APPARATUS FOR PRODUCING ORGANOMETALLIC COMPOUNDS AND METHOD OF PREPARING ORGANOLITHIUM COMPOUNDS AID APPARATUS

The present invention relates to an apparatus and method for producing organometallic compounds. In particular, the present invention relates to the preparation of organometallic compounds by reacting alkali metals with alkyl halides or poly- nuclear compounds. The apparatus of the present invention is suit¬ able for the preparation of lithium alkyl compounds such as, for example, ethyllithium, isopropyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, hexyllithium or 1,5-dillithi- umpentane, and lithium-polynuclear compound addition complexes such as, for example, dilithium napthalene, dilithium stilbene, dilithium anthracene, and dilithium biphenyl.

Reactors are known in the art for the production of organometallic compounds by reacting alkali metals and alkyl halides or polynuclear compounds, which comprise a sealed vessel furnished with a jacket for maintaining the desired temperature conditions therein, provision being also made in the vessel for connections for feeding.the reactants into and discharging the reaction products from the reactor. The reactor vessel houses a shaft-mounted stirrer.

In said prior art reactors, the process of producing organometallic compounds involves the employment of alkali metal dispersions preliminarily prepared in special-type apparatus by melting an alkali metal and dispersing the resulting melt in a suitable neutral medium, e.g. paraffin.

The thus-obtained alkali metal dispersion in a disper¬ sing medium is thoroughly separated in the reactor from said dispersing medium and mixed with a hydrocarbon solvent, followed by batching an appropriate alkyl halide into the continuously stirred reactor. The heat evolved in the course of organometallic compound formation is withdrawn via the reactor walls by means of a heat transfer agent circulating in the reactor jacket.

On reaction completion, the reaction mixture is discharged from If - 1 - 4i& , .ÎW1 the apparatus and passed to product separation.

The procedure described hereinabove is followed, for example, in the process for producing organolithium compounds wherein finely divided lithium containing sodium or potassium additives taken in an amount of from 0 to 1% is reacted with an appropriate alkyl halide in a hydrocarbon solvent medium and under an inert gas blanket at a temperature of from 0° to 600C, followed by recovering the target product by conventional tech¬ niques .

However, the known reactor for the production of organo- metallic compounds necessitates the use of alkali metal disper¬ sions preliminarily prepared in a special apparatus. Such an alkali metal dispersion in the dispersion medium contains a significant proportion of inactive alkali metal, thereby making it difficult to avoid corrosive attack on the surface of finely divided alkali metal particles in the course of dispersion preparation, packaging, storing and batching. It will be noted that the finer the dispersion, the higher the percentage of the alkali metal that avoids conversion during organometallic compound synthesis.

Another disadvantage of said prior art apparatus is associated with pronounced losses experienced by the dispersion during the step of washing repeatedly the dispersion with a hydrocarbon solvent in order to remove the dispersing medium.

The known method of preparing organometallic compounds in said reactor is likewise disadvantageous in that it involves a prolonged induction period prior to the commencement of organo¬ metallic compound synthesis, said induction period being due to physico-chemical processes which make for the removal of corros- ion products from the surface of alkali metal particles. Said induction period hampers essentially the feasibility of reaction control and affects adversely process safety.

- se J»»*-* O S, .*?»*-, — — The product obtained in said reactor is contaminated with finely divided sludge which consists of an alkali metal salt and exceedingly fine particles of unconverted alkali metal. The latter impurity in the form of a fine suspension renders it difficult to effect product purification by conventional procedures, e.g. décantation, centrifuging or filtration.

Moreover, carrying out the process in said reactor is accompanied by an unwanted side reaction, viz., the Wurtz reaction whose rate depends on the alkyl halide concentration in the reaction mixture and also on the reaction temperature.

The present invention provides an apparatus for the production of organometallic compounds and a method for preparing organolithium compounds in said apparatus which make it possible to substantially reduce active alkali metal losses, to increase the yield of target products and enhance the purity thereof, and to minimize the duration of target product recovery.

