Catalyseurs à base de métaux nobles supportés sur zircone pour l'hydrodésazotation poussée des gazoles

Dans un contexte de protection de l'environnement de plus en plus sévère, les catalyseurs classiques d'HDN ne sont plus suffisamment actifs. Parmi les nouveaux systèmes catalytiques envisagés, les métaux nobles semblent prometteurs et particulièrement le platine supporté sur zircone. Nous avons dans un premier temps étudié l'influence des paramètres de préparation de la zircone sur les propriétés finales du solide de façon à obtenir un support adéquat du platine. L'étude de divers catalyseurs a démontré que la phase monoclinique de la zircone était un des facteurs très importants pour conduire à la rupture de la liaison C-N. Nous avons ensuite étudié l'évolution de la thiorésistance ou de l'activité par ajout d'un second métal. Pour les catalyseurs PtPd, les particules sont bimétalliques mais le palladium ségrégue en surface et aucune amélioration dans la rupture de la liaison C-N n'a été observée. Par contre, le système PtRu montre un gain sensible d'activité hydrodésazotante.LYON1-BU.Sciences (692662101) / SudocSudocFranceF

The influence of MoS2 slab 2D morphology and edge state on the properties of alumina-supported molybdenum sulfide catalysts.

International audienceTo study the influence of MoS2 particles morphology on their catalytic properties, a series of MoS2/Al2O3 catalysts was prepared, by means of treatment of oxide precursor under variable conditions. The conditions of treatment were selected to generate the MoS2 crystallites exposing preferentially M-edges or M- and S-edges, as predicted by the theory phase diagrams. The MoS2 particles size was estimated by electron microscopy and the degree of sulfidation to MoS2 was determined from X-ray photoelectron spectroscopy. The edge state of MoS2 particles was probed by FT-IR of adsorbed CO and by temperature programmed reduction (TPR). Hydrogenation (HYD) selectivity and hydrodesulfurization (HDS) selectivity were estimated from the catalytic tests using hydroconversion of 2,3-dimethylbut-2-ene and 3-methylthiophene. It seems that the variations of 2D morphology of MoS2 particles influence the HYD/HDS selectivity. However, a drastic drop of activity was observed when the preparation temperature increased from 250 to 700 °C which cannot be accounted by the decrease of the amount of exposed edges due to thermal sintering. At the same time a drastic loss of ability to adsorb CO and harder reducibility of sulfide edges were observed for the samples prepared at high temperatures. The results suggest that well crystallized edges of MoS2 bearing no excess sulfur have low activity whatever their symmetry type

Insight into sulphur compounds and promoter effects on Molybdenum-based catalysts for selective HDS of FCC gasoline

International audienceThe effect of the nature of sulphur compounds (H2S and 2-methylthiophene) over unsupported molybdenum-based sulphide catalysts (promoted or not by nickel or cobalt) for the transformation of a model FCC feed (hydrodesulphurisation of 2-methylthiophene and hydrogenation of 2,3-dimethylbut-2-ene) was investigated. The activities of the various catalysts were compared between each reactant alone and the full model mixture. The promoting effect of Co and Ni is found for both hydrodesulphurisation (HDS) and hydrogenation of olefins (HYD) reactions. However, the hydrogenation activity strongly depends on the amount of sulphur compound present in the feed. Nickel, used as a promoter, seems more sensitive than cobalt, particularly for the hydrogenation reaction. The presence of 2-methylthiophene in the feed induces a stronger inhibiting effect than H2S on HYD reaction. This result highlights the different adsorption constant ratio between olefins and sulphur molecules depending on the sulphur compounds. Even though an impact of H2S can be observed on the NiMo and CoMo catalysts, no major modification occurs on the volcano-shaped curves obtained in previous work, in terms of activity or selectivity, as a function of the metal–sulphur bond energy. Whatever the amount of H2S added, NiMo and CoMo catalysts fit into the curve, NiMo being the most active and the most selective under these conditions

Deep HDS of FCC gasoline over alumina supported CoMoS catalyst: Inhibiting effects of carbon monoxide and water

International audienceThe selective hydrodesulfurization (HDS) of FCC gasoline is a key catalytic process for reducing sulfur content in gasoline. In the present work, we focus on the effect of H2O amount alone or in mixture with CO on the transformation of a model FCC gasoline composed of 2-methylthiophene (2MT) and 2,3-dimethylbut-2-ene (23DMB2N) molecules, over an alumina supported CoMoS catalyst. A negative impact of water and CO on the conversion of 2MT and 23DMB2N is found. However the effect in the presence of CO is much stronger. The comparison of Density Functional Theory (DFT) calculations of CO and water adsorption on the S- and M-edge sites of the CoMoS slabs shows a significantly stronger CO adsorption energy than water adsorption energy. When CO and water were introduced simultaneously, the negative impact observed in the transformation of the model feed is mainly due only to the presence of CO. However whatever the oxygenated molecules used and their amount, no impact in the selectivity measured by the ratio between the activity in hydrodesulfurization and in hydrogenation is observed

