Sulfides catalyst inhibitors

Pyridine (1.0 gm) added as a polymerization inhibitor. b S(CH2CH2OH)2 (6.0 gm) added as a catalyst. c Activated carbon with silver oxide or Ni-W sulfide catalyst added. a Anion-exchange resin (40-100 gm) added see U.S. Pat. 2,614,099 (1952). Absolute ethanol (62 gm) and 1 gm of FeCl3 or TiCl3 added. 

Sulfided catalyst are not stable for storage. Therefore, sulfidation has either to be carried out just before the start of the reaction or the inhibitor has to be added to the reaction solution. In addition, most sulfidation procedures are not easy to reproduce. 

Uses Emulsifier surfactant chemical intermediate raw material for surfactants germicide corrosion inhibitor in process plant streams acid scavenger in petrol prods. epoxy hardener curing catalyst vise, index improver for lubricants flotation collector for sulfide ores inhibitor for butadiene polymerization processing aid for metal and textiles... 

Many nucleophiles act as inhibitors of platinum, palladium and rhodium catalysts. The strongest are mercaptans, sulfides, cyanide and iodide weaker are ammonia, azides, acetates and alkalis [26]. 

Some of other effective platinum catalysts are sulfided platinum on carbon120 or platinum catalysts with inhibitors such as bis(2-hydroxyethyl)sulfide,121 morpholine,122 polyamines,123 phosphorous acid,105 phosphoric acid,124 and dicyandiamide.96 Dicy-andiamide was originally used as an effective inhibitor for Raney Ni, as described above (see eq. 9.50).113 Hydrogenations of halonitrobenzenes with use of these platinum catalysts are summarized in Table 9.5. In one patent, it is claimed that ethano-lamine is a better inhibitor than morpholine for Pt-C. Thus, 3,4-dichloronitrobenzene was hydrogenated over Pt-C modified with iron oxide in the presence of 1.2 mol% ethanolamine to give 3,4-dichloroaniline containing only 235 ppm of 4-chloroaniline, compared to 548 ppm with morpholine as the inhibitor.125... 

Thietane is a superior inhibitor of corrosion of iron in 10% hydrochloric acid and its effectiveness is said to be due to partial polymerization on the surface of the iron. Addition of chloride ion reduces the inhibition, possibly by inducing ringopening with the formation of sulfhydryl groups. The cyclic sulfide also has been considered as an odorant for natural gas and its absorption by organic soil and clay have been determined. Stabilization of methylchloroform and trichloroethylene by thietane, 2-methylthietane, 3-hydroxythietane, and two spirothietane derivatives has been claimed. Phosphorus and tin derivatives of 3,3-bis-hydroxy-methylthie-tane are reported to be light stabilizers for poly(vinyl chloride), and the dibutyl-tin derivative is a catalyst for the polymerization of aliphatic isocyanates. Mercury and zinc compounds derived from phenylmercury or phenylzinc hydroxide and 3-... 

The detoxification of catalysts poisoned by Group V or VI compounds can be accomplished by reactions in which these inhibitors are converted to substances that do not have unshared electron pairs. For instance, bivalent sulfur compounds can be oxidized to sulfones or sulfonic acids by treatment with hypochlorite or hydroperoxides. "2,108 Thiophene, dimethyl sulfide and other sulfur and metal ion poisons as well as phosphorous"" and arsenic compounds " can be removed from platinum by washing the catalyst with acetic acid. This method for the reactivation of the catalyst is simpler than the oxidation techniques. Acidic or basic inhibitors are removed by the addition of an appropriate amount of base or acid, respectively. The effect of a small amount of inhibitor can frequently be overcome by the use of a larger amount of catalyst. 

It may be added that sulfides or disulfides, which are found to be glycolysis inhibitors, also act as poisons or inhibitors for such inorganic catalysts as nickel or nickel oxide catalysts. 

It is generally assumed that ions which can accelerate either or both partial reactions in a corrosion process are capable of being adsorbed on the iron surface. Thus it is known that hydrogen sulfide ions which accelerate both partial reactions of acid corrosion (although predominantly the anodic one), and formic acid molecules which catalyze the cathodic partial reaction but inhibit the anodic one, as well as commercial inhibitors which reduce both partial reactions, are in fact adsorbed on the iron surface. As a consequence the mere fact that adsorption takes place cannot be used to predict an expected change in corrosion rate as it is also known that halide ions cat-alize the anodic dissolution of indium, while hydroxyl adsorption catalyzes the anodic dissolution of iron. Furthermore, it is also known that certain ions can act either as a catalyst or an inhibitor when adsorbed on the metal surface depending on the type of metal considered. Kolotyrkin (18) observed that the adsorp-... 

A strong inhibitor is a catalyst poison, e.g. sulfur for Ni hydrogenation catalysts. For example, partially sulfided Ni catalysts are applied for the selective hydrogenation of alkynes (lower activity than Lindlar s catalyst, reaction temperature 200-250 °C, continuous feed of 1 ppm H2S to the reactant). 

These compounds react quite differently over CoMo and NiMo catalysts, and the response of the two catalysts to the hydrogen sulfide produced during reaction and to inhibitors in the feed is dissimilar. To appreciate the criteria governing the choice of catalyst for ultra deep desulfurization and the consequences for product properties and hydrogen consumption, it is important to imderstand how the most refractive sulfur compounds react as well as the role played by inhibitors. 

The Catacarb process, which was disclosed by Eickmeyer (1962), is licensed by Eickmey-er and Associates of Prairie Village, Kansas. For most applications the Catacarb process utilizes a catalyzed hot potassium carbonate solution however, potassium borate solutions are used for the removal of hydrogen sulfide in the absence of carbon dioxide (Gangriwala and Chao, 1985). The solutions contain undisclosed additives that catalyze absorption and desorption of acid gases, particularly carbon dioxide. The additives, which include a corrosion inhibitor, are claimed to have no effect on reformer or methanation catalysts that the purified gas may pass through downstream of the Catacarb absorber (Morse, 1968). 

Oxidation Processes. These processes convert mercaptans into less odoriferous disulfides by such processes as the doctor, copper chloride, hypochlorite, and lead sulfide, processes. Since disulfides harm the lead susceptibility of gasoline and since the need of reduction of mercaptans to doctor sweet (0.0004 per cent) is being questioned, these processes are being gradually abandoned. However, catalysts or inhibitors of the 7>-phenylenediamine type, which in the presence of air cause mercaptans in some caustic-washed gasolines to be converted during a few days into disulfides (so-called inhibitor sweetening), continue to be used because of the cheapness of such a process. Small amounts of... 

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