US2671010A - Sodium peroxide manufacture - Google Patents

Description

March 1954 L. J. GOVERNALE 2,671,010

SODIUM PEROXIDE MANUFACTURE Filed Nov. 29. 1951 INVENTOR. LUKE J. GOVER/VALE' Patented Mar. 2, 1954 q UNITED STATES PATENT orn-cc IS'DDIUM IQERBXIDE MANUFACTURE Luke J, .Governale, Baton Rouge, La., assignor to Ethyl Corporation, vNewYork, N. 1 a corp oration 'of Delaware .AplilicationzNovcmher 29, 19.51,-Ser.ialNo. 258;!)33

'i'fllaims. (Cl.'2 3184) ;1 The present invention relatesto the production of sodium peroxide, more particularly its formation from metallic sodium.

Sod-ium peroxide has heretofore been .made

by several different methods. .See for example I U. S. Patent Nos. 1,796,241 and 1,685,520. Such :methods have disadvantages in that they involve a two step procedure requiring :separate treat ment steps performed in difierent manners. .Such prior techniques require, for example, the stepwise and :batchwise processing of large charges, necessitating large and cumbersome equipment. Further, an oxidizing atmosphere having an oxygen content higher than that prosent-in' is r quired. The oxidation ofsodium by a spray burning method has been proposed, but the product so obtained .is not entirely satiso :factory for many purposes, being somewhat too light and flulfy for easy handling and dissolving.

Among the objects of the -,present*inventionvis the provision of novel methods and apparatus for producing sodium peroxide in which the above and related disadvantages are avoided- Additional o j s of the present invention in- %clude the provision oi novel. methodsiandiappav.ratus for oxidizing sodium to sodium peroxide wi hout equiring the treatment of iarge masses or sodium, and without producing explosive rmixtures or fumes. A still zfurther object of the present invention is the provision of novel methiods and apparatus :for rapidly oxidizing sodium :to sodium peroxide essentially :in runenriched .a'ir. An additional object is "to provide an eflicient continuous process for the manufacture of com merc'ially acceptable sodium peroxide.

The above as well as still further objects of the present invention-will be more completely understood from the following description :of :several of its exemplifications, reference :being made to the accompanying drawing wherein the :single :fi ure shows in schematic form :a sodium :peroxide forming apparatus in accordance with the present invention.

It has been discovered that very efiective oxidation of sodium directly to :sodium iperoxidecan be readily attained by providing :a ithin film of sodium deposited on a carrierrsurface, and contacting this film with an oxidizing atmosphere at an elevated reaction temperature until it is -substantially converted to sodium peroxide, then parting from the supporting metal surface as a :comminuted product. Inpref'erred forms olthe process, the oxidizing gas, which may he air or an enriched oxygen stream, "is forcibly directed against the sodium filmas a gaseou ,jet or a V .2 multiplicity of ,jets. Thus, for example, a one millimeter .film of sodium is converted to a predominantly sodium peroxide product in about '15 minutes. Atihig'her temperatures'the .rate of conversion is even higher. The product. obtained is in a .des'irable form, being in relatively homogeneous or dense particles, as contrasted with the light and .flufiy material derived 'by other continuous .methods.

The process is operable at'quite moderate temperatures, that is, at temperatures in the range of about 300 C. Although the benefits of the process are obtained to .an extent at such relatively moderate temperatures, the outstanding .benefit of a rapid reaction is greatly reduced. .1 13 has been found that the oxidation of the sodium in the manner described, when expressed in terms of conversion .to sodium peroxide at \dif feren't times, but at .a controlled temperature, apparently usually exhibits a ,period of rapid or primary reaction, and then-a period of relatively slow or secondary reaction. Thus, in carrying out the oxidation of a one millimeter film at about 360 the initial period appears to last .for about five minutes, and thereaiter additio al oxidation isso slow that approximately one hour is required to provide a product of 8 0 percent or more sodium peroxide .=oontent. When operating at 400 0., the initial period is slightly longer, or about seven minutes, and the subsequent secondary oxidation at a lower rate. When operatingatabout 450 Ccor higher, the socal ed secondary reaction period appears to disappear, or to :merge with the primary period, As a result, in the relatively brief period of about 15 minutes at 450 0., the reaction is complete, with no additional oxidation occur- .ring. .A product having approximately 90 percent sodium peroxide is produced.

