Activated carbons amination

Condit and Haynor have studied the explosive decomposition of nitrobenzene and nitroxylene. They found that the minimum temperature for nitrobenzene is about 356 C and for nitroxylene, about 308°C. The temperatures are relatively independent of the pressure of the surrounding gas, are the same in hydrogen as in methane, and are unaffected by the presence of various steels or activated carbon. Amine concentrations of 25 per cent prevent explosive decomposition, giving resinous masses instead. 

Chemical Processing. Activated carbon consumption in a variety of chemical processing appHcations is about 8% of the total (74). The activated carbon removes impurities to achieve high quaHty. For example, organic contaminants are removed from solution in the production of alum, soda ash, and potassium hydroxide (82). Other apphcations include the manufacture of dyestuffs, glycols, amines, organic acids, urea, hydrochloric acid, and phosphoric acid (83). 

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). 

For more selective hydrogenations, supported 5—10 wt % palladium on activated carbon is preferred for reductions in which ring hydrogenation is not wanted. Mild conditions, a neutral solvent, and a stoichiometric amount of hydrogen are used to avoid ring hydrogenation. There are also appHcations for 35—40 wt % cobalt on kieselguhr, copper chromite (nonpromoted or promoted with barium), 5—10 wt % platinum on activated carbon, platinum (IV) oxide (Adams catalyst), and rhenium heptasulfide. Alcohol yields can sometimes be increased by the use of nonpolar (nonacidic) solvents and small amounts of bases, such as tertiary amines, which act as catalyst inhibitors. 

The reaction starts with the nucleophilic addition of a tertiary amine 4 to the alkene 2 bearing an electron-withdrawing group. The zwitterionic intermediate 5 thus formed, has an activated carbon center a to the carbonyl group, as represented by the resonance structure 5a. The activated a-carbon acts as a nucleophilic center in a reaction with the electrophilic carbonyl carbon of the aldehyde or ketone 1 ... 

Polymeric adsorbents have also been found to be very useful, and even highly water-loving undesired materials like p-toluene sulphonic acid from waste streams can be recovered via ad.sorption and regeneration with solvents like fv -propanol. In such instances, the regeneration of activated carbons is not satisfactory, even with aqueous sodium hydroxide. Solutes like phenols, substituted phenols, aromatic amines, heterocyclic amines (pyridine, picolines, etc.) can be recovered, in a rewarding way, from aqueous solutions. 

In this study we examine the generalities in reductive alkylation however, since the subject is vast, we limited ourselves to the interaction of aromatic and aliphatic primary amines and diamines with ketones. The ketones examined include the cyclic ketone, cyclohexanone, and aliphatic ketones such as acetone, and methyl isobutyl ketone (MIBK). We limited our study to sulfided and unsulfided Pt and Pd catalysts supported on activated carbon that were commercially available from Evonik Degussa Corporation. 

Liquid-solid-gas where the solid is normally a catalyst such as in the hydrogeneration of amines, using a slurry of platinum on activated carbon as a catalyst. 

The removal of carbobenzyloxy (Cbz or Z) groups from amines or alcohols is of high interest in the fine chemicals, agricultural and pharmaceutical industry. Palladium on activated carbon is the catalyst of choice for these deprotection reactions. Nitrogen containing modifiers are known to influence the selectivity for certain deprotection reactions. In this paper we show the rate accelerating effect of certain N-containing modifiers on the deprotection of carbobenzyloxy protected amino acids in the presence of palladium on activated carbon catalysts. The experiments show that certain modifiers like pyridine and ethylenediamine increase the reaction rate and therefore shorten the reaction times compared to non-modified palladium catalysts. Triethylamine does not have an influence on the rate of deprotection. 

Trichloromethyl chloroformate (diphosgene) is used as a safe substitute for highly toxic phosgene gas. The latter is generated in situ by addition of catalytic amounts of tertiary amines or amides, or active carbon. Diphosgene also disproportionates to 2 equivalents of phosgene on heating above 250°C. 

CDI-activated hydroxyls also may undergo a side reaction to form active carbonates. This occurs when an imidazolyl carbamate reacts with another hydroxyl group before the second hydroxyl has had a chance to get activated with CDI. Particularly with adjacent hydroxyls on the same molecule, this can be a problem if a defined reactive species is desired. Any carbonates formed, however, are still reactive toward amines to create carbamate linkages. 

Figure 5.16 Photoactivation of a phenyl azide group with UV light results in the formation of a short-lived nitrene. Nitrenes may undergo a number of reactions, including insertion into active carbon-hydrogen or nitrogen-hydrogen bonds and addition to points of unsaturation in carbon chains. The most likely route of reaction, however, is to ring-expand to a dehydroazepine intermediate. This group is highly reactive toward nucleophiles, especially amines.

Izumi and Urabe [105] found first that POM compounds could be entrapped strongly on active carbons. The supported POMs catalyzed etherization of ferf-butanol and n-butanol, esterification of acetic acid with ethanol, alkylation of benzene, and dehydration of 2-propanol [105], In 1991, Neumann and Levin [108] reported the oxidation of benzylic alcohols and amines catalyzed by the neutral salt of Na5[PV2Mo10O40] impregnated on active carbon. Benzyl alcohols were oxidized efficiently to the corresponding benzaldehydes without overoxidation ... 

Alternatively, diazopyrazole (86) reacted with amines to yield triazines which, when treated with activated carbonic acid derivatives, e.g., phosgene, afforded derivatives of 161 (87CB1375). 

The previous sections have dealt primarily with reactions in which the new carbon-carbon bond is formed by an SN2 reaction between the nucleophilic carbanions and the alkylating reagent. Another important method for alkylation of carbon involves the addition of a nucleophilic carbon species to an electrophilic multiple bond. The electrophilic reaction partner is typically an a,/i-unsaturated ketone, aldehyde, or ester, but other electron-withdrawing substituents such as nitro, cyano, or sulfonyl also activate carbon-carbon double and triple bonds to nucleophilic attack. The reaction is called conjugate addition or the Michael reaction. Other kinds of nucleophiles such as amines, alkoxides, and sulfide anions also react similarly, but we will focus on the carbon-carbon bondforming reactions. 

Contaminants and by-products which arc usually present in 2- and 4-atninophenol made by catalytic reduction can be reduced or even removed completely by a variety of procedures These include treatment with 2-propanol, with aliphatic, cycloaliphatic, or aromatic ketones, with aromatic amines, with loluene or low mass alkyl acetates, or with phosphoric acid, hydroxyacetic acid, hydroxypropionic acid, or citric acid. In addition, purity may be enhanced by extraction with methylene chloride, chloroform, or nitrobenzene. Another method employed is the treatment of aqueous-solutions of aminophenols with activated carbon. 

Na5PV2Moio04o supported on active carbon is active for oxidative dehydrogenation of benzylic alcohols and amines without overoxidation of benzalde-hyde and benzylamine in the liquid phase (357). The suppression of the overoxidation may be due to the lower oxidizing ability of Na5PV2Moio04o relative to its acid form. 

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