JPS6012430B2 - Olefin reduction method - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improvements in methods for reductive coupling of olefins. Electroreductive coupling of like or different olefin reactants and especially Q,8-olefin nitriles,
The preparation of paraffin dinitriles, dicarpoxamides or dicarboxylates by electrolytic hydrogeno-dimerization of carboxamides or carboxylates is described, for example, in U.S. Pat.
It is well known from the specifications of Nos. 93475-7 and 3193481-83. Although this method is sufficiently attractive that it has been used commercially for over eight years, the preferred commercially available method to date is a cell separated into anolyte and catholyte parts by a cation-permeable membrane. Efforts have been made to improve the method with particular attention to eliminating the associated investments. For example, Canadian Patent No. 813,877 discloses that acrylonitrile, polybasic acid By electrolyzing neutral aqueous solutions of alkali metal salts and quaternary ammonium salts, a considerable amount of
The patent discloses that it is possible to produce adibonitrile with a yield of 1. However, the commercial use of low current densities requires excessive capital investment in the electrolytic cell, and the use of low temperatures requires expensive cooling of the electrolytic medium. Good adibonitrile yields can initially be obtained at high temperatures and current densities, but as shown in US Pat. No. 3,616,321 (see Example 2, Experiment 1), substantial Continuous electrolysis of a solution similar to that of the Canadian patent for several hundred hours at higher current densities (7.9 amps/day) resulted in unacceptably high anode corrosion rates (22 amps/year). and averaged over the length of the operating period, resulting in a yield of adibonitrile that is much lower than that reported in the Canadian patent for operation at 4 Amps/d. One approach to controlling such anodic corrosion is described in U.S. Pat. No. 3,616,321, which uses current densities up to 20 amperes/d In the production of azibonitrile by electrolyzing an aqueous emulsion of acrylonitrile, an alkali metal phosphate and a quaternary ammonium salt in an undivided cell with a graphite cathode and an iron or magnetite anode at temperatures close to room temperature). It is disclosed that corrosion of the anode is substantially inhibited by using an incipient electrolytic soot containing an alkali metal polyphosphate. However, from that patent (see Example 2 Experiment 2), it is shown that the anode corrosion rate is reduced when polyphosphate is present, but 2
Average adiponitrile yield and current effect over 1 hour of operation (74.7% and 70.5%, respectively)
can be seen to be even lower than that achieved at the same current density (7.9 amperes/d〆) but without the presence of polyphosphate. In preferred length operations for actual commercial operations,
at least a portion of the corrosion products of the heavy metal electrodes used in such methods tend to migrate into the electrolytic medium;
And it has also been found that it accumulates there in the form of deposits on the cathode, increasing the evolution of molecular hydrogen at the expense of process current efficiency, and gradually reducing the reaction selectivity for the desired coupling product. Ta. As described in Belgian Patent No. 804,365, the production of molecular hydrogen and anode corrosion in such a process can be achieved by incorporating nitrilocarboxylic oxides such as alkali metal salts of ethylenediaminetetracarboxylic acid into the electrolytic medium. can be substantially prevented. As disclosed in that patent, such compounds sequester heavy metals in the electrolytic medium and thereby prevent the formation of metal deposits on the cathode that normally accompany the production of molecular hydrogen in the cell. It is believed that. Also,
The incorporation of such compounds into the electrolytic medium, as set out in that patent, is described in Canadian Patent No. 813,877.
This makes it possible to operate the process for extended periods of time at current densities and temperatures considerably higher than those at which practical use of the process of this patent or US Pat. No. 3,616,321 is limited. Therefore,
The improvements described in that patent are very significant advances in the art. However, even when such compounds are retained in substantial concentrations in the electrolytic medium, the accumulation of heavy metals in the medium from electrode, especially anode corrosion, can eventually affect product selectivity, current efficiency, and other processes. This is usually accompanied by deterioration in performance characteristics. The appearance of such deterioration can be delayed and its extent reduced by incorporating heavy metal sequestering agents into the medium, as described above. And in some cases,
This can be achieved to some extent by incorporating polyphosphates as previously suggested for anode corrosion control, but for commercial operations it is difficult to simply add a sequestering agent to the initial electrolytic medium. It is desirable to prevent degradation of such processes to a greater extent than is achieved by incorporating the sequestering agent into the medium or even by maintaining the sequestering agent at a predetermined concentration in the medium throughout the electrolysis. , can retain product selectivity for a longer period of time,
And the longer and more completely the formation of molecular hydrogen that causes current efficiency reduction can be prevented, the lower the cost of producing the desired coupling product will be. Such improvements in this method are the object of the present invention. Other objects of the invention will be apparent from the description below, in which all percentages are by weight unless otherwise specified. The desirability of heavy metals in the medium is such that the olefinic reactants are reductively coupled by electrolyzing a liquid aqueous medium containing the reactants and substantial heavy metals are transferred into the medium during the electrolysis. No effect, such as increased production of molecular hydrogen and ultimate reduction in selectivity for the desired product, is achieved by adding sufficient free heavy metal sequestering agent to the medium during electrolysis to retain excess free sequestering agent in the medium. It has now been discovered that it can be substantially reduced by This is not necessarily the case in all cases, but typically if the heavy metal has migrated into the medium in greater amounts than is soluble in the initial electrolytic medium, An excess of free heavy metal sequestering agent than can be sequestered is added to the medium during electrolysis. The undesirable effects of heavy metals in the medium (e.g. increased molecular hydrogen production and eventual reduction in selectivity for the desired product) are often due to the fact that this essentially eliminates the metals transferred into the medium, e.g. during electrolysis. By adding sufficient free heavy metal sequestering agent to this medium during electrolysis to substantially completely dissolve the metal throughout its presence in the electrolytic zone, the metal is transferred into the medium over essentially its entire presence in the electrolytic zone. Substantially further reductions can be achieved by leaving the heavy metals substantially completely dissolved. In another embodiment of the invention, sufficient free heavy metal sequestering agent is added to the medium during electrolysis to maintain the concentration of undissolved heavy metals in the medium in the electrolysis zone below about 2 mmol/l.
These improvements in the process are due to the process being in an undivided cell and due to the dual hydrogenation of acrylonitrile. nylon 66
It is particularly, but not exclusively, useful when carried out in the preparation of the intermediate adiponitrile. Reactive components that can be reductively coupled by the method of the invention include all homogeneous or heterogeneous olefin compounds that can be reductively coupled electrolytically in an aqueous medium. Most commonly at present, such reactants are substituted olefinic compounds, such as those having the structure R = CR-X, where -
X is -CN, -CONR2 or -COOR',
R is hydrogen or R' and R' is C, to C4 alkyl (eg methyl, ethyl, n-propyrel, isopropyl, n-butyl, isobutyl or tertiary-butyl). Compounds having that formula are known as having Q,B-monounsaturated bonds, and in each such compound at least one R can be R', with at least one Another R of is hydrogen and at least one R', if present, can be an alkyl group containing the specified number of carbon atoms, with at least one other R', if present, being hydrogen. R' is an alkyl group containing different numbers of carbon atoms. Such compounds include olefin nitriles such as acrylonitrile, methacrylonitrile, crotononitrile, 2
-〆Tyrenebutyronitrile, 2-bentenenitrile, 2
-methyleneparellonitrile, 2-methyllenehexanenitrile, tiglonitrile or 2-butylidenehexanenitrile, olefin carpoxylates such as methyl acrylate, ethyl acrylate or ethyl crotonate, and olefin carpoxamides such as acrylamide, methacrylamide, N , N-diethylacrylamide or N,N-diethylcrotonamide. Hydrogenated dimerization products of such compounds include those having the structural formula Nitriles such as adiponitrile and 2,5-dimethyladiponitrile, paraffinic dicarpoxylates such as dimethyladipate and diethyl-3,4-dimethyladibate and paraffinic dicarboxamides such as adipamide, dimethyladipamide and N,N'-dimethyl-2, 5-dimethylazibamide is mentioned. Such hydrogenated dimers can be used as useful monomers in the production of high molecular weight polymers, including polyamides and polyesters, or as intermediates convertible to monomers by known methods. Other examples of various olefin reactants that can be reductively coupled by the methods of the present invention and coupling products produced thereby are described in U.S. Pat.
-79 and Oka No. 3193481-83. The present invention will now be described with respect to the electrolysis of a liquid aqueous electrolytic medium containing the olefinic reaction components. Such an electrolytic medium may be essentially a single-phase aqueous solution, or preferably an aqueous solution, such as a mixture of continuous phases, but typically dispersed throughout the aqueous solution. The mixture may be a multiphase mixture containing an undissolved organic phase. Gases such as vaporized reaction components, oxygen produced at the anode and in most cases hydrogen produced at the cathode, are also usually present in the medium in small proportions. If present, this organic phase may constitute up to about 25% or even more of the medium. And in certain attractive embodiments of the improved methods described herein, the organic phase comprises at least about 10% (eg, between about 12% and about 20%) of the medium. In certain continuous process embodiments that include recycling of unconverted olefin reactants, such organic phase typically contains (
most commonly at least about 65%, and even more typically at least about 75%) of the olefinic reactant to be coupled and the reduced coupling product and any small amounts of side reactions that are also likely present. product,
Consists of water and other materials. In the hydrodimerization of acryloetrile, such organic phase generally contains at least about 10%, preferably from about 15% to about 50%, and even more typically from about 20% to about 40% acrylonitrile. ing. In any case, the concentrations of constituents dissolved in the aqueous solution phase of the electrolytic medium listed herein relate only to the aqueous solution mentioned, and this The content is not the sum of that in the amorphous organic phase. This latter may, but need not, be present in the electrolytic medium when the invention is carried out as described above. On the other hand, the weight percentages of undissolved organic phase described herein are based on the combined weight of the aqueous solution and undissolved organic phase in the electrolytic medium. With respect to the components of the aqueous solution in the electrolytic medium, the olefinic reactants to be coupled are at least in such proportions that electrolysis of the medium as described herein results in the production of a substantial amount of the desired coupled product. It exists in The ratio is usually at least about 0.1 of the aqueous solution.
%, more typically at least about 0.5% and in certain embodiments of the invention preferably at least about 1%. The incorporation of one or more additive components that increase the solubility of the olefinic reactants in the solution can be used with solutions containing relatively high proportions of the reactants, such as at least about 5% or even 10% or more. may make it possible to implement this method. However, in many embodiments of the invention, the aqueous solution is about 5%
Less than (e.g., no more than 4.5%) olefinic compound, and in some embodiments preferably about 2.5%.
