Identification Methods And Application Of The Autocatalysis Of Material Decompositions

Autocatalytic decompositions often occur suddenly at high rates of heat release with destructive power and thus are difficult to prevent,and many materials decompose with autocatalytic characteristics.In autocatalytic decomposition reactions,although the initial reaction rate is low,the reaction rapidly accelerates once the reactants are consumed and the catalyst is generated.In such cases,thermal runaway can easily occur,then leading to accidents.In recent years,there are more and more incidents caused by autocatalytic reactions of substances.Therefore,in order to prevent accidents from occurring fundamentally,it is very necessary to study the characteristics of autocatalytic decomposition reactions,especially autocatalytic characterization methods and the degree of autocatalysis.To explore the autocatalysis of decomposition reactions under adiabatic conditions,two stages of the autocatalytic reaction were simulated with thermal safety software.By adjusting the kinetic parameters,the time difference At(t0.001-max?t0.02-max)during which the temperature rise rate increased from 0.001K·min-1 and 0.02K·min-1 respectively to the maximum was obtained.Comparison of ?t of the autocatalytic reaction with that of the n-order reaction showed that At of the two types of reaction may be comparable in some conditions.Therefore,it could not be determined whether a reaction under the adiabatic condition is an autocatalytic reaction or an n-order reaction only based on ?t.Furthermore,a ratio of the specific heat release of the first-stage to that of the total reaction was calculated to characterize the degree of autocatalysis under ideal adiabatic condition,and the ratio was classified into five grades,including strong,less strong,moderate,less weak and weak.Finally,five substances,including dicumyl peroxide(DCP),a 29.5%nitroguanidine(NQ)aqueous solution,cumyl hydroperoxide(CHP),dimethyl sulfoxide(DMSO)and benzaldoxime(BO),were graded by this method.Finally,four methods(Swiss method,the method of interruption and re-scanning,isothermal method,grading method of autocatalysis)were applied in the thermal decomposition of 2,4-DNT.The results showed that four kinds of autocatalytic identification methods have their own characteristics,but all proved that the thermal decomposition of 2,4-DNT has autocatalytic properties.And the results of grading method of autocatalysis show that 2,4-DNT is of strong autocatalysis.