Self-accelerating Decomposition Temperature Research Articles

Considerations for the safe handling and processing of unstable materials

AbstractWe evaluate the instability hazards of initiators, monomers, and other unstable materials during storage and handling in individual containers, pallets of containers, and storage and process vessels. We propose a simplistic model to analyze the temperature–time profile of an unstable chemical, given heat transfer from/to the environment, heat generation due to decomposition and other reaction kinetics, and heat generated from auxiliary equipment (e.g., agitators/mixers, pumps, vessel jackets). Lumped capacitance‐based heat transfer and decomposition kinetics are integrated to predict self‐accelerating decomposition temperature (SADT), self‐accelerating polymerization temperature (SAPT), and the temperature profile given exposure conditions (e.g., ambient temperature and additional sources of heat). Case studies related to the storage and processing of unstable liquid monomers (i.e., methyl methacrylate, MMA), and organic peroxides, (i.e., tert‐butyl peroxybenzoate, TBPB), are presented. We also provide recommendations on determining safe storage and processing temperatures and steps to prevent emergency situations and include an overview of thermal analysis and data treatment procedures which might affect chemical process safety recommendations.

Analysis of thermal stability for slow burning propellant based on isothermal testing: Self‐accelerating decomposition temperature (SADT) calculation and validation

AbstractBurning rate suppressants (BRSs) refer to a series of additives that reduce the burning rate of propellants, crucial for achieving sustained and stable thrust. This research focuses on assessing the impact of ammonium sulfate and ammonium oxalate on thermal stability and their potential as BRSs. Due to the stronger inhibitory effect of ammonium sulfate on the AP proton transfer process, the activation energy of propellant's first decomposition can be increased from 94.71 kJ mol−1 to 129.69 kJ mol−1 at a 3 % addition level. Based on Semenov model, the self‐accelerated decomposition temperatures (TSADT) were calculated and validated through 7‐day isothermal test. Introducing ammonium sulfate and ammonium oxalate raised the TSADT from 197.31 °C to 220.90 °C and 215.06 °C, respectively, deviating less than 4 % from experimental results. Among the propellants tested, those with ammonium sulfate showed prolonged response delay times (44.43–33.60 h), lower superheating temperatures (222.8–445.5 °C), and reduced mass loss rates (33.0–71.4 %) after 7 days of isothermal storage at 220–240 °C. The consistency between thermal analysis and isothermal test underscores the significant impact of activation energy on thermal stability.

Effect of Cubic Crystal Morphology on Thermal Characteristics and Mechanical Sensitivity of PYX

To investigate the influence of the cubic crystal morphology on the thermal properties and sensitivity of 2,6-bis(picrylamino)-3,5-dinitropyridine (PYX), cubic PYX (CPYX) crystals were prepared using the antisolvent method. Scanning electron microscopy (SEM), laser particle size analysis, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were used to characterize the morphology, particle size and structure of the prepared products. The thermal behavior, thermal decomposition kinetics, thermal safety parameters and thermal decomposition mechanism of CPYX were investigated by differential scanning calorimetry–thermogravimetry–mass spectrometry–Fourier transform infrared spectrometry (DSC-TG-MS-FT-IR) and in situ FT-IR experiments. Meanwhile, the mechanical sensitivity of CPYX was determined by means of the explosion probability method. The results showed that the product had a smooth cubic morphology and small crystal aspect ratio with an average particle size (d50) of 10.65 μm, but it had no distinct differences from the crystal structure of raw PYX (RPYX). The thermal decomposition peak temperature, the self-accelerating decomposition temperature and the critical temperature of the thermal explosion of CPYX increased by 7.2 °C, 6.1 °C and 10.4 °C, respectively, compared to RPYX. Similarly, the apparent activation energy increased by 15%. Besides these, the impact sensitivity and friction sensitivity of CPYX decreased by 36% and 20%, respectively, compared to RPYX. The decomposition process of CPYX contains two stages. The first stage involves the breakage of N-H bonds and -NO2 groups with the release of CO2, N2O, NO, HCN and H2O, followed by the thermal decomposition of the resulting intermediate and the release of CO2, N2O and HCN in the second stage.

