DE1240082B - Process for the electrolytic production of tin or lead alkylene on a depletion cathode - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

C07f

German class: 12 ο - 26/03

Number: 1240 082

File number: P 30669IV b / 12 ο

Filing date: November 29, 1962

Open date: May 11, 1967

Electrolytic syntheses of organic metal compounds on spent cathodes are already known. So z. B. after Ber., 44, p. 327 (1911), tetraisopropyl lead by electrolysis of an aqueous, acidic acetone solution on a lead cathode in the absence of air. Such a procedure however, it is not generally applicable and for the production of organic lead compounds due to low yields and side reactions impractical. In 1925 Calingnert and M e a d the formation of tetraalkyl lead on a lead cathode by electrolysis of a catholyte, which consists of an alkyl halide either in alcoholic alkali (U.S. Patent 1539 297) or in aqueous, Casein containing alkali (U.S. Patent 1,567,159). With this procedure is however, a potential source of hydrogen is necessary and the lead-related yield cannot higher than 50% of the lead consumed. It is actually often below that, and that Cathode will soon be unusable. Furthermore, the alkylating agent is easily destroyed by side reactions.

It is also known for the production of tetraalkylene lead To implement lead-alkali metal alloys with alkyl halides or alkyl sulfates. With these However, based on the lead, only a maximum of 25% yield is possible. When performing In this process, it is necessary to recover and recover large quantities of lead to restore the alloy used for the reaction. In addition, the procedure must be accurate monitored so that the required occupational safety is guaranteed.

The known anodic processes also have numerous disadvantages. The source of the organic The group of the compound to be established is inevitably another organic metal compound (often a complex of two or more such compounds).

Such materials are usually difficult or expensive to manufacture and require special equipment Storage and handling under an inert atmosphere.

So is for the production of alkyl-lead compound fertilizers known to electrolyze a Grignard compound in a practically inert organic solvent, what must take place in an inert atmosphere. Other major disadvantages of this Process are the long reaction times that hinder industrial application of the process.

Process for the electrolytic production of
Tin or lead tetraalkylene on a consumable cathode

Applicant:

E. I. du Pont de Nemours and Company,

Wilmington, Del. (V. St. A.)

Representative:

Dr. W. Schalk, Dipl.-Ing. P. Wirth,

Dipl.-Ing. G. E. M. Dannenberg

and Dr. V. Schmied-Kowarzik, patent attorneys,

Frankfurt / M., Große Eschenheimer Str. 39

Named as inventor:

Ernest Frank Silversmith,

Walter John Sloan, Wilmington, Del. (V. St. A.)

Claimed priority:

V. St. ν. America November 30, 1961
(156128)

It is also known for the production of tetraalkylene lead to electrolyze aluminum triethyl. Even this process has serious disadvantages since the starting materials are oxygen-sensitive and self-igniting Represent compounds that are also made hydride-free in an additional treatment stage Need to become. Here too, the course of the reaction must be carefully monitored.

The aim of the present invention is to provide an improved method for electrolytic Manufacture of tetraalkyl lead or tetraalkyl tin compounds from relatively inexpensive and readily available Starting materials, with the use of organic metal compounds as the main alkylating agent is avoided. Furthermore, according to the invention, an improved method for electrolytic Alkylation, in particular of lead, created, the electrode material and alkylating agent be used more effectively and the anti-knock tetraalkyl lead compounds in obtained better yields than in the previously proposed methods of electrolytic reduction will.

The inventive method for the electrolytic production of tin or lead tetraalkylene

709 579/457

on a consumable cathode is characterized in that an alkyl chloride, bromide, iodide or sulfate with a maximum of 10 carbon atoms per alkyl radical is used as the catholyte alkylating agent, one of the solvents methylene dichloride, ethylrhodanide, acetonitrile, ethylene glycol dimethyl ether or excess alkylating agent is used as the catholyte medium optionally the catholyte an alkali or alkaline earth metal halide or an onium salt of the general formula G _n QY, in which G is a hydrocarbon radical, Q is a nitrogen, phosphorus or sulfur atom, Y is a salt-forming anion and η 3 or 4 and its aqueous solutions have a pH -Value from 5 to 10, adds.

The organic metal compound is obtained from the catholyte in the usual way, with properties and treatment of the organic metal compounds are known. The procedure is easy and economical to carry out and can be carried out at relatively low voltages and Current densities and at room temperature and ordinary pressure.