According to the present invention there is provided an apparatus for the production of organometallic compounds by reacting alkali metals and alkyl halides or polynuclear compounds which comprises a sealed vessel, means for introducing reactants and means for withdrawing reaction products, means of maintaining the requisite temperature conditions, a stirring means, a press to extrude the alkali metal used through a spinneret so as to feed alkali metal strands into the apparatus, and a cutting means to comminute the alkali metal strands issuing from said spinneret, said stirring means being a dispersing means.

It is desirable that the cutting means for comminuting alkali metal strands be knives mounted on a rotatable shaft, the cutting edges of said knives being disposed in close vicinity to the exit side of said spinneret.

It is preferable to dispose the alkali metal extrusion press and the cutting means in the upper part of the apparatus, and the dispersing means in the bottom part thereof with a hollow cylinder placed in the free space therebetween to direct the circulating reaction mixture from the dispersing means to the cutting means.

In the hollow cylinder, the walls may be made hollow to provide for thermostatting medium circulation.

The hollow cylinder may further be provided with a convergent nozzle.

To provide for additional positive circulation of the reaction mixture in the reaction volume, the apparatus may contain a mixing vane, in which case it is desirable to mount a dividing disk between the mixing vane and the dispersing means.

The method of preparing organolithium compounds in the apparatus of the present invention comprises reacting metallic lithium and alkyl halides or polynuclear compounds in a hydro¬ carbon solvent medium and under an inert gas blanket at a temper¬ ature of from 0° to 600C, followed by separating the desired pro¬ duct wherein, according to the invention, the metallic lithium is comminuted and dispersed directly in the apparatus, in which there occurs simultaneously the aforesaid reaction of the metallic lithium with an alkyl halide or a polynuclear compound.

In carrying out the present method, the alkyl halide should preferably be introduced into the apparatus at a rate below that of alkyllithium formation.

When all of the alkyl halide has been introduced in the apparatus, it is preferable to heat the reaction mixture to a temperature of 60° to 1000C and maintain said temperature for a period of 1.5 to 2 hours.

The apparatus and method of the present invention make it possible to significantly enhance the efficiency of the process organometallic compound synthesis proper, to improve the yield and quality of target products with concomitant marked reduction of .lit alkali metal consiamption, to simplify the production cycle and also to facilitate working conditions, a further advantage being improved process safety.

The present invention is illustrated hereinbelow by the description of exemplary embodiments thereof with reference to the accompanying drawings, wherein:

Fig. 1 is a schematic cross-sectional view of the appa¬ ratus for producing organometallic compounds, according to the invention, and Fig. 2 presents an exemplary position of a cutting means for comminuting alkali metal strands in the apparatus, according to the invention.

The apparatus for producing organometallic compounds by reacting alkali metals with alkyl halides or polynuclear compounds comprises a sealed vessel 1 (Fig. 1) furnished with a cover 2 and a means for maintaining the requisite temperature in said apparatus, said means being a thermostatic jacket 3.

Affixed to the cover 2 is a toroidal deflector 4, which smoothly varies the direction of flow of the reaction mixture stream that circulates in the apparatus. The cover 2 also carries a press for extruding the alkali metal into the apparatus, said press comprising a plunger 6, a cylinder 7 with a chamber 8 for accomo¬ dating the alkali metal stock, and a spinneret 9, through which alkali metal strands are extruded into the apparatus.

Provision is also made in the apparatus for a cutting means which serves for comminuting the alkali metal strands 'issuing from the spinneret and consists of knives 11 mounted on a shaft 10 so that the cutting edges of said knives 11 are disposed in close vicinity to the exit side of the spinneret 9.

The shaft 10 also carries a stirring means, viz, a dispersing means 12.

The dispersing means 12 may be of any design, but the ftflf JlSfW' _ 5 - particular type of dispersing means is selected so as to meet the requirement of carrying out the process in the most efficient manner in a given reaction medium. Thus, the dispersing means shown in Fig. 1 is of a turbine type which is preferable where the synthesis of alkyllithium compounds in the present apparatus is conducted in a hydrocarbon solvent such as, for example, the 65- 1000C gasoline fraction.

