Manganese oxide-based catalysts for toluene oxidation

Four different catalysts based on manganese oxide were prepared: a perovskite (LaMnO3), via sol-gel method; Mn2O3, rapid method and an Octahedral Molecular Sieve (OMS-2) by two different preparation methods, via solid state (OMSs) and hydrothermal method (OMSh). The physicochemical properties of these catalysts were characterized by X-ray diffraction (XRD), N2 adsorption–desorption at −196 °C, thermogravimetric and differential thermal analysis (TGA/DTA), inductively coupled plasma optical emission spectroscopy (ICP-OES) and temperature-programmed reduction with hydrogen (H2-TPR). Their catalytic performances were evaluated in the catalytic oxidation of toluene. Three consecutive catalytic cycles were performed for each catalyst in order to reach steady state performances. In order to assess the stability of the catalysts under reaction conditions, the catalytic performances were studied upon long term experiments running for 24 h at 25% of toluene conversion. For comparison purposes, the catalytic activity of the present manganese oxide catalysts was compared with that of typical industrial catalysts such as a commercial Pd/Al2O3 catalyst containing 0.78% Pd. The crystalline features detected in the XRD patterns, are well-consistent with the formation of the desired structures. Based on their specific surface area and their low-temperature reducibility, the catalysts were ranked as follows: OMSs > Mn2O3 > OMSh > LaMnO3. This trend was in good agreement with the performances observed in the catalytic removal of toluene. A kinetic model was proposed and a good agreement was obtained upon fitting with the experimental data.Se prepararon cuatro catalizadores diferentes a base de óxido de manganeso : una perovskita (LaMnO 3 ), por el método sol-gel; Mn 2 O 3 , método rápido y Tamiz Molecular Octaédrico (OMS-2) por dos métodos de preparación diferentes, vía estado sólido (OMS s ) e hidrotermal (OMS h ). Las propiedades fisicoquímicas de estos catalizadores se caracterizaron por difracción de rayos X (XRD), adsorción-desorción de N 2 a −196 °C, análisis termogravimétrico y térmico diferencial (TGA/DTA), espectroscopia de emisión óptica de plasma acoplado inductivamente (ICP-OES) y reducción a temperatura programada con hidrógeno (H 2-TPR). Sus actuaciones catalíticas se evaluaron en la oxidación catalítica de tolueno. Se realizaron tres ciclos catalíticos consecutivos para cada catalizador con el fin de alcanzar rendimientos de estado estable. Para evaluar la estabilidad de los catalizadores en las condiciones de reacción, se estudiaron los rendimientos catalíticos en experimentos a largo plazo durante 24 h al 25 % de conversión de tolueno. Con fines comparativos, la actividad catalítica de los presentes catalizadores de óxido de manganeso se comparó con la de los catalizadores industriales típicos, como el Pd/Al 2 O 3 comercial.catalizador que contiene 0,78% Pd. Las características cristalinas detectadas en los patrones XRD son consistentes con la formación de las estructuras deseadas. Según su área de superficie específica y su reducibilidad a baja temperatura, los catalizadores se clasificaron de la siguiente manera: OMS s > Mn 2 O 3 > OMS h > LaMnO 3 . Esta tendencia estaba en buen acuerdo con los rendimientos observados en la eliminación catalítica de tolueno. Se propuso un modelo cinético y se obtuvo un buen acuerdo al ajustar con los datos experimentales

Nickel oxide supported on porous clay heterostructures as selective catalysts for the oxidative dehydrogenation of ethane

