Decomposition Kinetic Parameters Research Articles

Thermal stability of the DPT reaction system synthesized by acetic anhydride method

The adiabatic decomposition of a reaction mixture prepared in DPT using the acetic anhydride method was analyzed using an Accelerating Rate Calorimeter (ARC) to determine the thermal decomposition characteristics and kinetic parameters of the reaction solution at different reaction times. The adiabatic decomposition kinetics were modeled using TSS software, and the corresponding kinetic parameters were derived. Subsequently, a numerical simulation was employed to predict the critical ambient temperature of the reaction liquid in the reactor in case of cooling failure. The results indicated that the CT value was lowest at a feeding time of 10 minutes, highest at a holding time of 15 minutes, and closest to the cooling temperature of the reactor at a feeding time of 30 minutes.

Study on the Thermal Decomposition Risk of 3,7-Dinitro-1,3,5,7-tetraazabicyclo[3,3,1]nonane under Different Conditions.

Given its role as a pivotal intermediate in octogen production, the thermal safety of DPT is of paramount importance due to its significant thermal hazard. To assess the potential thermal hazard associated with its decomposition, a nonisothermal DSC experiment and an ARC test were conducted. For the acquisition of more precise thermal decomposition kinetic parameters, the impact of various crucible types on the experimental outcomes was scrutinized. The DSC results indicate that the precise thermal decomposition process of DPT, an autocatalytic decomposition material, can be accurately ascertained by using a high-pressure sealed crucible test. The authentic thermal decomposition process of DPT encompasses two critical reactions: the decomposition of DPT itself and the secondary reaction and decomposition of its byproducts. A robust thermal decomposition kinetic model was established, integrating the findings from the DSC test results. Subsequently, the risk of thermal explosion during DPT storage was simulated by using a kinetic numerical simulation approach.

Revisiting biomass compositions determination using thermogravimetric analysis and independent parallel reaction model

The determination of biomass composition via thermogravimetric analysis (TGA) has been a subject of considerable interest for many years. The current work proposes a revised workflow for determining the amounts of cellulose, hemicellulose, and lignin in biomass by combining TGA under an inert atmosphere with analyses of extractives and ash. An independent parallel reaction (IPR) model used for the deconvolution of the derivative thermogravimetry data was improved by constraining model parameters, i.e., thermal decomposition kinetic parameters and char fractions of cellulose, hemicellulose, and lignin, with values compiled from the literature using statistical analysis. The workflow is developed and demonstrated using cellulose and starch mixtures and then applied to biomass with varying levels of ash, including pine, birch, and oak wood, switchgrass, and pine bark. Using extractive-free biomass in the new TGA-IPR workflow improved the composition results compared with untreated biomass. The compositions determined by this method agreed well with values reported in the literature (within approx. 8 wt%) for the tested samples. The results demonstrate improved biomass composition accuracy using an accessible and rapid TGA-based approach.

High-temperature dolomite decomposition: An integrated experimental and computational fluid dynamics analysis for calcium looping and industrial applications

The thermal decomposition of dolomite was investigated as a potential low-cost and high-performance precursor to CaO in the calcium looping process, which shows great promise when integrated with carbon capture and storage and thermochemical energy storage technologies. Experimental thermogravimetric analysis (TGA) and computational fluid dynamics (CFD) modelling were used to study the isothermal calcination process of dolomite considering industrially relevant conditions, focusing on high temperatures (800–1200 °C), sample sizes (12–18 mm), different calcination atmospheres (air and CO2) and gas velocities (0.2–3 m·s−1). Based on experimental findings, optimal calcination conditions for industrial applications require a minimum temperature of 1000 °C to achieve complete conversion within 25 min and smaller particles for faster conversion rates. Calcination atmosphere is flexible as CO2 concentration shows minimal impact on conversion rates. Laminar flow gas velocity is not a limiting factor and its value should be considered based on other aspects (i.e., costs). Higher particle initial porosity is seen to increase reactivity and thermal efficiency. The CFD model was validated with experimental data, resulting in determination coefficients (R2) higher than 0.9 for all simulated cases. Model predictions revealed insights into particle level phenomena during calcination, such as increased rates at higher temperatures with proportional self-cooling effects, wake formation enhancing fluid mixing and the presence of a thermal boundary layer reducing heat transfer. The findings presented in this paper can be used in future work to determine reaction mechanisms and optimize kinetic parameters for decomposition, as well as further optimize other aspects of the process at industrially relevant operating conditions.

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.

