Kinetics of Pyrolysis of the Isomeric Butenenitriles and Kinetic Modeling

Article abstract of DOI:10.1021/j100180a052

Kinetics of pyrolysis of the butenenitrile isomers, cis- and trans-crotonitrile and allyl cyanide, have been studied dilute in argon in a single-pulse shock tube over the temperature range of 1200-1500 K at uniform gas residence times behind the reflected shock of between 650 and 750 μs and at pressures between 18 and 20 atm.Thermal decomposition was preceded by isomerization of the butenenitriles whose rates are coupled with the rates of thermal decomposition.The decomposition was found to follow a free-radical mechanism, with the major chain involving propagation reactions of the cyanomethyl radical to produce acetonitrile and acetylene.Other routes important to the mechanism involve hydrogen atom addition to the butenenitriles.HCN principally arises from this route.A detailed kinetic reaction model is presented to model the experimental reactants and products profiles as a function of temperature.From the modeling and experiment, the following initiation rate constants have been obtained: trans-CH3CH=CHCN -> CH3 + HC=CHCN (k_-11 = 10^17.45 exp(-96.5/RT) s^-1), cis-CH3CH=CHCN -> CH3 + HC=CHCN (k_-12 = 10^17.53 exp(-98.5/RT) s^-1), CH2=CHCH2CN -> H2C=CH + CH2CN (k_-13 = 10^15.53 exp(-82.6/RT) s^-1), where the activation energies are in kcal mol^-1.