Calorimetric and kinetic evaluation of thermal stability and process safety in tert-butyl peroxy-2-ethylhexanoate and tert-butyl peroxybenzoate

This study evaluated the thermal stability and process safety of tert-butyl peroxybenzoate (TBPB), tert-butyl peroxy-2-ethylhexanoate (TBPO), and their mixture. Thermogravimetric (TG) analysis, differential scanning calorimetry (DSC), and accelerated rate calorimetry were used to elucidate the thermal behavior and breakdown kinetics. The TG results indicated moderate to low breakdown temperatures for all samples, demonstrating their thermal stability. DSC revealed onset temperatures for exothermic disintegration between 66.66 °C and 104.23 °C. The mixture had two distinct exothermic peaks, signifying the thermal decomposition of the mixture was such that the characteristic temperature and heat of the reaction were between those of TBPB and TBPO. Using Heat–Wait–Search methodology, the study identified thermal runaway exothermically. Under pseudoadiabatic conditions, the mixture exhibited greater increases in temperature and pressure—of 115.06 °C and 28.77 bar, respectively—compared with the individual compounds. To elucidate the apparent activation energy (Ea) and reaction kinetics, the study applied models developed by Arrhenius, Flynn-Wall-Ozawa, Friedman, Kissinger, and Starink. The Ea values obtained based on the TG, DSC, and ARC experiments were approximately 50.47, 98.19, and 99.71 kJ/mol, respectively, and were lower than those of TBPB and TBPO pure substances. The self-accelerating decomposition temperature of TBPB/TBPO decreased from 34 to 32 °C as the packaging of TBPB/TBPO was increased from 25 to 100 kg and was more than 10 °C lower than that of the individual substance. These findings offer a framework for evaluating the thermal risks associated with TBPB and TBPO, particularly when mixed. They contribute to the safe transit, storage, and handling of industrial organic peroxides, enriching our collective understanding of the stability and safety of these compounds.

Prediction of control temperature and emergency temperature of monadic/binary aromatic nitro compounds by quantitative structure-property relationship: correlation study of self-accelerating decomposition temperature in thermal hazard assessment.

The thermal hazard of reactions caused by the structural instability of aromatic nitro compounds is a major concern in the field of chemical process safety and one of the main causes of major thermal runaway (TR) accidents such as fire and explosion. Among them, the self-accelerating decomposition temperature (SADT), as an important parameter, has been widely used to evaluate the thermal hazards of aromatic nitro compounds in actual storage and transportation processes. However, the control temperature (CT) and emergency temperature (ET), which depend on and are associated with SADT, have been rarely reported in previous studies. In this work, multiple linear regression (MLR) and artificial neural network (ANN) models for CT and ET were constructed based on the molecular descriptors corresponding to the stable structures of 27 monadic/binary aromatic nitro compounds, combined with advanced adiabatic accelerating calorimetric experiments and quantitative structure-property relationship (QSPR). The optimal subset of descriptors with significant contributions was screened out while the fit, predictive ability, and robustness of the four types of models were evaluated with internal and external validation parameters, and finally, two types of parameters (R2 and ARE) were selected as the main indicators for a comprehensive comparative analysis. The results show that the four models fit the experimental data well. During this period, the accuracy of ANN models is slightly higher than that of MLR models, and the QSPR models under the two modes (linear and nonlinear) are more inclined toward ET in prediction ability. Based on simplifying the calculation process and realizing rapid parameter prediction, this study is expected to provide technical support for engineering applications such as safe operation, safe storage and transportation of substances, and emergency response in the chemical industry. In this work, we tested and calculated the thermal safety parameters of 27 monadic/binary aromatic nitro compounds by ARC and AKTS and further used the PubChem database and Gaussian 09 software program to obtain and optimize their corresponding molecular structures. The geometric optimization process adopts DFT on the B3LYP level and the 6-31 + G(d, p) basis set, while the same functional and basis set was used for vibration analysis. The OpenBabel toolbox and ChemDES platform were used for transformation coding and descriptor calculation. Finally, IBM SPSS Statistics 24 and MATLAB software were used to construct MLR models and ANN models, respectively.