Suitable devices and methods are in "Technique of Organic Chemistry", Vol. II, 2nd edition (1956), p. 385 ff. (Edited by A. Weis b erger). Carrying out the procedure takes place preferably in an electrolytic cell, in which the catholyte by an electrical Current permeable membrane is separated from the anolyte. Suitable devices of this type are in the aforementioned reference and in U.S. Patents 1539 297, 1567159 and 2985 568. However, the membrane can also be omitted.

The anode can be made from any desired electrode material be made, which is selected with regard to the composition of the anolyte. In contrast to the catholyte, the anolyte can optionally contain hydroxyl groups, provided that that it has the necessary conductivity for electrical current.

The alkylating agent is an alkyl chloride, bromide, iodide and / or sulfate having 1 to 10 carbon atoms in the alkyl radical. The alkyl radical can have carbocyclic substituents such as cycloaliphatic and aromatic groups. The chain length of the remainder does not seem to be feasible to be decisive; it preferably has fewer than 6 carbon atoms and is preferably a methyl or ethyl group.

Optionally, mixtures of two or more such alkylating agents can also be used those in which the alkyl radical is different can be used to denote mixed organometallic To create compounds with two or more different hydrocarbon radicals in the molecule, and mixtures of organic metal compounds, in the latter case at least one tetraalkyl lead compound from which catholyte is obtained.

In a preferred embodiment of the present invention, to increase the conductivity, the catholyte contains one or more onium salts of the formula G _n QY, in which G _n Q stands for an onium cation, where Q is a nitrogen, phosphorus or sulfur atom, η 3 or 4, G is a hydrocarbon radical (preferably with 1 to 10, preferably with 1 to 2 carbon atoms), of which at least one is an alkylating hydrocarbon radical which should correspond to the alkyl radical as defined above, and Y is a salt-forming anion, where the aqueous solutions of which have a pH between 5 and 10. The anion Y is preferably a chloride, bromide, iodide or sulfate ion. These onium salts also act as alkylating agents to a minor extent. Because of the greater reactivity of the above esters, therefore, the organic metal compounds produced usually contain the alkyl radical from the ester to a predominant extent and little or no alkylating radical from the onium salt.

The onium salts mentioned are known compounds. You cannot do this in situ either hydroxyl-containing catholyte solvents are formed, e.g. B. by implementing ethyl iodide with diethyl sulfide or triethylamine.

In solution in the catholyte, such onium salts can regress and are in equilibrium with stand by the ester.

The esters are the actual alkylating agents, as they are particularly important in terms of power utilization are particularly effective and economical and usually have high yields of the desired compounds supply, while the onium salts thus mainly act as conductors. With another preferred embodiment of the present invention is the ester in conjunction with a catholyte-soluble, current-carrying alkali or alkaline earth halide used. Combinations can also be used can be used from two or more of the conductive connections.

However, it is not necessary to maintain strictly anhydrous conditions in the catholyte and the Keep the atmosphere completely away from the cell or the cathode. The alkylating agent can itself Be catholyte medium.

The catholyte used in the process according to the invention should have an electrical conductivity of generally at least about 0.0005 ohm " ¹ cm" ¹ , preferably 0.005 to 0.05 ohm " ¹ .

In general, the solvent is the major component of the catholyte. The alkylating agent is will usually be present in proportions of at least 0.01 moles per kilogram of total catholyte about 0.01 to 8.7 mol and preferably about 0.25 to 5 mol is used. It will be in combination with an onium salt used, a concentration of about 0.1 to 8.7 Mol per Kilogram of solution, preferably at least about 1 mole, is used. The conductive connection can in proportions of 0.001 to about 2 mol per kilogram of catholyte, preferably about 0.05 to 0.5 mol or 0.1 to 0.5 moles can be used. The upper limit for the conductor also depends on his Solubility in the catholyte.

In general, the desired conversion of the alkylating agent appears to require about 1 to 2 volts. In some approaches, the minimum total voltage required for current to flow through the cell was about 4 to 5 volts. With normal devices and most catholytes, the application of more than about 15 volts is seldom necessary. The current density can be between 0.0001 to about lAmp./cm ² cathode area is maintained but preferably to 0.01 to 0,4Amp. / Cm ^2. The lower limit of the current density is determined by the desired production speed

the organic metal compound determined. Usually the current density is about 0.1 to 0.4 amps / cm ² .

