US3649482A - Cathodic process for the preparation of tetraalkyl lead compounds - Google Patents

Cathodic process for the preparation of tetraalkyl lead compounds Download PDF

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US3649482A
US3649482A US863096A US3649482DA US3649482A US 3649482 A US3649482 A US 3649482A US 863096 A US863096 A US 863096A US 3649482D A US3649482D A US 3649482DA US 3649482 A US3649482 A US 3649482A
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lead
water
tel
cathode
alkyl
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Kang Yang
James D Reedy
Morris A Johnson
William H Harwood
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ConocoPhillips Co
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Continental Oil Co
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B3/00—Electrolytic production of organic compounds
    • C25B3/01—Products
    • C25B3/13—Organo-metallic compounds

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  • This invention relates to a process for producing tetraalkyl lead compounds and more particularly to an electrolytic process wherein an alkyl halide or mixture of alkyl halides is reduced at a lead cathode to form tetraalkyl lead compounds.
  • Calingaert and Mead disclosed tetraalkyl lead formation at a lead cathode by electrolyzing a catholyte consisting of an alkyl iodide in either alcoholic caustic (Calingaert in US. Pat. No. 1,539,297) or aqueous caustic containing casein (Mead in US. Pat. No. 1,567,159). Also, Silversmith et al.
  • Electrolytic processes for the production of tetraalkyl lead compounds employing a lead cathode can be classi fied on the basis of the major solvent employed in the catholyte. This classification is as follows:
  • aprotic solvent is lower conducting than aqueous systems
  • materials needed for cell construction, particularly the cell membrane which separates the anolyte from the catholyte are less stable in aprotic solvents than in aqueous systems
  • halogens, generated at the anode tend to react the most aprotic solvents
  • aprotic solvents are more expensive than water.
  • a small amount of water has been added to an aprotic solvent to suppress side reactions; however, where the major solvent component is an aprotic solvent, these shortcomings cannot be remedied as long as the water remains a minor component.
  • water can be used as a catholyte solvent in an electrolytic process for the production of tetraalkyl lead compounds provided certain current carrying salts and certain solubilizing agents are included in the catholyte.
  • tetrabutyl ammonium bromide or tetrabutyl phosphonium bromide is used as a current carrier and acetone or a water soluble ether such as tetrahydrofuran is used as a solubilizing agent for the cathodic reduction to form tetraalkyl lead from a lead cathode and alkyl bromide
  • acetone or a water soluble ether such as tetrahydrofuran
  • anolyte is water with a current carrier therein, and it is therefore a simple matter to remove the bromine from the anolyte by distillation or other conventional means which are well known in the art.
  • suitable current carriers for the anolyte are NH Br, (NH CO NaBr, Na CO MgBr, (C H NBr, and a mixture of BrC H Br or C H Br and (C H NBr.
  • FIG. 1 is a graph showing the effect of the ratio of water and current carrier on the production of alkyl lead compounds. This FIG. 1 is related to Example 5.
  • FIG. 2 is a graph showing the effect of acetone concentration on the production of alkyl lead compounds. This FIG. 2 is related to Example 6.
  • EXAMPLE 1 A Pyrex cell was divided into cathode and anode compartments by using an anion exchange membrane.
  • the catholyte had the following composition:
  • Electrolysis was carried out as described in Example 1 for 3.0 hours at 150 ma.
  • Electrolysis was carried out as described in Example 1 for three hours at 150 ma.
  • EXAMPLE 5 This example shows the dependence of TEL on a concentration ratio, [water]/[(C H NBr].
  • Anolyte was g. of BrC H Br together with 16 weight percent J Qh in water.
  • Other electrolytic conditions are given in FIG. 1.
  • EXAMPLE 6 This example shows the effect of an addition of a solubilizer on TEL yield.
  • the anolyte composition was the same as in Example 5.
  • the cathodic conditions are given in FIG. 2.
  • Catholyte composition was: 14 g. of ethylbromide, and 60 g. of a solution having a composition of 10 g.
  • Catholyte composition was: 50 g. water, 10 g. C H CN, 3.60 g. (C H NBr, and 14 g. of C H Br.
  • Anolyte composition same as Example 7.
  • Example 6 the addition of some acetone in the catholyte greatly improves the TEL yields.
  • the electrochemical reduction of aqueous ketone at the lead cathode produces lead containing products which are not tetraalkyl leads.
  • the fact that we obtained nearly quantitative yields of TEL in the presence of acetone is contrary to this teaching and hence entirely unexpected.
