Time To Maximum Rate Research Articles

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.

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.

Thermal decomposition and thermal kinetic simulation of ammonium 3,3′-dinitrimino-5,5′-bis(1H-1,2,4-triazole)

Ammonium 3,3′-dinitrimino-5,5′-bis(1H-1,2,4-triazole) (ADNABT) was synthesized and characterized by IR spectroscopy, 1H/13C NMR and single-crystal X-ray diffraction. The thermal decomposition of ADNABT was investigated by thermogravimetry–differential thermal analysis (TG–DTA) and accelerating rate calorimeter (ARC). The kinetic parameters (activation energy, pre-exponential factor, mechanism functions) by DTA and ARC tests were simulated by Thermal Safety Software (TSS). The simulated results revealed that the exothermic decomposition of ADNABT under non-isothermal and adiabatic conditions all followed a full autocatalysis model. In order to ensure the safety of production, transportation and storage, several thermal hazard indicators such as time to maximum rate (TMR), reaction temperature at which TMR is 24 h (TD24), time to conversion limit and self-accelerating decomposition temperature (SADT) were also simulated by TSS on the kinetic model. The TD24 and SADT50 kg were calculated as 183.37 and 167.00 °C, respectively.

Thermal decomposition kinetics and thermal hazards simulation of sodium and rubidium 3,3′-dinitrimino-5,5′-bis(1H-1,2,4-triazole)

Sodium 3,3′-dinitrimino-5,5′-bis(1H-1,2,4-triazole) (Na2DNABT) and rubidium 3,3′-dinitrimino-5,5′-bis(1H-1,2,4-triazole) (Rb2DNABT) were synthesized and characterized by IR spectroscopy and 1H/13C NMR. Rb2DNABT was characterized by single-crystal X-ray diffraction. The thermal decomposition kinetics and thermal hazards of Na2DNABT and Rb2DNABT were investigated by difference scanning calorimeter (DSC) and accelerating rate calorimeter (ARC). The thermal decomposition kinetics (activation energy, pre-exponent, reaction model) were evaluated by Thermal Safety Software (TSS) on DSC and ARC tests. The activation energy of Na2DNABT and Rb2DNABT by DSC test was also calculated by Starink method, which consistent with the simulated activation energy by TSS. Time to maximum rate (TMR), reaction temperature at which TMR is 24 h (TD24) and time conversion limit (TCL) were simulated by TSS, too. The TD24 of Na2DNABT and Rb2DNABT were calculated as 215.86 and 141.95 °C, respectively, and their TCL at 200 °C was calculated as 24.00 and 4.56 h, respectively. Na2DNABT is a stable and safety compound compared with Rb2DNABT.

Mathematical methods for application of experimental adiabatic data – An update and extension

The paper represents some results of comparative analysis of the methods used for processing and interpreting data of adiabatic calorimetry as well as applying it to practical situations. Specifically two approaches are compared – approximate method based on evaluation of simplified kinetics and a more comprehensive, simulation-based method that utilizes the evaluation of more detailed kinetic models.The analysis is focused on two important types of data processing – correction of experimental results on thermal inertia (phi-factor correction) and estimation of adiabatic time to maximum rate (TMR).The most widely cited method for phi-factor correction is considered and its improvement is proposed to enable more precise prediction of the adiabatic time scale. A procedure for phi-factor correction of pressure response is also proposed. The limitations of this enhanced Fisher's method are discussed by comparison with simulation-based method. All the illustrative materials are based on real examples.As an example of application, the simplified method will be used to predict TMR and its limitations will be discussed.

Evaluation of thermal hazard for lauroyl peroxide by VSP2 and TAM III

When above certain temperature limits, lauroyl peroxide is an unstable material. If the thermal source cannot be properly governed during any stage in the preparation, manufacturing process, storage or transport, runaway reactions may inevitably be induced immediately. In this study, the influence of runaway reactions on its basic thermal characteristic was assessed by evaluating thermokinetic parameters, such as activation energy (Ea) and frequency factor (A) by thermal activity monitor III (TAM III). This was achieved under five isothermal conditions of 50, 60, 70, 80, and 90 °C. Vent sizing package 2 (VSP2) was employed to determine the maximum pressure (Pmax), maximum temperature (Tmax), maximum self-heating rate ((dT dt−1)max), maximum pressure rise rate ((dP dt−1)max), and isothermal time to maximum rate ((TMR)iso) under the worst case. Results of this study will be provided to relevant plants for adopting best practices in emergency response or accident control.

