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.     

Thermal safety assessment for solid organic peroxides

The thermal hazards of dicumyl peroxide (DCP) and benzoyl peroxide (BPO), self-reactive chemicals are identified and characterized using high-pressuredifferential scanning calorimeter, and simultaneous thermogravimetric analyzer, a C80 micro-calorimeter is used. The apparent exothermic onset temperature of DCP is found to be between the range of 112–122 °C for different heating rates in DSC tests. There are two coupled peaks of BPO around 105 °C at both the heating rates of 4.0 and 8.0 °C/min while no endothermic peak showed at lower heating rates. Furthermore, another endothermic peak appears immediately after the exothermic peak at about 211 °C of DCP under high-pressure conditions. For BPO, the endothermic peak before the exothermic peak disappears as the pressure increases to 1.0 and 1.5 MPa. The average values of apparent activation energy calculated by Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose methods during the conversion rate between 15 and 75% of DCP are 80.69 and 74.05 kJ/mol, and that of BPO are 119.96 and 112.93 kJ/mol, respectively. According to the isothermal tests, the thermal decomposition of DCP behaviors is an n-th order reaction while BPO conforms to the laws of autocatalytic reaction.     

自反应性化学物质的热危险性评价方法

笔者进行的研究工作 ,给出了利用C80微量量热仪所测得的自反应性化学物质的热流速曲线 ,从而求解该物质的化学反应动力学参数 ,以及在Semenov模型下求解其自加速分解温度SADT(Self AcceleratingDecompositionTemperature)的方法 ,并将一些有机过氧化物、氧化剂和可燃剂的混合物的自加速分解温度的推算结果与实测值进行了比较。实验证明 ,该推算方法结论准确 ,是一种安全、简便、实用的反应性化学物质热危险性的评价方法     

Validation of the UN criteria for the uncooled sea transport of liquid organic peroxides: Full-scale test and modeling

In the years 1987 and 1988 TNO and Akzo Nobel investigated the thermal safety of non-temperature-controlled sea transport of organic peroxides, by modeling and experimenting on several scales. A full-scale test was organised in the summer of 1989, in co-operation with the former Nedlloyd company, in which a sea container with palletised packages, filled with soybean oil as inert liquid and fully equipped with temperature measuring equipment, was transported from Rotterdam, The Netherlands, to Beira, Mozambique, and back. The trip took 2 months.To answer questions stated by the workgroup International Group of Experts on the Explosion Risk of Unstable Substances—subgroup on Energetic and Oxidising Substance (IGUS-EOS) during its meeting in Washington, DC, USA, April 2006, the original data of the sea-container trip were reviewed and applied in a new mathematical model of the sea-container filled with packages, and traveling through tropical sea areas.Analysis of the data from the full-scale test led to defining a worst combination of adverse temperature conditions: constant dead sailing of the wind (wind direction and speed equal to that of the ship), and sunny weather 12 h/day and a mean ambient temperature of 30 °C during 28 days.The effect of sunny weather was put into the model by assigning 24 h averaged excess temperatures to the sun-exposed surfaces. New simulations showed no runaway for the sea container, if filled with an organic peroxide having an self-accelerating decomposition temperature (SADT) of exactly 55 °C.The exaggerated worst case with an improbable mean ambient temperature of 33 °C also does not lead to a runaway.Therefore, the UN criteria for temperature control for organic peroxides are appropriate.     

过氧化甲乙酮的热危险性研究

为研究过氧化甲乙酮(MEKPO)在运输与储存中的热危险性,利用差示扫描量热仪(DSC)对质量分数为52%的MEKPO溶液(以2,2,4-三甲基-1,3-戊二醇二异丁酸酯为溶剂)进行测试,得到其起始分解温度T0约为40℃,比放热量ΔH约为1.24 kJ/g。运用加速量热仪(ARC)对3种MEKPO溶液(40%,45%和52%)及MEKPO纯品(化学纯)在绝热条件下进行了热分解测试,并在此基础上,借助Semenov热爆炸模型,计算得到上述样品在50 kg包件下的自加速分解温度(TSADT)分别为65.64,63.72,55.88和51.17℃。研究结果表明,加入稀释稳定剂是降低MEKPO热危险性的有效途径,且MEKPO混合物中其质量分数越大,其危险性越高。     

