Kinetics of the thermal gas-phase decomposition of 1,2-epoxypropane

Abstract

The kinetics of the gas-phase decomposition of 1,2-epoxypropane have been studied over the temperature range 654–717 K at pressures between 5 and 326 Torr. Unimolecular isomerizations to propanal, propanone, methyl vinyl ether and allylol account for ∼90 % of the primary reactions. Secondary reactions, that make quantitative determination of the individual rate constants difficult, are reduced by studying the reaction in the presence of nitric oxide. The rate constants, expressed in Arrhenius form, for the reactions from 131 Torr initial reactant with 8.5 % nitric oxide added, are as follows:, k_propanal/s^–1=10^{14.39 ± 0.18} exp (–244.7 ± 2.4 kJ mol^–1/RT);, (k_propanone)₁₃₁ Torr/s^–1=10^{14.18 ± 0.18}exp (–250.5 ± 2.4 kJ mol^–1/RT);, k_{methyl vinyl ether}/s^–1=10^{13.51 ± 0.23} exp (–245.9 ± 3.1 kJ mol^–1/RT);,k_allylol/s_–1=10^{12.90 ± 0.15} exp (–239.1 ± 2.0kJ mol^–1/RT)., Chemical activation effects result in the decomposition of some of the initially formed propanone. RRKM calculations satisfactorily reproduce the observed pressure dependence of propanone yields and allow an estimate to be made for the limiting high pressure rate constant for formation of propanone.

(k_propanone)∞/s^–1= 10^14.23exp (–254 kJ mol^–1/RT)

Self-heating effects are considered and it is possible that the above activation energies and pre-exponential factors would be reduced by ∼900 J mol^–1 and ∼10^0.07 respectively in the absence of self-heating.