US3431185A - Hydrocarbon lead production - Google Patents

Description

United States Patent 3,431,185 HYDROCARBON LEAD PRODUCTION Gene C. Robinson, Baton Rouge, La., assignor to Ethyl Corporation, New York, N.Y., a corporation of Virginia No Drawing. Filed June 22, 1964, Ser. No. 377,097 US. Cl. 204-59 2 Claims Int. Cl. Btllir 1/00 ABSTRACT OF THE DISCLOSURE This application relates to a mixture of tetraorganolead compounds and an electrolytic process for the production of the mixture by electrolyzing a liquid composition comprising a vinylic Grignard reagent and an alkyl halide.

The preparation of vinyl lead compounds containing at least one alkyl radical has been disclosed in U.S. Patent 3,071,607, patented Jan. 1, 1963. According to this patent the mixed lead compounds may be produced for example by reacting a vinyl Grignard reagent with the appropriate lead salt. However, such a process has certain disadvantages such as the relatively low yields obtained and the high cost of the required lead salt. It is accordingly an object of this invention to provide an improved process for the production of lead compounds having both vinylic and alkyl radicals attached to the lead. It is a further object of this invention to directly produce an organolead composition suitable for improved antiknock compositions. Another object is to produce organolead compounds having both alkyl and vinylic groups attached to the lead at higher yields and efiiciencies. These and other objects will be apparent in the description which follows.

According to this invention lead compounds having both vinylic and alkyl groups attached to the lead may be produced at high yields and current efficiencies by electrolyzing in an electrolytic cell having a lead anode, a liquid composition comprising a vinylic Grignard reagent (i.e., a vinylic magnesium halide) dissolved in an alkyl halide. By vinylic Grignard is meant compounds of the formula R C=CHMgX wherein R is selected from the group consisting of H, CH CH CH and mixtures thereof and X is a halogen. The alkyl halides have the formula R'Y wherein R is a lower alkyl radical and Y is a halogen. The anode of the electrolytic cell supplies the lead of the organolead product. The cathode may be either lead or another suitable material such as stainless steel.

One of the unexpected advantages of this invention is that a desired distribution of tetraorganolead compounds comprising tetraalkyl lead, trialkylvinylic lead, dialkyldivinyliclead, alkyltrivinylic lead and tetravinylic lead is achieved. Such compositions have been found to be of particular advantage as an antiknock composition in gasoline. Furthermore, by producing these mixed compositions directly, the process of redistributing the organo radicals in a mixture of tetraalkyl lead and tetravinylic lead compounds is avoided.

A further advantage of this invention is that the alkylvinylic compounds are produced in high yields in an eflicient process. It has been found that the lead compounds may be produced at current efiiciencies of greater than 100 percent. Thus considerable saving in current expenditures is realized and a greater throughput per unit time is achieved. These excellent results were particularly surprising because when a composition of vinyl Grignard reagent and vinyl chloride was electrolyzed only a very low yield of organolead compound was produced. The yields may be considerably higher using the process of this invention, wherein a composition comprisng a vinylic Grignard reagent and an alkyl halide is employed, than when a composition of alkyl Grignard and vinylic chloride is employed in the electrolytic cell. The reasons for these considerably improved results are not understood.

It is one of the features of this invention that the liquid composition comprising the vinylic Grignard reagent and the alkyl halide has a high conductivity. It is possible to conduct the reaction in the absence of added electrolytes. By conducting the reaction in the absence of additional electrolytes or solvents the recovery of the organlead product as well as the by-products is facilitated.

The process of this invention may be more completely understood and illustrated -by the following examples. All parts are by weight unless expressed otherwise.

Example I The electrolytic cell used in these tests has a 29 mm. by 200 mm. Pyrex test tube fitted with a stopper having a -inch glass T for charging the electrolyte or for connection to a gas bure'tte fitted with mercury for collecting and measuring gases evolved. When gas was not being collected the side arm of the glass T was connected to a nitrogen bubbler for maintaining an inert atmosphere in the cell. A hypodermic needle through the stopper was connected to a small cylinder for supplying the alkyl halide to the electrolytic solution. Two copper wires for the electrical leads were fitted tightly through holes in the stopper. The cathode was a stainless steel rectangular sheet which was about 2 cm. wide, 10' cm. long and about -inch thick. The cathode was sandwiched between two lead anode sheets of approximately the same size as the cathode. Teflon spacers held the electrodes about 0.5 cm. apart. Electrical direct current (DC) was supplied for the test by a battery charger operating off regular 115 volt AC supply line and voltage control was obtained by a rheostat on the battery charger. The current was measured by an ammeter and by a copper coulometer.

