US3048610A

US3048610A - Process for making tetramethyl lead

Info

Publication number: US3048610A
Application number: US50605A
Authority: US
Inventors: John M S Jarvie; Mathias J Schuler; Jr John D Sterling
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1960-08-19
Filing date: 1960-08-19
Publication date: 1962-08-07
Anticipated expiration: 1979-08-07

Description

lid ldfild Fatenteel Aug. 19%2 t it l .1 titt d l area ass-acre l litltll'lfid FUR MAZQLNG TETRAMETHYL LEAD .lohn M. S. ,larvie, Eastwood, New South Wales, Aus= traiia, and Mathias ll. Schiller, Pittman, and .i'ohn D. Sterling, .lr.., Wenonah, Nul assign-tors to 1. du Pont de Nemours Company, Wilmington, Deb, a corporation of Betas are No Drawing. Filed Aug. 19, 1969, er. No. 50,6tl5

ltd Claims. (Cl. Edd- 437) This invention relates to a process for the manufacture of tetramethyl lead, particularly by the reaction of a methyl halide with a sodium lead alloy in the presence of a catalyst.

It is Well known that tetraalkyl lead compounds are useful as antilrnocl: agents in fuels for internal combustion engines. Up to the present time, tetraedtyl lead has been manufactured and used predominantly. However, tetramethyl lead, particularly because of its higher volatility, can be used advantageously as an antiknoclr agent in motor fuels, alone or in combination with tetraethyl lead and the like in varying proportions to improve the road performance of leaded fuels, as more fully described by Smyers et al. in US. Patent 2,310,376. Calingaert et al. in US. Patent 2,270,109, disclose a process for preparing a mixture of tetra-methyl and ethyl lead compounds by reacting a mixture of methyl chloride and ethyl chloride with sodium lead alloy in the presence of an aluminum type catalyst. Such process results in a mixture of five tetraalkyl lead compounds in which tetramethyl lead is present in a minor proportion. The process of Calingaert et al. does not constitute an economical process for making pure or substantially pure tetramethyl lead in large quantities and does not yield the combination of tetraalkyl lead compounds in the proportions required for many purposes disclosed by Smyers et al.

The manufacture of tetramethyl lead by the general alkyl halide-sodium lead alloy reaction requires special conditions. Whereas the ethyl chloride-sodium lead alloy system does not require catalysis and can be accelerated by such substances as ketones, alcohols, acetals, etc. known in the art, the methyl chloride-lead alloy system responds not at all or poorly to the presence of such accelerators and to conditions otherwise conducive to the formation of tetraethyllead. Methyl halides are unique in that only certain catalysts of the aluminum type seem effective to bring about the formation of methylated lead compounds. Even so. the aluminum type catalysts present practical difliculties in commercial scale operation. For example, an induction period is generally encountered before the methylation begins, when using the combination of aluminum alloy and aluminum chloride described by Calingaert et al. in US. Patent 2,270,109 for the manufacture of mixed methyl and ethyl leads from mixtures of methyl and ethyl chlorides. Also, relatively high temperatures (100 C.-ll C.) are required to achieve satisfactory yields of tetramethyl lead. The induction period and high reaction temperature together present the hazard of sudden and uncontrollable reaction (Le. surges in temperature and pressure) once the exothermic methylation begins. This can be particularly serious with tetramethyl lead because of the relative ease with which it can decompose explosively. Aluminum plus aluminum chloride catalysts are ineffective in at least one of the following respects, to avoid the induction period, to initiate reaction at low temperatures, to provide satisfactory reaction control, and to produce tetramethyl lead in good yield safely and in short time.

Other aluminum type catalysts suggested by Calingaert et al., for example, trimethyl aluminum, dlmethyl aluminum chloride and the like, have the disadvantages for commercial use of being difi'icult and hazardous to han- -21 die because of their extreme sensitivity to air and to moisture. On the other hand, it is desirable to be able to use aluminum chloride which is commercially available and presents no unusal storage and handling problems, provided satisfactorily high yields of tetramethyl lead can be obtained with it.

It is an object of this invention to provide a new and improved process for the manufacture of tetramethyl lead. Another object is to provide such a process which is particularly adapted for the large scale manufacture of pure or substantially pure tetramethyl lead. A further object is to provide a catalytic process for reacting a methyl halide with a sodium lead alloy wherein the reaction is initiated without an induction period and proceeds smoothly at relatively low temperatures to produce tetramethyl lead in good yield. A still further obiect is to provide a process for making tetramethyl lead which utilizes an aluminum halide catalyst in combination with an additional agent which materially improves the yield of tetramcthyl lead. Other objects are to advance the art. Still other objects will appear hereinafter.