  • the second advantage in the present process is that the catholyte is high conducting and hence power consumption is low.
  • both water and alkylating agent solubilizer are so cheap that appreciable decomposition of these compounds at the cathode, which may occur at some high current density, is not a serious problem. This is certainly not so in the system using aprotic solvents.
  • ethyl bromide concentration of ethyl bromide can be varied widely. In one extreme (Example 9), pure alkyl bromide together with the salts gave a reasonably good yield of TEL; while in the other extreme (Example 6), a small amount of ethyl bromide without any solubilizer is enough to give a decent yield of TEL. This is shown in the following example.
  • EXAMPLE 9 The catholyte composition was: 0.551 mole of C H Br and 0.0236 mole of (C H PBr. Electrolysis was carried out with cation membrane at 50 ma. for 1 hour, at 62 ma. for 1 hour and at 70 ma. for 2 hours.
  • concentration of the alkylating agent can be varied widely as shown above, it is preferable to use water and solubilizer to reduce power cost and to improve alkyl lead yields.
  • solubilizer is also important in the present invention.
  • Acetone and tetrahydrofuran can be employed with a good result as shown in previous examples, but ethyl alcohol is quite unsatisfactory, as shown below.
  • Example 10 The composition of catholyte was:
  • Example 11 The composition of catholyte was:
  • Electrolysis was carried out as described in Example 1 at 150 ma. for 2.0 hours. There was appreciable gas formation at the cathode, and TEL yield was very low as indicated below:
  • Example 12 The composition of catholyte was:
  • Electrolysis was carried out for 1.43 hours at 100 ma. using a cation exchange membrane.
  • the present process can also produce TML, T P (propyl)L, and Methyl-Ethyl Mixed Lead. These are demonstrated in the following examples.
  • Example 13 An H-type cell was divided into cathode and anode compartment by an anion exchange membrane.
  • the cathodelyte composition was: 4.5 g. of (C H NBr, 41.5 g. of water, 13 g. CH COCH and 2004 cc. at 760 mm. (room temperature) of CH Br.
  • the anodelyte composition was 8.0 g. (NH CO in 100 g. water.
  • the cathode was a lead sheet with an effect surface area of about 3 cm. and the anode was a carbon rod.
  • Example 14 The cathode compartment contained 20 g. tetrabutylammonium bromide, 100 g. acetone, and 210 g. water.
  • the anode compartment contained 36 g. ammonium carbonate dissolved in 450 ml. water.
  • the anode was a carbon rod and the cathode was a lead sheet about 8 cm. which was prepared and weighed before and after each reaction. The contents of both half-cells were vigorously stirred with magnetic stirrers.
  • the cathode was degassed first with argon, then with methyl bromide.
  • the solution was electrolyzed for about 7 hours at 1 amp with slow bubbling of methylbromide through the cathode.
  • Lead loss at the end of this elec trolysis was 13.30 g.
  • the organic layer was separated, washed with three 125 ml. portions of water. Yield, 10.60 g. product after separation, drying over sodium sulfate, and filtration. Gas chromatography showed only a trace of methyl bromide, 99+% TML. No other components were detected. This product was used in the preparation of motor mix for antiknock rating.
  • Example 15 The cathodelyte composition used in the preparation of TPL (tetrapropyl lead) was: 15.0 g. of C3HqBr (normal), and 75 cc. of a polution containing g. water, 10 g. (C H NBr, and 40 g, acetone.
  • the anolyte composition was: 10 g. of BrC H Br and 70 g. of a solution containing 210 g. water and 40 g. (C H NB.
  • the cathode was a lead bar with an effective area of 5.26 cm.
  • the electrolysis was carried out at 600 ma. to give a total current of 7.46X10 (4 96500) coulombs.
  • the product was extracted with n-hexane and was analyzed chromatographically.
  • the major side product was (C3H7)3PbPb(C3H7)3.
  • Example 16 Mixed lead was prepared under the following conditions:
  • Cathode 14 g. C H Br, 0.665 g. CH Br, and 75 cc. of a solution having a composition of 10 g. (C H NBr, 100 g. H 0 and 35 g. CH COCH
  • Anode 10 g, BrC H Br and 70 g. of a solution having a composition of 40 g. (C H NBr and 210 g. H O.
  • the cathode compartment contained 20 g. tetrabutylammonium bromide, 100 g. acetone, and 210 g. water.
  • the anode compartment contained 36 g. ammonium carbonate dissolved in 450 ml. water.
  • the anode was a carbon rod and the cathode was a lead sheet about 8 cm. which was prepared and weighed before and after each reaction.
  • the cathode compartment contained 20 g. tetrabutylammonium bromide, 100 g. acetone, and 210 g. water.
  • the anode compartment contained 36 g. ammonium carbonate dissolved in 450 ml. water.
  • the anode was a carbon rod and the cathode was a lead sheet about 8 cm. which was prepared and weighed before and after each reaction.
