US2918435A

US2918435A - Preparation of alkali metal dispersions

Info

Publication number: US2918435A
Application number: US478618A
Authority: US
Inventors: Paul F Warner
Original assignee: Phillips Petroleum Co
Current assignee: Phillips Petroleum Co
Priority date: 1954-12-30
Filing date: 1954-12-30
Publication date: 1959-12-22
Anticipated expiration: 1976-12-22

Description

Dec. 22, 1959 P. F. WARNER PREPARATION oF ALKALI METAL DISPERsIoNs Filed nec. 30, 1954 INVENTOR.

PAUL F. WARNER i] hl A United States Pate-at- PREPARATIoN F ALKALI METAL nIsPERsIoNs Paul F. Warner, Phillips, Tex., assignor to Phillips Petroleum Company, a corporation of Delaware This invention relates to the dispersion of alkali metals.

in a dispersing medium.

D ispersions of alkali metals, particularly sodium, have been known and used for many years. Such dispersions are -used as catalysts` for many organic reactions, e.g. the production of liquid polybutadiene, metalation reactions, lrefining of petroleum fractions etc. Several batch methods are given in the art for the preparation of sodium dispersions. These batch methods work well enough when the sodium dispersion is employed in small scale batch reactions andl are used immediately after preparation. Sodium dispersions are dangerous to handle and it is desirable to have on hand at any given time only very limited quantities of sodium in the dispersed state. Furthermore, it is extremely diiicult to pump andto meter-sodium dispersions. With the development of large scale processes, and particularly continuous proc-- esses, wherein sodium dispersions are employed it has becomey highly desirable to be. able to prepare these ydispersions in a continuousmanner.'

I have devised a method and apparatus for continuously preparing a dispersion of an alkali metal in an inert liquid by means of which the above mentioned` diiculties are overcome or at least mitigated. Broadly speaking, my invention comprises continuously passing molten alkali metal and dispersing medium in'metered amounts through a dispersing. zone and concomitantly dispersing said metal insaid medium.

An object of this invention is to provide a method for preparing a dispersion `of alkali metal in a dispersing medium.

Another object of this invention is to provide a method for continuously preparing a dispersion of alkali metal in'` a dispersing medium and feeding said dispersionto a reaction zone as it is formed.

Another object of this invention is to avoid the use of pumps and meters in -handling dispersions of alkali metals in a dispersing medium.

Another object of thisinvention is to avoid the necessity for storing large quantities of alkali metal in they dispersedl state.

Still another object of this invention is to provide apparatus for carrying out the aforesaid objects.

Other objects-and advantages of the invention-will be apparent to those skilled in the art upon reading this disclosure and the attached drawing.

According to the invention there is provided a method for the preparation of dispersions of alkali metal in an inert liquid which comprises: continuously displacing molten alkali metal from anv alkali metal melting zone, with a metered stream of displacing medium, into and through a dispersing zone; simultaneously and continuously-passing an inert liquid in a metered amount into and through said dispersing zone; and concomitantly duringl said passage dispersing said molten metal in said inert liquid.

Further according to theinvention there is provided a combination kof vapparatus for carrying out. the method`V of the invention.

It is to be noted that the dispersion is prepared ina continuous manner. By thus continuously preparing the dispersion, as needed, the necessity for preparing in advance and storing large quantities of alkali metaly in the dispersed state, to be used duringthe course of a reaction, is avoided, My invention makes it possible to prepare the dispersionsras needed and pass same di-v rectly to the reaction zone. This feature of the invention is a definite advantage from a safety standpoint as will beV recognized by those skilled in the art.

It is also to be noted that the molten alkali metal isv displaced, with a metered stream of displacing medium, into and through the dispersing zone. Thus the necessity for a pump capable of handling the molten or dispersed alkali metal is avoided. Furthermore all-metered streams are free of dispersed metal, either in themoltenv or solid state, and can be pumped and metered without difculty.

A further advantage of my continuous method is that any possibility of agglomeration of the dispersed metal is avoided. Suchragglomeration sometimes occurs when the dispersion is prepared batchwise and allowed to stand until used. l

The term alkali metals as employed hereinv and in the claims includes the metals sodium, potassium, lithium, rubidium and caesium, and also alloys of two or more such metals with each other, for example, potassium-v sodium alloys. n

Inert liquids are suitable dispersing mediums. The term inert liquid includes any organic liquid that is inert to thealkali metal'and has a boiling point above the melting point of the metal to be dispersed therein under the conditions rof use. Examples of suitable lquids are xylene, toluene, isooctane, heptane, various pe-l troleum fractions such as light naphtha, Stoddard solvent,

refined kerosene etc.

