CA1050476A - Single-compartment electrolytic hydrodimerization process - Google Patents
Single-compartment electrolytic hydrodimerization processInfo
- Publication number
- CA1050476A CA1050476A CA232,364A CA232364A CA1050476A CA 1050476 A CA1050476 A CA 1050476A CA 232364 A CA232364 A CA 232364A CA 1050476 A CA1050476 A CA 1050476A
- Authority
- CA
- Canada
- Prior art keywords
- solution
- weight
- anode
- dis
- borate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B3/00—Electrolytic production of organic compounds
- C25B3/20—Processes
- C25B3/29—Coupling reactions
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
In a process for hydrodimerizing an olefinic nitrile, amide or ester by electrolyzing an aqueous solution of the olefinic compound and an alkali metal phosphate, borate or carbonate in a single-compartment cell with anode, corrosion being lessened by the use of a cell having an anode consisting essentially of carbon steel, there is provided the improvement of including in the aqueous solution quaternary phosphonium ions.
In a process for hydrodimerizing an olefinic nitrile, amide or ester by electrolyzing an aqueous solution of the olefinic compound and an alkali metal phosphate, borate or carbonate in a single-compartment cell with anode, corrosion being lessened by the use of a cell having an anode consisting essentially of carbon steel, there is provided the improvement of including in the aqueous solution quaternary phosphonium ions.
Description
~0504'76 This invention relates to an improvement in a single-compartment electrolytic hydrodimerization process.
Production of paraffinic dinitriles, dicarboxamides or dicarboxylates by electrolyic hydrodimerization of an alpha, beta-olefinic nitrile, carboxamide or carboxylate is well known, e.g. from u.S. Patents 3~193~475A79 and 3,193,481-83 issued July 6, 1965 to M. M. Baizer. Although the process has been sufficiently attractive that it has been in commercial use for over nine years, efforts to develop improvements thereon have been continued with particular emphasis on lowering elec-tric power costs and mitigating electrode corrosion and fouling tendencies because of which it has been heretofore commercially preferable to carry out the process with a cell divided by a cation-permeable membrane into separate anolyte and catholyte compartments. With the object o~ maintaining high electrolyte conductivity while employing a relatively low proportion of organic salts in the electrolysis medium, one approach to improvement of the process has been to carry out the electroly-sis in an aqueous solution of a mixture of quaternary ammonium and alkali metal salts together with the olefinic compound to be hydrodimerized.
An example of a process utilizing such an approach i is described in U.S. Patent 3,616,321 issued October 26, 1971, to Albert Verheyden et alO As described in that patent, adiponitrile is produced by electrolyzing an aqueous emulsion of acrylonitrile, an acidic alkali metal salt of a polyacid such as phosphoric acid and a surface-active substance such as a quaternary ammonium salt. According to that patent, selectivi-ties on the order of 75-~3% can be achieved when such a process is carried out in a single-compartment (undivided) cell having :, .
-~050~76 a graphite cathode and an iron or magnetite anode. However, corrosion of that type of anode proceeds at such a high rate that even with the use of an anode corrosion inhibitor such as an alkali metal pyrophosphate or metaphosphate, the process must be carried out at such low temperatures (preferably about 20C.) that expensive refrigeration of the electrolysis medium is required and at low enough current densities (typically less than 0.1 amp per square centimeter of anode surface area) that the productive capacity of such a cell is quite low. The suitability of other mate~rials (e.g. nickel, lead, lead dioxide, stainless steel and alloy steel) for use as the anode in similar processes has been suggested in U.S. Patent 3,511,765 issued May 12, 1970, to Fritz seck et al., U.S. Patent 3,630,861 issued December 28, 1971, to Jean Bizot et al. and U~S. Patent 3,689,382 issued September 5, 1972, to Homer M.
Fox et al. However, the materials just mentioned are likewise subject to relatively rapid corrosion when used as the anode in processes of the kind just mentioned.
To avoid the costs of using a cell-dividing membrane and for other reasons including those referred to hereinbefore, a process by which an olefinic nitrile, carboxamide or car-boxylate can be electrolytically hydrodimerized in an undivided I cell with high selectivity and a low rate of anode corrosion I is highly attractive for commercial use.
Thus, in accordance with this invention, there is i described the use of carbon steel as an anode in an undivided J cell wherein olefinic compounds are hydrodimerized to desired I hydrodimers, and wherein corrosion of the carbon steel anode J,~ iS inhibited by having present quaternary phosphonium ions in the aqueous solution of the olefinic compound containing .~ .