Thermal hazards assessment of three azo nitrile compounds

Commercially available azo radical compounds provide efficient initiation of many chemical reactions. However, such energetic azo group initiators have thermal stability issues at ambient or even sub-ambient temperatures. Azo decomposition initiated by heat and/or light can generate significant amounts of nitrogen gas with rapid pressure increases, presenting a safety challenge for shipping, storage and usage. In this study, three azo nitrile compounds were examined using various thermal calorimetry techniques with only 5 mg to 1 g scale samples. We obtained calorimetric data on exothermic activity and gas generation. The testing results were subsequently analyzed by using differential iso-conversional methods to obtain key decomposition kinetics parameters, including activation energy and pre-exponential factor. The model was then validated and utilized for prediction of several key safety parameters for scale-up applications, including Self-Accelerating Decomposition Temperature (SADT), Time to Maximum Rate (TMR), temperature profiles at iso- or non-isothermal conditions for shelf-life evaluation, adiabatic temperature rise, and rate of pressure increase. For compounds such as 2,2’-azobis-(2,4-dimethylvaleronitrile) and 1,1’-azobis(cyclohexane-1-carbonitrile) which went through phase transitions associated with thermal decomposition, the thermal decomposition behavior of liquid and solid state was found to differ in characteristic. This methodology for thermal decomposition kinetics assessment enables safe storage, handling, and scale-up process preparation.

Facile Recrystallization Process for Tuning the Crystal Morphology and Thermal Safety of Industrial Grade PYX.

In this study, the crystal appearance of industrial grade 2,6-diamino-3,5-dinitropyridine (PYX) was mostly needle-shaped or rod-shaped with an average aspect ratio of 3.47 and roundness of 0.47. According to national military standards, the explosion percentage of impact sensitivity s about 40% and friction sensitivity is about 60%. To improve loading density and pressing safety, the solvent-antisolvent method was used to optimize the crystal morphology, i.e., to reduce the aspect ratio and increase the roundness value. Firstly, the solubility of PYX in DMSO, DMF, and NMP was measured by the static differential weight method, and the solubility model was established. The results showed that the Apelblat equation and Van't Hoff equation could be used to clarify the temperature dependence of PYX solubility in a single solvent. Scanning electron microscopy (SEM) was used to characterize the morphology of the recrystallized samples. After recrystallization, the aspect ratio of the samples decreased from 3.47 to 1.19, and roundness increased from 0.47 to 0.86. The morphology was greatly improved, and the particle size decreased. The structures before and after recrystallization were characterized by infrared spectroscopy (IR). The results showed that no chemical structure changes occurred during recrystallization, and the chemical purity was improved by 0.7%. According to the GJB-772A-97 explosion probability method, the mechanical sensitivity of explosives was characterized. After recrystallization, the impact sensitivity of explosives was significantly reduced from 40% to 12%. A differential scanning calorimeter (DSC) was used to study the thermal decomposition. The thermal decomposition temperature peak of the sample after recrystallization was 5 °C higher than that of the raw PYX. The thermal decomposition kinetic parameters of the samples were calculated by AKTS software, and the thermal decomposition process under isothermal conditions was predicted. The results showed that the activation energy (E) of the samples after recrystallization was higher by 37.9~527.6 kJ/mol than raw PYX, so the thermal stability and safety of the recrystallized samples were improved.

Kinetics and mechanism of hydrogen release from isothermal decomposition of AlH3

Aluminum trihydride is an ideal hydrogen storage material. Aluminum trihydride is prone to dehydrogenate in ambient atmosphere due to its low chemical and thermal stability. Therefore, its thermal stability has become the focus of attention during production, use, transportation, and storage. In this paper, the pressure curve of the gas produced during the thermal decomposition of AlH3 with time at 333–373 K was obtained using an isothermal thermal decomposition gas measurement device. The isothermal thermal decomposition kinetic parameters of AlH3 were calculated using Arrhenius equation and mode matching method. The results show that the decomposition of AlH3 can be divided into three stages. The time required for AlH3 to reach a certain decomposition depth at different temperatures was obtained from Semenov equation. At room temperature, the time required for the decomposition depth of AlH3 (purity>99%) to reach 0.1% is 224.7 days in a vacuum environment. Furthermore, the possible decomposition mechanism of AlH3 was proposed by X-ray diffraction, gas chromatography, and transmission electron microscopy.

