Non-isothermal Decomposition Kinetics Research Articles

Thermodynamic Analysis and Pyrolysis Mechanism of 4,4'-Azobis-1,2,4-triazole.

The nonisothermal thermal decomposition kinetics of 4,4'-azobis-1,2,4-triazole (ATRZ) at different heating rates (5, 10, 15, and 20 °C·min-1) were investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC) studies. The thermal decomposition kinetic parameters such as apparent activation energy (E) and pre-exponential factor (A) were calculated by the Kissinger, Ozawa, and Šatava-Šestak methods. The E and A values calculated by the above three methods are very close, which are 391.1 kJ·mol-1/1034.92 s-1, 381.1 kJ·mol-1/1034.30 s-1, and 393.4 kJ·mol-1/1035.76 s-1, respectively. Then, the decomposition mechanism function of ATRZ is analyzed by the calculated results. The results show that the decomposition temperature of ATRZ is about 300 °C and the exothermic decomposition speed is fast. The decomposition pathway of ATRZ was analyzed by pyrolysis-gas chromatography-mass spectrometry (PY-GC-MS). The thermal decomposition kinetic equation of the ATRZ was deduced.

Pyrolysis behavior, properties and mechanism of high-energy oxidizer 2,3-bis(hydroxymethyl)-2,3-dinitro-1,4-butanediol tetranitrate

To evaluate the thermal properties and promote the application of 2,3-bis(hydroxymethyl)-2,3-dinitro-1,4-butanediol tetranitrate (BHDBT), thermal behavior of BHDBT was studied systematically using differential scanning calorimetry (DSC), thermogravimetric analysis (TG/DTG) and thermogravimetric-infrared-mass spectrometry (TG-IR-MS) techniques. The results show that the thermal behavior of BHDBT presents two stages, one is an obvious endothermic melting process, the other is a big exothermic decomposition process with mass loss of about 81 %, and the peak temperatures (Tp) of two processes are 86.5 °C and 186.9 °C at the heating rate of 10 °C min−1, respectively. In high-pressure sealed crucible, BHDBT presents similar thermal behavior to that in common open crucible. Non-isothermal decomposition kinetics equation of BHDBT was obtained, and the possible thermal decomposition mechanism for BHDBT was proposed based on the main gas-phase products, including H2O, HCN, CO, CO2, NO, N2O and NO2, which are proved by TG-IR-MS testing results. Finally, the combustion heat and standard molar enthalpy of formation of BHDBT were measured and calculated. All results will provide a theoretical support for the application of BHDBT.

Thermal studies of novel heat-resistant 3,6-dinitropyrazolo[4,3-c]pyrazole-based energetic materials

1,4-Bis(2′,4′,6′-trinitrophenyl)−3,6-dinitro[4,3-c]pyrazole (DTNBDNP) is a newly developed heat-resistant explosive exhibiting superior properties to most traditional heat-resistant energetic materials with a significantly high thermal decomposition temperature of 410 °C. Detailed thermal behaviors and nonisothermal decomposition kinetics of DTNBDNP and 1,4-bis(2′,4′-dinitrophenyl)−3,6-dinitro[4,3-c]pyrazole (DDNBDNP) were investigated using a differential scanning calorimeter (DSC), and the thermal safety was evaluated by different criteria, including the self-accelerating decomposition temperature and critical temperature of thermal explosion. Their thermodynamic functions were also obtained based on the specific heat capacity data determined using a micro-DSC method. Further studies on the thermal decomposition mechanism were carried out through condensed-phase thermolysis/Fourier transform infrared (in situ FTIR) spectroscopy and the combination of differential scanning calorimetry–thermogravimetry–mass spectrometry–Fourier transform infrared spectroscopy (DSC–TG–MS–FTIR) techniques. The experimental results prove that the decomposition of DTNBDNP and DDNBDNP is most likely to begin with a ring-opening reaction of the fused-heterocycle backbone. In addition, the main gaseous products, including NO, CO2, N2O, and NO2, are released from the decomposition of DTNBDNP and DDNBDNP.

