Diethanolamine systems

Diethanolamine Systems. Diethanolamine (DEA) is a secondary amine that has in recent years replaced MEA as the most common chemical solvent., s a secondary amine, DEA is a weaker base than MEA, and therefore DEA systems do not typically suffer the same corrosion problems. In addition, DEA has lower vapor loss, requires less heat for regeneration per mole of acid gas removed, and does not require a reclaimei. DEA reacts with H iS and COt as follows ... 

Bell (1975) used the C02-diethanolamine system to evaluate area-averaged mass fransfer performance of a range of smooth, mesh and perforated discs. Once again the smooth disc gave the lowest mass transfer coefficient, while the perforated and mesh discs were broadly similar. For all the discs a pronounced maximum coefficient was noted at a critical rotational speed. This phenomenon was asalbed to film breakdown in the peripheral regions of the discs as the rotational speed increased. The existence of peripheral dry areas was confirmed photographically. 

Work continues on improving the efficiency of this process, such as for freeing the alkan olamine from heat-stable salts that can form (125). Formulations have been developed which inhibit degradation of mono- and diethanolamine in processing (126). Models (127), computer programs (128), and kinetics and enthalpies (129—136) have been developed to help determine equiUbria of the acid gas—alkanolamine—water system. Additional references relate to the use of tertiary alkan olamines, such as triethanolamine, for gas conditioning (137—139). 

Activated tertiary amines such as triethanolamine (TEA) and methyl diethanolamine (MDEA) have gained wide acceptance for CO2 removal. These materials require very low regeneration energy because of weak CO2 amine adduct formation, and do not form carbamates or other corrosive compounds (53). Hybrid CO2 removal systems, such as MDEA —sulfolane—water and DIPA—sulfolane—water, where DIPA is diisopropylamine, are aqueous alkaline solutions in a nonaqueous solvent, and are normally used in tandem with other systems for residual clean-up. Extensive data on the solubiUty of acid gases in amine solutions are available (55,56). 

Since a-tocopherol destroys nitrite in the system in absence of the oil phase, we may postulate that the ineffectiveness of these two oil soluble inhibitors resulted from their absence from the aqueous phase. Diethanolamine is miscible with water and presumably its nitrosation occurs in the aqueous phase. There is a significant difference in the solubility characteristics of ascorbyl palmitate. The reducing portion of the molecule is water soluble. Thus the ascorbate moiety may be in the aqueous phase while the fatty acid tails may lie within the oil globules. The a-tocopherol and the BHA may well be effective if they are dispersed in the aqueous phase after preparation of the emulsion. This will be investigated in future experiments. 

R.Tauler and E. Casassas, Application of principal component analysis to the study of multiple equilibria systems — Study of Copper(ll) salicylate monoethanolamine, diethanolamine and triethanolamine systems. Anal. Chim. Acta, 223 (1989) 257-268. 

HS A family of gas purification processes developed by Union Carbide Corporation, based on the use of proprietary solvents known as UCARSOLs. UCARSOL HS-101, is based on methyl diethanolamine and is used for removing hydrogen sulfide and carbon dioxide from other gases. Ucarsol LH-101 is used in its Cansolv system for flue-gas desulfurization. 

Toxicology. In animal studies, target organs of diethanolamine (DEA) toxicity have included bone marrow, kidney, testis, skin, and central nervous system. 

Diethanolamine has been shown to inhibit choline uptake into cultured Syrian hamster embryo (SHE) and Chinese hamster ovary cells and to inhibit the synthesis of phosphatidylcholine in in-vitro systems in a concentration-dependent, competitive and reversible manner (Lehman-McKeeman Gamsky, 1999, 2000). Diethanolamine treatment caused a marked reduction in hepatic choline metabolite concentrations in mice following two weeks of dermal dosing. The most pronounced reduction was in the hepatic concentration of phosphocholine, the intracellular storage form of choline (Stott et al, 2000). Moreover, the pattern by which choline metabolites were altered was similar to the pattern of change that has been observed following dietary choline deprivation in rodents (Pomfret et al, 1990). Excess choline also prevented diethanolamine-induced inhibition of phosphatidylcholine synthesis and incorporation of diethanolamine into SHE cell phospholipids (Lehman-McKeeman Gamsky, 2000). 

