Toward the quantification of aluminum in zeolites using high-resolution solid-state NMR

International audienceThis chapter discusses the quantification of aluminum (Al) in zeolites using high-resolution solid-state nuclear magnetic resonance (NMR). The recent introduction of multiple-quantum magic angle spinning (MQMAS), a new high-resolution NMR method facilitates the interpretation of the 27Al NMR spectra of zeolites and thus allows a fast and correct identification of the various aluminum sites. This technique yields new information about the structural distortions around the aluminum atoms. The information given by simulation of MQMAS leads to the correct quantification of the different sites present in the sampl

Hydrodésulfuration : étude comparative de catalyseurs Co-MoS2 / alumine

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Impact of citric acid on the impregnation of CoMoP/γ-Al 2 O 3 catalysts: time and spatially resolved MRI and Raman Imaging study

International audienceAn in-situ characterization methodology based on the Magnetic Resonance Imaging (MRI) and Raman Imaging is applied to investigate the effect of citric acid in the impregnation step of molybdenum catalysts promoted with cobalt in the presence of phosphorus and support on γ-alumina. MRI provides temporal and spatial information of the transport of species of the impregnation solutions within the porosity with a spatial resolution of 39×39µm. Raman Imaging gives information about the chemical nature of the species deposited on the support with a spatial resolution of 16.2×16.2µm. The effect of citric acid strongly depends on the ratio between the additive and molybdenum used in the impregnation solution. For a ratio of 0.2, at the end of impregnation, molybdenum ions are in an egg-yolk distribution either in polymeric or monomeric form. For a ratio of 0.7, cobalt ions can be in the form of aqua complexes in an egg-yolk distribution or in the form of H 2 PMo 11 CoO 40 5-heteropolyanion, which can improve the proximity between molybdenum and cobalt ions. This work gives new insights concerning the role of citric acid on the metal distribution profiles obtained at the end of impregnation, which can be used to control the final active phase distribution

Catalytic hydroconversion of a wheat straw soda lignin: Characterization of the products and the lignin residue

RAFFINAGE+BJF:CLO:MAV:DLA:CGEInternational audienceA wheat straw soda lignin was characterized and converted into gases and liquids under H-2 pressure, at 350 degrees C over a supported NiMo sulfide catalyst, using tetralin as a hydrogen-donor solvent in a batch autoclave. The aim of this work was to evaluate the transformations occurring during the temperature increasing step to reach a pseudo-t(0) and the impact of the catalyst presence in the mixture. A well-developed products separation protocol made possible to isolate and to characterize gases, organic liquid, lignin residue and solids (catalyst and char). A limited quantity of solids (or char) was produced however. As the lignin residue is one of the main intermediates of the lignin conversion pattern, the nature of this material has to be carefully determined. Thanks to several appropriate characterization techniques (GPC, NMR, FTIR), the conversion was followed and the lignin residue was compared to the initial lignin in order to understand the transformations occurring during the process. (C) 2013 Elsevier B.V. All rights reserved

Stability, activity and selectivity study of a zinc aluminate heterogeneous catalyst for the transesterification of vegetable oil in batch reactor

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Intrinsic potential of alumina-supported CoMo catalysts in HDS: Comparison between gamma c, gamma T, and delta-alumina

RAFFINAGE+DLA:CRO:LMA:MVRMoS2 catalysts were firstly prepared over three different alumina supports gamma c-Al2O3, gamma T-Al2O3, and delta-Al2O3 with the same Mo loading per nm(2). Then, using various deposition methods and different Co-precursors as Co(NO3)(2), Co(acac)(2) and Co(CO)(3)NO, Co-promoted MoS2 catalysts were obtained. The different catalytic systems were tested in hydrodesulfurization (HDS) reactions of thiophene and 4.6-dimethyldibenzothiophene (4,6-DMDBT) under atmospheric and high pressure (4 MPa), respectively. For the non-promoted catalysts, we observed for delta-alumina supported system a higher intrinsic catalytic activity than for gamma c-Al2O3 and gamma T-Al2O3. For the Co-promoted systems, the use of cobalt organometallic complex allowed obtaining catalysts which exhibit higher intrinsic activity than the catalysts prepared by impregnation of Co inorganic salts on supported Mo sulfide. Furthermore, the intrinsic catalytic activities of promoted systems obtained with delta-alumina support were always higher than for the classical gamma-alumina. This support effect can be partially explained and supported by physicochemical characterization results of XPS and IR of adsorbed CO at low temperature (77 K). (c) 2012 Elsevier Inc. All rights reserved

Speciation of Basic Nitrogen Compounds in Gas Oils and Vacuum Gas Oils by Derivatization with BF₃ prior to NMR Analysis

Nitrogen-containing compounds, present in gas oils (GO) or vacuum gas oils (VGO) cuts, affect many of the important petroleum processes such as hydrocracking and hydrotreating due to their nucleophilic character. Basic nitrogen compounds, which can inhibit the acidic sites of the catalysts, are mainly pyridine derivatives (6-membered-ring nitrogen compounds), and despite the use of highly resolutive methods, their characterization, especially in VGO, is still limited. Herein, we propose a new promising methodology, coupling the derivatization with BF₃ of nonprotogenic nitrogen species and the use of NMR analysis. By crossing information from ¹⁹F, ¹H, ¹H–¹⁹F HMBC and ¹⁹F DOSY, it is possible to determine the close environment of the nitrogen atom of the most nucleophilic nitrogen impurities in GO or in VGO cuts, independently of the sizes of the molecules. This approach allows the characterization and comparison of fingerprints of basic nitrogen impurities in charges or effluents