The attached drawing illustrates diagrammatically one combination of apparatus which can be employed to prepare dispersions of alkali metals according to the invention.

Referring now to the drawing the invention willv be more fully explained. Reference numeral 10 denotes a vesselvcontaining an oil bath which is maintained at a desired temperature by circulating the oil through an externalnheaterll` by means of line 12 and pump 13. Other means suchas immersed electrical heaters can be employed to heat said oil bath. Mounted within and extending through the topL 16 of vessel 10 as shown are two melt tanks 14 and 15. Also mounted within and extending through the top 16 of vessel 10 and positioned between said melt tanks isl a dispersing chamber 17. In some instances it is desirable to mount dispersion chamber v17 outside oil bath 10 and thus be able to control the temperature of chamberV 17 independently of oil bath lll. Also means other than an oil bath, such as hot gases, electrical resistance heaters etc. can be employed to heat saidmelt tanks and` said dispersion cham.

ber.

A first conduit `18v having a valve 19 therein connects the bottom of melt tank 14 with the lower portion of chamber 17. A second `conduit 20 having a valve 21 therein connects the bottom of melt tank 15V with the v Lines 28 and -29 can .be connected to tank 30. Dis-- Patented Dec. 2 2, 1959 placing medium inlet lines 31 and 32 are connected to

inlet conduits

24 and 25 respectively at points below

valves

26 and 27. Extending downwardly through cover plate 22 of melt tank 14 are probes 57 and 58 which comprise a high level and low level indicating system. Said probes are connected through the lead wires shown to a suitable relay system (not shown) which operates a suitable warning `or indicating device such as a light or bell (not shown).

Dispersing chamber 17 is closed with a removable anged cover 33. Mounted on the bottom of cover 33 so as to be positioned in the upper portion of chamber 17 is a gear pump 34 having a suction line 35 extending into therlower portion of chamber 17. Pump 34 is driven by motor 36 mounted on top of cover 33 and operatively connected tosaid pump by a shaft extending through a suitable packing gland or mechanical seal 37. Pump 34 discharges through nozzle 38 against target plate 39. If desired said target plate can be omitted and the pump discharge directed, from a suitable distance away, against the wall of chamber 17. The invention is not limited to employing a gear pump in chamber 17 as just described. Any suitable dispersing means capable of effecting the desired degreeof dispersion can be employed in chamber 17 High speed stirring or agitating means can sometimes be employed. One high speed stirring head which can be employed in some instances is the Dispersator, commercially available in several sizes from Premier Mill Corp., Geneva, N.Y.

In operation for the preparation of a dispersion of an alkali metal in an inert liquid,` for example, sodium in xylene, the system from tank 46 through dispersion chamber 17 and line 51 is lled with xylene toremove oxygen. Conduits 18 and 20 can be purged by opening valves 19 and 21 and permitting a small amount of xylene to ow into melt tanks 14 and 15. If desired the system can be purged with nitrogen admitted through line 40, passed through chamber 17, conduits 18 and 2t) and a nitrogen atmosphere maintained in melt tanks 14 and 15 as they are being initially charged with sodium.

The oil bathis brought to operating temperature of approximately 240 F. and the melt tanks 14 and 15 are charged with metallic sodium which soon melts sufciently to form a liquid seal over the entrance to conduits 18 and 20.` Displacing medium, generally a light oil such as refined kerosene, is then pumped from tank 30 through line 42, pump 43, lines 44, 31 and 32 into melt tanks 14 and 15 to ll said tanks and purge said lines and pump 43. After the sodium has melted

valves

26 and 45 are closed. Displacing medium is pumped from tank 30 vialine 42, pump 43, line 44, valve 50 and line 31 into melt tank 14 to displace molten sodium therefrom via conduit 18 and valve 19 into dispersion chamber 17. Simultaneously with the start, and continuously during the ow of displacing medium into melt tank `14, xylene is passed from tank 46 `via line 47, pump 48 and line 49 directly intodispersing chamber 17. `Upon starting ilow of molten sodium and xylene into chamber 17, pump 34 is started and picks up a mixture of said two liquids through line 35 and discharges same through nozzle 38 against target plate 39, shattering the sodium and dispersing it in the xylene. Upon continued introduction of the sodium and xylene into chamber 17 the dispersion ofsodium in xylene is displaced by the two said entering streams into line 51 and is passed to the reaction zone where it is to be employed. When substantially all the sodium has been displaced from melt tank 14, as indicated by'probe 58, valve 27 is closed, valves 21 and 45 are opened, whereupon displacing medium is admitted into melt tank 15. Valves 50 and 19 are then closed and molten sodium is displaced from melt tank into and through dispersing chamber 17 as described in connection with rnelt tank 14. Simultaneously during displacement' of molten sodium from melt tanks `14 and 15the ow of xylene into` and through dispersion chamber 17 is continued, pump 34 is running and thus there is obtained concomitant dispersion of said molten sodium in said xylene during passage of said liquids through chamber 17.

