US2124257A - Process for vacuum distillation of hydrogen peroxide - Google Patents

Description

J. MERCIER 2,124,257

GEN PEROXIDE July 19, 193s.

PROCESS FOR VACUUM DISTILLATION OF HYDRO Filed Aug. 12, 1955 Invenfor.- Y

Patented July 19,` 1938 UNITED STATES PATENT ori-ICE- PROCESS `OR VACUUM DISTILLATIONOF HYDROGEN PEROXIDE Jean Mercier, NeuiilysurSeine,' France Application .August 12,1935, serial No.'s5;s9s

y i' In France August 21, 1934 1 claim. (ci. 20a- 52) f The object of the present invention is aprocess 'forthe vacuum distillation of easily decomposable liquids, vtogether with an apparatuslto perform thefsame.

This operation'v has always encountered serious dicultiesin practise. In particular it has always been found extremely. difiicult to obtain hydrogenperoxidc by vacuum distillation, when y starting from aqueous solutions of compounds containing active oxygen, due chiefly to the f acility with which hydrogen peroxide decomposes in the presence -oflperacids The fact that .the vapour pressure of hydrogen peroxide is lower than that of `water .also causes These have necessitated main-r grave diiiculties. ytaining an optimum .ratio between the'quantities of water and hydrogen peroxide to be evaporatedv simultaneously. On the other hand .it is very important to prevent the solidication oi' the reagents owing to the evaporation of water proceeding too far.

In the processes hitherto knowmin which the liquid to be distilled is sucked through the evaporator by means of vacuum, and its quantity regulated by means of injectors, cocks or capillary tubes, the conditions prevailingin the evaporator are always irregular. These'drawbacks are particularly applicable to the working of large in dustrial units .formed of a great number of evaporating tubes.

The .present invention consists in a process of I l evaporation such that the same degree of vacuum is maintained at every point in the apparatus, all the parts of .which (as for instance feed-tanks,

. evaporators, collecting vessels etc.) are connected 'to the same vacuum pipe line. ,v By this means the process is carried out in such a manner that the evaporator throughout the whole vapparatus is always uniform..

In the preferred manner of putting the invention'into execution, the movement of the liquid in the apparatus is not obtained as formerly by applying a difference ofv `pressure between the inlet and the outlet, but by employing a difference of temperature. To eifect this one employs a system of communicating vessels, one of which is a reservoir of any desired shape and capacity,

the otherV being one or more heated tubes. The difference in temperature thusA established between the part of the apparatus which is heated and the part not heated results in imparting a movement to the liquid of any desired speed simply by regulating the temperature of the hot tube or tubes which are situated between the feed-'tank and the evaporator. 'I'his speed is best Vbeing'joined to the same vacuum piping c.

regulated to coincide with that which will give sulcient bubbles of steam t'o cause the solution to enter the evaporator in the form of an emullsion and not in the form of a liquid layer, thus in turn causing the entire s uriace of the evaporating '5 tubes to be filled with a small quantity of solution. According tothe invention one maintains uniform conditions in the evaporator by maintaining the same reduced pressure atkthe inlet and the outletof the said evaporator, byemployl0 ing a speed for the circulation of the solution which isindependent of the suction by vacuum, c and lastly by maintaining` the physical conditions ofthe solution homogeneous. 'I'he apparatus for putting the present invention into execution con- 15 sists essentially of an evaporator lof any desired number of tubes placed in any desired position.

The following working examples will serve to y make perfectly plain the preferred methods of putting the invention into execution. y 20 Fig.y 1 represents the main outlines of an apparatus according to the invention. A

Fig. 2 .represents the drawingoi? a lportion of "I .-the rate of feed; consisting of the vessel eand ia series of tubespg. A constant level is maintained in the vessele by any desired' means, for example the vessel may be constructed on Mari'- 40 ottes principle with the added peculiarity that the tube which dips into the vessel is connected through a flexible connection to the vacuum pip-'- ing so that a regulation of the level in vessel e may b e obtained by modifying the height of the 45 tube in the vessel. y

As soon as onecommences to heat the tubes g the liquid which is at a certain height begins to ascend'and the emulsion enters the evaporator, The vapour separates from the liquid in the vessel 50 i, and then passes through piping k and the refrigerator l to the receivers m where the hydrogen peroxide is collected. The residual liquid flows from the vessel i into the receiver o, connected to the vacuum system operating the whole plant. 55

` are three exits for the vapour.

In Fig. 2 the tube g destined to produce thev circulation of the liquid is shown joined to the evaporating tube by an elbow q, but the con'- necting tube q can equally well be straight, or again be so formed that tube q and h are in one piece, the vacuum being applied both at the inlet and outlet of this single tube. At the same time it is considered generally preferable that the two tubes, one for producing the circulation and the other for the distillation, should be separate, as i this increases the ease with which they can be maintained at diierent temperatures.

The present yinvention lends itself particularly well to distillation in which the vapour is eliminated at two or more separate points in the evaporator. This manner of working has the advantage of withdrawing the vapour formed away from the zone of heat, and out of Contact with the solution.

As a result of the desired pressure under which the apparatus is working being identical at all points and the speed of circulation of the solution being regulated by the heat applied, one always obtains a regular distillation with a high yield in the diierent steps of this operation.

In Fig. 3 an apparatus is shown in which there The liquid coming from the feed-tank b passes through a first heating tube and a first condenser, exactly as in the apparatus outlined in Fig. l. .After having passed out through the separating vessel i the vapour passes through the piping c to the refrigerator, while the liquor enters the second stage of the evaporation through piping n and a second heating tube g. This second stage of evaporation is then followed by a third or even further similar stages, each with a. similar lay-out. Finally after the last separating vessel the liquid is sent to the receiver connected to the vacuum piping.

It will `be seen that in all the above described embodiments the vacuum has absolutely no eifect upon the movement of the liquid by reason A of the fact that all of the vessels, for instance,

b, e, y, i, o and m are connected to the vacuum c. Accordingly the same absolute pressure exists inthe entirety .of the arrangement and no effect of pressure or lack of pressure can play any. part in order to cause a displacement of the liquid.

Thus the displacement of the liquid is produced by the sole effect of the temperature to which the tube g is subjected.

Having now particularly 4described and ascertained the nature of my -invention and in what manner the same is to be performed, I declare that what I claim is:

Process for the preparation of hydrogen peroxide by vacuum distillation of solutions containing active oxygen, which comprises passing the solution to be distilled from a. feed tank through ascending tubes' into a tubular evaporator, the ascending tubes being heated in such a manner-that a. continuous movement of the liquid to be distilled from the feed tank into the tubular evaporator is engendered solely by they action o! the heat diierence between the feed tank and the ascending tubes, all these parts, as well as the rest of the apparatus being throughout subjected to substantially the same degree of reduced pressure, th'e elements at the two ends or! the apparatus, namely, the receiver and the feed tank, being for this purpose connected separately and directly to the same vacuum system.

, JEAN MERCIER.

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