Single-Event MicroKinetics of Aromatics Hydrogenation on Pt/H-ZSM22

Ab initio coverage-dependent microkinetic modeling of benzene hydrogenation on Pd(111)

Coverage-dependent calculations are required for an accurate DFT-based prediction of the activity and a correct mechanistic understanding of catalytic hydrogenation.

Hydrogen-atom attack on phenol and toluene is ortho-directed

The reaction of H + phenol and H/D + toluene has been studied in a supersonic expansion after electric discharge. The (1 + 1') resonance-enhanced multiphoton ionization (REMPI) spectra of the reaction products, at m/z = parent + 1, or parent + 2 amu, were measured by scanning the first (resonance) laser. The resulting spectra are highly structured. Ionization energies were measured by scanning the second (ionization) laser, while the first laser was tuned to a specific transition. Theoretical calculations, benchmarked to the well-studied H + benzene → cyclohexadienyl radical reaction, were performed. The spectrum arising from the reaction of H + phenol is attributed solely to the ortho-hydroxy-cyclohexadienyl radical, which was found in two conformers (syn and anti). Similarly, the reaction of H/D + toluene formed solely the ortho isomer. The preference for the ortho isomer at 100-200 K in the molecular beam is attributed to kinetic, not thermodynamic effects, caused by an entrance channel barrier that is ∼5 kJ mol(-1) lower for ortho than for other isomers. Based on these results, we predict that the reaction of H + phenol and H + toluene should still favour the ortho isomer under elevated temperature conditions in the early stages of combustion (200-400 °C).

Progress in kinetic predictions for complex reaction of hydrocarbons: from mechanism studies to industrial applications

Kinetic predictions for complex reaction systems of hydrocarbons are theoretically and technologically crucial to the petrochemical industry. Among several proposed kinetic models, a lumping kinetic model is a comparatively simple and developed method wherein a complex system is lumped into several pseudo-components. To acquire more accurate mechanistic information, kinetic models at the mechanistic level are developed, such as single-event kinetic and structure-oriented models. However, the number of kinetic parameters increases exponentially in these methods. Lumping kinetic methods are then reexamined, and kinetic models, such as relumping single-event kinetic methods, bimolecular methods, and special pseudo-component methods, are proposed to simplify the reaction system. Many mathematical methods, such as annealing algorithm or artificial neural networks, have also been developed to solve these complex reaction problems. Although a number of complex intrinsic reaction studies have been introduced, the combination of excellent prediction performances and practical industrial applicability remains a central challenge facing this field. This situation motivated this study, to review the recent development of reaction prediction models and their application in industrial processes. Furthermore, the practical applications of these possible pathways of kinetic predictions for mechanistic studies are addressed.