Isothermal and non-isothermal kinetic and safety parameter evaluation of tert-butyl(2-ethylhexyl)monoperoxy carbonate by differential scanning calorimetry

Tert-butyl(2-ethylhexyl)monoperoxy carbonate (TBEHC) 95 mass% is intrinsically a very unstable substance that can induce self-decomposition even under normal atmospheric condition. During storage, TBEHC 95mass% can release an enormous amount of heat if the temperature is higher than the recommended storage temperature, due to the self-accelerating reaction having been ignited. In this study, TBEHC 95mass% was tested by differential scanning calorimetry (DSC) under five heating rates (1, 2, 4, 6, and 8 °C/min) and four isothermal conditions (120, 125, 130, and 135 °C) to evaluate the basic kinetic and safety parameters of time to maximum rate (TMR), self-accelerating decomposition temperature (SADT), and temperature of no return (TNR). Under runaway reaction TBEHC 95 mass% releases a great quantity of heat. This study establishes an important guiding principle for related manufacturing processes worldwide.

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

Hydrogen peroxide (H 2O 2), 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 H 2O 2 leading to these accidents by incompatibility and to discuss what might be formed by the upset situations. Thermal hazard analysis contained a solvent, propanone (CH 3COCH 3, so-called acetone), which was deliberately selected to mix with H 2O 2 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 H 2O 2. The results indicated that H 2O 2 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 H 2O 2 was calculated to be 70 min for runaway reaction (after T 0) and TMR of H 2O 2/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.

Kinetic and safety parameters analysis for 1,1,-di-(tert-butylperoxy)-3,3,5-trimethylcyclohexane in isothermal and non-isothermal conditions

Over the past 30 years, the field of thermal analysis of organic peroxides has become an important issue in chemical engineering departments, safety departments, and in companies working with polymerization, petrifaction process, and so on. The contributions of thermal analysis to the evaluation and prediction of the runaway reactions have been important for decreasing or preventing a hazard, such as fire or explosion accident. This study was carried out using differential scanning calorimetry (DSC) to evaluate the kinetic and safety parameters in isothermal and non-isothermal conditions, for instance, temperature of no return ( T NR ), self accelerating decomposition temperature (SADT), time to maximum rate (TMR), activation energy ( E a ), frequency factor ( A), reaction order ( n), and reaction heat (Δ H), in terms of the hazardous material of 1,1,-di-(tert-butylperoxy)-3,3,5-trimethylcyclohexane (TMCH) 88 mass%. On the basis of this study, we demonstrated that TMCH 88 mass% must be well controlled in the manufacturing process due to the unstable structure of O–O, which releases a great quantity of heat, higher than 1300 J/g under decomposition. Results of this study could contribute to the relevant plants adopting TMCH 88 mass% in a process, in order to prevent a fire or explosion accident from happening.

Thermal hazard analyses of organic peroxides and inorganic peroxides by calorimetric approaches

Organic peroxides (OPs) and inorganic peroxides (IPs) are usually employed as an initiator for polymerization, a source of free radicals, a hardener, and a linking agent in low density polyethylene (LDPE), polyvinyl chloride (PVC), controlled-rheology polypropylene (CR-PP), and styrene industries. Worldwide, due to their unstably reactive natures, OPs and IPs have caused many serious thermal explosions and runaway reaction incidents. This study was conducted to elucidate its essentially hazardous characteristics. To analyze the runaway behavior of OPs and IPs in the traditional process, thermokinetic parameters including heat of decomposition (ΔH d ), exothermic onset temperature (T 0), self-accelerating decomposition temperature (SADT), time to maximum rate (TMR), critical temperature (T c ), etc., were measured by calorimetric approaches involving differential scanning calorimetry (DSC), vent sizing package 2 (VSP2), and calculation method. Safety and health handling information of hazardous materials and toxic substances is noted in material safety data sheets (MSDS) and was applied to analyze in process safety management (PSM) in the chemical industries, but MSDS are not providing important handling indicators concerning the SADT, TMR, T c , etc. In view of loss prevention, more useful indicators must be provided in the sheets or guide book.