Thermal decomposition characteristics and thermal safety performance evaluation of HAN-based propellant under different external environmental stimulations

This research aims to investigate thermal characteristics and assess thermal hazards of hydroxylamine nitrate (HAN)-based liquid propellant using a combination of accelerating rate calorimeter and high-pressure differential scanning calorimetry. Adiabatic experiments revealed that the exothermic reaction initiated at 115.7 °C and a rise sharply was at 128.4 °C with a maximum self-heating rate of 164.3 °C/min and the exothermic event was accompanied by a pressure rise of 3.7 bar in 0.03s. The corrected values of adiabatic temperature rise and time to maximum rate were 605.6 °C and 1.46 min, which confirms the vulnerability of the propellant to undergo a catastrophic explosion. To prevent thermal loss prevention accidents, time to maximum rate was obtained as 24 h under 111.3 °C. The apparent activation energy calculated decreased greatly with the increase of storage temperature from 25 °C to 45 °C, and so did the thermal explosion temperature (Tb) and self-accelerating decomposition temperature (TSADT). Additionally, the linear relationship between Ea and T was E = 991.7–2.7904T. The reliability of TSADT prediction was validated through slow cook-off test. Furthermore, the propellant exhibited more violent thermal decomposition under high pressure, resulting in a higher peak power. The thermokinetic parameters related to this phenomenon were identified, specifically at pressure of 4.0 MPa.

Thermal hazard assessment of tert-butyl perbenzoate using advanced calorimetric techniques and thermokinetic methods

Tert-butyl perbenzoate (TBPB) is a common organic peroxide initiator in the polymer sector, and its thermal behavior and potential dangers are explored in this quantitative study. Advanced calorimetric techniques and thermokinetic models were used to examine the thermal stability and breakdown features of TBPB. During the first stage of the TBPB synthesis, the process safety analysis revealed a very exothermic reaction. Peak temperatures for TBPB thermal decomposition ranged from 133.37 to 156.64 °C, with heat release values of roughly 1279 ± 135 J/g, as determined by differential scanning calorimetry and thermogravimetric analysis. Apparent activation energies ranged from 78.78 to 133.92 kJ/mol in a thermokinetic analysis employing the Kissinger, Starink, ASTM E698, Friedman, Kissinger-Akahira-Sunose, and Flynn-Wall-Ozawa models. Based on multiple nonlinear regression analysis, a two-step reaction mechanism was postulated, one involving an autocatalytic reaction and the other involving a reaction of the nth order. In order to evaluate the thermal dangers related with TBPB, the self-accelerating decomposition temperature (SADT) and thermal risk index (TRI) were calculated. Based on TRI calculations, TBPB was assessed as having low thermal risk, with SADT values ranging from 40 to 60 °C depending on package size. These numerical findings add to our knowledge of the thermal risks posed by TBPB and shed light on how best to handle, store, and transport the compound for use in industrial settings.

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.

Experimental hazardous risk investigation of energetic styphnic acid analytical reagent in calorimetric analysis

Analytical reagents identify and manage metal pollution, a major environmental issue. Regrettably, these compounds' safety concerns, especially when heated, have been neglected. This research examines the thermal hazard of the extremely reactive analytical reagent styphnic acid. Differential scanning calorimetry, thermogravimetric analysis, and accelerating rate calorimetry examined styphnic acid's thermodynamics. Thermogravimetric analysis showed weight loss reactions starting at 127 °C and peaking at 208 °C. Differential scanning calorimetry showed an endothermic peak at 176 °C. The accelerating rate calorimetry test showed that styphnic acid self-accelerates at 237 °C after 196.5 °C. Kissinger, Ozawa-Flynn-Wall, and Kissinger-Akahira-Sunose thermokinetic models calculated apparent activation energy from 131.677 to 155.718 kJ/mol. A nonlinear regression analysis showed that styphnic acid undergoes a two-step autocatalytic reaction during heat degradation. Thermal safety was assessed by measuring time to conversion limit, maximum rate, total energy release, self-accelerating decomposition temperature, and adiabatic temperature rise. Styphnic acid is less stable at higher temperatures and its thermal hazards depend on heating rate. The computed SADT was 109.04 °C, with alarm and control temperatures of 104.04 and 99.04 °C, respectively. The risk matrix analysis based on Tad and TMRad suggests reducing thermal instability. This study on styphnic acid's thermal risks and safe storage and transit during analytical applications is beneficial.