The above and other objects may be accomplished in accord with this invention which involves the process for making tetramethyl lead which comprises mixing at a temperature below 50 C. a sodium lead alloy, at least about 0.25 mole per mole of sodium of an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, from about 0.05% to about 5% by weight of the alloy of an aluminum halide in which the halogen has an atomic number in the range of 17 to 53, and from about 0.1 to about parts per part of aluminum halide of an organolead compound of the class consisting of hydrocarbon leads and hydrocarbon lead halides in which the halogen has an atomic number in the range of 17 to 53, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 70 C. to about C. and maintaining it at such temperature until the methylation reaction is substantially complete while gradually adding such quantities of said methyl halide as may be required to provide a total of at least one mole thereof for each mole of sodium.

It has been found that by carrying out the reaction in such manner, material advantages and improved results are obtained. By having the organolead compound present when the reaction mixture is subjected to reaction conditions, particularly to temperatures of from 50 C. to about 70 C., the reaction is initiated promptly without an induction period. In other Words, the presence of the added organolead compound provides a smooth and safe initiation of the methylation reaction promptly at relatively low temperatures and ensures a smooth and controlled reaction. This is particularly important at the beginning when the mixture is heated to start the reaction. In addition, the use of the organolead compound to initiate the reaction also provides the unexpected benefit of increased yields of tetramethyl lead, over and above the quantity added to initiate the reaction. This is particularly surprising since tetrarnethyl lead is a product of the reaction between the methyl halide and the sodium lead alloy, and it is not obvious why the system does not respond to the presence of such organolead compound formed in situ to give the high yields of tetramethyl lead which are characteristic of the process of this invention.

Broadly, the overall process comprises mixing the sodium lead alloy, the methyl halide, the aluminum halide catalyst, and a small proportion of added organolead compound at a temperature below 50 C. at which the relction does not readily take place, then heating the mixul'C with agitation to a temperature at which the reaction is initiated and, when the reaction has become well started, gradually raising the temperature to one at which the reaction proceeds at a reasonable rate, completing the reaction at the higher temperature, and then recovering the tetramethyl lead from the reaction mixture by conventional procedures. Reaction temperatures are usually in the range of from 50 C. to about 130 C. and, for reasons of safety, the pressure preferably should be kept below about 500 p.s.i.g., for example, by cooling, controlling the rate of heating and/or the amount of methyl halide in the reaction zone, and by venting. The reaction requires one mole of methyl halide for each mole of sodium in the sodium lead alloy. The reaction may be initiated with all of the desired amount of methyl halide present or with a fraction of the required amount of methyl halide present, followed by gradual addition of the rest of the desired amount as the reaction proceeds.

The alkylating agent employedwill consist of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, i.e. methyl chloride, methyl bromide, or methyl iodide, or a mixture of 2 or more methyl halides. Preferably, the reaction will be carried out with methyl chloride and monosodium lead alloy, NaPb. The total amount of methyl halide employed will be at least one mole and usually not more than 20 moles thereof per mole of sodium as sodium lead alloy, and preferably from about 1.1 to about moles of methyl halide per mole of sodium. When it is desired to gradually add the methyl halide during the reaction, it is best to have present at the initiation of the reaction from about 0.25 to about 0.50 mole of methyl halide per mole of sodium, preferably about 0.50 mole, and to gradually add the rest of the methyl halide after the reaction has been initiated. Larger amounts than about 1.5 moles of the methyl halide can be used to dilute the reaction mass and aid in controlling the reaction temperature. Similarly, the methyl halide can be carried in an inert solvent, such as the hydrocarbons, hexane, benzene, toluene and the like, to dilute the reaction mass.

The process requires, as a catalyst, an aluminum halide in which the halogen has an atomic number in the range of 17 to 53. The term aluminum halide is used in its strict sense to mean the compounds which consist of aluminum and halogen, i.e. AlCl AlBr and A11 The aluminum halide can be used as such or as a suspension, slurry, or solution in an inert liquid carrier such as hexane, benzene, toluene, kerosene or liquefied methyl halide. Metallic aluminum and aluminum alloys may be used in combination with the aluminum halide catalyst as more particularly described by Calingaert et al. in US. Patent 2,270,109, but are unnecessary and usually are without significant advantage. The amount of the aluminum halide catalyst employed usually will be from about 0.05% to about 5% by weight of the sodium lead alloy, and preferably from about 0.5% to about 1.5%.