Computer-aided design of initiator utilization strategies for vinyl chloride suspension polymerization with constant reaction rate

From the viewpoint of polymer reaction engineering (PRE), polymerization with constant reaction rate is beneficial for reducing manual operations and promoting production efficiency. Using vinyl chloride (VC) suspension polymerization as a model system, manipulating the radical concentration by radical concentration-dependent optimization (RCO)-based initiators mixing (IM) strategy or continuous initiator dosing (CiD) strategy enables the polymerization with constant reaction rate. Case studies have been done to illustrate how the RCO-based IM strategy works for binary initiator combination screening and how to conduct VC suspension polymerizations with different reaction rates using RCO-based IM strategy. Importantly, decomposition kinetic parameters estimated for virtual initiators can be used for guiding the design of the capable initiators. Moreover, in the single initiator systems, the applicability of the RCO-based CiD strategy has been demonstrated by conducting VC suspension polymerization with different reaction rates and different temperatures. Optimal dosing rate profiles of the initiator can be provided for the cases demonstrated. It is expected that both RCO-based IM and CiD strategies can be extended to other free radical polymerization systems.

Isothermal decomposition of AlH3/hydrogen absorbents

In this article, the isothermal decomposition dynamics research instrument was used to investigate the interaction between three hydrogen absorbents and AlH3, including C60, C70, and 1,4-bis (phenylethynyl) benzene (DEB). The gas volumes emitted by AlH3, AlH3/C60, AlH3/C70, and AlH3/DEB during the 48 h vacuum stability experiment were 2.85, 2.41, 1.92 and 2.02 mL/g, respectively. The isothermal thermal breakdown of the three materials was investigated simultaneously at 333–393 K. The isothermal thermal decomposition kinetic parameters of AlH3/C60, AlH3/C70, and AlH3/DEB were determined using the Arrhenius and model-fitting method by using the pressure–time curve of the decomposition and release gas of the mixed sample of AlH3 and three hydrogen absorbents. AlH3/C60, AlH3/C70, and AlH3/DEB had activation energies of 118.2, 116.9, and 116.8 kJ·mol−1, respectively and pre-exponential factors of 20.49, 20.16, and 20.19, respectively. By using XRD and TEM, the thermal breakdown products were examined.

Comparative Analysis of Thermal Decomposition Kinetics of Copolymers Based on Polyethylene Glycol Fumarate with Methacrylic Acid

The thermal properties of a copolymer based on polyethylene glycol fumarate with methacrylic acid in a nitrogen atmosphere were studied in this paper. Four various heating rates and two types of a polyester resin composition were used. The analysis of thermal decomposition kinetics was implemented. Three kinetics methods namely Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose and Friedman were applied. Curves of a thermogravimetric analysis demonstrated that the thermal decomposition of copolymers with different molar ratios was observed. It was determined that the kinetic data depends on the studied copolymers’ composition. The obtained data showed a good convergence in various heating rates. Also, the thermodynamic characteristics were calculated namely the changes in the Gibbs energy (ΔG), enthalpy (ΔH) and entropy of activation (ΔS). The Achar-Brindley-Sharp method was used to find the invariant kinetic parameters of decomposition. Thus, the the kinetic compensation effect was applied to define a reaction model and a pre-exponential factor. A main phase of the copolymer decomposition in a narrow temperature range was determined. It was attested by a peak on the differential curve. An insignificant mass loss of the volatile-matter yield was observed in the range of 30–150 °C.

Catalytic performance of nano-sized cobalt copper ferrite on thermal decomposition of ammonium nitrate

Ammonium nitrate (AN) is being explored as a high energetic oxidizer in propellants. The utilization of pure AN in propellants suffers from a low burning rate. To improve the burning rate, it is important to improve the thermal decomposition characteristics of AN to fasten its thermal decomposition. The effect of CoCuFe2O4 additive was explored to improve the thermos-kinetic parameters of AN's thermal decomposition. Coprecipitation was used to synthesize nanocrystalline CoCuFe2O4. The thermodynamic and kinetic parameters of decomposition of AN: CoCuFe2O4 were investigated using TG-DSC-DTA analysis at 5, 10, and 15 °C min−1. The thermodynamic and kinetic studies suggest that the thermal decomposition of AN+CoCuFe2O4 was more favorable than AN. The decomposition of AN+CoCuFe2O4 occurs at a lower 10 °C lower temperature with ∼44 % decrement in the activation energy and decreased pre-exponential factor. The faster decomposition at a lower temperature was obtained for AN+CoCuFe2O4 composition. Nano-sized particles with efficient optical and polarizable properties made this ferrite material easily separable and eco-friendly for the preparation of a chemical propulsion system based on AN. The AN+CoCuFe2O4 propulsion mixture can be utilized in place of pure AN for better thermal performance in a propellant system.•CoCuFe2O4 was able to influence the thermal decomposition parameters of ammonium nitrate (AN).•AN+CoCuFe2O4 decomposes at lower activation energy with a faster decomposition than pure AN.•Thermodynamics suggest favorable decomposition of AN+CoCuFe2O4 than pure AN.