Mixing hazard evaluation of organic peroxides with other chemicals

Organic peroxides (POs) have been widely used in chemical industries as initiators of polymerization, hardening or bridge formation agents, and they are known for its self-reactive and also mixing hazard characteristics when mixed with other chemicals such as acids and alkalis. It is the purpose of this investigation to propose a simple but useful evaluation flow of mixing hazards of POs with other chemicals using conventional experimental techniques such as a glass test tube test, Dewar vessel test and DSC is proposed. 7 kinds of POs (DEPD, THP, TBEH, TBTC, MEKPO, DTBP, THHP) were mixed with sulfuric acids with various concentration, sodium hydroxide solutions, -iron(III) oxide and acrylonitrile (AN).

Based on the proposed evaluation flow the testing results were classified into 4 ranks due to the hazard criteria. Futhermore DEPD/acrylonitrile mixtures were investigated in more detail and the influences of the mixing ratio and the stirring speed were discussed.     

膨胀聚苯乙烯热分解动力学分析和寿命预测

针对既有聚苯乙烯泡沫类外墙外保温系统的防火问题,在空气和氮气气氛下对非阻燃和阻燃型膨胀聚苯乙烯泡沫进行了热重分析。样品由10℃/min、20℃/min、40℃/min和50℃/min四个升温速率从室温加热至800℃。热分解动力学参数由Flynn-Wall-Ozawa(FWO)等转化率方法和多参数非线性回归方法(multivariate non-linear re-gression method)计算,结果表明六溴环十二烷(HBCD)阻燃剂可一定程度上提高EPS的热稳定性。EPS在空气和氮气气氛下热解可认为是单步反应。非阻燃聚苯乙烯泡沫在空气和氮气气氛下的热解过程可由自催化n阶反应机理描述。阻燃EPS在空气气氛下的热解机理为自催化n阶反应,在氮气气氛下则为n阶反应机理。基于动力学参数和反应机理,对聚苯乙烯泡沫在不同温度下的寿命进行了预测。     

Thermal decomposition mechanism of 65% lysine sulfate powder and its thermal stability based on thermal analysis

Lysine is widely used in the fields of food, medicine and feed, which generally appears in the form of lysine sulfate or lysine hydrochloride dust because of the high instability of the free L-lysine. The L-lysine Sulfate is in high risk of decomposition, spontaneous ignition and even the dust explosion, because the control temperature in its production process is high up to 90 °C. Thus, the thermal behaviors and its thermal stability of 65% lysine sulfate are experimentally explored in Air and Nitrogen using the simultaneous TG-DSC measurements. Results show: (1) the decomposition of 65% lysine sulfate can be divided into three stages both in the atmospheres of air and nitrogen, and most of the weight loss occurred in the first two stages, which are related with the decarboxylation and deamination process. (2) The effects of atmosphere on the decomposition of 65% lysine sulfate mainly occur at the third stage. In this stage, the weight loss in nitrogen is only 14.2%, which is much lower than that in air (34.3%), which is related to the oxidative degradation at high temperature. Besides, the active energy is slightly increased in nitrogen compared to that in air. (3) The initial temperatures of the decomposition of the 65% lysine sulfate are 145 °C and 155 °C, for the air and nitrogen atmosphere, respectively, which are much lower than that (260 °C) of the pure lysine.     

Micro calorimeter study on the thermal stability of lithium-ion battery electrolytes

With the extensive applications of lithium-ion batteries, many batteries explosion accidents were reported. The thermal stability of lithium-ion battery electrolyte could substantially affect the safety of lithium-ion battery. The C80 micro calorimeter was used to study the thermal stability of several commonly used organic solvents and electrolytes. The samples were heated in argon atmosphere and air atmosphere, respectively. The chemical reaction kinetics was supposed to fit by an Arrhenius law, then the self-accelerating decomposition temperature was calculated. It is found that most of the samples are stable in argon atmosphere while decomposing in air atmosphere, and the single organic solvent is more stable than the electrolyte generally.     