The organolead compounds employed for initiating the reaction in the process of the present invention will be of the class consisting of hydrocarbon leads and hydro carbon lead halides in which the halogen has an atomic number in the range of 17 to 53. By hydrocarbon leads is meant compounds consisting of lead and hydrocarbon radicals, that is, in which lead is directly joined to hydrocarbon radicals solely. Likewise, hydrocarbon lead halides means compounds consisting of lead, hydrocarbon radicals and one or more of chlorine, bro mine and iodine, in which the leadis directly bonded to 1-3 hydrocarbon radicals and 3-1 halogen atoms. The hydrocarbon radicals include alkyl, alkenyl and aryl radicals which usually will contain 1-10 carbon atoms. Preferably, the hydrocarbon radicals will be alkyl radicals of 1-3 carbon atoms, i.e. methyl, ethyl and propyl, and most preferably methyl radicals. Also, the alkyl leads constitute a preferred class, represented by tetramethyl lead, tetraethyl lead, tetrapropyl lead, methyltriethyl lead,

dimethyldiethyl lead, trimethylethyl lead, and hexaethyl dilead, with tetrarnethyl lead being most preferred. Other representative organolead compounds within this invention are tetraallyl lead, phenyl triethyl lead, vinyltrimethyl lead, dimethyl lead dichloride, diethyl lead dichoride, triethy lead iodide, trimethyl lead bromide, and the like.

Mixtures of any two of more of such organolead com-- pounds may be used, if desired. The organolead compound can be used as such or added to the reaction mixture as a solution in an inert solvent, for example, as a solution of from about 20% to about by weight thereof in a solvent, such as hexane, benzene, toluene, kerosene, and liquefied methyl halide.

Usually and preferably from about 0.4 part to about 20 parts by weight of the organolead compound per part of aluminum halide catalyst will be used. Smaller amounts, down to about 0.1 part, of organolead compound per part of aluminum halide are beneficial. Amounts larger than about 20 parts of organolead compound, e.g. parts or more thereof per part of aluminum halide, while operable, are genrally unnecessary.

It is essential for the purposes of this invention and to obtain the advantageous results thereof that the organolead compound be present in the reactor with the aluminum halide catalyst and the other components when the mixture is subjected to reaction conditions. Accordingly,

at least part of the methyl halide and the other components are mixed at a temperature below 50 C., usually at room temperature or below, i.e. about 20 C. to about 30C. and below, and then the mixture heated to the temperature required for initiation of the reaction. The methylation reaction can be initiated smoothly at temperatures of 50 C. to about 60 C., with temperatures not higher than about 70 C. generally needed. The reaction can be completed at such temperatures. However, the reaction is undesirably slow at such temperatures, and it is usually desirable to employ higher temperatures of from about 70 C. to about 130 C. for completion of the reaction. The production of tetrarnethyl lead proceeds at reasonable rates at temperatures from about 70 C. to about 80 C. However, it is preferred to employ temperatures of from about 100 C. to about C. for rapid completion of the reaction safely.

The importance of these results is that a greater degree of safety is achieved and at a lower operating cost, considering the hazards and expense of using pressurized equipment and having a relatively unstable product such as tetramethyl lead confined at elevated temperatures. To be able to control temperatures and pressures is particularly important in the early stages of the reaction where the danger of a runaway reaction is greatest. Once at least 0.5 mole of methyl halide has reacted with the sodium lead alloy, the danger is greatly lessened and the temperatures can be more ra idly increased to the higher temperatures where the reaction takes place at the optimum rate. In general, the rate of heating and the pressure rise resulting therefrom are coordinated to prevent sharp increases therein, the temperature being raised gradually to the desired maximum temperature. This gradual rise in temperature, if not too rapid, may b continuous from the temperature of mixing the ingredients through the reaction initiation stage to the temperature desired for rapid completion of the reaction, or may be intermittent, a desired.

The reaction is effected under agitation. It is usually desirable to carry out the reaction in the presence of an inert solid, such as graphite or silica, as an internal lubricant, mixing aid, or anti-agglomerant for lead, since ordinarily the reaction mass tends to be somewhat difficult to stir, probably due to the inherent tendency of the particles of free lead to stick together. From about 1% to about 20% by Weight of the alloy are used, depending on the dimensions of the reactor, the effective ness of the agitation means, and the proportions of the reactants.