At temperatures above 450 -C., the time re .quired .for oxidation is decreased still further, .50 thatthe capacity of a given plant :is increased. Satisfactory conversion is attained at temperatures of the order .of 6.00 C., but. for several reasons, the upper limit of the preferredoperating temperature range is about 575 C. -It has been found that above this temperature, the sodium peroxide tends to decompose more strongly than at lower temperatures, and that, therefore, it .is appreciably more dir'licult to ob? tain a product of acceptable purity. Further, the corrosive tendency ofsodiumperoxidegrea ly in-cr ase at temperatu es approaching 600 C which tends to limit the life of the equipment.

afiected to some extent by the thickness of the film of sodium being processed. Films thicker than one millimeter can also be used throughout the entire range at the cost of some increase in conversion time. However, when the sodium is deposited at a rate thicker than a one millimeter film, the overall degree of conversion is slightly reduced. The adverse effect of thickness is partially offset by the effect of the jets of air, which appear to penetrate through the initially oxidized surface to the full depth of the film. On the other hand, films thinner than one millimeter are rapidly converted. However, the effect of reduction of thickness below one millimeter is not as marked as the efi'ect of reducing the film thickness to one millimeter.

For practical operations it is advantageous that the process of the present invention be carried out in a continuous manner. By providing a carrier having an extended surface occupying an endless or looped path, and arranging for this surface to be continuously recycled around said path, the sodium can be continually applied at one portion of the path, followed by exposure of the sodium to air and the subsequent continual removal of the final oxidized product at a different portion of the path after which the surface is ready for another application.

The figure shows a convenient modification of an apparatus according to the present invention. A housing l carries within it a cylindrical drum l2 mounted for rotation around its cylindrical axis in the direction of the arrow l4. Above the drum there is positioned an applicator or distributor H; which may merely be in the form of anelongated pipe having a plurality of outlet nozzles I8 distributed along its lengths so as to extend across the axial length of drum l2. The applicator i fed by a source of molten sodium, shown as a container 20 which may be within or outside of the housing 10.

To avoid difficulties that may arise if the sodium solidifies in applicator l6, or container 2|), these structures may be provided with an external heating jacket through which hot liquid, such as oil, may be passed to heat them up or keep them from cooling suificiently to cause solidification. Such jacketing is conventional and in the interest of simplicity is not shown in the drawing.

The drum I2 is arranged to be held at the desired operating temperature, as by placing its interior in communication with an oil burner. This can be conveniently done by merely mounting an oil burner at one end of the cylinder and connecting a chimney or other vent to the other end. Although heat is liberated during the oxidation of the sodium, this heat is not sufiicient to keep the reaction mixture at temperatures as high as 450 C. for example.

Along the cylindrical periphery of drum 12 there is shown mounted a plurality of air nozzles 2|, 22, 23, 24 and 25, each connected to a suitable source of air such as a small blower, and each positioned to direct a stream of air against the external surface of drum 12 as this surface moves past applicator l6 and picks up sodium. It is advisable to use only dry air in the air nozzles, and for this purpose they can be connected to a source of fresh air by way of a drying unit to absorb substantially all moisture.

A scraper blade 30 is shown as engaging the external surface of drum [2 beyond the air nozzles to scrape off the reaction product 32, which product remains on the drum surface. A collecting trough 34 can conveniently be positioned below the scraper blade 30 to catch the removed product and if desired, automatically carry it out of the housing 10 continuously or in separate batches.

The apparatus can be operated by heating up the drum, introducing air through the air nozzles, and then starting th application of sodium. The sodium begins to oxidize as soon as it is exposed to the oxidizing atmosphere, but this factor, far from being disadvantageous, assists in retaining the film on the drum surface. This surface oxide film, being solid at operating temperatures, tends to prevent flow of the metallic sodium off of the drum and facilitates application. It is preferred to adjust the feed rate of the sodium by valve I! to provide a film of about one millimeter thickness or less. Inasmuch as the drum 12 can be arranged for operation at a substantially constant speed, the rate of application can also be fixed.

The housing In can be arranged to completely seal in the above units, except for a vent for the escape of xcess or reacted air. Since this excess gas, lean in oxygen content is very dry, it can be used in other applications where a dry atmosphere is needed. The escaping gas can also be filtered to catch particles of sodium or its oxidation products which may be picked up during passage through the housing In. By reason of the relatively high temperatures to which the escaping air is heated by th preferred type of operation, it can also be used to supply heat where desired.

Instead of having a cylindrical drum as shown in the figure, the sodium-carrying surface can be in the form of a flexible sheet metal belt which can be looped around one or more rollers to provide a corresponding cyclical travel around an endless path. In such a modification heating can be applied by way of the roller or rollers around which the band is looped, or the air blown against the metal surface can be preheated.

Alternatively the endlessly recycling sodiumcarrying member can be in the form of a fiat surface, such as that of a circular disc, and rotating around its center with sodium applied at one part of the rotation, the air exposure at a second part, followed by a scraper blade at a third part. This type of structure has th advantage of making possible the spreading of the reaction over substantially the entire recycling path of the sodium-carrying surface. This will be evident by noting that in the drum construction illustrated in the figure, about one-third of the drum periphery is not used for oxidation. The disc type of sodium holder can conveniently be heated by making the disc hollow and introducing heat to the hollow interior as in the manner described above in connection with the drum of the figure. If desired, heated air can also be used to heat the reaction mixture held on the discshaped carrier, or on the drum carrier of the figure.