Vinyl magnesium chloride was prepared by the reaction of magnesium and vinyl chloride. Magnesium chips, 121.6 g., were reacted in 1,075 g. of tetrahydrofuran with 396 g. of vinyl chloride. The reaction product was cooled and unreacted vinyl chloride was vented. The product solution, 1300 ml., was decanted and 500 m1. of tetrahydrofuran was added to extract the residue. Most of the residue went into solution, which was then decanted and added to the product solution giving it a total of 1900 m1. Aliquots of this product solution indicated it was 2.64 molar with respect to magnesium and 2.74 molar with respect to chloride ions. The product solution (25 ml. portions equivalent to 67.25 millimols of vinyl magnesium chloride) was used in the electrolyte solution for the electrolysis test.

A mixture of tetravinyl lead, trim-ethylvinyl lead, dimethyldivinyl lead, methyltrivinyl lead, and tetramethyl lead was produced in the electrolytic cell. The vinyl magnesium chloride prepared above in an amount of 67.25 millimols was combined with 10 ml. of dibutyl Carbitol (diethylene glycol dibutyl ether) and 15 ml. of benzene to constitute the electrolytic solution. Methyl chloride, 25 g., was added during electrolysis. The cell was cooled by a flow of tap water around the cell. The run was 2.5 hours long. The initial current Was 200 milliamps and the voltage was maintained at 5.3. During the run the current was allowed to drop to a minimum of milliamps while the voltage was held constant at 5.3. The product contained a total of 1.27 g. of lead present as a mixture of tetraorga-nolead compounds. This product comprised a desired mixture of trimethylvinyl lead, dimethyldivinyl lead and methyltrivinyl lead together with some tetrametyl lead and tetravinyl lead. No triorgano lead compounds were detected. The product was analyzed by the dithizone method of analysis. Only a negligible amount of gas was produced during the run. The current efficiency during the run was 178 percent.

Example II The procedure of Example I is repeated with the exception that ethyl chloride was substituted for the methyl chloride of Example I. A high yield of product comprising triethylvinyl lead, diethyldivinyl lead, and ethyltrivinyl lead, together with a small amount of tetraethyl lead and tetravinyl lead is obtained. In this example negligible gas is produced and the current efficiency is high.

Example III To illustrate the advantage of the instant invention whereby the electrolytic solution comprises a vinylic Grignard reagent and an alkly halide, a comparative run was made wherein vinyl chloride was substituted for the methyl chloride of Example I. The same vinyl magnesium chloride of Example I in an amount of 67.25 millimols was combined with 45 g. of vinyl chloride and 25 ml. of dibutyl Carbitol to form the electrolytic solution. The nominal milliamps were 100 and the nominal voltage was 3 volts. The run was operated for a period of 18 hours, yet only 0.040 g. of organolead compounds were produced. During the run large amounts of gases were evolved.

Example IV To further illustrate the unexpected nature of this invention, Example III was repeated using 67.25 millimols of the vinyl magnesium chloride, 240 g. of vinyl chloride, ml. of dibutyl Carbitol and ml. of benzene. The nominal milliamps were 100 and the voltage was 2.9. During a run of 17 hours only a relatively small amount of organo lead compounds were produced. During this run also large amounts of gases were evolved. When the voltage in this run was gradually increased to 24 while maintaining a current flow of 100 milliamps, no significant improvement in the results were noted.

As pointed out in the examples, when a composition comprising vinyl magnesium halide and vinyl chloride was electrolyzed very low yields of tetraorgano metallic compounds were obtained. It was accordingly surprising that when an alkyl halide such as methyl chloride was substituted for vinyl chloride that high yields of the various tetraorgano lead compounds were produced.

The alkylvinylic lead compositions produced according to the present process comprise, in general, organolead compounds having between 1 to 3 vinylic groups attached directly to lead and the remaining valences of the lead are satisfied by alkyl radicals. Generally the alkyl radicals will contain from 1 to 8 carbon atoms, with the alkyl radicals having one or two carbon atoms being particularly preferred. The alkyl or vinyl groups may be the same or different. The examples of compounds that may be produced according to this invention are trimethylvinyl lead, dimethyldivinyl lead, methyltrivinyl lead, triethylvinyl lead, diethyldivinyl lead, ethyltrivinyl lead, methylethyldivinyl lead, methyldiethylvinyl lead, di-nbutyldivinyl lead, n-hexyltrivinyl lead, Z-ethylhexyltrivinyl lead, dimethylethylvinyl lead, dimethyldipropenyl lead, dimethyldibutenyl lead, methyltriisobutenyl lead, isopropyltrivinyl lead, methyldivinylpropenyl lead, mixtures thereof and the like.