Hydrogen bond networks enhance the safety of energetic salts azobistetrazole-1,1′-dioxy dimethylbiguanide

Weak interaction is an important force widely existing in material molecules, which may affect the structure and even properties of materials, mainly including π stacking, hydrogen bond network and van der Waals force, etc. The π-stacking and hydrogen bonding networks in energetic materials have a particularly significant impact on their safety. 1,1′-dihydroxy-azobistetrazole (H2AzTO) with abundant hydrogen bond acceptor and dimethyl biguanide (DMG) with abundant hydrogen bond donor was selected as starting materials, then a new energetic salt with strong hydrogen bond network structure, azobistetrazole-1,1′-dioxy-dimethyl biguanide (DMGAzTO), was synthesized through an acid-base neutralization reaction. The structure of DMGAzTO was characterized by FT-IR, 1H NMR, 13C NMR, EA, and SC-XRD, and the thermal stability and non-isothermal thermal decomposition reaction kinetics of DMGAzTO were studied by DSC and TGA methods. The HOF, detonation velocity, and pressure (D, P) were calculated by Born-Haber cycle and K-J empirical formula. The friction and impact sensitivity (FS and IS) of the compound were examined using a BAM sensitivity tester. Results show that the DMGAzTO salt belongs to the 1:1 type with a molecule of bound water; the peak temperature of thermal decomposition is 502 K; the thermal weight loss rate is 82%; the theoretically calculated D and P are 8217 m s−1 and 27.1 GPa, and the FS and IS are 30 J and 360 N, respectively.

Pyrolysis Kinetics and Combustion Behaviors of a High-Nitrogen Compound, 4,4'-Azobis(1,2,4-triazole).

To study the thermal decomposition behavior of 4,4′-azobis(1,2,4-triazole) (ATRZ), the non-isothermal thermal decomposition kinetics of ATRZ were studied using the thermogravimetric–differential scanning calorimetry (TG–DSC) method. The TG–DSC of ATRZ was analyzed at heating rates of 5, 10, 15, and 20 K·min−1 in an argon atmosphere. The thermal decomposition kinetic parameters at peak temperature (Tp), such as apparent activation energy (Ea) and pre-exponential factor (lgA) of ATRZ, were calculated using the Kissinger, Ozawa, and Satava–Sestak methods. Ea and lgA calculated using the Kissinger, Ozawa, and Satava–Sestak methods are very close, at 780.2 kJ·mol−1/70.5 s−1, 751.1 kJ·mol−1/71.8 s−1, and 762.1 kJ·mol−1/71.8 s−1, respectively. Using a combination of three methods, the reaction mechanism function g(α) of ATRZ was obtained. The results show that the decomposition temperature of ATRZ is about 310 °C, and the decomposition is rapidly exothermic. The pyrolysis path of ATRZ was investigated through a pyrolysis-gas chromatography mass spectrometry (PY-GC/MS) experiment. ATRZ has three different decomposition paths and finally generates N2, HC-N-CH, N≡C-N, and HC=N-C≡N. The laser ignition combustion duration of ATRZ was 0.5033 s and the peak temperature was 1913 °C. The laser ignition combustion duration of ATRZ+CL-20 was 1.0277 s and the peak temperature was 2105 °C. The rapid energy release rate of ATRZ promotes the combustion energy release of CL-20.

Synthesis, characterization, thermal behavior, and antitumor activities of an Ag(I) complex based on 4-(2-hydroxyphenyl)-2-methylpyrimidine

A new Ag(I) coordination complex, Ag(C11H10N2O)2·NO3 (C11H10N2O = 4-(2-hydroxyphenyl)-2-methylpyrimidine) is successfully synthesized and characterized by infrared spectroscopy, elemental analysis, and single-crystal X-ray diffraction analysis. This complex features a three-dimensional framework consisting of hydrogen bonds, π–π stacking interactions, coordination interactions, and electrostatic interactions. Moreover, the thermal stability and non-isothermal thermal decomposition reaction kinetics of the complex are well investigated by the methods of Kissinger and Ozawa. Finally, the antitumor ability of the complex is evaluated against human lung cancer cells (NCI-H460), human hepatocellular cancer cells (HepG2), and human breast cancer cells (MCF7). The complex exhibits potent antitumor activities against HepG2 and MCF7 cancer cells.

