Solvents alkanolamines

Scheme 7.6 Solvent-free enzymatic synthesis of fatty alkanolamines.

Alkanolamines, generally referred to as amines, are organic compounds of the form Hn-N-(R0H)3-n (3) the hydroxyl group generally provides for the compounds solubility in water, while the HN group provides the alkalinity in water solutions to cause the absorption of acid gases. Amine processes used commercially are shown in Table I. These compounds are chemical solvents they combine chemically with H2S, C02, and other sulfur compounds. They are customarily regenerated by the application of heat. 

Alkanolamines. Gas sweetening, ie, removal of hydrogen sulfide and carbon dioxide, using alkanolamines was patented in 1930. Several amine solvents are available as of the mid-1990s. The most widely used are monoethanolamine [141-43-5], diethanolamine [111-42-2], diglycolamine [929-06-6], and methyldiethanolamine [105-59-9]. Amine processes are generally applicable when hydrogen sulfide concentration in the feed gas is relatively low (eg,... 

Capital costs for a Sulfinol unit are lower than alkanolamine units that have the same capacity. This is because the equipment is smaller as a result of less foaming and lower circulation rates. However, certain treating applications may not be ideal for the Sulfinol process. A reclaimer may be needed to remove DIPA degradation products when C02 partial pressure is high. Also, aromatic and hydrocarbon co-absorption occurs when solvent -to-gas ratios are high260-... 

Solvent UCARSOL Alkanolamine Solution with Metal-Passivating Corrosion Inhibitors... 

The Shell Sulfinol Process is used for removal of acidic constituents such as H2S, CO2, COS, etc. from a gas stream. Improved performance over other processes is due to the use of an organic solvent, Sulfolane (tetrahydrothiophene dioxide), mixed with an aqueous alkanolamine. Relative proportions of Sulfolane, alkanolamine, and water, as well as the operating conditions, are tailored for each specific application. Simultaneous physical and chemical absorption under feed gas conditions is provided by this Sulfinol solvent. Regeneration is accomplished by release of the acidic constituents at near atmospheric pressure and a somewhat elevated temperature. The flow scheme (Figure 4) is very similar to that of an aqueous alkanolamine system since it involves only absorption, regeneration and heat exchange under typical alkanolamine treater conditions. 

Alkanolamines are ammonia-like organic compounds. When dissolved in water they form weak bases. The bases react with the acids formed when H2S and C02 dissolve in water. This acid-base reaction greatly enhances the solubility of the acid gases. Because the alkanolamines are weak bases, the process can be reversed. When the solutions are heated, the acid gases are liberated and the solvent regenerated. 

The excess air s introduction of oxygen degrades the principal chemical absorbents (alkanolamines) and increases solvent consumption. This degradation is also exacerbated by the presence of sulphur in the flue gas, e.g. from fuel oil. This is illustrated in Figure 6.2 and Table 6.4 which illustrates process flows and utilities consumption for the reduction of carbon dioxide in a flue gas to below 2% using a standard sorbent (MEA) and a solvent under development (SH amine) ... 

Alkanolamine MEA processes aMDEA Hot poptash processes Selexol Selexol Fluor solvent Fluor solvent Purisol Purisol Rectisol Rectisol Sulfinol D Sulfinol D... 

Nitrourea is decomposed quantitatively into cyanic acid and nitrous oxide when heated in aqueous solution. If primary or secondary amines are present, the products are alkylureas or N,N-diaIkylureas, respectively.Alcohol is used as a solvent for amines which are only slightly soluble In water. The yields in general are excellent (70-98%), and the reaction is preferred to the exchange with urea described above. Alkanolamines give hydroxyalkylureas in 85-95% yields." Nitrourea is conveniently prepared in 90% yield from urea nitrate."... 

The Sullinol process, developed by Shell in the early 1960s, is a combination process that uses a mixture of amines and a physical solvent. The Shell Sulfinol process is a regenerable amine process for acid gas removal. As the process uses a mixture of water, sulfolane, and one or more alkanolamine, removal capacity of COS, mercaptan s, and organic sulfides from gas streams is excellent by virtue of the improved physical solubility of these compounds in the solvent. A typical flow diagram of sulfinol process is shown in Figure 5.29.196... 

From time to time more solvents are being added to the lists that have not been included in previous compilations7,13,16,27. Such are certain hydroxylic solvents, studied by Gonqalvcs and coworkers98 with 5 for solvent polarities and with 8 for their EPD/HBA properties, and alkanolamines studied by Lagalante and coworkers99 with 7 and 8, respectively for these properties, as non-exclusive examples. 

A minor variant to the amine scrubbing process described above is the Sulfinol process, which still uses an alkanolamine base, diisopropanolamine (35%), but in a solvent consisting of a mixture of sulfolane (40%), tetramethy-lene sulfone (CH2)4S02, a good hydrogen sulfide solvent) and water [29]. Other processes are based on hydrogen sulfide absorption in aqueous alkaline carbonate solutions, such as the Catacarb and Benfield systems (Eqs. 9.16 and 9.17). 

Monoglycerides form an inverse hexagonal phase with glycerol, as in water [112], Mixtures of triethanolamine and oleic acid form a nonaqueous lamellar liquid crystal with a surfactant bilayer of soap and acid with intercalated ionized and unionized alkanolamine as solvent [113,114], Lamellar liquid crystals form analogously with dodecylbenzenesulfonic acid and triethanolamine [115]. 

Water based poly(ester-imide) wire enamels were developed in the 1960s and 1970s. The resins were made water soluble in different ways. Resins with a defined acid number were neutralized with alkanolamines [144-148] or ammonia [149]. In another process the poly(ester-imide) resins were submitted to an ami-nolysis with alkanolamines [150-153] or ammonia [154-156], when the resin network is more or less degraded. Solvents for this poly(ester-imide) is water and usually a small amount of high boiling solvents like N-methylpyrrolidon or diethylene glycol monomethylether. Titanium catalysts stable to hydrolysis, like titanium-ammonium lactate and titanium lactate, were used [157]. To improve thermal and mechanical properties, phenol blocked isocyanates can be added to the water based poly(ester-imide)s. The blocked isocyanates are dispersed by means of an ethoxylated nonylphenol and are added to the water based wire enamel. Improvement of the property level is claimed [158]. 

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