Decomposition effects on the mass burning rate of organic peroxide pool fires

The mass burning rate of pool fires of organic peroxides do not vary appreciably with the pool size as have been observed for the hydrocarbons. Instead the decomposition temperature largely controls the same. The dependence of mass burning rate on the decomposition temperatures namely self-accelerating decomposition temperature (SADT) and extrapolated onset temperature measured by differential scanning calorimetry (DSC) for organic peroxide pool fires are identified and correlations are developed.     

4种硝酸酯热安定性的绝热试验研究

利用绝热加速量热仪(ARC)对硝酸正丙酯(NPN)、硝酸异丙酯(IPN)、太根(TEGDN)、敌根(DEGDN)4种硝酸酯的热稳定性进行了绝热试验研究,得到绝热放热曲线和热分解特征参数。分析了4种物质分解过程的特点,对测试结果进行了修正。计算得到动力学参数和自加速分解温度SADT,以此作为评估热安定性的判据。结果表明,4种硝酸酯在外界热作用下容易发生分解,反应速度较快,伴随明显的热效应和压力效应。4种硝酸酯的热安定性由好到差排序为:IPN、NPN、TEGDN、DEGDN。     

Numerical simulation of the thermal inertia of an adiabatic reaction calorimeter in reaction thermal safety process

Obtaining accurate thermal risk assessment parameters of chemical processes and substance properties is essential for improving the safety of chemical production and substance use and storage, and the adiabatic reaction calorimeter (ARC) has been employed by many researchers for this purpose. However, with the improvement and upgrading of the instrument, an examination of the factors that affect its detection accuracy is warranted. A simplified reaction model of the adiabatic thermal decomposition of tert-butyl peroxyacetate was constructed using computational fluid dynamics in which the adiabatic thermal decomposition kinetic model and fluid-solid coupling model were combined to simulate heat transfer. To verify the reliability of the parameters of the numerical calculation model, the effects of the sample cell's material, wall thickness, and mass were investigated in relation to the thermal inertia of the ARC. The results indicated that the thermal inertia of the system was lowest when the sample cell was composed of titanium. When the sample pool's composition is determined, the thermal inertia of the system can be reduced to a certain extent through an approximate increase in the sample mass. Finally, an analysis of the heat flow cloud diagram of the wall of sample pools made from different materials revealed that the thermal conductivity of titanium was high; this information can assist in controlling the adiabatic process.     

Catalytic decomposition of hydrogen peroxide in the presence of alkylpyridines: Runaway scenarios studies

A number of runaway scenarios of the excess of hydrogen peroxide used during the N-oxidation of alkylpyridines, under closed and open conditions, were examined. It was found that, in most cases, if the volume of the liquid hydrogen peroxide solution occupies more than 10% of the total volume of a closed system (e.g. reactor and vent line between reactor and blockage), the production of gases raises the pressure so quickly that evaporation is completely suppressed. Higher than 70% filling levels result in complete expansion of the liquid. The MTSR(t) of the system falls rapidly if the normal process temperature is high, but if a runaway occurs exactly at the end of dosing, MTST will be very high and secondary decompositions will rapidly develop. The results of this study are currently being used to critically assess the current approaches and further the study of inherently safer designs.     

