US2859231A - Manufacture of alkyllead compounds - Google Patents

Description

Patented Nov. 4,1958

United States" Patent OfiFice MANUFACTURE OF ALKYLLEAD COMPOUNDS Sidney M. Blitzer and Tillmon H. Pearson, Baton Rouge, La., assignors to Ethyl Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application December 29, 1955 Serial No. 556,051

Claims. (Cl. 260-437) This invention relates to a process for the manufacture of tetrahydrocarbon lead compounds. More particularly, the invention is directed to a new and novel process for the manufacture of tetraalkyllead compounds, of which tetraethyllead is the most important.

The processes heretofore employed on a substantial scale are best illustrated by reference to the production of tetraethyllead. This material is in wide usage as an antiknock agent in the operation of internal combustion engines. The commercial process has generally been highly successful, but has certain inherent disadvantages not heretofore circumvented. The commercial process proceeds by reacting a sodium lead alloy, of composition controlled to correspond substantially to NaPb, with ethyl chloride according to the following equation:

With the highest yields obtained thereby, only some percent of the lead present in the NaPb alloy is converted to tetraethyllead. This conversion of lead to tetraethyllead has not been materially changed in many years, apparently because of an inherent'lirnitation corresponding to the above equation. In this reaction, then, at least 75 percent of the lead originally employed is not alkylated. Large quantities of lead must then be recovered and reprocessed to NaPb alloy in order to make it economical. A further disadvantage of such a large quantity of unreacted lead is that valuable reaction space in the reactor is occupied by materials which are essentially inert for the manufacture of tetraethyllead under present conditions and mode of operation.

Other reaction processes for the production of hydrocarbonlead compounds, especially tetraethyllead, have been devised to consume the lead produced in the above While such processes aresatisfactory from equation. the standpoint of lead consumption, they suffer an additional drawback in common with the present commercial process in that they require organo halide as the ethylating agent. One such process is that described in U. S. Patent 2,535,190 wherein lead, as for example that produced in the commercial process, is treated with metallic magnesium and ethyl chloride in the presence of a catalyst, preferably an alkyl ether. Thus, in this process as well as the above mentioned alloyrocess, the tetraethyllead manufacturing operation is restricted by the necessary balance between the metallic sodium required and the organic chlorine in the ethyl chloride. A classical method for the manufacture of tetraethyllead which likewise requires strict balance between metallic magnesium and organic halide, and has the additional drawback of requiring highly hazardous ether, is the reaction of the so-called Grignard reagent, for instance ethyl magnesium chloride, with lead chloride. I

It is an object of the present invention to provide a new reaction process for manufacturing the tetrahydrocarbonlead compounds, the process overcoming the prior dilficulties and providing other unanticipated benefits. More particularly, an object of the invention is to provide a process which realizes a conversion of lead to tetraethyllead in greater proportions than heretofore provided. Even more specific an object is to provide a process which does not require the use of metallic sodium or other alkali metal. In addition, an object is to provide a process which does not require the use of metallic lead or organic chlorides. A still further object especially of preferred embodiments, is to provide a new reaction process wherein certain lead compounds are reacted with alkyl compounds of active metals.

The foregoing and other objects are attained by the process of'reacting a lead organo acidsalt and a nonlead alkylmetal compound as an alkylating agent. substantial number of lead salts as well as of non-lead alkylmetal compounds stable under reaction conditions, are employable, as is illustrated hereafter.

The organic lead salts employed in conducting this invention comprise lead compounds wherein lead is attached to at least one carbon-containing organic radical through an intermediate atom of oxygen or sulfur, that is, a chalkogen. Lead salts of recognized organo acids not having a carboxylic acid grouping, but having strongly acidic hydrogen, are efiective in this process. Thus, the lead salts employed in this invention comprise lead carboxylates, lead thiocarboxylates, lead phenates and lead thiophenates. of such leadsalts comprise alkanoic, cycloalkanoic, carboxyaromatic and phenolic radicals. In a preferred embodiment of this invention a group III-A metal alkylating agent is reacted with a neutral lead salt of an aliphatic carboxylic acid having from one to about 21 carbon atoms in the aliphatic radical. The lead salt employed will be dictated by a number of factors, primarily economics, inasmuch as they all appear to be.

quite effective in the reaction. The preferred lead compounds are lead salts of low molecular weight carboxylic acids, especially the lead acetates. Another class of organic lead salts particularly suitable in this invention comprise the lead salts of the so-called naphthenic acids having from six to about twenty-five carbon atoms in each organic radical. Additionally, the organic portion of the lead salt can contain other elements besides carbon and hydrogen, in particular oxygen. In those embodiments employing aromatic lead salts, the aromatic radicals can be substituted with other elements including oxygen, nitrogen, sulfur, providing that the substituent is not effective in degrading the metal alkyl reagent.

