Influence of Reaction Temperature on the Interpretation of Delplots for the Parallel-Series Reaction Network

The use of Delplots to deduce the key features of reaction networks using nonisothermal kinetics data was examined. Using Delplots, a product's network rank, i.e., the number of reaction steps required for its formation from a specified reactant "A," is generally obtained by extrapolating plots of y_i/xA_r vs x_A to x_A = 0, where at isothermal conditions, contact time was varied to provide the range of conversion supporting the extrapolation. The presently described work addressed the common experimentalists' technique of using temperature, rather than contact time, to provide the range of conversion. To assess any uncertainties thus introduced, the effect of changing the temperature of kinetic measurements has been addressed for the parallel-series reaction network A→k1B→k3C; A→k2D with B₀ = 0. The relative activation energies of the key reactions were varied by ±6 kcal/mol with respect to that for k₁, and temperature was varied between 200 and 1000 K. The resulting Delplot information can appear to suggest different reaction networks if the activation energy difference is too large and the temperature range too wide. The Delplot method classifies species B to be a primary product at low temperature when E₂ > E₁, while it appears to be a secondary product when E₂ < E₁. We suggest, as rough guidelines, that varying temperature to provide variations in conversion in the kinetic study is reasonable for E₁ ∼ 50 kcal/mol if the activation energy difference E₂₁ is in between 3 and 3 kcal/mol.