Journal of Loss Prevention in the Process Industries 16 (2003) 389–393www.elsevier.com/locate/jlp

Evaluation on thermal hazard of methyl ethyl ketone peroxide byusing adiabatic method

Zhi-Min Fu a,∗, Xin-Rui Li b, Hiroshi Koseki b, Yun-Soo Mok c

a Department of Fire Protection Engineering, Chinese People’s Armed Police Force Academy, P.O. Box 424, Langfang 065000, Hebei, Chinab National Research Institute of Fire and Disaster, 181-8633 Japan

c Pukyong National University, South Korea

Received 4 April 2003; received in revised form 13 June 2003; accepted 20 June 2003

Abstract

Ketone peroxides are capable of spontaneous decomposition, and violent decomposition occurs if they contact with strong mineralacids. In this paper, an adiabatic method is used to investigate the thermal hazard of Methyl Ethyl Ketone Peroxide (MEKPO) andmixture of MEKPO with sulfuric acid in order to understand the effect of the contamination of sulfuric acid on the thermal stabilityof MEKPO. On the basis of experimental results, kinetic parameters of exothermic reaction of MEKPO and mixture of MEKPOwith 1% sulfuric acid are estimated, and thermal hazard parameters, such as the initial exothermic temperature and the adiabatictemperature rise are obtained under real adiabatic condition. It can be seen from the results that the thermal hazard of MEKPOwith sulfuric acid is more remarkable than that of MEKPO itself. 2003 Elsevier Ltd. All rights reserved.

Keywords: MEKPO; Explosion; Thermal hazard; Adiabatic method; Accelerating rate calorimeter (ARC)

1. Introduction

There exist various Ketone Peroxides (monomeric,dimeric, trimeric or polymeric) which can be producedfrom interaction of given ketone and hydrogen peroxide.Several types of structure are explosive and sensitive invarying degrees to heat and shock (Urben, 1995; Yosh-ida, 1987). They are capable of spontaneous decompo-sition, even relatively stable peroxides tend to releaseactive oxygen above 40 °C. Some decompose evenbelow room temperature. Contacted with strong mineralacids such as sulfuric acid, a violent decompositionoccurs. Although low-temperature type peroxides cap-able of self-accelerating thermal decomposition belowroom temperature have been developed to stable per-oxide, which can not generate appreciable amount of freeradicals without being heated to elevated temperature,explosions of Ketone Peroxides have occurred some-

∗ Corresponding author. Tel.: +86-316-2068509; fax: +86-316-2068501.

E-mail address: fuzmin2002@yahoo.com.cn (Z.-M. Fu).

0950-4230/$ - see front matter 2003 Elsevier Ltd. All rights reserved.doi:10.1016/S0950-4230(03)00067-6

times during their manufacture process, storage, trans-port or use.

Methyl Ethyl Ketone Peroxide (MEKPO, Permek H,N, S, F, G, NR, NY, NB, GR, GY, GB) is widely usedin manufacture of unsaturated polyester resins (NipponOil & Fats Co., 1996). Recently explosion accidents withregards to MEKPO have been reported for several times.Two of them occurred in Thailand and Korea, both inAugust 2000.

In this paper, an adiabatic method was used to investi-gate the thermal hazard of MEKPO and mixture ofMEKPO with H2SO4.

2. Experiments

2.1. Apparatus

In this study, an adiabatic calorimeter called ARC(Accelerating Rate Calorimeter, Aurther D Little Co.Ltd.) was used. This instrument was used for acquiringthermodynamic and kinetic information for runawayreactions in order to evaluate thermal hazards associated

390 Z.-M. Fu et al. / Journal of Loss Prevention in the Process Industries 16 (2003) 389–393

with the reactive material. The main components and thedetailed description of principle of ARC can be foundelsewhere (Townsend & Tou, 1980; Fu, Huang, Quan, &Feng, 2001). The main operation indexes of the ARCare temperature range 0–500 °C; pressure range 0–20MPa; sample mass range 0.01–10 g; slope sensitivity0.02 K·min�1.

2.2. Sources of materials and measuring conditions

The samples tested are MEKPO (Permek H) and mix-tures of MEKPO with 1% H2SO4. The chemical struc-ture of MEKPO (Permek H) is as follows (Nippon Oil &Fats Co., 1996).

The measuring conditions are listed in Table 1.MEKPO and mixture of MEKPO with 1% H2SO4 weretested twice respectively in order to observe the repeat-ability of the data.

3. Results and discussion

The measured data and curves of test Nos. 1–4 forMEKPO and mixture of MEKPO with 1% H2SO4 aregiven in Figs. 1–6 and Table 2.

