The thermal hazard evaluation of 1,1-di (tert-butylperoxy) cyclohexane by DSC using non-isothermal and isothermal-kinetic simulations

1,1-Di (tert-butylperoxy) cyclohexane (DTBPH) has been widely employed in the chemical industry. Unfortunately, organic peroxides have been involved in many serious fires and explosions in manufacturing processes, storage, and transportation. This study investigated the thermokinetic parameters by isothermal kinetic and non-isothermal-kinetic simulation, using differential scanning calorimetry (DSC) tests. DSC was applied to assess the kinetic parameters, such as kinetic model, frequency factor (ln k₀), activation energy (E_a), reaction order, and heat of reaction (ΔH_d). Comparisons of non-isothermal and isothermal-kinetic model simulation led to a beneficial kinetic model of thermal decomposition to predict the thermal hazard of DTBPH. Simulations of a 0.5 L Dewar vessel and 25 kg barrel commercial package in liquid thermal explosion models were performed and compared to the results in the literature. From the results, the optimal conditions for use of DTBPH to avoid violent runaway reactions during the storage and transportation were determined. This study established the features of thermal decomposition that could be executed as a reduction of energy potential and storage conditions in view of loss prevention.     

贫烟煤氧化热解反应的动力学分析

通过运用热分析的技术研究平顶山烟煤以及郑州嵩枫贫煤氧化热解反应的动力学特性.依据转化率将煤样的TG曲线划分为两个不同的温度区间进行动力学机理函数的探讨.通过对比分析整个TG曲线的氧化受热情况,将线性较好的机理函数带入DSC曲线进行分析验证,并求解出动力学参数以分析其氧化热解反应的特点.研究得出:这两种煤的氧化热解过程相似但同等条件下反应程度不同;在不同的反应阶段其化学反应级数不同并且相应过程中的TG曲线和DSC曲线反应级数一致;煤反应的活化能随着煤与氧反应过程的深入而增加,指前因子随着活化能的增加而增加且煤氧化反应过程是个分阶段的、多步反应以及相互联系促进的过程.     

Modeling thermal analysis for predicting thermal hazards relevant to transportation safety and runaway reaction for 2,2′-azobis(isobutyronitrile)

The pure decomposition behavior of 2,2′-azobis (isobutyronitrile) (AIBN) and its physical phase transformation were examined and discussed. The thermal decomposition of this self-reactive azo compound was explored using differential scanning calorimetry (DSC) to elucidate the stages in the progress of this chemical reaction. DSC was used to predict the kinetic and process safety parameters, such as self-accelerating decomposition temperature (SADT), time to maximum reaction rate under adiabatic conditions (TMR_ad), and apparent activation energy (E_a), under isothermal and adiabatic conditions with thermal analysis models. Moreover, vent sizing package 2 (VSP2) was applied to examine the runaway reaction combined with simulation and experiments for thermal hazard assessment of AIBN. A thorough understanding of this reaction process can identify AIBN as a hazardous and vulnerable chemical during upset situations. The sublimation and melting of AIBN near its apparent onset decomposition temperature contributed to the initial steps of the reaction and explained the exothermic attributes of the peaks observed in the calorimetric investigation.     

Efficiency characterization of fire extinguishing compound superfine powder containing Mg(OH)2