In practice, the methyl halide is simply added to a reactor which will also contain the sodium lead alloy, aluminum halide, organolcad compound, and usually an internal lubricant, such as graphite, at about room temperature. In a typical run, an autoclave is loaded at room temperature to contain 35 pounds (about 1.5 moles per mole of sodium) of methyl chloride, 0.6 pound of AlCl 0.3 pound of tetramethyl lead, and 3 pounds of graphite per 100 pounds of NaPb alloy, added in any order. Reaction is effected under agitation and pressure by heating to a temperature at which the methylation begins and can be maintained safely at a practical rate. The rate of heating and the pressure rise (as a result of heating) are coordinated to prevent sharp increases. Reaction mass temperature is controlled, by cooling the autoclave when necessary, to keep the internal pressure from exceeding about 300 p.s.i.g. Usually, a temperature of about 50 C.60 C. has to be reached to initiate the rnethylation, and, once the exothermic reaction has started, the temperature is allowed to rise (or is raised) to 100 C.l C. and held there until the reaction is complete.

Alternatively, the methyl chloride can be fed gradually into the autoclave containing the other components. preferably, about 0.25 to about 0.50 mole of methyl chloride per mole of sodium is added before the charge is brought to 50 C.-60 C. where reaction begins. The rest of the methyl chloride is then fed in slowly and the temperature allowed to increase to 100 C.1l0 C. where the reaction is completed. The pressure is kept under about 300 p.s.i.g. by cooling, controlling the methyl chloride feed, and venting of non-condensibles.

To recover the product, the charge is cooled to about C.- C. and residual methyl halide vented to a recovery system, as in tetraethyl lead technology. The tetramethyl lead component can be recovered by solvent extraction, e.g. with toluene, or by steam distillation, according to the well-known methods.

in order to more fully illustrate this invention, preferred modes of carrying it into effect, and the advantageous results to be obtained thereby, the following examples are given in which the amounts and proportions are by weight, except where otherwise specifically indicated.

Example 1 A steel bomb is charged under nitrogen to contain 2.5

parts of graphite, 0.62 part of aluminum chloride, 100 1 warming to room temperature, the bomb is heated over a period of 15 minutes to 110 C., held there for 1 hour, then cooled and opened. Tetramethyl lead is obtained in 86.7% yield on extraction of the reaction mass with. isooetane.

Substantially identical results are obtained in the above procedure by steam distilling rather than extracting the reaction Steam distillation is effected conveniently for reasons of safety in the presence of a hydrocarbon such as toluene, benze e or xylene, and the product recove"ed as a solution, e.g. 80% by weight in the hydrocarbon.

The yield of tetramethyl lead is only 52% when aluminum chloride is used alone in the above procedure.

On using 12 parts of tetraethyl lead in place of the tetramethyl lead as the co-catalyst (or catalyst promoter) in the above procedure, tetramethyl lead is obtained in 61% yield.

When boron fluoride is used instead of aluminum chloride in the above procedure of Example 1, no tetramethyl lead is obtained. This is in contrast to the disclosure of Calingaert et al. in US. Patent 2,270,109 that this substance catalyzes the reaction of mixtures of a methyl halide and ethyl chloride with sodium lead alloy to pro duce a mixture of methyl and ethyl lead tetraalkyl compounds.

Example 2 A stainless-steel lined pressure reactor is loaded in order with 3.4 parts of graphite, 1.3 parts of AlCl 100.4 parts of NaPb alloy, 2.6 parts of tetramethyl lead and parts or" methyl chloride, the weight/volume ratio of the methyl chloride to the total capacity of the bomb corresponding to 0.21 gram/cc. The reaction mass, under agitation, is heated in 7 minutes to 70 C., held there for 3 hours, and cooled. The yield of tetramethyl lead, isolated in the usual manner, is 73.8%.

In contrast, with AlCl alone (i.e. when the added tetramethyl lead is omitted), the yield of tetramethyl lead is 57.2%.

Inferior results are obtained with a mixture of aluminum chloride and aluminum alloy turnings (eg. as an alloy of percent composition 6.2-8.0 Cu, 1.4 Fe, 1.3 Si, 0.5 Mn, 0.07 Mg, 2.2 Zn, 0.3 Ni, 0.2 Ti, 0.5 other, the rest Al) as the sole catalyst combination (i.e. without organolead) under the above conditions. Induction periods of up to about 1 hour are observed before the reaction starts at 70 C., and the yields of tetramethyl lead tend to be even lower than obtained with aluminum chloride alone. For example, the yield is 45.3% when 0.34 part of aluminum chloride and 0.21 part of the aluminum alloy are used and no organolead is added.

