n-Hexadecane hydrocracking Single-Event MicroKinetics on Pt/H-beta

[EN] The Single-Event MicroKinetic (SEMK) model constructed for gas-phase hydroconversion of light n-alkanes on large-pore USY zeolites was applied, for the first time, to the hydrocracking of n-hexadecane on a Pt/H-Beta catalyst. Despite the 12-ringed pore channels, shape selectivity was observed in the formation of ethyl side chains. Additionally, heavy feed molecules such as n-hexadecane lead to physisorption saturation of the catalyst pores by strong Van der Waals interactions of the long alkyl chains with the zeolite framework. Intermolecular interactions and packing efficiencies in the pores induce deviations from typical Henry-regime physisorption characteristics as the physisorption selectivity, which is expected to increase with increasing carbon number, appeared to be independent of the latter. Micropore saturation effects were described by the 'size entropy' which quantifies the difference in standard entropy loss between physisorption in the Henry regime and hindered physisorption on a saturated surface. The size entropy is proportional to the catalyst loading with physisorbed species and the adsorbate carbon number. The addition of a size entropy term in the SEMK model, amounting to 102J mol(-1) K-1 for a hexadecane molecule at full saturation, allowed accurately reproducing the contribution of secondary isomerization and cracking reactions, as quantified by means of a contribution analysis. (C) 2012 Elsevier B.V. All rights reserved.This work was funded by the European Research Institute of Catalysis and the European Community’s Sixth Framework Programme. This work was also supported by the Research Board of Ghent University (BOF), the Interuniversity Attraction Poles Programme–Belgian State–Belgian Science Policy and the Long Term Structural Methusalem Funding by the Flemish Government. Financial support by the Comisión Interministerial de Ciencia y Tecnología (CICYT) of Spain through the Project CTQ2010-17988/PPQ is also gratefully acknowledged.Vandegehuchte, BD.; Thybaut, JW.; Martinez Feliu, A.; Arribas Viana, MDLD.; Marin, GB. (2012). n-Hexadecane hydrocracking Single-Event MicroKinetics on Pt/H-beta. Applied Catalysis A General. 441:10-20. doi:10.1016/j.apcata.2012.06.054S102044

Kinetic models for catalytic reactions from first principles: Benzene hydrogenation

10.1080/00268970410001668516Molecular Physics1023 PART II267-272MOPH

Extension of the Single-Event Methodology to Metal Catalysis: Application to Fischer-Tropsch Synthesis Extension de la méthodologie des événements constitutifs à la catalyse métallique : Application à la synthèse Fischer-Tropsch

The single-event methodology has been extended to metal catalysis using Fischer-Tropsch synthesis on an iron-based catalyst as case study. The reaction mechanism has been assessed in terms of elementary steps that could be categorized in reaction families such as reductive elimination, β-hydride elimination and methylene insertion. A computer code has been developed for the generation of the reaction network containing these elementary steps. The representation of reacting and intermediate species explicitly takes into account metal-carbon bonds as well as the presence of oxygen. The model has been validated using iron-based catalytic data at 623 K, 0.6 to 2.1 MPa, inlet molar H2/CO ratio between 2 and 6. 14 parameters, among which 10 activation energies and 4 atomic chemisorption enthalpies have been adjusted to the experimental data. Experimentally observed trends in alkane and 1-alkene product yields with the carbon number were adequately reproduced as well as the individual molar yields of the non-hydrocarbon products. <br> La méthodologie par événements constitutifs a été étendue à la catalyse métallique en utilisant la synthèse Fischer-Tropsch sur un catalyseur au fer comme cas d'étude. Le mécanisme réactionnel a été décomposé en étapes élémentaires qui peuvent être classées par type de réactions, telles que l'élimination réductrice, l'élimination d'hydrure en β, et l'insertion de groupe méthylène. Un code de calcul a été développé pour générer le réseau réactionnel impliquant ces étapes élémentaires. La représentation des réactifs et des espèces intermédiaires prend en compte explicitement les liaisons carbone-métal et inclut la présence d'atomes d'oxygène. Le modèle a été validé sur une base de données obtenues sur un catalyseur à base de fer à 623 K, sur une plage de 0,6 à 2,1 MPa, un ratio H2/CO en entrée variant de 2 à 6. Quatorze paramètres, dont 10 énergies d'activation et 4 enthalpies de chimisorption atomique ont été ajustés aux données expérimentales. Les tendances observées expérimentalement pour les rendements en alcanes et alcènes-1 en fonction du nombre de carbones sont correctement reproduites, ainsi que les rendements molaires des produits non-hydrocarbures

First-principles based kinetic model for the hydrogenation of toluene

10.1016/j.jcat.2005.09.019Journal of Catalysis2361129-13