Binary sulfides formation

The IR spectra in Fig.7 indicate the preferential adsorption of NO on the Co sites. It may be conjectured that the Mo sulfide species are physically covered by the Co sulfide species or that Co-Mo mixed sulfide species are formed and the chemical natures of the Co and Mo sulfides are mutually modified. The Mo K-edge EXAFS spectra were measured to examine the formation of mixed sulfide species between Co and Mo sulfides. The Fourier transforms are presented in Fig.8 for MoSx/NaY and CoSx-MoSx/NaY. The structural parameters derived from EXAFS analysis are summarized in Table 1. The structure and dispersion of the Mo sulfides in MoSx/NaY are discussed above. With the Co-Mo binary sulfide catalyst, the Mo-Co bondings are clearly observed at 0.283 nm in addition to the Mo-S and Mo-Mo bondings. The Mo-Co distance is close to that reported by Bouwens et al. [7] for a CoMoS phase supported on activated carbon. Detailed analysis of the EXAFS results for CoSx-MoSx/NaY will be presented elsewhere. It is concluded that the Co-Mo mixed sulfides possessing Co-S-Mo chemical bondings are formed in CoSx-MoSx/NaY. 

For aspects of complex formation it is important to realize that thiometalates are not very stable in aqueous solution, especially at low pH. Their decomposition may be caused by hydrolysis to oxometalates, by intramolecular redox processes, or by their marked tendency to form sulfides. With molybdates and tungstates the stability decreases with increasing oxygen content and increasing electron density on the ligands. When they decompose in acid media, binary sulfides (or with selenometalates, selenides) such as MoS3 are formed. 

Theberge SM, Luther GW, Rozan TF, Rickard DT (2000) Evidence for aqueous clusters as intermediates during copper sulfide formation. Abstr Am Chem Soc 220 353 Thompson DN, Sayer RL, Noah KS (2000) Sawdust-supported passive bioremediation of western United States acid rock drainage in engineered wetland systems. Minerals Metall Process 17 96-104 Tolman RC (1966) Consideration of Gibbs theory of surface tension. J Chem Phys 16 758-774 Tolman RC (1949) The effect of droplet size on surface tension. J Chem Phys 17 333-337 Tomino H, Kusaka I, Nishioka K, Takai T (1991) Interfacial tension for small nuclei in binary nucleatioa J Crystal Growth 113 633-636... 

Crystal structure plays a secondary role in catalysis by the Transition Metal Sulfides. As the periodic trends for HDS of the binary sulfides shows the dominant effect is which transition metal is present in the reaction, this transition metal takes on the structure and stoichiometry of the phase which is most stable in the sulfur containing catalytic environment. The unsupported promoted catalyst systems can be grouped into "synergic" pairs of sulfides. Because these pairs are related to the basic periodic trends of the binary Transition Metal Sulfides through average heats of formation. 

Isoprene [78-79-5] (2-methyl-1,3-butadiene) is a colorless, volatile Hquid that is soluble in most hydrocarbons but is practically insoluble in water. Isoprene forms binary azeotropes with water, methanol, methylamine, acetonitrile, methyl formate, bromoethane, ethyl alcohol, methyl sulfide, acetone, propylene oxide, ethyl formate, isopropyl nitrate, methyla1 (dimethoxymethane), ethyl ether, and / -pentane. Ternary azeotropes form with water—acetone, water—acetonitrile, and methyl formate—ethyl bromide (8). Typical properties of isoprene are Hsted in Table 1. 

Treatment of the rhenium sulfide chlorides with an excess of chlorine at temperatures above 450°C results in formation of ReCls 140). Reduction between 350 and 500°C gives binary rhenium chalcogenides 139,262). Action of water vapor on rhenium sulfide chlorides at 350-500°C produces oxysulfides 139). 

Figure 7.15 (a) Enthalpy of formation of ternary oxides and nitrides from their binary constituent compounds as a function of the ratio of ionic potential [16]. Reprinted with permission from [16] Copyright (1997) American Chemical Society, (b) Gibbs energy of the oxide-sulfide equilibrium for group 1 and 2 metals at 1773 K as a function of the optical basicity of the metal. 

More recent research has focused on the binary Ru sulfides and selenides. Schulenberg et al. showed that modifying a Ru/C with Se (via H2Se03) improved activity by a factor of three. It was concluded that the Se inhibited surface oxide formation that limits active sites with Ru/C. Both catalysts showed some H2O2 formation at lower potentials (e.g., 3% at... 

Appendix 2 was compiled and formatted by eomposition paralleling the presentation for the fibrous minerals. The list, in eontrast with that of the minerals, shows a predominanee of simple chemical compounds that combine two or three elements. One-third of the reeorded synthetie fibers are of elements or binary alloys. Another third are compounds such as sulfides, phosphides, and halides that do not eontain oxygen (Table 2.9). Only three synthetic fibrous silicate compounds etre listed, although undoubtedly other experimental silicate combinations have been made but not recorded by us. 

The oxidation of phosphorus by elemental sulfur to give binary phosphorus sulfides, which is initiated by mild heating (<100 °C) or upon photolysis at 0 °C, may involve the formation of the catenaS biradical in the rate-determining first step. ... 

The Group 2 thioacetate compounds, M(SOCMe)2L, have been studied as single-source precursors for the formation of binary Group 2 metal sulfides, MS. The rationale to investigate these compounds is that if the reaction pathway involves thermally induced elimination of thioacetic anhydride according to Eq. (32), then the metal sulfide film should be relatively pure. 

Differences in the cohesive energy between Nb and Ta give rise to the formation of a bundle of (Nb, Ta)-rich sulfides without counterparts in the corresponding binary M-S systems. The phase richest in metal of this class has been identified as NbxTa7 xS2. (Nb, Ta)7S2 is an excellent example of a mixed niobium-tantalum-rich sulfide without counterpart in the adjoining binary systems. Its structure differs... 

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