~050476 at least about 0.1% by weight of an alkali metal phosphate, borate or carbonate.
In the process of this invention, improved efficiencies in obtaining high yields of the desired hydrodimers and cor-rosion inhibition of the carbon steel anode can be obtained by having present in the aqueous solution mono-quaternary phosphonium ions, or divalent polymethylenebis(trialkylphos-phonium) ions.
Olefinic compounds that can be hydrodimerized by the process of this invention include those having the structural formula R2C=CR-X wherein -X is -CN, -CONR2 or -COOR', R is hydrogen or R' and R' is C1-C4 alkyl (i.e., methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl or tert-butyl). Com-pounds having that formula are known as having alpha-beta mono-unsaturation and in each such compound, at least one R
may be R' while at least one other R is hydrogen and at least one R', if present, may be an alkyl group containing a given number of carbon atoms while at least one other R', if present, ` is an alkyl group containing a different number of carbon atoms. Such compounds include olefinic nitriles such as, for example, acrylonitrile, methacrylonitrile, crotononitrile,
Production of paraffinic dinitriles, dicarboxamides or dicarboxylates by electrolyic hydrodimerization of an alpha, beta-olefinic nitrile, carboxamide or carboxylate is well known, e.g. from u.S. Patents 3~193~475A79 and 3,193,481-83 issued July 6, 1965 to M. M. Baizer. Although the process has been sufficiently attractive that it has been in commercial use for over nine years, efforts to develop improvements thereon have been continued with particular emphasis on lowering elec-tric power costs and mitigating electrode corrosion and fouling tendencies because of which it has been heretofore commercially preferable to carry out the process with a cell divided by a cation-permeable membrane into separate anolyte and catholyte compartments. With the object o~ maintaining high electrolyte conductivity while employing a relatively low proportion of organic salts in the electrolysis medium, one approach to improvement of the process has been to carry out the electroly-sis in an aqueous solution of a mixture of quaternary ammonium and alkali metal salts together with the olefinic compound to be hydrodimerized.
An example of a process utilizing such an approach i is described in U.S. Patent 3,616,321 issued October 26, 1971, to Albert Verheyden et alO As described in that patent, adiponitrile is produced by electrolyzing an aqueous emulsion of acrylonitrile, an acidic alkali metal salt of a polyacid such as phosphoric acid and a surface-active substance such as a quaternary ammonium salt. According to that patent, selectivi-ties on the order of 75-~3% can be achieved when such a process is carried out in a single-compartment (undivided) cell having :, .
-~050~76 a graphite cathode and an iron or magnetite anode. However, corrosion of that type of anode proceeds at such a high rate that even with the use of an anode corrosion inhibitor such as an alkali metal pyrophosphate or metaphosphate, the process must be carried out at such low temperatures (preferably about 20C.) that expensive refrigeration of the electrolysis medium is required and at low enough current densities (typically less than 0.1 amp per square centimeter of anode surface area) that the productive capacity of such a cell is quite low. The suitability of other mate~rials (e.g. nickel, lead, lead dioxide, stainless steel and alloy steel) for use as the anode in similar processes has been suggested in U.S. Patent 3,511,765 issued May 12, 1970, to Fritz seck et al., U.S. Patent 3,630,861 issued December 28, 1971, to Jean Bizot et al. and U~S. Patent 3,689,382 issued September 5, 1972, to Homer M.
Fox et al. However, the materials just mentioned are likewise subject to relatively rapid corrosion when used as the anode in processes of the kind just mentioned.
To avoid the costs of using a cell-dividing membrane and for other reasons including those referred to hereinbefore, a process by which an olefinic nitrile, carboxamide or car-boxylate can be electrolytically hydrodimerized in an undivided I cell with high selectivity and a low rate of anode corrosion I is highly attractive for commercial use.
Thus, in accordance with this invention, there is i described the use of carbon steel as an anode in an undivided J cell wherein olefinic compounds are hydrodimerized to desired I hydrodimers, and wherein corrosion of the carbon steel anode J,~ iS inhibited by having present quaternary phosphonium ions in the aqueous solution of the olefinic compound containing .~ .
~050476 at least about 0.1% by weight of an alkali metal phosphate, borate or carbonate.
