Adsorption sulfur compounds

Conversion Processes. Most of the adsorption and absorption processes remove hydrogen sulfide from sour gas streams thus producing both a sweetened product stream and an enriched hydrogen sulfide stream. In addition to the hydrogen sulfide, this latter stream can contain other co-absorbed species, potentially including carbon dioxide, hydrocarbons, and other sulfur compounds. Conversion processes treat the hydrogen sulfide stream to recover the sulfur as a salable product. 

Although the continuous-countercurrent type of operation has found limited application in the removal of gaseous pollutants from process streams (Tor example, the removal of carbon dioxide and sulfur compounds such as hydrogen sulfide and carbonyl sulfide), by far the most common type of operation presently in use is the fixed-bed adsorber. The relatively high cost of continuously transporting solid particles as required in steady-state operations makes fixed-bed adsorption an attractive, economical alternative. If intermittent or batch operation is practical, a simple one-bed system, cycling alternately between the adsorption and regeneration phases, 1 suffice. 

It is believe that the HDS sites (rim sites and edge sites) are different than the olefin hydrogenation sites (rim sites) opening an opportunity for the development of selective HDS catalysts [45 171. Another concept to exploit in catalyst development is the competitive adsorption, by which the sulfur compounds inhibit olefins hydrogenation [48]. 

In this equation, B stands for adsorption coefficients and C for concentrations. The thermodynamic control imposes the use of very high pressures, low space velocities, and very active catalysts. For the specific case of aromatic saturation and in the presence of H2S or any other sulfur compound, NiW is the recommended catalyst [66], However, in those cases where a precious metal catalyst may be used then, it becomes the preferred choice [67],... 

Katasorbon A process for removing carbonyl sulfide and other organic sulfur compounds from syngas by combined catalysis and adsorption. Offered by Lurgi. 

In ODS, sulfur compounds present in fuels are oxidized to more polar sulfones / sulfoxides to facilitate their removal by solvent extraction or adsorption. Various oxidation systems have been reported in the literature for this transformation. Among these oxidants like hydrogen peroxide (H2O2) and carboxylic acid as catalyst3"5. For the chemical industry, it becomes more and more important to develop cleaner technologies. Solvent extraction processes are used to separate sulfones / sulfoxides from oxidized fuels. These processes required suitable and selective solvents for separation of oxidized sulfur compounds from petroleum feedstocks. 

Natural gas feedstock is very dependent of the source location in some cases it has high levels of H2S, CO2 and hydrocarbons. Organic sulfur compounds must be removed because they will irreversibly deactivate both reforming and WGS catalysts. Hence a preliminary feed desulfurization step is necessary. This process consists in a medium-pressure hydrogenation (usually on a cobalt-molybdenum catalyst at 290-370 °C), which reduces sulfur compounds to H2S, followed by H2S separation through ZnO adsorption (at 340-390 °C) or amine absorption [9]. 

Other Sulfur Compounds and Complex Adsorption Layers. 863... 

Other Sulfur Compounds and Complex Adsorption Layers Adsorption of 5-(octyldithio)-2-nitrobenzoic acid on a gold electrode has been investigated using a quartz crystal microbalance [177]. 

Long-term poisoning of the NOx storage components by sulfur and phosphorus contained in fuel and lubricants leads to gradual decrease of the effective NOx adsorption capacity. The sulfates formed on the NOx storage sites are more stable than the nitrates, and special de-sulfurization techniques need to be applied from time to time to keep the NSRC effectiveness on a reasonable level (cf., e.g., Dieselnet, 2007). The NSRC poisoning by different sulfur compounds (S02, H2S and COS) was examined by Amberntsson et al. (2002). 

The number of available bonding orbitals on Co(Ni) could vary with conditions (i) the CN could change from 5 to 6 (ii) at CN = 6 the complex could be either octahedral or trigonal bipyramidal (iii) the number of vacant orbitals may vary if equilibrium adsorption is rapid and competitive between the sulfur compound and other ligands, such as H2S (see Fig. 22b), where one orbital is occupied by a coordinated H2S molecule. 

Adsorption (coordination) of the sulfur compound to the active site... 

There are no real thermodynamic limits in the removal of sulfur from any organic sulfur compound by reaction with hydrogen (1, 2, 5). There are, however, limits on the overall rates of conversion that may be achieved by increasing the temperature of the reaction. A classic limitation in rates is the result of the inverse relationship between adsorption on a catalytic surface and temperature. This may be a problem with dialkyldibenzothio-phenes, which have steric limitations for adsorption. 

It appears that the inhibition by both H2S and aromatic hydrocarbons involves competition between the inhibitor and the reactive sulfur compound for adsorption on the active site. However, inhibition could also be the result of occupancy of one or more of the bonding orbitals of the Co(Ni) by some nonreacting molecule, such as H2S or naphthalene. This would prevent the oxidative addition of the thiophene ring to the Co(Ni) in a mechanistic sequence such as that described in Figs. 

Figure 7 shows the activity and selectivity towards sulfur compounds of H-NbMCM-41 with various Si/Nb ratio H-NbMCM-41 seems to be a good catalyst as far as the formation of methanethiol is concerned. All hydrogen forms of niobium-containing MCM-41 materials are very stable in the production of sulfur compounds. The reason for that is the low acidity of the material, the absence of dissociative adsorption of H2S, and very easy formation of methoxy species on the surface as demonstrated earlier on the basis of IR measurements [3,10] If the mesoporous matrix possesses A1 instead of Nb, the MeOH conversion is higher, but the selectivity to methanothiol is lower. 

While most bearings depend on the viscosity of the oil for the formation ol a lubricating film (0.01)01 lo 0.11020.0(125 to 0.051 nun thick), iherc arc many cases where this is not feasible and successful lubrication depends on the formation of veiy thin films t III to It) A thicki. This was geneiallr thoughl to occur through preferential adsorption by the solid surface of polar compounds (c.g.. naplhihenic acids, sulfur compounds) present m small ainounls In the otl. 

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