Contains not more than 5% olefin compounds. For example, in certain embodiments where quaternary ammonium cations are used to direct the reaction to the desired coupling product, the minimum required proportions of these cations are very small.
Generally, only an amount sufficient to give the desired product selectivity (typically at least about 75% and preferably at least about 80% for most olefin nitrile, carpoxylate or carboxamide couplings) is needed. be. However, much higher ratios may also be present if desired or convenient. In most cases, the quaternary ammonium ion is present at a concentration of at least 10-5 moles per portion of the aqueous solution, and even more typically at least about 10-4 moles per portion of the solution. The quaternary ammonium ion is generally about 0.5 mol/molar and even more commonly about 10-1 mol/molar, although higher proportions may be present in some cases as discussed above. It is present in aqueous solution at a concentration not exceeding . - In a preferred embodiment, the concentration of quaternary ammonium ions in the solution is
at least about 5 x 10-4 mol/sleeve, but about 5 x
Do not exceed 102 Mornok. Quaternary ammonium cations that can exist in such concentrations are those in which the nitrogen atom has a valence of 5 and is directly bonded to another atom (e.g. carbon) in such a way that it satisfies its valency of 4'5. It is a positively charged ion. Such ions can also be cyclic, as in the case of piveridinium, pyrrolidinium and morpholinium, but they generally preferably lack olefinic unsaturation and desirably contain hydrocarpyl groups (e.g. alkyl, aryl, etc.). ), trihydrocarpylammonium-substituted derivatives of such groups, and combinations of the like, from 4 to 48, preferably from about 6 to about 3, and even more preferably from about 7 to about It is of the type in which nitrogen atoms are directly bonded to four monovalent organic groups selected to have an average total carbon source content of 28. Suitable aryl groups typically contain 6 to 12 carbon atoms and preferably contain only one aromatic ring, such as in phenyl or penzyl groups. Suitable alkyl groups can be straight, branched or cyclic, and each typically contains 1 to 12 carbon atoms. Although quaternary ammonium ions containing combinations of such alkyl and aryl groups (e.g., penzyltrethylammonium cations) can be used, many embodiments of the invention are preferably practiced using tetraalkylammonium ions. and excellent results are generally obtained with those containing at least 3 C2-C6 alkyl groups and a total of 8 to 24 carbon atoms in the 4 alkyl groups, such as jetyldipropyl,
Ethyltripropyl, ethyltributyl, ethyltriamyl, ethyltrihexyl, octyltriethyl, tetrapropyl, methyltripropyl, decyltripropyl, meltributyl, tetrabutyl
, amyltributyl, tetraamylu, titrahexyl, ethyltrihexyl, diethyldioctyl ammonium and many others mentioned above in U.S. Pat. No. 3,193.
Nos. 475-7 and 3193481-83. The most practical from an economic point of view are generally tetraalkylammonium ions in which each alkyl group contains from 2 to 5 carbon atoms, such as diethyldiamyl, tetrapropyl,
Tetrabutyl, amyltripropyl, tetraamyl, ammonium, and others. Such cations may be added to the aqueous solution to be electrolyzed in any convenient manner, for example by dissolving quaternary ammonium hydroxide or a salt thereof in the amount necessary to provide the desired quaternary ammonium ion concentration. can be mixed in. However, quaternary ammonium cations in the electrolytic medium are only one way in which selectivity for certain reductive coupling products can be improved, and their presence is critical to the utility of the present invention. It should be recognized that this is not indispensable. The type of conductive salt used is likewise generally not a critical factor in realizing the advantages of the invention. Conducting salts may therefore be quaternary ammonium salts of the type hitherto used in the commercial practice of electroreductive coupling methods, such as tetraalkyl ammonium (e.g. tetraethylammonium) sulfate, alkyl sulfate (e.g. ethyl sulfate) or It can be an aryl sulfonate (eg toluene sulfonate). Although organic salts of that general type may be used as conductive salts in divided or undivided cells, it is generally preferred in most undivided cells to use other conductive salts, such as alkali metal salts. If alkali metal salts are used, lithium and especially sodium and potassium are generally preferred for economic reasons. Preferred for such use are salts of inorganic and/or polyhydric acids such as tetraalkylammonium or alkali metal orthophosphates, borates,
Perchlorates, carbonates or sulfates and especially incompletely substituted salts of that type, i.e. at least one valence whose anion is filled by hydrogen and at least one other valence filled by an alkali IJ metal. It is a salt with a valence of . Examples of such salts include dinatriwaum phosphate (Na2
HP04), potassium acid phosphate (KH2P04), sodium bicarbonate (NaHC03) and dipotassium shelfate (
K2HB03). Also alkali metal salts of condensed acids such as pyrophosphoric acid, metaphosphoric acid, metaphosphoric acid, pyrophosphate and others (e.g. sodium pyrophosphate, potassium metaphosphate, borax, etc.) and/or partial salts of such condensed acids. Or fully hydrolyzed products are also useful. Depending on the acidity of the aqueous solution in the electrolytic medium, the stoichiometric proportions of such anions and alkali metal cations in that solution may vary depending on the mixture of two or more such salts, e.g. sodium acid phosphate and diphosphate. It may correspond to a mixture with sodium. Such salt mixtures (each a mixture of salts of different cations, e.g. different alkali metals and/or different acids) are therefore referred to as "conducting salts", "alkali metal phosphates" as used herein. , shelf salt or carbonate” and other expressions.
All alkali metal acids can be dissolved in solution either neat or otherwise, eg as an alkali metal hydroxide and the acid necessary to neutralize the hydroxide to the desired pH. The concentration of conductive salt in the solution should be at least sufficient to substantially increase the electrical conductivity of the solution above its conductivity in the absence of such salt. In most cases a concentration of at least about 0.1% is preferred. More advantageous conductivity levels are achieved when the solution has at least about 1% conductive salt or even more typically at least about 2% such salt dissolved therein. . In many cases, preferred operating conditions include a solution having 5% or more (typically at least 5.5%) of the conductive salt dissolved therein.
When an alkali metal conducting salt is used, the maximum amount of salt in solution is typically limited only by its solubility therein, and this will vary depending on the particular salt used. In the case of salts such as sodium or potassium salts of phosphoric and/or shelf acids, about 7% to
It is generally most convenient for the solution to contain about 20% of such salt or mixture thereof. As mentioned above,
While electrolyzing the medium (e.g. from an electrode), the present invention
It must be concerned with reducing the potentially undesirable effects of heavy metals migrating into the electrolytic medium. In this specification, heavy metals are metals having a specific gravity of 4.0 or more, such as iron, cadmium, lead, zinc, nickel,
It means mercury, manganese, copper, cobalt, chromium, titanium, thallium, vanadium, molybdenium, ruthenium, antimony, bismuth, platinum and palladium. Prior to passing into the electrolytic medium, the heavy metal may be substantially pure or may be in a combinatorial form, such as a compound (eg, an oxide or salt) or an alloy of the metal. In general, metals that have a greater activity against adverse effects on the process after migration into the medium are those with low hydrogen overpotentials, such as iron, nickel, tungsten, cobalt and molybdenum, or in other words. , are typically unpreferred metals as cathode materials for reductive coupling methods. Accordingly, in many aspects, the present invention relates to heavy metals from the anode of an electrolytic cell, in particular an anode of an undivided cell, which is used in particular in a reductive coupling process. However, even metals of high hydrogen overpotential and potentially useful as reductive coupling cathode materials can also be used if present in the electrolytic medium in substantial concentrations, e.g. by sequestration, removal from the medium, or otherwise. It has been discovered that if this is not prevented, process performance can ultimately be adversely affected. This means that heavy metals migrating from the cathode into the medium have the potential to redeposit on the cathode in a somewhat different form or state than if they were originally part of the cathode. It can mean something. in any case,
In certain embodiments, the present invention relates primarily to heavy metals from the cathode used in the process, and thus the process improvements of the present invention may relate to metals transferred into the medium from the anode, the cathode, or both. Such metals may migrate into the medium as a result of physical attack or corrosion of process equipment, such as electrodes, pipes, etc., chemical or electrochemical attack or otherwise. It can therefore enter the medium as ions, oxides, hydroxides, salts (related to anions in the medium) such as phosphates, shelf salts, carbonates, sulfates, etc. or as more complex compounds. However, their chemical and/or physical forms and perhaps even their valence states may be present in the medium and/or they may be transferred into or out of the medium (e.g. deposited on the cathode of a cell). case), it undergoes a significant change. For example, at the surface of a ferrous metal anode (i.e. an anode containing iron, e.g. carbon steel, stainless steel or other iron-containing alloys, iron oxides e.g. magnetite or other iron compounds), iron is present in the phosphate anion-containing electrolytic medium. Iron phosphate is produced as a result of corrosion by iron phosphate which enters the medium or is otherwise present as a finely divided (e.g. colloidal) solid compound in the medium, e.g. Deposited as seeds or more iron oxides. Another aspect of the present invention is that the heavy metals that have migrated into the medium during electrolysis remain essentially substantially completely dissolved throughout the presence of the metal in the electrolytic zone. and in another aspect, it is related to maintaining the concentration of undissolved heavy metals in the electrolytic belt below about 2 mmol/〆. As used herein, a "single metal transferred into a medium" refers to a single metal that is immobilized on the surface of a device through which a liquid medium passes or circulates (e.g., an anode or cathode in an electrolytic cell in which the medium is electrolyzed). Heavy metals that enter the liquid medium in the sense that they become freely circulating with or in the medium, unlike heavy metals that
If heavy metals are separated from the medium by passing it through a membrane-type filter with a standard porosity of millimicrons, it is in an unmelted state, and conversely, by passing the medium through such a filter, heavy metals are removed from the medium. If not separated, the heavy metal is in a dissolved state. The "electrolytic zone" is the region occupied by the liquid electrolytic medium through which a current flows that reductively couples the olefin reaction components in the medium, and the "presence of heavy metals in the electrolytic zone" therefore refers to the olefin reaction. It refers to heavy metals present in a liquid medium that has been subjected to an electrolysis that reductively couples the components. Therefore,
Precipitation of heavy metals from the medium outside the electrolytic zone (e.g. by addition of heavy metal precipitating agents such as sulfides or ferricyanides) can be achieved by previously separating the precipitated metals in the medium being recycled (e.g. by centrifugation). , furnace filtration, etc.) or remelting, except to the extent that the solution medium is subsequently recirculated through the electrolytic band. The transfer of a metal into a medium at a substantial rate or at a "substantial rate" means that the metal is no longer capable of having an adverse effect, e.g. by removal from the medium or otherwise. It is meant that the amount and rate are sufficiently large to substantially adversely affect its operating properties, such as molecular hydrogen formation or product selectivity, during the electrolytic process, unless otherwise specified. The absolute amount or rate at which such an effect occurs will vary widely depending on the particular metal involved, the particular reductive coupling reaction desired, and many other process conditions. The fact that heavy metals that migrate into the medium during electrolysis are "substantially completely dissolved throughout" the presence of metal in the electrolytic zone means that the heavy metals that migrate into the medium during electrolysis are "substantially completely dissolved throughout" the presence of the metal in the electrolytic zone. Substantially all (typically at least about 80
%, preferably at least about 85% and most preferably at least about 90%). Shirtdown, upset or other variations result in relatively short periods of time during which heavy metals remain insoluble to such an extent, but typically there is such a period (e.g. batch (Formula) operation is 1
No more than about 20% of the time the electrolysis lasts, which can be as long as 0 to 2 hours or even less, or as long as several thousand hours or more in other (generally continuous) embodiments. and preferably about 1
It accounts for less than 0%. Heavy metal sequestering agents useful in keeping heavy metals in solution according to the present invention include various sequestering agents that bind metals to form soluble complexes in the presence of other chemical reagents that would otherwise tend to precipitate the metal ions. It can be any known compound. In some cases, capping agents that are at least partially organic, ie contain at least one organic component such as a carboxyl group or an amino- or hydroxy-substituted hydrocarbyl (eg alkyl) group, are preferred. Particularly preferred are amine/carboxylic acids having one or more amine groups and at least one carboxylic acid group, such as nitriloacetic acid and nitrilopropionic acid and glycine compounds. These are expressed by the following formula. Y2N→Z-YNnanR''
1C〇〇M In the above formula, Y is a monovalent group such as hydrogen, 1R''-COOM,
fCH2 naho, CH or C, ~C2. Alkyl (preferably C, ~C, alkyl such as ethyl, n-propyl, tert-butyl, n-hexyl, n-
decyl, etc.), and -R' is C ratio n or tC
HR...Na, R''' is hydroxy, -COOM,
fCH2nanC○OM or C, to C8 alkyl, hydroxyalkyl (e.g. hydroxyethyl) or hydroxyphenyl (e.g. orthohydroxyphenyl), Z is a divalent C2-C6 hydrocarbon group (e.g. alkylene group), e.g. n -hexylene, n-butylene, isobutylene or generally more preferably ethylene or n-
propylene, M is a monovalent group such as hydrogen, an alkali metal (such as lithium or more preferably sodium or potassium) or ammonium, m is 1 or 2, and n, if present, is tZ-YN )
-) and can be 0, 1, 2, 3 or 4, and in which at least one Y is -R
'-COOM or (-CH2nm+,OH, i.e., the compound is the right-most -COOM of the formula described herein).