The initial exothermic temperatures of tests Nos. 1and 2 (MEKPO) are very close, 327.70 and 328.81 Krespectively. While there is greater difference in initialexothermic temperature between tests Nos. 3 and 4(mixture of MEKPO with 1% H2SO4). The reason is thatthe start temperature was set higher than the initial exo-thermic temperature of mixture of MEKPO with 1%H2SO4 in test No. 3. In fact the initial self-heat rate of thesystem has reached 0.0236 K·min�1 when temperatureis 309.90 K from the data of test No. 4. The self-heatexothermic reaction has started before temperaturereaches to the set point 50 °C in test No. 3. Thereforehigher self-heat rate occurs at higher start temperature.

From the curves of temperature vs. time (Fig. 1) andself-heat rate vs. temperature for MEKPO (Fig. 3), it can

Table 1The sizes of measured samples and measuring conditions

Test No. Sample mass (g) Bomb mass (g) Start temperature (°C) Slope sensitivity (K·min�1) Heat step (K)

MEKPO 1 0.5899 6.6118 25.00 0.02 3.002 0.9742 6.5371 50.00 0.02 3.00

MEKPO 3 0.5718 6.5744 50.00 0.02 3.00�1% H2SO4 4 0.6539 6.5639 25.00 0.02 3.00

Fig. 1. Curves of temperature vs. time for MEKPO.

Fig. 2. Curves of temperature vs. time for mixture of MEKPO with1% H2SO4.

be recognized that there are three exothermic reactionphases for the decomposition of MEKPO. The first phase(AB) appears in a narrow temperature range and the tem-perature rise is smaller. In the second phase (BC) thetemperature rise is larger and in a wider range. In thethird phase (CD) the temperature rise of testing system

391Z.-M. Fu et al. / Journal of Loss Prevention in the Process Industries 16 (2003) 389–393

Fig. 3. Curves of self-heat rate vs. temperature for MEKPO.

Fig. 4. Curves of self-heat rate vs. temperature for mixture ofMEKPO with 1% H2SO4.

attains to the maximum. It is possible that this phenom-enon results from different molecular structures(monomeric, dimeric, trimeric or polymeric) included inMEKPO. While for mixture of MEKPO with 1% H2SO4,there is only one prominent exothermic process. This isa simple reaction process (Figs. 3 and 4).

The curves of temperature vs. time to maximum self-heat rate for MEKPO and mixture of MEKPO with 1%H2SO4 are shown in Figs. 5 and 6. The time to themaximum self-heat rate can be obtained at different exo-thermic temperature from these graphs.

Meanwhile, there is some difference in final tempera-ture of system and adiabatic temperature rise. The differ-ence depends on the different thermal inertia factor oftesting system. It is necessary to modify them by thermalinertia factor.

Fig. 5. Curves of temperature vs. time to maximum self-heat ratefor MEKPO.

Fig. 6. Curves of temperature vs. time to maximum self-heat rate formixture of MEKPO with 1% H2SO4.

4. Kinetic analysis and modification of measureddata

4.1. Determination of kinetic parameters

For an nth-order reaction with a single reaction, theself-heat rate of the adiabatic system can be expressedas (Townsend, & Tou, 1980; Fu, 2002)

mT � k�Tad·�Tf�T�Tad

�n

(1)

where mT is the self-heat rate at arbitrary temperature Tof adiabatic system, k is the rate constant, k =

Aexp��Ea

RT�, A is the pre-exponential factor, Ea is the

392 Z.-M. Fu et al. / Journal of Loss Prevention in the Process Industries 16 (2003) 389–393

Table 2The measured thermal decomposition characteristic data of MEKPO and its mixture

Test No. Sample Initial exothermic Initial self-heat rate of Final temperature of system Adiabatic temperature risemass (g) temperature of system (K·min�1) (K) of system (K)

system (K)

AB BC CD AB BC CD

MEKPO 1 0.5899 327.70 0.0206 330.07 336.89 356.90 2.37 6.82 20.012 0.9742 328.81 0.0236 334.42 346.26 389.58 5.61 11.84 43.32

MEKPO 3 0.5718 322.52 0.0599 361.07 38.55�1% H2SO4 4 0.6539 309.9 0.0236 354.91 45.01

apparent activation energy, R is the gas constant, �Tad

is the adiabatic temperature rise, �Tad = Tf�T0, Tf is thefinal temperature, T0 is the initial exothermic tempera-ture, n is the reaction order.

From the Eq. (1), the rate constant can be expressed as

k �mT

�Tad·�Tf�T�Tad

�n(2)

It has been known

lnk � lnA�Ea

R·1T

(3)

The plot of lnk vs.1T

is expected to be a straight line

provided that the order of reaction is correctly chosen.The Arrhenius kinetic parameters, Ea and A can be calcu-lated from the plot accordingly.

