Collisional energy transfer in multichannel reaction system

Abstract

The objective of the present study is to develop and assess a new method to extract peak shape parameters from the exponentially modified Gaussian peak model, and apply the method to quantify real gas chromatograms for the study of multichannel system. This method requires both normal and derivative peak heights at four or five different time points with the same time interval. The essential peak shape parameters can be readily evaluated by solving the cubic or quartic equation of $\tau$. Computer simulation studies showed that in the case of a peak-to-peak noise value of 1.0\%, the peak parameters were reproducible within 1.5\% by the method developed in this study. The experimental works with the real chromatograms have shown that the parameters were recovered with the standard deviations no more than 1.57\%. Thermal decomposition reaction of 1,2-dibromopropane(12DBP) was studied at temperatures from 592.2 to 636.2 K over the pressure range 0.23-24.5 torr. The main products were four different bromopropenes and hydrogen bromide. Propylene as a minor product was also observed by the concurrent heterogeneous debromination. The inhibition effect by cyclohexene and propene, and the catalytic effect by HBr manifest that 12DBP is thermally decomposed by dual mechanisms, i.e., the unimolecular elimination and the radical chain process. The rate constant in maximal inhibition is expressed by $k_i=10^{13.8\pm0.4}\exp[(-50400\pm3000)/RT]\,(\sec^{-1})$. The pressure dependence was also studied both in the presence and in the absence of inhibitors. The fall-off curve obtained in maximum inhibition condition was compared with the theoretical curve calculated by RRKM formulation with the intermolecular energy transfer of $1000 cm^{-1}$. The reaction mechanism is proposed to offer a satisfactory explanation for thermal decomposition of 12DBP.