The alkylmetal reactants used in the process are chosen in accordance with the desired tetrahydrocarbonlead product and may be selected from a large number of materials of high but varying effectiveness. The alkylmetal compounds suitably used are preferably derivatives of a metal having an electrode potential of more than 0.3 volt, including for example group I-A metals such as lithium and sodium, group II metals such as beryllium, magnesium, zinc and cadmium, and group III-A metals such as boron and the aluminumtype metals. The fully alkylsubstituted compounds of polyvalent metals are preferred, but alkyl compounds of monovalent active metals, and the partially alkylated derivatives of the polyvalent metals are also suitable.

A particular feature of the process of the invention is the employment of lead organo acid salts to produce tetrahydrocarbon lead, or more particularly, tetraalkyllead products. Such materials have not been heretofore produced from lead organo acid salts. A further unexpected advantage of preferred embodiments of the process of the present invention is the transfer of all the alkyl groups of certain polyalkylmetal alkylating agents reacted, into the tetraalkylead product.

In general, the organic portion like.

In preferred "embodiments of this invention alkylating compounds having fromone to about eight carbon atoms-- in each alkyl group are reacted with lead salts of aliphatic acids. One such class of lead salts are the lead alkapoates havingone -to 2l carbon atoms in- -e ach-acidic radical:

Illustrativeof suchlead salts-are 'leadacetate, lead sub acetate; lead-tetraacetate, lead -butyrate;-lead-formate;' lead oxalate, lead laurate, lead stearate; lead palmitate;- lead linoleate, -lead propionate; mixtures thereof and -the Typicaiof thelead organo acid; salts -wherein the leadatornis attached to the organic radical through sul j fur are leadthioacetata-and lead thioformate.

the aromatic lead salts which can be employed, typical examples-include lead phenate, lead thiophenate, lead" pounds ofaluminum type metals, VlZ., aluminum, gal-- lium; and indium in grOup III-A of the periodic table, the" alkylaluminum reactants being particularly preferred; 1

From this groumpreferredembodimentsinclude the trialkylaluminum compounds havinga total of 3 to 24 carhon-atoms in the alkyl radicals, the alkyl radicals being norm-al'or branched chain groups. Among the group IIIA-metalalkyl-compounds Which can be reacted'with the lea'd organo-acid s'alts are trimethylaluminum, triethylaluminum,-methyldiethylaluminum, tripropylaluminum,

dir'nethylhexylalurninum, methylethyloctylaluminum, tn-

isooctylaluniinum; diethylaluminum hydride, methylalu minum 1 dihydride'; triisobutylaluminum diisobutylaluminum hydride; octylaluminumflihydride, sodium aluminum tetraethyl, lithiuin--aluminumtetraethyl, potassium aluminum triethyl hydride;sodium aluminum tetrabutyl, potassiumalum-inum dioctyl dihydride, dimethylaluminum chloride, -ethylaluminum dichloride, ethylaluminum sesquichloride, trimethylgallium; triethylgallium, methyldiethylgallium, tripropylgallium, dimethylhexylgalliurn, methylethyloctylgallium; trioctylgallium, dipropylgallium hydride, methylgallium dihydride, triisobutylgallium, diisobutylgallium hydride, sodium gallium tetraethyl, lithium gallium tetraethyl, potassium gallium triethyl hydride, sodium gallium tetrabutyl, caesium gallium dioetyl dihydride, dimethylgallium chloride, ethylgallium sesquichloride, trimethylindium; triethylindium, methyldiethyl:

indium,-'tripropylindium, dimethylhexylindium, methylethyloctylindium, trioctylindium, dirnethylindium hydride, methylindium -dihydride; ;triisobutylindium, diisobutylindium vhydride, sodium'indium tetraethyl, lithium indium tetraethyl, potassium-indium triethylhydride, sodium indium tetrabutyl,-potassium indiurn'dioctyl' dihydride, dimethylindium chloride, ethyl-indium sesquichlm ride, and the like.-