In the process of this invention, improved efficiencies in obtaining high yields of the desired hydrodimers and cor-rosion inhibition of the carbon steel anode can be obtained by having present in the aqueous solution mono-quaternary phosphonium ions, or divalent polymethylenebis(trialkylphos-phonium) ions.
Olefinic compounds that can be hydrodimerized by the process of this invention include those having the structural formula R2C=CR-X wherein -X is -CN, -CONR2 or -COOR', R is hydrogen or R' and R' is C1-C4 alkyl (i.e., methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl or tert-butyl). Com-pounds having that formula are known as having alpha-beta mono-unsaturation and in each such compound, at least one R
may be R' while at least one other R is hydrogen and at least one R', if present, may be an alkyl group containing a given number of carbon atoms while at least one other R', if present, ` is an alkyl group containing a different number of carbon atoms. Such compounds include olefinic nitriles such as, for example, acrylonitrile, methacrylonitrile, crotononitrile,
2-methylenebutyronitrile, 2-pentenenitrile, 2-methylene-valeronitrile, 2-methylenehexanenitrile, tiglonitrile or 2-ethylidenehexanenitrile; olefinic carboxylates such as, for example, methyl acrylate, ethyl acrylate or ethyl crotonate;
- and olefinic carboxamides such as, for example, acrylamide, methacrylamide, N,N-diethylacrylamide or N,N-diethylcrotonamide.
Best results are generally obtained when the olefinic compound has at least one hydrogen atom directly attached to either of the two carbon atoms joined by the double bond ~ the aforedes-cribed structural formula. Also presently of greater utility ~ , .
~ - 3 -... . .
504'7~
in the process of this invention are those olefinic compounds where R' is methyl or eth~l, and particularly acrylonitrile, methyl acrylate and alpha-methyl acrylonitrile. Products of hydrodimerization of such compounds include those having the structural formula X-CHR-~R2-CR2-CHR-X wherein X and R have the aforesaid significance, i.e., paraffinic dinitriles such as, for example, adiponitrile and 2,5-dimethyladiponitrile;
paraffinic dicarboxylates such as, for example, dimethyladipate and diethyl-3,4-dimethyladipate; and paraffinic dicarboxamides such as, for example, adipamide, dimethyladipamide and N,N'-dimethyl-2,5-dimethyladipamide. Such hydrodimers can be em-ployed as monomers or as intermediates convertible by known processes into monomers useful in the manufacture of high molecular weight polymers including polyamides and polyesters.
The dinitriles, for example, can be hydrogenated by known processes to prepare paraffinic diamines especially useful in the production of high molecular weight polyamides.
Other examples of various olefinic compounds that can be hydro-dimerized by the process of this invention and the hydrodimers thereby produced are identified in the aforecited U.S. Patents
- and olefinic carboxamides such as, for example, acrylamide, methacrylamide, N,N-diethylacrylamide or N,N-diethylcrotonamide.
Best results are generally obtained when the olefinic compound has at least one hydrogen atom directly attached to either of the two carbon atoms joined by the double bond ~ the aforedes-cribed structural formula. Also presently of greater utility ~ , .
~ - 3 -... . .
504'7~
in the process of this invention are those olefinic compounds where R' is methyl or eth~l, and particularly acrylonitrile, methyl acrylate and alpha-methyl acrylonitrile. Products of hydrodimerization of such compounds include those having the structural formula X-CHR-~R2-CR2-CHR-X wherein X and R have the aforesaid significance, i.e., paraffinic dinitriles such as, for example, adiponitrile and 2,5-dimethyladiponitrile;
paraffinic dicarboxylates such as, for example, dimethyladipate and diethyl-3,4-dimethyladipate; and paraffinic dicarboxamides such as, for example, adipamide, dimethyladipamide and N,N'-dimethyl-2,5-dimethyladipamide. Such hydrodimers can be em-ployed as monomers or as intermediates convertible by known processes into monomers useful in the manufacture of high molecular weight polymers including polyamides and polyesters.
The dinitriles, for example, can be hydrogenated by known processes to prepare paraffinic diamines especially useful in the production of high molecular weight polyamides.
Other examples of various olefinic compounds that can be hydro-dimerized by the process of this invention and the hydrodimers thereby produced are identified in the aforecited U.S. Patents
3,193,475-79 and '481-83.
