Solvent degradation

The selective epoxidation of ethylene by hydrogen peroxide ia a 1,4-dioxane solvent ia the presence of an arsenic catalyst is claimed. No solvent degradation is observed. Ethylene oxide is the only significant product detected. The catalyst used may be either elemental arsenic, an arsenic compound, or both. 

In a resin plant, solvents were directed from storage tanks to a blender by means of solvent charging manifold. Because of the poor panel layout and labeling of the charging manifold, a worker made connections that pumped solvent to blender 21A instead of 12A as directed by the instructions. An earlier error had left the valve open from the charging manifold to blender 21A and hence the misdirected solvent degraded a batch already in the blender (this example will be analyzed in more detail in Chapter 7). 

The corrosion resistance of lithium electrodes in contact with aprotic organic solvents is due to a particular protective film forming on the electrode surface when it first comes in contact witfi tfie solvent, preventing further interaction of the metal with the solvent. This film thus leads to a certain passivation of lithium, which, however, has the special feature of being efiective only while no current passes through the external circuit. The passive film does not prevent any of the current flow associated with the basic current-generating electrode reaction. The film contains insoluble lithium compounds (oxide, chloride) and products of solvent degradation. Its detailed chemical composition and physicochemical properties depend on the composition of the electrolyte solution and on the various impurity levels in this solution. 

Many pesticides are moderate to weak acids. Strong acid pollutants are fully ionised at ambient pH. Examples include trifluoroacetic and chloroacetic acids, whose use as herbicides has been banned but which still occur as solvent degradation products [16], or the pesticide 2,4,5-trichlorophenoxyacetic acid (P 2.83). 

In the radiolysis of nitric acid, HNO2 and H2O2 are formed. They strongly affect the solvent degradation, oxidation states of metal ions, and corrosion condition of the material. However, HNO2 and H2O2 are not coexisting because the next reaction will take place. 

The products of the selective electrochemical fluorination of butadiene with platinum electrodes in amine/ HF mixtures, particularly Et,N 3HF, were 3,4-difluorobut-1-cnc and 1,4-difluorobut-2-ene in a ratio of 1 2, 2.3-dimethyIbut-2-enc gave 2.3-difluoro-2,3-dimelhylbutane (yield 22%), while 2-mcthylbut-2-ene gave 2,3-difluoro-2-methyIbutanc (yield 23%) and 2,2-difluoro-3-methylbutane (yield 11 %). Oct-1-ene could not be fluorinated instead, the solvent degraded. Volatile degradation products were acetaldehyde, acetyl fluoride and fluorocthane. 

The primary separation of plutonium and uranium from the fission products involves a solvent extraction with 30 vol % TBP at room temperature. The activity levels in this separation are quite high ( 1700 Ci/L for the fission products) and the aqueous waste, which contains 99+% of the fission products, is a high-level waste. Am and Cm are not extracted and Np is partially extracted. Because of the high radiation levels, there are radiolysis problems with TPB, leading to solvent degradation. Primary products of the radiolysis of TBP are the dibutyl- and monobutylphosphoric acids along with phosphoric acid. These degradation products are removed in the solvent purification steps. 

The solvent was loaded with 137Cs and subsamples were stored on a shaker table while in contact with the extract, scrub, or strip aqueous phases. Evidence of solvent degradation was evaluated for exposure times of 83 days this resulted in estimated solvent doses of 1.24 Mrad, equivalent to the dose expected to be received during 16.5 years of operation at the SRS plant. 

Distribution of cesium in the batch tests remained constant within experimental error in addition, no third-phase formation was observed. The solvent concentrations of calix[4]arene-bis-(rm-octylbenzo-crown-6) and l-(2,2,3,3-tetrafluoroproproxy)-3-(4-sec-butylphenoxy)-2-propanol remained constant within experimental error. Solvent degradation with irradiation was evidenced by a decrease TOA concentration decrease and an degradation product (4-ver-butyl phenol) increase in the solvent phase. No decline in extraction or scrubbing performance of the irradiated solvents was observed. The stripping performance of the solvent was seriously impaired with irradiation however, a mild caustic wash and replenishment of the TOA concentration restored the ability to strip the irradiated solvent. 

However, the conditions are often far from those of industrial situations. In order to better simulate solvent degradation during the PUREX process, a test loop was created in the 1990s in a CEA laboratory (Fontenay-aux-Roses, France), with the EDIT loop (Extraction Desextraction Irradiation Traitement) (21, 22). The laboratory simulation of industrial conditions consisted of a succession of representative physical and chemical treatments after the irradiation of the solvent (i.e., alkali and acid treatments, distillation). Indeed, these treatments can modify the final solvent composition because of the elimination of some compounds or the occurrence of secondary reactions. A few years later, the MARCEL (Module Avance de Radiolyse dans les Cycles d Extraction Lavage) test loop was built at Marcoule to follow the regeneration efficiencies of degraded solvents involved in actinide separation processes (4, 5). 

Stieglitz, L., Becker, R. 1982. Chemical and radiolytic solvent degradation in the PUREX process, in Nukleare Entsorgung Nuclear Fuel Cycle-, Baumgartner, F., Ebert, K., Gelfort, E., Lieser, K.H. Eds. Verlag-Chemie Weinheim, Deerfield Beach, EL, Basel, 333-350. 

Minimizes solvent degradation Minimizes solvent inventory Proven in nuclear industry... 

K. L. Tyczkowska, R. D. Voyksner, and A. L. Aronson, Solvent degradation of cloxacillin in vitro—tentative identification of degradation products using thermospray LC-MS, J. Chromatogr., 594 195 (1992). 

Some general applications of TG-FTIR are evolved gas analysis, identification of polymeric materials, additive analysis, determination of residual solvents, degradation of polymers, sulphur components from oil shale and rubber, contaminants in catalysts, hydrocarbons in source rock, nitrogen species from waste oil, aldehydes in wood and lignins, nicotine in tobacco and related products, moisture in pharmaceuticals, characterisation of minerals and coal, determination of kinetic parameters and solid fuel analysis. 

Earlier work at Mobil and other laboratories (4, 5) had identified several processes responsible for solvent degradation (e.g. hydrogen transfer, cracking, isomerization, alkylation and condensation). In general, each of these processes converts a molecule which is useful in the liquefaction process to one which is less useful. Each of these processes can lead to both changes in structure and the physical properties of the solvent components. 

From Mann s review, it is clear that the anion and the electrode material have a pronounced effect on the oxidation potentials of the nonaqueous systems. The metals to which the highest potentials can be applied in nonaqueous systems are obviously the noble metals (Pt, Au). The limiting reaction when the anions are halides (Cl-, Br, I ) was found to be their oxidation to the elemental form. When the anion is C104 , its oxidation onset at potentials above 1.5 versus Ag/ Ag+ may promote further intensive solvent degradation, as was found with ACN. It is important to note that using BF4 instead of C104- in ACN (which is an important and useful nonaqueous solvent in electrochemistry) extended its anodic stability limit by 2 V. 

Other solvent degradation products derived from the diluent as well as from TBP may arise. Butyl lauryl phosphoric acid (HELP) has been used as a model for diluent derived diesters of phosphoric acid and at concentrations above 2xlO M enhances Zr extraction by TBP. HELP is not removed by alkali washing of the solvent but BLP is transferred into water at low ionic strength. Dialkylphosphorane complexes of Zr may also arise from irradiation and can stabilize emulsions. Diluent derived hydroxamic acids are present at too low a concentration (10 -10 M) to completely account for the extent of zirconium retention which occurs in... 

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