Tunable catalytic activity of energetic multi-metal hexanitro complexes for RDX decomposition and ignition

Development of the high energy and low signature propellants with controllable heat releases is always desirable but challenging. Herein, four versatile energetic materials, multi-metal hexanitro complexes (K3[Co(NO2)6], K2Pb[M(NO2)6] (M = Cu2+, Ni2+, Co2+)) as potential catalysts and flash suppressors of the propellants, have been prepared and characterized, and their effects on the non-isothermal and adiabatic decomposition behaviors and kinetics, pyrolysis pathway, heat release, laser ignition and flame propagation properties of RDX have been studied. The results showed that the structure, composition, powder color, and morphology of the hexanitro complexes were transformed due to the substation of transition metal cations, resulting in their different thermal behaviors. The study of the non-isothermal decomposition kinetics showed that the decomposition peak temperature and activation energy (Ea) of RDX was decreased by the addition of hexanitro complexes, and addition of K2Pb[Co(NO2)6] to RDX has the lowest activation energy, while the replacing of the transition metal cations Cu2+ and Ni2+ for Co2+ cannot improve the catalytic activity. The influence of hexanitro complexes on the main pyrolysis pathway of RDX was studied by the TG-FTIR technique, and it is found that the decomposition products (NO and metal oxides) of hexanitro complexes resulted in the transformation of the pyrolysis mechanism of RDX. The adiabatic decomposition results showed that the RDX/K2Pb[Cu(NO2)6] had the largest self-heat rate and the lowest Ea, whereas the RDX/K2Pb[Co(NO2)6] have the shortest time to maximum rate under adiabatic condition. The addition of K2Pb[Cu(NO2)6] to RDX resulted in the largest total heat release, the fastest release rate, and the lowest ignition delay time. The results from the non-isothermal and adiabatic decomposition, heat release and ignition presented that the diverse metal cations in the hexanitro complexes led to the different catalytic performances, which indicated the tunable catalytic activities of hexanitro complex systems to RDX pyrolysis. The hexanitro complexes facilitated the mass and heat transfer in the flame propagation process, owing to the formation of enormous gaseous products and microparticles. Therefore, the tunable characterization of energetic hexanitro complexes demonstrated that these complexes have a large potential application for controlling the heat release of the solid propellants.

A Kinetic Evaluation for Phenothiazine Based Copolymers

In here, the nonisothermal decomposition kinetics of co-polymers based phenothiazine was present-ed. For this, firstly, 3, 7-di-2-thienyl-10H-phenothiazine (TF) was prepared via an optimized Suzu-ki–Miyaura cross-coupling reaction. After monomer (TF) characterization, the copolymerization re-actions with EDOT and thiophene were performed by the electrochemical technique. The molecular masses of the co-polymers were found by gel permeation chromatography (GPC) analysis. Thermal characterizations of the resulting polymers were conducted by thermogravimetric analyses. The thermal decomposition kinetics of the resulting polymers was also performed. For this, the kinetic methods (Tang, FWO, KAS, Kissinger, and Friedman) based on the multiple heating rates were used. Several kinetic parameters related to the decomposition kinetics of the solid-state were revealed.

Non-isothermal decomposition kinetics of lipids recovered from oleaginous microbial biomass (C. vulgaris and L. starkeyi): reaction mechanism and TGA-MS analysis

Oleaginous microorganisms and the thermal decomposition of their recovered lipids are new attractive research fields for the sustainable production of biofuels from actual biomass. In this work, the thermal decomposition of lipids from C. vulgaris and from L. starkeyi was investigated using a thermogravimetric analyzer coupled to a mass spectrometer (TGA-MS) under non-isothermal conditions. Thermal decomposition was examined using the one-step reaction model. Integral, differential, and advanced isoconversional methods were implemented to analyze the conversion-dependent activation energy. The Friedman method resulted in an accurate and reliable estimation of the kinetic parameters. The activation energy showed a strong dependence on conversion from 123.5 to 246 kJ mol-1 for lipids from C. vulgaris and from 80.3 to 299.9 kJ mol-1 for lipids from L. starkeyi. The generalized master plot approach evidenced that the thermal decomposition of lipids from C. vulgaris proceeds via three-dimensional diffusion (D3—Jander’s equation). Also, the kinetic analysis indicated that Valensi’s equation (D2), controlled by a two-dimensional diffusion model, is the most likely mechanism for the thermal decomposition of lipids from L. starkeyi. The rate parameters were evaluated via a kinetic compensation plot. Ion temperature evolution was investigated by TGA-MS revealing many of the functional groups evolved in the range of 350–500 °C as C1–C7 aliphatic hydrocarbons, aromatic hydrocarbons, aldehydes, carboxylic acids, and furan derivatives. All these aspects favor the lipid biosynthesis from microbial biomass to potential lipid-based building blocks.

