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

Enhancement of ethylene production by alkali metal doping of MoVSb mixed oxide catalyst for ethane oxidative dehydrogenation

Hydrothermally prepared Mo-V-Sb mixed oxides doped with alkali metal cations (Li, Na, K, Rb, or Cs) show a significantly improved catalytic behavior in the oxidative dehydrogenation of ethane (ODH) compared to conventional alkali metal-free MoVSbO catalysts. Initial selectivity to ethylene above 95 % was held up to 20 % of ethane conversion for all alkali metal promoted MoVSbO catalysts, as well as lower ethylene overoxidation at higher ethane conversion, with differences depending on the alkali metal employed. Thus, from Li to K, the enhanced catalytic performance follows a bottom-up trend as increasing the size of the cation. An intermediate behavior is observed though for the catalyst doped with Cs cations, with the highest atomic radius. The K-doped MoVSbO catalyst is the least prone to both ethane total oxidation and ethylene overoxidation, which enables up to 90 % selectivity to ethylene at ethane conversion higher than 65 %.This work was supported by the Ministerio de Ciencia e Innovación of Spain (projects PID21-126235OB-C31 and PID21-126235OB-C33). F. Ivars-Barceló also acknowledges the Ministerio de Ciencia e Innovación of Spain by the support from the “Ramón y Cajal” excellence grant (Ref.: RYC2020-029470-I/AEI/10.13039/501100011033)

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

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

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)

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

Catalytic methane combustion over Co, Mn and Fe exchanged zeolite CaA

World Congress on Oxidation Catalysis (6. 2009. Lille, France