[EN] Porous clay heterostructures (PCH) have shown to be highly efficient supports for nickel oxide in the oxidative dehydrogenation of ethane. Thus NiO supported on silica with a PCH structure shows productivity towards ethylene three times higher than if NiO is supported on a conventional silica. This enhanced productivity is due to the increase in the catalytic activity and especially to the drastic increase in the selectivity to ethylene. Additionally, PCH silica partially modified with titanium in the columns (PCH-Ti) have also been synthesized and used as supports for NiO. An enhanced activity and selectivity to ethylene was found over NiO supported over PCH-Ti compared to the corresponding catalysts supported over the Ti-free PCH. The enhanced catalytic performance has been related to the high dispersion of nickel oxide particles on the support, which leads to a lower reducibility of the nickel oxide, hindering the oxidation of ethane into carbon oxides. More interestingly, the particle morphology plays an important role on the catalyst selectivity since a higher distortion of the NiO crystal lattice parameter meant an enhanced selectivity to ethylene.The authors would like to acknowledge the DGICYT in Spain (CTQ2012-37925-C03-1, CTQ2012-37925-C03-2 and CTQ2012-37925-C03-3) and the FEDER for financial support. We also thank the University of Valencia and SCSIE-UV for assistance.Solsona Espriu, BE.; Concepción Heydorn, P.; López Nieto, JM.; Dejoz, A.; Cecilia, JA.; Agouram, S.; Soriano Rodríguez, MD.... (2016). Nickel oxide supported on porous clay heterostructures as selective catalysts for the oxidative dehydrogenation of ethane. Catalysis Science and Technology. 6(10):3419-3429. https://doi.org/10.1039/C5CY01811KS3419342961

One-pot synthesis of nano-crystalline MCM-22

[EN] Nano-crystalline MCM-22 zeolite was synthesized in a one-pot procedure by the use of an organosilane (dimethyl-octadecyl-(3-trimethoxysilylpropyl)-ammonium chloride, TPOAC) in the zeolite synthesis gel. This crystal growth inhibition procedure introduced mesopores in the MCM-22 crystallites. The lower mechanical stability of the nano-crystalline MCM-22 zeolite compared with bulk MCM-22 can be countered to some extent by pillaring. The increased external surface of the microporous zeolite domains resulted in increased accessibility of the Bronsted acid sites, as followed from the better performance in liquid-phase benzene alkylation with propylene as compared with bulk MCM-22. The increased accessibility of the internal acid sites in Mo-loaded hierarchical MCM-22 was also evident from the improved benzene selectivity during methane aromatization. Silylation of hierarchical Mo/MCM-22 was detrimental for the catalytic performance in MDA. The nano-crystalline MCM-22 has physico-chemical and catalytic properties intermediate between those of MCM-22 and ITQ-2 with the benefit over ITQ-2 that it can be synthesized in a single step. (C) 2015 Elsevier Inc. All rights reserved.Funding from the 7th Framework Program of the European Commission through the Collaborative Project Next-GTL (agreement no 229183) and financial support by the Spanish Government-MINECO through "Severo Ochoa" (SEV 2012-0267), Consolider Ingenio 2010-Multicat (CSD2009-00050) and MAT2012-31657 are acknowledged. Marta E. Martinez Armero thanks MINECO for economical support through pre-doctoral fellowship for doctors training (BES-2013-066800). The authors thank B. Esparcia for technical assistance.Tempelman, CHL.; Portilla Ovejero, MT.; Martínez Armero, ME.; Mezari, B.; De Caluwe, NGR.; Martínez, C.; Hensen, EJM. (2016). One-pot synthesis of nano-crystalline MCM-22. Microporous and Mesoporous Materials. 220:28-38. https://doi.org/10.1016/j.micromeso.2015.08.018S283822

Corrélation entre l'acido-basicité de surface et la mobilité de l'oxygène. (Conférence invitée)

SSCI-VIDE+CARE+CDSNational audienceNon

Catalytic wastewater treatment: oxidation and reduction processes. (conférence invitée)

SSCI-VIDE+CARE+CDSInternational audienceNon

Application of carbon materials in wastewater treatment

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Catalytic wet (air or peroxide) oxidation for the treatment of wastewater

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Environmental Catalysis: when the oxygen activation/mobility plays a major role

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Réduction catalytique du monoxyde d'azote par le méthane : traitement des gaz d'echappement des moteurs fonctionnant au gaz naturel (G.N.V.)

SSCI-VIDE+CARE+CDSInternational audienceNon