A further highly effective class of alkylating reactants for the process are the alkylzinc compoundsya's well "as certain other alkylcompounds of divalent-metals; Both 1 monoand dialkylderivatives are suitable, but the most efiicient process employsa dialkylzinc-compound,-eachalkyl group having, preferably, at-least-oneand; u'p-to Also among-the suitable alkylating eight carbon atoms.

agents are the alkyl-zinc hydrides, alkylrzinc halides; and

mixtures thereof. Further, the alkyl zinc=may be in the form of a bimetallic complex, such as=s0dium:..zinc tri-- ethyl, potassium zinc methyldiethyl. and .the'likec AIR-1;,

other efiective class of reactants arecertain reaction prod-:1

nets of active metals andalkyl esters 'of polybasic,.acids:;: The alkyl zinc reagents employedin reacting ,withthe lead:organoacid salt further include the-identically ,di.;

alkyl substituted compounds, suchas,diisopropylzinc,-;di-

ethylzinc, dimethylzinc, I dibutylzinc, :diamylzinc dihexylt;

zinc, dioctylzinc, or in the case of compounds with alkyl groups of fouror'more'carbon atoms, the diisoalkyl compounds, or the ditertiary alkyl compounds. The dialkylzincs having dissimilar alkyl substituents are frequently desirably employed such as methylethylzinc, ethyl-npropyl zinc, isopropyl-n-butylzinc, isobutyl-3,3-dimethylbutylzinc, n-heptyl-n-octyl zinc and others, However, the proeess is not: confined to the dihydrocarbon zinc com pounds, it having been discovered that monoalkylzinc compeundsare highly eflfectivet; Illustrative examples of such monoalkyl substituted zinc compounds are ethylzinc bromide, ethylzinc chloride, ethylzinc iodide, n-butylzinc bromide and the-lil e. Itgisnot essential that the organozinc compoundbe 1a purified andvisolated zinc compound, but, in certain instances, reaction, product mix tures having uncertain amounts'of alkylzinc bonds are employable as reagents. For example, it has been'recently discovered that metallic zinc can be reacted with 'diethylsulfatetoyield a partially" ethylated zinc-solid that is, thosecompounds having ,more, than, one metal in the compound ,are employable, typical specimens being the-conjplxes-having an alkali metal therein. The rela.- tively pure-monoalkyl compounds'ofthe alkali metals can be employed, 1 although' these compounds generally are dis-advantageous withrespect. to reaction efficiency because or their normally solid, insoluble character, where'- as-manyof the other materials suitable are normally liquids at ,reaction conditions; Typical of the alkyl alkali or alkaline earth metalcompounds suitable in the proc--' ess are; ethyllithium, ethyl sodium, as well as the alkyl compounds having as low asone or up to about eight carbonatomsinthe alkyl radicals.

Additional alkylmetal reagents for the process-are the alkyl derivatives of beryllium and boron. The latter-- group of alkyl compoundsincludes not only the simple" compounds having only one boron atom in the molecule, but also --thealkyl-substitute derivatives-of diborane B H Examples of these alkylboroncompounds are triethylborine, triisobutylborine, trimethylborine, trimethyldL; borane,-tri-n-propylborine, et a1. As with the other polyvalent metals, it is apparent from the above that it is not essential to the process that the alkylboron materials be fully alkyl substituted; butother substituents on the base:

metal are permissible unless they are degrading reactants.-

By the process of this invention as much as 50 percent of the lead in the organic divalent lead salt is directlyconverted to tetraalkyllead-and nearly percent is con verted whenthe organic tetravalent' lead salts are em? ployed. In the divalent lead embodiment of the process of this invention the unreacted lead is in highly active form as lead metal and is ideally suited for employment in g the commercial process employing sodium-lead alloy 7 or inthat which proposes the reaction of-metallic lead with-3 an 'alkylating- :agent in the presence of magnesium and-a-catalyst. Converselygrthe lead soproduced by this. invention can be: treated; and convertedagain to a lead salt of an organicacid and, employed in making an. alkyllead.

While this invention. is adaptable to the production of ky ea mpqn s-. e a- 1v t' e n the: krk, radicalsindividually contain from oneto abouteight can,

bon ,atoms, ion cotwen ience in ;describirig this invention sometimes hereinafter specific reference will be made to tetraethyllead, the most widely known because of its use as an antiknock agent. Whenever, in the following description, this material is referred to, it is to be understood that other tetraalkyllead compounds can be made by this process. Further, for convenience in description below, reference may be made to non-lead alkylmetal compound. It will be understood that this refers to alkyl compounds of active metals of groups I-III-A having an electrode potential of over 0.3 such compounds being suitably used for treating the lead salts.

