US1050160A - Process of manufacturing concentrated nitric acid. - Google Patents

Description

Patented Jan. 14, 1913.

M. MOEST, R. M. VON BERNEOK 6; J. OPLL PROCESS OF MANUFACTURING GONGENTRATED NITRIC ACID. APPLICATION FILED JULY 26, 1911. 1,050,100.

U ITED sTA Es PATENT OFFICE,

MARTIN MOEST AND RUDOLF M'ULLER VON BERNECK, or HocHsT-oN-THE-MAIN, AND 'JOSEF OPL, or LoRsBncH, GERMANY, ASSIGNORS T0 FARBWERKE voRM. MEIsTER LUCIUS & BRfiNING, or HocHsT-oN-THE-MAIN, GERMANY, A CORPORATION OF G ANY.

PROCESS OF MANUFACTURING CONCENTRATED NITRIC ACID.

To all whom it may concern: I

Be it known that we, MARTIN MOEST, Ph, D., RonoLr MI'jLLER voN BERNECK, and JosEF OPL, chemists, citizens of the Empires of Germany and Austria-Hungary, respectively, the first two'residing at Hochst-onthe-Main, Germany, and the third at Lorsbach a. T., Germany, have invented certain new and useful Improvements in Nitric Acid of High Percentage and Processes of Making Same, of which the following is a specification.

By the method, hitherto in use in the manufacture of nitric acid, consisting in causing NO gases to act upon water in presence of oxygen, only a comparatively diluted nitric acid is obtained. Thus with mixtures of nitric oxid and air an acid of only -52 per cent. strength is produced. With regard to mixtures of pure nitrogen peroxid gas with oxygen, Foerster and Koch (see Zez'tsohm'ft fair ange'wandte Ohemie, 1908, page .2168) have shown that the highest concentration of nitric acid obtainable is an acid of about 68 per cent. strength, namely the acid of the lowest vapor-pressure. From their experiments and from theoretical considerations the said authors draw the following conclusion There is no doubt that the highest concentration of nitric acid obtainable by the action of nitrogen peroxid and excess of oxygen upon water at ordinary temperature, scarcely exceeds 69 per cent. In practice it was not possible to obtain in this manner an acid of a greater strength than 60-62 per cent. This fact is unfortunate, particularly because for industrial purposes there is principally required an acid of 70-80 per cent. strength for the preparation of the mixed acid mostly used for nitrating purposes, Whereas nitric acid of a percentage strength below 70 is employed only to a comparatively small extent.

esses for the concentration of' the dilute nitric acid obtained from oxids ofqnitrogen Specification of Letters Patent.

Application filed July 26, 1911.

p In consequence of this therev have been elaborated of late numerous proc Serial No. 640,647.

by their action upon water in presence of Patented Jan. 14, 1913.

excess of oxygen. These processes are however for the most part complicated andin any case expensive.

Now contrary to the technical and theoretical considerations hitherto entertained, we have found a process for manufacturing directly from nitrogen peroxid (or nitrogen tetroxid), water and oxygen at ordinary atmospheric pressure, a nitric acid containing 7 0 per cent. and more of I-INO This process, which constitutes our present invention,-

consists in enriching nitric acid obtained in the usual manner, for instance acid of 6062 per cent. strength, with nitrogen peroxid, which easily dissolves in the acid, and in then subjecting this nitric acid containing nitrogen peroxid, ina finely subdivided state to the action of oxygen. In consequence of the increased concentration of the N 0 the speed of the reaction is increased in the sense of the equation 2NO +H O HNO-l-HNO while at the same time the evaporation of I-INO which is antagonistic to the concentration, is checked by avoiding a considerable excess of oxyg en. The non-oxidized part of the nitrogen peroxid or of the nitrous acid, that maybe present in solution, is expelled by the oxygen introduced at the end of the reaction system, so that the nitric acid finally obtained is practically free from nitrous acid.