偶氮二异丁腈热安全性分析与评估

为获得偶氮二异丁腈(AIBN)在各种热应力条件下的危险参数,通过简化的压力容器试验测试AIBN的热分解激烈性等级,采用差示扫描量热仪(DSC)和绝热量热仪(ARC)对AIBN的热分解过程进行研究,用动力学与热稳定性分析软件AKTS计算动力学参数在整个反应进程中的变化情况,并根据ARC测试结果推算自加速分解温度(TSADT)。结果表明:AIBN的热分解激烈性为Ⅱ类,易呈现爆炸特性;其初始分解温度和TSADT很低,分别约为78℃和61℃,且分解放热过程和熔融吸热过程同时发生。因此,在AIBN的生产、使用、贮存和运输等过程中应加强温度监控,并根据实际情况采取降温措施。     

二甲亚砜热稳定性的实验研究

采用先进的绝热加速量热仪为手段,对二甲亚砜的热稳定性进行了系统研究,其内容涉及纯二甲亚砜的热稳定性、加酸碱和硫化物等杂质后二甲亚砜的热稳定性,包括初始放热温度、温升速率、温度-压力等;通过修正试验数据,消除了热惰性因子的影响;得到了二甲亚砜的热稳定性特性。研究表明,在酸、碱存在时,二甲亚砜在室温下即可发生强烈的放热反应,导致二甲亚砜的分解温度提前。该实验研究结果,对二甲亚砜的安全生产工艺过程控制具有重要参考价值。     

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.     

Explosibility and thermal decomposition behavior of nitrile rubber dust in industrial processes

The formation of nitrile rubber (NBR) dust clouds during processing can lead to a potential dust explosion under certain conditions. However, the potential explosion hazard posed by NBR dust is usually overlooked by enterprises. In this paper, the explosive properties of NBR dust are investigated using a Hartmann tube, a G-G furnace, and a 20 L explosion chamber. The results showed that NBR dust could cause explosions severe enough to be classified as St-1. In addition, the thermal decomposition behavior of NBR dust under combustion conditions was investigated using a combination of thermogravimetric analysis coupled with Fourier transform infrared spectroscopy (TGA-FTIR). The results indicated that in the early stage, NBR dust mainly undergoes self-thermal decomposition to produce a large amount of combustible gas, which combines with oxygen to form a mixed gas and cause a gas-phase explosion. In addition, the participation of oxygen could lower the initial temperature of NBR dust thermal decomposition. As a result, decomposition occurred more quickly and a large amount of combustible gas was produced, thus expanding the range of dust explosions. Furthermore, these combustible gases exhibit varying degrees of toxicity, seriously affecting the life and health safety of relevant personnel. This work provides theoretical guidance for the development of safe procedures to prevent and address problems during NBR dust processing in enterprises.     

重结晶LLM-105的热危险性分析

为了研究重结晶前后LLM-105在敞开体系、绝热体系中的热分解特性,采用溶剂-非溶剂法制备了形状规则、缺陷更少的重结晶LLM-105。以差示扫描量热仪研究了LLM-105的非等温热分解行为,利用Friedman法得到了非等温热分解动力学参数及TD24。采用加速量热仪研究了LLM-105的绝热分解行为,计算了绝热分解动力学参数及SADT。结果表明,重结晶LLM-105的非等温热分解起始温度(升温速率为10℃/min)、绝热起始分解温度、绝热最大升温速率分别为353.12℃、277.19℃、77.39℃/min,未重结晶LLM-105的相应参数值分别为341.62℃、273.77℃、136.62℃/min。重结晶LLM-105的非等温热分解起始温度、绝热起始分解温度更高,绝热最大升温速率更小。结晶品质是LLM-105的热分解特性、热危险性的重要影响因素。重结晶LLM-105具有更好的热稳定性,绝热分解反应更温和。     

过氧化氢异丙苯热稳定性与热安全性研究

为研究过氧化氢异丙苯(CHP)的热稳定性和热安全性,利用C80微量量热仪对CHP在空气中的热分解进行试验研究。利用热分析技术研究CHP的热分解,得到了升温速率对CHP热分解的影响,CHP热分解的活化能,绝热条件下最大反应速率到达时间Tmrad和不同包装下的自加速分解温度。结果表明:随着升温速率的增加,CHP的起始放热温度和最大放热温度随之升高;CHP热分解的活化能范围为52～91 kJ/mol;Tmrad为1,8,24,50和100 h时对应的起始温度分别为118.08,75.41,55.83,44.83和34.52℃;CHP的储罐内径越大,其对应的自加速分解温度越低。