The particular details of carrying out any one embodiment of the process may .vary appreciably from others, dependent upon the physical properties of the non-lead alkylmetal compound employed, and of course of the tetraalkyllead product released. A more or less generally applicable reaction procedure is initiated by providing a finely divided lead salt and feeding it into a suitable solvent or suspending medium in a stirred reaction-vessel, said vessel being equipped with means for supplying and removing heat and .introduction of liquids. The vessel is preferably equipped to handle moderate pressures in a sealed system, in many instances, atmospheric pressure operations being fully suitable. To the solution or suspension of the organic lead salt is introduced with agitation the non-lead alkylmetal reactant which may be diluted with a solvent or carrying medium. In many instances the reaction proceeds at moderate temperature and as the addition of the alkylmetal reactant proceeds mild refrigeration is applied to the reaction system until all the reactants are blended. To insure completeness of reaction, after such addition, external heating can be applied for a moderately long period of time after which the contents of the vessel'are cooled to a convenient handling temperature and discharged into a recovery system. The recovery system employedidepends partly upon the nature of the tetraalkyllead compounds produced and the nature of the by-product metal compound. In the typical manufacture of the lower tetraalkyllead compounds, such as for example tetraethyllead, wherein aluminum triethyl is reacted with lead acetate in the presence of a medium boiling hydrocarbon, it is convenient to discharge the reaction product mixture and to separate the solids, largely lead from the liquid components. The liquid phase can then be resolved by a multiplate vacuum fractionation to give a pure or relatively pure tetraalkyllead product and a separate hydrocarbon reaction medium stream.

While the above general procedure for conducting the process of this invention refers to a batch operation, in many instances improved operation can be obtained by employing a continuous reaction system wherein the two reactants are continuously and separately delivered in appropriate carrying media to a reaction zone and continuously discharging the products of the reaction to an appropriate recovery system.

When the process of this invention is conducted in the presence of an inert carrier liquid it is convenient to select the liquid so that at least one of the reactants is soluble therein. Thus, a controllable reaction is readily achieved, a distinct advantage of the process of this invention. Thus, many of the lead organoacid salts are at least partly soluble in hydrocarbons. For such reactants toluene, benzene, xylene, hexanes, kerosene and the like can be employed. Furthermore, when a normally liquid nonlead alkylmetal is to be reacted with such lead organoacid salts in such a hydrocarbon system, a homogeneous single phase reaction'is frequently achieved, with precipitation during the course of the reaction of a non-lead metal salt corresponding to the lead salt employed. Recovery of the products from such a reaction can be eifected by filtration of the aluminum byproduct and the tetraalkyllead compound dissolved in the hydrocarbon can be further processed for purification or employed as such.

- When certain other non-lead alkylmetal reactants are employed such as for example sodium aluminu'rn tetraethyl, a two phase reaction system may result and in such instances the reaction is enhanced by employing such reactants in finely divided form and maintaining v eflicient agitation. In other cases, the non-lead alkylmetal may be a liquid substantially insoluble in any other liquid phase present. In such instances several liquid phases will be present.

In certain instances it is preferable to employ the tetraalkyllead compound itself as the inert diluent. Thus, the recovery of products is simplified and particularly in a continuous operation the materials handling problem and purificationis minimized. This is particularly advantageous when employing non-lead alkylmetal compounds which' are soluble in tetraalkyllead compounds, such a system, however, can also be employed when reacting certain of the mixed alkylmetal compounds or complexes such as for example the sodium fluoridealuminum triethyl complex, the aluminum alkyl hydrides, aluminum sesquihalides, alkylzinc halides, and sodium zinc triethyl.

The examples given hereafter illustrate generally the numerous forms and embodiments of the process.

Example I The equipment employed in the present example consisted of a stirred reaction vessel equipped with cooling and heating means as well as means for introducing the reactants to the reaction zone. To this reaction vessel was added 17.1 parts of finely pulverized and dried lead diacetate. The reaction vessel was purged with dry nitrogen gas and 100 parts of toluene was added followed by the addition of 4.09 parts of triethylaluminum. The suspension was stirred for a period of about 0.5 hour at which time the reaction temperature was slowly increased by external heating means to the reflux temperature of the solvent (110 C.) and maintained there for an additional period of 1 hour. At this time the reaction vessel was cooled to room temperature and the mixture was then filtered to remove the solid constituents. The filtrate thus obtained was washed with an equal volume of water and the organic layer was then transferred to a fractionating still for removalof the toluene and recovery of the tetraethyllead from the mixture. A 92% yield of high purity tetraethyllead was obtained.