The procedure is usually carried out at normal room temperature and atmospheric pressure. the However, working temperatures can be higher or lower. Temperatures of used around 20 to 70 ° C. The pressure should be at least to maintain a liquid catholyte sufficient and can be below or above atmospheric pressure. Also reflux conditions can be applied. Where the materials used or the organic ones made If metal compounds are sensitive, an inert atmosphere can also be used.

In the following examples, the process is carried out in batches. The implementation can however also take place continuously. In particular, the tetraalkyl lead appears almost immediately from the start of electrolysis. The conversion is poor for short times, but the yields are poor Electricity and lead high, on the order of 90%. In the continuous process the catholyte containing the product can be continuously removed to recover the organic Treated metal compound and recycled and replaced in whole or in part by fresh catholyte will.

The lead compounds with lower hydrocarbon residues are known as anti-knock agents. The other organic metal compounds are used as catalysts, fungicides and anti-knock agents known.

The following examples illustrate the invention. Unless otherwise stated, all quantities are Parts by weight.

example 1

(A) An electrolytic cell consisting of a lead cathode, a platinum anode and separate catholyte and anolyte compartments was used; the latter were separated by a cation-permeable membrane. The catholyte solution consisted of 29 parts of ethyl bromide, 5 parts of tetraethylammonium bromide and 175 parts of acetonitrile (which corresponded to 1.273 mol of ethyl bromide and 0.114 mol of tetraethyl ammonium bromide per kilogram of solution). The anolyte consisted of 28 parts of sodium carbonate in 250 parts of water. With the electrolytes at room temperature, the direct current was switched on and within 15 minutes the voltage was gradually increased from about 6 to about 15 Volts; the amperage was increased from about 0.2 to about 1 to 1.5 amps, corresponding to a final current density of about 0.02 to 0.03 amps / cm ² . These conditions were maintained for about 4 hours with the temperature increasing to about 60 ° C. The catholyte was removed, decanted from a trace of insoluble material, mixed thoroughly with 800 parts of water and 150 parts of pentane and the resulting system separated from two layers. A further 150 parts of pentane were used for renewed extraction of the aqueous layer and the entire pentane extract was distilled under reduced pressure, whereby tetraethyl lead in 70% yield, based on the current passed through, and in 80% yield, based on the weight loss of the cathode during electrolysis.

The electrolyzed catholyte preparation can also be fractionally distilled to obtain tetraethyl lead or steam distilled.

(B) In the above electrolytic process, but with an anolyte from a solution of 5 parts Tetraethylammonium bromide in 175 parts of acetonitrile, the yield of tetraethyl lead was 77%,

ίο based on electricity, and 81% based on that Lead. During the latter procedure, bromide was oxidized at the anode; the oxidation product was present in the anolyte as polybromide ions; molecular bromine could be derived from this in a known manner be won. Optionally, an agent for removing the anolyte can be added to the initial anolyte oxidizing bromine are added. Such a means can e.g. B. be an olefin, the olefin dibromide forms; or it can be a very basic one

so be anion exchange resin in the halide form, such resins are known to chemically absorb bromine as polybromo halide ions.

(C) Other current conductors can be tetraethylammonium bromide replace in catholyte. Typical examples using according to the procedure of Example 1 (A) The results obtained are:

Conductor

Triphenylmethyl bromide.

Lithium bromide

_3S triethylsulfonium bromide

Sodium iodide

Potassium rhodanide

Lithium perchlorate

Potassium iodide

Triphenylethyl

phosphonium iodide ...

Calcium bromide

Moles / kg
Catholyte

0.094
0.524
0.121
0.159
0.243
0.149

<0.145

0.091

<0.012

Yield to
Tetraethyl lead

in%>,
based on lead

72
100

81

76
100
100

84

86
100

The normally covalent triphenylmethyl bromide apparently underdissociates in acetonitrile the conditions used in ions. Therefore, the conductor does not need a previously formed, as Ions to be present in the solid state salt, but it just needs to make the solution electrically conductive can do.