For carrying out our new process it is advantageous to use a system adapted to fulfil the following conditions :The first part of the system produces a nitric acid of simultaneously, if required, introducing oxygen; in the third part of the system oxygen is introduced for the purpose of converting nitrogen peroxid into nitric acid and expelling the unused oxids of nitrogen. In practice it is advantageous to work on the counter-current principle and continuously in such a manner that at one end of the system water is introduced and at the other end the concentrated nitric acid is drawn oli' whereas the oxygen and the nitrogen peroxid gases pass in the opposite direction. The several parts of the system may consist of the known trickling-towers or of a system of vessels in which, either by means of spraying nozzles, agitators or any other suitable device, the nitric acid containing N0 is brought into intimate contact with the oxygen. The nitrogen peroxid or nitrogen tetroxid may be introduced at suitable points either inliquid or vaporous form or mixed with oxygen. It has been found particularly advantageous to introduce the nitrogen peroxid in such a manner that the current of oxygen is passed through liquid nitrogen peroxid whereby exactly regulated quantities of the nitrogen peroxid can be introduced into the reaction system by operating at determined temperatures. The oxygen is introduced either exclusively at the end of the system or at several points as required. When starting from nearly pure oxygen and nearly pure nitrogen peroxid in proper proportions, it is possible, as both gases are consumed, to carry on the process in such a manner that at the end of the system only very small quantities of gas escape so that losses owing to entrainment of nitric acid vapors are entirely avoided. In practice, however, it is advantageous to work with a small excess of oxygen which,

a in order to avoid losses of oxygen is reintroduced into the process by suitable devices. It is not necessary to charge the whole system with pure oxygen, but there may be prepared nitric acid of a lower concentration in the usual manner from N0 water and air, and the dilute nitric acid thus obtained may be further treated, as above indicated, with NO and oxygen; thus a considerable saving of oxygen is effected. Of course it is possible to combine these arrangements.

The accompanying drawing illustrates suitable apparatus for carrying out the process, the figure being a side elevation. The absorption chambers T T T and T in which the nitrogen-oxids are converted into nitric acid with the aid-of oxygen and water, are connected with each other by gaspipes G. In chamber T the non-oxidized nitric oxid gases from the nitric acid are expelled, with the aid of oxygen. The introduction of the water and the dilute nitric acid is eifected at H O; that of the nitricoxids-alone or mixed with oxygenat rea ies N0 and of the oxygen at 0. These gas-es flow through the system in the direction'indicated by the arrows beside pipes Gr, while the water and the dilute nitric acid pass through the apparatus in the reverse direction, from the bottom of one chamber, through the lifting device, to the top of the next chamber. D D and D are devices for lifting the nitric acid loaded with nitric gases. The finished product is discharged from chamber T at B. In the reaction which takes place, two molecules of NO require one molecule of water and half a molecule of oxygen. Gonsequently, there are required for the oxidation of 92 grams of N0 into nitric acid 12 liters of oxygen. In practice, a small excess of oxygen is employed so that no nitrogen oxids escape from the apparatus, but only oxygen. Theinitial temperature is that of the surrounding air, and as the reaction is attended by evolution of heat, a rise of the tempreature gradually sets in which depends on the radiation and on the quantity of the nitric-oxid used, per time-unit. We have found that the best reaction takes place if 5-l0 kg. of nitrogen peroxid per cubic meter of the reaction area and per hour are employed, according to the desired concentration of the acid. If it is intended to prepare a strong acid, less of the nitrogen peroxid should be used than if an acid of a lower strength is desired.

Having now described our invention what we claim is: 1

1. The process of manufacturing, in a direct way, highly concentrated nitric acid, which consists in enriching the dilute nitric acid, obtained in the usual manner, with nitrogen peroxid and treating this mixture with oxygen.

2. The process of manufacturing, in a direct way, highly concentrated nitrlc acid, 105 which consists in enriching the dilute nitric acid, obtained in the usual manner, with nitrogen peroxid in a gaseous form, and treating this mixture with oxygen.

3. The process of manufacturing, in a di- 110 rect way, highly concentrated nitric acid, which consists in enriching the dilute nitric acid, obtained in the usual manner, with nitrogen peroxid which is introduced into the nitric acid in a vaporous form with the aid 115 of a current of oxygen, and treating this mixture with oxygen.

4. The process of manufacturing, in a direct way, highly concentrated nitric acid,

which consists in enriching the dilute nitric 5. The process of manufacturing, in a di- In testimony whereof, we aflix our signa- 10 rect way, highly concentrated nitric acid, tures in presence of two witnesses. which consists in treating dilute nitric acid,

obtained in the usual manner, with a mix- MARTIN-MQEST' ture of nitrogen peroxid and oxygen and g ggfigfi VON BERNEGK" further treating this mixture With oxygen,

introduced at the end of the reaction-appa- Witnesses:

ratus, thereby expelling the non-oxidized JEAN GRUND,

nitric oxid gases from the nitric acid. CARL GRUND.

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