The invention may also be described in terms of electrol~zing an aqueous solution having dissolved therein certain proportions of the olefinic compound to be hydro-dimerized, quaternary phosphonium ions and an alkali metal phosphate, borate or carbonate. Such use of the term "aqueous solution" does not imply, however, that the electrolysis medium may not also contain an undissolved organic phase. To the contrary, the process of this invention can be carried out by electrolyzing the aqueous solution in an electrolysis lOS047~i medium containing the recited aqueous solution and a dis-persed but undissolved organic phase in any proportions at which the aqueous solution is the continuous phase of the electrolysis medium. Hence in some embodiments of the in-vention there may be suitably electrolyzed an aqueous solution containing essentially no undissolved organic phase, by which is meant either no measurable amount of undissolved organic phase or a minute proportion of undissolved organic phase having no significant effect on the hydrodimer selectivity achieved when the aqueous solution is electrolyzed in accordance with the process of this invention. Such a minute proportion, if present, would be typically less than 5% of the combined weight of the aqueous solution and the undissolved organic phase contained therein. In other embodiments, the invention can be carried out by electrolyzing the aqueous solution in an electrolysis medium consisting essentially of the recited aqueous solution and a dispersed but undissolved organic phase in a larger proportion te.g. up to about 15%, 20% or even more of the combined weight of the aqueous solution and the undissolved organic phase in the electrolysis medium) which may or may not significantly affect the hydrodimer selectivity depending on other conditions of the process. In some con-tinuous process embodiments involving recycle of unconverted olefinic compound and whether present in a minute or larger proportion, such an organic phase would be normally made up mainly (most commonly at least about 65% and even more typically at least about 75%~ of the olefinic compound to be hydrodimerized and the hydrodimer product with some minor amounts of organic hydrodimerization by-products, quaternary phosphonium ions, etc. possibly also present. Typically, such ~()5(~7t~
an organic phase contains at least about 10%, preferably between about 15~ and about 50%, and even more desirably between about 20% and about 40% of the olefinic compound to be hydrodimerized. In any event, however, the concentrations of the constituents dissolved in the aqueous solution to be electrolyzed as set forth in this specification and the - appended claims, are with reference to the recited aqueous solution alone and not the combined contents of said aqueous solution and an undissolved organic phase which, as aforesaid, may be present but need not be present in the electrolysis medium as the process of this invention is carried out. On the other hand, the weight percentages of undissolved organic phase described herein are based on the combined weight of the aqueous solution and the undissolved organic phase in the electrolysis medium.
Referring to the constituents of the aqueous phase, the olefinic compound to be hydrodimerized will be present in at least such a proportion that electrolysis of the solu-tion, as described herein, will result in a substantial amount of the desired hydrodimer being produced. That proportion is generally at least about 0.1% cf the aqueous solution, more typically at least about 0.5% of the aqueous solution and, in some embodiments of the invention, preferably at least about 1% of the aqueous solution. Inclusion of one or more additional constituents which increase the solubility of the olefinic compound in the solution may permit carrying out the process with the solution containing relatively high proportions of the olefinic compound, e.g. at least about 5~ or even 10%
or more, but in many embodiments of the invention, the aqueous solution contains less than about 5% (e.g. not more than ~%) of the olefinic compound and, in some of those embodiments, preferably not more than about 1.8% of the olefinic compound.
~()50~76 The minimum required proportion of quaternary phos-phonium ions is very small. In general, there need be only an amount sufficient to provide the desired hydrodimer selec-tivity (typically at least about 75%) although much higher proportions can be present if desired or convenient. In most cases, the quaternary phosphonium cations are present in a concentration of at least about 10 5 gram mol per liter of the aqueous solution. Even more typically their concentra-tion is at least about 10 gram mol per liter of the solution.
10 Although higher proportions may be present in some cases, as aforesaid, the quaternary phosphonium cations are generally present in the aqueous solutlon in a concentration not higher than about 0.5 gram mol per liter and even more usually, in a concentration not higher than about I0 l ~ra~ mol per liter.
In some preferred embodiments, the concentration of quaternary phosphonium ions in the solution is between about 10 4 and about 10 2 gram mol per liter.
