Sulfur-containing environments

The most common form of corrosion is uniform corrosion, in which the entire metal surface degrades at a near uniform rate (1 3). Often the surface is covered by the corrosion products. The msting of iron (qv) in a humid atmosphere or the tarnishing of copper (qv) or silver alloys in sulfur-containing environments are examples (see also SiLVERAND SILVER ALLOYS). High temperature, or dry, oxidation, is also usually uniform in character. Uniform corrosion, the most visible form of corrosion, is the least insidious because the weight lost by metal dissolution can be monitored and predicted. 

The traditional HDS catalysts are CoMo or NiMo based catalysts. Highly dispersed molybdenum sulphide exhibits a low but stable catalytic activity in a sulfur-containing environment. By adding the promoter elements, cobalt or nickel, in an atomic Co/Mo or NiMo ratio of 0.3 to 0.5 a ten-fold increase in activity could be achieved [1], Further improvements were made by addition of chelating agents, phosphate, and fluorine [2]. 

F). For best resistance to sulfur-containing environments, iron-base alloys should contain high chromium and low nickel. 

Chromizing [6,7]. In the chromizing process a layer of chromium is applied at a high temperature which allows inward diffusion forming a composition gradient. An important use of this process is the protection of nickel from sulfur-containing environments. 

It should be noted that titanium aUo5 are generally not susceptible to sulfide stress cracking (SSC) in HjS-rich, sulfides, and/or sulfur containing environments (e.g., sour gas/oil well fluids). This inherent SSC resistance stems from the fact that formation of titanium sulfide corrosion products is not thermodynamically favored, such that stability of titanium s protective oxide surface film wiU prevail even at higher service temperatures. In these hot sour brine service environments, resistance to chloride-induced SCC is a more relevemt issue for titanium alloys. 

Mazumder TK, Nishio N, Fukazaki S, et al. 1986. Effect of sulfur-containing compounds on growth of Methanosarcina barkeri in defined medium. Appl Environ Microbiol 10 617-622. 

An efficient, low temperature oxidation catalyst was developed based on highly disperse metal catalyst on nanostructured Ti02 support. Addition of dopants inhibits metal sintering and prevents catalyst deactivation. The nanostructured catalyst was formulated to tolerate common poisons found in environments such as halogen- and sulfur-containing compounds. The nanocatalyst is capable of oxidizing carbon monoxide and common VOCs to carbon dioxide and water at near ambient temperatures (25-50 °C). 

The mechanisms by which acid rain forms and exerts its effects on the environment are now quite well understood. The primary culprit in this process is sulfur dioxide, produced when sulfur-containing coal is burned in power generating plants ... 

It is also possible that bacterial decomposition of sulfur containing organic compounds may account for some DMS in natural waters (31-36). Conversely, bacteria may also utilize DMS and therefore act as a sink (37-39). The contribution of bacterial processes to the DMS/DMSP cycle in open ocean environments has not been addressed and is as yet not understood. However, studies to better understand the biogeochemistry of DMS can not exclude bacterial processes (e.g. 4041). 

Reduced sulfur compounds are ubiquitous in aqueous and atmospheric systems (10,11). Natural sources of reduced sulfur species in aqueous environment result from biological reduction of sulfate, anaerobic microbial processes in sewage systems, putrefaction of sulfur-containing amino-acids (12), oxidative decomposition of pyrite (13), and activities of marine organisms in the upper layers of the ocean (14,15). The build-up of sulfides in areas such as the Black Sea is also giving cause for concern (8). 

In summary, considerable progress has been made in recent years in the characterization of sulfur-containing organic compounds in coal. Much of this progress is attributed to the development of GC-MS. However, systematic study of many coal samples from different seams is needed to establish a firm relationship between the nature of organosulfur compounds and either coal rank or depositional environment. 

Tables 1 and 2 contain the formation heat values for adsorption complexes of sulfur-containing amino acids on a silica surface from gas phase and for their zwitterions with a hydrated environment...

Although metals or even promoted metals have very low sulfur tolerances in synthesis reactions, other materials, such as metal oxides, nitrides, borides, and sulfides, may have greater tolerance to sulfur poisoning because of their potential ability to resist sulfidation (18). The extremely low steady-state activities of Co, Ni, and Ru metals in a sulfur-contaminated stream actually correspond to the activities of the sulfided metal surfaces. However, if more active sulfides could be found, their activity/selectivity properties would be presumably quite stable in a reducing, H2S-containing environment. This is, in fact, the basis for the recent development of sulfur active synthesis catalysts (211-215), which are reported to maintain stable activity/ selectivity properties in methanation and Fischer-Tropsch synthesis at H2S levels of 1% or greater. Happel and Hnatow (214), for example, reported in a recent patent that rare-earth and actinide-metal-promoted molybdenum oxide catalysts are reasonably active for methanation in the presence of 1-3% H2S. None of these patents, however, have reported intrinsic activities... 

Mackay, D., Shiu, W.Y, Ma, K.C. (1995) Rlustrated Handbook of Physical-Chemical Properties and Environmental Fate for Organic Chemicals. Vol. 4, Oxygen, Nitrogen and Sulfur-Containing Compounds. Lewis Publishers/CRC Press, Boca Raton, Florida. Mackay, D., Yuen, T.K. (1983) Mass transfer coefficients correlations for volatilization of organic solutes from water. Environ. Sci. Technol. 17, 211-217. 

The chapter is divided into four main parts Sec. 2 Thiols , Sec. 3 Thioethers , Sec. 4 Disulfides , and Sec. 5 Sulfoxides and Sulfonyls . They describe how sophisticated radiation-chemical techniques have been applied to address the role of sulfur-free radicals derived from these three classes of sulfur-containing compounds, in particular, in the biological environment. Important outputs from these studies are new directions for improving our knowledge of how sulfur-centered radicals interact with major cellular targets during oxidative stress, i.e. proteins, DNA, and lipids. 

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