硝酸异辛酯热安定性的实验研究

使用加速量热仪(ARC)研究硝酸异辛酯(EHN)的热分解,得到热分解温度随时间的变化曲线,自放热速率、分解压力随温度的变化曲线以及分解压力随升温速率的变化曲线。分析在绝热条件下硝酸异辛酯的热分解反应动力学和热分解过程,计算表观活化能、指前因子和反应热等参数。根据绝热热分解的起始温度和反应热数据,给出硝酸异辛酯在反应危险度等级中的分类,并计算在75℃时的反应风险指数。     

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.     

Thermal research on the uncontrolled behavior of styrene bulk polymerization

Thermal runaway can occur during the styrene bulk polymerization process because of easily formed local hotspots resulting from the high viscosity of reactants and the difficulty of heat dissipation. To obtain the thermal hazard characteristics, the polymerization behavior of styrene was investigated using differential scanning calorimetry (DSC) at a scanning rate of β = 2 °C/min. Experimental results showed that the exothermic peaks obtained for heat initiation were different from those obtained when initiator was added. The exothermic peak changed from one to two after the initiator was added. The exothermic onset temperature (T₀) was also reduced. Phi-tech II was utilized to study the bulk polymerization of styrene in an adiabatic environment. The adiabatic temperature rise (ΔT_ad), starting temperature of uncontrolled polymerization (T_star), maximum temperature (T_end), and heat of polymerization (ΔH) under different conditions were acquired. When the dose of the additive was increased, the starting temperature of uncontrolled polymerization (T_star) decreased and the adiabatic temperature rise (ΔT_ad) increased gradually. Severity grading was performed based on the severity evaluation criteria of runaway reaction. The results can help designers decide whether it is necessary to take certain measures to reduce risk.     

Thermal hazard assessment for synthesis of 3-methylpyridine-N-oxide

The exothermic oxidation of 3-methylpyridine with hydrogen peroxide was analyzed by Reaction Calorimeter (RC1e) in semi-batch operation. Heat releasing rate and heat conversion were studied at different operating conditions, such as reaction temperature, feeding rate, the amount of catalyst and so on. The thermal hazard assessment of the oxidation was derived from the calorimetric data, such as adiabatic temperature rise (ΔT_ad) and the maximum temperature of synthesis reaction (MTSR) in out of control conditions. Along with thermal decomposition of the product, the possibility of secondary decomposition under runaway conditions was analyzed by time to maximum rate (TMR_ad). Also, risk matrix was used to assess the risk of the reaction. Results indicated that with the increase of the reaction temperature, the reaction heat release rate increased, while reaction time and exotherm decreased. With the increase of feeding time, heat releasing rate decreased, but reaction time and exotherm increased. With the amount of the catalyst increased, heat releasing rate increased, reaction time decreased and exothermic heat increased. The risk matrix showed that when the reaction temperature was 70 °C, feeding time was 1 h, and the amount of catalyst was 10 g and 15 g, respectively, the reaction risk was high and must be reduced.     

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.     

Diphenylmethane diisocyanate self-polymerization: Thermal hazard evaluation and proof of runaway reaction in gram scale

Thermal analysis by differential scanning calorimetry and thermogravimetric/differential thermal analysis mass spectrometry, adiabatic calorimetry, a gram-scale heating test, and infrared spectroscopy were performed to evaluate the thermal hazards of diphenylmethane diisocyanate (MDI) and prove the occurrence of a runaway reaction. The self-polymerization of MDI was found to occur at about 340 °C under rapid heating conditions. Carbon dioxide was eliminated and heat was generated to allow polymerization. Under adiabatic and closed conditions, the runaway reaction of MDI can begin at least from 220 °C. Besides it is highly probable that the runaway reaction of MDI can begin from a lower temperature in an actual process scale. More heat was generated than in the previous case and the pressure rose rapidly. A closed 2-mm-thick glass vessel exploded because of the runaway reaction of MDI even if the temperature was lower than 300 °C. Therefore, MDI could cause fatal runaway reactions below 300 °C, where MDI had been assumed to self-polymerize by eliminating carbon dioxide previously.     