Example 3 The procedure of Example 2 is repeated except that (a) the quantity of added tetramethyl lead is 1.2 parts and (b) the reaction mixture is heated in 13 minutes to 70 C., held 3 hours at 70 C., then in 9 minutes raised to 110 C. and held 21 minutes at this temperature, before cooling to room temperature and discharging the product. Tetramethyl lead is obtained from the reaction mass in 80% yield.

Good yields of tctramethyl lead are also obtained by the above procedure on using parts of monosodium lead alloy, 33 parts of methyl chloride, 0.6 part of tetramethyl lead and 0.6 part of aluminum chloride.

Example 4 An alkylation autoclave (equipped with agitation, temperature and pressure control means, and inlet and outlet means) is charged at room temperature with 15,000 parts crushed NaPb alloy, 454 parts graphite, 98 parts alu minum chloride, 87 parts tetramethyl lead as an 80% solution in toluene, and 6350 parts liquid methyl chloride, the latter being added under pressure to the autoclave which is otherwise sealed. The autoclave is closed and the contents, under agitation, is heated during /2 hour to 65 C. to initiate the reaction, and the temperature is controlled so that the pressure is in the range 200 to 300 p.s.i.g. The temperature is gradually raised from 65 C. to C. over a period of 5.5 hours, the temperature rise being coordinated with the pressure which is maintained below 300 and above 200 p.s.i.g. The autoclave is then cooled, vented to recover unreacted methyl chloride, and then discharged. From the discharged product, tetramethyl lead was obtained in about 80% yield.

When the above procedure is modified so that 1725 parts of methyl chloride is charged initially along with the other reactants, and the remaining 4625 parts are added gradually as needed to maintain 200-300 p.s.i.g. pressure at a temperature within the range 65 C.1l0 C., essentially the same yield of tetramethyl lead is realized.

Example 5 Example 1 is repeated, except that 77 parts of methyl bromide is used in place of the methyl chloride and the reaction mixture held at 85 C. for 4 hours, to obtain tctramethyl lead in 71% yield.

Example 6 A S-gallon autoclave was charged under nitrogen atmosphere with 15,100 g. comminuted NaPb alloy, 490 g. flaked graphite, 30 g. aluminum alloy, 50 g. aluminum chloride, 266 g. tctramethyl lead as a toluene solution totaling 2400 g., and 2,950 g. methyl Chloride (liquefied). The autoclave was closed and the charge heated under agitation over a 45 min. period from room temperature to a reaction mass temperature of 80 C. and a pressure of about 260 p.s.i.g. Additional methyl chloride (2,500 g.) was then fed in slowly over a period of about 1 hour, during which time the temperature of the reaction mass increased to 88 C., and the pressure increased to 310 p.s.i.g. The reaction mass was then cooked for about 2% hours with the temperature increasing gradually to 110 C. The pressure reached a maximum of 340 p.s.i.g. before decreasing steadily. The reactor was then cooled to about 40 C., vented, and discharged by dropping its contents to a steam still. The reactor was rinsed with toluene and the rinsings added to the steam still. Steam distillation of the total reaction product gave 3605 g. tctramethyl lead (corrected for the initial 266 g. and toluene). This yield corresponds to 82% of theoretical. In contrast, in substantially otherwise identical runs, one before and one after in the same reactor wherein toluene was added without tctramethyl lead, the yield1 of tetramethyl lead was 65% before and 74% afterwar s.

The aluminum alloy used in these runs was a commercial alloy of the composition in percent: Cu 6.0-8.0, Fe 1.4, Si l.03.0, Mn 0.1, Mg 0.07, Zn 2.2, Ni 0.3, Ti 0.2, other elements 0.5, the remainder Al.

It will be understood that the preceding examples have been given for illustrative purposes solely and that this invention is not restricted to the specific embodiments described therein. n the other hand, it will be readily apparent to those skilled in the art that, subject to the limitations set forth in the general description, many variations can be made in the materials, proportions, conditions and techniques employed, without departing from the spirit and scope of this invention.