Effects of stirring rate for thermal runaway reaction in cumene hydroperoxide manufacturing process using calorimetric techniques

Oxygen (O2) or air is widely applied globally to yield cumene hydroperoxide (CHP) in a cumene oxidation tower. In previous studies, CHP has been identified as a thermally hazardous chemical. This study was used to evaluate thermal hazard of CHP in cumene using differential scanning calorimetry and vent sizing package 2 (VSP2). Self-accelerating decomposition temperature (SADT), self-heating rate, exothermic onset temperature (T0), critical temperature (Tc), time to maximum rate (TMR), activation energy (Ea), etc., were employed to prevent and protect thermal runaway reaction and explosion in the manufacturing process and/or storage area. The reaction order (n) of CHP was evaluated to be 0.5 in this study. The Ea was determined to be 122 kJ mol−1 by VSP2. High volume of CHP with 0 rpm of stirring rate by VSP2 was more dangerous than a low one. Control of stirring rate should be a concern in process safety management program. In view of proactive loss prevention, inherently safer handling procedures and storage situations should be maintained in the chemical industries.

Further explanations of lauroyl peroxide runaway reaction by DSC tests and simulations

It is our honor and pleasure to discuss some phenomena of specific organic peroxide with Prof. M. Malow and Prof. K. D. Wehrstedt. The kinetic parameters of the thermal behavior of lauroyl peroxide (LPO) were detected by DSC under nonisothermal conditions. Kinetic models and algorithms for thermal analysis were invented by Kossoy, Akhmetshin, and their associates (2007) of the Thermal Safety Software (TSS) [1–6]. Inputting experimentally derived data of interest into TSS is a simple analytical process that can be used to estimate or predict the thermal hazard of organic peroxides and other energetically sensitive materials to achieve optimization in the safety approaches of chemical plants. In our laboratory, many applied cases [7–10] in the use of organic peroxides and energetic materials have already been studied using this method. For instance, from Tables 1 and 2, the kinetic parameters of the thermal behavior of LPO were tested by DSC in non-isothermal conditions (with heating rates of 1, 2, 4, and 10 C min) first. Then they were further simulated using TSS by nth order and autocatalytic reaction processes, respectively. In addition, the thermal hazard parameters of LPO, time to maximum rate (TMR), and a certain time to conversion limit (TCL) at heating rates of 1, 2, 4, and 10 C min by nth order and autocatalytic simulation were shown in Figs. 1 (for TMR) and 2 (for TCL). Under adiabatic condition, TMR is normally employed as a critical index of a temperature with an explosive accident potential once over by the surrounding temperature. According to Fig. 1, through simulation of a temperature of 70 C, the TMR value was about 3–5 min. Utilization of this data could enable an operator to know how much time would be available for emergency response in the event of a runaway reaction. LPO is solid organic peroxide, belonging to the group of quasi-autocatalytic reactions of thermal decomposition [11]. When LPO was stored under isothermal conditions, over a long time, an abrupt self-heating of the resultant liquid started. In essence, exothermic decomposition reactions can begin when the solid and liquid phases coexist on one container [12]. Another parameter for determining thermal stability, which is characterized by the time necessary to reach TCL, was necessary to determine the stability of materials under storage or transportation conditions. In our previous studies associated with the aforementioned kinetic-based simulation approach, three main steps were conducted: executing a necessary series of calorimetric experiments; building up the mathematical model of a reaction based on experimental data of DSC, incorporating the kinetic model into the model of processing; and achieving the practical target by applying mathematical simulations. In case of a package containing a solid with both internal heat losses from the surface are important [6]. Various vessel types with different material densities were chosen for simulation, like LPO in box is simulated by solid thermal explosion specifying boundary conditions of the first, second, and third type. Transport package sizes and boundary conditions, shown in Tables 3 and 4, were assumed to be uniform over each package’s surface. M.-L. You Department of General Education Center, Chienkuo Technology University, 1, Chieh-Shou N. Rd., Changhua 50094, Taiwan ROC

