroxides TATP and HMTD by T‐Jump/FTIR Spectroscopy

The thermal decomposition of the peroxides, triacetone triperoxide (TATP) and hexamethylene triperoxide diamine (HMTD) was investigated as a function of pressure, temperature and atmosphere by T‐jump/FT‐IR spectroscopy. In an Ar atmosphere at fast heating rates, the dominant decomposition product of TATP was methane rather than acetone which dominates at slow heating rates. The products of TATP were different in Ar and in air which implies that decomposition occurs primarily in the gas phase. In contrast, the products from HMTD were independent of the surrounding atmosphere implying that it decomposes primarily in the condensed phase. The IR spectra of the decomposition products of HMTD exhibited some dependence on pressure but not on the pyrolysis filament temperature.     

Effect of Nano‐Copper Oxide and Copper Chromite on the Thermal Decomposition of Ammonium Perchlorate

The catalytic effect on the thermal decomposition behavior of ammonium perchlorate (AP) of p‐type nano‐CuO and CuCr₂O₄ synthesized by an electrochemical method has been investigated using differential scanning calorimetry as a function of catalyst concentration. The nano‐copper chromite (CuCr₂O₄) showed best catalytic effects as compared to nano‐cupric oxide (CuO) in lowering the high temperature decomposition by 118 °C at 2 wt.‐%. High heat releases of 5.430 and 3.921 kJ g⁻¹ were observed in the presence of nano‐CuO and CuCr₂O₄, respectively. The kinetic parameters were evaluated using the Kissinger method. The decrease in the activation energy and the increase in the rate constant for both the oxides confirmed the enhancement in catalytic activity of AP. A mechanism based on an electron transfer process has also been proposed for AP in the presence of nano‐metal oxides.     

Thermal Decomposition of Energetic Materials 86. Cryogel Synthesis of Nanocrystalline CL‐20 Coated with Cured Nitrocellulose

An unusual energetic composite, in which spherical nano‐dimensional particles of CL‐20 were uniformly coated with HDI‐cross‐linked nitrocellulose, was synthesized by the sol‐gel to cryogel method. Up to 90% solid loading was achieved. The particle size of CL‐20 was determined to be in the range of 20–200 nm by transmission electron microscopy, atomic force microscopy, and X‐ray powder diffraction. The decomposition characteristics of the composite were investigated by DSC and T‐jump/FTIR spectroscopy. The decomposition properties were controlled mostly by nitrocellulose until the percentage of CL‐20 was well above 50%. The drop weight impact sensitivity of the cryogels was essentially independent of the composition.     

A First Principles Density Functional Study of Crystalline FOX‐7 Chemical Decomposition Process under External Pressure

We report on a first principles analysis of chemical decomposition reaction in a crystalline FOX‐7 (1,1‐diamino‐2,2‐dinitroethylene) molecule, which is a good candidate for insensitive energetic materials. Our calculations are based on variable‐cell shape methods under pressure, density functional theory with localized numerical orbital and pseudopotential, together with ab initio biasing molecular dynamics. The calculated crystal structure and equation of state (pressure vs. volume) up to 8 GPa agrees well with the corresponding experimental data. A chemical decomposition by intermolecular hydrogen transfer is found at higher pressure. This decomposition appears to be driven by a weakening in the chemical hardness. This suggests that the molecular HOMO and LUMO orbital energy difference is decreased when intermolecular hydrogen transfers occur, and for the FOX‐7 crystal the band gap is narrowed with increasing external pressure.     

Synthesis,Characterization and Thermal Behaviour of Guanidinium‐5‐aminotetrazolate (GA) – A New Nitrogen‐Rich Compound

This work describes the synthesis and the thermoanalytical characterization of guanidinium‐5‐aminotetrazolate (GA). GA is a new nitrogen‐rich energetic material. It is not mentioned in the chemical literature so far. The molecular structure of the compound has been determined by IR, ¹H‐, ¹³C‐ and ¹⁵N‐NMR spectroscopy. The thermal properties, the decomposition pathways and its volatile products were investigated by thermal analysis and are discussed.     

Extraction with Spinodal Decomposition – Experiment and Simulation

Experimental results on the growth and velocity of droplets (up to 0.45 mm/s) during the temperature‐induced phase separation of the 3‐methoxypropionitrile/water solvent system as well as a variety of theoretical methods used to study the demixing dynamics are presented. Due to computational costs, the simulation with Molecular Dynamics (MD) is feasible only for very short times (ps) and miniscule boxes (Å). Dissipative Particle Dynamics (DPD), where a coarse‐grained model of the system is employed, allows nanosecond simulations in a box with more than 13 million atoms in a diffusion‐dominated regime. Finally, the influence of the diffusion/convection ratio during the separation in the μs scale is studied by use of a code based on Model H for both instantaneous and non‐instantaneous quenching cases. Structural information and macroscopic parameters, such as interfacial tension, can be derived from the molecular simulations.     

Decomposition of phenols in aqueous solution by a UV/O3 process

The decomposition of several non‐biodegradable phenols by the UV/O₃ and ozonation processes was studied and compared under various solution pH values, O₃ input mass flow rates and UV intensities to investigate the removal efficiencies of reactants and organic intermediates. The decomposition rate of phenols by the UV/O₃ process was found to increase with increasing O₃ input dosage, light intensity and solution pH value. The mineralization efficiencies of phenols in aqueous solution would be above 98% under adequate reaction conditions within three hours, but would be retarded for alkaline solutions because of the dissolution of CO₂ formed by mineralization of phenols. The increment of ozone input dosage had little effect on the mineralization of organic intermediates at the latter course of the reaction. The order of the decomposition rate of the phenols used in this research was 2,4‐dichlorophenol > 2‐chlorophenol > 2‐nitrophenol for low and neutral pH solutions, whereas they were nearly alike for alkaline solutions. The two‐step consecutive kinetic model was found to fit well in modeling the behavior of species during the decomposition of phenols in aqueous solutions by the UV/O₃ process.     

Analysis of Liquid Jet Breakup in One‐ and Two‐Phase Flows

The phenomenon of breakup of a jet into drops has been applied mainly to separation technologies in the chemical, pharmaceutical, and metallurgical industries. The paper deals with the experimental analysis directed at the breakup of polymer solutions flowing through an orifice nozzle. The analysis of the breakup and atomization of a liquid jet by a high‐speed gas jet is presented. Additionally, non‐Newtonian effects on the breakup of the liquid jet into drops were studied using the microphotography method. In the experiments, various aqueous solutions of polyacrylamide were used. The polymer solutions studied were power‐law fluids. Analysis of the photographs of the jet breakup showed that the length of the jets depends on the liquid and gas flow rates and on the concentration of the polymer used. High‐molecular‐weight polymers added to a solvent lead to changes in the rheological properties of the liquid and the breakup length of the jet.