When displacing medium is started into melt tank 15 a new charge of sodium is placed in melt tank 14 by opening valve 26. Melt tank 14 is full of displacing medium which overows through line 28. When melt tank 15 is substantially empty, as indicated by probe 60, the displacing medium is switched back to melt tank 14 in a manner similar to that described and melt tank 15 is recharged. The system is now on continuous operation. Thus, there is obtained, alternate ,melting of metallic sodium in, and alternate displacing of molten sodium from, a rst section and a second section of a sodium melting zone so as to continuously pass molten sodium from said melting zone into and through a dispersing zone;

During the above operations pressureindicating gages 52, 53 and 54 register the pressure in melt tank 14, melt tank 15 and dispersion chamber 17 respectively. Safety release valves 55 and 56 are provided to release displacing medium into

overllow lines

28 and 29 respectively if the pressure in melt tanks 14 or 15 becomes too high. Pressure indicating controller 61 and motor valve 62 can be employed to hold a desired back pressure on the system. p

Pumps

43 and 48 are meteringpumps and are shown as drivenby a common drive 57 powered from a source not shown. Separate drive can be used. Said pumps are set to deliver each liquid at a predetermined tixed rate relative to the weightof sodium it is desired to disperse in a given weight of xylene. For example, if it is desired to prepare an alkali metal dispersion containing 25 percent metal by weight, pump 43 is set to deliver 25 parts by weight to every 75 parts by weight delivered by pump 48. VMetering and proportioning pumps of this typecan be obtained commercially. Other types of pumps and meteringsystems can be employed. It is a feature of the invention that by` performing the pumpingand metering operations on the inert liquid and the displacing medium, increased flexibility in the choice of p pumps is obtained. The only requirement is that the pumps chosen have suflicient head to move the liquids through the system and the resulting dispersion `into the reaction chamber where the dispersion is to be employed.

The following example further illustrates theinvention.

Example f The system was prepared for operation as described above. After the metallic sodium had melted in the melt tanks, displacing medium was started into melt tank 14. Simultaneously, xylene was started into the dispersion chamber and pump 34 in said chamber was started. Operating conditions were as follows:

Feed composition:

k Sodium 25 partsby weight. Xylene 75 parts by weight. O1l bath temperature 240 F. (approx.).`

Nozzle to target distance ).12 inch (approx.). Velocity of liquid through nozzle 210 to 240 ft./sec. Residence time in dispersion chamber, average 1.4 to 1.8 hours. Circulation rate in dispersion chamber 1.7 gaL/min. (approx.).

. switched to melt tank 15 and a fresh charge of sodium was melted in melt tank 14 as described.` Alternate melting of metallic sodium in,` and alternate displacing of molten sodium from, melt tanks 14 and 15 was continued during the length of the run. The first dispersion product was low in sodium content due to the dispersion chamber being full of Xylene at the start of the run. This could have been compensated for by charging the sodium at a higher initial rate. After the system was lined out a sodium dispersion having a composition of 25 percent by weight sodium and 75 percent by weight xylene and an average particle size of 5-10 microns was obtained.

Repeated runs, employing substantially the apparatus and modus operandi described above, have demonstrated that sodium dispersions having a sodium concentration up to at least 50 percent by weight, and an average particle size of at least 5-10 microns, can be prepared continuously and regularly without diiiiculty.

`If desired dispersion aids and dispersion stabilizers can be employed by injecting them into the inert liquid prior to dispersing the metal therein. However, it is a feature of the invention that inasmuch as the dispersion can be prepared as needed and used immediately, the need for dispersion stabilizers is greatly reduced or eliminated.

Operating conditions of temperature and pressure will depend upon the melting point of the metal being dispersed and the boiling point of the inert liquid in which the metal is being dispersed. Generally the temperature will be in the range of 20 to 40 F. above the melting point of the metal.

The pressure will depend to some extent upon the process in which the dispersion is being used. It is preferred to operate the dispersing system at a pressure higher than that at which the process wherein the dispersion is used is carried out. The pressure must be high enough to maintain the inert liquid in liquid phase at the conditions of operation of the dispersing system. The choice of proper operating temperatures and pressures will be readily understood by those skilled in the art yin view of this disclosure.

