Oxidation of CS

The products of the oxidation of carbon disulfide include SO2, S2O, CO2, CO, OCS, and sulfur. SO and CS intermediates have been observed in the cold flame Kondratiev reported the yields of SO2, CO, OCS, and S2 as functions of the initial [O2] [CS2] ratio in flames. At a ratio of 2.5 1, the products were almost exclusively SO2 and CO in a ratio of 2 1, suggesting that the bulk of the reactants obeyed the stoichiometry 

At lower [O2] [CS2] ratios OCS and S2 were evident, but still in smaller quantities than either the CO or SO2. 

Early work concentrated on determining the explosion limits and induction period this material has been reviewed by Grewer . We shall concentrate on the later work which provides direct information on the mechanism of the reaction. 

The most important single study of the explosive oxidation of CS2 was made by Myerson et who followed CS2, intermediates, and products by uv absorp- 

This would account for the early appearance of CS. However, since CS was reported to be stable to oxidation by O2 below 100 they assumed the second 

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Oxidation of CS-> by H->Oo CS2 is fairly stable in acidic solutions but is quantitively oxidized to sulfuric acid by H202 in alkaline solutions (72,73). The overall stoichiometry for the reaction can be written as ... 

By analogy with the normal layer structures (large polarizable anions) we should expect the anti structures to occur for the large polarizable cations such as Ag" ", Cs", Tl" , and Pb ". However, the situation is more complicated because not all these compounds are normal valence compounds there is clearly some delocalization of electrons in a number of them. It is interesting to compare the oxides of Cs ... 

Gold(V)—Salts of [AuFg] containing the novel An " oxidation state, have been isolated via Scheme 26. Alternatively, the caesium salt can be obtained by direct oxidation of Cs[AuF4] with fluorine. Raman spectra were recorded, and X-ray powder patterns showed the salts to be isomorphous with related [MFg] (M = Ru, Ir or Pt) salts. 

A very convenient way to follow adsorption is the detection of electrons generated during the adsorption process. Since the reaction with the surface must be sufficiently energetic for the emitted electrons being able to overcome the substrate work-function, the phenomenon has been observed only in a few cases, e.g. during the oxidation of Cs- and Na-surfaces [94GRO],[92BOE]. 

Methylation of free OH groups, followed by denitration, hydrolysis, reduction, and glc analysis has been suggested as a method for determining the location of nitrate (82). This method has been suggested for CP and CS (82) as the phosphate and sulfate groups are stable to methylation and can then be removed. Periodate oxidation has been used to determine the DS of CS (81). 

There is some evidence that Cs + can be formed by cyclic voltammetry of Cs+[OTeF5] in pure MeCN at the extremely high oxidizing potential of 3 V, and that Cs + might be stabilized by 18-crown-6 and cryptand (see pp. 96 and 97 for nomenclature). However, the isolation of pure compounds containing Cs + has so far not been reported. 

These are strong, unstable acids. Oxidation to disulfides takes place readily. Several methods have been used to prepare the dithio acids (I), the most useful of which is the reaction of CS with a Grignard reagent (27). 

With its oxygen functionality, graphite oxide has chemical properties more akin to those of layered disulfides or sheet silicates than to those of graphite (Gi, T1,A2). Many studies have been of an extremely applied nature the possibility of fluorination (LI, N1), redox potentials in the presence of hydrogen peroxide (V2), the apparent density (L2), the adsorption isotherms with nitrogen (L3), and the diffusion of Cs in graphite oxide (R2). 

The T dependence of the solubility of CsH in Cs differs significantly from those for solutions of the hydrides in the other alkali metals. Distillation leaves behind involatile impurity salts, but oxygen transport from distilland to receiver has been observed. Oxygen can be carried over with the distillate in the form of COj or CO, the former being produced by decomposition of carbonate and the latter by reduction of oxides with a carbon impurity under dry conditions near the end of distillation. The identification of CO among the noncondensable gases during the distillation of Cs lends support to this. ... 

In the Lai.,CsxMn03 catalyst, the T decreases with an increase of x value and shows an almost constant value upon substitution of x>0.3. It is thought that the oxygen vacancy sites of perovskite oxide increase with an increase of amount of Cs and the oxidation activity also increases. This result is also verified by the TPR result of these catalysts(Fig. 3). As shown in Fig. 3, the reduction peak appears at low temperature with an increase of x value and no change is shown at more than x=0.3. It can thus be concluded that the catalytic performance of these oxides increases as the amount of Cs in the crystal lattice increases. However, the substitution of Cs to more than x=0.3 leads to excess Cs, which is present on the surface of mixed oxides might have no effect on the catalytic activity... 

Evans CS, B Dellinger (2005a) Mechanisms of dioxin formation from the high temperature oxidation of 2-chlorophenol. Environ Sci Technol 39 122-127. 

As it is shown above for many cases, dioxides, sulfide oxides and disulfides of carbon decompose upon irradiation into two carbene type fragments. They can recombine if a wavelength is used, which is absorbed by one of the fragments. According to the recombination of two molecules of CS it should also be possible to synthesize S=C=C=0 117, if CS is photochemically excited in the presence of carbon monoxide. 

The evaluation of carriers and catalyst compositions showed that significantly higher SO2 oxidation activity could be achieved with Cs as a promoter under the operating conditions downstream the intermediate absorption tower as demonstrated by the results in Table 1, where the activity compared to the standard product is increased by more than a factor 2. This was clearly sufficient for the introduction of VK69 to the market as a new sulphuric acid catalyst. The activity results for different melt compositions were used to optimise the vanadium content and the molar ratios of K/V, Na/V. and Cs/V. However, the choice of Cs/V was not only a question of maximum activity, because of the significant influence of the Cs content on the raw material costs (the price of caesium is 50-100 times the price of potassium on a molar basis). Here, the economic benefits obtained by the sulphuric acid producer by the marginal activity improvement at high Cs content also had to be taken into account. 

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