From the" preceding description and examples, it will be apparent that this invention provides a new and improved process for making tctramethyl lead in high yields which process overcomes the diificulties and hazards involved in the prior processes. iarticularly, this invention eliminates the induction period ordinarily encountered in prior processes and the hazards involved therein, and permits the initiation of the reaction at lower temperatures in a smooth and safe manner and the reaction to be readily controlled. It produces tctramethyl lead as the predominant product and makes it possible to safely and economically produce pure or substantially pure tctramethyl lead in high yields. Furthermore, this invention provides a process whereby tctramethyl lead can be readily obtained in materially higher yields than could be obtained heretofore. Accordingly, it will be apparent that this invention constitutes a valuable advance in and contribution to the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. The process for making tctramethyl lead which comprises mixing at a temperature below 50 C. a sodium lead alloy, at least about 0.25 mole per mole of sodium of an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, from about 0.05% to about 5% by weight, based on said alloy, of an aluminum halide in which the halogen has an atomic number in the range of'l7 to 53, and from about 0.1 to about 100 parts per part of aluminum halide of an onganolead compound of the class consisting of hydrocarbon leads and hydrocarbon lead halides in which the halogen has an atomic number in the range from 50 C. to about 70 C. to initiate the methylationreaction, and then heating the mixture to a temperature of from about 70 C. to about 130 C. and maintaining it at such temperature until the methylation reaction is substantially complete while gradually adding such quantities of said methyl halide as may be required to provide a total of at least one mole thereof for each mole of sodium.

2. The process for making tctramethyl lead which comprises mixing at a temperature below 50 C. a sodium lead alloy, from about 0.25 mole to about 20 moles per mole of sodium of an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, from about 0.05% to about 5% by weight, based on said alloy, of an aluminum halide in which the halogen has an atomic number in the range of 17 to 53, and from about 0.4 to about 20 parts per part of aluminum halide or" a hydrocarbon lead in which the hydrocarbon groups are alkyl radicals of 1 to 10 carbon atoms, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 70 C. to about 130 C. and maintaining it at such temperature until the methylation reaction is substantially complete while gradually adding such quantities of said methyl halide as may be required to provide a total of at least one mole thereof for each mole of sodium.

3. The process for making tctramethyl lead which comprises mixing at a temperature below 50 C. a sodium lead alloy, from about 0.25 mole to about 20 moles per mole of sodium of an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, from about 0.05 to about 5% by weight, based on said alloy of an aluminum halide in which the halogen has an atomic number in the range of 17 to 53, and from about 0.4 to about 20 parts per part of aluminum halide of a tetraalkyllead in which each alkyl group contains 1-3 carbon atoms, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 70 C. to about C. and maintaining it at such temperature until the methylation reaction is substantially complete while gradually adding such quantities or" said methyl halide as may be required to provide a total of at least one rnole thereof for each mole of sodium.

4. The process for making tctramethyl lead which comprises mixing at a temperature below 50 C. a sodium lead alloy, from about 0.25 mole to about 5 moles per mole of sodium of an alkylating agent which consists of methyl chloride, from about 0.5% to about 1.5% by weight based on said alloy, of aluminum chloride, and from about 0.4 to about 20 parts of tctramethyl lead per part of aluminum chloride, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 70 C. to about 110 C. and maintaining it at such temperature until the methylation reaction is substantially complete while gradually adding such quantities of methyl chloride as may be required to provide a total of at least one mole thereof for each mole of sodium.

5. The process for making tctramethyl lead which comprises mixing at a temperature below 50 C. a sodium lead alloy, from 1 mole to about 20 moles per mole of sodium of an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, from about 0.05% to about 5% by weight based on said alloy, of an aluminum halide in which the halogen has an atomic number in the range of 17 to 53, and from about 0.4 to about 20 parts per part aoaaero of aluminum halide of a hydrocarbon lead in which the hydrocarbon groups are alkyl radicals of 1 to 3 carbon atoms, heating the mixture LO a temperature of from 5 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 70 C. to about 130 C. and maintaining it at such temperature until the methylation reaction is substantially complete.

6. The process for making tetramethyl lead which comprises mixing at a temperature below 50 C. a sodium lead alloy, from 1 to about moles per mole of sodium of an alkylating agent which consists of methyl chloride, from about 0.05% to about 5% by weight, based on said alloy, of aluminum chloride, and from about 0.4 to about 20 parts of tetramethyl lead per part of aluminum chloride, heating the mixture to a temperature of from 5 0 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 70 C. to about 110 C. and maintaining it at such temperature until the methylation reaction is substantially complete.