A dispersing means comprising a toothed impeller and a similar stator is the preferred type for carrying out the synthe¬ sis of lithium-polynuclear compound addition complexes in a hydro¬ carbon solvent, e.g. toluene, or for producing alkyllithium compounds in a viscous neutral medium such as, for example, vaseline oil (this type of dispersing means is not shown in the drawings).

Knives 11 of the cutting means may be mounted on a shaft 13 (Fig. 2) actuated by an individual drive 14, thereby rendering it possible to select the optimum speed of rotation for both the shaft 13 with the knives 11 mounted thereon and the shaft 10, which carries the dispersing means 12 (Fig. 1).

The vessel 1 houses a cylindrical insert 15 with hollow walls for thermostatting medium passage therethrough. Said insert 15 directs the circulating reaction mixture from the dispersing means 12 to the knives 11, provided the knives 11 and the press 5 are located in the top part of the apparatus, while the dispersing means 12 is disposed in the bottom part thereof.

Heat transfer agent introduction into and discharge from the hollow walls of the insert 15 is effected via connections 16 and 17, respectively.

Where the apparatus is of significant length, it is desirable to mount on the shaft 10 a mixing vane 18 enclosed in a cylindrical guide 19 to impart additional positive circulation to the reaction mixture in the space of the vessel 1, in which case the preferred practice is to dispose between the mixing vane 0$ 18 and the dispersing means 12 a dividing disk 20, which separates the reaction fixture circulating stream produced by the raixing vane 18 and the dispersing means 12.

The apparatus cover 2 is furnished with connections 21 for reagent and hydrocarbon introduction, as well as with an inert gas inlet connection 22, whereas in the vessel 1 provision xs made for a connection 23, through which the reaction products are withdrawn.

Thermostatting medium feed into and discharge from the jacket 3 is effected via connections 24 and 25, respectively.

in the cylindrical insert 15, provision is made for a convergent nozzle 26. The nozzle 26 improves the conditions of stream circulation in the apparatus, as well as for eliminating stagnation zones. m some instances, the no22le 26 of .

rical insert 15 provides for preparing highly mobile dispersions in viscous neutral media.

To prepare organometallic compounds by reacting alkali metals with alkyl halides in the apparatus of the invention, recourse is had to the following procedure.

A hydrocarbon solvent is charged, via the connection 21, into the apparatus to a level somewhat below the upper edge of the cylindrical insert 15, followed by circulating the thermo¬ statting medium in the jacket 3 and through the hollow walls of the cylindrical insert, 15 via the connections 24, 25, 16 and 17.

The apparatus is then evacuated and filled, via the connection 22, with an inert gas.

The shaft 10 is then set in rotation. Once the requi¬ site temperature conditions (io- to 30<>C). are attained and main¬ tained in the apparatus, said temperature conditions favouring the process of dispersing mechanically the alkali metal used, there comnences feeding the alkali metal blanks, preferably ' cylinders or spheres of alkali metals, such as lithium, sodi.

Lum > - 7 - or potassium, via the chamber 8 into the press 5. m the press 5, the reciprocating plunger 6 forces the alkali metal through the spinneret 9, and the alkali metal strands issuing from the spinneret 9 into the apparatus undergo comminution by the knives 11, the resulting alkali metal particles being entrained with the circulating solvent stream into the volume of the vessel.

While passing repeatedly through the mixing vane 18 and the dispersing 12, the alkali metal particles undergo further commin¬ ution until a desired dispersion is obtained. For example, dispersing an alkali metal in a viscous neutral medium by means of a conventional impeller-type disperser yields an alkali metal dispersion in the form of flat flakes of 5 to 200 microns in diameter having ragged edges.

In this case the converging nozzle 26 in the cylindri¬ cal insert'.15 is instrumental in preserving pronounced fluidity of the alkali metal dispersion in viscous media even at concentra¬ tions as high as 15 to 20% by weight due to inert gas entrapment by and dispersing in the circulating medium in the course of operation of the dispersing means.

Where an alkali metal is dispersed in gasoline by means of the dispersing means 12 shown in Fig. 1, the alkali metal dispersed particles are nearly spherical in shape and have a diameter of up to 0.5-1.0 mm, and high mobility of the resulting system makes the employment of the nozzle 26 optional.