  • ethylbromide To the cathode compartment was added 30 g. ethylbromide. The cathode solution was degassed first with argon, then with methylbromide. The solution was electrolyzed at a pressure of about p.s.i. methylbromide and about 1 amp for several hours. After electrolysis, the organic layer in the cathode compartment was separated, Washed well with water, dried over sodium sulfate, and evacuated on a rotary evaporator at ambient temperature for a few minutes. Gas chromatography indicated the product was 98 percent TEL, about 1 percent methyltriethyl lead (PbMeEt and only a trace of TML. Lead loss was 9.63 g.
  • Suitable membrane materials are porous porcelain, asbestos, glass fiber paper, cellulosic substances such as porous cellophane and parchment, films of agar gel, and ion exchange resins.
  • alkyl bromide can be employed in a water solvent system with or without an addition of a solubilizer.
  • a solubilizer To be commercially successful, one must recover bromine generated at the anode almost quantitatively; in this connection, our system is ideally suited.
  • the leakage of (C H P+ or (C H N+ to the anode should be very small, and bromine loss due to the reaction with these ions becomes very low. Even if some leakage did occur, bromine can be recovered readily by reacting the complex between Br and the leaked salt with ethylene. Resulting dibromoethane can be used in the motor mix.
  • solubilizer In our invention a proper choice of solubilizer is of prime importance. Acetone and tetrahydrofuran work very well, but alcohol is quite unsatisfactory. As far as we know, existing literature or patents do not contain experimental data indicating that in the electrochemical reductions of alkyl halides in water solvent, acetone and tetrahydrofuran should be better than alcohol. We thus feel that the use of acetones and water soluble ethers as alkyl bromide solubilizers in electrochemical reductions in water solvent is also unexpected. Some other solubilizers which may be used include: some ketones, C H CN and CH CN.
  • TML has been regarded as perhaps mor beneficial in actual road octane rating than in the research or motor octane ratings usually performed at refineries.
  • TML can be produced cheaper than TEL.
  • Factors of cost include raw materials, electrical power, purification and product losses therefrom. in each of these factors, the TML process is superior to the TEL process.
  • mixed lead alkyls are superior in antiknock properties to tetraethyl lead (TEL) and to tetramethyl lead (TML). These antiknock compounds have been more expensive, and more laborious to prepare than TEL or TML.
  • TEL tetraethyl lead
  • TML tetramethyl lead
  • MLA mixed lead alkyls
  • the bromine formed at the anode can be recovered, for example, by the bromine recycle method using QBr (tetrabutylammonium bromide) in the anode and is based on the following three reactions:
  • the exchange reaction (3) is catalyzed by a phosphoniurn quat, (C H PC H +Br.
  • the exchange rate increases linearly with increasing quat concentration; it can also be increased sharply by increasing temperature.
  • reaction 3) is carried out at the outside of the anode loop. It is then sufficient to consider only reactions (1) and (2) in closing the anode loop.
  • Ethylbromide does not suffer this fault.
  • solubility of tribromide in ethylbromide is much higher than that in dibromocthane (exceeds 5 weight percent at 40 C.)
  • reaction (2) must be carried out in a pressure vessel since the vapor pressure of ethylbromide at 100 C. is about 5.7 atmospheres.
  • the whole solvent must be stripped off to recover the product, dibromoethane.
  • reaction (2) can be carried out at atmospheric pressure, and the product recovery is greatly simplified.
  • A passing an electrolyzing direct current through a liquid catholyte comprising (a) an alkyl bromide or a mixture of two alkyl bromides, in which the alkyl group has 1 to 3 carbon atoms, (b) a current carrier selected from the group consisting of tetraalkyl ammonium bromide and tetraalkyl phosphonium bromide, (c) water, and
  • improvement which comprises carrying out said process wherein the alkyl group in the tetraalkyl ammonium bromide or tetraalkyl phosphonium bromide current carrier is tetrabutyl and wherein the molar ratio of water to said current carrier is from about 30:1 to about 1000:1.
  • nonhydroxylic solubilizer is acetone, THF, acetonitrile or propionitrile.
  • anolyte solvent is water
  • the anolyte current carrier is (C H )4NBr or (C H PBr
  • ethylbromide or BrC H Br is added to remove bromine-current carrier complex from the anode compartment.
  • alkyl bromide is methylbromide and the product is TML.
  • alkyl bromide is ethylbromide and the broduct TEL.
  • alkyl bromide is propyl bromide and the product is TPL.
  • alkyl bromide is a mixture of methylbromide and ethyl bromide and the product is methyl-ethyl mixed lead.