Particularly preferred compositions produced are those containing the mixed organo lead compositions such as one containing tetraalkyl lead, trialkylvinyl lead, dialkyldivinyl lead, alkyltrivinyl lead, and tetravinyl lead, wherein the alkyl groups contain from one to three carbon atoms. Such compositions may be produced directly by the process of this invention. These compositions possess unique characteristics such as for antiknock compositions, and it is an important feature of this invention that these compositions may be produced directly without the necessity of redistributing a combination of tetravinyl lead and tetraalkyl lead. A predominately alkylvinylic lead composition may be produced.

One method for producing mixed lead compounds wherein the alkyl groups are different is to utilize a combination of alkyl halides, such as combination of methyl chloride and ethyl chloride. The methyl chloride and ethyl chloride are then combined with the vinylic Grignard reagent to form the electrolytic composition. The mixture of alkyl halides may be present in any combination and more than two alkyl halides may also be employed.

The vinylic Grignard agent of the formula R C CHMgX may be produced in conventional manner. Generally the halogen of the Grignard reagent as well as for the alkyl halide will be selected from the group consisting of chlorine, bromine, iodine and mixtures thereof. Preferred halogens are chlorine and bromine with chlorine being particularly preferred.

The ratio of the alkyl halide to the vinylic magnesium halide present in the electrolyte may be varied somewhat but generally will be in the ratio of 0.1 to 10 mols of alkyl halide per mol of vinylic magnesium halide. A preferred ratio of alkyl halide to vinylic magnesium halide is between 0.75 and 2.0 mols of alkyl halide per mol of vinylic magnestium halide. The process may be operated as a batch process or may be operated continuously. All of the vinylic magnesium halide and alkyl halide may be added initially or either of these may be added continuously or intermittently throughout the reaction. Of course, in a continuous operation the electrolyzed composition may be continuously or intermittently removed from the cell. Similarly, additional or new lead anodes may be added as required.

The cell employed may be of conventional design with one or more electrodes and cathodes. Provision should be made for the release of any gases evolved during the reaction. Also the cell should be suitable for operating under the pressure generated by the particular reactants at the temperature of reaction. Suitably the electrolytic solution will be anhydrous.

The temperature during electroylsis is not critical. It should be sufiiciently high to give reasonable reaction rates but should not be above the decomposition temperature of the organometallic reactants or the organolead products. Thus, the operating temperature of the reaction depends upon the particular organometallic compounds involved. In general, suitable temperatures are between about 30 C. and about 130 C., but temperatures from about 15 to C. are preferred to facilitate heat removal, for maximum current efficiency and for best results. Higher temperatures can be employed when using organolead thermal stabilizers. In some instances considerable exothermic heat is generated and consequently a cooling medium may be desired to control the temperature.

About atmospheric pressure is normally employed, although subatmospheric pressures are permissible. In some instances, supraatmospheric pressure is preferred, particularly when employing a relatively high temperature and a relatively volatile solvent or electrolyte. Also, a pressure of inert gas is sometimes desirable, for example to assure anhydrous conditions. The pressure will generally be from about 0 to 500 p.s.i. with the range of about atmospheric (STP) to 259 p.s.i.g. being particularly suitable In some instances various solvents can be employed during the electrolysis step. The solvent should desirably dissolve the vinylic Grignard reagent and the alkyl halide and preferably will be inert to reaction with the organolead product. The use of a solvent however is not essential to the operation of the process and its absence may be desirable in some instances. Thus when electrolyzing the electrolyte in the absence of a solvent, the organo lead compound is generally insoluble and separates as a distinct phase which can easily be recovered. When a solvent is employed, it is not necessary that the organo lead product be soluble in the solvent. When the organo lead product is insoluble in the solvent system, it can be recovered directly from the cell as a separate phase. In this case it is generally desirable to Withdraw a part, of the solvent-containing electrolyte, either continuously or periodically, to use as a solvent for the fresh electrolyte feed. In general, solvents suitalble are the ethers and polyethers (including cyclic ethers), tertiary amines, other organometallics, amides and substituted amides, and hydrocarbons, particularly the aro matic hydrocarbons. Typical examples of suitable solvents are illustrated in the above examples. Similar results are obtained when these examples are repeated with triisopropyl amine, toluene, xylene, and the like. Additional typical examples of suitable solvents are dialkylamides such as diethylamide and ethers, such as dimethyl ether, methylethyl ether, methyl-n-propyl ether, and mixtures of these. Suitable polyethers are ethylene glycol diethers, such as methylethyl, diethyl, ethyl'butyl, and dibutyl; diethylene glycol ethers, such as dimethyl, diethyl, ethylbutyl and butyl lauryl; trimetylene glycol ethers, such as dimethyl, methylethyl; glycerol ethers, such as trimethyl, diethyl methyl, etc.; and cyclic ethers, such as dioxane and tetrahydrofiuran. Typical amines suitable for this invention include aliphatic and aromatic amines and heterocyclic nitrogen compounds. The preferred tertiary amines for use in this invention are trimethyl amine, dimethyl ethyl amine, tetra/methyl ethylene diamine and n-methyl morpholine. Primary and secondary amines can also he used, such as methyl amine, dimethyl amine, etc.

