Diethanolamine degradation

Hakka, L. E., Singh, K. P., Bata, G. L., Testart, A. C., and Andrejchyshyn, W. M., 1968, Some Aspects of Diethanolamine Degradation in Gas Sweetening, Paper presmted at Canadian Natural Gas Processing Association meeting. May 9. 

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). 

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. 

Diethanolamine is a favored absorbent due to its lower corrosion rate, smaller amine loss potential, fewer utility requirements, and minimal reclaiming needs. Diethanolamine also reacts reversibly with 75% of carbonyl sulfides (COS), while the mono- reacts irreversibly with 95% of the COS and forms a degradation product that must be disposed of. 

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). 

Degradation of amoxicillin in aqueous solution containing phosphate [45], sorbitol and zinc sulphate [46] or diethanolamine and zinc sulphate [47] gave a product which was assumed from its spectroscopic properties, and by analogy with ampicillin degradation, to be the piperazine-2,5-dione, VI. This was subsequently confirmed by characterisation of the isolated product [48,49], which was shown [48] to be formed in significant amount on degradation of concentrated aqueous solutions of amoxicillin sodium... 

Conversion to the piperazine-2,5-dione with sorbitol/zinc sulphate [46] or diethanolamine/zinc sulphate [47], foUowed by measurement at 322nm in 1M NaOH, provided a stability indicating method for amoxicillin. Any piperazine dione present as impurity was corrected for by a sample blank and no interference was found from acid or alkali degradation products or from amoxicUlin oligomers. 

We performed a series of experiments to elucidate the MOA of the novel TNAP inhibitors. The catalytic mechanism by which TNAP degrades PR consists of rapid phosphorylation of the active site in the presence of the phospho-donor substrate and a rate-limiting dephosphorylation by the phospho-acceptor substrate, either water or amino-containing alcohols (Fig. 5). All the TNAP inhibitors reported to date are uncompetitive with respect to phos-pho-donors and are likely to be non- or uncompetitive with diethanolamine (DBA). The latter conclusion is based on the fact that the majority of the alkaline phosphatase assays are performed in the presence of saturating concentrations of DBA or other phosphor-acceptors. 

A. Chakma and A. Meisen [Can. J. Chem. Eng.. 75, 861-871 (1997)] studied the kinetics of the hquid phase degradation of methyl diethanolamine (A) at 18°C at elevated pressures in an autoclave. Test the following data to ascertain whether they are consistent with zero-, first-, or second-order kinetics. Prepare plots of the data using coordinates that should yield straight lines if the presumed rate expression is correct Report the value of the rate constant corresponding to the proper value of the order of the reaction. Comment on the shapes of the plots. 

Systems handling mixtures of the two fall between these two extremes if the gases contain at least 1 vol.% H2S. Corrosion in amine plants using monoethanolamine is more severe than in those using diethanolamine, because the former is more prone to degradation. Corrosion is not caused by the amine itself, but is caused by dissolved hydrogen sulfide or carhon dioxide and by amine degradation products. 

In [74], a method of reclaiming of PUR flexible foam waste by grinding of foam scraps and heating in the presence of mono- and diethanolamine at a temperature of 130-150°C is described. The reaction process was considerably faster when monoethanolamine was used at elevated temperature. After the completion of the process, the degradation product underwent separation into... 

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