Juliette Blanchard

Catalysts for aromatics hydrogenation in presence of sulfur: reactivities of nanoparticles of ruthenium metal and sulfide dispersed in acidic Y zeolites

Zeolite-supported ruthenium sulfide and ruthenium metal catalysts were prepared with various Si/Al ratios, with and without extra-framework Al species. They were characterized by means of NMR, HRTEM and FTIR. For the sulfided catalysts, the activity for the tetralin hydrogenation, carried out in presence of H2S was very high and roughly 10 times the activity (expressed per gram of catalyst) of an industrial hydrotreating catalyst, i.e. NiMo/Al2O3. The differences in activities within the series of zeolites were discussed in terms of dispersion of the active phase and acidity of the zeolitic support. The catalytic properties of the metal catalysts were much lower than those of the sulfided catalysts in similar testing conditions.

Relevant parameters for obtaining high-surface area materials by delamination of magadiite, a layered sodium silicate

Layered silicates can be used for the preparation of high surface area materials by intercalation with organic cations followed by ultrasonication. The relevant parameters for delamination (exfoliation) of cetyltrimethylammonium bromide exchange magadiite are investigated. Using a magadiite wet cake, performing the delamination in water and recovering the solid phase by acidification allow increasing the surface area of the final material by a factor of ca. 20 (553 vs. 30 m2 g−1) compared to the standard procedure. The role of each step is analysed and the material resulting from the optimised procedure can be described as creased silicate layers. This results in a microporous–mesoporous material with about 60% of the surface in pores larger than 2.0 nm.

On the Detrimental Effect of Tungstates on the n-C10-SCR of NOx on Ag/γ-Al2O3

The influence of the addition of W to Al2O3, promoted or not by Ag, on the n-C10 SCR of NOx was investigated. It was shown that the addition of W was detrimental to the n-C10 SCR reaction. Based on the NOx-TPD, the XPS and the n-C10 SCR measurements, it was concluded that the loss of activity observed at temperatures lower than 400xa0°C on the Ag/W(5)–Al2O3 catalyst compared with the Ag/Al2O3 sample is likely due to the preferential deposition of Ag on the tungstate phase, making it inactive for the n-C10 SCR reaction which requires the active silver species to be in close contact with the Al2O3. At higher temperatures, the occupation, by the tungstates, of the Al2O3 sites responsible for the n-C10-SCR reaction is proposed to be an additional drawback accounting for the detrimental effect of W on Al2O3-supported catalysts promoted or not by Ag.

Confinement in Nanopores at the Oxide/Water Interface: Modification of Alumina Adsorption Properties

There is limited knowledge on the influence of the pore size on surface phenomena (adsorption, dissolution, precipitation, etc.) at the oxide/water interface and a better understanding of the space confinement in nanoscale pores should have practical implications in different areas, such as transport of contaminants in the environment or heterogeneous catalyst preparation, to name a few. To investigate the modifications of the oxide adsorption properties at the oxide/water interface in a confined environment, the surface acidobasic and ion adsorption properties of six different aluminas (5 porous commercial aluminas with pore diameters ranging from 25 to 200 A and 1 non-porous alumina) were determined by means of acid-base titration and Ni(II) adsorption. It is shown that the confinement has a moderate impact on the alumina adsorption capacity because all materials have similar surface charging behaviours and ion saturation coverages. However, a confined geometry has a much larger impact on the ion adsorption constants, which decrease drastically when the average pore diameter decreases below 200 A. These results are discussed in terms of nanoscale pore space confinement.

High surface area supports with strong Brønsted acidity in an open porosity

Two routes for the preparation of high surface area silica-alumina materials with strong Bronsted acidity and open porosity are examined: one uses the organisation of β-zeolite seeds with surfactant micelles, and the other the delamination of Al-Magadiite, a naturally occurring sodium phyllosilicate. The textures, of these materials are characterised using N 2 -sorption and the localisation of most of the Al in tetrahedral substitution in the silica, framework is shown using 27 Al MAS NMR. These two materials show good activity for the cracking of cumene. Furthermore, the characterization of their acidity by FTIR of adsorbed CO reveals the presence of strong and medium Bronsted acid sites.

Acidic zeolites and Al-SBA-15 as supports for sulfide phases: application to hydrotreating reactions

Hydrotreating catalysts were prepared by supporting molybdenum, nickel molybdenum or nickel tungsten sulfides on HBEA zeolites or Al-SBA-15 mesoporous materials. The effect of the acidity (strength and number of acidic sites) on the properties of the sulfide phases and on their catalytic activity was discussed. An effect of the zeolite acidity on the electronic properties of the MoS 2 phase was observed, leading to a considerable enhancement in the hydrogenation and hydrodesulfurization activity. On the other side, for nickel molybdenum sulfide catalysts supported on an Al-SBA-15 support, no effect of acidities on hydrodesulfurization activity was observed. This result was assigned to the mild Bronsted acidity of Al-SBA-15. However, compared to silica support or commercial silica-alumina, an improvement of the hydrocracking activity ( n -decane hydrocracking) of the nickel tungsten sulfide phase (NiWS) and isomerization selectivity (4,6-dimethyldibenzothiophene hydrodesulfurization) of the nickel molybdenum phase (NiMoS) was observed for the Al-SBA-15 supports.

Influence of thermal treatment on the dispersion of MoS2 into MCM-41 and SBA-15 supports: TEM study and hydrotreating activity

MoS 2 catalysts supported on MCM-41 and SBA-15 were prepared by impregnation with ammonium heptamolybdate (≈8.0 wt % Mo) with the aim of obtaining a high Mo oxide dispersion, then a high MoS 2 dispersion after sulfidation for application in reaction of hydrodesulfurization. The influence of the thermal treatment (under air at 573 and at 723 and under He at 823K) on the nature and dispersion of the MoO x phase, and then of the sulfided phase was first studied with a commercial silica support, by X-ray diffraction, transmission electron microscopy and hydrodesufurization of dibenzothiophene. The best conditions of the thermal treatment, i.e. , under He at 823 K were then successfully applied for the preparation of MoS 2 /MCM-41 and MoS 2 /SBA-15 catalysts, which leads to a higher hydrodesulfurization activity of dibenzothiophene than with MoS 2 supported on commercial silica.