Besides the R''-COOM group, at least one -R''-
It contains COOM or kiCQchim+, OH group.
Such additional R″-COOM or KiCH2nam+
, OH groups are usually desirably attached to the left-most nitrogen atom of the formula, but when n is 1, such additional groups (alternately or otherwise) -YN
It may be bonded to one nitrogen atom. and n is 2
. Preferably, but not necessarily, the capping agent is an aminocarboxylic acid compound, ie a compound having at least two -R''-COOM groups therein. Z is C2-C47 alkylene and n is 0,1,2
, or 3 (even more preferably 0, 1 or 2 and most preferably 1 or 2). Representative of such compounds are nitrilotriacetic acid, diethylenetriaminebentaacetic acid, N,N-
di(2-hydroxyethyl)glycine, ethylenediaminetetrapropionic acid, N,N'-ethylenebis[2-(o-hydroxyphenyl)]glycine and typically and most preferably ethylenediaminetetraacetic acid and N
-Hydroxyethyl ethylene diamine triacetic acid (hereinafter referred to as EDTA and HEDTA, respectively)
It is. At the low concentrations commonly used, they can be used as acids or, usually more conveniently and especially at alkaline pH, which is preferred for most embodiments of the invention, as partially or fully neutralized salts (e.g. (water-soluble ammonium or alkali metal salts of acids) can be added to the electrolytic medium. Known methods for the production of aminocarboxylic acid compounds, such as those described here, are generally referred to in Belgian Patent No. 804,365. For example, alkali metal salts of such compounds can be prepared by combining a suitable amine (e.g. ethylenediamine) with an alkali metal salt of chloroacetic acid in the presence of an alkali metal hydroxide, or with hydrogen cyanide and formaldehyde and then with an alkali metal hydroxide or with ethylene glycol. to form a hydroxyethyl substituent on the nitrogen of the amine and then react the hydroxyethyl substituted amine with an alkali metal hydroxide in the presence of cadmium oxide to convert the hydroxyethyl substituent to the desired converted into an alkali metal acetate substituent or by reaction with acrylonitrile in the presence of a base (e.g. sodium hydroxide) and then hydrolysis of this cyanoethylated amine in the presence of an alkali metal hydroxide. be able to. Other capping agents suitable for use in the present invention include Q-hydroxycarboxylic acids such as citric acid, tartaric acid, gluconic acid, etc., 3,5-disulfopyrocatechol, pyridine such as 2-aminomethylpyridine, N- Hydroxyethyl-2-aminomethylpyridine, 2-aminomethylpyridine-N-monoacetic acid, ethylenebis-N,N-(2-aminomethyl)-pyridine-N,
Mention may be made of N'-diacetic acid and many other compounds known in the art as sequestering agents, chelating agents, complex formers, and the like. [Chabelek and Martell, "Organic Sequestering Agents", John Wiley & Sons, 195 King Edition, Dower and Mellor, "Chelating Agents and Metal Chelates", Academic Press, 1964 King Edition, and Martell and Kelvin, "Metal Chelate Compounds" (See ``The Chemistry of Science'', Prentice-Hall Publishing, 1952 King Edition). As mentioned above, the object of the present invention can be achieved by adding a free heavy metal sequestering agent to the medium, where a free heavy metal sequestering agent is defined as one that sequesters heavy metals in the medium to its maximum capacity. This means no heavy metal sequestrants. Examples of such free sequestering agents include, for example, acid forms of such compounds, their alkali metal or ammonium salts and their non-sequestering or incompletely sequestering active ions in solution. In the present invention, the free sequestrant can be removed by suturing the free sequestrant into the medium anew or by regenerating the free sequestrant from the metal complexes in a portion of the medium outside the electrolytic zone (e.g. using a heavy metal precipitant). (by separating the metal from the complex). On the other hand, in still other systems, the free sequestering agent can be regenerated from the heavy metal complex separated from the medium, and the free sequestering agent thus externally regenerated can then be re-added to the medium. can. In any such system, the free sequestering agent is added to the medium continuously or intermittently and at any convenient point in the system, for example on the part of the medium undergoing electrolysis or (generally can be carried out (preferably in continuous systems) on a portion of the medium which is withdrawn from the electrolysis zone and recycled for further electrolysis. Also, as mentioned above,
The object of the present invention is achieved by retaining an excess of free heavy metal sequestering agent in the electrolytic medium, which provides a significant means ability. Said capacity is a (preferably substantial) excess of any metal sequestering capacity provided by the free sequestering agent in static equilibrium with the heavy metal in the medium. Usually, and especially relatively high equilibrium constants (i.e. lo
Regarding the generally preferred sequestering agents with gK), the concentration of free sequestering agents in static equilibrium with the heavy metals in the medium is so low that they have no practical significance. Therefore, the substantial concentration of free sequestrant measured in a medium can be viewed as being essentially the same as the excess free sequestrant concentration in that medium. However, excess free sequestering agent may be present in the medium, e.g. in systems where sequestering agent is continuously removed or otherwise lost from the medium and free sequestering agent is continuously added. It should be recognized that scales exist in dynamic equilibrium. Such a dynamic equilibrium concentration of free sequestering agent can be much greater than the normal static equilibrium concentration of free sequestering agent in such a medium, and this one type of equilibrium concentration is , should not be confused with the presence of excess free sequestering agent used in the present invention. Determination of the concentration of sequestrants (free or otherwise) was performed as previously described and as described in Keys to Chelation, published by The Dow Chemical Company.
(1969), as described in various publications, including (1969). Maintaining an excess of free sequestering agent in the medium as used herein means generally having an excess of free sequestering agent present in the medium throughout the operation of the process. Upsets and other variations may result in the absence of excess free sequestering agent for temporary and/or relatively short periods of time, but excess free sequestering agent typically occurs in some (e.g. batchwise) embodiments. at least about 80%, preferably at least about 90% of the time the medium is subjected to electrolysis, for short periods of time on the order of 10 to 20 hours, or on the order of thousands of hours or more in other (generally continuous) modes. and most preferably retained in the medium for about 100%.
