Amine solutions, carbon dioxide

Amide-containing dibenzo-16-crown-5 compounds, transport of metal perchlorates, 161-165 Amine(s) as carriers, carbon dioxide facilitated transport through functional membranes prepared by plasma graft polymerization, 252-268 Amine solutions, carbon dioxide facilitated transport through supported liquid membranes, 239-250 Amino acid derivatives, use as heavy metal ion carriers, 175-179... 

HjO almost insoluble in cold alcohol and ether soluble in boiling alcohol it is odorless and tasteless, and its solutions are neutral. It sublimes at 170° (338° P.) without decomposition if suddenly heated above 180° (356° F.), it is decomposed into amyl-amin and carbon dioxid. 

Several mechanisms have been proposed for amine-acid gas corrosion. Riesenfeld and Blohm (1950, 19S1A, B) were the first to note that significant amine corrosion was usually associated with the evolution of acid gases from the rich amine solution. Based on this observation, Riesenfeld and Blohm stated that amine solution carbon steel corrosion was due to the presence of the acid gases themselves. For example, carbon dioxide can be evolved from rich amine solutions according to reactions 3-13 and 3-14 ... 

Uncontaminated solutions of tertiary amines such as MDEA are generally not corrosive whatever the acid gas. According to API 945, solutions of most amines are not corrosive if the ratio of hydrogen sulfide to carbon dioxide is above roughly S/9S, because the corrosion reaction leads to formation of a protective sulfide film (API, 1990). The most corrosive combinations appear to be those of primary or secondary amines with carbon dioxide. 

It must be kept under an atmosphere of nitrogen or carbon dioxide it reduces, for example, Fe(III) to Fe(II) and nitro-organic compounds RNO2 to amines RNH2 (it may be used quantitatively to estimate nitro-compounds). In neutral solution, hydrolysis occurs to give species such as [Ti(0H)(H20)s], and with alkali an insoluble substance formulated as Ti203 aq is produced this is rapidly oxidised in air. 

Chill the concentrated solution of the amine hydrochloride in ice-water, and then cautiously with stirring add an excess of 20% aqueous sodium hydroxide solution to liberate the amine. Pour the mixture into a separating-funnel, and rinse out the flask or basin with ether into the funnel. Extract the mixture twice with ether (2 X25 ml.). Dry the united ether extracts over flake or powdered sodium hydroxide, preferably overnight. Distil the dry filtered extract from an apparatus similar to that used for the oxime when the ether has been removed, distil the amine slowly under water-pump pressure, using a capillary tube having a soda-lime guard - tube to ensure that only dry air free from carbon dioxide passes through the liquid. Collect the amine, b.p. 59-61°/12 mm. at atmospheric pressure it has b.p. 163-164°. Yield, 18 g. 

The first-order decomposition rates of alkyl peroxycarbamates are strongly influenced by stmcture, eg, electron-donating substituents on nitrogen increase the rate of decomposition, and some substituents increase sensitivity to induced decomposition (20). Alkyl peroxycarbamates have been used to initiate vinyl monomer polymerizations and to cure mbbers (244). They Hberate iodine quantitatively from hydriodic acid solutions. Decomposition products include carbon dioxide, hydrazo and azo compounds, amines, imines, and O-alkyUiydroxylarnines. Many peroxycarbamates are stable at ca 20°C but decompose rapidly and sometimes violently above 80°C (20,44). 

Cyclohexylamine is miscible with water, with which it forms an azeotrope (55.8% H2O) at 96.4°C, making it especially suitable for low pressure steam systems in which it acts as a protective film-former in addition to being a neutralizing amine. Nearly two-thirds of 1989 U.S. production of 5000 —6000 t/yr cyclohexylamine serviced this appHcation (69). Carbon dioxide corrosion is inhibited by deposition of nonwettable film on metal (70). In high pressure systems CHA is chemically more stable than morpholine [110-91-8] (71). A primary amine, CHA does not directiy generate nitrosamine upon nitrite exposure as does morpholine. CHA is used for corrosion inhibitor radiator alcohol solutions, also in paper- and metal-coating industries for moisture and oxidation protection. 

Other components in the feed gas may react with and degrade the amine solution. Many of these latter reactions can be reversed by appHcation of heat, as in a reclaimer. Some reaction products cannot be reclaimed, however. Thus to keep the concentration of these materials at an acceptable level, the solution must be purged and fresh amine added periodically. The principal sources of degradation products are the reactions with carbon dioxide, carbonyl sulfide, and carbon disulfide. In refineries, sour gas streams from vacuum distillation or from fluidized catalytic cracking (FCC) units can contain oxygen or sulfur dioxide which form heat-stable salts with the amine solution (see Fluidization Petroleum). 

