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Journal of Loss Prevention in the Process Industries 25 (2012) 202e208

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Journal of Loss Prevention in the Process Industries

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Effects of ferric oxide on decompositions of methyl ethyl ketone peroxide

Wei Menga,b, Yuan Lua, Victor H. Carreto-Vazqueza, Qingsheng Wangc,*, M. Sam Mannana,**

aMary Kay O’Connor Process Safety Center, Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX 77843-3122, USAbDepartment of Chemical Engineering, Tsinghua University, Beijing 100084, ChinacDepartment of Fire Protection and Safety, Oklahoma State University, Stillwater, OK 74078-8016, USA

a r t i c l e i n f o

Article history:Received 8 November 2010Received in revised form25 August 2011Accepted 29 August 2011

Keywords:MEKPOFerric oxideThermal stabilityAPTACRunaway reaction

* Corresponding author.** Corresponding author. Tel.: þ1 979 862 3985; fax

E-mail addresses: qingsheng.wang@okstate.edu (Q(M.S. Mannan).

0950-4230/$ e see front matter � 2011 Elsevier Ltd.doi:10.1016/j.jlp.2011.08.007

a b s t r a c t

Methyl ethyl ketone peroxide (MEKPO) is a widely used initiator for polymerization reaction and hardenerin glass-reinforced plastic. However, MEKPO is an unstable reactive chemical and has caused several seriousaccidents all over the world. This work studied the thermal stability of MEKPO in the presence of ferricoxide as the contaminant through calorimetric and kinetic studies. The calorimetry was performed usingAutomatic Pressure Tracking Adiabatic Calorimeter (APTAC) to identify the effects of ferric oxide (differentconcentration) on important reactive hazards such as onset temperature and pressure hazard. Kineticmodeling was then performed to study the kinetics of the runaway reaction and estimate important kineticparameters. The results indicate that in the low concentration range (<0.3%), ferric oxide has no significanteffect on the thermal stability of MEKPO. However, in the high and intermediate concentration range offerric oxide (i.e., 10%), the negative effect on the thermal stability of MEKPO was observed. This result isin agreement with the kinetic study result that the activation energy and frequency factor decreasedramatically in the high ferric oxide concentration range. The results provide necessary process safetyinformation for the handling of MEKPO and also technical basis for the further study in this area.

� 2011 Elsevier Ltd. All rights reserved.

1. Introduction

Methyl ethyl ketone peroxide (MEKPO) has been widely usedin the production of unsaturated polyester resins (Fu, Li, Koseki, &Mok, 2003). However, the weak oxygeneoxygen bond in theperoxide functional group can be easily broken into radicals andinitiate decomposition reaction. The runaway reaction may occur ifheat generated by decomposition reaction cannot be removed effi-ciently from the process. The runaway reaction can lead to dramaticincrease of temperature and pressure inside of process equipmentand therefore impose great risk to process.

Several severe accidents caused by MEKPO have been reported,which lead to fatalities, injuries and millions of dollars propertydamage. One of the most severe accident occurred in Taipei, Taiwanin 1979 due to improper storage operation. Another disasterhappened inTokyo, Japanwith 114 injuries and 19 fatalities. Some bigaccidents also occurred in Korea and China, such as the explosion inYosu, Korea in 2000 and those in China in 1993, 2001 and 2003 (Lin,Tseng,Wu, & Shu, 2008). The explosion in 1993 in China happened ina research institute in Shanxi province. In that incident, the initial

: þ1 979 845 6446.. Wang), mannan@tamu.edu

All rights reserved.

explosion happened research scientists were conducting experi-ments usingMEKPO,whichwas followed by the secondary explosionof 170 kg MEKPO stored in the laboratory, causing 4 fatalities and 44injuries. Considering continuing occurrence of incidents causedby MEKPO, there is an urgent need to achieve the comprehensiveunderstanding of the reactive hazards of MEKPO, which can helpdeveloping strategies for safe handling of MEKPO in process industryand adopting preventive and mitigate safety measures.