Coupling effect on the thermal hazard assessment of hazardous chemical materials via calorimetric technologies and simulation approaches

The coupling effect of heat absorption and release exists in the thermal decomposition of a few chemical materials. However, the impact of the above coupling on thermal hazard assessment is not considered in the literature studies. In this work, nitroguanidine (NQ) and 1,3,5-trinitro-1,3,5-triazine (RDX) are selected as representative materials to explore the influence of the coupling effect on the thermal hazard assessment of chemical materials. The linear heating experiments of NQ and RDX are carried out by a microcalorimeter and synchronous thermal analyser. The thermal decomposition curves are decoupled by advanced thermokinetics software. The thermal decomposition and kinetic parameters before and after decoupling are calculated. The results of TG experiment show that both NQ and RDX began to lose mass during the endothermic stage. The endothermic melting and exothermic decomposition of NQ and RDX are coupled within this stage. The coupling effect has different degrees of influence on its initial decomposition temperature and safety parameters. Compared with the parameters in the coupling state, the initial decomposition temperature and adiabatic induction period after decoupling decrease. The self-accelerating decomposition temperature increases, and internal thermal runaway time decreases. In the thermal hazard assessment of chemical materials with coupling effects, the calculated parameters after decoupling should be taken as an important safety index.

Three ionic liquids as ‘‘smart’’ stabilizers for diethyl azodicarboxylate (DEAD)

As a homogeneous system consists of diethyl azodicarboxylate (DEAD) soluble in three ionic liquids (ILs), such as [BMIM][NTf2], [BMIM][BF4], [BMIM][PF6], the catalytic efficiency can be substantially improved. However, their compatibility and stability have not yet been understood. The present study combines Thermal Safety Software (TSS) with Semenov theory in an in-depth analysis of experiment data to elucidate the reaction mechanism of DEAD with solvents effect. The characteristic thermokinetic parameters of DEAD dissolved in these three ILs, which TSS simulated, were high and consistent with the experimental values. Evidence was presented which showed that the thermal decomposition reaction mechanisms were determined as N-order model when DEAD soluble in the three ILs, and the order of the compatibility was: [BMIM][NTf2] > [BMIM][BF4] > [BMIM][PF6]. In this paper, the simulated value of self-accelerating decomposition temperature (SADT) was 48 °C for DEAD soluble in [BMIM][PF6] with a certain proportion, compared with the SADT value 43 °C calculated by Semenov theory. The research presented here confirms that 43 °C is the upper limit standard for the storage and transportation of DEAD, which paves a new avenue to facilitate the industrial process application of DEAD. The study concludes that three ILs are the smart stabilizers for DEAD, ameliorating its catalytic efficiency and thermal stability and laying a foundation for the rational design of catalysts toward green chemistry.

Thermal stability and decomposition mechanism analysis of 1, 1’-Azobis(cyclohexanecarbonitrile) by STA, DSC, ARC and TG-FTIR

1, 1′-Azobis(cyclohexanecarbonitrile) (ABCN) is a kind of azo compound, which is widely used as an initiator in the polymer industry. Plenty of heat will be released during the thermal decomposition, and fire or explosive accidents could happen when the cooling system of the polymerization reactor fails. In this manuscript, the thermal decomposition behavior of ABCN under a dynamic temperature environment was investigated by simultaneous thermogravimetric analyzer (STA). Differential scanning calorimeter (DSC) was used to detect the thermal effects of different stages of mass loss. The apparent activation energy was calculated by Kissinger-Akahira-Sunose methods (K-A-S methods). The thermal runaway behavior was investigated by accelerating rate calorimeter (ARC), which was used to predict time to maximum rate under adiabatic condition (TMRad). The results show that the temperatures at TMRad = 8 h and 24 h are 93.0 °C and 89.7 °C, respectively. The self-accelerating decomposition temperature (SADT) is 86.6 °C, which is calculated based on the thermal theory of Semenov. Since ABCN is used at 60–90 °C, a major accident could happen when the heat accumulated in the reactor is not removed timely. The risk of thermal runaway reactions for ABCN was defined against the risk matrix as level Ⅲ, which is an unacceptable risk. The carbon radicals and nitrogen were released during the decomposition of ABCN based on the experiment result of thermal gravimetric analyzer-Fourier transform infrared spectrometer (TG-FTIR) system. Several safety assessment parameters could supply references for the industry to alleviate thermal hazards and prevent critical incidents.

