Quantitative screening of an extended oxidative coupling of methane catalyst library

A comprehensive microkinetic model, including catalyst descriptors, that accounts for the homogeneous as well as heterogeneously catalyzed reaction steps in Oxidative Coupling of Methane (OCM) was used in the assessment of large kinetic datasets acquired on five different catalytic materials. The applicability of the model was extended from alkali magnesia catalysts represented by Li/MgO and Sn-Li/MgO and alkaline earth lanthana catalysts represented by Sr/La2O3 to rare earth-promoted alkaline earth calcium oxide catalysts, represented by LaSr/CaO, and to a Na-Mn-W/SiO2 catalyst. The model succeeded in adequately simulating the performance of all five investigated catalysts in terms of reactant conversion and product selectivities in the entire range of experimental conditions. It was found that the activity of Sr/La2O3, in terms of methane conversion, is approximately 2, 5, 30 and 33 times higher than over the La-Sr/CaO, Sn-Li/MgO, Na-Mn-W/SiO2 and Li/MgO catalysts, respectively, under identical operating conditions. This was attributed mainly to the high stability of adsorbed hydroxyls, the high stability of adsorbed oxygen and the high concentration of active sites of Sr/La2O3. The selectivity towards C2 products was found to depend on the methyl radical sticking coefficient and the stability of the adsorbed oxygen and was the highest on the Na-W-Mn/SiO2 catalyst, that is 75% at about 1% methane conversion and 1023 K, 190 kPa and inlet molar CH4/O2 ratio of 4

From fundamental insights to economic viability: valorization of minors from deodorizer distillates

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Key parameters controlling selectivity and conversion in OCM: from experiments and modelling, towards an optimised reactor design

SSCI-VIDE+ING+YSC:CMIInternational audienceNon

Key parameters controlling selectivity and conversion in OCM: from experiments and modelling, towards an optimised reactor design

SSCI-VIDE+ING+YSC:CMIInternational audienceNon

Key parameters controlling selectivity and conversion in OCM: from experiments and modelling, towards an optimised reactor design

SSCI-VIDE+ING+YSC:CMIInternational audienceThe present work focuses on the engineering descriptor Volume-to-Surface (V/S) ratio required for designing an Oxidative coupling of Methane (OCM) reactor. This parameter is analysed against catalytic performance (activity, C2 selectivity and ethylene-to-ethane ratio) for two Sr-La/CaO and Mn/Na/WSiO2 OCM catalysts. In parallel, changes of that parameter are calculated from a micro-kinetic model and the convergence between experiments and calculations is analysed. From this analysis, guide-lines are proposed for further reactor design

A microkinetic vision of High-Throughput catalyst formulation and optimization: development of an appropriate software tool

internationalInternational audienc

Fischer-Tropsch Synthesis: Development of a Microkinetic Model for Metal Catalysis

The construction of a single-event microkinetic (SEMK) model for metal catalysis using Fischer-Tropsch synthesis as example reaction is addressed. SEMK's describe the full product distribution with a limited number of kinetic parameters. A computer algorithm is required to generate all the elementary steps and species of the reaction network. Reacting and intermediate species are represented with Boolean matrices and standardized labels. The adjustable model parameters are the atomic chemisorption enthalpies of carbon, oxygen and hydrogen on the metal surface and the single-event kinetic coefficients of the kinetically relevant reaction families

Unraveling Diffusion and Other Shape Selectivity Effects in ZSM5 Using <i>n</i>‑Hexane Hydroconversion Single-Event Microkinetics

Potentially dominant factors governing the shape selectivity in <i>n</i>-hexane hydroconversion over a Pt/H-ZSM5 catalyst were evaluated by means of single-event microkinetic (SEMK) model regression against experimental data. The observed product distribution could be adequately modeled, and a corresponding physically meaningful interpretation could be made only when accounting for intracrystalline diffusion limitations for each hexane isomer involved in the reaction network, rather than considering physisorption effects or transition-state shape selectivity. Simultaneous diffusion and reaction inside the catalyst crystallites were expressed via Fick’s second law, while the alkane Fick diffusion coefficients were assessed by explicitly accounting for mixture nonideality effects. A 3-fold lower diffusion coefficient was found to be required for 3-methylpentane compared with 2-methylpentane to explain the typically high selectivity toward the latter alkane. Once formed inside the catalyst crystallite, dimethylbutane isomers remained nearly immobile as was evident from their significantly lower diffusion coefficients. Reaction at the crystallite external surface was primarily responsible for the marginal conversion toward the former species, as observed experimentally