The lead anode can be pure lead or alloys thereof of varying shapes. Typical examples of alloy metals are tin, bismuth, cadmium, antimony and copper. In some cases sodium, lithium, magnesium, and zinc are suitable. Likewise the lead or lead alloys can be coated or impregnated on a conductive metal, either metallic or non-metallic, such as graphite. The cathode can be any suitable conductive metal but is preferably one which does not alloy with the metal produced.

The voltage and amperage necessary for the reaction depend upon the particular organo lead compound being formed, as well as upon the specific resistance of the cell. In general, the potential across the electrodes should be between about 0.5 and 50 volts, although not greater than volts is normally required or desirable. Preferably, a potential of 1-1 5 volts is employed. In general, not greater than 0.25 ampere/ sq. cm. is employed. A preferred range is between 0.002 to 0.1 ampere/ sq. cm.

Alkyl vinylic lead compounds may also be produced by electrolyzing a composition comprising alkyl magnesium halides and a vinylic halide. This subject matter is not being claimed herein but rather is the subject of impending application filed on even date. However, it is one of the unexpected features of the instant invention that improved results may he obtained by the electrolysis of the composi- Cit tion comprising vinylic magnesium halide and alkyl halide over that obtained by the electrolysis of alkyl magnesium halide and a vinylic halide. Superior yields of the desired product and higher current efiiciencies result from the process of the instant invention. Again the reason for such an improvement by the process of this invention is not understood.

The products of this invention possess considerable utility. These compositions are soluble in hydrocarbons and are valuable as antiknock compositions for gasolines. The compositions containing the distributed isomers are of particular value. As has been shown this composition may be produced directly by the process of this invention. The products may also be used as monomers in the production of polymers, e.g., for the production of copolymers with other vinyl compounds.

Other embodiments of this invention can be made without departing from the spirit and scope of this invention which is not limited to the specific embodiments given herein. For example, tetravinylic lead compounds may be produced by separating the product of the electrolysis of the vinylic magnesium halide and the alkyl halide.

What is claimed is:

1. An electrolytic process for the production of a mixture of tetraorganolead compounds consisting essentially of a predominant amount of trialkylvinylic lead, dialkyldivinylic lead and alkyltrivinylic lead and small amounts of tetravinylic lead and tetraalkyl lead which comprises electrolyzing in an electrolytic cell having a sacrificial lead anode a liquid composition comprising a vinylic Grignard reagent and an alkyl halide, said liquid composition initially having a mol ratio of alkyl halide to vinylic Grignard reagent of from about 0.1 to about 10, said vinylic Grignard reagent being at least one compound represented by the formula R C=CHMgX wherein R is at least one radical selected from the group consisting of H1 CH -CH CH and mixtures thereof and X is a halogen, and said alkyl halide being at least one compound represented by the formula RY wherein R is an alkyl radical selected from the group consisting of alkyl radicals having from 1 to about 8 carbon atoms and Y is a halogen.

2. The process of claim 1 further characterized by said liquid composition comprising a solvent for said alkyl halide and said vinylic Grignard reagent.

References Cited UNITED STATES PATENTS 3,298,939 1/1967 Linsk 204-59 2,535,193 12/1950 Calingaert et al. 260-437 3,155,602 11/1964 Linsk et al. 204-59 3,156,716 11/1964 Ramsden et al 260-437 HOWARD S. WILLIAMS, Primary Examiner.