Preparation and surface functionalization of MWCNTs: study of the composite materials produced by the interaction with an iron phthalocyanine complex

Carbon nanotubes [CNTs] were synthesized by the catalytic vapor decomposition method. Thereafter, they were functionalized in order to incorporate the oxygen groups (OCNT) and subsequently the amine groups (ACNT). All three CNTs (the as-synthesized and functionalized) underwent reaction with an iron organometallic complex (FePcS), iron(III) phthalocyanine-4,4",4",4""-tetrasulfonic acid, in order to study the nature of the interaction between this complex and the CNTs and the potential formation of nanocomposite materials. Transmission electronic microscopy, N2 adsorption at 77 K, thermogravimetric analysis, temperature-programmed desorption, and X-ray photoelectron spectroscopy were the characterization techniques employed to confirm the successful functionalization of CNTs as well as the type of interaction existing with the FePcS. All results obtained led to the same conclusion: There were no specific chemical interactions between CNTs and the fixed FePcS

Acetonitrile Synthesis via Ammoxidation: Mo/zeolites Catalysts Screening

International audienceMo/zeolites catalysts were investigated in ethane and ethylene ammoxidation into acetonitrile. The catalysts were prepared either in solid-solid or liquid-solid interface after varying different parameters. The stabilization of Mo species upon the exchange is dependent on the hydrophilic/hydrophobic character of the zeolite and the type of Mo precursor. In fact, zeolites with low Si/Al molar ratios should be avoided due to their higher dehydration enthalpy values (Δ dehyd .H). On the other hand, the use of MoOCl 4 , Mo(CO) 6 and MoCl 3 precursors and zeolites with high Si/Al ratios led to inefficient [Mo 7 O 24 ] 6species and amorphous MoO 3 which catalyzes the combustion reaction. Nevertheless, the use of MoCl 5 , MoO 3 and MoO 2 (C 5 H 7 O 2) 2 led to promising activities. In catalysis, [MoO 4 ] 2species are required to activate C 2 H 6 into C 2 H 4 , while [Mo x O3 x+1 ] 2-(x =1, 2) species catalyze the ammoniation of C 2 H 4 and the ethylamine dehydrogenation into CH 3 CN. Interestingly, active catalysts could be obtained by humid impregnation and a simultaneous oxidative treatment. Such a treatment improves the dispersion state of crystalline MoO 3 , which activate ethane molecules. It is judicious to perform C 2 H 6 oxidative dehydrogenation before ammoxidation since the interference between the different investigated parameters could be noted

Comparative Study of Different Acidic Surface Structures in Solid Catalysts Applied for the Isobutene Dimerization Reaction

Dimerization of isobutene (IBE) to C8s olefins was evaluated over a range of solid acid catalysts of diverse nature, in a fixed bed reactor working in a continuous mode. All catalytic materials were studied in the title reaction performed between 50–250 C, being the reaction feed a mixture of IBE/helium (4:1 molar ratio). In all materials, both conversion and selectivity increased with increasing reaction temperature and at 180 C the best performance was recorded. Herein, we used thermogravimetry analysis (TGA) and temperature programmed desorption of adsorbed ammonia (NH3-TPD) for catalysts characterization. We place emphasis on the nature of acid sites that a ect the catalytic performance. High selectivity to C8s was achieved with all catalysts. Nicely, the catalyst with higher loading of Brønsted sites displayed brilliant catalytic performance in the course of the reaction (high IBE conversion). However, optimum selectivity towards C8 compounds led to low catalyst stability, this being attributed to the combined e ect between the nature of acidic sites and structural characteristics of the catalytic materials used. Therefore, this study would foment more research in the optimization of the activity and the selectivity for IBE dimerization reactions.This research received external funding from the Spanish Government (CTQ2017-89443-C3-1-R and -3-R)

Catalytic behaviour of molybdenum-based zeolitic materials prepared by organic-medium impregnation and sublimation methods

International audienc

Preparation and surface functionalization of MWCNTs: study of the composite materials produced by the interaction with an iron phthalocyanine complex

Abstract Carbon nanotubes [CNTs] were synthesized by the catalytic vapor decomposition method. Thereafter, they were functionalized in order to incorporate the oxygen groups (OCNT) and subsequently the amine groups (ACNT). All three CNTs (the as-synthesized and functionalized) underwent reaction with an iron organometallic complex (FePcS), iron(III) phthalocyanine-4,4",4",4""-tetrasulfonic acid, in order to study the nature of the interaction between this complex and the CNTs and the potential formation of nanocomposite materials. Transmission electronic microscopy, N2 adsorption at 77 K, thermogravimetric analysis, temperature-programmed desorption, and X-ray photoelectron spectroscopy were the characterization techniques employed to confirm the successful functionalization of CNTs as well as the type of interaction existing with the FePcS. All results obtained led to the same conclusion: There were no specific chemical interactions between CNTs and the fixed FePcS.</p