Multiple research works have been done to investigate reactivehazards associated with MEKPO. For example, early work by Yehet al. offers a general idea of thermal instability of this material (Yeh,Shu, & Duh, 2003). Then different contaminants, such as inorganicacid, alkyl, and salt, and apparatuses, such as DSC, ARC, VSP2, TAMIII, have been used to identify its characteristics (Chang, Shu, Duh, &Jehng, 2007; Duh, Hui wu, & Kao, 2008; Li, Koseki, Iwata, & Mok,2004; Tseng, Chang, Horng, Chang, & Shu, 2006; Tseng, Chang, Su,& Shu, 2007; Tseng & Shu, 2010; Tseng, Shu, Gupta, & Lin, 2007;Tseng, Shu, & Yu, 2005). Researchers also studied incompatibilityof MEKPO with organic contaminants, such as acetone (Lin et al.,2008). Efforts have also been done on the prediction of the reac-tive hazards for MEKPO and other organic peroxides (Lu, Ng, &Mannan, 2010). However, so far little work has been done on howFe2O3 affects the reactive hazards of MEKPO (Tseng et al., 2005).Since ferric oxide is the contaminant frequently encountered inindustrial processes, more work should be done regarding the

Fig. 1. (a) Comparison of onset temperature between MEKPO and MEKPO with lowconcentrations of contaminants. (b) Pressure profiles.

W. Meng et al. / Journal of Loss Prevention in the Process Industries 25 (2012) 202e208 203

incompatibility of MEKPO with different levels of ferric oxide in thereaction system.

The purpose of this work is to identify the effects of ferricoxide on reactive hazards of MEKPO at different concentrations. Inthis research, experimental investigation using APTAC was utilizedin conjunction with kinetic modeling as the research approach forrevealing the comprehensive understanding of the incompatibilityof MEKPO with industrial contaminant. The research results can beused to develop safer process conditions in the course of processdesign.

2. Experimental

2.1. Apparatus

The experiments were conducted in an APTAC. This calorimetercan track the pressure inside the test cell automatically, thereforeallows the usage of test cells with thinwalls and littlemass. Becauseof this function, the thermal inertia factor, namely the phi factor(4¼ (MsCsþMbCb)/MsCs, here M is the mass, C is the heat capacity,subscript s and b respectively stand for sample and bomb), can beas low as 1.1. The APTAC can be operated under the pressure up to2000 psi and the temperature up to 500 �C. It can track self-heatingrate up to 400 �C/min, and compensate pressure up to or evengreater than 10,000 psi/min. The APTAC has four heating modes(e.g., isothermal, temperature ramp, and heatewaitesearch). In thiswork, we used the heatewaitesearch (HWS) heating mode. In thismode, the sample is heated up in several steps and searching for anexotherm at each step. When an exotherm is detected, the APTACshifts to adiabatic mode automatically and tracks the reaction untilone of the shutdown criteria is met. A detailed APTAC descriptioncan be found elsewhere (Chippett, Ralbovsky, & Granville, 1998).

2.2. Materials

MEKPO of 35 wt% (diluted in 2,2,4-trimethyl-1,3-pentanedioldiisobutyrate) was purchased directly from the Aldrich Company.The measuring conditions of the experiments performed in thiswork are summarized in Table 1.

3. Results

3.1. Calorimetry study

The runaway reaction of MEKPO was investigated based ondifferent sets of calorimetry data. Different amounts of ferric oxidewere used as contaminant to quantitatively estimate its effect on thereactive hazards of MEKPO, among which only one concentrationwas done in a previous work (Tseng et al., 2005). Here we classifiedeight concentrations of contaminant Fe2O3 into three categories:low concentration (No. 3, No. 4, No. 5 and No. 6), intermediate

Table 1Measuring conditions of all experiments.

Samples Test no. MEKPO mass (g) Bomb m

MEKPO 1 8.13 57.61MEKPO 2 8.15 54.06MEKPO with 0.0024 g Fe2O3 3 8.18 57.61MEKPO with 0.0025 g Fe2O3 4 7.74 53.57MEKPO with 0.006 g Fe2O3 5 7.99 53.67MEKPO with 0.0234 g Fe2O3 6 7.99 53.17MEKPO with 0.08 g Fe2O3 7 7.85 53.08MEKPO with 0.4 g Fe2O3 8 7.92 54.65MEKPO with 0.79 g Fe2O3 9 7.78 52.99MEKPO with 1.56 g Fe2O3 10 7.95 52.99

concentration (No. 7 and No. 8) and high concentration (No. 9 andNo. 10). The temperature and pressure profiles for each category areshown in Figs. 1(a)e3(a), respectively.