To improve the fire extinguishing efficiency of existing dry powders, a new type of superfine dry powder was prepared using magnesium hydroxide as an additive. In our study, a thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to analyze the thermal decomposition of the synthesized powders. The temperature of thermal decomposition, weight loss, and other thermodynamic parameters of the fire extinguishing powders were analyzed to explain the performance advantages of the compound superfine powder. Through a small-scale fire experiment, the physical parameters of the extinguishing process—such as extinguish time, powder dosage, smoke concentration, and minimum extinguishing concentration—were quantified for the suppression of a diesel fire using the different powders; these parameters were used to evaluate the fire extinguishing capacity and toxic gas suppression ability of the powders. TGA demonstrated that the compound superfine powder decomposed more quickly and its thermal decomposition process was much shorter than those of the other powders. The DSC data indicated that the compound superfine powder could decrease the characteristic temperature at each stage and thus the powder absorbed the flame's heat more quickly and suppressed flame propagation. The fire extinguishing test demonstrated that the consumption of the three types of fire extinguishing powder decreased with an increase in the driving pressure, and the order of powder dosage was as follows: commercial dry powder > superfine powder > compound superfine powder. Similarly, the order of minimum extinguishing concentration was as follows: commercial dry powder > superfine powder > compound superfine powder. Furthermore, the compound superfine powder exhibited a greater capacity for controlling toxic and harmful gas emissions.     

Characterization of Ti powders mixed with TiO2 powders: Thermal and kinetic studies

The fire and explosion risks of metal powders admixed with solid inertants have been extensively investigated for many years. However, it remains unclear why such solid mixtures have high potential fire and explosion risk even when mixed with high percentages of non-combustible solids. This paper investigates how to interpret these risks, from a microscopic perspective, with thermal and kinetic parameters including initial ignition temperature, mass unit exothermic energy, activation energy and risk index of spontaneous combustion. The results show that the initial ignition temperature based on TG (Thermogravimetry) analysis is related to ignition sensitivity, and increased with percentage of admixed solid inertant. The unit mass exothermic energy based on DSC (Differential scanning calorimetry) analysis is related to flame spread velocity. Activation energy and the risk index of spontaneous combustion can be used to explain the reactivity and spontaneous combustion hazard, respectively, of metal powders. We conclude that thermal and kinetic parameters may provide another way to describe the fire and explosion risk of combustible powders, especially for nano metal powders due to the laboratory safety in the normative tests for explosion parameter determination.     

Thermal hazard analysis of triacetone triperoxide (TATP) by DSC and GC/MS

Thermal degradation of triacetone triperoxide (TATP) was studied using differential scanning calorimetry (DSC) and gas chromatography/mass spectrometry (GC/MS). TATP, a potential explosive material, is powerful organic peroxide (OP) that can be synthesized by available chemicals, such as acetone and hydrogen peroxide in the laboratory or industries. The thermokinetic parameters, such as exothermic onset temperature (T₀) and heat of decomposition (ΔH_d), were determined by DSC tests. The gas products from thermal degradation of TATP were identified using GC/MS technique.In this study, H₂O₂ was mixed with propanone (acetone) and H₂SO₄ catalysis that produced TATP. The T₀ of TATP was determined to be 40 °C and E_a was calculated to be 65 kJ/mol. A thermal decomposition peak of H₂O₂ was analyzed by DSC and two thermal decomposition peaks of H₂O₂/propanone were determined. Therefore, H₂O₂/propanone mixture was applied to mix acid that was discovered a thermal decomposition peak (as TATP) in this study. According to risk assessment and analysis methodologies, risk assessment of TATP for the environmental and human safety issue was evaluated as 2-level of hazard probability rating (P) and 6-level of severity of consequences ratings (S). Therefore, the result of risk assessment is 12-point and was evaluated as “Undesirable” that should be enforced the effect of control method to reduce the risk.     

Reaction hazard and mechanism study of H2O2 oxidation of 2-butanol to methyl ethyl ketone using DSC,Phi-TEC II and GC-MS