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 T_ad and TMR_ad suggests reducing thermal instability. This study on styphnic acid's thermal risks and safe storage and transit during analytical applications is beneficial.     

2-氨基-2,3-二甲基丁酰胺氧化合成热危险性研究

为研究2-氨基-23,-二甲基丁酰胺氧化合成的热危险性,采用差示扫描量热仪(DSC)测试2-氨基-2,3-二甲基丁腈和2-氨基-2,3-二甲基丁酰胺的热分解情况,采用反应量热仪(RC1)研究反应温度、双氧水滴加速度和氢氧化钠用量对反应的影响。研究结果显示,2-氨基-2,3-二甲基丁腈吸热热分解温度为149.5℃2,-氨基-2,3-二甲基丁酰胺表现为吸热和放热2段分解过程,吸热和放热分解温度分别为234.4℃和456℃。反应放热速率主要为加料控制,但是,存在一定的热累积。热失控体系最高温度(MTSR)低于2-氨基-23,-二甲基丁腈和2-氨基-23,-二甲基丁酰胺的分解温度,高于体系沸腾温度,在热失控的条件下,反应体系容易导致冲料危险;在优惠的工艺条件范围内,提高反应温度,延长滴加时间,可降低反应的MTSR,提高热转化率和反应安全性。     

Research on thermal decomposition characteristics of H foaming agent with different moisture contents

N, N-Dinitroso pentamethylene tetramine, also known as H foaming agent, is a self-reactive chemical substance commonly used in the rubber industry. Decomposition, explosion and combustion may be caused by the presence of fire or high temperature. As a high-risk chemical that is strictly regulated in China, H foaming agent has ever triggered multiple accidents. During the study of the decomposition thermal process of H foaming agent, it was found that the presence of moisture content at different levels had a significant effect on its thermal stability. The thermal characteristics of H foaming agent under different moisture contents was studied through the test means such as adiabatic calorimetry and high-pressure differential scanning calorimetry. Through isothermal calorimetry experiment, it was found that the decomposition of H foaming agent had obvious auto-catalytic characteristics. In the moisture content within the range of 0–40%, with the increase of moisture content, the initial exothermic temperature T_onset of the mixture system of H foaming agent and water decreased, while the time from initial heat release to rapid temperature rise of the reaction system (induction period) was gradually prolonged, and the temperature increment of the reaction system was increased gradually. As the proportion of moisture content in the system increased, the adiabatic temperature rise ΔT_ad of the mixture system of H foaming agent and water gradually decreased, meanwhile the time to maximum rate under adiabatic condition (TMR_ad) gradually decreased. The research results have guiding significance for finding the reasonable moisture content of H foaming agent in the drying process and determining the upper temperature limit during storage and transportation.     

Hazard evaluation for chlorination and amination reactions of fluorocytosine production process

Reaction thermal runaway is one of the most important reasons leading to chemical accidents. With the rapid development of the chemical industry in the world, especially the fine chemical industry, various safety accidents also occur frequently. Therefore, it is necessary to study the exothermic behavior of the reaction process. In this study, reaction calorimeter was used to study the exothermic phenomena during the chlorination reaction and amination reaction. Differential scanning calorimetry was performed on the reactants, and thermogravimetric experiments were performed on the products. In addition, adiabatic experiment was performed to study the thermal runaway behavior of amination products under adiabatic conditions. The results showed that the target reactions generated a large amount of heat in the initial stage. The maximum temperature of amination reaction is higher than the initial decomposition temperature of the amination product under adiabatic condition. The pyrolysis of amination product was divided into three stages. The product had a high apparent activation energy at the beginning of decomposition, and the apparent activation energy decreased as the decomposition progressed.     

绿色技术评价磺化反应过程热危险性

反应量热仪RC1研究磺化反应过程中热危险性具有评价路线简单、易于操作、过程绿色环保等优势,近年来逐渐成为研究的热点.磺化反应过程中由于工艺的不同,不同磺化反应过程的热危险性也具有很大的差别.通过反应量热仪RC1、差示扫描量热DSC、绝热加速量热仪ARC对10种不同工艺的磺化反应过程的热危险进行了深入的研究,对企业实践生...     

