Carbon ‐ Supported Transition Metal Sulfides

Vissers, Jpr; Groot, C.; Oers, E.M. van; Beer, V.H.J. de; Prins, R.

doi:10.1002/bscb.19840930822

Cited by 162 publications

(29 citation statements)

References 11 publications

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“…The decomposition of the Re 4f spectrum is well documented in the literature and consists of two doublet contributions. The major one attributed to ReS 2 has a binding energy at 41.7-41.9 eV for Re 4f 7/2 in agreement with previous published values [5,21]. The second contribution, with a binding energy Re 4f 7/2 circa 43.0 eV, was attributed to some oxy-rhenium sulfide species [22].…”

Section: Xps Resultssupporting

confidence: 84%

Unexpected Support Effect in Hydrotreating: Evidence of a Metallic Character for ReS2/Al2O3 and ReS2/SiO2 Catalysts

et al. 2011

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Rhenium sulfide based catalysts were prepared by the incipient wetness impregnation method over alumina and silica supports and evaluated for 4,6-dimethyldibenzothiophene hydrodesulfurization in a high-pressure stirred-tank reactor. The catalyst prepared over silica was about six times more active for hydrodesulfurization than the corresponding catalyst prepared over alumina and a NiMo/Al 2 O 3 industrial reference catalyst. This surprising and positive SiO 2 support effect was explained by a metallic character of the supported sulfide, which was demonstrated using a kinetic approach of competitive hydrogenations and by XPS characterization.

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Section: Xps Resultssupporting

confidence: 84%

Unexpected Support Effect in Hydrotreating: Evidence of a Metallic Character for ReS2/Al2O3 and ReS2/SiO2 Catalysts

et al. 2011

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“…The fact that the Pt/SI wafer and the PVSiO2 catalyst give the same relatively high S/Pt ratioafter suiphiding favours the formation of a compound, probably a very sulphur deficient form of PtS. Interestingly we have previously obtained [15] a similar stoichiometry following sulphidation of PdO2 with 10% H2S/H2 with BE again lower than reported for carbon supported Pd [12]. This lends support to the view that these materials tend to form highly reduced suiphides at the conditions used.…”

Section: Platinumsupporting

confidence: 41%

“…In a previous publication Vissers et ai. [12] reported the formation of PtS on carbon supported catalysts sulphided at similar conditions. The Pt4f BE were slgnlflcantly higher than reported here and the S2p/Pt4f intensity ratio was more than double the present value.…”

Section: Platinummentioning

confidence: 89%

“…The Pt4f envelope from the untreated sample corresponds to Pt in more than one oxidation state. The BE reported in literature for PtCi4 is 75.5 eV while those associated with oxide related species range from 72.6 eV, reported for Pt(OH)2, to 75.5 eV, reported for Pt02 [12]. The Pt4f envelope from the untreated sample could well indude contributions from oxide/hydroxide species, probably formed from water adsorption by the hygroscopic PtC14 (small amounts of oxygen associated with Pt would not be distinguishable from the large signal from the 9 0 2 ) .…”

Section: Platinummentioning

confidence: 91%

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Cyclic Sulphidation/Reduction of Transition Metal Model Compounds: A Quasi in situ XPS Study