Methyl ethyl ketone (MEK) oxidation via H₂O₂ with tungsten-based polyoxometalate catalysts has gained much attention with an ever-growing body of knowledge focusing on the development of environmentally benign processes in chemical industry. In this study, two calorimetry techniques, differential scanning calorimetry (DSC) and Phi-TEC II adiabatic calorimetry, were employed to analyze the thermal hazards associated with the 2-butanol oxidation reaction system. Hydrogen peroxide was the oxidant and a tungsten-based polyoxometalate as the catalyst. Gas chromatography-mass spectrometry was used for identification of the organic products. Important thermal kinetic data were obtained including “onset” temperature, heat of reaction, adiabatic temperature rise and self-heat rate. From DSC results, three exothermic peaks were detected with a total heat generation of approximately 1.26 kJ/g sufficiently to induce a thermal runaway. Possible reaction pathway for three stages were proposed based on both DSC and GC-MS results. One exotherm was detected by Phi-TEC II calorimeter and the pressure versus temperature profile together with the DSC and GC-MS data demonstrate the complexity of 2-butanol reaction system under both thermal screening and adiabatic conditions.     

Green thermal analysis for predicting thermal hazard of storage and transportation safety for tert-butyl peroxybenzoate

Liquid organic peroxides, such as tert-butyl peroxybenzoate (TBPB), have been widely employed in the petrifaction industry as a polymerization formation agent. This study investigated the thermokinetic parameters of TBPB by isothermal kinetic algorithms and non-isothermal kinetic equations, using thermal activity monitor III (TAM III) and differential scanning calorimetry (DSC), respectively. Simulations of 0.5 L, 25 kg, 55 gallon, and 400 kg reactors in liquid thermal explosion models were performed and compared to the results in the literature. A green thermal analysis was developed for a reactor containing TBPB to prevent pollution and reduce the energy consumption by thermal decomposition. It is based on the thermal hazard properties, such as the heat of decomposition (ΔH_d), activation energy (E_a), self-accelerating decomposition temperature (SADT), control temperature (CT), emergency temperature (ET), and critical temperature (TCR). From the experimental results, the optimal conditions to avoid violent runaway reactions during the storage and transportation of TBPB were determined.     

Kinetic parameter estimation for decomposition of organic peroxides by means of DSC measurements

The thermal stability of organic peroxides (cumene hydroperoxide 80 wt% and dicumyl peroxide) was studied by means of calorimetric measurement (DSC, TA Q1000) in an isotherm mode and a dynamic mode. Analysis of power profiles released in the isothermal mode was combined with the analysis of the decomposed compounds by a gas chromatograph/mass spectrometer (GC/MS) to determine the reaction mechanisms corresponding to each of the two reactions. In this work, a methodology for estimating kinetic parameters was based on the comparison of the power profile (dynamic mode) given by the model to that obtained experimentally by changing the parameters values. Parameter estimation is achieved using the mixed estimation method where a genetic algorithm is combined with a locally convergent method.     

聚碳酸酯/ABS/蒙脱土纳米复合材料的热重动力学分析

利用直接熔融插层技术制备聚碳酸酯/ABS聚合物合金/蒙脱土纳米复合材料.用热重分析法(TGA)研究了聚合物合金和纳米复合材料的热氧化降解行为.分别采用了无模式函数法(model-freemethod)和多元非线性回归法(multivariate nonlinearregression method)进行动力学评价.由此确定了整个降解过程的表观动力学参数.研究结果表明聚碳酸酯/ABS/蒙脱土纳米复合材料具有较高的热稳定性和阻燃性.两种材料的热氧化降解模型是一个两步分解过程.     

Thermal runaway reaction for highly exothermic material in safe storage temperature

Highly exothermic materials have caused many serious accidents involving storage and transportation, due to being thermally reactive. The safe storage and management of these materials is still a critical problem in many countries. Our aim was to study the thermal hazard of thermal reactive materials, such as a propellant, by employing differential scanning calorimetry (DSC) non-isothermal tests and isothermal tests, and then comparing the kinetic parameters by isothermal and non-isothermal of kinetics. The chosen approach was to obtain reliable thermal decomposition by a safe and effective method, which acquired the kinetic and safety parameters of storage conditions that could be applied as highly exothermic materials' reduction of loss prevention and energy potential for safer design during storage transport and processing operations.     