ASAXS Study of the Influence of Industrial Sulfidation Conditions and of Organic Additives on Sulfide Slabs Distribution

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Deep hydrodesulfurization of FCC gasoline and gas oil cuts: Comparison of CO effect, a by-product from biomass

International audienceRegarding the composition of the various feedstocks which should be hydrotreated inorder to obtain fuels with amount of sulfur less than 10 wt ppm, we have shown that thepresence of traces of CO, a by-product from lignocellulosic biomass feedstock conversion,inhibited the transformation of model compounds representative of FCC gasolines and gasoils over CoMo-based sulfide catalysts. Thus, this effect is more significant in the presenceof 2-methylthiophene and 2,3-dimethylbut-2-ene representative of a FCC gasoline than inthe presence of dibenzothiophene and 4,6-dimethyldibenzothiophene representative of astraight run gas oil, even if the operating conditions are not the same. This effect isattributed to phenomena of competitive adsorption between sulfur compounds, alkenesand CO on the catalyst surface

Sensitivity of supported MoS 2 -based catalysts to carbon monoxide for selective HDS of FCC gasoline: Effect of nickel or cobalt as promoter

International audienceThe impact of CO, a by-product of biomass transformation, on the transformation of a model FCC gasolinecomposed of 2-methylthiophene (2MT) and 2,3-dimethylbut-2-ene (23DMB2N) molecules, over MoS2based catalyst supported over alumina was investigated. More specifically, the effect of the presence andthe type of the promoter (Ni or Co) was studied. A gain in activity in HDS of 2MT and hydrogenationof olefins has been confirmed in the presence of the catalysts promoted by cobalt or nickel. However,surpringly, depending on the promoter (Ni or Co), the effect of the presence of CO is really different. Infact, while the carbon monoxide has a significant negative impact on the CoMoS/Al2O3catalyst for thetransformation of model molecules, no effect is observed for other catalysts. These differences could beattributed to a lower adsorption energy of CO on the non-promoted catalyst and promoted by nickelrelative to the catalyst promoted by cobalt as calculated

Ischaemic skin lesions with multi-organ failure due to cocaine intake.

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Regeneration of an aged hydrodesulfurization catalyst : Conventional thermal vs non-thermal plasma technology

International audienceThis study compares the regeneration efficiency of an aged industrial hydrodesulfurization catalyst (CoMoP/Al2O3) by conventional and alternative routes: thermal oxidation versus non-thermal plasma technology (NTP). Spent, partially, and fully regenerated catalysts have been characterized by XRD, XPS, and toluene hydrogenation to measure hydrogenating activity. Complete regeneration of the HDS catalyst via NTP requires the heating of the dielectric barrier discharge plasma reactor. Total removal of coke is obtained from 250 °C by applying only 8.6 W/gcatalyst, against 400 °C by conventional thermal treatment. The hydrogenation activity of the regenerated catalyst by NTP assisted by temperature is higher than that obtained by traditional thermal regeneration practiced industrially. Plasma treatment mitigates the oxide sintering but leads to the formation of cobalt oxide species preventing Co of fully playing its role as MoS2 slabs promoter. HDS catalyst regeneration using non-thermal plasma assisted by low temperature appears as a promising alternative to thermal combustion

Influence of the Ageing and Drying Steps of a CoMoP/γ‐Al2O3 Catalyst onto the Multi‐Scale Molybdenum Active Phase Organization

International audienceTo study the influence of ageing and drying steps onto the multiscale Mo active phase arrangement (i. e. MoS2 slabs and slab aggregates), a series of highly loaded CoMoP/γ-Al2O3 catalysts aged, unaged, dried or freeze-dried were prepared and tested in toluene hydrogenation. Electron Probe Micro Analyses(EPMA) and Anomalous Small Angle X-Ray Scattering (ASAXS) permit to highlight the influence of each preparation steps. A growth of Mo entities occurs during ageing along with metal diffusion inside the support and leads to longer slabs. The same occurs during drying with metal redistribution due to solvent evaporation. Concomitantly, a fragmentation of slab aggregates takes place and leads to numerous small slabs aggregates. Slab length and aggregates amount were found to drive the catalytic activity, which translates the relationship between activity, number of active sites and their accessibility. Conversely,macroscopic metal distribution into the extrudates appears to have no impact on the catalytic performance