Once the requisite initial concentration of the alkali metal dispersion, e.g. lithium dispersion, has been attained in the reaction zone of the present apparatus, the temperature in the apparatus is maintained in the 0° to 60°C range and an alkyl halide such as, for example, butyl chloride, is introduced into the apparatus via the connection 21.

The alkyl halide is introduced in the reaction zone in the form of a 0-60% solution in a hydrocarbon solvent, said îmSl M**»** - 8 - 3.007832 solvent being the mediuxn in which the synthesis of the target alkyllithium is conducted.

Alkyllithium formation occurs immediately after alJcyl halide introduction and, hence, involves no induction period The alkyl halide is fed into the apparatus at a rate below that of alkyllithium formation, thereby reducing the consumption of the alkyl halide in the side reaction (Wurtz reaction) and increasing the target product yield. Reaction heat dissipation xs effected via the surface of the vessel 1 and of the cylindrical -0 ansert 15 by means of the circulating heat transfer agent. When all of the alkyl halide has been introduced, the reaction mixture xn the apparatus is maintained at a temperature of from 65° to 100oC for a period of 2 hours.

Heating the reaction mixture brings about aggregation of finely divided sludge particles and provides for completion of the reaction of the alkyl halide with the alkali metal. Further advantages inherent in the present method manifest themselves in that the procedure of sludge separation from the alkyllithium solution is essentially simplified and the target product is free from unconverted alkyl halide. it is to be noted that the presence of alkyl halide in the target product results in the formation of a fine, stable lithium chloride suspension.

On reaction completion, the reaction mass is discharg¬ ed from the apparatus via the connection 23 and directed to product recovery.

The method of producing alkyllithium compounds accord¬ ing to the present invention makes it possible to obtain pure products containing but a low percentage (under 1%) of inactive admixtures, the yield of the product being at least 90%.

The apparatus of the invention is useful for the prep¬ aration of alkyllithium compounds such as, for example, ethyl- lithium, isopropyllithium, n-butyllithium, sec-butyllithium, irw - 9 - tert-butyllithium hexyllithium or 1,5-dilithiimpentane, and lithiiom-polynuclear compound addition complexes such as, for example, dilithium naphthalene, dilithium stilbene, dilithium anthracene, and dilithium biphenyl.

Organometallic compound preparation by reacting alkali metals with polynuclear compounds is conducted as follows.

As in the case of alkyllithium compound synthesis, the apparatus is charged with a hydrocarbon solvent, via the connection 21, to a level somewhat below the upper edge of the cylindrical insert 15, followed by introducing into the apparatus, also via the connection 15, the calculated amount of a polynuclear compound such as, for example, naphthalene. Thermostatting medium inlet and outlet are effected through the connections 24, 25, 16 and 17.

With the shaft 10 set in rotation, the requisite temp¬ erature conditions (30° to 60°C) are established and maintained in the apparatus.

Alkali metal blanks are fed, via the chamber 8, into the press 5, whereupon the plunger 6 extrudes the alkali metal through the spinneret 9. The alkali metal strands issuing from the spinneret 9 are comminuted with the knives 11 and entrained into the volume of the vessel 1 with the circulating reaction mixture stream. The reaction of lithium with polynuclear comp¬ ounds to yield addition complexes, e.g. dilithium naphthalene, necessitates vigorous stirring. Process intensification is attained thanks to repeated passage of the reaction mixture through the mixing vane 18 and the dispersing means 12.

On reaction completion, the product is discharged from the apparatus via the connection 23, the yield of the target product being as high as 85%.

For a better understanding of the practice of the present invention by those skilled in the art, the following kW-*» _ examples illustrate specific embodiments of the method for producing organolithium compounds and the apparatus for accompli- shing the same.

