由熱爆炸理論估算自催化物質之安全儲存溫度

Determination of the Safe Storage Temperature of Autocatalytic Materials by Thermal Explosion Theories

歐新榮(Hsin-Jung Ou) ； 張承明(Cheng-Ming Chang)

《勞工安全衛生研究季刊》 15卷2期 (2007/06) Pp. 159-169

https://doi.org/10.7005/JOSH.200706.0159

摘要

若物質具自催化反應特性且其反應屬放熱反應，當使用者無法適當辨識其反應動力特性，則物質可能會在儲存單元中引發劇烈的自催化反應危害。常見具自催化反應特性的物質有有機過氧化物及具雙鍵的聚合物單體，這些物質一旦受熱或與不相容性物質接觸時便會產生反應性危害，且此反應無法以簡單的n階反應模式來完整描述，需採用自催化反應模式進行描述較為恰當，而所得的反應動力參數，如頻率因子、反應活化能及反應階數皆為設計及操作儲存系統的重要參數。本文以丙烯酸酯作為範例，應用微差描熱卡計(differential scanning calorimetry, DSC)探討丙烯酸甲酯、丙烯酸乙酯、丙烯酸正丁酯、丙烯酸異辛酯等4種丙烯酸酯在沒有聚合起始劑及不相容物質的情況下，受熱所產生的放熱反應行為，並應用自催化反應模式描述DSC所測得的熱譜圖，其描述能力較n階反應優越。此外，本研究更修飾僅適用於n階反應模式的Semenov及F-K熱爆炸理論，將此2理論應用至自催化反應模式，並估算此4種丙烯酸酯於3種不同儲存容器的安全儲存溫度，其中安全儲存溫度以聯合國所建議的自加速分解溫度作為指標，結果顯示，具自催化反應特性之物質，應採用修飾後的Semenov或 F-K模式來估算其自加速分解溫度較為適當，否則將可能高估其自加速分解溫度，而導致在儲存過程中發生自催化反應危害。

關鍵字

安全儲存溫度 ； 自催化反應 ； 自加速分解溫度

並列摘要

Some materials have autocatalytic exothermic reactions, and when their kinetic characteristics have not been properly identified, poor storage of these materials can cause serious reactive incidents. Organic peroxides and monomers containing double bonds are typical materials that may have autocatalytic exothermic reactions. If they are heated or come in contact with incompatible materials, they can cause reactive hazards. While it is difficult to predict these hazardous reactions using an nth order reaction model, their behavior is described excellently by an autocatalytic reaction model. The autocatalytic reaction parameters, such as the pre-exponential factor (A), activation energy (Ea), and reaction order, are important in the design and operation of a safe storage unit. Four different acrylate esters were used as examples in this study: methyl acrylate (MA), ethyl acrylate (EA), n-butyl acrylate (BA), and 2-ethylhexyl acrylate (EHA). Differential scanning calorimetry (DSC) was used to determine the exothermic behavior of these four acrylate esters under heating and in the absence of any polymerization initiators or incompatible materials. The autocatalytic reaction model provides a good fit for these DSC patterns, with results that are much better than using the nth order reaction model. In addition, the Semenov and Frank-Kamenetskii (F-K) thermal explosion theories, originally intended for the nth order reaction model, were modified to work with the autocatalytic reaction model. The safe storage temperatures of these four acrylate esters in three different types of storage vessels were calculated based on the two modified thermal explosion theories. In this paper, the safe storage temperature refers to the UN suggested self-accelerating decomposition temperature (SADT). The results show that the modified Semenov and F-K thermal explosion theories are able to provide the SADT of autocatalytic materials while the temperatures are overestimated by the original theories. Overestimating the SADT might cause a user to become less concerned with the storage temperature and through negligence allow an autocatalytic accident during storage to occur.

並列關鍵字

Safe storage temperature ； Autocatalytic reaction ； Self-accelerating decomposition temperature SADT

參考文獻

Fisher HG,Goetz DD(1993).Determination of self-accelerating decomposition temperatures for self-reactive substances.Journal of Loss Prevention in the Process Industries.6,183-193.

United Nations (UN)(2003).Recommendations on the transport of dangerous goods, test and criterion.Now York and Geneva.

Yang D,Koseki H,Hasegawa K(2003).Predicting the self-accelerating decomposition temperature (SADT) of organic peroxides based on non-isothermal decomposition behavior.Journal of Loss Prevention in the Process Industries.16,411-416.

Semenov NN(1959).Some problems of chemical kinetics and reactivity.London:Pergamon Press.

Frank-Kamenetskii DA(1969).Diffusion and heat exchange in chemical kinetic.New York:Plenum Press.