New insensitive high-energy dense biopolymers from giant reed cellulosic fibers: their synthesis, characterization, and non-isothermal decomposition kinetics

Renewable giant reed has been explored for the first time to develop new advanced high-energy dense biopolymers through carbamate surface functionalization and nitration of native cellulose and cellulose microcrystals.

Biofuels production from rubber seeds

Worldwide biodiesel is being produced mainly from edible and non-edible vegetable oils. The choice of vegetable oils depends on primarily on availability, price, and the policy adopted by governing agencies. Currently, rubber seed getting attention for production of biofuels. In this study, the entire work was carried out in this research in into three major parts; (1) Parameter optimization during rubber seed oil (RSO) extraction: The effects of process parameters such as extraction time (3–12 h), kernel particle size range (0.5–3 mm), ratio of kernel to solvent (0.03–0.09 g/ml), and variety of solvents (polar and non-polar) on sox let extraction process were studied. Design of experiment (DOE) schemes was considered to prepare an experimental matrix using central composite design (CCD) approach. Response surface methodology (RSM) was applied to optimize the process parameters to achieve maximum oil yield. (2) Ultrasonic-assisted chemical modification of RSO for rubber oil methyl ester (ROME) production: Since RSO is high free fatty acid oil, a two-step procedure, esterification using homogeneous catalyst followed by transesterification with heterogeneous catalyst was followed for ROME synthesis. Further, the physico-chemical properties and rheological behavior of rubber seed oil (RSO) and its derivative methyl esters as well as their blends with diesel fuel were investigated. (3) Solid by-product utilization for biofuel synthesis: Solid wastes generated during biodiesel feedstock preparation process which comprise 40–48 wt. % rubber seed shell (RSS) and 25–30 wt% rubber seed cake (RSC) were utilized to produce liquid fuel and bio-char. Physico-chemical properties and thermo-gravimetric analysis (TGA) based non-isothermal decomposition (pyrolysis) kinetics of RSS and RSC were investigated. In depth analysis of physico-chemical-thermal properties of RSS and RSC obtained products (liquid and bio-char) using various analytical techniques suggested that both RSS and RSC can be considered as a suitable feedstock for the production of value added chemicals including fuel.

Energetic properties, thermal behavior and thermal safety of 4-(2,2,2-trinitroethyl)-2,6,8,10,12-pentanitro-2,4,6,8,10,12-hexaazaisowurtzitane

The physicochemical and energetic properties of 4-(2,2,2-trinitroethyl)-2,6,8,10,12-pentanitro-2,4,6,8,10,12-hexaazaisowurtzitane (1) are investigated. The energetic cage compound exhibits detonation properties comparable to those of HMX, and its impact sensitivity is higher than that of ε-CL-20. It shows a significantly higher thermal stability with a decomposition temperature of 227.6 °C than those of the other trinitromethyl-substituted energetic compounds. Its thermal behavior is further investigated using differential scanning calorimetry and accelerating rate calorimetry. The non-isothermal and adiabatic decomposition reaction kinetics of compound 1 are studied, and its thermal safety is evaluated using different criteria including the self-accelerating decomposition temperature, critical temperature of thermal explosion, and five-second delay exploding point.

Non-isothermal decomposition kinetics of nano-scale CaCO3 as a function of particle size variation

We report the synthesis of nanocrystalline calcium carbonate with varying particle sizes by precipitation techniques from an aqueous solution of calcium nitrate and sodium carbonate at controlled pH. The particle size of the carbonate powder was precisely controlled by changing the precursor concentration. The synthesized carbonate powders were characterized by using scanning electron microscopy, X-ray diffraction technique, and transmission electron microscopy. The particle size, along with the crystallite size of as-synthesized carbonate powder, decreases with increasing precursor concentration. The non-isothermal decomposition kinetics of the carbonate powder was also evaluated by using near to the modified Arrhenius equation's exact solution. The experimental results were best fitted at n = 0.5, and the one-dimensional diffusion-controlled transport process mechanism (D1) and one-dimensional phase boundary movement mechanism (R1) was found to be very close fit of the corresponding evaluated g(α) value. The apparent activation energy of the nano calcium carbonate decomposition was found in the range of 120–175 kJ/mol, which is also inherently functioning with the average particle size. The apparent activation energy of decomposition of CaCO3 found to be decreased with decreasing average particle size of nanocrystalline calcium carbonate.