Effects of metal ions on thermal hazard of tert-butyl peroxy-3,5,5-trimethylhexanoate

As a commonly used initiator for polyethylene, tert-butyl peroxide 3,5,5-trimethylhexanoate (TBPTMH), with the molecular formula of C13H26O3, is more likely to decompose and cause fires and explosions. Understanding the thermal risks of TBPTMH mixed with common metal ions, potentially in containers and pipes, is important. In this work, by using differential scanning calorimetry (DSC) and Phi-Tec adiabatic calorimetry, the effects of CuCl2, FeCl3, CuBr2, and FeBr3 on the thermal decomposition of TBPTMH were investigated. Adiabatic kinetic analysis was performed and the apparent activation energy (Ea) was calculated by thermodynamic analysis. Time to maximum rise under adiabatic conditions (TMRad) and the self-accelerating decomposition temperature (SADT) under different packing qualities were reckoned. It was found that the thermal risk of TBPTMH was increased while mixing these metal ions, especially CuBr2. To ensure the safety of the substance in process industry, the temperature of TBPTMH in the presence of metal should be governed below 39.48 °C. This work was expected to provide some guidance for improving the process safety of TBPTMH.

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.

Bis(5-nitroimino-1,2,4-triazole-3-yl) methane-based energetic salts: Synthesis, crystal structure, thermal behavior and catalytic activity

Four energetic ionic salts of bis(5-nitroimino-1,2,4-triazole-3-yl) methane (BNTM) potassium (KBNTM), ammonium (A2BNTM), hydroxylamine ((HA)2BNTM), 1,3-diaminoguanidine ((DAG)2BNTM) have been synthesized and characterized by Elemental analysis(EA), Fourier infrared(FI) and Nuclearmagnetic resonance(NMR). Fortunately, the single crystals available for determination of KBNTM was acquired by slow evaporation of solvent method and its structure was discussed. The thermal behaviors of them were explored by Differential Scanning Calorimetry(DSC) and Thermogravimetry/ Derivative Thermogravimetry (TG/DTG) technique, and the result displayed that all of them had good thermal stability. The most possible mechanism function of main exothermic decomposition process were obtained (No.35 for KBNTM, No.6 for A2BNTM, No.24 for (HA)2BNTM, No.14 for (DAG)2BNTM). In addition, (HA)2BNTM has the best thermal safety, followed by KBNTM and A2BNTM according to the calculated value of self-accelerating decomposition temperature (TSADT) and critical temperature of thermal explosion (Tb). Moreover, the catalytic effects of four ionic salts on Cyclotrimethylenetrinitramine(RDX) and Octogen(HMX) were investigated respectively. The consequent showed that (HA)2BNTM accelerated the thermal decomposition of RDX and HMX, and reduced the decomposition temperature and apparent activation energy of RDX and HMX by 6.94 °C, 17.37 kJ·mol−1 and 4.17 °C, 2.77 kJ·mol−1, respectively. Surely, the thermal decomposition mechanism function of (HA)2BNTM/RDX was different from that of RDX (No.5, f(α)=6(1-α)2/3 [1-(1-α)1/3]1/2). In summary, (HA)2BNTM can be regarded as a potential energetic combustion catalyst with insensitive to physical impact (IS=16 J).

Thermal decomposition characteristics and runaway boundary conditions of HATO at adiabatic and high pressure situations

Dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (HATO) is a new generation of energetic material with low toxicity and high energy, which meet the needs of current weapon systems. To explore the effect of particle size on the thermal stability and thermal risks of HATO, decomposition reactions of HATO nanoparticles (NPs) and microparticles (MPs) were studied by accelerating rate calorimeter. The two decomposition stages for HATO NPs and HATO MPs were researched and the apparent activation energies were obtained with different reaction order. Furthermore, temperature at the time of no return and self-accelerating decomposition temperature of the two kinds of HATO were calculated and discussed. Moreover, the thermal behaviors of HATO NPs at atmospheric and high pressure were researched by differential scanning calorimetry. The decomposition of HATO NPs was more violent at high pressure with higher peak power and the related thermokinetic parameters at the pressure of 1.0 MPa were identified.

