Decomposition of Crotonaldehyde at Elevated Temperatures. Studies with a Single-Pulse Shock Tube

Article abstract of DOI:10.1021/j100357a027

The thermal decomposition of crotonaldehyde (CH3CH=CHCHO) in concentrations of ca. 0.5percent in argon was studied behind reflected shocks in a pressurized driver single-pulse shock tube over the temperature range 960-1350 K and overall densities of ca. 3E-5 mol/cm³.Under these experimental conditions the following decomposition products were found in the postshock mixtures: CO, CH4, C2H2, C3H6, CH2=CHCHO, CH3C<*>CH, CH2=C=CH2, C2H4, C2H6, C4H4, C2H6 and 1-C4H6.One dissociative H atom migration (resulting in the unimolecular formation of propylene and carbon monoxide) and two dissociation reactions initiate the decomposition of crotonaldehyde: (1) CH3CH=CHCHO -> CH3CH=CH2 + CO, (2) C3H5CHO -> *CH3 + *CH=CHCHO, and (3) C3H5CHO -> CH3CH=CH* + CHO*.Following secondary reactions the two dissociative channels (reactions 2 and 3) yield hydrogen atoms, methyl radicals, acetylene, and carbon monoxide.The second channel yields also acrolein (CH2=CHCHO), and the third contributes to the production of propylene at higher temperatures.The rate parameters obtained for the overall pyrolysis of crotonaldehyde over the temperature and pressure ranges of this experiment are k_total = 1E16.04exp(-73 * 1E3/RT) s^-1 where R is expressed in units of cal/(K*mol).The reactions of the initiation products as well as of free radicals lead to the formation of plethora of reaction products.Arrhenius rate parameters for their formation are reported, and a general pyrolysis scheme is suggested.