Similarly, when trimethylaluminum, tripropylaluminum, tributylaluminum, trihexylaluminum' and trioctylaluminum are employed in the process of the foregoing example, equally satisfactory yields of tetramethyllead, tetrapropyllead, tetrabutyllead, tetrahexyllead and tetra: octyllead are produced, respectively.

Example II I e The procedure of Example I is repeated except that stoichiometric amounts of triethylgallium and lead diacetate are reacted in the presence of cyclohexane at atmospheric pressure and at a reaction temperature of about to 95 C. for about 3 hours. A high yield of tetraethyllead is obtained.

Example III Tetraethyllead is again prepared in high yield by reacting triethylindium with essentially a stoichiometric amount of lead tetraacetate in the presence of benzene as a dispersing medium under reflux conditions for a reaction time of about 2% hours.

Example IV Example I is repeated essentially as described with the exception that 15.5 parts of lead tetraacetate and 4.0 parts of triethylaluminum were employed. The reaction temperature was maintained between 0 and 10 C. for a total reaction time of 2.5 hours and at the end of which time the reaction mixture was worked up in an identical manner to that of Example I. A yield of tetra;

' lium, trioctylgallium, trimethylindium and triethylindium areemployed in the process. of. the above examples equally as goodyieldsqof the. corresponding tetraorganolead compounds are obtained.

ExampleV The equipment employedin, this example was essentially, as, described in Example ,I.v To the reaction vessel was added 22.8 parts of. lead-diacetate and 50 parts of anhydrous toluene. The, suspension was vigorously stirred under a nitrogen atmosphere and5.8. parts of sodium aluminum. tetraethyl was introduced into the reaction zone. The reactionmixture was heated to the reflux temperature (110 C.) and maintained there for a period of about 3'hours. The temperature was reduced to room temperature andthe reaction mixture worked up in an identical manner to that of Example I to recover the tetraethyllead in a 73.5 yield based on the quantity of sodium aluminum tetraethyl employed.

Example VI The procedure of Example V is repeated except that stoichiometric, quantities ofleadtetraacetate andsodium aluminum tetraethyl are employed as the reactants. At a reaction temperature of about 85 -95 C. a high yield of 'tetraethyllead'is obtained after a reaction periodof' about'4 hours. No metallic lead was formed.

Equally good results are'obtained when alkyl metal complex compounds such as lithium aluminum tetraethyl, sodium aluminum tetrabutyl, sodium gallium tetraethyl, potassium gallium tetraethyl and sodium indium tetraethyl areemployed 'in the processes of'Examples ;V and VI.

Example VII Again employing'the procedure of Example I, tetraethyllead is obtained in high yield when diethylaluminumhydride is reacted with lead diacetate in essentially stoichiometric quantities in'a toluene reactionmedium. The reaction i con-ducted at the reflux temperature of toluene (110 C.) for a reaction period of about 6 hours.

Example VIII The procedure of Example I is again repeated except that 44 parts'of methylaluminumdihydride and 325 parts of lead diacetate are'suspended in 100 parts of benzene in the reaction vessel. The reaction is conducted for a period of about 8 hours at a reaction temperature of 50 C. and the tetramethyllead recovered therefrom in the manner of Example I. An excellent yield of tetramethyllead is obtained.

When diisobutylaluminum hydride, methylaluminum dihydride, methylgallium dihydride, isobutylindium dihydride, diisobutylgallium hydride, and diethylindium hydride are employed as the alkyl metal hydride in the process of Example VII equally as good yields of the corresponding tetraalkyllead compounds are obtained.

Example IX In a similar processes is shown in Example I, 247.5 parts of ethylaluminum sesquichloride are introduced into thereaction vessel which contain 150 parts of xylene. The mixture is stirred ata rapid rate during the addition of 443 parts of lead tetraacetate, the reaction and the introduction being conducted under a blanket of dried and purified nitrogen. The reaction mixture is maintained at a temperature of about 90 C. for a total reaction time of about 3 hours at the end of which time the temperature is reduced to room temperature and the reaction mixture subjected to the separation steps described ingExample I. A high yield of tetraethyllead is obtained.