The quaternary ions that are present in such concen-trations are those positively charged ions in which a phosphorus atom has a valence of five and is directly linked to other atoms (e.g. carbon3 satisfying four fifths of that valence. Such cations need contain only one penta-valent phosphorus atom but may contain more than one of such pentavalent atoms as in, e.g., various multivalent multi quaternary ions such as the bis-quaternary phosphonium ions referred to hereinafter. Suitable mono-quaternary ions may be cyclic, but they are more generally of the type in which a pentavalent phosphorus atom is directly linked to a total of four monovalent organic groups preferably devoid of olefinic 30 unsaturation and desirably selected from the group consisting of alkyl and aryl radicals and combinations thereof. Suitable , v ~, -- 7 --~05~)47~
multi-quaternary phosphonium i~ns may likewise by cyclic, and they are typically of a type in which the pentavalent phos-phorus atoms are linked to one another by at least one divalent organic (e.g. polymethylene) radical and each further substi-tuted by monovalent orsanic groups of the kind just mentioned sufficient in number tnormally two or three) that four fifths of the valence of each such pentavalent atom is satisfied by such divalent and monovalent organic radicals. As such mono-valent organic radicals, suitable aryl groups contain typically from six to twelve carbon atoms and preferably only one aromatic ring as in, for example, a phenyl or benzyl radical, and suitable alkyl groups can be straight-chain, branched or cyclic with each typically containing from one to twelve carbon atoms.
Although quaternary phosphonium cations containing a combina-tion of such alkyl and aryl groups (e.g. benzyltriethylphos-phonium) ions can be used, many embodiments of the invention are carried out with quaternary cations having no olefinic or aromatic unsaturation. Good results are generally obtained with tetraalkylphosphonium ions containing at least three C2-C6 alkyl groups and a total of from 8 to 24 carbon atoms in the four alkyl groups, e.g. tetraethyl-, ethyltripropyl-, ethyltributyl-, ethyltriamyl-, ethyltrihexyl-, octyltriethyl-, tetrapropyl-, methyltripropyl-, decyltripropyl-, methyltributyl-, tetrabutyl-, amyltributyl-, tetraamyl-, tetrahexyl-, ethyltri-hexyl-, diethyldioctyl -phosphonium and many others referred to in the aforecited U.S. Patents 3,193,475-79 and '481-83.
Generally most practical from the economic standpoint are those C8-C20 tetraalkylphosphonium ions containing at least ` three C2-C5 alkyl groups, e.g. methyltributyl-, tetrapropyl-, ethyltriamyl-, octyltriethylphosphonium,etc. Particularly ~- .
_ ~ _ -()47~
useful are the C8-C16 tetraalkylphosphonium ions containing at least three C2-C4 alkyl groups. Similarly good results are obtained by use of the divalent polymethylenebis(trialkyl-phosphonium) ions, particularly those containing a total of from 17 to 36 carbon atoms and in which each trialkylphosphoniu~
radical contalns at least two C3-C6 alkyl groups and the polymethylene radical is C3~C8, i.e., a straight chain of from three of eight methylene radicals. Presently most attractive from the economic standpoint are the C18-C32 polymethylenebis (trialkylphosphonium) ions in which each trialkylphosphonium radical contains at least two C3-C5 alkyl groups and the polymethylene radical is C4-C6. In many embodiments of the invention employing such polymethylenebis(trialkylphosphonium) ions, the carbon atom content of such ions is preferably from 20 to 34. Presently of specific interest for potential com-mercial use in the process of this invention are the C20-C34 hexamethylenebis(trialkylphosphonium) ions, e.g. those in which each trialkylphosphonium radical contains at least two C3-C6 alkyl groups. Also generally preferred are the hexamethylene-bis(trialkylphosphonium) ions containing from 20 to 30 carbon atoms, e.g. those in which each trialkylphosphonium radical contains at least two C3-C5 alkyl groups, and especially the C24-C30 hexamethylenebis(trialkylphosphonium) ions in which each trialkylphosphonium radical contains at least one and preferably two n-butyl groups. Any of such cations can be incorporated into the aqueous solution to be electrolyzed in any convenient manner, e.g. by dissolving the .
' : , ' ' . ~ - . ' ' ~ 050476 hydroxide or a salt (e.g. a Cl-C2 alkylsulfa~e) of the desired quaternary phosphonium cation(s) in the solution in the amount required to provide the desired concentration of such cations.
One significant advantage of the polymethylenebis (trialkylphosphonium) ions for use in the present invention is that relative to most of the corresponding tetraalkyl-phosphonium ions of the type described hereinbefore, they tend to distribute themselves in higher proportion toward the aqueous phase of a mixture of an aqueous solution of the type electrolyzed in accordance with the present invention and the undissolved organic phase which, as aforesaid, may be present in the aqueous solution during the electrolysis.