The most desirable concentration of excess free sequestering agent will vary depending on many other operating conditions, but in many preferred embodiments the excess free sequestering agent will advantageously be at least about 2 mmol (and preferably is capable of sequestering at least about 4 mmol of heavy metals. In most embodiments of the invention, it is advantageous to add an excess of free heavy metal sequestering agent to the medium during electrolysis to sequester the amount of heavy metals that will migrate into the medium during the same or comparable period of time as electrolysis. In this specification, a certain amount of heavy metal is
"Sequestering" means, for example, that the amount of heavy metal is present in a form that can be easily sequestered, that the heavy metal and free sequestering agent are in close contact, and that the sequestration time approximates a static equilibrium state. This means that conditions are favorable for a lockdown, including In some cases, such equilibrium conditions cannot be reached under electrolytic conditions and, therefore, certain amounts of heavy metals cannot be sequestered without the addition of an amount of free sequestrant in the sense used herein. In some cases, it may not be possible to completely block it. In fact, as described hereinafter, despite the addition of free sequestering agents, which advantageously had the ability to sequester the amount of metals migrated into the medium, the amount of heavy metals migrated into the medium Embodiments exist in which a substantial proportion is not sequestered, or at least throughout its presence in the electrolytic medium. The amount of heavy metals transferred into the medium and the amount of free sequestering agent added "during electrolysis" can be considered with respect to any particular period of electrolysis, and of continued batch or continuous operation. It should also be recognized that the invention does not necessarily concern only electrolysis throughout the period or from the beginning of such operation or until the end of such operation. Also,
As used herein, "soluble in the initial electrolytic medium"
The expression refers to the solubility in the electrolytic medium used at the beginning of any such electrolytic period. However, the amount of heavy metals soluble in such a medium may decrease during electrolysis, for example if the initial medium contains sequestering agents that are susceptible to decomposition during electrolysis;
It should therefore be noted that the heavy metals that migrate into the medium during the substantial period of electrolysis are not soluble in as large a quantity as the metals were dissolved at the beginning of that period. Since substantial concentrations of dissolved heavy metals may also be present in the initial electrolytic medium, "an amount of a single heavy metal greater than that soluble in the initial electrolytic medium is defined as This means that the amount of heavy metals migrating into the electrolysis medium exceeds the amount that is soluble in the medium in addition to the amount that was dissolved in the "initial electrolysis medium" at the beginning of the period. As already mentioned, various sequestering agents, especially many containing organic groups, undergo decomposition in the electrolytic medium, for example by hydrolysis or oxidation, especially in embodiments using undivided cells, also at the anode. Some of the decomposition products have significant sequestering capacity;
It therefore constitutes a free sequestering agent in the sense used herein. Therefore, in part because of such decomposition, measurements of the presence or concentration of free sequestering agents are often made more important as a determination of sequestering capacity rather than as a qualitative or quantitative analysis of a particular sequestrant compound or group thereof. . In some systems, for example in batch operations which utilize a medium that can be safely discarded after separation of the reductive coupling products, the free sequestering agent is gradually dissolved in the electrolytic medium during the operation while being added to the medium. It may be practical to increase heavy metal concentrations in However, in other systems, including those in which the sequestering agent can decompose in the electrolytic medium, and especially where such decomposition can occur in direct relation to the concentration of the sequestering agent in the medium, It may be preferable to maintain essentially constant the concentration of heavy metals dissolved in the compound and thereby maintain essentially constant the concentration of sequestering agent necessary to maintain the heavy metals substantially completely dissolved. This can be done in various ways, for example by removing a portion of the medium from the system during electrolysis and replacing it with a second portion having lower dissolved heavy metals than in the removed portion or by sequestering. or alternatively, by precipitating the dissolved heavy metals and then removing the precipitation from a portion of the medium outside the electrolytic zone (eg, by filtration, centrifugation, etc.). In fact, it is a preferred embodiment of the invention in which the liquid aqueous electrolytic medium containing the olefinic reactants is subjected to electrolysis in an electrolytic zone, and thereby the reactants are reductively coupled and the heavy metals are transferring a substantial amount into the medium, removing a portion of the electrolytic medium from said belt, and removing the reductive coupling product from said removed aliquot (e.g. by decanting the product-containing organic phase). The dissolved heavy metals are separated and replaced with fresh olefinic reactants from the removed aliquots (e.g., by removing a fraction of the ejected aliquots from the system or The heavy metals are precipitated and then the precipitated metals are removed from said aliquots (by filtration or centrifugation), and all withdrawn fractions of said aliquots have lower dissolved heavy metals than that fraction. sufficient free heavy metals to retain an excess of free sequestering agent in the medium, and the removed aliquots are then recycled to the belt for subsequent electrolysis. A sequestering agent is added to the medium during electrolysis, and preferably in an amount sufficient to substantially completely dissolve the heavy metal throughout essentially its entire presence in the zone. As used herein, the expression keeping the dissolved heavy metal concentration in a medium essentially stable does not necessarily mean keeping the concentration within a particularly low range. And in fact, under the operating conditions involved, the concentration of heavy metals dissolved in the medium is 100% from the reference amount.
It can vary up to or even higher on the higher end. However, it is important to note that the dissolved heavy metal concentration is typically substantially less than the concentration that would otherwise rise during continuous transfer of the metal into the medium and addition of the free sequestering agents described herein to the medium. means that it is kept below a low maximum value. As used herein, dissolved heavy metals means heavy metals that are not separated from the medium by passing the medium through a membrane-type filter having a standard porosity of 0.45 microns. Thus, for typical systems, the concentration of heavy metals dissolved in the electrolytic medium can be easily determined by conventional analysis (eg, atomic absorption) of a sample of the medium passed through such a filter. In a particular system, the relative desirability of various techniques for keeping dissolved heavy metal concentrations stable is based on several factors. However, for many organic sequestering agents, including aminocarpoxy compounds such as EDTA and HEDTA, the concentration of dissolved heavy metals in the medium ranges from about 2 to about 50 (preferably from about 4 to about 30).
It has been found that a retention of mmol/saw is most desirable. This may be, for example, about 100 to about 250 cm (preferably about 200 to about 1500 feet) if the heavy metal is iron and the medium has a typical specific gravity of about 1.08. Corresponds to the concentration of iron dissolved in the medium.
For many such decomposable sequestrants, especially in undivided cells, the free sequestrant added to the medium will sequester at least about 1.5 times the amount of heavy metals that will be transferred to the medium during electrolysis. is generally preferred. This amount can usually be calculated from the measured concentration of metal in the electrolytic medium or from the quantitatively observed loss of metal from one or more electrodes. In fact, since the metal loss from the anode is usually closely related to the amount of current flowing through the medium in contact with it, the metal loss and free sequestering agent addition are expressed in millimoles per faraday of such current. It is often convenient to do some basic calculations. For example, for anodes made from ferrous metals, such as carbon steel, the added freestanding sequestrant will generally most desirably contain at least about 0.1 mmol of iron or other heavy metals per faraday of current through the medium. can be blocked. Since a number of sequestering agents are capable of sequestering heavy metals on a 1:1 molar basis, these sequestering agents (including aminocarboxyl compounds such as EDTA and HEDTA) are preferably used in most non-split compounds with such anodes. In the cell, free sequestering agent is added to the electrolytic medium in similar molar amounts, ie, at least about 0.1 mmol per faraday of current passing through the medium. For use of the invention in most undivided cells:
The tendency for corrosion of the anode and thus for the deposition of heavy metals on the cathode can be advantageously prevented by including in the electrolytic medium a shelf acid, a condensed phosphoric acid or an alkali metal salt thereof. The shelf acid or shelf acid salt can be added to the medium as an ortho-acid, meta-acid or pyro-acid and then neutralized as desired with, for example, an alkali metal hydroxide or such an acid. It can be added as a fully or incompletely substituted alkali metal salt (eg diodium or monosodium orthoate, potassium metatrate, sodium tetraporate or its hydrate form commonly referred to as porax). Condensed phosphoric acid or phosphate is polyphosphoric acid (
(e.g. pyrophosphate or triphosphate) and then neutralized to the desired pH, or as its fully or partially substituted alkali metal salt (e.g. tetrasodium pyrophosphate, potassium hexametaphosphate or sodium triphosphate). I can do it. Details regarding such use of shelf acids or condensed phosphoric acids or salts thereof in reductive coupling processes as heretofore described are contained in Belgian Patent No. 804,365. In most cases, the pH of the electrolytic medium (bulk) used in the present invention is greater than or equal to 2, preferably at least about 5, more preferably at least about 6, and most conveniently especially when the method has a metal anode. At least about 7 if done in an undivided cell. on the other hand,
The overall PII is generally not greater than about 1 square, and typically not greater than about 11. and when sodium and/or potassium phosphates are used, this is generally not substantially higher than about 10. The temperature of the electrolytic medium can be at any level compatible with the liquid state of the medium, ie above its freezing point but below its boiling point under the pressure used. Good results can be achieved at temperatures between about 50 and about 7 YO, or even higher if pressures of substantially 1 atmosphere or more are used. The optimal concentration range is
It will vary depending on the particular olefin compound and hydrogenation compound, among other factors. However, in the hydrogenation dimerization of acrylonitrile to adiponitrile, at least about 2
Electrolysis temperatures of 5:00 o'clock are usually preferred, and temperatures between about 40 o'clock and about 65 o'clock are particularly desirable. In fact, 4000 (
It is a particularly useful feature of the present invention that it can be used very satisfactorily at temperatures above (the highest temperatures listed as usable in the US Pat. No. 3,616,321 disclosure). This is because the electrolytic medium conductivity typically increases with temperature, and therefore the power cost of the process is generally lower above 40 q○ than at lower temperatures. As is well known, the electroreductive coupling of olefinic reactants (including those previously described herein) is accomplished by attaching the reactants to a cathode surface that has sufficient cathodic potential for reductive coupling of these reactants. It takes place in contact. Generally, there is no minimum current concentration that will allow the invention to be practiced, but in most cases the cathode surface 1
A current density of at least about 1 ampere per square decimeter (in A/d) is used, and at least about 1 ampere per square decimeter (A/d) is usually preferred. Although higher current densities may be practical in some cases, those generally used herein do not exceed about 150 A/d power, and even more typically about 75 A/d. That's not all. Depending on process variables, current densities of no more than about 50 A/d may be preferred in some embodiments. However, it is true that typically current densities of at least about 10 amperes per cathode surface ld, and in some cases even about 2 d/d or more, are most satisfactorily practiced. This is a significant advantage of the invention. Although not required, liquid impermeable cathodes are usually preferred. When using such a cathode, the aqueous medium to be electrolyzed generally has a concentration of at least about 0 with respect to the adjacent cathode surface.
．． It is passed between the anode and cathode at a linear velocity of 304 m/sec, preferably about 0.608 m/sec, and even more preferably from about 0.914 m/sec to about 2.438 m/sec. However, speeds up to 6.1 m/sand or higher can be used if desired. The air gap between the anode and cathode can be very narrow, for example about 0.1 inch or less, or it can be as wide as 1.27 inch or more. However, it is usually most conveniently between about 0.152 and about 0.635c. The cathode surface can be made of virtually any material that can provide the necessary cathode potential and does not dissolve or corrode at an unacceptable rate. For example, the process can generally be carried out using a cathode consisting essentially of cadmium, mercury, thallium, lead, zinc, manganese, tin (perhaps not suitable for certain nitrile reactants) or graphite; This means that the cathode surface contains a high percentage (generally at least about 95% and preferably at least about 98%) of one or a combination of two or more such materials (e.g., an alloy). However, it does not change the properties of the cathode surface so as to interfere with the substantial realization of the advantages of the invention described herein.