Similarly, excellent: results are obtained when dimethylaluminum chloride, methylaluminum sesquichloride, ethyl: aluminumsesquibromide, :dimethylgallium chloride, ethyl: gallium sesquichloride, .butylgallium .sesquichloride,.octylindium sesquichloride, and. dipropylindium. chloride. are employed.intheprocess of .ExampleIX in the. place of, the- :ethylaluminum; sesquichloride.

Example X Excellent. yields. of. tetrabutyllead are; obtained when stoichiometric quantities of-sodium aluminum tributyle hydride and. lead: p al'mitate are: employed; in a similar process .to. thatzofzExampleiI. Thereaction is conducted aha-temperature .ofiabontg40f C. for. a reactiontimeof about:8 hoursand theproduct isrecovered in themanner. of Example I.

The. use of potassium aluminum. dioctyldihydride, po-: tassium, aluminum gdiethyldihydride, potassium gallium tripropylhydride, and: lithium indium. triethylhydride in the..above reaction. also.results;in excellentyields ofthe corresponding.organoleadcompounds.

Example XI This example demonstrates the suitability of employing the complex salts of the alkylmetal compounds with sodiumlluoride in the process of this invention. The equipment and procedures employed were similar to those ofExample-Lexcept that 156 parts of sodium aluminum triethylfiuoride and- 325 parts of lead diacetate in the presence of. ZOOparts -of cyclohexane were employed'as the reactants. The reactionwas conducted at a temperatureof about 100 C. fora period ofabout 4 hours. At the conclusion ofthe reaction the temperature was reduced toroom temperatureand the reaction mixture subjected to air-actionation process as described in ample I. An excellent yield of tetraethyllead was obtained. The-sodium. fluoride formed as; aby -product in this process is recovered for use in the formation of addi: tional sodium aluminum triethylfluoride.

Example 'XII Example. I is repeated essentially as described with the exception that tetraethylleadis employed as-the diluent and the reaction temperature is to C. In this instance, the process-is conducted continuously by the continuous feeding of the triethylaluminum and lead diacetate to the reactor and withdrawing a slurry of solids in tetraethyllead from the reactor while leaving a heel of tetraethyllead suificient to maintain the fluidity V of the reaction mixture.

Example XIII The process of'Example I was repeated except that 40.4 parts ofleaddistearate and'4.'1 parts of triethylaluminum were reacted together in 100 parts toluene at reflux temperature. A 81% yield of tetraethyllead'was obtained.

Example XIV' The suitability of usingsalts containing Pb-S bonding Example XV When the procedure of Example I is again repeated but employing 321.8 parts of lead phenolate and 98 parts of triisobutylaluminum. in alphamethyl naphthalene a solvent'themesults obtained'are similar to those of Example I. A high yield of tetraisobutyllead 'is ob ained.

Example X VI The process of Example I is repeatedexce'pt that a mixed alkylaluminum compound is employed. Thus, stoichiometric quantities of methyldiethylaluminum and lead tetraacetate are employed in the procedure of Example I to give an excellent yield of alkylated lead products including tetramethyllead, tetraethyllead, methyltriethyllead, dimethyldiethyllead, and trimethylethyllead.

Equally good results are obtained when lead butyrate, lead formate, lead citrate, lead phenol sulfonate, lead salicylate, and lead naphthenate are employed as the lead salts in the processes of the above examples. As evident from the foregoing examples, it is customary to employ the reactants of any particular embodiment of the process in stoichiometric proportions. However, it will also frequently be found desirable to provide an excess of one or the other of the reactants according to specific circumstances.

The foregoing examples illustrate principally embodiments of the process wherein the non-lead alkymetal compound is a compound of an aluminum type metal. Other alkylmetal compounds of polyvalent metals are also frequently efiectively used as shown by the following examples.

Example X VII A reaction vessel, provided with a vapor outlet and an internal agitator, was carefully dried and flushed several times with dry nitrogen. To the reaction space was added while agitating 40 parts of dry toluene, 11.5 parts of anhydrous lead diacetate and 4.32 partsof diethyl zinc. The foregoing charge ratio is equivalent to equimolal proportions of the lead acetate and diethylzinc.

Immediately on adding the diethyl zinc, the reaction mixture turned black and heat was evolved, showing that thereaction started immediately; Stirring was continued, after charging all components, for a one-hour period. At that time the temperature was raised to about 110 C., or enough to cause vaporization and-refluxing of the toluene from an overhead condenser. This refluxing was continued for an additional period of aboutone hour.