Thermal degradation and kinetic studies of redwood (Pinus sylvestris L.)

AbstractIn this scientific paper, thermochemical conversion of redwood (RW) was studied. Using the thermogravimetric analysis' technique (TGA), the thermal behavior of RW samples was examined at four heating rates ranging from 5 to 20 K min−1 in inert atmosphere between 300 and 900 K. Two main objectives have been set for this study; the first one was the determination of the kinetic decomposition parameters of RW (Pinus sylvestris L.), and the second one was the study of the variation of characteristic parameters from the TG-DTG curves of the main RW's components, such as; cellulose, hemicellulose and lignin. The kinetic analysis was performed using three isoconversional methods (Vyazovkin (VYA), Friedman (FR) and Flynn-Wall-Ozawa (FWO)), Avrami theory method and the Integral master-plots (Z(x)/Z(0.5)) method to estimate activation energy (Ea), reaction order (n), pre-exponential factor (A) and model kinetic (f(x)) for the thermal decomposition of cellulose, hemicellulose and lignin components.The DTG and TG curves showed that three stages identify the thermal decomposition of RW, the first stage corresponds to the decomposition of hemicellulose and the second stage corresponds to the cellulose, while the third stage corresponds to the lignin's decomposition. For the range of conversion degree (x) investigated (0.1 ≤ x ≤ 0.7), the mean values of apparent activation energies for RW biomass were 127.60–130.65 KJ mol−1, 173.74–176.48 KJ mol−1 and 197.21–200.36 KJ mol−1 for hemicellulose, cellulose and lignin, respectively. Through varied temperatures from 550 to 600 K for hemicellulose, from 600 to 650 K for cellulose and from 750 to 800 K for lignin, the corresponding mean values of reaction order (n) were 0.200 for hemicellulose, 0.209 for cellulose and 0.047 for lignin. The pre-exponential factor's average values for three components of RW ranges from 0.08 × 1012 s−1 to 2.5 × 1012 s−1 (Ahemicellulose = 1.09 × 1012 s−1), 0.10 × 1014 s−1 to 0.28 × 1014 s−1 (Acellulose = 0.17 × 1014 s−1) and 3.07 × 1016 s−1 to 3.69 × 1016 s−1 (Alignin = 3.33 × 1016 s−1), respectively. The experimental data of RW had overlapped the D4, D2 and F3 in the conversion degree of 10–30%, 30–55% and 55–70% for the three components, respectively.

Synthesis, Spectroscopic Characterization, Biocidal evaluation Molecular Docking & DFT Investigation of 16-18 membered Macrocyclic Complexes of Cobalt (II).

Antimicrobial, DFT, and Docking representation of Cobalt (II) macrocyclic complexes. The online version contains supplementary material available at 10.1007/s12039-022-02109-2.

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.

Isothermal decomposition of CL- 20 before and after thermally induced ε-γ crystal transformation

The ε-γ crystal transformation of CL-20 (hexanitrohexaazaisowurtzitane) was examined using a self-made constant temperature decomposition gas measuring device, and the isothermal decomposition kinetic parameters of ε-and γ-CL-20 with different crystal phases were obtained. Results show that the pressure temporal curves of CL-20 before and after crystal transformation have their own decomposition mechanism, indicating that the phase transformation has a significant effect on CL-20 decomposition. The kinetic parameters of ε- and γ-CL-20 were also calculated by Arrhenius and Mode matching methods. The activation energy (Ea) of ε-CL-20 decomposition was 118.82 kJ·mol−1 in the temperature range of 423–443 K, and the Ea of γ-CL-20 decomposition was 77.74 kJ·mol−1 in the temperature range of 453–468 K. The storage life of ε- and γ-CL-20 was estimated by Semenov equation. When the reactivity reaches 0.5 %, the storage time of ε-CL-20 at room temperature (298 K) is 227.8 years. Finally, the gas and solid residues obtained after CL-20 decomposition by SEM, FT-IR, and GC techniques. The possible decomposition mechanism of ε-CL-20 was proposed.