Whether or not such an organic phase is present in substan-tial proportion in the aqueous solution during the electroly-sis, product hydrodimer is generally most conveniently removed from the electrolyzed solution by adding to the solution (either before or after the electrolysis) an amount of the olefinic starting material in excess of its solubility therein, mixing the solution and the excess olefinic compound until they are substantially equi]ibrated, and then separating (e.g.
decanting) from the resulting mixture a first portion thereof that is richer than said mixture in the olefinic compound and therefore richer than said mixture in the hydrodimer product which is normally substantially more soluble in the olefinic compound than in the electrol-yzed aqueous solution. Normally, the hydrodimer product is separated from said first portion of the mixture (e.g. by distillation) while a second portion .
of the mixture comprisin~ an aqueous solution of the type subjected to electrolysis in accordancewith the present inven-tion is recycled and the aqueous solution comprised by said ~05~76 second portion is subjected to ~ore of such electrolysis. In process embodiments in which the hydrodimer product is separated from the electrolyzed solution in t~ manner just described and in view of the importance of having sufficient quaternary phosphonium cations in the aqueous solution to maintain a high hydrodimer selectivity on further electrolysis of the solution, the use of a quaternary cation that distributes itself in relatively high proportion in the a~ueous portion of a sub-stantially equilibrated mixture of the type just described is highly attractive from the standpoint of lessening the costs of recovering such cations from the separated (e.g. decanted) organic portion of the mixture and/or loss of such cations due to incomplete recovery from said organic portion of the mixture.
Surprisingly, and despite their generally higher carbon content, various bis-quaternary cations of the class defined herein-before have been found to distribute themselves toward the aqueous solution in ratios significantly higher ~e.g. up to at least 3-4 times high~r) than those of the corresponding mono-quaternary cations.
The alkali metal salts which can be employed in the invention are those of sodium, potassium, lithium, cesium and rubidium. Generally preferred for economic reasons are those of lithium and especially sodium and potassium. Also preferred for such use are the alkali metal salts of inorganic and/or polyvalent acids, e.g. an alkali metal orthophosphate, borate or carbonate, and particularly an incompletely-substituted salt of that type, i.e. a salt in which the anion has at least one valence satisfied by hydrogen and at least one other valenae satisfied by an alkali metal. Examples of such salts include disodium phosphate (Na2HPO4), potassium acid phosphate (KH2PO4), sodium bicarbonate (NaHCO3) and dipotassium borate (K2HBO3). Also useful are the alkali metal salts of condensed acids such as pyrophosphoric, metaphos-. .
.
. . . .- ,~ ,, ~ . .
I osoY ~6 phoric, metaboric, py~oborîc and the like (e.g. sodium pyrophosphate, potassium metaborate, etc.). Depending on the acidity of the aqueous solution to be electrolyzed, the stoi-chiometric proPortions of such anions and alkali metal cations in the solution may correspond to a mixture of two or more of such salts, e.g. a mixture of sodium acid phosphate and diso-dium phosphate, and accordingly, such mixtures of salts (as well as mixtures of salts of different alkali metals and/or -different acids) are intended to be within the scope of the expression "alkali metal phosphate, borate or carbonate" as used herein. In fact, it has been found that the rates of corrosion of the carbon steel anodes employed in the process of this invention are significantly and surprisingly lower when the electrolyzed solution has dissolved therein certain mi~tures of such salts including mostnotably an alkali metal phosphate and an alkali metal borate. Any of the alkali metal salts may be dissolved in the aqueous solution as such or otherwise, e.g. as the alkali metal hydroxide and the acid necessary to neutralize the hydroxide to the extent of the desired acidity of the aqueous solution.
The concentration of alkali metal salt in the solution should be at least sufficient to substantially increase the electrical conductivity of the solution above its conductivity without such a salt being present. In general, there is also enough alkali metal salt dissolved in i the solution to provide alkali metal cations constituting more than half of the total weight of all cations in the solution.
In most cases, the solution has dissolved therein at least about 0.1% of alkali metal salt. More advantageous conductivity levels are achieved when the solution has dissolved therein at least about 1% of alkali metal salt or, even more preferably, at least about 2% of such a salt. In many cases, optimum . ~
~ . . . .. ~ . . ~
~()S047~
process conditions include the solution having dissolved therein more than 5~ (typically at least 5.5~) of alkali metal salt. The maximum amount of alkali metal salt in the solution is limited only by its solubility therein, which varies with the particular salt employed. With salts such as sodium or potassium phosphates and/or borates, it is generally most convenient when the solution contains between about 1% and about 15% of such a salt or mixture thereof~ When the solution contains an alkali metal phosphate and an alkali metal borate, especially low rates of anode corrosion are normally achieved when the solution has dissolved therein at least about 0.5%
and preferably at least about 2% of alkali metal phosphate and at least about 0.25%, preferably at least about 0.5%
but in some cases desirably not more than about 4% of alkali metal borate.