This means that it may contain small amounts of species or more components. When present in substantial concentrations, such other components are preferably other substances with relatively high hydrogen overpotentials. In general, cathodes consisting essentially of cadmium, lead, zinc, manganese, graphite or an alloy of one of such materials are particularly preferred, and in particular cathodes consisting essentially of cadmium. Best results are usually at least about 99.5%, even more typically at least about 99.8% and most preferably at least about 99.5% as in ASTM Standard B440-6 (published in 1966). Obtained using a cathode surface with a power dome content of 9%. The cathodes used in the present invention can be prepared by a variety of techniques - for example, by electroplating the desired cathode material onto a suitably shaped substrate of another material (e.g. a metal with greater structural rigidity); Layers of cathode material can be produced by chemically, thermally and/or mechanically bonding to similar substrates. Alternatively, plates, sheets, rods or any other suitable structure consisting essentially of the desired cathode material may be used in place of such substrates, if convenient. The method of the present invention comprises a cation-permeable membrane separating the anode and cathode compartments of the cell so that an electrolytic medium that is in direct physical contact with the cathode of the cell does not simultaneously come into direct contact with the anode of the cell; It can be carried out in divided cells with diaphragms and the like. However, it is particularly advantageously used in cells that are not divided in such a manner, ie in cells where the electrolytic medium is simultaneously in direct physical contact with the anode and cathode of the cell. In fact, it is carried out in an undivided cell with an anode containing ferrous metal, using conductive salts of alkali metal phosphates, lateral salts or carbonates and an electrolytic medium with a pH not substantially below 7. This is a preferred embodiment of the present invention. Of particular interest are embodiments using anodes consisting essentially of carbon steel. Exemplary compositions of this are those listed in the American Iron and Steel Institute and Society of Automotive Engineers Standard Steel Composition Numbers 1000, 1100 and 1200 series, many of which It can be found in the "Metals Hand Book" (1961) 8th edition, Volume 1, page 62 (published by the American Society for Metals). In general, the carbon steel advantageously used as the anode material in the method of the invention will be about 0.0
It contains between 2% carbon (more typically at least about 0.05% carbon) to about 2% carbon. Generally carbon steels such as those of the standard steel composition numbers AISI and SAEIOOO series are preferred, and those typically containing between about 0.1% and about 1.5% carbon are most desirable. Regardless of the material from which it is manufactured, each anode in a cell can be a plate, sheet, strip,
It can be a rod or any other structure suitable for the intended use. In one embodiment, the anode is in the form of a sheet (eg, of carbon steel) that is essentially parallel to the cathode surface and raised a narrow distance from the cathode surface of about the same dimensions. In some cases, one side comprises a suitable anodic material (e.g. magnetite or steel obsessive material) and the other side comprises a suitable cathode material (e.g. conveniently electroplated on a support material or other material). It comprises a series of substantially parallel plates or sheets of self-supporting material (e.g. iron or steel) coated with cadmium or other metals coated in the manner of If it is possible to pass through a plurality of channels between plates or sheets such as It is very advantageous to use a multi-cell package that is tightly packed. In the following specific example, the heavy metals present in significant proportions in the electrolytic medium are iron and cadmium. This latter is known from published data and experimental comparisons to be sequestered by the type of sequestering agent used, in the same molar proportion and essentially completely in preference to iron. It is being Therefore, in the following examples, the ability of the electrolytic medium to dissolve additional cadmium or iron was determined as follows. i.e.

[1-A representative sample of the electrolytic medium is diluted and then filtered through a membrane-type filter having a standard porosity of 0.45 millimicrons to remove essentially all solids, {2}
The weight concentrations of iron and cadmium in the first aliquot of the reactor sample are determined individually by atomic absorption, and the In addition to the two aliquots, the aliquots were then incubated for a sufficient number of hours, refurbished, and analyzed for their cadmium weight concentration in the same manner as was done for the first aliquot of the sample, as described herein. Convert the weight concentrations of cadmium and iron measured in the above manner into molar concentrations; It is subtracted from the concentration. This difference represents the molar concentration at which the representative sample has the ability to dissolve additional iron or cadmium in addition to the iron and cadmium actually dissolved in the media sample. Also, in the following examples, acrylonitrile and adiponitrile are generally designated AN and ADN, respectively. Example 1 In the continuous method, [1] about 1.7% AN, 1.
A sodium orthophosphate mixture corresponding to a solution of 2% ADN, 10% pH 9 and an aqueous solution containing 4 to 9 x 10-3 mol/ethyltributyl ammonium ion dissolved in the solution of about 99% and about 1% { 2) Approximately 31%AN, 5
A liquid electrolytic medium consisting of about 1% of a dispersed but undissolved organic phase containing 2-53% ADN, 8-9% AN dimerization byproduct and 8% water was mixed with 55oo and 1%
．． Cadmium (at least 99.9%Cd)
) MS separated by a distance of 0.238 skin from the cathode
I was circulated through an undivided electrolytic cell with an I020 carbon steel anode and electrolyzed at a current density of 20 amps per anode or cathode surface as it passed through the cell. The organic phase containing product ADN, by-products and unreacted AN was separated from the electrolytic medium, supplementary AN was added, after which the medium was recycled to the cell and electrolyzed again under the conditions described above. Initially, the medium contained dissolved iron and cadmium at concentrations of 4.75 and 0.24 mmol/sole, respectively, and the medium contained an additional 5.8 mmol/sleeve, but no more than that amount of iron and/or cadmium. It contained tetrasodium ethylenediaminetetraacetate (Na4EDTA) and its decomposition products in such proportions that it could be dissolved. 0.28 mmol of Na4EDTA per faraday of current through the medium is added to this circulating medium, and 13.2 mm of solution is removed from the system, keeping the concentration of these components of the solution at said level and the concentration of the medium. Sufficient water containing dissolved ethyltributylammonium ion and sodium orthophosphate was displaced to keep the total volume essentially constant. Under these conditions, the anode and cathode contain "0.139 mmol of iron and 0.0 mmol of iron per faraday of such current.
With an average rate such that 0.8 mmol of cathodomium migrates into the medium (approximately 0.063 and 0.007 mmol respectively)
The iron and cadmium which corroded in the skin/year) and migrated to the medium during electrolysis exceeded 5.8 mmol per medium during the first 18 hours of electrolysis. The addition of 0.28 mmol Na4EDTA per faraday retains an excess of free sequestering agent in the aqueous phase of the medium with an average sequestering capacity of 2 mmol iron or cadmium per solution making up the aqueous phase. I forced it. The concentrations of iron and cadmium dissolved in the solution were 206-378 and 28-3 kaku (4-7.3 and 0.27-0.34), respectively.
It was stable in the range of mmol/unit). On the other hand, about 40% of the iron transferred from the anode into the electrolytic medium produced solids that could be removed by furnace filtration. During 35 hours of electrolysis under these conditions, AN was converted to ADN with an average selectivity of 86.5%, and the voltage drop across the cell was stable between 3.9 and 4.0 volts, The hydrogen content percentage in the electrolytically generated gas was 8% on average. At that time, the removal (purge) speed was 4.4
It was lowered in the evening/Faraday. Iron and cadmium continued to migrate into the electrolytic medium at essentially the same average rate as before, but unexpectedly, the concentration of iron dissolved in the solution did not increase. Instead, its concentration remains stable in the range of 290-32 mmol/so, while about 80-85% of the iron transferred from the anode into the electrolytic medium is A solid was produced which could be removed by filtration. At lower removal rates, 0.28 mmol Na4EDTA per faraday
The addition of 20% caused an excess of free sequestering agent to be retained in the aqueous phase with an average sequestering capacity of 4.3 mmol of iron or cadmium per solution. The concentration of cadmium dissolved in the solution was stable in the range of 70-8 fields (0.77 mmol/day). After an additional 191 hours of electrolysis under these conditions, AN was converted to ADM with an average selectivity of 87%, the voltage drop remained below 4 volts, and the volume percent hydrogen in the evolved gas was on average 10%. It was below.
Comparative Example A An electrolytic medium essentially identical to that of Example 1 was electrolyzed under essentially the same conditions as Example 1. However, the intermediate removal ratio is 8.06 mmol of Na and the lower 0.085 mmol of Na
A loading ratio of 48DT was used. Under these conditions, the concentrations of iron and cadmium dissolved in solution were stable at approximately 260 and 4 mmol/day (5 and 0.39 mmol/night), respectively, but at least as low as Example 1. For iron and cadmium that migrated into the electrolytic medium at average rates, the Na4EDTA addition was not sufficient to retain excess free sequestrant in the medium. and 16
After a lake hour of electrolysis, the corrosion of the anode is accelerated to a much higher rate, the ADN selectivity drops to 84%, the intra-cell voltage drop rises to 4.4 volts, and the volume% of hydrogen in the evolved gas decreases. rose to 26%. Example B In the continuous method, (1) 1.3% to 1.6% AN, about 1.2% ADN, 4 to 10 x 10-3 mol/
A mixture of the ethyltributylammonium ion, 10% sodium orthophosphate and sodium sulfate (prepared by neutralizing an amount of orthosulfate equivalent to a 2% solution to a solution trace of 8.5) was dissolved. about 99% of the aqueous solution and [21 about 24-30% AN, 54-
60% ADN, 8% AN dimerization byproduct and 8%
A liquid electrolytic medium consisting of about 1% of a dispersed undissolved organic phase containing 5,500 and 1.2
NSI spaced 0.178 C from the cadmium (at least 99.9% Cd) cathode at 2/sec.
It was cycled through an undivided electrolytic cell with an I020 carbon steel anode and electrolyzed at a current density of 16 amps per anode or cathode surface as it passed through the cell. The organic phase containing product ADN, by-products and unreacted AN was separated from the electrolytic medium and supplemental AN was added before the medium was recycled to the cell and electrolyzed again under the conditions described herein. Initially, the medium has approximately 6.8 mmol/its dissolved iron, and the medium has an additional 4.9 mmol/dissolved iron.
It contained Na4EDTA and its decomposition products in such a proportion that it was capable of dissolving iron and/or cadmium, but not more than that amount. 0.4 mmol of Na4EDTA per faraday of current through the medium was added to the circulating medium and 12 ml of solutions were removed from the system and the constituent concentrations of these solutions were kept at the above levels and the total volume of the medium was reduced to essentially The solution was replaced with water containing enough dissolved ethyltributylammonium ion and sodium orthophosphate and sodium sulfate to keep the temperature constant. Under these conditions, the anode and cathode have 0.09 mmol of iron and 0.09 mmol of iron per faraday of such current.
Corroded at an average rate (approximately 0.033 and 0.077 mm/year, respectively) such that 0.09 mmol of cadmium migrated into the medium. The iron and cadmium transferred to the medium during electrolysis exceeded 4.9 mmol per medium during the first four hours of electrolysis. 0.4 per faraday
The addition of mmol of Na4EDTA causes an excess of free sequestering agent to be retained in the aqueous phase of the medium with an average sequestering capacity of 2.5 mmol of iron or cadmium per night of solution constituting the aqueous phase, and Concentrations of dissolved iron and cadmium are 32.6-450 and 3, respectively.
