Method of extracting dinitrogen pentoxide from its mixture with

Details Method of extracting dinitrogen pentoxide from its mixture with Method of extracting dinitrogen pentoxide from its mixture with

1992-04-16

1993-11-30

Heller, Gregory A.

Chemistry of inorganic compounds

Nitrogen or compound thereof

Oxygen containing

423235, 4233901, C01B 2122, C01B 2124, C01B 2138, C01B 2100

Patent

active

052662926

DESCRIPTION:

BRIEF SUMMARY
This invention relates to the extraction of dinitrogen pentoxide (N.sub.2 O.sub.5) from its mixture with nitric acid, and in particular to the extraction of N.sub.2 O.sub.5 from solutions of such mixtures in organic solvents.
It is known that concentrated solutions of N.sub.2 O.sub.5 in nitric acid can be prepared by the electrochemical oxidation of dinitrogen tetroxide (N.sub.2 O.sub.4) in concentrated nitric acid. This represents one of the most cost-effective methods of producing N.sub.2 O.sub.5 currently available.
According to USSR Inventor's Certificate SU-1089047A, a mixed N.sub.2 O.sub.5
itric acid solute may be precipitated from concentrated solutions of N.sub.2 O.sub.5 in nitric acid by the addition thereto of moderate amounts of cold liquid N.sub.2 O.sub.4. N.sub.2 O.sub.5 has a strong affinity for nitric acid, and in order to extract from the solute relatively pure N.sub.2 O.sub.5, the solute is sublimed at 5.degree. C. to 10.degree. C. and the sublimate condensed onto a cold surface at -20.degree. C. Once the acid-free solid N.sub.2 O.sub.5 has been prepared, it may then be dissolved in a suitable carrier, typically an inert organic solvent such as a chlorinated alkane, for subsequent use in a wide variety of nitration reactions.
There are a number of disadvantages associated with the method of N.sub.2 O.sub.5 extraction disclosed in SU-1089047A. Sublimation must be conducted at a reduced pressure of typically about 50 mm Hg in order to avoid the need for higher sublimation temperatures which would otherwise cause the N.sub.2 O.sub.5 to decompose rapidly. The build-up of condensed N.sub.2 O.sub.5 gradually reduces the thermal efficiency of the cold surface on which the sublimate forms. Any moisture present during the condensation of the N.sub.2 O.sub.5 sublimate and its subsequent dissolution in an organic solvent produces yet more nitric acid by reaction between the moisture and the N.sub.2 O.sub.5.
It is an object of the present invention to overcome the disadvantages associated with this aforementioned method.
Accordingly, a method of extracting N.sub.2 O.sub.5 from its mixture with nitric acid comprising the steps of: solvent, temperature sufficient to transfer at least part of the N.sub.2 O.sub.5 from the solution into the carrier gas, and second body of inert organic solvent at a temperature lower than that of step (b).
For the present method to be effective, the mixture preferably contains a minor amount of nitric acid i.e. less than 50% by weight of the total amount of N.sub.2 O.sub.5 and nitric acid, and will typically contain from 4 to 40% nitric acid. The mixture may, for example, comprise N.sub.2 O.sub.5 contaminated with nitric acid during it preparation by contact with moisture, or it may comprise an N.sub.2 O.sub.5 solute recovered from a mixture of N.sub.2 O.sub.4 and N.sub.2 O.sub.5 in nitric acid. Typically the first body of solvent will contain from 2 wt % to 20 wt % N.sub.2 O.sub.5 and up to 10 wt % nitric acid.
It has been found that by appropriate selection of contact temperature, N.sub.2 O.sub.5 readily transfers into the gas phase even when step (b) is performed at atmospheric pressure, leaving the relatively involatile nitric acid behind in solution within the first body of inert solvent. The presence of ozone in the carrier gas ensures that any N.sub.2 O.sub.4 produced by decomposition of the N.sub.2 O.sub.5 during its vapourisation and subsequent reabsorption in solvent is rapidly reconverted to N.sub.2 O.sub.5, so obviating the need to conduct step (b) at a pressure which is significantly sub-atmospheric.
Much if not substantially all of the ozone is subsequently dissolved in the second body of inert solvent along with the N.sub.2 O.sub.5 thereby increasing the effective thermal stability of the recovered N.sub.2 O.sub.5 and maintaining its purity.
Any moisture present in the carrier gas is converted in step (b) to relatively involatile nitric acid by reaction with N.sub.2 O.sub.5 and is rapidly absorbed by the first body of inert solvent. Nitric acid contaminatio

REFERENCES:
patent: 1348874 (1920-08-01), Guye
patent: 3044844 (1962-07-01), Maury et al.
Chemical Abstracts, vol. 97, No. 6, Aug. 1983 #97-43480b.
Chemical Abstracts vol. 101, No. 6 Aug. 1984 #101:40593f.
Chemical Abstracts, vol. 106 No. 16 Apr. 1987 122387j.

Affiliated with

Also associated with

Rating

Method of extracting dinitrogen pentoxide from its mixture with does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method of extracting dinitrogen pentoxide from its mixture with , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of extracting dinitrogen pentoxide from its mixture with will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2093656