Example 2

The procedure of Example 1 (A) was repeated with the acetonitrile by an equal volume a solvent listed below was replaced, and wherein the number of moles of ethyl bromide and Tetraethylammonium bromide per kilogram of catholyte according to the changes in the density of the solvent varied.

solvent
65 Moles / kg
(C ₂ H ₅ ) Br Catholyte
(C ₂ Hs) ₄ NBr Yield to
Tetraethyl lead
in ° / o
based
on lead Methylene dichloride
Ethyl rhodanide 0.794
1.031 0.071
0.093 71
84

Example 3

Following the procedure of Example 1 (A) with other ethylating agents, tetraethyl lead was made as follows manufactured:

Ethylating agent Moles / kg
Catholyte Yield of tetra
ethyl lead in »/ o,
based on lead Diethyl sulfate
Ethyl iodide
Ethyl chloride 0.81
4.24
1.51 81
72
93

Example 4

A catholyte of 200 ecm acetonitrile, 2 ecm methyl chloride and 15 g tetraethylammonium bromide [which corresponded to 0.23 mol CH ₃ Cl and 0.41 mol (C ₂ H ₅ ) ₄ NBr per kilogram of catholyte] was electrolyzed according to Example 1 (B) ( ie, the anolyte consisted of 15 g of tetraethylammonium bromide in 200 ecm of acetonitrile). The voltage and current were increased to about 15 volts and 1 to 1.5 amps in about 15 minutes, which corresponded to a current density of about 0.02 to 0.03 amps / cm *. After 4 hours the catholyte was decanted from a trace of sludge and analyzed. The tetraethyl lead content, calculated as tetramethyl lead (the presumably predominant product), corresponded to a 93% yield based on the lead consumed and a 75% yield based on the current.

Example 5

The procedure of Example 1 (A) was repeated. The catholyte consisted of:

171 g acetonitrile (225 ecm),

2.54 g dimethyl sulfide (3 mol / kg catholyte), 45.5 g CH ₃ I (1.44 mol / kg catholyte).

The anolyte consisted of Na ₂ CO ₃ in water.

The yields of tetramethyl lead were 86%, based on lead, and 85%, based on electricity. That Dimethyl sulfide apparently reacts with some methyl iodide to form trimethyl sulfonium iodide as Conductor.

Example 6

Example 1 (A) was repeated with a cathode made of tin instead of lead, with tetraethyltin was obtained in a yield of about 72%, based on the tin (determined by bromine titration of the product).

Example 7

An electrolytic cell consisting of a 100 cc jar with three electrodes and an asbestos fiber bridge. The cathode was made of lead, the anode of platinum, and the reference electrode to determine the reduction potential consisted of an aqueous saturated calomel electrode. This arrangement was made in conjunction with a polarograph and an IR compensator as used by Arthur, among others, in Anal. Chem., 33, pp. 488, 765 (1961) became.

ίο The test composition was a 1,2-dimethoxyethane solution of methyl bromide (about 0.01-0.1N) and tetrabutylammonium bromide (0.1N). The electrolysis was carried out ² 41 minutes at 25 ⁰ C with an applied potential of 1,3VoIt and a current density of 0.05 Amp./cm. Under these conditions the methyl bromide reduction potential was determined to be about 1.1 volts. The other electrolytic components did not exert a reducing effect, that is to say they behaved inertly.

The resulting solution was examined for lead content. From other work with this cell For the electrolytic production of tetramethyl lead, it has been determined that the lead is in the form of tetramethyl lead Template. The yield of tetramethyl lead was practically quantitative.

Claims (2)

Patent claims: 1. A process for the electrolytic production of tin or lead alkylene on a consumable cathode, characterized in that the catholyte alkylating agent used is an alkyl chloride, bromide, iodide or sulfate with a maximum of 10 carbon atoms per alkyl radical, and one of the solvents methylene dichloride, ethylrhodanide as the catholyte medium , Acetonitrile, ethylene glycol dimethyl ether or excess alkylating agent and optionally the catholyte an alkali or alkaline earth metal halide or an onium salt of the general formula G _n QY, in which G is a hydrocarbon radical, Q is a nitrogen, phosphorus or sulfur atom, Y is a salt-forming anion and η 3 or 4 and its aqueous solutions have a pH of 5 to 10, is added. 2. The method according to claim 1, characterized in that one per kilogram of catholyte 0.07 to 0.5 mol onium salt or alkali or alkaline earth metal halide added. Considered publications:
German Auslegeschrift No. 1114 816;
U.S. Patent No. 3,007,858; Düb, Organometallic Compounds, Volume II (1961), Pp. 257/258. 709 579/457 5.67 © Bundesdruckerei Berlin