5-9Q side (6.3-8.7 and 0.34-0.87
It was stable in the range of mmol/〆). After performing 23-time electrolysis, AN was converted to ADM with a selectivity between 87.5% and 50% throughout the operation,
The voltage drop in the cell (3.73 volts) did not increase after the start of operation, and the volume percent of hydrogen in the evolved gas averaged 4 to
5%, maximum value 6% and final value 5.5%. Example m Initially the electrolytic medium contains dissolved iron and cadmium with concentrations of about 11.1 and 2.4 mmol/its, respectively, the rate of Na4EDTA addition is 0.495 mmol/day and the current density is 42. Essentially the same method as Example 0 except for 18.5 Amps/d.
If continued for 9 hours, the anode and cathode will move at an average rate such that 0.132 mmol of iron and 0.012 mmol of cadmium will migrate into the medium per faraday of current passing through the medium (approximately about 0.055 and 0.05 mmol, respectively). .010 skin/year). The iron and cadmium transferred to the medium during the first 31 hours of electrolysis exceeded 4.9 mmol per medium.
0.495 mmol Na4EDTA per faraday
The addition of 10.0% resulted in an excess of free sequestering agent being retained in the aqueous phase of the medium with an average sequestration capacity of 5.75 mmol of iron or cadmium per night of solution making up the aqueous phase. The concentration of iron and cadmium dissolved in the solution is 455
It was stable in the range of ~570 and ~178 ppm (8.8-11.0 and 0.9-1.7 mmol/〆). Under these conditions, AN was 88% and 8%, respectively.
converted to ADN with an average and final selectivity of 7.1%,
The voltage drop within the cell was stable at 3.84-3.9 volts, and the volume percent hydrogen in the evolved gas averaged about 10% and the final value was 16.4%. Example W In the lotus bran method, about 1 to 1.5% AN in '11
, 1.2% ADN, 12.2% potassium orthophosphate, ethyltributylammonium ion (7.5-16
x 10-3 mol/night) and sodium esterate (produced by neutralizing an amount of ortho-sherate to a solution foot of 8.5 times the equivalent of a 2% solution) in an aqueous solution of approximately 99 % and ■ AN of 18-27%, 57-66%
of ADN, about 1% of a liquid electrolytic medium consisting of a dispersed but insoluble organic phase containing 8% of dimerization by-products and 8% of water at 55° C. and 1.22 skin/sec. Cadmium (at least 99.9% Cd) from the cathode.
It was circulated through an unsplit electrolytic cell with AIS II 020 carbon steel anodes spaced apart by 178 arcs and electrolyzed as it passed through the cell at a current density of 16 Amps per anode or cathode. . The organic phase containing product ADN, by-products and unreacted AN is separated from the electrolytic medium and supplementary AN is added, after which this medium is recycled through the cell and electrolyzed again under the conditions described herein. did. Initially, the medium contained 13.7 mmol/concentration of dissolved iron and Na4EDTA and its decomposition products in proportions such that the medium could dissolve any additional iron or cadmium. 0.4 mmol of Na4EDTA per faraday of current passing through the medium is added to the circulating medium and 12 days of solution is removed from the system, keeping the concentration of these components of the solution at said level and the concentration of the medium. Ethyltributylammonium ions in a state of sufficient solution to keep the total volume essentially constant were replaced with water containing potassium orthophosphate and sodium sulfate. Corroded at an average rate (approximately 0.038 and 0.007 c/year, respectively) such that 0.104 mmol of iron and 0.009 mmol of cadmium per faraday migrated into the medium. Na4EDT
The addition of A caused an excess of free sequestering agent to be retained in the aqueous phase of the medium with an average sequestering capacity of 3 mmol of iron or cadmium per solution constituting the aqueous phase. And the concentrations of iron and cadmium dissolved in the solution are 519-708 and 209-475 legs (10.3
-14.1 and 2.1-4.7 mmol/〆). After 23 $ hours of electrolysis under these conditions, AN was converted to ADN with an average and final selectivity of 88%, the intra-cell voltage drop (3.65 volts) did not increase after the start of operation, and Volume % of hydrogen in generated gas
3-4%, and the final value was 4.4%. Example V In continuous method, about 85.4% '1' among which about 1.7%
AN, 1.2% ADN, . Produced by neutralizing 10% sodium orthophosphate, 2 to 5 x 10-3 mol/its ethyltributylammonium ion and an amount of orthoshelf acid corresponding to a 1.8% solution to a solution level of 8.5 An aqueous solution of about 85.4% and (2) about 31% AN, 53~
54% ADN, 7-8% dimerization byproducts and 8%
A liquid electrolytic medium consisting of approximately 16.4% of a dispersed but undissolved organic phase containing water of
Mountain SI separated from the cathode by a spacing of 0.178
It was circulated through an undivided electrolytic cell with an I020 carbon steel anode and electrolyzed at a current density of 18.5 Amps per anode or cathode surface ld during each passage through the cell. The organic phase containing the product ADN, by-products and unreacted AN was separated from the electrolytic medium, supplementary AN was added, and this medium was then circulated through the cell and electrolyzed again under the conditions described herein. Initially, this electrolytic medium contained dissolved iron and cadmium at concentrations of 9.0 and 2.75 mmol, respectively;
However, it contained Na4EDTA and its decomposition products in such a proportion that it could dissolve iron and/or cadmium (but not more than that amount). 0.4 mmol of Na4EDTA per faraday of current through the medium was added to the circulating medium and 12 mmol of the solution was removed from the system, keeping the concentration of these components of the solution at the stated level and reducing the total volume of the medium. Displacement was made with water containing enough dissolved ethyltributylammonium ion and sodium orthophosphate and sodium shelfate to keep it essentially constant. Under these conditions, the anode and cathode move at an average rate such that 0.12 mmol of iron and 0.008 mmol of cadmium per faraday of such current migrate into the medium (approximately 0.05 and 0.00 mmol, respectively).
7 years ago). and the iron and cadmium that migrated during electrolysis into the medium are 5% during the first 37 hours of electrolysis.
．． It exceeded 25 mmol/so. 0.4 per faraday
The addition of mmoles of Na4EDTA caused an excess of free sequestering agent to be retained in the liquid phase of the medium with an average sequestration capacity of 5.25 mmoles of iron or cadmium per night of solution making up such aqueous phase. The concentrations of iron and cadmium dissolved in the solution were 465-490 and 170-28 (9-9.5 and 1.6-2.8), respectively.
It remained stable in the range of millimoles/day). After 6 periods of time electrolysis under these conditions, AN was converted to ADN with an average and final selectivity of 87.8%, the intra-cell voltage drop was stable below 4 volts, and The volume percent hydrogen was on average 3-4%, with a final value of 6%. In the example continuous process, about 99% '1 - 1.4% to 1.8% AN dissolved therein, about 1.2% ADN, 10
~11% sodium orthophosphate, ethyltributylammonium ion (approximately 1.4 x 10-3 mol/s) and sodium esterate (an amount equivalent to a 2% solution) was added to a solution trace of 8.5%. About 99% of an aqueous solution containing a mixture of
~32% AN, 53-59% ADN, 6-7% A
A liquid electrolytic medium consisting of approximately 1% of a dispersed but undissolved organic phase containing N dimerization by-products and 8% water was heated at 55 qo and 1.22 m/s with cadmium (at least 99.9 %) circulated through an undivided electrolytic cell with an AIS II 020 carbon steel anode spaced 0.178 skins apart from the cathode and 18.5 d force per anode or cathode surface as it passed through the cell. Electrolyzed at a current density of ampere. The organic phase containing the product ADN, by-products and reaction mixtures was separated from the electrolytic medium and supplementary AN was added after which the medium was recycled to the cell and electrolyzed again under the conditions described. Initially, this medium has approximately 12
．． 8 and 2.7 mmol/concentration of dissolved iron and cadmium, and trisodium in proportions such that the medium is capable of dissolving an additional 4.9 mmol/(but not more) of iron and/or cadmium. Hydroxyethylethylenediaminetetraacetate (Na3HE
DTA) and its decomposition products. 0.495 mmol N per faraday of current through the medium
a3HEDTA was added to the circulating medium and 12
The evening solution is removed from the system and filled with enough dissolved ethyltributylammonium ion and sodium orthophosphate to maintain the concentrations of these components in the solution at the aforementioned levels and to keep the total volume of the medium essentially constant. It was replaced with water containing sodium chloride. Under these conditions, the anode and cathode move at an average rate such that 0.14 mmol of iron and 0.022 mmol of cadmium per faraday of such current migrate into the medium (approximately 0.059 and 0.020 skin/year). The iron and cadmium that migrated into the medium during electrolysis were then reduced to 4.5% per medium during the first 27 hours of electrolysis.
It was more than 9 mmol. 0.495 per faraday
The addition of mmol of Na3HEDTA retained an excess of free sequestering agent in the aqueous phase of the medium with an average capacity to sequester 4.6 mmol of iron or cadmium per hour of solution making up the aqueous phase. The concentrations of iron and picadmium dissolved in the solution are
5 powder to 668 and 106 to 279 blood (10.
It was stable in the range of 4 to 12.9 and 1.0 to 2.7 mmol/〆). Approximately 4% of the iron transferred from the anode into the medium formed solids that could be removed by filtration.
During 241 hours of electrolysis under these conditions, AN was converted to ADN with average and final selectivities of 89.3% and 89.0%, respectively, and the intra-cell voltage drop was stable at 3.9 volts, The volume percentage of hydrogen in the generated gas was 4.5% on average, and the final value was 5.4. Example: When an electrolytic medium essentially identical to that of the example is electrolyzed for 36 hours under conditions essentially the same as that of the example, the anode and cathode will have a current of 0.1 per faraday through the medium.
It corroded at an average rate such that 37 mmol of iron and 0.019 mmol of cadmium migrated into the medium (approximately 0.058 and 0.017 arcs per year, respectively). The iron and cadmium that migrated into the medium during electrolysis exceeded 4.9 mmol/night of medium during the first two lifetimes of electrolysis. The addition of 0.495 mmol of NaHEDTA per faraday results in an excess of free sequestration in the aqueous phase of the medium with an average capacity of sequestering 5.6 mmol of iron or cadmium per night of solution making up that aqueous phase. The drug was retained. And the iron and cadmium concentrations dissolved in the solution are 506-558 and 105-27 & blood (9.8-
It was stable within the range of 10.8 and 1.0-2.7 mmol/so). Under these conditions, AN'ma88
．． AD with average and final selectivity of 7% and 87.1%
M was converted. The voltage drop in the cell is stable at 3.9 volts, and the volume percent hydrogen in the evolved gas averages 7.9 volts.