Thermal hazard evaluation of sodium dichloroisocyanurate via TG-MS, DSC, and ARC

Sodium dichloroisocyanurate (NaDCC) is a novel and effective material for sterilization, disinfection, and bleaching. However, the utilization of NaDCC has caused several thermal runaway incidents worldwide, raising attention to exploring its unknown thermal hazards. This paper simulated the different incident conditions to conduct a comparative study on the thermal stability and decomposition of NaDCC using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and accelerating rate calorimeter (ARC). The gaseous products of the thermal decomposition of NaDCC were analyzed by a thermogravimetry-mass spectrometer (TG-MS). Several kinetic methods were used to calculate Ea of the pyrolysis reaction of NaDCC under different conditions. TMRad and self-accelerating decomposition temperature (SADT) were calculated based on the thermodynamic and kinetic analysis. The results of TMRad showed that the adiabatic induction period decreased significantly, and the risk of losing control enlarged with increasing temperatures. Meanwhile, by comparing the SADT of NaDCC under several common packaging materials, the chemical plastic drums should be used for packaging materials of NaDCC. The result clarifies the reason for incidents and provides the fundamentals and valuable data for safe preparation, production, transportation, and storage of NaDCC.

Thermal risk classification optimization of flammable aromatic nitro compounds: Experiments and QSPR models

AbstractIn view of the frequent occurrence of major fires and explosions in the production, transportation, and storage of aromatic nitro compounds, the reactive thermal hazards of these compounds have attracted widespread attention in the chemical industry. Thermal hazard assessment is of great significance for the standardized storage of reactive chemicals. Based on adiabatic calorimetry and quantitative structure–property relationship (QSPR) prediction, a thermal hazard assessment and classification method dominated by the molecular structure of nitro compounds were proposed. While obtaining thermodynamic parameters, stable configuration and molecular descriptors, the prediction models were constructed by multiple linear regression (MLR) and artificial neural network (ANN), respectively, including self‐accelerating decomposition temperature (SADT), maximum power density (MPD), and the apparent activation energy (Ea). On this basis, SADT, H50, and Ea were selected as the possible characterization parameters of thermal risk of nitro compounds, while MPD and ΔTad were selected as the characterization parameters of consequence severity. When combined with weight and reference TNT, this method comprehensively evaluated the thermal hazards of nitro compounds and divided them into four types of thermal hazard levels. By comparing the method with the previous classification standards, it is found that the evaluation method is expected to provide theoretical support for the safe standardized storage of nitro compounds in chemical enterprises.

Experimental study on thermal runaway of sodium nitrate-containing hazardous waste during thermal treatment

Sodium nitrate-containing organic solid waste (NaNO3-OSW) has been classified as hazardous waste because it engendered severe fire and explosion risk, while large amounts of NaNO3-OSWs were generated during the metal recovery process from e-waste recently. This study aims to characterize thermal runaway behavior and reaction mechanism of NaNO3-OSW via theoretical and experimental analysis. Component characterization results show that this waste contains 23.3% wt. NaNO3, mixed with 11.8% wt. ascorbic acid, 47.2% wt. dehydroascorbic acid, and 17.7% wt. polyvinylpyrrolidone. Thermal risk assessment could provide guidance on the kind of safety measurements. Results present that this waste is thermal sensitive with high deflagration potential while its minimum ignition temperature is 290 ℃, and the maximum explosion pressure is 0.51 MPa. The predicted self-accelerating decomposition temperature is 148.3 ℃ for a standard 50 kg package. Combustion behavior characterization could offer insights into the realization of essential safety during disposal. Results reveal that the self-redox reaction between organic compounds and NaNO3 has occurred in the temperature range of 276–405 ℃. The reaction mechanism suggests that the catalytic decomposition of ascorbic acid by melting NaNO3 is the crucial factor that results in intense combustion. The findings of this study provide practical insights into the in-situ disposal of this waste by removing organic compounds at low temperatures.

Development of Prediction Models for the Self-Accelerating Decomposition Temperature of Organic Peroxides.

Thermal risk assessment is very important in the primary stages of chemical compound development. In this study, a model to estimate the self-accelerated decomposition temperature of organic peroxides was developed. The structural information of compounds was used to calculate descriptors, on which partial least-squares (PLS) regression and support vector regression were applied for temperature prediction. Molecular mechanics and density functional theory calculations were performed before descriptor calculations, for structure optimization, using a genetic algorithm for variable selection. Structure optimization and variable selection immensely improved the prediction accuracy. Thus, a PLS model, with R2 = 0.95, root mean square error = 5.1 °C, and mean absolute error = 4.0 °C, exhibiting higher accuracy than existing self-accelerating decomposition temperature prediction models, was constructed.