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 risk analysis of cumene hydroperoxide in the presence of alkaline catalysts

Many studies have been performed to clarify the basic thermal runaway hazards and kinetics of cumene hydroperoxide (CHP) decomposition. However, materials that are incompatible with CHP have not been clearly identified. Alkaline solutions have been used as a catalyst to form dimethylphenyl carbinol (DMPC) and dicumyl peroxide (DCPO); however, these solutions also affect the reaction and storage temperature of CHP. In this study, thermal calorimeters, differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2), were used to compare the effects of various bases on the decomposition of CHP in cumene. Specifically, the exothermic onset temperature, change in pressure over time, self-heating rate and heat of decomposition were evaluated. Moreover, to appraise the degree of hazard associated with the use of CHP, the compatibility of CHP with various substances was analyzed, and a risk matrix for thermal runaway reactions was obtained. The results of the present study could be used to design safety procedures for the production of CHP and its derivatives.     

The application of kinetics based simulation method in thermal risk prediction of coal

Coal spontaneous combustion is one of the major natural disasters faced in coal mines. The accurate prediction of the thermal risk of coal is of great importance. However, there isn't a widely accepted approach to get the oxidation process of coal that under adiabatic condition or in a specific environment under mine at present. To demonstrate whether the advanced kinetics simulation method could be employed to obtain the accurate oxidation process of coal for determining the coal's thermal risk in the mine design phase and mining phase, DSC experiments were conducted by C80 micro-calorimeter to get the heat behavior of coal, based on which the kinetic parameters can be solved and the oxidation process of coal can be predicted.The results showed that the kinetics based simulation method was successfully used to predict the adiabatic temperature rise process of coal for risk prediction. The deviation between the predicted curve and tested curve that obtained by adiabatic test is small enough to be accepted. Kinetics based simulation method is a promising candidate, instead of adiabatic test, to assess the propensity of coal to spontaneous combustion, which can play an important role in the design phase of the mine and mining area. Moreover, through establishing the heat balance equation of residual coal and with the aid of kinetics based simulation method, the oxidation process of coal that in the suffocation zone of the gob was also accurately predicted. According to the index t₇₀ (the time required for coal to reach 70 °C) and v_min (the lower limit of the advancing speed of the working face) obtained from the predicted curve, the thermal risk of coal was predicted to guide the further adjustment of the advancing speed of the working face, the amount of the injected mud and the determination that whether to add other fire prevention measures. Kinetics based simulation method, be of great practical importance in risk prediction of coal that in the gob, can be also used as a convenient tool to guide the safe production in the actual mining process.     

Comparisons of TGA and DSC approaches to evaluate nitrocellulose thermal degradation energy and stabilizer efficiencies

This study investigated the thermal degradation energy (activation energy, E_a) for nitrocellulose (NC) with low nitrogen content of 11.71 mass%, so-called NC3, by using two different kinds of thermal analysis instruments: thermogravimetric analyzer (TGA) and differential scanning calorimetry (DSC). A comparison of E_a for various nitrogen content NC samples at two scanning rates (5 and 10 °C min^?1) tested by TGA and DSC is also discussed in this paper. Meanwhile, our aim was to analyze the anti-degradation of E_a for NC with high nitrogen content, as so-called NC1. Thermal stability for NC1 with diphenylamine (DPA) was tested via DSC with 10 DPA concentrations in weights of 0, 0.25, 0.50, 0.75, 1.0, 1.25, 1.50, 1.75, 2.0, and 3.0 mass%. Experimental results indicated that E_a of NC3s was 319.91 kJ mol^?1. Moreover, that while dosing DPA into NC1 the best recipe could be employed to avoid any violent NC1 runaway and also can be used to distinguish the differences of thermal decomposition E_a between NC with different nitrogen contents. This study established a fast and efficient procedure for thermal decomposition properties of NC, and could be applied as an intrinsically safer design during relevant operations.     