2% and the final value was 8.5%. Example In dish continuous method, '1' between 85.9% and 87.5%, in which 1.4% to 1.6% AN, about 1.2% ADN
, 9.6-9.9% sodium orthophosphate, ethyltributylammonium ion (0.8-2.5 x 10-
An aqueous solution 85 in which a mixture of sodium esterate (produced by neutralizing the corresponding amount of orthochloric acid to a solution side of 8.5-9 in a solution of about 2%) . 9-87.5% and '2) AN of 26-29%, 54
A liquid electrolytic medium consisting of 12.5-14.1% of a dispersed but undissolved organic phase containing ~59% ADN, 7-9% AN dimerization byproducts and 8% water. ,
circulating at 55 pm and 1.158 m/sec through an undivided electrolytic cell having an AISI I020 carbon steel anode spaced 0.228 skin apart from the cadmium (at least 99.9% Cd) cathode; And while it passed through the cell, the anode was electrolyzed at a current density of 20 amperes per surface ld force of the cathode. The organic phase containing product ADN, by-products and unreacted AN is separated from the electrolytic medium, supplementary AN is added, after which this medium is recycled to the cell and again under the conditions described herein. Electrolyzed. Initially, this electrolytic medium contains dissolved iron and cadmium at concentrations of 6.9 and 1.25 mmol/concentration, respectively, and the medium contains an additional 2.75 mmol/concentration (but not more than that weight) of iron and/or cadmium. Na4EDT in such a proportion that it can dissolve
It contained A and its decomposition products. 0.475 mmol Na4E per faraday of current passing through the medium
DTA is added to the circulating medium and about 10 minutes of solution is removed from the system, and enough dissolved ethyltriptylammonium is added to maintain the concentrations of these solution components at the aforementioned levels and to keep the total volume of the medium essentially constant. It was replaced with water containing ions and sodium orthophosphate and sodium sulfate. Under these conditions, the anode and cathode are transported at an average rate such that 0.12 mmol of iron and 0.014 mmol of cadmium per faraday of such current migrate to the medium (0.05 and 0.0 mmol per year, respectively). 012 arc) was corroded. The iron and cadmium that migrated into the medium during electrolysis are... During the first 10 hours of electrolysis, more than 2.75 mmol per medium was obtained. 1
The addition of 0.475 mmol Na4EDTA per faraday results in 3.6 mmol per faraday of the solution making up the aqueous phase.
An excess of free sequestering agent with an average capacity to sequester millimoles of iron or cadmium was retained in the aqueous phase of the medium. The concentrations of iron and cadmium dissolved in the solution are 350-550 and 130-165 feet (6.8
~11.6 and 1.25-1.55 mmol/〆). After electrolyzing for 26 hours under these conditions, AN was converted to ADM with average and final selectivities of 87% and % respectively, the intra-cell voltage drop was stable at 4 volts, and the hydrogen in the evolved gas was The volume percent was found to average about 6.5% and the final value was 10.4%. Example K In a continuous process, '1} 1.4% to 1.8% AN dissolved therein, about 1.2
%ADN, 10-11% of sodium orthophosphate, ethyltributylammonium ion and sodium esterate (produced by diluting an amount of orthophosphate equivalent to a 2% solution to a solution size of 8.5%) ) with a mixture of about 97% and {2'27-32% A
A liquid electrolytic medium consisting of approximately 3% of a dispersed but undissolved organic phase containing N, 53-59% ADN, 6-7% AN dimerization by-product and 8% water was
0 and 1.22/sec, cadmium (at least 99
．． 9% Cd) is circulated through an unsplit electrolytic cell with an MSII 020 carbon steel anode spaced 0.178 arcs apart from the cathode, and as it passes through the cell the anode or cathode surface ld Electrolysis was carried out at a current density of 18.5 amperes per hour. The organic phase containing product ADN, by-products and unreacted AN was separated from the electrolytic medium, supplementary AN was added, after which the medium was recycled through the cell and electrolyzed again under the conditions described. Initially this medium is about 1
trisodium in such proportions as to be capable of dissolving dissolved iron and cadmium in concentrations of 2.8 and 2.7 mmol/concentration, and a further 4.9 mmol/concentration (but not more) of iron and/or cadmium; Hydroxyethylethylenediamine triacetate (Na3HED
TA) and its decomposition products. 0.495 mmol Na per faraday of current passing through the medium
3 HEDTA is added to the circulating medium and 12 ml of solution is removed from the system, and sufficient dissolved ethyltributylammonium ions and 12 ml of dissolved ethyltributylammonium ion are added to keep the concentrations of these components of the solution at the aforementioned levels and the total volume of the medium essentially constant. It was replaced with water containing sodium orthophosphate and sodium shelfate. Under these conditions the anode and cathode's current is such that 0.14 mmol of iron and 0.022 mmol of cadmium migrate into the medium per faraday of current (approximately 0.059 mmol per year, respectively).
and 0.020 skin). The iron and cadmium transferred to the medium during electrolysis was greater than 4.9 mmol per medium during the first two pulses of electrolysis. And the concentrations of iron and cadmium dissolved in the solution are 538-668 and 106-279 feet (10.4-279 feet), respectively.
It was stable in the range of 12.9 and 1.0-2.7 mmol/and). The media and combined process effluent (separated organic phase and solution removals) were filtered through a 0.45 millimicron standard porosity membrane-type filter, the solids thereby removed were analyzed, and such Comparing the amount of undissolved iron and cadmium present in the solid with the amount of dissolved iron and cadmium present in the medium or previously removed in the removal material, the iron and cadmium transferred to the medium during electrolysis are Cadmium is at least the following % i.e. Fe9
5.8%, Cd 99.7% and a total of 96.9% of Fe and Cd remained dissolved in the medium throughout their presence in the medium undergoing electrolysis in the cell. During 241 hours of electrolysis under these conditions, AN'
were converted to ADN with average and final selectivities of 89.3% and 89.0%, respectively, and the intra-cell voltage drop was stable at 3.9 volts, and the volume % of hydrogen in the electrolytically generated gas was on average 4.5%, and its final value is 5.4
It was %. Example × When an electrolytic medium essentially the same as Example K is electrolyzed for 36 hours under conditions essentially the same as Example K, the anode and cathode have a current of 0.13 per faraday through the medium.
An average rate such that 7 mmol of iron and 0.019 mmol of cadmium migrate into the medium (each approximately 0.01 mmol).
Corrosion occurred at a rate of 0 spots and 0.017 per year). And the iron and cadmium that migrated into the medium during electrolysis exceeded 4.9 mmol/night of medium during the first two hours of electrolysis. After the first 130 hours, the concentrations of iron and cadmium dissolved in the solution were 506-558 and 105-27, respectively, without any filtration of the circulating medium.
It was stable in the range of &mole (9.8-10.8 and 1.0-2.7 mmol/so). The concentration of insoluble heavy metals (essentially all iron) in the medium undergoing electrolysis is kept below 0.93 mmol/〆 and the iron and cadmium migrated into the medium during electrolysis is at least %, viz. F
e91.9Cd essentially 100% and total 94.1
% remained dissolved throughout their presence in the medium undergoing electrolysis. Under these conditions, AN is Iso. A with an average and final selectivity of 7% and 87.1%
DN' is converted, the voltage drop within the cell is stable at 3.9 volts, and the volume % of hydrogen in the evolved gas averages 7.2
% and the final value was 85%. For example, in the continuous method, '1' contains 1.3% to 1.6% AN, about 1.2% ADN, 4 to 10 x 10-3 mol/its ethyltributylammonium ion, 10% ortho A mixture of sodium phosphate and an aqueous solution of about 99% sodium phosphate prepared by neutralizing an amount of orthochloric acid equivalent to a 2% solution to a solution of 8.5% and ■ about 24% A liquid electrolytic medium consisting of approximately 1% of a dispersed but undissolved organic phase containing 30% AN, 54-60% ADN, 8% AN dimerization by-product and 8% water was added to 55 qo and 1.22/sec of cadmium (at least 99.9% Cd) is circulated through an undivided cell with a Yama SI I020 carbon steel anode spaced 0.178 C from the cathode; It was electrolyzed with a current density of 18.5 amps per anode or cathode surface ld while passing through the cell. separating the organic phase containing the product ADN, by-products and unreacted AN from the electrolytic medium and adding make-up AN;
The medium was then recycled through the cell and electrolyzed again under the conditions described. Initially, the medium contains dissolved iron and cadmium at concentrations of approximately 11.1 and 2.4 mmol/concentration, respectively, and the medium further contains up to (but not more than) 4.9 mmol/concentration of iron and/or cadmium. Tetrasodium ethylenediaminetetraacetate (Na4EDTA) in such a proportion that it can be dissolved.
) and its decomposition products. 0.495 mmol Na4E per faraday of current passing through the medium
Add DTA to the circulating medium and remove one solution from the system and add enough dissolved ethyltributylammonium and It was replaced with water containing sodium phosphate and sodium phosphate. Under these conditions, the anode and cathode move at an average rate such that 0.132 mmol of iron and 0.012 mmol of cadmium per faraday of such current migrate into the medium (approximately about 0.055 and 0.05 mmol, respectively).
010 skin/year> corroded. The iron and cadmium that migrated into the medium during electrolysis exceeded 4.9 mmol per medium during the first 31 hours of electrolysis. And the concentrations of iron and cadmium dissolved in the solution were 455-570 and 94-17 & palisade (8.8-11.
It was stable in the range of 0 and 0.9 to 1.7 mmol. If no circulating medium is suitable for the furnace after the first 19 anchor hours, the concentration of insoluble heavy metals (essentially or all iron) in the medium undergoing electrolysis is kept below 1.9 mmol/min, and the The iron and cadmium that migrated into the medium during
d essentially 100% and a total of 87.5% retained in solution throughout its presence in the electrolyzed medium. During the electrolysis of Terama for a total of 42 years under these conditions, A
N was converted to ADN with average and final selectivities of 88% and 87.1%, respectively, with an intra-cell voltage drop of 3.8
It was stable between 4 and 3.9 volts, and the volume percent hydrogen in the evolved gas averaged 10%, with a final value of 16.4%. COMPARATIVE EXAMPLE B An electrolytic medium was electrolyzed essentially according to example, except that Na4EDTA was added in an insufficient proportion to maintain substantially complete solution of the iron and cadmium that had migrated into the medium. After 6 hours of electrolysis, a large amount of solids accumulated in the circulating medium, the intra-cell voltage drop increased to 4.8 volts, and the volume percent hydrogen in the evolved gas increased to 10%. The electrodes were cleaned, the media was thoroughly filtered, and the process was restarted. However, after only 2 more minutes of electrolysis, a large amount of solids has again accumulated in the circulating medium and the cell voltage has again increased to 4.