Synthesis, characterization, and thermal decomposition kinetics of deuterated 1,3,5-triamino-2,4,6-trinitrobenzene

ABSTRACT TATB and TATB-d6 were synthesized using phloroglucinol as raw material. Their molecular structure and micromorphology of them were well characterized by FTIR, NMR spectroscopy, XRD and FE-SEM. The thermal behaviors of these compounds were studied with TG-DSC, and the non-isothermal kinetic decomposition parameters of the two compounds were gained using the method of Friedman (FM). The apparent activation energy value of TATB-d6 was larger than that of TATB, which indicated the heat stabilization of deuterated TATB particles was improved. Finally, the thermal detonation critical temperatures of these two products were also calculated and discussed.

Thermal energy simulation safety model of wupaolong fireworks based on Friedman method

The performance of firecrackers and fireworks in the dance, artillery and dragon competitive activities enhances appreciation and entertainment of wupaolong. Wupaolong has the meaning of dispelling evil spirits and eliminating disasters. With the development of fireworks preparation technology, wupaolong powder throwing technology also puts forward the requirements of low ignition point, rich color and low combustion and explosion temperature. In this paper, the effects of water content and environmental humidity on the thermal decomposition characteristics of pyrotechnic agents were studied by thermal analysis method. The thermal decomposition kinetic parameters of red pyrotechnic agents were determined by Friedman method. The effects of water content and environmental humidity on their thermal decomposition characteristics were summarized and analyzed. The thermal safety model studied in this paper can play a key role in improving the theory and technology of fireworks material components. And it creates the data micro-control processing of naked grain ignition time, ignition delay period, ignition temperature and ignition position of fireworks at different ambient temperatures. Experiments show that the optimized model scheme in this paper can analyze the thermal decomposition dynamics of different component grains and has high application value for improving the thermal safety of propellant.

The heating performance and kinetic behaviour of oil shale during microwave pyrolysis

In this study, the microwave pyrolysis of oil shales (MPOS) from Estonian Kukersite, Moroccan Tarfaya, Chinese Longkou, and Chinese Barkol were investigated. The heating performance of MPOS was also examined. A comparison study between MPOS and conventional oil shale pyrolysis (CPOS) was conducted, which included comparing the temperature profile, heating rate, weight loss at the same temperature, and the organic decomposition kinetic parameters. Results indicate that, under MPOS, both the maximum temperature (Tm) and average heating rate (γ) were influenced by the organic matter content in oil shale, and the effects were more significant at higher microwave powers (400–700 W) than at lower powers (200–400 W). Furthermore, both Tm or γ were linearly and/or exponentially correlated with microwave power with a breakpoint of 400 W in each correlation. Compared with CPOS, MPOS provided higher γ based on the same input powers and higher weight loss at the same temperatures. This demonstrates that MPOS requires much less processing time and a lower input energy than CPOS. Additionally, the kinetics of oil shale pyrolysis were modelled using the Kissinger method. For organic matter decomposition, MPOS decreased the activation energy by 13–39% and increased the reaction rate constant by at least 65%, compared to CPOS. This implies that under MPOS, higher powers are necessary to establish oil shale thermal reactivity and higher reaction rates can be obtained, thereby causing greater weight loss than with CPOS.

Effects of lipids on sludge and chlorella protein pyrolysis by thermogravimetry Fourier transform infrared spectrometry

Biomass pyrolysis has attracted attention; however, its development has been restricted by the formation of NOx precursors, which result mainly from protein pyrolysis. In addition, the effect of lipids on this process is not clear. We extracted proteins and lipids from chlorella and sewage sludge to investigate the thermal decomposition characteristics, thermodynamic properties, kinetic parameters, and reaction mechanisms of protein with or without lipids. Two model-free methods Flynn-Wall-Ozawa (FWO) and Friedman (FM) were used to calculate the kinetic energy. Between 150 and 600 ℃, the average activation energy (E) of sludge protein was 73.63 kJ/mol (FM) or 72.53 kJ/mol (FWO), whereas with lipids, it was 129.19 kJ/mol (FM) or 124.55 kJ/mol (FWO), indicating that lipids restrict the pyrolysis of sludge protein. There was no significant difference between E of chlorella protein pyrolysis with or without lipids. Moreover, the proteins in sludge and chlorella released less NH3 under the influence of lipids; however, the formation of HCN was affected slightly. The results of this study provide a reliable reference for the regulation of protein pyrolysis, considering the production of NOx precursors.