7. The process for making tetramethyl lead which comprises mixing at a temperature below 50 C. a sodium lead alloy, from about 0.25 mole to about 20 moles per mole of sodium and an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, from about 0.05% to about 5% by Weight, based on said alloy, of an aluminum halide in which the halogen has an atomic number in the range of 17 to 53, and from about 0.4 to about 20 parts per part of aluminum halide of a hydrocarbon lead halide in which the halogen has an atomic number in the range of 17 to 53 and the hydrocarbon groups are alltyl radicals of 1 to carbon atoms, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 70 C. to about 130 C. and maintaining it at such temperature until the methylation reaction is substantially complete while gradually adding such quantities of said methyl halide as may be required to provide a total of at least one mole thereof for each mole of sodium.

8. The process for making tetramethyl lead which comprises miXing at a temperature below 50 C. a sodium lead alloy, from about 0.25 mole to about 5 moles per mole of sodium of an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, from about 0.5% to about 1.5% by weight, based on said alloy of an aluminum halide in which the halogen has an atomic number in the range of 17 to 53, and from about 0.4 to about 20 parts per part of aluminum halide of a dialkyl lead dihalide in which each alkyl group contains l-3 carbon atoms and the halogen has an atomic number in the range of 17 to 53, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 70 C. to about 110 C. and maintaining it at such temperature until the metiylation reaction is substantially complete while gradually adding such quantities of said methyl halide as may be required to provide a total of at least one mole thereof for each mole of sodium.

9. The process for making tetramethyl lead which comprises m' ing at a temperature below 50 C. a sodium lead alloy, from about 0.25 mole to about 5 moles per mole of sodium of an alkylating agent which consists of methyl chloride, from about 0.5% to about 1.5% by Weight, based on said alloy, of aluminum chloride, and from about 0.4 to about 20 parts of dimethyl lead dichloride per part of aluminum chloride, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 70 C. to about 110 C. and maintaining it at such temperature until the '10 methylation reaction is substantially complete while gradually adding such quantities of methyl chloride as may be required to provide a total of at least one mole thereof for each mole of sodium.

10. The process for making tetramethyl lead which comprises mixing at a temperature below 50 C. a sodium lead alloy, from 1 to about 5 moles per mole of sodium of an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53, from about 0.05% to about 5% by Weight based on said alloy, of an aluminum halide in which the halogen has an atomic number in the range of 17 to 53, and from about 0.4 to about 20 parts per part of aluminum halide of a hydrocarbon lead halide in which the halogen has an atomic number in the range of 17 to 53 and the hydrocarbon groups are alkyl radicals of 1 to 3 carbon atoms, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate methylation reaction, and then heating the mixture to a temperature of from about 70 C. to about 130 C. and maintaining it at such temperature until the methylation reaction is substantially complete.

11. The process for making tetramcthyl lead which comprises mixing at a temperature below 5 0 C. a sodium lead alloy, from 1 to about 5 moles per mole of sodium of an alkylating agent which consists of methyl chloride, from about 0.5% to about 1.5 by weight, based on said alloy, of aluminum chloride, and from about 0.4 to about 7 20 parts of dimethyl lead dichloride per part of aluminum chloride, heating the mixture to a temperature of from 50 C. to about 70 C. to initiate the methylation reaction, and then heating the mixture to a temperature of from about 70 C. to about C. and maintaining it at such temperature until the methylation reaction is substantially complete.

12. The process for making tetramethyl lead which comprises initiating at a temperature of from about 50 C. to about 70 C. the reaction of a sodium lead alloy and an alkylatinag agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53 in the presence of from about 0.05% to about 5% by weight, based on said alloy, of on aluminum halide in which the halogen has an atomic number in the range of 17 to 53 and from about 0.1 to about 100 parts per part of aluminum halide of an organolead compound of the class consisting of hydrocarbon leads and hydrocarbon lead halides in which the halogen has an atomic number in the range of 17 to 53, and the hydrocarbon groups contain 1 to 10 carbon atoms and are selected from alkyl, allcenyl and aryl radicals, then heating the mixture to a temperature of from about 70 C. to about C. and maintaining the mixture at the latter temperature until the methylation reaction is substantially complete.

