Photocatalytic synthesis of dioctylsulfide has been performed at room temperature in liquid phase by addition of 1-octanethiol on 1-octene in contact with illuminated TiO2. Under inert atmosphere, dioctylsulfide is selectively obtained whereas in the presence of oxygen high selectivity in n-dioctylsulfide has vanished. This study illustrates the potential of photocatalysis for the production of thio-compounds.

Following the numerous and contradictory results reported in the literature about the origin of the different functionalities of MoS2 based catalysts, an approach using the 4,6-dimethyldibenzothiophene as a probe molecule is reported. That has been done by the study of the variations of selectivities during poisoning of 4,6-DMDBT HDS (using olefin, aromatics and nitrogen containing compounds), and by a careful study of the variations of selectivities during the transformation of 4,6-DMDBT over fresh and aged catalysts.The ratio of selectivities between the hydrogenation (HYD) and the direct desulfurization (DDS) routes are found to be the same whatever the inhibiting compound and the aging has the same effect on both routes of reaction. These results will be discussed assuming adsorptions on the same type of sites (uncoordinated molybdenum atom) and a general mechanism will be proposed. (c) 2005 Elsevier B.V. All rights reserved.

Mesoporous titanium oxide with a high specific surface area of 120m2/g prepared by a novel method developed by Chiyoda was used for supporting molybdenum sulfide. In order to examine the influence of the surface area on the properties of the molybdenum sulfide phase, two different samples of titanium oxide were studied, a commercial one with a surface area of 72m2/g and that prepared by Chiyoda. Molybdenum was deposited on the TiO2 supports by incipient wetness impregnation with ammonium heptamolybdate in one or two steps depending on the Mo loading. Some samples were also prepared by impregnation of ammonium heptamolybdate basified by ammonia. Raman spectroscopy and XPS were used to examine the nature of the molybdate phase and its dispersion in the oxidic state. HREM and XPS were used for studying the sulfided state. As expected, the maximum amount of well-dispersed molybdenum is higher on the Chiyoda support than on the reference support with a lower surface area. The catalytic properties of the catalysts were studied in dibenzothiophene conversion. For the Chiyoda support, the catalytic activity varied linearly with the Mo loading up to 6–7 Mo/nm2 then became nearly constant for the higher loadings. Much higher activities (six times, expressed per gram of catalyst) were obtained compared to molybdenum sulfide supported on alumina.

Niobium-molybdenum disulfide solid solution (NbxMo1−xS2) 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 NbxMo1−xS2 solid solution (HDS of DBT, Ptot=33bar) is not decreased in the presence of H2S up to p(H2S)=200Torr, at least up to x=0.4.

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.

(Ni)W/ZrO2 oxide catalysts have been prepared using reactions in molten Na(K)NO3 fluxes at different temperatures ranging from 350 to 500°C. The solids were characterized using X-ray diffraction (XRD), textural measurements and X-ray photoelectron spectroscopy (XPS). Highly dispersed zirconia with tungstate species grafted on its surface was formed at 450–500°C. At 350–400°C tungsten oxide or crystalline intermediate polytungstates of K and Na were observed in the products. Specific surface areas of the solids were high, up to 250m2/g, due to stabilizing effect of tungstate species. After sulfidation, the catalysts were studied by XPS in situ, and tested in the model reactions of hydrodesulfurisation (HDS) and hydrogenation (HYD). XPS study reveal incomplete sulfidation of tungsten even at 500°C, suggesting some persistent Zr–O–W bonds. Compared with conventional impregnation NiMo/Al2O3 systems, the (Ni)W/ZrO2 solids showed increased hydrogenating activity.

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 0.25–0.5wt.% 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.

The objective of this work was the study of the hydrodesulphurization (HDS) catalytic properties of the nickel Chevrel phase NixMo6S8 in a highly dispersed state. Since Chevrel phases are not soluble, new synthesis routes were developed on bulk materials from soluble precursors and then applied for the preparation on a porous support. The method is a two-step gas over solid thermal process: sulfurization under H2S/H2 and then reduction under H2. The first step corresponds to the classical preparation of NixMoS2 on alumina industrial hydrotreating catalyst. XRD, TEM and catalytic activity measurements allowed us to determine the preparation parameters leading to the synthesis of NixMo6S8 nanometric particles on alumina (φ<5 nm).

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 H2S shows a maximum of sulphur resistance for the Pd20Pt80 atomic composition.

Bimetallic Pd–Pt clusters produced by laser vaporization of bulk alloy have been deposited on high surface alumina. Energy dispersive X-ray (EDX) analysis and transmission electron microscopy (TEM) show that they have a perfectly well-defined stoichiometry and a narrow range of size. Therefore, they constitute ideal systems to investigate alloying effects towards reactivity. Pd–Pt alloys are already known for their applications in the hydrogenation of unsaturated hydrocarbons, especially aromatics, because this system is highly resistant to sulfur and nitrogen poisoning. In this context, the catalytic properties of this system have been investigated in the hydrogenation of tetralin in the presence of hydrogen sulfide. Preliminary results show that this model catalyst is more sulfur-resistant than each of the pure supported metals prepared by chemical methods.

