Martine Cattenot

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.

Enhancement of the catalytic properties of NiMo and CoMo alumina-supported sulfide catalysts by addition of ruthenium sulfide dispersed in Y zeolites

Abstract Y zeolite- or alumina-supported ruthenium sulfide catalysts were investigated for the hydrogenation of pyridine to piperidine. Their activity was compared with that of commercial NiMo or CoMo alumina-supported catalysts and they were found to be more active than the latter. RuKY exhibited higher intrinsic activities than RuHY and Ru Al 2 O 3 catalysts. Mechanical mixtures consisting of RuKY and commercial alumina-supported NiMo- or CoMo-based catalysts exhibited synergy for the hydrogenation of pyridine. This phenomenon was not observed for the other supports. This observation is related to the particular ability of highly dispersed ruthenium sulfide for hydrogen activation.

Promoting effect of ruthenium on NiMo/Al2O3 hydrotreating catalysts

Abstract Ruthenium (Ru) has been tested as a dopant for NiMo on alumina catalyst. A promotion effect is observed for the hydrodesulfurization (HDS) of dibenzothiophene (DBT), and the hydrogenation (HYD) of tetralin. Maximum activity is obtained at a loading in the range of 0.25–0.5xa0wt.% Ru added to a NiMo catalyst. Temperature programmed reduction (TPR) and TEM were used to characterize the catalysts. The possibility to create a mixed decorated site (NiRu)MoS was investigated by varying the Ni/Ru atomic ratio. Substitution of Ni atoms by Ru may explain the promoting effect.

Hydrotreating properties of mixed NbxMo1−xS2 alumina supported catalysts

Abstract Niobium-molybdenum disulfide solid solution (Nb x Mo 1− x S 2 ) has been prepared in a dispersed state on gamma alumina. The existence of this solid solution supported on alumina carrier has been proven with the help of EXAFS technique. The catalytic properties of these materials have been studied in hydrogenation and hydrodesulfurization reactions. Interestingly, as already observed for niobium sulfide, the activity of the Nb x Mo 1− x S 2 solid solution (HDS of DBT, P tot =33xa0bar) is not decreased in the presence of H 2 S up to p (H 2 S)=200xa0Torr, at least up to x =0.4.

Sulphur resistant palladium-platinum catalysts prepared from mixed acetylacetonates

Well-defined mixed acetylacetonates precursors were synthesised on a silica support and identified by their X-ray differaction spectra. After a calcination treatment to decompose the ligands and a reduction in hydrogen, bimetallic particles of 3.5 to 5 nm have been obtained. Analytical microscopy shows that these catalysts have a perfectly homogeneous composition. Low energy ion scattering experiments show that the surface of the particles is palladium enriched, as expected from Monte Carlo simulations. However, in the simple hydrogenation of cyclooctadiene to cyclooctene, where Pd is two orders of magnitude more active than Pt, it is observed that the rate is not proportional to the Pd surface concentration. This is interpreted as an ensemble effect on the chemisorption of the reactant. A study of the hydrogenation of tetralin in the presence of H 2 S shows a maximum of sulphur resistance for the Pd 20 Pt 80 atomic composition.

Hydrogenation of tetralin over a sulfided ruthenium on Y zeolite catalyst: comparison with a sulfided NiMo on alumina catalyst

Hydrogenation of tetralin at 300°C, under hydrogen pressure, and in the presence of hydrogen sulfide was used to modelize the hydrogenation of aromatics in gasoils. The activity for this reaction of a sulfided ruthenium on dealuminated Y zeolite catalyst (RuKYd), was found to be much higher than that of a sulfided NiMo on alumina. Moreover, the activity of the RuKYd catalyst was dependent very much on the sulfidation method: owing to a very significant carbon deposition initiated by the zeolite acid sites, the catalyst sulfided by dimethyldisulfide in solution in n-heptane was less active than when sulfided by a H2S/H2 mixture. This effect was not observed in the case of the NiMo/alumina catalyst, which is not acidic. On the other hand, whatever the catalyst, the presence of n-heptane as a solvent during the hydrogenation test decreased significantly the conversion of tetralin. This was due to the competitive adsorptions between the two molecules.