Reaction mechanism and process safety assessment of acid-catalyzed synthesis of tert-butyl peracetate

Esterification during the synthesis of tert-butyl peracetate (TBPA) is highly exothermic. Since peroxides (tert-butyl hydroperoxide TBHP and TBPA) are intrinsically thermosensitive, this synthesis process is potentially dangerous. In this work, the exothermic process and mechanism of TBPA synthesis using acetic anhydride (Ac₂O) and TBHP under the catalysis of sulphuric acid (H₂SO₄) were clarified by calorimetry, infrared spectroscopy, and high-performance liquid chromatography. To substantially alleviate the thermal risk of the reaction, and to feasibly select appropriate synthesis conditions for ensuring the process safety of the synthesized products, several sets of isothermal and isoperibol experiments were performed using calorimetry. The intermediates formed and concentration changes during the reaction were monitored using in-situ Fourier-transform infrared spectroscopy. Differential scanning calorimetry and adiabatic calorimetry were used to assess the thermal hazard of the materials during the synthesis process. The reaction mechanism was verified using density functional theory calculations. The results revealed that a controlled increase in exothermicity could be achieved by adding aqueous TBHP to Ac₂O in semi-batch experiments in isothermal mode, and accordingly, the highest yield was 95.71%. Experiments combined with theoretical calculations revealed that the primary exothermic event was the TBPA formation reaction, and the removal of a large amount of water from TBHP prior to this is favourable for the reaction. The criticality classes of this reaction were of Grade 2.     

Thermal hazard accident investigation of hydrogen peroxide mixing with propanone employing calorimetric approaches

Hydrogen peroxide (H₂O₂), historically, due to its broad applications in the chemical industries, has caused many serious fires and explosions around the world. Its thermal hazards may also be incurred by an incompatible reaction with other chemicals, and a runaway reaction may be induced in the last stage. This study applied thermal analytical methods to explore the H₂O₂ leading to these accidents by incompatibility and to discuss what might be formed by the upset situations. Thermal hazard analysis contained a solvent, propanone (CH₃COCH₃, so-called acetone), which was deliberately selected to mix with H₂O₂ for investigating the degree of thermal hazard. Differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2) were employed to evaluate the thermal hazard of H₂O₂. The results indicated that H₂O₂ is highly hazardous while mixed with propanone, as a potential contaminant. The time to maximum rate (TMR) was used as emergency response time in the chemical industries. Therefore, TMR of H₂O₂ was calculated to be 70 min for runaway reaction (after T₀) and TMR of H₂O₂/propanone was discovered to be 27 min only. Fire and explosion hazards could be successfully lessened if the safety-related data are properly imbedded into manufacturing processes.     

交联剂TAIC反应风险评估分析

利用全自动反应量热仪和绝热加速量热仪等相关实验仪器检测出TAIC(三烯丙基异氰尿酸酯)合成反应的反应热、比热容及热稳定性等数据,依据绝热温升、工艺温度、技术最高温度、最大反应速率到达时间及失控体系可能达到的最高温度这5个温度参数按照评估标准从分解热、严重度、可能性、矩阵、工艺危险度这5个方面分别进行评估。通过对热参数及实验过程进行分析提出降低工艺危险等级的工艺优化方法。根据最终评估结果对TAIC生产装置的安全性进行评价,提出相应的整改措施及建议。     

Evaluating time to maximum rate (TMR) and self-accelerating decomposition temperature (SADT) of self-polymerizing vinyl acetate monomer

Vinyl acetate monomer (VAM) is widely used as a chemical intermediate producing a variety of copolymer products. Besides, VAM has the tendency to readily decompose into free radicals and ions that initiates the self-sustaining polymerization reaction. The non-isothermal experiments of VAM were performed using differential scanning calorimetry (DSC), and the calculations of the kinetic parameters from temperature-programmed DSC curves have been evaluated by the isoconversional method. The thermal analysis of VAM was proceeded using the advanced thermal analysis software (AKTS) to figure out the time to maximum rate (TMR) and self-accelerating decomposition temperature (SADT) for a proactive safety design of VAM. Subsequently, the kinetic model is used to predict the potential thermal runaway in the VAM-PVAc polymerizing process.