Diethanolamine (DEA) has replaced MEA as the most widely used amine solvent. High load DEA technologies, such as that developed by Elf Aquitaine, permit the use of high (up to 40 wt % DEA) concentration solutions. The Elf Aquitaine—DEA process allows lower cinculation rates, and has consequent reductions ia capital and utility expenses. DEA tends to be more resistant to degradation by carbonyl sulfide and carbon disulfide than MEA. DEA is, however, susceptible to degradation by carbon dioxide. 

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). 

Experience in air separation plant operations and other ciyogenic processing plants has shown that local freeze-out of impurities such as carbon dioxide can occur at concentrations well below the solubihty limit. For this reason, the carbon dioxide content of the feed gas sub-jec t to the minimum operating temperature is usually kept below 50 ppm. The amine process and the molecular sieve adsorption process are the most widely used methods for carbon dioxide removal. The amine process involves adsorption of the impurity by a lean aqueous organic amine solution. With sufficient amine recirculation rate, the carbon dioxide in the treated gas can be reduced to less than 25 ppm. Oxygen is removed by a catalytic reaction with hydrogen to form water. 

Methylkasugaminide (5) from C9-Amine (3). An aqueous solution (30 ml.) saturated with barium hydroxide was added to a solution of Co-amine hydrochloride (250 mg., 0.93 mmole) dissolved in water (3 ml.) free from carbon dioxide. The solution was refluxed for 10 hours on a steam bath. By the similar treatment of the reaction mixture as described in the case of cold alkaline hydrolysis, ammonia (0.91 mmole), barium... 

Methylkasugaminide (5) by Cold Alkaline Hydrolysis of C9-Amine (3) with Barium Hydroxide. A solution of C9-amine (519 mg., 2.24 mmoles) dissolved in 5 ml. of water free from carbon dioxide was treated with 50 ml. of barium hydroxide saturated solution at room temperature for 48 hours. Generation of ammonia was observed and barium oxalate (241 mg., 0.99 mmole) was obtained. After removal of barium oxalate, barium carbonate produced by neutralization with dry ice was also removed by filtration. The filtrate thus obtained was placed on a column of Amberlite CG-50 (ammonium form, 1.5 x 25 cm.) and developed with water. After the similar treatment as described in the cold hydrolysis of kasugamycin, ninhydrin-positive fractions afforded a colorless crystalline material (154 mg., 0.62 mmole), m.p. 223°-225°C. (dec.), [ ]D20 +110° (c=1.7, H20), pK a 1.8 and 7.9, which was identified to be C9-acid (15). Anal. Calcd. 

NOTE In simple filming amine formulations ODA is the most widely employed ingredient. Formulations are typically available as 100% concentrated flakes, 2 to 5% strength aqueous solutions, or 5 to 10% strength emulsions. Solid ODA should be stored without exposure to air because it gradually reacts with carbon dioxide to form ODA carbonate, which is white and crumbly in composition. 

More recently Hand et al. (ref. 9) have studied the decomposition reaction of N-chloro-a-amino acid anions in neutral aqueous solution, where the main reaction products are carbon dioxide, chloride ion and imines (which hydrolyze rapidly to amine and carbonyl products). They found that the reaction rate constant of decarboxylation was independent of pH, so they ruled out a proton assisted decarboxylation mechanism, and the one proposed consists of a concerted decarboxylation. For N-bromoamino acids decomposition in the pH interval 9-11 a similar concerted mechanism was proposed by Antelo et al. (ref. 10), where the formation of a nitrenium ion (ref. 11) can be ruled out because it is not consistent with the experimental results. Antelo et al. have also established that when the decomposition reaction takes place at pH < 9, the disproportionation reaction of the N-Br-amino acid becomes important, and the decomposition goes through the N,N-dibromoamino acid. This reaction is also important for N-chloroamino compounds but at more acidic pH values, because the disproportionation reaction... 

AMINEX A process for removing hydrogen sulfide and carbon dioxide from gas and LPG streams, by circulating an aqueous amine solution through bundles of hollow fibers immersed in them. Developed in 1991 by the Merichem Company, Houston, TX. 

GAS/SPEC CS-Plus A process for removing carbon dioxide and hydrogen sulfide from natural gas by washing with a solution of a special amine. Developed and offered by Dow Chemical Company. Operated since 1988. 

Beyond the density changes that can be used to control method modifications in SFC, the mobile phase composition can also be adjusted. Typical LC solvents are the first choice, most likely because of their availability, but also because of their compatibility with analytical detectors. The most common mobile phase modifiers, which have been used, are methanol, acetonitrile and tetrahydrofuran (THF). Additives, defined as solutes added to the mobile phase in addition to the modifier to counteract any specific analyte-column interactions, are frequently included also to overcome the low polarity of the carbon dioxide mobile phase. Amines are among the most common additives. 

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