Influence of extractions on physicochemical characterization and bioactivity of Piper nigrum oils: Study on the non-isothermal decomposition kinetic

Black pepper oils have been investigated frequently in the recent years. However, there is a significant variation in physicochemical properties and bioactivity of oils depended on extraction techniques. In this study, the systemic investigation of four various extraction methods was performed to evaluate the physicochemical characterizations, antioxidant and antibacterial activity. The investigation of 1H NMR, FTIR and UV–Vis spectra confirmed presence of non-volatile components in oils extracted through supercritical CO2 and hexane-soaking extractions which induced their typical thermal properties. The isothermal behaviour of extracted oils related to evaporation was within range of 3.2–7.3% (w/w) at 27 °C. The SEM images of the black pepper confirmed different operation manners of mechanism between extractions using the solvents and heating process. The lowest MIC for both essential oils from conventional hidrodistillation and microwave-assisted hidrodistillation against two bacteria including E. coli and B. subtilis were found to be 137 µg mL−1. The non-isothermal decomposition kinetics were investigated on the essential oil of microwave-assisted hydrodistillation extraction. The activation energies and pre-exponent factors of non-isothermal decomposition were found to be in range of 36.5–73.7 KJ mol−1 and 4.98 × 103–1.97 × 108 s−1, respectively, dependent on conversional fractions of the oil. The results revealed that chemical components, physicochemical properties and bioactivity of black pepper essential oils depended on the extraction techniques.

Non-isothermal decomposition kinetics, X-ray diffraction, infrared spectrum and antimicrobial studies of gamma irradiated barium doped diaquamalonatozinc(II)

Abstract The present investigation probes into the effect of gamma irradiation as well as doping on non-isothermal decomposition kinetics, structural, spectral and antimicrobial studies of barium doped diaquamalonatozinc(II). The compound were prepared by reported procedures and characterized by elemental analysis and spectral studies. Pure dried samples of uniform mesh size were encapsulated in glass ampoules and irradiated to 200 kGy using 60Co gamma rays. Non-isothermal studies of barium doped [Zn(mal)(H2O)2] were done before and after gamma irradiation by Coats-Redfern method. Results revealed that activation energy and associated kinetic parameters were lowered upon irradiation as well as doping. From X-ray diffraction studies both unirradiated and irradiated samples are found to be monoclinic. Lattice parameters are changed after irradiation. Change in intensity of FTIR bands were observed after irradiation. Antimicrobial studies revealed irradiation induced activity towards Escherichia coli, Staphylococusaureus and Sacchromycescerevisiae.

Thermal analysis of the prepared lignin/graphene oxide/polyurethane composite

Lignin/graphene oxide/polyurethane composite was prepared for removing polyaromatics from wastewater. X-ray and TEM are used for the characterization of the prepared composite. Thermal analysis was carried out for two reasons. One reason to ascertain the composite formation and the second to study the thermal stability of the synthesized composite. The kinetic parameters for each one of the decomposition steps were calculated through four methods of the non-isothermal decomposition kinetics calculations, and the kinetic mechanisms were determined by analyzing the thermal data by using thirty-five solid-state reaction models. The results showed that the mechanisms of decomposition steps depend on the type of starting materials. It was observed as the thermal decomposition that lignin passes through an unjustified mechanism. Graphene oxide shows a two-dimension diffusion mechanism. However, the synthesized Lignin/Graphene oxide/Polyurethane composite exhibits a chemical reaction mechanism (one and a half order and second order. The thermodynamic parameters ΔS#, ΔH# and ΔG#, were also computed and discussed.