The acidity of the solution is preferably such that a neutral or alkaline condition prevails at the cathode. Since there is normally an acidity gradient across the cell, pH
at the anode can be lower than seven, if desired. In most cases, however, pH of the overall solution is at least about five, preferably at least about six and most conveniently at least about seven. Also in most cases, the overall solution pH is not higher than about twelve, typically not higher than about eleven and, with the use of sodium or potassium phosphates and/or borates as the main conductive salts, generally not substantially higher than about ten.
The temperature of the solution may be at any level compatible with e~istence as such of the solution itself, i.e., above its freezing point b~t below its boiling point under the pressure employed. Good results can be achieved between about 5 and about 75C. or at even higher temperatures if pressures substantially above one atmosphere are employed. The optimum : . ~ . : , . . - , .
: . .
. , . .. . . ~:
- . . - . ~ . -. .
. .
~OSV~7~
temperature range will vary with the specific olefinic compound and hydrodimer, among other factors, but in hydrodimerization of acrylonitrile to adiponitrile, electrolysis temperatures of at least about 25 are usually preferred and those between about 40 and about 65C. are especially desirable. In fact, it is an important advantage of the present invention that it can be carried out at such relatively high temperatures without an economically intolerable rate of anode corrosion.
Although not necessary, a liquid-impermeable cathode is usually preferred. With the use of such a cathode, the aqueous solution to be electrolyzed is generally passed between the anode and cathode at a linear velocity with ~-reference to the adjacent electrode surface of at least about 0.6 meter per second and even more preferably between about 0.9 and about 2.44 meters per second although a solution velocity up to 6 meters per second or higher can be employed, if desired. The gap between the anode and cathode can be very narrow, e.g. about 1.0 millimeter or less, or as wide as 1.27 centimeters or even wider, but is usually most conven-iently of a width between about 1.5 and about 6.35 millimeters.
ff As is well-known, electrolytic hydrodimerization ofan olefinic compound having a formula as set forth herein-before must be carried out in contact with a cathodic surface 1 ~ ~
7 having a cathode potential sufficient for hydrodimerization ~' of that compound. In the process of this invention, the ., ~
3~ cathodic surface can be made of virtually any material at ¦ which such a cathode potential can be provided and which is not dissolved, corroded or fouled by the electrolysis medium at ~ an intolerable rate. In general, the process is most s ~ 30 desirably carried out with a cathode consisting essentially ;~ of cadmium, mercury, thallium, lead, zinc, tin (possibly not suitable with some nitrile starting materials) or graphite, .
:::
1a~5C~47~i by which is meant that the cathodic surface contains a high percenta~e ~yenerall~ at least about 95% and prefer~bly at least about 98%1 of one or a combination (e.g. an alloy) of two or more of such materials, but it may contain a small amount of one or more other constituents that do not alter the nature of the cathodic surface so as to prevent substantial realization of the advantages of the present invention, parti-cularly as describea herein. Such other constituents, if present, are desirably other materials having relatively high hydrogen overvoltages. Of particular preference are cathodes consisting essentially of cadmium, mercury, thallium, lead or an alloy of at least one of such metals, and especially cathodes consisting essentially of ca~mium.
Cathodes employed in this invention can be prepared by various techniques such as, for example, electroplating of the desired cathode material on a suitably-s~aped substrate of some other material, e.~. a metal having greater structural rigidity, or by chemically, thermally and/or mechanically bonding a layer of the cathode material to a similar substrate.
Alternatively, a plate, sheet, rod or any other suitable con-figuration consisting essentially of the desired cathode material may be used without such a substrate, if convenient.