Effects of cumene hydroperoxide on phenol and acetone manufacturing by DSC and VSP2

Cumene hydroperoxide (CHP) being catalyzed by acid is one of the crucial processes for producing phenol and acetone globally. However, it is thermally unstable to the runaway reaction readily. In this study, various concentrations of phenol and acetone were added into CHP for determination of thermal hazards. Differential scanning calorimetry (DSC) tests were used to obtain the parameters of exothermic behaviors under dynamic screening. The parameters included exothermic onset temperature (T 0), heat of decomposition (ΔH d), and exothermic peak temperature (T p). Vent sizing package 2 (VSP2) was employed to receive the maximum pressure (P max), the maximum temperature (T max), the self-heating rate (dT/dt), maximum pressure rise rate ((dP/dt)max), and adiabatic time to maximum rate ((TMR)ad) under the worst case. Finally, a procedure for predicting thermal hazard data was developed. The results revealed that phenol and acetone sharply caused a exothermic reaction of CHP. As a result, phenol and acetone are important indicators that may cause a thermal hazard in the manufacturing process.

Thermal explosion analysis of methyl ethyl ketone peroxide by non-isothermal and isothermal calorimetric applications

In the past, process incidents attributed to organic peroxides (OPs) that involved near misses, over-pressures, runaway reactions, and thermal explosions occurred because of poor training, human error, incorrect kinetic assumptions, insufficient change management, and inadequate chemical knowledge in the manufacturing process. Calorimetric applications were employed broadly to test organic peroxides on a small-scale because of their thermal hazards, such as exothermic behavior and self-accelerating decomposition in the laboratory. In essence, methyl ethyl ketone peroxide (MEKPO) is highly reactive and exothermically unstable. In recent years, it has undergone many thermal explosions and runaway reaction incidents in the manufacturing process. Differential scanning calorimetry (DSC), vent sizing package 2 (VSP2), and thermal activity monitor (TAM) were employed to analyze thermokinetic parameters and safety index. The intent of the analyses was to facilitate the use of various auto-alarm equipments to detect over-pressure, over-temperature, and hazardous materials leaks for a wide spectrum of operations. Results indicated that MEKPO decomposition is detected at low temperatures (30–40 °C), and the rate of decomposition was shown to exponentially increase with temperature and pressure. Determining time to maximum rate (TMR), self-accelerating decomposition temperature (SADT), maximum temperature ( T max), exothermic onset temperature ( T 0), and heat of decomposition (Δ H d) was essential for identifying early-stage runaway reactions effectively for industries.

Runaway effects of nitric acid on methyl ethyl ketone peroxide by TAM III tests

Methyl ethyl ketone peroxide (MEKPO) is an unstable material above certain limits of temperature, decomposing into chain reactions by radicals. The influence of runaway reactions on this basic characteristic was assessed by evaluating kinetic parameters, such as activation energy (E a ), frequency factor (A), etc., by thermal activity monitor III (TAM III). This was done under three isothermal conditions of 70, 80, and 90 °C, with MEKPO 31 mass% combined with nitric acid (HNO3 6 N) and sodium nitrate (NaNO3 6 N). Nitric acid mixed with MEKPO gave the maximum heat of reaction (△H d ) and also induced serious reactions in the initial stage of exothermic process under the three isothermal temperatures. The time to maximum rate (TMR) also decreased when HNO3 was mixed with MEKPO. Thus, MEKPO combined with HNO3 6 N forms a very hazardous mixture. Results of this study will be provided to relevant plants for alerting their staff on adopting best practices in emergency response or accident control.

Thermal hazards evaluation of cumene hydroperoxide mixed with its derivatives

Over 90% of the cumene hydroperoxide (CHP) produced in the world is applied in the production of phenol and acetone. The additional applications were used as a catalyst, a curing agent, and as an initiator for polymerization. Many previous studies from open literature have verified and employed various aspects of the thermal decomposition and thermokinetics of CHP reactions. An isothermal microcalorimeter (thermal activity monitor III, TAM III), and a thermal dynamic calorimetry (differential scanning calorimetry, DSC) were used to resolve the exothermic behaviors, such as exothermic onset temperature (T0), heat power, heat of decomposition (ΔHd), self-heating rate, peak temperature of reaction system, time to maximum rate (TMR), etc. Furthermore, Fourier transform infrared (FT-IR) spectrometry was used to analyze the CHP products with its derivatives at 150 °C. This study will assess and validate the thermal hazards of CHP and incompatible reactions of CHP mixed with its derivatives, such as acetonphenone (AP), and dimethylphenyl carbinol (DMPC), that are essential to process safety design.