Non-isothermal decomposition kinetics of in-chain functionalized poly(MMA-co-ethylene)

Efficient incorporation of polar monomers in polyolefin can lead to many desirable properties in the parent chain. Herein, we report the synthesis of ethylene and methyl methacrylate (MMA)-based copolymers by transition metal-catalysed reverse atom transfer radical polymerization technique with controlled ethylene feed pressure. Successful copolymerization was confirmed by 1H nuclear magnetic resonance analysis. With increasing polymerization time, resultant copolymers exhibit bimodal molecular weight distributions with controlled high molecular weight component and less-controlled low molecular weight component as confirmed by size-exclusion chromatography analysis. Morphological and crystal structures of the copolymer were established using scanning electron microscope and X-ray diffraction analysis, respectively. Thermogravimetric analysis of the copolymer under non-isothermal condition shows a two-step decomposition process with the major decomposition in the range of 320–450 °C. Based on approaches of Friedman and Flynn–Wall–Ozawa, model-free multivariate nonlinear regression analyses were performed to find out the formal mechanisms, kinetic model and its corresponding kinetic triplets. The results revealed the nth-order (Fn) mechanism responsible for the decomposition of the copolymer. The estimated kinetic parameters for the decomposition of poly(MMA-co-ethylene) copolymer were Ea= 227.80 kJ mol−1 and A = 6.76 × 1015 s−1.

Thermal behavior and non-isothermal decomposition reaction kinetics of catalyzed hniw-cmdb propellant

The thermal behavior under pressure of 0.1, 4, and 7 MPa and non-isothermal decomposition reaction kinetics under pressure of 4 and 7 MPa of the composite modified double base propellant containing hexanitrohexaazaisowurtzitane (HNIW-CMDB propellant) was investigated by differential scanning calorimetry (DSC). The results showed that there are two exothermic peaks on DSC curve under 0.1 MPa. The exothermic peak temperature decreases with surroundings pressure increasing. There is only one exothermic peak on every high pressure DSC curve. The exothermic peak temperature under every pressure increases with heating rate increasing. The exothermic decomposition kinetic parameters of the propellant changed while the reaction mechanism function didn’t change when catalyzer was added into propellant or testing surroundings changed. The kinetic equation of exothermic decomposition reaction mechanism under 4 MPa and 7 MPa are Avrami-Erofeev (n=2/3).

Preparation of in-situ compatibilized PLA/starch composites and its non-isothermal pyrolysis kinetics

A fully degradable PLA/starch composite was prepared by one-step in-situ compatibilization method. The effects of raw materials ratio and maleic anhydride （MAH） dosage were studied by thermogravimetric analyzer (TG) and scanning electron microscopy (SEM). The thermal stability and microstructure of the composites were investigated, and the non-isothermal thermal decomposition kinetics of the composites were discussed. The DTG results show that there are two distinct maximum decomposition rate peaks in the unmodified composites. After the MAH is added, the maximum decomposition rate peaks of the composites are close to each other. In addition, as the MAH dosage increases, the maximum rate of decomposition peak gradually shifts to a lower temperature. The SEM results show that the compatibility of the composites is improved after the addition of MAH. And both the Kissinger and Flynn-Wall-Ozawa methods are well described for the non-isothermal thermal decomposition kinetics of PLA and PLA/starch composites.

Physicochemical characterizations, antimicrobial activity and non-isothermal decomposition kinetics of Cinnamomum cassia essential oils

ABSTRACTThe extraction of essential oils from Cinnamomum cassia bark and leaf was carried out by hydrodistillation (HD) and microwave-assisted hydrodistillation (MAHD). Chemical compositions of volatile compounds were determined by GC/MS, 1H-NMR and infrared spectroscopy analysis. The dominant constituents found in the essential oils were aromatic compounds (> 90%) including (E)-cinnamaldehyde (CAL) and (E)-cinnamyl acetate (CAC) as the major components. The thermogravimetry (TG) method was used to study thermal stability and volatilization of the oils at room temperature. The bark essential oils exhibited inhibitory effects against a bacterial strain, S. aureus and a yeast strain, S. cerevisiae at MIC value 200 µg/mL. The decomposition kinetic of the essential oils was studied via the isoconversional kinetic models using the TG data. Two the isoconversional models, Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) were used to determine activation energies (Ea) for decomposition of the essential oils.