Thermal kinetics analysis of polymerization reaction of styrene-ethylbenzene system

To explore the reaction thermodynamics of a styrene-ethylbenzene mixed system, a differential scanning calorimetry (DSC) analysis was performed on the mixed system with styrene: ethylbenzene mass ratios of 1:0, 4:1, 3:2, and 2:3 at heating rates of 2.5, 5, 7.5, and 10 K/min. The activation energy of the mixed reaction system was calculated using the model-free Kissinger kinetic method, to determine a mixed system of relative stability mixing proportion. The thermodynamic parameters of the styrene-ethylbenzene mixture system at the optimal ratio were obtained using an adiabatic accelerating calorimeter. Further, dynamic thermal parameters such as the activation energy of the hybrid system, pre-exponential factor and order of reaction, TMR, TMRad, and T_D24 were calculated.     

Thermal hazard analysis of 1-((cyano-1-methylethyl) azo) formamide and effect of incompatible substances on its thermal decomposition

1-((cyano-1-methylethyl) azo) formamide (CABN) is an azo compound that exhibits high thermal sensitivity and self-reactivity. Because of incorrect operation, incompatible substances and other dangerous conditions, thermal explosion accidents may occur during the manufacturing, storage, and transportation of CABN. The pyrolysis characteristics of CABN and its mixture for various heating rates were assessed using differential scanning calorimetry. The results showed that incompatible substances increased the risk of CABN. Moreover, the thermal runaway of CABN under an adiabatic condition was studied using an adiabatic rate calorimeter to obtain the parameters under adiabatic condition. Based on the experimental data, the kinetic parameters of CABN and its mixtures were obtained. In addition, a thermal decomposition kinetic model of CABN was created using Thermal Safety Series. All experiments have shown that the conditions and parameters of CABN must be strictly controlled.     

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, CuBr_2, and FeBr₃ on the thermal decomposition of TBPTMH were investigated. Adiabatic kinetic analysis was performed and the apparent activation energy (E_a) was calculated by thermodynamic analysis. Time to maximum rise under adiabatic conditions (TMR_ad) 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.     

含能材料CL-20的热安全性测试分析

CL-20是一种高能量、高性能的炸药。为了研究CL-20的热分解性能,分别采用DSC-TG、DSC-TG-QMS联用系统和高压型差示扫描量热仪(DSC 204 HP)对CL-20的热安全性进行了测试分析,并计算了CL-20的热力学参数和动力学参数。结果表明,CL-20固体炸药在不同升温速率下的TG曲线基本相似,都只有一个台阶。在升温速率为10 K/min时,CL-20在放热峰温处的活化焓、活化熵和活化自由能分别是177.26 k J/mol、52.61 J/(K·mol)和149.7 kJ/mol。CL-20热分解后的气体产物主要有NO、CO、CO_2和H_2O,离子流强度约为10-9A,其中H_2O的离子流强度最大。不同压力时CL-20热分解的过程不同,在压力高的情况下CL-20分解放热更多,反应过程越剧烈,热安全性越差。与常压下相比DSC放热峰值温度降低。     

Kinetic mechanism and effects of molecular structure on thermal hazards of azo compounds

In this paper, the kinetic mechanism of AIBN, AMBN, and ABVN was proposed, and the effect of molecular structure on their thermal hazards based on the kinetic mechanism was investigated. Calculated by non-isothermal DSC datum, the kinetic mechanism of AIBN, AMBN, and ABVN is revealed by the linear relationship between the integrated form of mechanical function and reaction time. The results indicate that the thermal decomposition process is controlled by the Johnson-Mehl-Avrami equation. Based on the determination of kinetic mechanism function, the reaction rate constants at various heating rates are directly calculated, and the intercept of the best fitting straight line of reaction rate constants with heating rate is approximately equal to the reaction rate constant under isothermal conditions. Besides, theoretical values obtained by multiplying kinetic mechanism function by reaction rate are well consistent with the experimental values, suggesting that the kinetic mechanism obtained is credible. Bond Dissociation Energies (BDE) calculated by quantum chemical equations are employed to evaluate the thermodynamics stability of AIBN, AMBN, and ABVN. Depending on similar molecular structures, the influence of differentiated group structure on the thermodynamic stability represented by BDE and heat release and the kinetic stability characterized by reaction rate constant were revealed. Finally, the results demonstrate that the thermal hazard increases as the volume of substituent group and molecular weight.     