Thermal hazard evaluation for methyl ethyl ketone peroxide mixedwith inorganic acids

Methyl ethyl ketone peroxide (MEKPO) possesses complex structures which have caused many incidents involving fires or explosions by mixing with incompatible substances, external fires, and others. In this study, reactivities or incompatibilities of MEKPO with inorganic acids (HCl, HNO3, H3PO4 and H2SO4) were assessed by differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2). Parameters obtained by the above-mentioned devices could be readily employed to discuss the runaway reaction, such as onset temperature (T0), heat of reaction (ΔHd), time to maximum rate (TMR), maximum self heat rate (dT/dt)max, adiabatic temperature rise (ΔTad), maximum pressure of decomposition (Pmax) and so on.

Study of thermal decomposition of methyl ethyl ketone peroxide using DSC and simulation

Methyl ethyl ketone peroxide (MEKPO) is a typical organic peroxide with thermally unstable nature that has been broadly employed in the manufacturing process of acrylic resins, as a hardening agent for fiberglass-reinforced plastics, and as a curing agent for unsaturated polyester resins. The aim of this study was to identify the characteristics of MEKPO 31 wt.% while mixing with contaminants, such as H 2SO 4, HCl, and NaCl under runaway conditions. To acquire the thermal runaway data, DSC and a simulation were used for thermal analysis. The results showed that the thermal decomposition of MEKPO and MEKPO + H 2SO 4 follows two stages. The first one can be modeled by using an empirical nth order rate equation. The second stage can be modeled as autocatalytic. MEKPO + HCl and MEKPO + NaCl included two independent autocatalytic reactions. The decomposition of MEKPO in the presence of Cl − ions (added in MEKPO either in the form of HCl or NaCl) follows a significantly different path, an earlier decomposition “onset” temperature, higher amount of generated thermal power and smaller temperature of no return ( T NR) and time to maximum rate (TMR) values. Simulations based on experimental data indicated that the effect of H 2SO 4 was the most dangerous contaminant on MEKPO 31 wt.%. However, the impact of Cl ions was also important. It is therefore recommended that the means of fire fighting employed for this substance to be free of Cl −.

Thermal Stability of an Oligosaccharide: Autocatalytic Behavior

Many of the materials in the pharmaceutical industry can present hazards, and it is essential to have a good knowledge of the thermal stability of every material to be able to assess any risk. Not only raw material and final products must be studied but also reaction intermediates. In this way, a safety study of a Sanofi-Synthelabo process pointed out the thermal instability of an isolated intermediate from an oligosaccharide pharmaceutical active ingredient synthesis. This led to a detailed kinetic study to give suitable safety recommendations to industrials for handling and storage of this product. The differential scanning calorimetry (DSC) was the technique used to perform the study. Dynamic and isothermal analyses underlined the autocatalytic behavior of the product. Activation energy, time to maximum rate (TMR), and critical storage radius were evaluated, and to complete the study the compatibility with materials (glass, aluminum, and stainless steel) has also been tested.

Prediction and evaluation of the reactivity of self-reactive substances using microcalorimetries

To evaluate the thermal hazard of self-reactive substances in chemical processes, the time to maximum rate (TMR) of autocatalytic decomposition reaction of cumenehydroperoxide (CHP) was determined by calculations based on the results of isothermal measurement using DSC and heat conduction calorimeter. In addition, the factors affecting the calculated results were investigated. It was found that the TMR is affected by the catalytic action of the sample vessel metal. When this effect is taken into account in analyzing the experimental result, the predicted TMR shows a good agreement with the value determined using the adiabatic reaction calorimeter. The present study clarified that the proposed technique would enable the appropriate evaluation of thermal hazard of an autocatalytic reaction.