Onset temperature is an important parameter studied inthis research, which indicates the thermal stability of MEKPO. Bycomparing the temperature profiles between the pure MEKPO andMEKPO with very low concentration of contaminant (w0.03 wt%)(Fig. 1(a)), an increase of about 11 �C in onset temperature wasobserved. This observation does not agree with the expectationthat Fe2O3 is a contaminant impairing the thermal stability ofMEKPO. However, when test was performed on MEKPOwith higherconcentration of Fe2O3 (around 2 or 10 times of the concentrationused in the first set of experiments), the onset temperature ofMEKPO sample is quite close to pure MEKPO, indicating that ferricoxide within this range has no observable effect on thermal stability

ass (g) Start temperature (�C) Vapor space (mL) F Factor

35 83.6 3.330 83.7 3.235 83.5 3.335 84.7 3.335 84.5 3.235 84.0 3.235 87.5 3.235 87.6 3.235 84.7 3.235 84.5 3.2

Fig. 2. (a) Comparison of onset temperature between MEKPO and MEKPO withintermediate concentrations of contaminant. (b) Pressure profiles.

Fig. 3. (a) Comparison of onset temperature between MEKPO and MEKPO with highconcentrations of contaminants. (b) Pressure profiles.

Fig. 4. Comparison of pressure rate between MEKPO and MEKPO with low concen-trations of contaminants.

W. Meng et al. / Journal of Loss Prevention in the Process Industries 25 (2012) 202e208204

of MEKPO. When further increasing the concentration of Fe2O3,the onset temperature of MEKPO significantly decreases from 86 to58 �C (Figs. 2(a) and 3(a)). This result implies that intermediate andhigh concentration of ferric oxidewill effectively impair the stabilityof MEKPO.

The pressure data shown in Figs. 1(b)e3(b) complies withtemperature data shown in Figs. 1(a)e3(a). Nevertheless, themaximum pressures of samples 3 and 4 (Fig. 1(b)), which aresupposed to be alike, have a difference of more than 100 psi. Thisis because the adiabatic process was shutdown due to reachinga certain temperature rate limit we set before starting the test, butthe relief valve of APTAC might have a delay at that moment,which caused a delay in pressure tracking and leaded to maximumpressure rise.

The pressure rate data obtained from calorimeter tests arepresented in Figs. 4e6 respectively. The pressure rate data in Fig. 6shows the impact imposed by big amount of ferric oxide whenadded into MEKPO. MEKPO with high and intermediate concentra-tions of contaminants shows higher pressure rate throughout therunaway reaction process. However, in the low concentration range,ferric oxide has no significant impact on pressure rate.

3.2. Kinetic studies

Investigationwas also done to study the kinetics of the runawayreaction in presence of ferric oxide. Since the reaction mechanismis still unknown, two types of reactionmodel were employed in thisstudy to identify the kinetics of the reaction and estimate impor-tant kinetic parameters.

3.2.1. nth Order reaction modelThe nth order reaction can be describe using the following

equation (Lu, Ng, Miao, & Mannan, 2010; Townsend & Tou, 1980)

dCdt

¼ �kCn (1)

where C is the concentration of the reactant. Also, we know at anytemperature, the concentration of the reactant and the tempera-ture of the system have an approximate relation

Fig. 5. Comparison of pressure rate between MEKPO and MEKPO with intermediateconcentrations of contaminants.

W. Meng et al. / Journal of Loss Prevention in the Process Industries 25 (2012) 202e208 205

C ¼ Tf � TDTAB

C0 (2)

here C0 is the initial concentration of the reactant, Tf is the finaltemperature, and DTAB is the adiabatic temperature rise, Tf� T0,while T0 here is the initial temperature. Equations (1) and (2) can becombined together

mT ¼ dTdt

¼ k�Tf � TDTAB

�n

DTABCn�10 (3)

where mT is called the self-heating rate measured at temperatureT, or time t. And also, with the Arrhenius equation

k ¼ A e�Ea=RT (4)

Arrhenius equation can be rewritten as:

ln k ¼ ln A� EaR

�1T

�(5)

Substituting equation (3) into equation (2) leads to the calculationmethodology of Arrhenius parameters Ea and A of an nth orderreaction.