According to Eqs. (2) and (3), the curves of rate con-stant vs. absolute temperature and the fitting lines forfour tests can be obtained. It has been known that thedecomposition of MEKPO is first order reaction. Thesecond reaction phase (BC in Fig. 3) is the first mainreaction phase for MEKPO. Therefore the kinetic para-meters of second reaction phase for MEKPO are calcu-lated.

The linearity fitting results are listed in Table 3. Theapparent activation energy and pre-exponential factor are102.97 kJ·mol�1 and 1.77 × 1013 s�1 for MEKPO, 49.83kJ·mol�1 and 5.07 × 105 s�1 for mixture of MEKPOwith 1% H2SO4 respectively. These values have good

Table 3The calculated results of kinetic parameters for test No. 1 to No. 4

Test No. ln A E / R Relation A (min�1) Ea (kJ·mol�1) Temperature range (K)factor

MEKPO 1 32.81458 12175.76 0.9949 1.78×1014 101.23 ± 1.98 327.70 ~ 336.892 35.20773 12594.16 0.9776 1.95×1015 104.71 ± 3.32 339.02 ~ 344.65

MEKPO 3 17.90879 6678.64 0.9978 5.99×107 55.53 ± 0.38 325.73 ~ 344.92�1% H2SO4 4 13.69621 5307.43 0.9762 8.88×105 44.12 ± 0.27 321.32 ~ 340.85

agreement with that from the C 80 D (Li, Fu, Koseki, &Mok, 2002).

4.2. Modification of measured data

In order to eliminate the effects of thermal inertia oftest sample on measured results, it is necessary to modifythem by thermal inertia factor.

4.2.1. Thermal inertia factorUnder real experimental condition of the ARC, heat

from exothermic reactive sample rises the temperatureof both sample and reaction chamber. The relationshipbetween real adiabatic and pseudo adiabatic condition isas follows

MCvmT � (MCv � MbCv,b)mT (4)

where M is the mass of reactive materials, Cv is the heatcapacity of reaction material, Mb is the mass of the reac-tion container, Cv,b is the heat capacity of reaction con-tainer, mTs

is the self-heat rate of the reaction systemincluding the reactive material and the reaction con-tainer.

Define thermal inertia factor f as (Townsend, &Tou, 1980)

f �MCv � MbCv,b

MCv

(5)

4.2.2. Modification of adiabatic temperature rise,initial exothermic temperature and final temperature

From Eqs. (4) and (5), the relationship between adia-batic temperature rise and pseudo adiabatic temperature

393Z.-M. Fu et al. / Journal of Loss Prevention in the Process Industries 16 (2003) 389–393

Table 4The thermal decomposition characteristic data of test No.1 ~ 4 modified by thermal inertia factor f

Test No. Sample Thermal Initial exothermic Initial self- Final temperature of system (K) Adiabatic temperature riseMass (g) inertia temperature (K) heat rate of system (K)

factor (K·min-1)

AB BC CD AB BC CD

MEKPO 1 0.5899 3.79 316.32 0.02 325.30 351.15 426.99 8.98 25.85 75.842 0.9742 2.67 315.15 0.02 330.13 361.74 477.40 14.98 31.61 115.66

MEKPO 3 0.5718 3.86 288.51 0.02 437.31 148.80�1% H2SO4 4 0.6539 3.50 287.76 0.02 445.29 157.53

rise for reaction system including sample and containercan be expressed as

�Tad � f�Tad, s (6)

Regards T0 as the value when self-heat rate mT equalsinfinitesimal e, then Eq. (1) can be simplified as (Fu,2002)

e � �TadAexp��Ea

RT0� (7)

Therefore the initial exothermic temperature can beobtained

T0 �(�Ea)

RlnA�Te

(8)

The relationship between different initial exothermictemperatures at different initial self-heat rates can begotten from Eq. (8)

T02

T01�

lnA�Tad�lne1lnA�Tad�lne2

(9)

The finial temperature modified by thermal inertia factoris (Feng, Fu, & Qian, 2003)

Tf � f�Tad,s � � 1T0,s

�REa

lnf��1

(10)

The modified data by thermal inertia factor are listed inTable 4. The modified data show that thermal inertia fac-tor has to a certain extent effects on initial exothermictemperature, adiabatic temperature rise and final tem-perature.

5. Conclusions

The thermal stability of MEKPO and mixture ofMEKPO with 1% H2SO4 are investigated by using the

ARC. There are three decomposition processes whenMEKPO decomposes due to the existence of differentchemical structures in MEKPO. The initial exothermictemperature is low in first phase but the exothermic reac-tion lasts a short time. When H2SO4 is added, threephrases become a more sensitive and drastic but simpleexothermic process.

The data from the ARC suggested that the initial exo-thermic temperature of MEKPO is below 318.15 Kunder adiabatic condition, while the initial exothermictemperature of mixture of MEKPO with 1% H2SO4 islower than 289.15 K. The effect of sulfuric acid on thedecomposition process of MEKPO is significant.

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