Oen

Hellgardt

Chadwick

1995

Bulletin des Soc Chimique

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INTR OD UCTlONAs the allowable level of sulphur in refinery products is reduced, the H2S concentrations to which catalysts are exposed during the final stages of hydrotreating can be expected to decrease. Although the precise H2S/H2 ratio will be dependent on the reactor configuration, this may lead to loss of sulphur from the catalyst surface with consequent effects on catalyst structure and activity. This problem Is likely to be more acute for catalysts based on precious metals with their potential use for deep desulphurization, slnce thermodynamic calculations suggest, for example, that Pt and Re sulphides are reducible in H2 atmospheres containing less than 1 % H2S [l ,2,3] whereas base metals show greater stability of their sulphldes towards reduction by H2.Studies of the sulphidation of hydrotreating catalysts show that their activlty depends on several factors. Coupled or stepwise sulphidatlon/reduction seems to yield the most active catalysts (41, but other factors also affect the final performance. For example, oxygen incorporation in the sulphided catalyst can give sites of higher activii [5], and reduction after sulphidation can give either higher acti-The present study forms part of a programme of research to probe the surface compositions of the suiphided state of various transition metal model compounds after cyclic treatments simulating low H2S concentration hydrotreating conditlons and resulphldation. For this task a quasi in situ XPS system has been built to allow measurement of surface sulphurlmetal ratios of transition metals after various cyclic treatments of the same sample without air exposure. This work concentrates on the precious metals Pt and Re, as well as Mo and Fe. These materials were investigated as thin films on Si wafers, as SiO2 supported catalysts in the case of Pt and Re, and as bulk materials in some cases. EXPERIMENTALFor this study a gas-cell-type reactor was constructed in the preparation vessel of a Vacuum Generators ESCA 111 XPS Instrument. Cyclic treatments and surface analysis were performed on the same sample without air contactlng the sample between treatment and analysis. A sketch of the reactor set-up is given in Figure 1. The sample is held on the end of a movable probe and the reactor hangs from a bellows system. For sample treatment, the reactor is lowered down onto a support, the sample is moved into the reactor and sealed with a metal gasket. Further details of the reactor construction and performance can be found in another publication [7]. XPS spectra were taken using Mg or A1 radiation and binding energles were referenced to the Cls binding energy of 264.6 eV or cross-referenced to Si2p312 at 103.2 eV in some cases. For the Mo/Si wafer and the MoS2 single crystal, the S2p was set at 162.0 eV, corresponding to the average of a range of values taken from literature [8,9]. This is discussed further below. Constant spectrometer pass energies of 50 or 20 eV were applied.

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“…It is suggested the nature of these sites is intimately related to the metal-sulfur bond strength [16][17][18][19]. Basic studies support the idea that differences between catalytic activity is related to variations in the concentration of CUS (the Lewis acid sites), which in turn depend on the metal-sulfur bond strength [20][21][22][23][24][25][26][27][28][29][30][31]. Nickel (and cobalt)-promoted molybdenum sulfide catalysts have for many years been regarded as being among the most important catalysts used in refineries.…”

Section: An Application To Nanocatalyts -Exploring the Structure Of Tmentioning

confidence: 92%

Atoms in Molecules Theory for Exploring the Nature of the Active Sites on Surfaces

Aray¹,

Rodríguez²,

Vega³

2007

The Quantum Theory of Atoms in Molecules

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The atoms in molecules theory provides a rigorous definition of chemical bonds for all types of molecules and solids [1][2][3][4][5][6][7][8][9][10] and has proven useful in analysis of the physical properties of insulators, pure metals, and alloys [4][5][6][7][8]. In particular, it has been observed that the strength of the bonding between a given pair of atoms in a molecule correlates with the values of the electron density at the bond critical point, r b [1]. A simple relationship between the binding energy and r b in periodic solids has also been reported [4,6,8]. The AIM theory also leads to unique partition of three-dimensional space into a collection of chemically identifiable regions called atomic basins (the atoms in a molecule or in a crystal). These are the most transferable pieces one can define in exhaustive partitioning of the real space [1]. In this chapter we describe the implementation of an algorithm that uses the r(r) topological information to determine the main elements of the AIM theory for periodic systems, and discuss an application to nanocatalysis. Implementing the Determination of the Topological Properties of r(r) from a Three-dimensional GridThe CPs are usually calculated using the Newton-Raphson (NR) technique [11]. The NR algorithm starts from a truncated Taylor expansion at a point r ¼ r 0 þ h, about r 0 of a multidimensional scalar function ð'rðrÞÞ:where H is the Hessian (the Jacobian of 'rðrÞÞ at point r 0 . The best step, h, to move from the initial r 0 to the CP is h ¼ ÀH À1 'rðr 0 Þ. This correction is then used to obtain a vector r new ¼ r old þ th (t is a small value) and the process is iter- 231The Quantum Theory of Atoms in Molecules. Edited

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Carbon ‐ Supported Transition Metal Sulfides

Cited by 162 publications

References 11 publications

Unexpected Support Effect in Hydrotreating: Evidence of a Metallic Character for ReS2/Al2O3 and ReS2/SiO2 Catalysts

Unexpected Support Effect in Hydrotreating: Evidence of a Metallic Character for ReS2/Al2O3 and ReS2/SiO2 Catalysts

Cyclic Sulphidation/Reduction of Transition Metal Model Compounds: A Quasi in situ XPS Study

Atoms in Molecules Theory for Exploring the Nature of the Active Sites on Surfaces

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