US2558207A - Manufacture of alkyllead compounds - Google Patents

Description

Patented June 26, 1951 MANUFACTURE OF ALKYLLEAD COMPOUNDS George Calingaert, Geneva,

N. Y., and Hymin Shapiro, Detroit, Mich, assignors to Ethyl Corporation, New York, N

Delaware Y., a corporation of No Drawing. Application July 27, 1950, Serial No. 176,251

This invention relates to a new process for making alkyllead and aryllead compounds.

The most important of the alkyllead compounds is tetraethyllead which is made commercially by reacting monosodium-lead alloy with ethyl chloride in accordance with the following equation This process has been successful but it has certain disadvantages among which are the 11609"- sity of forming a sodium-lead alloy and the inherent limitations in yield since three-fourths of the lead is not utilized in the reaction. The unused lead must be recovered and re-alloyed with the sodium. The usual yield of tetraethyllead is about 22 weight per cent based on the lead.

One object of our invention is to provide a process for increasing the yield of tetraethyllead obtained in the present process. Another object is to provide a process using free lead, thus avoiding the expensive alloying operation.

The above objects are accomplished by reacting an alkylating or arylating agent with lead and an aryl or alkyl lithium compound. Our reaction can be generalized by the following equation:

where R is an alkyl or aryl radical and X is an inorganic acid radical which forms a salt with the lithium.

It should be noted that the theoretical yield of the alkyllead compound based on the lead is four times that of the present commercial process.

Any of the alkylating agents heretofore used.

or described in the prior art can be used, among which are the alkyl and aryl halides preferably the iodides, bromides and chlorides, the dialkyl sfilfates and the trialkyl phosphates. In general, t e alkylating and arylating agents are esters of inorganic acids having the proper alkyl groups for making the desired alkyllead compound, and having an inorganic acid group which forms a salt with the lithium. Among those which can be used in our invention are the ethyl, propyl, butyl and phenyl chlorides, as well as the corresponding bromides and iodides, diethylsulfate and triethylphosphate.

Catalysts, while not essential to our invention, do improve the yields. The preferred catalysts are the dialkyl ethers such as dimethyl, diethyl, and diisopropyl ethers. Also catalysts of the amine type such as trimethylamine, diethylamine and triethylammonium iodide can be used.

5 Claims. (Cl. 260-437) While tetraethyllead is the principal compound discussed herein because of its large commercial use, other alkyllead compounds such as tetramethyllead, tetrapropyllead, dimethyldiethyllead, methyltriethyllead, tetraphenyllead, diethyldiphenyllead can be made by the process of our invention.

Various alkyl or aryl lithiums can be used depending on the lead alkyl desired such as the methyl, ethyl, propyl, butyl and phenyl lithium. If the alkyl group attached to lithium is different than the one attached to the alkylating agent, a mixture of alkyllead compounds usually results.

For best results a slight stoichiometric excess of the alkyl lithium should be used although lesser amounts give proportionate yields and will result in an increase in yield when used concurrently with the present process.

The temperature employed is not important, the preferable range being 50 and C. The pressure used is not critical but should be sufficient at the temperature employed to maintain the alkylating agent in the liquid phase. The time of reaction is between about 30 minutes and 5 hours. The amount of alkylating agent employed is not critical but an excess over the stoichiometric amount required in the above general equation is preferred.

Our process can be used concurrently to improve the yield of the present commercial process or it can be used independently in treating the unreacted lead from the present process or other forms of free lead. By concurrently is meant either adding the alkyllithium along with the other reactants to the present process or first conducting the reaction of the present process and then adding the alkyllithium together with additional alkylating agent, if required. Such an overall reaction is expressed by the following illustrative equation:

Also, in place of sodium other metals, generally the alkali earth and alkali metals, well known for this purpose, can be alloyed with the lead and used in the above reaction among which are potassium and calcium.

Our invention can best be understood by referring to the following typical working examples in which all the parts and percentages are by weight.