13. The process for making tetramethyl lead which comprises initiating at a temperature of from about 50 C. to about 70 C. the reaction of a sodiurn lead alloy and an alkylating agent which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53 in the presence of from about 0.05% to about 5% by Weight, based on said alloy, of an aluminum halide in which the halogen has an atomic number in the range of 17 to 53 and from about 0.4 to about 20 parts per part of aluminum halide of a hydrocarbon lead in which the hydrocarbon groups are alkyl radicals of 1 to 10 carbon atoms, then heating the mixture to a temperature of from about 70 C. to about 130 C. and maintaining the mixture at the latter temperature until the methylation reaction is substantially complete.

14. The process for making tetramethyl lead which comprises initiating at a temperature of from about 5 0 C. to about 70 C. the reaction of a sodium lead alloy and an alkylating agent which consists of methyl chloride in the presence of from about 0.05% to about 5% by spa-acre l l. Weight, based on said alloy, of aluminum chloride and from about 0.4 to about 20 parts of tetramethyl lead per part of aluminum chloride, then heating the mixture to a temperature of from about 70 C. to about 110 C. and maintaining the mixture at the latter temperature until the methylation reaction is substantially complete.

15. The process for making tetramethyl lead which comprises initiating at a temperature of from about 50 C. to about 70 C. the reaction of a sodium lead alloy and an alkylating agent Which consists of a methyl halide in which the halogen has an atomic number in the range of 17 to 53 in the presence of from about 0.05% to about by Weight, based on said alloy, of an aluminum halide in which the halogen has an atomic number in the range of 17 to 53 and from about 0.4 to about 20 parts per part of aluminum halide of a hydrocarbon lead halide in which the halogen has an atomic number in the range of 17 to 53 and the hydrocarbon groups are alkyl radicals of 1 to 10 carbon atoms, then heating the mixture to a temperature of from about 70 C. to about 130 C. and I maintaining the mixture at the latter temperature until the methylation reaction is substantially complete.

16. The process for making tetramethyl lead which comprises initiating at a temperature of from about C. to about C. the reaction of a sodium lead alloy and an alkylating agent which consists of methyl chloride in the presence of from about 0.5% to about 1.5% by Weight, based on said alloy, of aluminum chloride and from about 0.4 to about 20 parts of dimethyl lead dichloride per part of aluminum chloride, then heating the mixture to a temperature of from about 70 C. to about C. and maintaining the mixture at the latter temperature until the methylation reaction is substantially complete.

References Cited in the tile of this patent UNITED STATES FATENTS 2,270,109 Calingaert et al. Jan. 13, 1942

Claims

1. THE PROCESS FOR MAKING TETRAMETHYL LEAD WHICH COMPRISES MIXING AT A TEMPERATURE BELOW 50*C. A SODIUM LEAD ALLOY, AT LEAST ABOUT 0.25 MOLE PER MOLE OF SODIUM OF AN ALKYLATING AGENT WHICH CONSISTS OF A METHYL HALIDE IN WHICH THE HALOGEN HAS AN ATOMIC NUMBER IN THE RANGE OF 17 TO 53, FRAOM ABOUT 0.05% TO ABOUT 5% BY WEIGHT, BASED ON SAID ALLOY, OF AN ALUMINUM HALIDE IN WHICH THE HALOGEN HAS AN ATOMIC NUMBER IN THE RANGE OF 17 TO 53, AND FROM ABOUT 0.1 TO ABOUT 100 PARTS PER PART OF ALUMINUM HALIDE OF AN ORGANOLEAD COMPOUND OF THE CLASS CONSISTING OF HYDROCARBON LEADS AND HYDROCARBON LEAD HALIDES IN WHICH THE HALOGEN HAS AN ATOMIC NUMBER IN THE RANGE OF 17 TO 53 AND THE HYDROCARBON GROUPS CONTAIN 1 TO 10 CARABON ATOMS AND ARE SELECTED FROM ALKYL, ALKENYL AND ARYL RADICALS, HEATING THE MIXTURE TO A TEMPERATURE OF FROM 50*C. TO ABOUT 70*C. TO INITIATE THE METHYLATION REACTION, AND TAHEN HEATING THE MIXTURE TO A TEMPERATURE OF FROM ABOUT 70*C. TO ABOUT 130*C. AND MAINTAINING IT AT SUCH TEMPERATURE UNTIL THE METHYLATION REACTION IS SUBSTANTIALLY COMPLET WHILE GRADUALLY ADDING SUCH QUANTITIES OF SAID MWTHYL HALIDE AS MAY BE REQUIRED TO PROVIDE A TOTAL OF AT LEAST ONE MOLE THEREOF FOR EACH MOLE OF SODIUM.