The thermal inertia factor (F) is considered to reduce the heattransfer of the reaction vessel. Equation (6) shows one way toderive adiabatic temperature rise from pseudo temperature rise.

Fig. 6. Comparison of pressure rate between MEKPO and MEKPO with high concen-trations of contaminants.

DTAB ¼ fDTAB;s (6)

where subscript s stands for the total system. Therefore, theadiabatic final temperature of the sample, Tf, is thus

Tf ¼ T0 þ fDTAB;s (7)

The simulated self-heating rate for some tests was plotted versusexperimental data in Fig. 7. The estimation for kinetic parametersusing nth order reaction model are presented in Table 2 From thistable, for the MEKPO samples contaminated with low concentrationsof Fe2O3 we can clearly see an increase of onset temperature, andactivation energy, and a decrease in heat of reaction, which meansthe decomposition reaction is more unlikely to start (higher onsettemperature and activation energy) and is less hazardous (less heat ofreaction)when adding a small amount of ferric oxide. However,whenmore Fe2O3 is added to the MEKPO solution, this trend reverses.With large amounts of Fe2O3 added into MEKPO samples, we canobserve the decrease of onset temperature, activation energy and theincrease of heat of reaction. This means that when a large quantityof ferric oxide exists in the equipment or process, the thermal stabilityof MEKPO will decrease. However, such high concentrations ofcontaminant are very unlikely to occur in a process and the MEKPOcan be considered insensitive to the presence of Fe2O3 in concentra-tions typically exist in process industry (i.e., traces).

However, by comparing the simulated and experimental resultsin Fig. 7, the nth order reaction model cannot well simulate therunaway reaction process due to the gap between experimentaland simulation results. More advanced kinetic model needs to bedeveloped to study the kinetics of the MEKPO runaway reaction.

3.2.2. Autocatalytic reaction modelThe reaction mechanism of MEKPO decomposition is very

complex and some other reaction model other than the nth orderreaction model has been proposed by other researchers. Kossoyet al. proposed a kinetic model composed of nth order reactionfollowed by an autocatalytic reaction (Kossoy, Benin, & Akhmetshin,2005). In all the previous literatures where this model were applied(Lin et al., 2008; Tseng et al., 2005), DSC was used to collectexperimental data. The DSC heating rate versus time plots clearlyshow two or more peaks, while data presented by APTAC onlyshows a sharp one because once a runaway reaction begins andthe heat rate start to accelerate in the test cell under adiabaticconditions, the temperature rises much faster. In this work, anautocatalytic model was adopted, and it is shown as follows:

dadt

¼ A e�Ea=RT ð1� aÞn1ðzþ an2Þ (8)

where A is the frequency factor, Ea is the apparent activation energy,a is the conversion, n1, n2 and z are parameters used to describe thecatalytic effect of MEKPO (Liu, Wei, Guo, Rogers, & Mannan, 2009).Because the experimentwas conducted in an adiabatic environment,the self-heating rate can be calculated using the following equation.

CPm � dTdt

¼ DHrmdadt

� 1f

(9)

where CP is the heat capacity; m is the sample mass; DHr is heat ofreaction; f is thermal inertia factor.

Equations (8) and (9) can be combined together

dTdt

¼ DHr

CPf� A e�Ea=RT ð1� aÞn1ðan2 þ zÞ (10)

After developing the reaction model, a non-linear optimizationmethod was applied here to validate the model structure and

Fig. 7. Calculated versus experimental self-heating rate for nth order reaction model. (a) Pure MEKPO; (b) 0.03 wt% Fe2O3; (c) 0.293 wt% Fe2O3; (d) 19.6 wt% Fe2O3.

W. Meng et al. / Journal of Loss Prevention in the Process Industries 25 (2012) 202e208206

estimate the kinetic parameters. This method ensures the best fitto the experimental data by minimizing the measure of residualsbetween experimental and simulated responses. The objectivefunction in this optimization method is shown in equation (11).The estimated kinetic parameters obtained through non-linearoptimization method are listed in Table 3. The self-heating ratesobtained from some experiments are plotted versus calculatedvalue in Fig. 8.

