Hydrogen sulfide, catalysts affected

SolubiHty of carbon dioxide in ethanolamines is affected by temperature, amine solution strength, and carbon dioxide partial pressure. Information on the performance of amines is available in the Hterature and from amine manufacturers. Values for the solubiHty of carbon dioxide and hydrogen sulfide mixtures in monoethanolamine and for the solubiHty of carbon dioxide in diethanolamine are given (36,37). SolubiHty of carbon dioxide in monoethanolamine is provided (38). The effects of catalysts have been studied to improve the activity of amines and provide absorption data for carbon dioxide in both mono- and diethanolamine solutions with and without sodium arsenite as a catalyst (39). Absorption kinetics over a range of contact times for carbon dioxide in monoethanolamine have also been investigated (40). 

Hydrogen sulfide At low levels, hydrogen sulfide can inhibit aromatic ring saturation. This results in higher-octane gasoline and low-smoke-point jet fuel. At high concentrations, cracking catalyst activity is adversely affected. 

Figure 3 shows the effect of sulfiding on the hydrodesulfurization of thiophene over various noble metal/HZSM-5 catalysts. It was revealed that the high and stable activity of the Pt/HZSM-5 catalyst was hardly affected by the introduction of hydrogen sulfide. 

Pure component studies indicate the rate of mercaptan formation is sufficiently rapid at hydrotreating conditions compared to the saturation step which lead to alkane [8]. The exothermic reversible reaction, which shifts to the left at higher hydrogen sulfide partial pressure, is also dependent on temperature, feedstock type, total sulfiir, partial pressure of hydrogen and alkenes, space velocity and catalyst type. Furthermore the size of the reactor affect the balance between the kinetic sulfur removal and alkene saturation [9]. 

Almost all polar substances exert a strong negative influence on the polymerization. COS and hydrogen sulfide, particularly, are considered to be strong catalyst poisons, of which traces of more than 0.2volppm affect a catalyst s activity. Neither the solvent nor the gaseous monomer should contain water, carbon dioxide, alcohols, or other polar substances in excess of 5 ppm. Purification may be carried out by means of molecular sieves. 

In comparison to SO2, hydrogen sulfide is reported to have an even more adverse effect on fuel cell catalysts [33,37,43,50]. H2S can strongly adsorb onto Ft and affect the catalyst layer by disrupting its morphology [43]. By occupying polyatomic sites on the catalyst, it prevents the reactants from reaching reaction sites. A mechanism proposed for the interaction of hydrogen sulfide with a platinum surface involves the formation of adsorbed... 

Sulfation was more effectively controlled by the use of titania catalysts, which were not affected by oxygen concentrations of several thousand parts per million. This was partly because the thiosulfate intermediate on titania is unstable above 100°C, and because surface sulfates on titania are more easily reduced with hydrogen sulfide." This means that a titania surface is free from sulfate, whereas sulfate blocks an alumina surface. Fmther advantages of using titania are that it can operate at a higher space velocity than alumina and convert a greater proportion of any carbon disulfide and carbon oxysulfide present. 

The first HTS catalysts were reported to operate for about two years before replacement was required. As production techniques were developed, however, catalyst lives improved so that by 1940, lives of more than 14 years were regularly achieved. There were few poisons which affected the catalyst performance although sulfirr, which was the most common impurity in early plants, did sulfide the magnetite. This reaction was, nevertheless, reversible. If hydrogen sulfide levels exceeded about 300 ppm, sulfided catalysts could not be regenerated... 

It is evident that the activation of molecular hydrogen does not require the existence of a solid metal with properties associated with a group of metallic atoms. It seems probable that the present information on molecularly dispersed catalysts will apply to atoms or ions, present on the surface of metals or metal oxides or sulfides, which singly or in small numbers constitute active sites. Of course the atom on the surface must be affected by the bulk solid, which is part of its environment. 

The measure of activity on these pretreated catalysts gives a direct access to the real toxicity of sulfur for the specific reaction. Figure 12 emphasizes the turnover numbers of the 1-butene hydrogenation and isomerization versus the sulfur level. The sulfiding of the metal deactivates the catalyst for both reactions. Nevertheless, they are quantitatively not similarly affected the hydrogenation shows a toxicity of 5 and the izomerization of 2. The rates are not proportional to the free surface portion, which would be indicated by a toxicity of 1. The addition of one sulfur atom deactivates more than one palladium atom. 

The biscinchona alkaloid ligands can also be used for the asymmetric oxidation of sulfides to sulfoxides with hydrogen peroxide as the oxidant in the presence of tungsten(VI) oxide, or layered double hydroxide (LDH) supported 0s04 as catalyst (Scheme 3.46) [375, 376]. The approach can also be used to affect a kinetic resolution of racemic sulfoxides by oxidation of one enantiomer to the sulfone (Scheme 3.47) [376]. 

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