Development of an advanced nanocalorimetry system for material characterization

Calorimetric techniques, such as Differential Scanning Calorimeter (DSC), are widely used to characterize energetic materials. The conventional DSC is a well-established tool but is limited to a macroscopic sample. A key drawback of conventional macroscale DSC technology is the large thermal inertia of the calorimetric cell and its associated hardware for smaller sample size. The conventional technology can impose severe limitations in cases where only minute sample quantities are available for testing (e.g. forensics, detection of trace explosives, process or product development).A microreactor based calorimeter is being developed to obtain accurate measurements with smaller sample sizes. Because these systems incorporate a very small thermal mass and use reagent quantities in the nanogram/nanoliter range, rapid and uniform heating and cooing can be achieved while maintaining a high level of temperature homogeneity. These miniaturized nanocalorimeters can offer enhanced sensing capabilities in an inexpensive portable format so that measurements can be made directly in the settings where they are needed.This paper discusses the design and fabrication of the nanocalorimeter device, as well as interface with a modular thermal control system. With the proposed advanced device, a calorimetric analysis can be performed in a few minutes utilizing a minute sample. Therefore, such a nanocalorimeter can be effectively employed for rapid screening of energetic materials at relatively low cost.     

Removal of a cationic bisbiguanide using Functionalized Activated Carbons (FACs)

Functionalized Granular Activated Carbons (FACs) are used as adsorbents for treating pharmaceutical wastewaters containing Chlorhexidine Gluconate. Chemical modifications of Granular Activated Carbons (GACs) using functionalizing agents like HCl and HF produce FACs. The adsorption capacity of each of FAC-HCl and FAC-HF is found to be higher than GAC. The modelled maximum adsorption capacity for FAC-HCl is 1.02 g/g of adsorbent, 3.49 g/g of adsorbent for FAC-HF and 0.0682 g/g of adsorbent for GAC. This is mainly due to the additional chemisorptions by surface complexation at the functionalized surface sites of the modified GACs. This is also supported by the well-known pseudo-second-order kinetic model. Formation of surface complexes with the functional groups and weakly polar Chlorhexidine Gluconate is well supported by the physical characterization using Energy dispersive X-ray spectroscopy (EDAX), Brunner–Emmett–Teller (BET) test and Fourier Transform Infrared spectroscopy (FTIR) analysis after adsorption. The adsorption capacity of GAC and the FACs increases in the order of FAC-HF > FAC-HCl > GAC conforming to the proportion of the total acidity of the carbon surfaces. Intra-particle diffusion is not the sole rate-controlling factor. An agreement to pseudo-second-order kinetic model, Elovich kinetic model and Boyd's film diffusion model proves that chemisorption is the rate-controlling parameter in this adsorption study.     

KFR-2特种饰面型防火涂料的热解动力学分析

利用梅特勒TA4000,25-TC15型热分析仪对KFR-2特种饰面型防火涂料和普通乳胶漆涂料进行了TG和DSC分析,研究了KFR-2特种饰面型防火涂料和普通乳胶漆涂料的降解过程.在分析动力学理论模型基础上,分析数据,确定了KFR-2特种饰面型防火涂料和普通乳胶漆涂料的热力学参数,活化能.通过分析比较得出,与普通乳胶漆相比,KFR-2特种饰面型防火涂料由于添加了阻燃成分,使活化能显著提高,热稳定性明显加强,体系耐热性能好,阻燃效果明显.