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US863096A 1968-11-04 1969-10-02 Cathodic process for the preparation of tetraalkyl lead compounds Expired - Lifetime US3649482A (en)

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AT (1) AT299972B (de)
BE (1) BE741249A (de)
CA (1) CA960999A (de)
CH (1) CH510056A (de)
DE (1) DE1955201A1 (de)
ES (1) ES373470A1 (de)
FR (1) FR2022554A1 (de)
GB (1) GB1285209A (de)
LU (1) LU59753A1 (de)
NL (1) NL6916616A (de)
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US6428676B1 (en) 2000-11-08 2002-08-06 Enthone Inc. Process for producing low alpha lead methane sulfonate

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US8313634B2 (en) 2009-01-29 2012-11-20 Princeton University Conversion of carbon dioxide to organic products
US8721866B2 (en) 2010-03-19 2014-05-13 Liquid Light, Inc. Electrochemical production of synthesis gas from carbon dioxide
US8500987B2 (en) 2010-03-19 2013-08-06 Liquid Light, Inc. Purification of carbon dioxide from a mixture of gases
US8845877B2 (en) 2010-03-19 2014-09-30 Liquid Light, Inc. Heterocycle catalyzed electrochemical process
US8845878B2 (en) 2010-07-29 2014-09-30 Liquid Light, Inc. Reducing carbon dioxide to products
US8961774B2 (en) 2010-11-30 2015-02-24 Liquid Light, Inc. Electrochemical production of butanol from carbon dioxide and water
US8568581B2 (en) 2010-11-30 2013-10-29 Liquid Light, Inc. Heterocycle catalyzed carbonylation and hydroformylation with carbon dioxide
US9090976B2 (en) 2010-12-30 2015-07-28 The Trustees Of Princeton University Advanced aromatic amine heterocyclic catalysts for carbon dioxide reduction
US8821709B2 (en) 2012-07-26 2014-09-02 Liquid Light, Inc. System and method for oxidizing organic compounds while reducing carbon dioxide
US8641885B2 (en) 2012-07-26 2014-02-04 Liquid Light, Inc. Multiphase electrochemical reduction of CO2
US10329676B2 (en) 2012-07-26 2019-06-25 Avantium Knowledge Centre B.V. Method and system for electrochemical reduction of carbon dioxide employing a gas diffusion electrode
US8858777B2 (en) 2012-07-26 2014-10-14 Liquid Light, Inc. Process and high surface area electrodes for the electrochemical reduction of carbon dioxide
US9175407B2 (en) 2012-07-26 2015-11-03 Liquid Light, Inc. Integrated process for producing carboxylic acids from carbon dioxide
US9873951B2 (en) 2012-09-14 2018-01-23 Avantium Knowledge Centre B.V. High pressure electrochemical cell and process for the electrochemical reduction of carbon dioxide
CA2883367A1 (en) * 2012-09-19 2014-03-27 Liquid Light, Inc. Electrochemical co-production of chemicals employing the recycling of a hydrogen halide

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6428676B1 (en) 2000-11-08 2002-08-06 Enthone Inc. Process for producing low alpha lead methane sulfonate

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BE741249A (de) 1970-05-04
NO131458C (de) 1975-06-04
GB1285209A (en) 1972-08-16
FR2022554A1 (de) 1970-07-31
DE1955201A1 (de) 1970-05-27
LU59753A1 (de) 1970-01-13
NL6916616A (de) 1970-05-08
ES373470A1 (es) 1972-01-16
CA960999A (en) 1975-01-14
SU471724A3 (ru) 1975-05-25
AT299972B (de) 1972-07-10
NO131458B (de) 1975-02-24

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