Example 1 into an apparatus filled with argon is charged 26.5 1.

of hydrocarbon solvent (gasoline fraction boiling in the 65° to 100°C range), followed by introducing, via the press 5, and comminuting in the apparatus 550 g of metallic lithium (sodium content, 0.4%). The mixture is heated to a temperature of 40°c and to it is added over a period of 4 hours 3.8 1. of alkyl halide (n-butyl chloride) mixed with an equal volume of a hydrocarbon solvent (gasoline fraction boiling in the 65° to 100°C range), the reaction mixture being vigorously stirred by the dispersing means 12. After all of the n-butyl chloride has been added, the reaction mixture comprising a suspension of lithium chloride and unconverted metallic lithium particles in the solution of the n-butyllithium in hydrocarbon solvent, is maintained at a temperature of 70° to 75°C for 2 hours, followed by filtration to free the n-butyllithium solution from the lithium chloride and excess metallic lithium. The product, n-butyllithium solution, is a straw-yellow liquid containing 1.02 N of active lithium and 0.7% of inactive impurities. The yield of n-butyllithium equals 8 7% based on the n-butyl chloride.

Example, 2 Into an apparatus filled with argon is charged 25.5 1.

of hydrocarbon solvent (gasoline fraction boiling in the 65° to 100°C range), followed by introducing, via the press 5, and comminuting in the apparatus 630 g of metallic lithium. The mixture is heated to a temperature of 40°C and to is added over a period of 8.5 hours 4.25 1. of n-butyl chloride mixed with an equal volume of hydrocarbon solvent (gasoline fraction boiling in the 65° to 100°C range). After all of the n-butyl chloride 4« laùTsaz h- .aaea, the reaction mixtura (suspension) is mslil>tainea •t a temperature of 70- to 75-0 for a hours a„a thereafter fUt- ere, to free the n-butyllithium .olnl!loB from ana eoess taXX.o llthtl.. Iha ..

tron i. a straw-yeUow liguia contain, 1.ln ot aotiva ana 0.3, of inactive impurities, the yiela of n-butyllithiu„ being 89% baSea on the „-butyl ohioria..

Example 3 into an apparatus filiea with argon is chargea 31 9 1 =f hyarocarhon solvent «gasoline fraction hoiiing in the „.' " 100»c range,, followea by introaucing, via the press 5, ana commuting i„ the apparatua „„ g of i-t|aiio iithi_ Mixture is heatea to a temperature of 40"c ana to it is aaaea over a perioa of 3.5 hours l.as 1. of sec-hutyl chioriae mix8a wrth an egual volume of hyarocarhon sdvent <gasoli„. fraotion borling in the 65= to 100-0 range, , the reaction ture heing vigorously stirrea by the aispersing means 12. After all of the sec-butyl chloriae has been aaaea, the reaction mixture «suspension, is maintainea at a temperature of ec for 2 hours ana thereafter fiiterea to free the sec-butyllithi™ solution from the irth.um chloriae ana excess metallic lithium. Xhe proauct sec-butyilithium soiution, is a coiourless liguia containing 0.401N of active lithium and 0 42% um ana 0.42% of inactive impurities. The yield of sec-butyllithium is 79% based on + cased on the sec-butyl chloride.

Example 4 into an apparatus filiea „ith argon are ohargea 33 of toluene ana , kg. of „aphthale„e, followea by introaucing, ' the press 5, ana comminuting in the apparatU3 so0 g irthium. The mixture is heatea to a temperature of 30-0 ana maintainea at this temperature for a perioa of 10 hours, while being vigorously stirrea by the aispersing means 12. on reaction completion, the reaction proauct in the form of a violet suspension '.&,*=£ - 12 - S wmmz is discharged from the apparatus, the yield of dilithium naph¬ thalene being 85% based on the naphthalene.

Example Into an apparatus filled with argon is charged 26.1. of vaseline oil, followed by introducing, via the press 5, and comminuting in the apparatus 500 g of metallic lithium. The mixture is heated to a temperature of 42°C and to is added over a period of 3.5 hours 3.5 1. of n-butyl chloride mixed with an equal volume of vaseline oil, the reaction mixture being vigorously stirred by the dispersing means 12. After all of the n-butyl chloride has been added, the reaction product in the form of a suspension is maintained at a temperature of 70° to 750c for 2 hours, allowed to settle during 16 hours and filtered to free the n-butyllithium solution from the remaining unconverted lithium. The product, n-butyllithium solution is a viscous yellow liquid containing 1.04N of active lithium and 0.58% of inactive impurities. The yield of n-butyllithium is 77% based on the n- butylchloride.

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