Whole-body autoradiography of male Sprague-Dawley rats given intravenous injections (2.7 mg/kg bw) of 7V-nitroso[ C]diethanolamine showed an even distribution in most tissues except for tissue-bound radioactivity that was localized in the liver and the nasal olfactory mucosa. A lower level of labelling in the central nervous system probably indicated that 7V-nitrosodiethanolamine penetrated the blood-brain barrier poorly, while higher labelling in the kidney and urinary bladder may reflect elimination of 7V-nitroso[ C]diethanolamine in urine (Lofbeig Tjalve, 1985). 

The modification of silica gel with diethanolamine (DEA) resulted in a stable alkaline filter, capable to collect H2S, COS, CS2, S02, C02 and H20 from contaminated air.56 The presence of odorous mercaptanes and organic sulphides may be selectively determined, as these compounds do not react with the DEA and therefore are not collected on the filter. By means of this scrubber an automatic survey system has been developed allowing the detection and determination of the nature of odour nuisance, caused by industrial emissions of volatile organic sulphur compounds, up to the ppb-level. The system consists of two continuous, highly sensitive and fast responding sulphur analyzers. One of the detectors is equipped with an SO, scrubber and measures the total amount of non-S02 sulphur compounds. The other detects the organic S-compounds, using the amine-silica filter. 

The cooled process gas that leaves the Syngas Scrubber is fed to the Amine unit. The amine unit consists of an absorption-stripping system plus associated equipment. In this system a circulating amine stream (activated MDEA - or Methyl Diethanolamine) absorbs the C02 in the C02 Absorber. The amine is regenerated in the C02 Stripper with the C02 being recycled to the compressor. 

In an amine system, one way to increase absorption is to increase amine concentration. A higher amine concentration requires 1) more extensive filtration to keep the solution clean and 2) the addition of corrosion inhibitors and to minimize corrosion. Another option is to change from monoethanolamine (MEA) to methyl diethanolamine (MDEA)86. 

Shell-side effluent from the reforming exchanger is cooled in a waste-heat boiler, where HP steam is generated, and then flows to the CO shift converters containing two catalyst types one (4) is a high-temperature catalyst and the other (5) is a low-temperature catalyst. Shift reactor effluent is cooled, condensed water separated (6) and then routed to the gas purification section. C02 is removed from synthesis gas using a wet-C02 scrubbing system such as hot potassium carbonate or MDEA (methyl diethanolamine) (7). 

Benfield LoHeat System (UOP) [677], The high thermal efficiency of this two-stage adsorption process using lean and semi-lean solvent is achieved by recompression of the flash steam with an injector or a mechanical vapor compressor. UOP has also developed a number of other process configurations [404], [669], [678] -[680], The diethanolamine promoter enhances the mass transfer by carbamate... 

The photolability of nitrobenzenes has previously received comment, and reactions in the presence of carbon tetrachloride and diethanolamine have now been studied. In the former system the main products are chlorobenzene and hexachloroethane, with smaller amounts of CHCh, COCI2, and C2CI4. Nitrobenzene is photoreduced in the presence of the amine to give phenyl-hydroxylamine. The reaction is enhanced six-fold in the presence of 0.1 M benzophenone and is considered to proceed by way of hydrogen abstraction by the triplet nitro-arene from diethanolamine (which is degraded to glyoxal). 

Depending on whcih of the four types of alkanolamide is to be produced, the starting material could be either fatty acid, methyl ester, or triglyceride (coconut oil) and monoethanolamine or diethanolamine. Usually, a batch system of manufacturing is employed, as shown in Figure 20. 

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