Adsorbing hydrogen sulphides

The reaction between alcohols and hydrogen sulphide can proceed not only via one reaction pathway. The reaction pathway depends on the type of zeolites. It was stated that over hydrogen forms of faujasite type zeolites the Brflnsted acid sites play the role of active centres and the reaction proceeds between chemisorbed alcohol and physisorbed H2S (ref.2). However, in the absence of Brttnsted acid sites the cations seem to play the role of active centres (ref.7). It was suggested that on cationic forms of zeolites the reaction takes place between dissociatively adsorbed hydrogen sulphide and alcohol. The results obtained in this work confirm this sugge-... 

Important quantitative experiments on the adsorption of gases on solids (charcoal and other porous bodies) were made by Theodore de Saussure and Hunter. J. Stenhouse found that the adsorbed gas is chemically active (charcoal which has adsorbed hydrogen sulphide inflames in oxygen), and he devised a charcoal respirator. 

In addition, they have potential applications as an additive in soils, for heavy metal adsorption [24] and as carrier in pesticides, herbicides and fungicides. Based on such adsorbing characteristics, zeolites have also been effective as additive in animal feeds to act as a detoxing agent, e.g., Clinoptilolite. Zeolites exhibit possibilities of applications in animal sheds for adsorbing hydrogen sulphides and subsequent odour control in the surrounding environment. 

Adsorbed species may also accelerate the rate of anodic dissolution of metals, as indicated by a decrease in Tafel slope for the reaction. Thus the presence of hydrogen sulphide in acid solutions stimulates the corrosion of iron, and decreases the Tafel slope The reaction path through... 

Type 4A sieves. The pore size is about 4 Angstroms, so that, besides water, the ethane molecules (but not butane) can be adsorbed. Other molecules removed from mixtures include carbon dioxide, hydrogen sulphide, sulphur dioxide, ammonia, methanol, ethanol, ethylene, acetylene, propylene, n-propyl alcohol, ethylene oxide and (below -30°) nitrogen, oxygen and methane. The material is supplied as beads, pellets or powder. 

For example, carbon dioxide from air or ethylene nitrogen oxides from nitrogen methanol from ethyl ether. In general, carbon dioxide, carbon monoxide, ammonia, hydrogen sulphide, mercaptans, ethane, ethylene, acetylene, propane and propylene are readily removed at 25°. In mixtures of gases, the more polar ones are preferentially adsorbed). 

Sulphur is applied, commonly in the powdered form or as /lowers of sulphur, to medicinal purposes, and also agriculturally as a dust or dressing to check fungoid diseases of certain plants, ( specially the vine.5 The toxic properties of sulphur have not been fully elucidated and are variously ascribed to reduction to hydrogen sulphide, oxidation to polythionic acids, or to the vapour of the element itself, produced by slow vaporisation.8 If adsorbed pcntathionic acid be removed from... 

Sulphur compounds in the fuel (0.05-0.01 %) must be removed because they would poison the reformer catalyst. Sulphur compounds are removed by using a hydrodesulphurization catalyst (HDS), typically noble metals on alumina, to convert the organic sulphur to hydrogen sulphide. Then a zinc oxide adsorbent bed is used to trap the hydrogen sulphide ... 

The efficiency of the adsorption of many gases on solid adsorbents may be increased by using specific impregnation substances. These are applied onto carriers or directly onto the charcoal. In this way it is possible to increase strongly, for instance, the adsorption efficiency for ammonia (with the help of bromine), formaldehyde (with the help of sodium sulphide) and hydrogen sulphide (with the help of silver cyanide or lead acetate). 

Adsorbed species may also accelerate the rate of anodic dissolution of metals, as indicated by a decrease in Tafel slope for the reaction. Thus the presence of hydrogen sulphide in acid solutions stimulates the corrosion of iron, and decreases the Tafel slope - - . The reaction path through (Fe-HS-W has been postulated to lead to easier anodic dissolution than that through (Fe-OH) s.. This effect of hydrogen sulphide is thought to be responsible for the acceleration of corrosion of iron observed with some inhibitive sulphur compounds, e.g. thioureas , at low concentrations, since hydrogen sulphide has been identified as a reduction product. However, the effects of hydrogen sulphide are complex, since in the presence of inhibitors such as amines , quaternary ammonium cations , thioureas . ... 

FIGURE 5.11 Amount of hydrogen sulphide adsorbed from its mixture with air on different carbons. (1) activated carbon fiber, ACF (2) oxidized activated carbon fiber OCF, (3) oxidized activated carbon fiber impregnated with copper, (4) oxidized carbon fiber impregnated with iron. (After Svetlana, S., Kartel, N.T., and Tsyba, N.N., Carbon 02, Intern. Conf. on Carbon, Beijung, 2002, Paper PI 68 D. 063. With permission.)... 

The amount of hydrogen sulphide produced per day is relatively very low and a moderately sized vessel contains sufficient zinc oxide to adsorb all of the sulphurous gas that will be generated in one year. The spent adsorbent is simply removed and the vessel filled with fresh zinc oxide. This is rare. Normally a solid adsorbent (or liquid absorbent) is regenerated and re-used. This is certainly necessary in the absorption process that is used to remove the carbon dioxide over 1 tonne of carbon dioxide is produced for every tonne of ammonia. 

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