Electrochemical generation of dinitrogen pentoxide in nitric aci

Details Electrochemical generation of dinitrogen pentoxide in nitric aci Electrochemical generation of dinitrogen pentoxide in nitric aci

1991-07-23

1993-01-26

Niebling, John

Chemistry: electrical and wave energy

Processes and products

Electrostatic field or electrical discharge

204103, C25B 100

Patent

active

051819961

DESCRIPTION:

BRIEF SUMMARY
This invention relates to a process for the electrochemical generation of dinitrogen pentoxide (N.sub.2 O.sub.5) in nitric acid.
It has been known for many years that N.sub.2 O.sub.5 can be produced by the simultaneous anodic oxidation of dinitrogen tetroxide (N.sub.2 O.sub.4) in nitric acid and cathodic decomposition of nitric acid. Such reactions are conveniently conducted in electrochemical cells, in which the following principle reactions take place +2H.sup.+ +2e O
In practice, in order to prevent the decomposition of the N.sub.2 O.sub.5 product, the anode and cathode reactions are usually separated by a membrane which keeps apart the N.sub.2 O.sub.5 formed at the anode from the water formed at the cathode. The membrane therefore effectively divides the interior of the cell into an anode space and a cathode space.
One problem associated with known processes which exploit these electrochemical reactions in the production of H.sub.2 O.sub.5 in nitric acid, is that the current efficiency of these processes, which is the ratio of the actual mass of N.sub.2 O.sub.5 liberated in the anode reaction by a given current between the anode and cathode to that which should theoretically be liberated according to Faraday's Law, has hitherto found to be low leading to high production costs. This problem has lead to the formulation of processes designed to increase current efficiency and reduce specific power consumption.
One such process is described in German Patent No. DE-884,356 (Wendlant et al). N.sub.2 O.sub.4 in nitric acid is continuously added to both the anode and cathode spaces either side of a permeable membrane in a electrochemical cell, and the product acid containing N.sub.2 O.sub.5 is continuously drawn off from the anode space before the complete anodic conversion therein of tetroxide to pentoxide. A disadvantage of this process is that although higher current efficiencies and lower specific power consumptions are reported by utilising an incomplete conversion of tetroxide to pentoxide, the appreciable amounts of tetroxide left over at the end of anodic oxidation represent a significant reduction in the overall yield of N.sub.2 O.sub.5 over that which is theoretically possible, and constitute an unwanted contaminant in the product acid.
More recently, in a further batch process described in U.S. Pat. No. 4,432,902 (Coon et al) some improvement in current efficiency is reported by maintaining a carefully controlled potential difference between the anode and cathode spaces. However, the relatively complex control system employed by Coon et al is not readily adapted for use in semi-continuous and continuous methods of production, which means that the usefulness of this technique is generally restricted to small scale production of N.sub.2 O.sub.5.
It has now been discovered that the problem of contamination with N.sub.2 O.sub.4 can be largely overcome by the partial use of cationic ion exchange membranes between the anodic and cathodic spaces, which are found to retain N.sub.2 O.sub.5 within the anodic space but permit leakage of N.sub.2 O.sub.4 contamination from the anodic space to the cathodic space. This has in turn made it possible to produce highly concentrated mixtures of N.sub.2 O.sub.5 in nitric acid which have hitherto not been attainable by the aforementioned known processes and at the same time permit migration of N.sub.2 O.sub.4 liquid from the anode to the cathode liquid.
According to the present invention there is provided a method for the electrochemical generation of dinitrogen pentoxide (N.sub.2 O.sub.5) by the simultaneous anodic oxidation of N.sub.2 O.sub.4 in nitric acid and cathodic decomposition of nitric acid, wherein the N.sub.2 O.sub.5 is generated in two production stages, a first stage in which the anodic and cathodic reactions are separated by an anionic or a non-ionic, semi-permeable ion exchange membrane and a second stage in which the product of the anodic reaction from the first stage is subjected to further anodic oxidation, the anodic and cathodic reactions of the secon

REFERENCES:
patent: 4432902 (1984-02-01), McGuire et al.
patent: 4443308 (1984-04-01), Coon et al.
patent: 4525252 (1985-06-01), McGuire et al.

Affiliated with

Also associated with

Rating

Electrochemical generation of dinitrogen pentoxide in nitric aci does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Electrochemical generation of dinitrogen pentoxide in nitric aci, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electrochemical generation of dinitrogen pentoxide in nitric aci will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1410943