Sulfur contaminant

Sulfur Compounds. Various gas streams are treated by molecular sieves to remove sulfur contaminants. In the desulfurization of wellhead natural gas, the unit is designed to remove sulfur compounds selectively, but not carbon dioxide, which would occur in Hquid scmbbing processes. Molecular sieve treatment offers advantages over Hquid scmbbing processes in reduced equipment size because the acid gas load is smaller in production economics because there is no gas shrinkage (leaving CO2 in the residue gas) and in the fact that the gas is also fliUy dehydrated, alleviating the need for downstream dehydration. 

A fermentation route to 1-butanol based on carbon monoxide employing the anaerobic bacterium, Butyribacterium methjlotrophicum has been reported (14,15). In contrast to other commercial catalytic processes for converting synthesis gas to alcohols, the new process is insensitive to sulfur contaminants. Current productivities to butanol are 1 g/L, about 10% of that required for commercial viabiUty. Researchers hope to learn enough about the bacteria s control mechanisms to be able to use recombinant DNA to make the cells produce more butanol. 

Hj, Pd/C, NajCOj, THE (until complete removal of sulfUr contaminant)... 

Disulfur dichtoridc was added to an aqueous solution of ammonia to give a yellow precipitate of sulfur contaminated with S4N4 y. Pharm. Chim. 11, 315 (1835). 

The effect of sulfur contamination on catalyst activity was examined in a special test run in the SASOL plant. Conversion in 6.3 and 23.8% of the total catalyst bed, taken as an indirect criterion of catalyst activity, is plotted vs. operating time in Figure 3. 

Pseudomonas has been disclosed [233], The method consists of mutating the genes by UV irradiation or other methods and separating the desired protein. A specific amino acid sequence, present in that protein, shows the function for regulating the expression of benzothiophene oxidase gene. The fact that the protein is thought to be useful for both, desulfurization and for purification of sulfur contaminated soil or waste waters indicates a probable destructive pathway. 

Chemical Agent HT Agent T is bis [2-(2-chloroethylthio) ethyl] ether (CAS 63918-89-8) and is a sulfur, oxygen and chlorine compound similar in structure to HD. It is 60 percent HD and 40 percent T plus a variety of sulfur contaminants and impurities, and is a blister agent. 

Hydrode- sulfurization Treatment Catalytic Remove sulfur, contaminants High-sulfur residual/gas oil Desulfurized olefins... 

Impurities other than hydrocarbons are of concern in the petroleum industry. For example, many catalytic processes are sensitive to sulfur contaminants. Consequently, there is also a series of methods to determine trace concentrations of sulfur-containing compounds (ASTM D1685, D3961, D4045, D4735). 

Natural gas is cleaned of its sulfur contaminants in a fuel cleanup device. Steam is added to the fuel stream prior to being fed to the internally reforming fuel cell. The fuel reacts electrochemically with the oxidant within the fuel cell to produce 3 MW of dc power. 

Esterification Reactions. The use of solid acids provides a practical substitute for homogeneous acid catalysts commonly employed to prepare alkyl esters. The use of homogeneous acid catalysts, such as sulfuric acid, and p-toluene- or methane-sulfonic acids, generally results in sulfur contamination of the final product, which upon combustion yield compounds that are known pollutants. 

Thiourea dioxide has a stronger reducing effect (-1100 mV) than hydrosulfite. Therefore, with sensitive dyes, a risk of over-reduction exists. In addition, the oxidation products of thiourea dioxide contribute to the nitrogen and sulfur contamination of wastewater. 

Organic reducing agents such as hydroxyacetone do not contribute to the sulfur contamination of wastewater. However, the reducing effect of hydroxyacetone is much weaker (-810 mV), so it cannot replace hydrosulfite in all applications. The use of hydroxyacetone is restricted to closed systems because it forms strong-smelling condensation products in alkaline solution. 

Sensitivity of exhaust - after treatment devices. It is clear that excessive deposition of phosphorus and sulfur on the catalyst can cause the reduction in system efficiency. Oil phosphorus contaminant comes from the oil additive ZDDP. The reduction in its use adversely affects both antiwear and antioxidation performance. Sulfur comes from the base oil, antiwear additives, detergents, organomolybdenum friction modifiers, and from the fuel. There is strong pressure from OEMs to reduce the sulfur level of the fuel, and to reduce the sulfur contamination of the catalyst, which results from presence of sulfur in oil. 

Fig. 8 Mott/Schottky plots as obtained from CdS-(0001)Cd (a) polished and etched as usual (sulfur contaminated) (b) sulfur free (for details see Meissner et al. 1987b)...

In the current investigation we have extended these types of experiments to cover the influence of sulfur on the catalytic properties of iron. Since C2H4 does not readily undergo decomposition on iron surfaces we elected to use the decomposition of CO/H2 and CO/C2H4/H2 mixtures at 600 0 as the probe reactions in this work. For this purpose, both the amount of solid carbon and the gas phase product distribution arising from the decomposition of these mixtures have been used to monitor variations in the catalytic behavior of both pure and sulfur contaminated iron particles. 

Figure 37 First (solid line) and second (dashed line) voltammetric cycles of a sulfur contaminated Ni(lll) surface described in the caption to Figure 36.

The dramatic increase in irreversible CO adsorption on presulfided supported nickel catalysts at moderate pressures (162) has significant, practical implications in regard to the use of CO chemisorption to measure nickel dispersion. For example, it is often desirable to determine nickel surface areas for catalysts used in a process where sulfur impurities are present in the reactants. Substantial differences in the measurements of nickel surface area by H2 or CO adsorption are possible depending upon the catalyst history and choice of adsorption conditions. In view of the ease with which catalysts may be poisoned by sulfur contaminants at extremely low concentrations in almost any catalytic process, and since large CO uptakes may be observed on supported Ni not necessarily representative of the unpoisoned nickel surface area, the use of CO adsorption to measure nickel surface areas is highly questionable under almost any circumstance. 

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... 

In order to be able to reduce the pollution load of the pulp mills, attempts have been made to diminish the use of sulfur chemicals even if their complete elimination is difficult. Sulfur contaminants are easily introduced into the system, e.g., in connection with the use of oil as fuel, and already traces of them give rise to odor. 

Phenol50 Hydrogen peroxide Removal of sulfur contaminants from benzene sulfonic acid hydroxylation... 

Heptasulfur imide follows soon after the sulfur, with which it overlaps slightly. It is best to reject the early sulfur-contaminated fractions, which entails little loss. The pure fractions are combined, and on evaporation deposit large, nearly colorless rhombs of the imide. Yield 25-45 g. To remove any remaining traces of sulfur, the imide can be recrystallized by evaporation of a warm solution in carbon disulfide, or by allowing a satvurated solution in boiling carbon tetrachloride or hot toluene to cool. 

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