Example I Two-stage reaction using sodium-lead alloy and ethyl chloride: A charge of 100 parts of NaPb alloy is added to a reaction vessel, equipped with an agitator, a jacket for circulation of heating or cooling liquids, a reflux condenser, charging and discharging ports, liquid feed lines, and means for releasing the pressure. Liquid ethyl chloride in the amount of 112 parts is added under pressure to the stirred solids in the vessel over a period of one-half hour. By controlling the flow of liquid in the autoclave jacket and in the reflux condenser the temperature of the reaction mass is permitted to rise from an initial temperature of 50 C. to a temperature of 70 C. during this feed period. The pressure in the autoclave during this feed rises to 75 pounds per square inch gauge where it is maintained. The temperature of the stirred reaction mixture is maintained at 70 C. for an additional 15 minutes maintaining the 75 pound pressure. For the second stage, an additional quantity of 56 parts of ethyl chloride which has been premixed with 19.1 parts of ethyl lithium, is added uniformly. under pressure as a slurry to the autoclave over a period of 15 minutes, again maintaining the 75 pounds pressure. The temperature of the stirred reaction mass is maintained at 70 C., while maintaining 75 pounds pressure, for an additional 85 minutes. At the end of this period the pressure in the autoclave is reduced to atmosperic by venting for a 15 minute period at 70 C. Nitrogen is passed over the reaction mass while the autoclave is open to the atmosphere. The mass is then cooled to 45 C. over an additional 30 minute period while flushing with a stream of nitrogen. The reaction mass is then discharged slowly to a steam-still containing 250 parts of water. With 100-steam fed to the jacket of the steam-still, 1a forecut of ethyl chloride is taken, up to a, vapor temperature of 70 C. At this point the steam jets are then turned on, and with the jacket steam off, the tetraethyllead is distilled for one and one-half hours after the first drop of tetraethyllead appears in the distillation receiver. The yield of product is 92.9 parts, or a yield of 66.2 per cent based on the lead present in the sodium-lead alloy.

Example H In an operation similar to Example 1 above, in the second stage the additional ethyl chloride was added along with 21.7 parts of ethyl lithium and 70 parts of diethyl ether. The product was recovered as in the foregoing example. The amount of alkyllead produced in the two stages of this operation was 119.5 parts or 85 per cent based on the lead present in the sodium-lead alloy employed in the first stage.

4 Example III In the same equipment described in Example I, parts of lead recovered from an operation similar to that described as the first stage of Example I was treated with 198 parts of ethyl chloride premixed with 37.5 parts of ethyl lithium and 117 parts of diethyl ether. The reaction was conducted. in the same manner as in the second stage of Example I. The product obtained in this reaction was 139.5 parts of alkyllead, corresponding to a yield of 89.5 per cent based upon the lead charged to the reactor.

Thus, a fourfold increase in yield over that obtained in the present commercial process is made byour process.

Other embodiments of this invention can be made without departing from the spirit and scope of our invention which is not limited to specific embodiments given herein.

We claim:

1. A process for making hydrocarbon-lead compounds comprising reacting lead with a reagent selected from the class consisting of arylating and alkylating agents which include the hydrocarbon radical in question and have a negative radical which reacts with lithium, and with a hydrocarbon-lithium compound in which the hydrocarbon radical is selected from the group consisting of alkyl or aryl.

2. A dual process for making tetraethyllead which comprises reacting a sodium lead alloy with ethyl chloride, and reacting the free lead so-produced with ethyl chloride in the presence of ethyl lithium and diethyl ether.

3., The process of claim 1 in which the hydrocarbon-lithium compound is an alkyl lithium.

4. The process of claim 1 for making tetraethyllead in which the alkylating agent is an ethylating agent and the hydrocarbon lithium compound is ethyl lithium.

5. The process of claim 1 for making tetraethyllead in which the alkylating agent is ethyl chloride, the hydrocarbon lithium compound is ethyl lithium, and further the process is conducted in the presence of ethyl ether as a catalyst.

GEORGE CALINGAERT. HYMIN SHAPIRO.

Name Date Groll Dec. 5, 1933 Number

Claims (1)

1. A PROCESS FOR MAKING HYDROCARBON-LEAD COMPOUNDS COMPRISING REACTING LEAD WITH A REAGENT SELECTED FROM THE CLASS CONSISTING OF ARYLATING AND ALKYLATING AGENTS WHICH INCLUDE THE HYDROCARBON RADICAL IN QUESTION AND HAVE A NEGATIVE RADICAL WHICH REACTS WITH LITHIUM, AND WITH A HYDROCARBON-LITHIUM COMPOUND IN WHICH THE HYDROCARBON RADICAL IS SELECTED FROM THE GROUP CONSISTING OF ALKYL OR ARYL.