Instead of blowing air into the housing, advantage can be taken of the natural draft that can be provided by the exhausting hot air. Thus by merely providing a sutiable chimney, the air blower can be eliminated.

As a further modification of the present invention, the number of air nozzles can be reduced or they can be completely eliminated and replaced by a single air inlet which can be simply provided at the wall of housing l0. Where one or more separate nozzles are used, one such nozzle can also be positioned to direct a stream of air somewhat enrichedwith oxygen against the sodium-carrying surface at a point just before the final product is removed. This is particularly suitable when the operation is carried out at temperatures below 450 C., inasmuch as a final contact of the oxidizing materials with an atmosphere containing more than 20 percent oxygen will greatly accelerate the completion of the oxidation, without requiring an excessive expense in the provision of an oxidizing atmosphere. It is advantageous in this form of the invention to provide an enclosing duct to keep the enriched air against the drum so that it does not dissipate too rapidly throughout the housing. The useful volume of enriched air can thereby be held down to substantially insignificant proportions.

The precise location of the scraper or doctor blade 39 is not critical. However, on the drum type reactor of the figure, it should be vertically positioned at or below the axis of the drum. This assures that the product as it is removed from the drum will fall clear and can be collected in a suitable receptacle or hopper 34. Location of the doctor blade in the region indicated will also provide the maximum practical reaction time for a given size drum. With the disc type sodium carrier, no special scraper location is needed. It is not essential that the doctor blade should scrape the drum surface entirely clear or free of the sodium peroxide product. In fact, it has been found desirable to allow a thin coating of the product to remain on the metal surface by a loose contact of the doctor blade. The effect of this recycled adherent coating is to minimize the corrosion of the metal drum and to assure a high purity product, that is, free of contaminants resulting from corrosion reactions.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope hereof, it is to be understood that the invention is not limited to the specific embodiments hereof, except as defined in the appended claims.

What is claimed is:

1. A method of producing sodium peroxide which method is characterized by pouring a film of liquid sodium not more than about one millimeter thick over the external surface of a rotatable carrier heated to between about 450 and 575 C., rotating said carrier through a stream of air directed against said heated film, the air being at a rate in excess of the quantity required for completely converting the sodium to sodium peroxide, for not more than about fifteen minutes 55 till the film is largely converted to sodium peroxide, and scraping off the resulting product.

2. The method as defined in claim 1 in which the carrier is rotated in succession through a plurality of streams of air.

3. A method of producing sodium peroxide comprising continuously depositing a thin film of sodium, having a thickness of not more than about one millimeter, on the exterior surface of an endless moving heat transmissive metal carrier, contacting a stream of air against said film at a rate in excess of the quantity necessary for completely converting the sodium to sodium peroxide, while heating the carrier to a temperature between about 450 and 575 C., continuing said contacting for not more than about 15 minutes until the sodium is largely converted to sodium eroxide, and then parting said peroxide from the said surface.

4. A method of producing sodium peroxide comprising depositing a film of sodium having a thickness of not more than about one millimeter on the exterior surface of an endless moving heat transmissive metal carrier, directing a plurality of jets of air against said film for a conversion time providing substantially complete conversion of the sodium to sodium peroxide while heating the carrier in an initial portion of not more than about 15 minutes of the conversion time to a temperature in the range of from above 450 to 575 C., and in the following portion to a temperature in the range of about 300 to 450 C., and parting the so-formed sodium peroxide from the said surface.

LUKE J. GOVERNALE.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Handbook of Chem. and Physics, 27th ed., 1943, pp. 462, 463. Published by Chem. Rubber Pub. 00., Cleveland, Ohio.

Claims (1)

1. A METHOD OF PRODUCING SODIUM PEROXIDE WHICH METHODS IS CHARACTERIZED BY POURING A FILM OF LIQUID SODIUM NOT MORE THAN ABOUT ONE MILLIMETER THICK OVER THE EXTERNAL SURFACE OF A ROTATABLE CARRIER HEATED TO BETWEEN ABOUT 450* AND 575* C., ROTATING SAID CARRIER THROUGH A STREAM OF AIR DIRECTED AGAINST SAID HEATED FILM, THE AIR BEING AT A RATE IN EXCESS OF THE QUANTITY REQUIRED FOR COMPLETELY CONVERTING THE SODIUM TO SODIUM PEROXIDE, FOR NOT MORE THAN ABOUT FIFTEEN MINUTES TILL THE FILM IS LARGELY CONVERTED TO SODIUM PEROXIDE, AND SCRAPING OFF THE RESULTING PRODUCT.

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