SSðPÞ ¼Xi

wi�YexpðtiÞ � YsimðtiÞ

�2/min ¼ SS

�Pr�

(11)

where wi is the weight factor, Yexp is the experimental data, Ysim isthe simulation data.

As seen in Fig. 8, the calculated self-heating curve shows quitegoodfitting to experimental data in all contaminant levels, indicating

Table 2Kinetic parameters obtained from the 1st order reaction model.

Test no. Ferric oxideconcentration (wt%)

Tonset (�C) Hr (J/g) Ea (kJ/mol) ln A

1 0 86 928 74.5 12.22 0 90 931 77.4 13.73 0.030 97 860 89.2 17.24 0.032 97 899 86.2 16.45 0.075 86 979 74.0 12.26 0.293 86 941 68.9 10.67 1.006 76 1081 57.8 7.58 5.050 69 1302 52.6 5.79 10.154 66 1303 48.3 4.510 19.623 58 1669 41.1 1.9

that an autocatalytic reaction model can represent the decomposi-tion reaction of MEKPO andMEKPO contaminated by different levelsof Fe2O3. The kinetic parameters presented inTable 3 shows the effectof Fe2O3 on the kinetics of MEKPO runaway reaction.

The activation energy, an important parameter indicating thethermal stability, decreases significantly when the contaminantlevel is beyond 0.3 wt%, which is in agreement with the trend ofonset temperature data. The variation of activation energy impliesthat the decrease of activation energy leads to the decrease ofonset temperature. The dramatic decrease of frequency factor wasobserved when the contaminant concentration exceeds 0.3 wt%.With the presence of small quantity of Fe2O3, the heat of reactionshows small but noticeable reduction. However, in the intermediate

Table 3Kinetic parameters obtained from the autocatalytic model.

Test no. Ferric oxideconcentration(wt%)

Tonset (�C) Hr (J/g) n1 n2 Ea (kJ/mol) z ln A1

1 0 86 928 0.22 1.95 97.4 0.1 23.02 0 90 931 0.4 1.9 96.2 0.1 23.03 0.030 97 860 0.2 1.8 95.8 0.1 23.04 0.032 97 899 0.3 1.9 95.5 0.1 23.05 0.075 86 979 0.1 1.3 96.4 0.1 22.96 0.293 86 941 0.1 2.5 81.0 0.1 18.17 1.006 76 1081 0.1 2.5 77.0 0.1 17.28 5.050 69 1302 0.1 2.5 77.6 0.1 16.89 10.154 66 1303 0.1 2.1 67.9 0.03 15.310 19.623 58 1669 0.1 2.5 52.4 0.03 9.9

Fig. 8. Calculated versus experimental self-heating rate for autocatalytic reaction model. (a) Pure MEKPO; (b) 0.03 wt% Fe2O3; (c) 0.293 wt% Fe2O3; (d) 19.6 wt% Fe2O3.

W. Meng et al. / Journal of Loss Prevention in the Process Industries 25 (2012) 202e208 207

and high contaminant concentration range (5e20 wt%), the heat ofreaction increases significantly with the increase of contaminantlevel. The change of heat of reaction indicates the reaction mecha-nism of MEKPOmay have been changed in the presence of a certainamount of Fe2O3.

The phenomena observed earlier that the low concentration ofcontaminant increases the stability of MEKPO can be explained interms of kinetic parameters. In the range of low concentration ofFe2O3, heat of reaction is the only parameter whose change wasobserved. According to equation (10), if other parameters keep inthe same level, at the same temperature, decomposition reactionwith lower heat of reaction will present lower self-heating rate.This conclusion indicates that in order to reach the same detectableself-heating rate, MEKPO with low concentration of Fe2O3 requireshigher temperature compared with pure MEKPO.

4. Conclusions

The reactive hazards of MEKPOwere studied using APTAC underdifferent concentration of ferric oxide to identify the effect of ferricoxide on the reactive hazards. The experimental results showthat ferric oxide effectively impairs the thermal stability of MEKPOin the intermediate and high concentration range. The high ferricoxide level also leads to the increase of pressure rate. The kineticshows that the runaway reaction of MEKPO under adiabaticcondition follows autocatalytic reaction mode. Also, the trends ofkinetic parameters also confirm that experimental observation that

ferric oxide has no significant effect on the reactivity of MEKPO inlow concentration range.

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