．． increased to 8 volts, ADN selection rate decreased to approximately 2%,
The volume percentage of hydrogen in the generated gas rose to 17%.
For example, in the continuous cutting method, about 85.4% of '11.
7% AN, 1.2% ADN, 2-5 x 10-3 mol/
A mixture of ethyltributylammonium ion, 10% sodium orthophosphate, and sodium esterate prepared by neutralizing an amount of orthophosphoric acid equivalent to a 1.8% solution to a solution value of 8.5. About 85.4% dissolved aqueous solution and ■ about 31% AN dispersed but not dissolved, 53-54% ADN, 7
A liquid electrolytic medium consisting of about 14.6% organic phase containing ~8% AN dimerization byproduct and 8% water was charged with cadmium (at least 99%) at 5 g○ and at 1.22 units/sec.
9% Cd) circulated through an undivided cell with an AISI I020 carbon steel anode spaced 0.178 C from the cathode and 18.5 per anode or cathode surface ld as it passed through the cell. Electrolyzed at a current density of ampere. separating the organic phase containing the product ADN, by-products and unreacted AN from the electrolytic medium and adding make-up AN;
The medium was then recycled through the cell and electrolyzed again under the conditions described. Initially, the electrolytic medium was 9
．． 0 and 2.75 mmol/concentration of dissolved iron and cadmium and Na4EDTA and its decomposition products in such proportions that the medium can further dissolve (but not exceeding) 5.25 mmol/concentration of dissolved iron and cadmium. It contained. 0.4 mmol of Na4EDTA per faraday of current passing through the medium is added to the circulating medium, and a solution of 129 is removed from the system, maintaining the concentration of these components in the solution at said level and reducing the total volume of the medium. This was replaced with water containing enough dissolved ethyl tributyl ammonium ion and sodium orthophosphate and sodium chlorate to keep it constant. Under these conditions, the anode and cathode move at an average rate (
Corrosion occurred at approximately 0.050 and 0.007 k/year, respectively. and the iron and cadmium that migrated into the medium during electrolysis were
．． It exceeded 25 mmol/so. And the concentration of iron and cadmium dissolved in the solution is 465-490, respectively.
and 170-28 cervical flies (9-9.5 and ].6-2
．． The iron and cadmium which remained stable in the range of 8 mmol/s) and which migrated into the medium during electrolysis were found in examples m
It remained dissolved throughout its presence in the medium undergoing electrolysis at approximately the same percentage. 6 under these conditions
During the electrolysis, AN' was converted to ADN' with an average and final selectivity of 87.8%, and the voltage drop within the cell was 4.
It was stable below volts and the volume percent hydrogen in the evolved gas averaged 3-4% with a final value of 6%. Example x
m continuous method, between 85.9% and 87.5% [11
Among them, 1.4% to 1.6% AN and about 1.2% AD
N, 0.8-2.5 x 10-3 mol/ethyltriptylammonium ion, about 2% solution up to 9.6-9.9% sodium orthophosphate and 8.5-9 solution legs An aqueous solution of 85.9% to 87.5% and [2] 26 to 29% of AN, in which an aqueous solution is dissolved in a mixture with sodium chloride produced by neutralizing an amount of ortho-acid corresponding to 85.9% to 87.5% and Dispersed solution containing 54-59% ADN, 7-9% AN dimerization by-product and 8% water, consisting of 12.5%-14.1% organic phase. AISI I02 with a cadmium (at least 99.9% Cd) cathode separated by 0.228 skin spacing at 55° C. and 1.158 m/sec.
circulated through an undivided electrolytic cell having a zero carbon steel anode;
Electrolysis was then carried out at a current density of 20 amperes per anode or cathode surface ld while it passed through the cell. The organic phase containing the product ADN, by-products and reaction AN is separated from the electrolytic medium and supplementary AN is added, after which this medium is recycled to the cell and electrolyzed again under the conditions described herein. did. Initially the electrolytic medium is dissolved iron and cadmium at concentrations of 6.9 and 1.25 mmol/respectively and the medium is further added to 2.75 mmol/
It contained Na4EDTA and its decomposition products in a proportion sufficient to dissolve (but not more than) iron and/or cadmium. 0.475 mmol Na4ED per faraday of current passing through the medium
TA is added to the circulating medium and about 10 days of solution is removed from the system, and enough dissolved ethyl tributyl is added to maintain the solution components at the above levels, but to keep the total volume of the medium constant. It was replaced with water containing ammonium ion and sodium orthophosphate and sodium trusate. Under these conditions, and without any circulating medium, the anode and cathode are such that 0.12 mmol of iron and 0.014 mmol of cadmium migrate into the medium per faraday of such current. average speed (approximately 0.05 and 0.01 respectively)
The iron and cadmium which corrode at 2 hours/year) and migrate into the medium during electrolysis are more than 2.75 mmol per medium during the first 10 hours of electrolysis and dissolved in the solution. The iron and cadmium concentrations were 350 and 350, respectively.
It is stable in the range of ~550 and 130-16 strings (6.8-11.6 and 1.25-1.55 mmol/〆) and is stable in the range of insoluble heavy metals (essentially The concentration of iron and cadmium (all iron) remains below 2 mmolnok for at least 90% of the time, and the iron and cadmium that migrated into the medium during electrolysis are approximately the same % as in example m, and their presence in the medium undergoing electrolysis. Remained dissolved throughout. After electrolyzing for 2 total hours under these conditions, AN was converted to ADN with average and final selectivities of 87% and 2%, respectively, and the voltage drop per cell was stable at 4 volts,
The volume percentage of hydrogen in the generated gas was on average about 6.5%, and the final volume was 10.4%. The gist of the present invention and specific examples of embodiments are listed below. 1. In a process in which olefinic reactants are reductively coupled by electrolyzing a liquid aqueous medium containing the reactants and heavy metals are transferred into the medium in substantial amounts during the electrolysis, an excess of free sequestering agent is removed. An improvement comprising adding sufficient free heavy metal sequestering agent to the medium during electrolysis to cause the concentration of dissolved heavy metals in the medium to remain essentially stable. 2 The reaction component has the formula R2C=CR-× (in the formula, x is -CN,
-CONR2 or -COOR', R is hydrogen or R, and R' is C, ~C4 alkyl)
have. The method according to item 1 above. 3. The method according to item 2 above, wherein the capping agent added is an aminocarboxyl compound. 4. The method of claim 3, wherein the excess free sequestering agent is capable of sequestering at least about 2 mmol of heavy metal per medium. 5. The method of claim 2, wherein the heavy metal is iron and the added sequestering agent is capable of sequestering at least about 0.1 mmol of iron per faraday of current passing through the medium. 6. The method of claim 2, wherein acrylonitrile is the olefinic reactant and the liquid medium contains as its continuous phase an aqueous solution containing acrylonitrile, quaternary ammonium ions, and a conductive salt. 7. The liquid medium is in contact with the ferrous metal anode, and the added sequestering agent has at least about 1.5% of the iron transferred into the medium. The method according to the above-mentioned item 6, which includes an aminopolycarboxyl compound capable of blocking pharyngeal sounds. 8. Clause 7 above, wherein the added sequestering agent comprises at least about 0.1 mmole of a salt of ethylenediaminetetraacetic acid or N-hydroxyethylethylenediaminetriacetic acid per faraday of current passing through the medium. Method described. 9. The method of claim 7, wherein the medium is electrolyzed in contact with an essentially cadmium cathode. 10 The olefin reactants are reductively coupled by electrolyzing a liquid aqueous medium containing the reactants in an electrolytic zone, and the heavy metals are reduced during electrolysis to a substantially greater extent than is soluble in the initial electrolytic medium. free heavy metal sequestration sufficient to keep the heavy metals that migrate into the medium during electrolysis substantially completely dissolved throughout essentially the entire presence of the metal in the electrolytic zone, in such a manner that the heavy metals migrated into the medium in an amount that Improvements involving adding agents to the medium during electrolysis and keeping the concentration of dissolved heavy metals in the medium essentially stable. 11 The olefin reaction component has the formula R2C=CR-X, where x is -CN, -CONR2 or -COOR',
11. The method of claim 10, wherein R is hydrogen or R' and R' is C2-C4 alkyl. 12. The method of claim 11, wherein sufficient free heavy metal sequestering agent is added to the medium during electrolysis to maintain the concentration of insoluble heavy metals in the medium in the electrolysis zone at about 2 mmol/less or less. 13. The liquid aqueous medium containing the reactive components is in contact with an anode containing heavy metals that migrate into the medium during electrolysis in a substantially greater amount than is soluble in the initial electrolytic medium. The method according to paragraph 11. 14. Acrylonitrile is hydrogenated dimerized by electrolyzing a liquid medium containing an aqueous solution of acrylonitrile, quaternary ammonium ions and a conductive salt in contact with an electrode containing heavy metals as its continuous phase in an electrolytic band; The heavy metal is transferred into the medium during electrolysis in a substantially greater amount than is soluble in the initial electrolytic medium, and the electrolysis eliminates at least about 85% of the heavy metal transferred into the medium during electrolysis. 12. The method of claim 11, wherein sufficient free heavy metal sequestering agent is added to the medium during electrolysis to keep essentially all of the metal present in the zone dissolved in the medium. 15 The sequestering agent includes an aminocarboxyl compound and the concentration of heavy metal dissolved in the solution is from about 100 to about 25
The method according to the first paragraph, which is essentially stable between the 0Q sides. 16. The method of No. 1Q, supra, wherein the heavy metal is iron and the concentration of iron dissolved in the solution is essentially stable between about 4 and about 30 mmol/millimol/l. 17. Said first method wherein the electrode is a ferrous metal anode and the sequestering agent comprises a salt of ethylenediaminetetraacetic acid or N-hydroxyethylethylenediaminetriacetic acid.
Q How to write tribute. 18. The method of page 19, wherein the anode is essentially carbon steel and the cathode is essentially cadmium.

Claims (1)

[Claims] 1. In a method of electroreductive coupling of olefins in a liquid aqueous medium, polymerized metals that substantially migrate into the liquid medium from the surface of the electrolytic device in which the electrodes and the liquid aqueous medium come into contact during electrolysis are sequestered and added to the medium. adding to and into the medium an excess of free heavy metal sequestering agent sufficient to retain and maintain the heavy metals present in the medium substantially completely dissolved throughout the electrolytic zone; Olefin reduction method.