Sulfur gaseous species

Corrosion reactions of a metal with gaseous species such as oxygen, chlorine, sulfur containing molecules or water vapor to produce a thin layer of product phase are typical of ambipolar diffusion reactions. For example, metal oxidation... 

The measured uptake coefficient y is a convolution of the processes which affect the rate of gas uptake. Uptake coefficients have been measured for various PSC surfaces and sulfuric acid solutions using a variety of experimental methods, and have been interpreted in tenns of physico-chemical models to yield reactivities and solubilities of gaseous species. More most cases the total experimental uptake coefficient ym can be represented in tenns of a resistance model, whereby the resistances l/ym and 1/y are associated with reaction and liquid solubility [42] Quantitative values for y will be discussed later in section 2.3.4. 

The results of deposition studies using H2S are summarized in Table III. The sparsity of the data reflects the problems of conducting this type of experiment. The emission rates shown are the values measured immediately before and after making deposition measurements, and are used to calculate the deposition rate. It is clear in the case of the seawater surface that changes in natural emissions complicate the study to such an extent that interpretation is impossible. Furthermore, it should be noted that the nature 01 enclosure designs provides elevated concentrations of emitted gaseous species, and it is likely that the measured emission rates already include a depositional component. The concentration of sulfur species added to the chamber in these studies is comparable to that already present, and the actual deposition rates would probably be higher at ambient reduced sulfur levels. 

Rose W. 1., Chuan R. L., Giggenbach W. F., Kyle P. R., and Symonds R. B. (1986) Rates of sulfur dioxide and particle emissions from White Island volcano. New Zealand, and an estimate of the total flux of major gaseous species. Bull. Volcanol. 48, 181-188. 

Estimating the deposition velocities of gaseous species is considerably more complex than estimating those for substances in particles, in part due to the uncertainties in the sticking and reaction probabilities. Such estimates have not been made but the potential effects of some of the typical gases can be surmised from available data on surface accumulation rates, e.g. sulfate accumulation on indoor zinc and aluminum surfaces is predominantly a result of particulate sulfate deposition rather than a corrosion reaction involving sulfur dioxide (0. 

Fig. 9. Percentage distribution of sulfur between different phases in a solar composition gas as a function of temperature for a total pressure of 10 4 bar. Gaseous species are indicated with (g), all other species are condensed phases...

We have seen in Chapter 3 that in the case of several trace gases (H2, CH4, CO, 03, N20) these sink mechanisms are provided by chemical reactions producing components that are utilized by the biosphere. Another possibility for the removal of some gaseous species (sulfur, nitrogen and organic compounds) is their transformation into particulate matter (see Chapters 3 and 4). 

With the gaseous sulfur-bearing species being predominantly hydrogen sulfide and sulfur dioxide, further recovery of elemental sulfur depends on the Claus reaction ... 

Another mode of deactivation is termed poisoning (see Figure 4), which results from a chemical reaction of a gaseous species with the active metal (or, alternatively, a strong chemisoiption bond). For example, under certain conditions sulfur can fonn a compound with some metals. Phosphorous, halogens, and lead are common poisons for noble metal catalysts. 

Sulfur Compounds. - Studies on the adsorption and electrochemical transformations of SO2 and H2S are of both fundamental and applied interest as sulfur-containing species could be either promoters or inhibitors of electrocatalytic processes depending on the situations and systems considered. In addition, the desulfurization of gaseous emissions and other waste treatment procedures illustrates a better knowledge of the electrochemistry of the sulfur-containing simple species. For instance, voltammetric behavior of irreversibly adsorbed SO2 on Pt single crystal surfaces Pt(lll) was studied by Quijada et al. "... 

This chapter provides a comprehensive summary of surface science involved in the application of activated carbon for air cleaning from sulfur containing species such as hydrogen sulfide, sulfur dioxide, and mercaptans. Moreover, the removal of organic sulfur-containing compounds from both gaseous and liquid fuel is addressed. The emphasis is placed on the role of activated carbon surfaces, either unmodified or modified in the processes of adsorption and catalytic oxidation of these pollutants. 

In other systems, similar effects of dissolved gaseous species can be important and may require the use of HT/HP corrosion test procedures to give accurate simulation of service environments. Examples of such conditions are those that contain carbon dioxide, sulfur dioxide, and NOx, which can determine the pH of the aqueous phase and affect the severity of corrosion reactions. 

In practice, situations are often encountered where the protective oxide scales contain cracks or open porosity which acts as channels for gaseous inward transport to the metal. Two examples of internal sulfidation are given in Fig. 2-18. In this case, the sulfur-containing species can penetrate the scale via the gas phase and react with the underlying metal forming internal sulfides. An important issue in this respect is the composition of the gas phase of the environment. If oxygen is involved in the equilibrium between the different components of the environment, then the activity of one of the... 

Gaseous SO2 is readily soluble in water (3927 cm SO2 in lOOg H2O at 20°). Numerous species are present in this aqueous. solution of sulfurous acid" (p. 717). At 0° a cubic clathrate hydrate also forms with a composition S02.6H20 it.s dissociation pressure reaches I atm at 7.1°. The ideal composition would be SO2.55H2O (p. 627). 

Abstract Molecular spectroscopy is one of the most important means to characterize the various species in solid, hquid and gaseous elemental sulfur. In this chapter the vibrational, UV-Vis and mass spectra of sulfur molecules with between 2 and 20 atoms are critically reviewed together with the spectra of liquid sulfur and of solid allotropes including polymeric and high-pressure phases. In particular, low temperature Raman spectroscopy is a suitable technique to identify single species in mixtures. In mass spectra cluster cations with up to 56 atoms have been observed but fragmentation processes cause serious difficulties. The UV-Vis spectra of S4 are reassigned. The modern XANES spectroscopy has just started to be applied to sulfur allotropes and other sulfur compounds. 

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