-Materials of construction generally can be selected from those available commercially. Mild steel can be used in most instances. Gasketing and packing materials should be inert to sodium. Halogenated materials should not be used.

Caution should be exercised in Working with and preparing alkali metal dispersions. All equipment should be clean and dry. Since these dispersions sometimes ignite on exposure toair such exposure should be avoided. Removal of theinert liquid as by evaporation or by capillary action on contact with textile materials, such as clothing, leaves a residue of finely divided metal which may ignite spontaneously.

As will be evident to those skilled in the art, various modifications of the invention can be made, or followed, in the light of the above disclosure and the appended claims, without departing from the spirit or scope of said disclosure and said claims.

l claim:

1. A method for the preparation of a dispersion of an alkali metal in an inert organic dispersing medium which is inert to and has a boiling point higher than the melting point of said alkali metal, which method comprises, in combination,` the steps of: continuously displacing a measured amount of a molten alkali metal from an alkali metal melting zone with a like measured amount of a stream of light oil displacing medium directly into and through a dispersing zone; simultaneously and continuously passing a measured amount of said dispersing medium in a separate stream directly into and through said dispersing zone; and concomitantly, during passage of said streams through said dispersing zone, dispersing said molten metal in said dispersing medium.

2. A method according to claim 1 wherein said alkali metal is sodium.

3. A method according to claim 1 wherein said alkali metal is potassium.

4. A method according to claim 1 wherein said alkali metal is rubidium.

5. A method according to claim 1 wherein said alkali metal is lithium.

6. A method according to claim 1 wherein said alkali metal caesum.

7. A method for the preparation of alkali metal dispersions in an inert organic dispersing medium which is inert to and has a boiling point higher than the melting point of said alkali metal, which comprises, in combination, the steps of: continuously pumping a stream of oil at a predetermined fixed rate into an alkali metal melting zone so as to continuously displace a corresponding n amount of molten alkali metal directly into and through a dispersing zone; simultaneously and continuously pumping, at a predetermined fixed rate, a separate stream of said dispersing medium directly into and through said dispersing zone, each of said predetermined fixed rates being determined by the weight of said metal to be dispersed in said dispensing medium; and concomitantly dispersing said molten alkali metal in said dispersing medium during said passage of said streams through said dispersing zone to form a dispersion of said metal in said medium.

8. A method for the preparation of a sodium metal dispersion in xylene, which method comprises, in combination, the steps of: alternately melting metallic sodium in, and alternately displacing metallic sodium from, a first sodium melting zone and a second sodium melting zone so as to continuously pass a stream of molten sodium from at least'one of said melting zones directly into and through a dispersing zone, said molten sodium being displaced from said melting zones in a measured amount by passing a like measured amount of a light oil displacing medium into said melting zones; simultaneously and continuously passing a measured amount of said Xylene directly into and through said dispersing zone; concomitantly, during passage of said streams through said dispersing zone, dispersing said molten sodium in said Xylene to form a dispersion; and passing said dispersion directly to a reaction zone.

References Cited in the le of this patent UNITED STATES PATENTS 2,021,143 Calcott et al. Nov. 19, 1935 2,409,519 Tanner Oct. 15, 1946 2,487,333 Hansley Nov. 8 ,1949 2,487,334 Hansley Nov. 8, 1949 2,612,354 Dron Sept. 3, 1952 2,685,437 OKeefe Aug. 3, 1954

Claims

1. A METHOD FOR THE PREPARATION OF A DISPERSION OF AN ALKALI METAL IN AN INERT ORGANIC DISPERSING MEDIUM WHICH IS INERT TO AND HAS A BOILING POINT HIGHER THAN THE MELTING POINT OF SAID ALKALI METAL, WHICH METHOD COMPRISES, IN COMBINATION, THE STEPS OF: CONTINUOUSLY DISPLACING A MEASURED AMOUNT OF A MOLTEN ALKALI METAL FROM AN ALKALI METAL MELTING ZONE WITH A LIKE MEASURED AMOUNT OF A STREAM OF LIGHT OIL DISPLACING MEDIUM DIRECTLY INTO AND THROUGH A DISPERSING ZONE; SIMULTANEOUSLY AND CONTINUOUSLY PASSING A MEASURED AMOUNT OF SAID DISPERSING MEDIUM IN A SEPARATE STREAM DIRECTLY INTO AND THROUGH SAID DISPERSING ZONE; AND CONCOMITANTLY, DURING PASSAGE OF SAID STREAMS THROUGH SAID DISPERSING ZONE, DISPERSING SAID MOLTEN METAL IN SAID DISPERSING MEDIUM.