Pyrolysis of Acrylonitrile at Elevated Temperatures. Studies with a Single-Pulse Shock Tube

Article abstract of DOI:10.1021/j100341a038

The thermal decomposition of acrylonitrile was studied behind reflected shocks in a single-pulse shock tube over the temperature range 1150-1430 K and overall densities of ca. 3 X 10^-5 mol/cm³.Under these conditions the major reaction products are (1) hydrogen cyanide and acetylene and (2) hydrogen and cyanoacetylene: CH2=CHCN -> CH*CH + HCN (reaction 1) and CH2=CHCN -> CH*C-CN + H2 (reaction 7).In the presence of toluene, at a ratio of ₀/₀ ca. 10/1, a twofold decrease in the production rate of these products was observed, indicating a free-radical mechanism in parallel to the four-center eliminations.After the contribution of the free radical chain was subtracted, the following rate constants for the four-center eliminations were obtained: k₁ = 10^12.25 exp (-68 X 10³/RT) s^-1, and k₂ = 10^13.40 exp (-77 X 10³/RT) s^-1, where activation energies are expressed in units cal/mol.Ethylene was found in quantities roughly equal to those of cyanoacetylene.C2N2, CH3CN, CH4, C4H6 and C2H6 were found in the postshock mixtures but at much lower concentrations.Arrhenius parameters for the formation rate of the different reaction products are given and the general pyrolysis mechanism is discussed.