The properties of hydrotreating catalysts (Ni–Mo)/ZrO 2 –Cr 2 O 3 containing either 10 or 90 mol% of Cr 2 O 3 have been studied in the model reactions of thiophene hydrodesulfurisation (HDS) and tetralin hydrogenation (HYD). Catalysts were characterized by X‐ray diffraction, UV‐visible spectroscopy and measurements of textural properties. It has been shown that the presence of chromium in the NiMo/ZrO 2 systems makes them more hydrogenating, because of the formation of chromium sulphide Cr 2 S 3 . Mixed hydrous or crystalline oxide Cr–Zr can be sulfided under mild conditions (400°C, H 2 S/H 2 ) leading to highly dispersed Cr 2 S 3 which is impossible for individual Cr 2 O 3 . Such systems are several times more active in HYD of tetralin than industrial NiMo/Al 2 O 3 reference catalyst. At the same time in the presence of chromium, the synergy of catalytic activity between Ni and Mo in the reaction of HDS of thiophene was lowered, apparently because of hindering of formation of mixed sulfide Ni–Mo–S active sites due to the stronger interaction between Ni and Cr species than that of Ni and Mo.

The reactivity of a series of amines with various structures and different numbers of hydrogen atoms on the carbon atoms in the α and β position, with respect to the nitrogen atom, was examined on four transition metal sulfides, i.e. NbS3, MoS2, RuS2, and Rh2S3. It is shown that the reaction mechanism proceeds via an elimination or a nucleophilic substitution the relative importance of which depends on the structure of the substrate to be transformed and on the transition metal sulfides properties. NbS3is the most active sulfide of the series for the elimination reaction due to its high acidity, but it is inactive for the nucleophilic substitution. On the other hand, the surface species of Rh2S3can be involved in a nucleophilic substitution but not in an elimination reaction. The other sulfides of the series behave in between. These results clearly demonstrate that the catalysts intervene differently in the HDN mechanism. Moreover, for a given solid the structure of a nitrogen-containing molecule strongly affects the elementary steps of its transformation. Accordingly, a precise mechanistic study of the reactivity of a model molecule at the surface of a sulfide cannot be generalized to the overall HDN process which involves several types of molecules.

Catalysts of ruthenium sulfide, dispersed in a series of Y zeolites with various acidic properties, were prepared by ion exchange and subsequent sulfidation. The activities for the reactions of hydrogenation of tetralin and toluene, carried out in the presence of H2S (1.9%), vary widely according to the nature of the zeolites. Ruthenium sulfide catalysts are much more active when using acidic zeolite, HY and HYd (dealuminated), and a partially potassium-exchanged KHYd sample, than when using the KY support. The acidic properties of the sulfided RuY catalysts were determinedin situusing infrared spectroscopy and the conversion of isooctane. Both methods gave similar rankings of catalyst acidity. The electronic properties of the ruthenium sulfide phase were examined by means of the infrared study of the adsorption of CO. A low-frequency shift of 15 cm−1was observed for CO adsorbed on RuKY by reference to CO adsorbed on all other samples. The increase in activity for the hydrogenation of aromatics is related to the electron-deficient character of the sulfide particles in the acidic zeolites as has been proposed, in the literature, for metal catalysts. A superimposed influence of the acidic sites on the adsorption of the aromatic molecule may also occur which could explain the amplitude of the effect (difference of activity between the most and less active catalysts ∼200 times) and the variations of activity observed within the series of the acidic catalysts.

Catalysts of ruthenium sulfide supported in a dealuminated KY zeolite were prepared by ion exchange and subsequent sulfidation using several atmospheres containing sulfur. They were characterized by means of HREM, EDX, TPR, and EXAFS. The activity for the tetralin hydrogenation, carried out in presence of large amounts of H2S (1.85%), was very high and roughly 300 times the activity (expressed per metal atom) of an industrial NiMo/Al2O3hydrotreating catalyst. A simple modeling of the results obtained by the physicochemical techniques suggests that the active phase consists of clusters of less than 50 ruthenium atoms of a ruthenium sulfide-like phase with very small domains of ruthenium metal.

Hydrogenation of tetralin at 300 degrees 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/H-2 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.

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 RuAl2O3 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.

Bulletin des Sociétés Chimiques BelgesVolume 104, Issue 4-5 p. 213-218 Article CONVERSION OF NITROGEN CONTAINING MOLECULES IN THE PRESENCE OF MIXTURE OF NICKEL MOLYBDENUM SUPPORTED ON ALUMINA AND RUTHENIUM SULFIDE DISPERSED IN A KY ZEOLITE J. L. Zotin, J. L. Zotin Institut de Recherches sur la Catalyse, CNRS, 2, avenue Albert Einstein, 69626 Villeurbanne, FranceSearch for more papers by this authorM. Cattenot, M. Cattenot Institut de Recherches sur la Catalyse, CNRS, 2, avenue Albert Einstein, 69626 Villeurbanne, FranceSearch for more papers by this authorJ. L. Portefaix, J. L. Portefaix Institut de Recherches sur la Catalyse, CNRS, 2, avenue Albert Einstein, 69626 Villeurbanne, FranceSearch for more papers by this authorM. Breysse, M. Breysse Institut de Recherches sur la Catalyse, CNRS, 2, avenue Albert Einstein, 69626 Villeurbanne, FranceSearch for more papers by this author J. L. Zotin, J. L. Zotin Institut de Recherches sur la Catalyse, CNRS, 2, avenue Albert Einstein, 69626 Villeurbanne, FranceSearch for more papers by this authorM. Cattenot, M. Cattenot Institut de Recherches sur la Catalyse, CNRS, 2, avenue Albert Einstein, 69626 Villeurbanne, FranceSearch for more papers by this authorJ. L. Portefaix, J. L. Portefaix Institut de Recherches sur la Catalyse, CNRS, 2, avenue Albert Einstein, 69626 Villeurbanne, FranceSearch for more papers by this authorM. Breysse, M. Breysse Institut de Recherches sur la Catalyse, CNRS, 2, avenue Albert Einstein, 69626 Villeurbanne, FranceSearch for more papers by this author First published: 1995 https://doi.org/10.1002/bscb.19951040406Citations: 7AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume104, Issue4-51995Pages 213-218 RelatedInformation