Upon completion of the foregoing, the reacted mixture was inserted or poured into a volumetric calibrated container, and diluted to approximately twice the volume with benzene solvent. Aliquot portions of the reaction mixture were then analyzed and a yield of about 90 percent tetraethyllead was found.

The tetraethyllead is recoverable as a relatively pure product by filtration of the organic layer from the reaction product mixture, and by vacuum distillation or fractionation of the several components thereof.

Instead of the diethylzinc used in the foregoing example, equivalent amounts of other dialkylzinc compounds can be substituted. Thus, when diisopropylzinc or dioctylzinc are substituted for the diethylzinc, similar high yields of tetraisopropyllead and tetraoctyllead are obtained.

Example XVIII The procedure followed in Example XVII is repeated, except that about 7.8 parts of lead tetraacetate is used in place of the lead diacetate. A good yield of tetraethyllead from the lead tetraacetate converted is obtained.

As previously mentioned, it is not essential that a fully alkylated metal reagent be employed in treating the lead organoacid salt, as further shown by the following example.

Example XIX Lead diacetate and ethylzinc hydride, in the proportions of about 24 parts of lead diacetate to parts of ethylzinc hydride are reacted together in the presence of a substantial amount of benzene as a reaction medium. A high conversion of the lead diacetate to a good yield of tetraethyllead is obtained.

About 30 parts of zinc metal is heated with 71 parts of diethyl sulfate at a temperature of over C. for a period of over one hour. A granular solid mass is produced; treatment of portions of this solid with isopropanol showed that it contained about 13 weight percent active ethyl groups.

The solid was mixed with lead diacetate in the proportions of 100 parts of solids and 75 parts of lead diacetate, in the presence of about'50 parts of toluene. After heating for about one hour at refluxing conditions, a production of about 20 parts of tetraethyllead was produced.

Frequently it will be desirable to employ an alkyl compound of an alkali metal, similarly to the reaction shown in the following example.

Example XXI Sodium ethyl and lead diacetate are fed to a reaction vessel in approximately 2 to 1 molal proportions, concurrently with sufficient aromatic solvent to provide a thin slurry. The mixture is heated with stirring at about C. for about three hours. A high conversion of the lead diacetate and a good yield of tetraethyllead are provided,

Example XXII Lead diisobutyrate, 300 parts, and triethylborine, 100 parts, are reacted in the presence of about 500 parts of ethylbenzene at atmospheric pressure and with continuous stirring at C. After continuing the reaction for several hours, a good conversion of the lead diisobutyrate and a high yield of tetraethyllead are obtained.

Notonly are lead organo acid salts effective in supplying thesole lead source in production of tetraalkylleads, but, these reactants are also highly effective in conjunction with other reactions, providing that at least some bonds of a polyvalent metal are occupied by alkyl groups. Thus, a lead organo acid salt can be employed sequentially with an inorganic lead salt, for example, lead sulfide or lead oxide, used in proportion sufiiciently to react some, but not all, of the alkyl groups of a polyalkyl metal compound, as is illustrated in the following examples.

Example XXIII About 60 parts by weight of dry toluene was charged to a reaction vessel, and then about 12.3 parts of dry, powdered lead oxide. About 4.2 parts of triethylaluminum was charged, and the reaction mixture was heated to refluxing temperature and heating, with stirring, continued for 2.5 hours, and then about 6.3 parts of lead diacetate was added and the reaction continued for an additional hour. A conversion of 70 percent of the ethyl groups to tetraethyllead was obtained, or about 10 percent more than realized by reacting lead oxide solely.

When other lead organoacid salts are employed in a reaction step supplementing a previous reaction of a lead chalkogen with polyalkylmetal compound under such conditions that only a part of the alkyl groups are converted to tetraalkyllead compounds, similar increases in yield are provided.

A more preferred operation is to supply the lead source in the form of a double salt between the lead organo acid aaaaa l.

salt and the lead chalkogen. These doublesalts'can generally be prepared by reacting a solutionof; the. lead organo acid salt with the lead chalkogen and removalofthe solvent from the system: to form the.;dry.dou ble,-salt. Double salts having varying proportions of lead organo acid salt to lead chalkogen-are known and have been described in the literature.

