Nitrates, pyrolysis

In the case of organic nitrate pyrolysis, the reaction proceeds by O-N bond homolysis... 

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). 

Cobalt(Il) dicobalt(Ill) tetroxide [1308-06-17, Co O, is a black cubic crystalline material containing about 72% cobalt. It is prepared by oxidation of cobalt metal at temperatures below 900°C or by pyrolysis in air of cobalt salts, usually the nitrate or chloride. The mixed valence oxide is insoluble in water and organic solvents and only partially soluble in mineral acids. Complete solubiUty can be effected by dissolution in acids under reducing conditions. It is used in enamels, semiconductors, and grinding wheels. Both oxides adsorb molecular oxygen at room temperatures. 

Houser and Lee studied the pyrolysis of ethly nitrate using a stirred flow reaetor. They proposed the following meehanism for the reaetion ... 

Attempts to prepare 6-hydroxybenzofuroxan by demethylation of 5-methoxybenzofuroxan, by pyrolysis of 4-azido-3-nitrophenol, and by hypochlorite oxidation of 4-amino-3-nitrophenoD failed. This rather unstable compound was finally prepared by hydrolysis of 5-acetoxybenzofuroxan its tautomeric possibilities are numerous, but from the similarity of its ultraviolet spectrum to that of 5-methoxybenzofuroxan it was considered to be largely in the hydroxy form. It is a fairly strong acid, of pK 6.76 (cf. 5-hydroxybenzo-furazan, pK 7.28). 7-Hydroxy-4,6-dinitrobenzofuroxan has been reported as arising from oxidation and nitration of dinitrosoresorcinol monooxime (tetraoxocyclohexene trioxime). ... 

The precipitation step may be replaced by spray drying of a homogeneously stirred solution of, e.g., nitrates [31], or by spraying the precursors into a very hot flame at about 1500-2200 °C. This method is called flame pyrolysis. 

Dinitromphtkaiene (2,3-DNN). Yei needies from MeOH, mp 170.5-1.0° (Refs 8 23) CA Registry No 1875-634. It is prepd by bromination of 5,6-dinitro-1,2,3,4-tetrahydro-naphthalene followed by dehydrohalogenation (Ref 23) or by nitration of a naphthalene-hexachlorocyclopentadiene adduct (Diels-Alder), followed by pyrolysis to regenerate the 2,3-DNN (Ref 58)... 

Houser and Lee [J. Phys. Chem., 71 (3422), 1967] have studied the pyrolysis of ethyl nitrate using a stirred flow reactor. They iiave proposed the following mechanism for the reaction. 

In the analysis of diethylzinc, a 1 ml sample is cooled to — 196°C and treated with 2 ml of ethanol to give the ethoxide. During subsequent conversion to zinc nitrate (prior to pyrolysis to the oxide) by treatment with 3 ml of 30% nitric acid, cooling must be continued to avoid an explosion hazard. 

The palladium and magnesium nitrates modifier makes it possible to apply thermal pretreatment temperatures of at least 900-1000 °C for all investigated elements. For most elements this modifier supports substantially higher pyrolysis temperatures than did the matrix modifier recommended previously by Perkin-Elmer [688]. These higher pyrolysis temperatures allow for effective charring of biological matrices and removal of most inorganic concomitants prior to analyte element volatilisation. 

Upon flash vacuum pyrolysis or under silver nitrate catalysis, a variety of 2-ethenyl-sub-stituted cydopropylamines 146 cleanly undergo a vinylcyclopropane to cyclopentene rearrangement [129] and afford high yields (up to 95%) of 4-aminocyclopent-l-enes 147, some of which have unprecedented substitution patterns (Scheme 11.37) [130],... 

Pyrolysis of ethyl nitrate. Data from a CSTR... 

P2.03.12. PYROLYSIS OF ETHYL NITRATE. DATA FROM A CSTR... 

A chain reaction was proposed for the pyrolysis of ethyl nitrate Houser Lee ( J Phys Chem 1 3422, 1967) ... 

Nitration of various phenyl-49 and benzyl-phosphine60 oxides (59) has been described, and the P=0 group found to be mem-directing49 in the former case. Pyrolysis of the acyl azide (60)51 takes the course shown. 

Copper(II) oxide occurs in nature as the mineral tenorite. It may be prepared by pyrolysis of copper nitrate, copper carbonate or another oxo copper salt... 

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