Nitrates denitration

Rayon was first made by denitration of cellulose fibers (Chardonnet process). The cellulose was first reacted with a mixt of nitric and sulfuric acids to form NC, The prod was then dissolved in a mixt of eth and ethanol and spun into yarn by a "dry spinning process. In some instances the yarn was denitrated by alkaline hydrosulfites, neutralized and then w washed and dried (Ref 9). See also under "Cellulose Nitration, Denitration in Vol 2, C118-R to C119-R... 

It is clear therefore that ESCA provides a new dimension to this complex problem of the nitration-denitration of cellulose materials and the work described here provides a strong basis for the study of the even more complex systems represented by double and triple based propellant formulations. 

Hoh and Wang (1980) reported the rate of extraction of nitrate (denitration) by a solution of 75% tributyl phosphate diluted with kerosene and the rate of stripping of nitrate (acid recovery) from nitrate-loaded TBP with water. The experiments carried out in a mixing vessel indicate an optimum rpm for extraction. Their experimental observations can be explained by the results of Sheka and Kriss (1959) where HNO3 -TBP predominates at nitric acid concentration up to 4 M and 3HNO3 TBP is the dominant species up to 9 M nitric acid concentration. The first extraction period is the rate controlling step. 

Sir Joseph Swan, as a result of his quest for carbon fiber for lamp filaments (2), learned how to denitrate nitrocellulose using ammonium sulfide. In 1885 he exhibited the first textiles made from this new artificial sHk, but with carbon fiber being his main theme he failed to foUow up on the textile possibihties. Meanwhile Count Hilaire de Chardoimet (3) was researching the nitrocellulose route and had perfected his first fibers and textiles in time for the Paris Exhibition in 1889. There he got the necessary financial backing for the first Chardoimet silk factory in Besancon in 1890. His process involved treating mulberry leaves with nitric and sulfuric acids to form cellulose nitrate which could be dissolved in ether and alcohol. This collodion solution could be extmded through holes in a spinneret into warm air where solvent evaporation led to the formation of soHd cellulose nitrate filaments. 

In TBP extraction, the yeUowcake is dissolved ia nitric acid and extracted with tributyl phosphate ia a kerosene or hexane diluent. The uranyl ion forms the mixed complex U02(N02)2(TBP)2 which is extracted iato the diluent. The purified uranium is then back-extracted iato nitric acid or water, and concentrated. The uranyl nitrate solution is evaporated to uranyl nitrate hexahydrate [13520-83-7], U02(N02)2 6H20. The uranyl nitrate hexahydrate is dehydrated and denitrated duting a pyrolysis step to form uranium trioxide [1344-58-7], UO, as shown ia equation 10. The pyrolysis is most often carried out ia either a batch reactor (Fig. 2) or a fluidized-bed denitrator (Fig. 3). The UO is reduced with hydrogen to uranium dioxide [1344-57-6], UO2 (eq. 11), and converted to uranium tetrafluoride [10049-14-6], UF, with HF at elevated temperatures (eq. 12). The UF can be either reduced to uranium metal or fluotinated to uranium hexafluoride [7783-81-5], UF, for isotope enrichment. The chemistry and operating conditions of the TBP refining process, and conversion to UO, UO2, and ultimately UF have been discussed ia detail (40). 

Fig. 3. Pilot-plant fluidized-bed denitiatoi for denitration of U02(N0 )2 bHjO where UNH = utanyl nitrate liexahydrate (40),...

Methylation of free OH groups, followed by denitration, hydrolysis, reduction, and glc analysis has been suggested as a method for determining the location of nitrate (82). This method has been suggested for CP and CS (82) as the phosphate and sulfate groups are stable to methylation and can then be removed. Periodate oxidation has been used to determine the DS of CS (81). 

Process (3) may be slow, hence under industrial conditions it may be broken off before equilibrium is established. This means that chemical reaction (3) is not completed. As a final product, a not very homogeneous nitrocotton is obtained. The higher the nitrating temperature, the more rapid the denitration process, the sooner the reaction balance is established, and hence the more uniform the product ... 

Precipitation Processes. Plutonium peroxide precipitation is used at Rocky Flats to convert the purified plutonium nitrate solution to a solid (14) the plutonium peroxide is then calcined to Pu02 and sent to the reduction step. The chemistry of the plutonium peroxide precipitation process is being studied, as well as alternative precipitation processes such as oxalate, carbonate, fluoride, and thermal denitration. The latter method shows the most promise for cost and waste reduction. 

In an alternative method of preparing m/vo-dihydroxyanthraquinonedisulfonic acid by heating the title compound with oleum to effect simultaneous hydrolysis, denitration and sulfonation of the nucleus, there is the possibility of formation of methyl nitrate from the scission fragments. 

Because the a-nitroketones are prepared by the acylation of nitroalkanes (see Section 5.2), by the oxidation of (3-nitro alcohols (Section 3.2.3), or by the nitration of enol acetates (Section 2.2.5), denitration of a-nitro ketones provides a useful method for the preparation of ketones (Scheme 7.10). A simple synthesis of cyclopentenone derivatives is shown in Eq. 7.66.76... 

Purified mtALDH catalysed the stoichiometric formation of 1,2-GDN and nitrite from GTN, in a reaction that was shown to be dependent on the presence of thiols. It was argued that reductive denitration of GTN involves interaction of one of two adjacent active site thiols with GTN to yield an -SNO2 group, which then reacts with the other thiol to yield nitrite and a disulfide. In a final, essential step the inactive disulfide is converted back to two thiols by external thiol compounds (Scheme 2.2). It is interesting to note that this mechanism is essentially that foreseen by Needleman and colleagues in their proposed nitrate receptor (see earlier). 

Scheme 2.2 Mechanism of reductive denitration of organic nitrates (RONO2) to nitrite, catalysed by mtALDH. Adapted from Chen et al. [95].

Needleman, P., Blehm, D J., Rotskoff, K. S., Relationship between glutathione-dependent denitration and the vasodilator effectiveness of organic nitrates. J. Pharmacol. Exp. Then 237 (1969), p. 296-288... 

Fig. 9.4. Postulated mechanisms in the thiol-dependent denitration of organic nitrates...

Fig. 9.6. Postulated mechanisms in the cytochrome P450 catalyzed reductive denitration of organic nitrates. Pathway a shows the hypothetical mechanism for the reduction of organic nitrates to organic nitrites, whereas Pathway b presents the same reaction for organic nitrites.

N. Ogawa, T. Hirose, K. Fukushima, T. Suwa, T. Satoh, GSH-Independent Denitration of the Nitrate Ester of a Dihydropyridine Derivative in Rabbit Hepatic Cytosol , Biochem. Pharmacol. 1995, 49, 141 -146 N. Ogawa, T. Flirose, K. Fukushima, T. Suwa, T. Satoh, Metabolism of a Nitrate Ester, Dihydropyridine Derivative in Rabbit Hepatic Microsomes and Cytosol , Xenobiotica 1995, 25, 283-290. 

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