Mechanism and Rate Constants for 1,3-butadiene Decomposition

Data on the decomposition of 1,3-butadiene have been analyzed. The numerous isomerization processes that have recently been proposed as additional channels for decomposition have been considered. Energy transfer effects have been taken into account through the solution of the time-dependent master equation. We confirm recent supposition that direct formation of ethylene and acetylene is a major reaction channel during the thermal decomposition of 1,3-butadiene. The isomerization to 1,2-butadiene and its subsequent decomposition to form propargyl and methyl is the next most important process. Almost no vinyl radicals are produced. The formation of the isomerization products, in contrast to those from the initial reactant, is generally characterized by long transients before the attainment of a steady state. Standard methods of treating processes where such reactions are important must be carefully analyzed. The calculations are calibrated with experimental results. It proved not to be possible to fit simultaneously all the experimental observations with the model. Rate expressions for the major decomposition and isomerization channels are presented.