Catalizadores de Pd soportados en oxido de grafito y en sus derivados exfoliados aplicados en la hidrogenación de 1,3-butadieno

Trabajo presentado en el XXIV Congreso Iberoamericano de Catálisis, celebrado en Medellín (Colombia) del 14 al 19 de septiembre de 2014.Se prepararon dos series de catalizadores de Pd soportados sobre oxido grafitico y sus derivados exfoliados, empleando el método de intercambio y el método de impregnación, y se estudiaron en la reacción de hidrogenación del 1,3-butadieno. En la primera serie se redujeron las muestras a distintas temperaturas y sin exfoliar el oxido grafitico, y se observo un aumento en la actividad y selectividad hacia los productos deseados con la temperatura de reducción. En la segunda serie estudio la influencia de la etapa en la que tenía lugar la exfoliación del soporte sobre el comportamiento catalítico del Pd. Se consiguieron resultados optimizados de selectividad hacia butenos (98%) y en particular hacia el 1-buteno.Se agradece la financiación de este trabajo a cargo de los proyectos CTQ 2011-29272-C04-01 y 03 y del 2011/PUNED/0001.Peer Reviewe

Non-noble MNP@MOF materials: synthesis and applications in heterogeneous catalysis

[EN] Transition metals have a long history in heterogeneous catalysis. Noble or precious transition metals have been widely used in this field. The advantage of noble and precious metals is obvious in ‘heterogeneous catalysis’. However, the choice of Earth abundant metals is a sustainable alternative due to their abundance and low cost. Preparing these metals in the nanoscale dimension increases their surface area which also increases the catalytic reactions of these materials. Nevertheless, metals are unstable in the nanoparticle form and tend to form aggregates which restrict their applications. Loading metal nanoparticles (MNPs) into highly porous materials is among the many alternatives for combating the unstable nature of the active species. Among porous materials, highly crystalline metal-organic frameworks (MOFs), which are an assembly of metal ions/clusters with organic ligands, are the best candidate. MOFs, on their own, possess catalytic activity derived from the linkers and metal ions or clusters. The catalytic properties of both non-noble metal nanoparticles (MNPs) and MOFs can be improved by loading non-noble MNPs in MOFs yielding MNP@MOF composites with a variety of potential applications, given the synergy and based on the nature of the MNP and MOF. Here, we discussed the synthesis of MNP@MOF materials and the applications of non-noble MNP@MOF materials in heterogeneous catalysis.RH acknowledges the UNED and Fundación Mujeres por África for the scholarship Lear Africa. This work has been funded by the CSIC Project iCOOP-2019 COOPA20376, and 2019AEP076 as well as the Spanish Agency for International Development Cooperation AECID INNOVACION (2020/ACDE/000373). The support from Haramaya University via a research project HURG_2020_03_02_75 is duly acknowledged

Role of exposed surfaces on zinc oxide nanostructures in the catalytic ethanol transformation

For a series of nanometric ZnO materials, the relationship between their morphological and surface functionalities and their catalytic properties in the selective decomposition of ethanol to yield acetaldehyde was explored. Six ZnO solids were prepared by a microemulsion-precipitation method and the thermal decomposition of different precursors and compared with a commercial sample. All these materials were characterized intensively by XRD and SEM to obtain their morphological specificities. Additionally, surface area determinations and IR spectroscopy were used to detect differences in the surface properties. The density of acid surface sites was determined quantitatively using an isopropanol dehydration test. Based on these characterization studies and on the results of the catalytic tests, it has been established that ZnO basal surfaces seem to be responsible for the production of ethylene as a minor product as well as for secondary reactions that yield acetyl acetate. Furthermore, one specific type of exposed hydroxyl groups appears to govern the surface catalytic properties.The financial support of the Spanish government by Projects CTQ2011‐29272‐C04‐01 and CTQ2011‐29272‐C04‐03 is recognized. M.V.M. appreciates the financial support of UNED by a predoctoral grant.Peer Reviewe

Importance of basic sites on ZnO surfaces for bioethanol valorization

Trabajo presentado en el International Congress on Green Chemistry and Sustainable Engineering, celebrado en Barcelona (España), del 29 al 31 de julio de 2014.One of the major products of biomass conversion is ethanol, which can be the raw material to manufacture a number of chemical products. For example, dehydrogenation of ethanol using basic catalysts leads to acetaldehyde, which has been categorized as one of the promising bioethanol derivates from a sustainable perspective. One of the materials that catalyzes this reaction is ZnO, which crystallizes in a wurtzite-type structure, where the polar faces, (0001) and ( ), are located perpendicular to the c-axis while the nonpolar ones), are parallel to it. The polar/nonpolar facet ratio is often argued to be a key aspect in the photochemical catalytic activity. However, unlike in photocatalysis, in this reaction very little is known concerning the direct relation between ZnO morphology (i.e. polar/nonpolar facet ratio) and its catalytic performances. In this communication we present the catalytic properties of six polycrystalline ZnO samples used in the decomposition of ethanol.Peer Reviewe