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

C

Catalytic cracking of n-alkane naphtha: The impact of olefin addition and active sites differentiation

An extended dual kinetic model allows to fit the n-heptane cracking results working in a wide range of reaction conditions. The duality of the model is provided by the contribution of monomolecular and bimolecular cracking mechanisms. It takes into account the role played by the olefins formed on the global cracking or added within the feed. Furthermore by means of this model and the kinetic parameters obtained when cracking n-heptane on ZSM-5, it has been observed that, while some characterization techniques show a homogeneous zeolite surface from the point of view of the active sites, rigorous kinetic experiments point to the possibility that the reactant sees a heterogeneous surface with, at least, two groups of cracking active sites. Those differentiated active sites give different cracking rates and different activation energies for the process and, in the case of ZSM-5, could be assimilated to sites pointing to the 10R channels and sites pointing into the crossing of the 10R channels, mainly due to differences in kid site location and confinement effects. (C) 2015 Elsevier Inc. All rights reserved.Financial support by the Ministerio de Economia y Competitividad of Spain (MINECO) [Programa Estatal (Project MAT2012-31657) and Programa Consolider-Ingenio 2010 (Project MULTICAT)] is gratefully acknowledged.Corma Canós, A.; Mengual Cuquerella, J.; Miguel Dolz, PJ. (2015). Catalytic cracking of n-alkane naphtha: The impact of olefin addition and active sites differentiation. Journal of Catalysis. 330:520-532. https://doi.org/10.1016/j.jcat.2015.04.020S52053233

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