Example XXIV To 'a solution of 0.3 mole of lead acetate in about 25 parts 'of'waterwas added 0.3- mole of lead oxide and 100 parts of "benzene. The-mixture washeated to'distillofi the benzene-water azeotrope leaving a white'amorphouspowder which was washed-witbpetroleum ether and dried. Theproduct was identified as the double salt, lead acetate lead oxide.

About 30 parts by weight of drytoluene was charged to a reaction vessel followed by the addition of about 6.06 parts of the dried, powdered lead acetate-lead oxide double salt prepared above. The reaction mixture was heated to' refluxing temperature and heating and stirring continued for one hour while concurrently adding a'solution of about 1.68 parts of triethylaluminum in about. 40 parts of toluene. Heating and stirring was continued for an additional hour after the addition of this material and the reaction mixture was then cooled to room temperature and the tetraethylleadrecovered- .A conversion of 78' percent ofthe ethyl groups to .tetraethyllead was obtained.

When double salts of-otherlead-organo acid salts and lead chalkogens are employed in similar reactions equally desirable increases in yield are obtained.

The pressure employed in the reaction vessel is not critical and usually ranges between aboutatrnospheric pressure and the autogenous pressure created by the carrier liquid at the temperature employed.

The temperature required to initiate the self-sustaining reaction of this invention varies with the alkyllead compound being produced and the non-lead alkylmetal compound-being-reacted. In general it is-preferred to employ temperature conditions under which the reactants and-products'are stable. Towards this end thermal stabilizers well known to the art, such as'for example naphthalene'and styrene, can be employed to permitthe use of high reaction temperatures without concomitant de-.

composition of the alkyllead compounds. Generally temperaturesbetween--about 20 to200 C. and' preferably between about 25" and C. can be employed to initiate or conduct the present operation.

From' the-foregoing description and examples, it will i be evident'-that the process of the inventioniscapable?of a very large number of embodiments without departing from-thescopethereof3 Thus the mechanics of carry ing;out thereaction, including the temperature -and-pres-' sure conditions; the-physical state of the reactants, and

thereaction medium employed, when one is used; can-be greatly varied.

'Whatis claimed is:

'1. A processfor manufacturing tetraalkyllead'compoundswhich comprises reacting in an inert carrierliqni'd a lead salb of an organic-acid wherein lead is attachedto carbonthrou-gh an-intermediate chalkogematom selected I from the group consisting ofoxygen and sulfurand wherein said-organic acidcontains from l te-25 carbon atoms'inclusive with'an alkyl metal compound of a metal having an electrode potential of more than 0.3 volt,-and

wherein each. alkyl groupof said alkyl metal compound} containsup to 8 carbonatoms inclusive.

2. Theprocess. of claim 1 wherein the metal of-said alkyl metal compound isav polyvalentmetal.

3. Process ofclaim l-whereinsaid lead saltis a.salt of an acid selected from the group consisting of alkanoic', carboxyaromatic, and phenolic acids.

4. The process of claim 3 wherein said lead salt is lead diacetate:

5. Theprocessof claim 3 wherein said lead salt is lead naphthenate;

6. The process of claim 3 wherein said-alkyl metal compound-is agrbup. IImetal alkyl;

'7; The processof'claim'6 wherein said groupllmetal comprises-'reacting'lead diacetate with triethylaluminum 1 inthemolal proportions' of'about 1 /2 to 1 in-the-presence of an inert carrier liquid at a temperature between about25-to-l50 C.

References Citedin the file-of this patent UNITEDSTATES PATENTS 1,938,180 Groll Dec. 5. 1,933

Claims (1)

1. A PROCESS FOR MANUFACTURING TETRAALKYLLEAD COMPOUNDS WHICH COMPRISES REACTING IN AN INERT CARRIER LIQUID A LEAD SALT OF AN ORGANIC ACID WHEREIN LEAD IS ATTACHED TO CARBON THROUGH AN INTERMEDIATE CHALKOGEN ATOM SELECTED FROM THE GROUP CONSISTING OF OXYGEN AND SULFUR AND WHEREIN SAID ORGANIC ACID CONTAINS FROM 1 TO 25 CARBON ATOMS INCLUSIVE WITH AN ALKYL METAL COMPOUND OF A METAL HAVING AN ELECTRODE POTENTIAL OF MORE THAN 0.3 VOLT, AND WHEREIN EACH ALKYL GROUP OF SAID ALKYL METAL COMPOUND CONTAINS UP TO 8 CARBON ATOMS INCLUSIVE.