SCR of NOx by NH3 over model catalysts: The kinetic data-linear free energy relation

We propose a kinetic data-linear free energy relation (KDLFER) that links kinetics with thermodynamic parameters to obtain the activation energy and pre-exponential factor:equation(1)lnk=EaΔG°lnKeq+lnAThe correlation describes the influence of the Gibbs free-energy (∆G°) and equilibrium constant (Keq) upon rate constant (k) and activation energy (Ea). The correlation also identifies the contribution of the enthalpic and entropic terms upon activation energy. SCR of NOx by NH3 over V2O5–WO3/TiO2 model catalysts was used to obtain and compare the parameters of Arrhenius equation with respect to those reported in this work.For the SCR process, we found that activation energy from KDLFER is similar to that obtained from the Arrhenius equation. We also found that the enthalpic term has a strong influence on the activation energy, which suggests that the SCR system follows a dissociative mechanism. However, the factors that control the changes in magnitudes of Ea for a particular reaction-catalyst still remain unanswered.

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► We propose a kinetic data-linear free energy relation.
► Activation energy and pre-exponential factor can be obtained from our relation.
► We found that the Gibbs free-energy affects directly the activation energy.
► Rate constant is limited by the equilibrium conversion with temperature.
► The results are based on the SCR of NO by NH3 over V–W/TiO2 catalysts.