Sulfides transition metal

Direct splitting requires temperatures above 977°C. Yields of around 30% at 1127°C are possible by equiUbrium. The use of catalysts to promote the reaction can lower the temperature to around the 327—727°C range. A number of transition metal sulfides and disulfides are being studied as potential catalysts (185). Thermal decomposition of H2S at 1130°C over a Pt—Co catalyst with about 25% H2 recovery has been studied. 

The red tetrathiomolybdate ion appears to be a principal participant in the biological Cu—Mo antagonism and is reactive toward other transition-metal ions to produce a wide variety of heteronuclear transition-metal sulfide complexes and clusters (13,14). For example, tetrathiomolybdate serves as a bidentate ligand for Co, forming Co(MoSTetrathiomolybdates and their mixed metal complexes are of interest as catalyst precursors for the hydrotreating of petroleum (qv) (15) and the hydroHquefaction of coal (see Coal conversion processes) (16). The intermediate forms MoOS Mo02S 2> MoO S have also been prepared (17). 

The performance of VASP for alloys and compounds has been illustrated at three examples The calculation of the properties of cobalt dislicide demonstrates that even for a transition-metal compound perfect agreement with all-electron calculations may be achieved at much lower computational effort, and that elastic and dynamic properties may be predicted accurately even for metallic systems with rather long-range interactions. Applications to surface-problems have been described at the example of the. 3C-SiC(100) surface. Surface physics and catalysis will be a. particularly important field for the application of VASP, recent work extends to processes as complex as the adsorption of thiopene molecules on the surface of transition-metal sulfides[55]. Finally, the efficiciency of VASP for studying complex melts has been illustrate for crystalline and molten Zintl-phases of alkali-group V alloys. 

We have already referred to the Mo/Ru/S Chevrel phases and related catalysts which have long been under investigation for their oxygen reduction properties. Reeve et al. [19] evaluated the methanol tolerance, along with oxygen reduction activity, of a range of transition metal sulfide electrocatalysts, in a liquid-feed solid-polymer-electrolyte DMFC. The catalysts were prepared in high surface area by direct synthesis onto various surface-functionalized carbon blacks. The intrinsic... 

Trapp V, Christensen PA, Hamnett A (1996) New catalysts for oxygen reduction based on transition-metal sulfides. J Chem Soc Earaday Trans 92 4311 319... 

Reeve RW, Christensen PA, Dickinson AJ, Hamnett A, Scott K (2000) Methanol-tolerant oxygen reduction catalysts based on transition metal sulfides and their appheation to the study of methanol permeation. Electrochim Acta 45 4237-4250... 

This work is a contribution to the understanding of the effect of spillover hydrogen in a type of catalyst of considerable industrial importance, namely that composed of transition metal sulfides and amorphous acidic solids. This is typically the case of sulfided CoMo supported on silica-alumina used for mild hydrocracking. 

With other transition metal sulfides the mixed vanadium-silver cubane-like cluster, (Et4N)2[Ag2V2S4 S2CN(OC4H8)2 2(SPh)2] (166)1092 and [ y-C5Me5)WS3 2Ag3 (PPh3)3]N03 (167), have been reported.1093... 

Chianelli, R. R., and Berhault, G., Symmetrical synergism and the role of carbon in transition metal sulfide catalytic materials. Catal. Today, 1999. 53 pp. 357-366. 

Khramov, M.I. and Parmon, V.N. (1993) Synthesis of ultrafine particles of transition-metal sulfides in the cavities of lipid vesicles and the light-stimulated transmembrane electron-transfer catalyzed by these particles. Journal of Photochemistry and Photobiology A-Chemistry, 71, 279-284. 

L121 Th. Weber, R. Prins and R.A. van Santen (Eds.), Transition Metal Sulfides Chemistry and Catalysis, Kluwer, Dordrecht, 1998. 

Eichorn, Bryan W., Ternary Transition Metal Sulfides. 42 139... 

K), Fe-S cluster assembly (nIfM) and the biosynthesis of the iron molybdenum cofactor, FeMo-co (nifN, B, E, Q, V, H)(5a). It is the last two functions, involving the placement of unusual transition metal sulfide clusters into the nitrogenase proteins, that cause nitrogenase and its components to be appropriately included in this symposium. 

This caveat notwithstanding, the Dominant Hypothesls( ) designates [FeMo] as the protein responsible for substrate reduction. The FeMo protein contains an 02fi2 subunit structure due to expression of the nifD and nlfK genes(24,25). Its overall M.W. of about 230,000 reflects the 50-60,000 M.W. of each of its four subunits. The nonprotein composition of 30 Fe, 2 Mo, and 30 s2- betokens the presence of transition metal sulfide clusters, which are presumed to be the active centers of the protein. 

Transition metal sulfide units occur in minerals in nature and play an important role in the catalytic activity of enzymes such as hydrogenase and nitrogenase. Industrial processes use transition metal sulfides in hydroprocessing catalysis. Both the metal and the sulfur sites in these compounds can undergo redox reactions which are an important part of their reactivity. Thus, the electronic situation of the ReS4 anion and related complexes is of considerable interest and has been evaluated applying quantum chemical methods. 

Attempts were made to utilize transition-metal sulfides as cathodes in SBs. These sulfides, and especially those of Ti, are electrochemically actiye and reyersible in cells such as that based on Li and TiS in a LiAlCli -propylene carbonate electrolyte. More than 80 cycles were performed with TiS2, it was reported (43a). Eleyen hundred shallow (4%) cycles were reported later (43b). 

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