As aforesaid, the process of this invention is carried out in an electrolytic cell having an anode consisting essen-tially of carbon steel. By that is meant that the portion of the positive pole of the cell that is in contact with the solution undergoing electrolysis consists essentially of a steel of a type conventionally recognized as a carbon steel and not as iron or an alloy steel or stainless steel. A
standard definition of carbon steel, provided by the American -Iron and Steel Institute (AISI) is as follows: "Carbon steel is classed as such when no minimum content is specified or ~, - 15 -105047~
guaranteed for aluminum, ch~omium, columbium, molybdenum, nickel, titanium, tungsten, vanadium or zirconium; when the minimum for copper does not exceed 0.40 percent; or when the maximum content specifi~d or guaranteed for any of the following elements does not exceed the percentages noted:
manganese 1.65, silicon 0.60, copper 0.60." Carbon steels of various compositions are listed in the 1000, 1100 and 1200 series of AISI and SAE standard steel composition numbers, many of which may be found on page 62 of Volume 1, Metals Hand-book, 8th Edition (1961) published by the American Society for Metals, Metals Park, Ohio. Carbon steels are readily distinguishable from steels conventionally known as alloy steels and listed in the 1300 and higher series of the aforementioned standard steel composition numbers, from the special alloy steels that are conventionally known as stainless steels and normally contain substantial (usually more than 0.5~) other metals such as nickel and/or chromium, and from commercially-pure iron which, by definition, contains not more than about 0.01% carbon. In general, the carbon steels that can be used as anode materials in the process of this invention contain between about 0.02% carbon (more typically at least about 0.05% carbon) and about 2% carbon. Normally, carbon steels such as those of the AISI and SAE 1000 series of standard steel composition numbers are preferred and those containing between about 0.1% and about 1.5% carbon are typically most desirable. Such proportions are expressed, of course, without reference to any constituents of the electroly-sis medium althou~h in operation of the process, certain of those constituents may become associated with the surface of the anode, either transiently or otherwise, so as to act as a part of the anodic surface in the sense of serving as the positive pole of the electrolytic cell. For example, in ~ ' ~050~76 some embodiments of the process r it may be desirable to include in the electrolysis medium a small amount (generally between about 0.01~ and about 3%) o~ an inhibitor of corrosion of the anode (e.g. an alkali metal salt of a condensed phosphoric acid, such as tetrasodium pyrophosphate or the like) and/or a similarly small amount of a heavy metal chelating agent ~e.g.
an alkali metal salt of a nitrilocarboxylic acid, such as tetrasodium ethylenediaminetetraacetate or -t~trapropionate, trisodium hydroxyethyleth~lenediaminetriacetate, trisodium nitrilotriacetate or the like) and one or both of the same may in some cases (generally in only very minor quantities) become so associated with the carbon steel anode surface.
In operation of the undivided cell, in which an anode and a cathode of the cell are simultaneously in direct physical contact with the solution being electrolyzed, each anode may be in the form of a plate, sheet, strip, rod or any other suitable configuration. In a preferred embodiment, the anode is a sheet of carbon steel closely spaced from and essentially parallel to a sheet-like cathode in the same cell. As typically used in the process of this invention, carbon steel anodes are relatively inexpensive, highly conductive, have good mechanical properties including excellent structural strength and, as aforesaid, corrode at a rate that is lower, to a surprisingly great degree, than the corrosion rate of anode materials previously suggested for similar use. The corrosion rate of the carbon steel anode is particularly and importantly lower at relatively high current densities, permitting much greater hydrodimer productivity in a cell having a given anode surface area in contact with the 3~ electrolysis medium and thereby available for passage of the electric current employed in the process of this inven~ion.
.. . . . ............................ . . .
- ~ . .. .
In yeneral, there is no minimum current density with which the present process can be carried out but economic considerations usually requ~re the use of a current density of at least about 0.01 and preferably at least about 0.05 amp per square centimeter (amp/cm2~ o~ the anode surface in contact with the solution being electrolyzed. Similar processes employing more readily corroded anodes have had to be generally carried out, as aforesaid, with current densities substantially lower than 0.1 amp/cm2 of such anode surface, but the present process can be very conveniently carried out with anode current densi-A~ ties of at least about 0.1 amp/cm2 and, usually even more desirably from an economic standpoint, with anode current densities of at least about 0.15 amp/cm~ or even much higher.
Although greater anode current densities may be practical in some instances, those employed in the present process are generally not higher than about 0.75 amp/cm2 and even more typically not higher than about 0.5 amp/cm of the anode surface area in contact with the solution being electrolyzed. -Depending on other process variables, anode current densities of not more than about 0.35 amp/cm2 may be preferred in some embodiments of the invention. However, the fact that any of the aforementioned anode current densities of at least ., " .
about 0.1, and particularly at least about 0.15 amp/cm can be advantageously employed in the process of this invention, and especially at temperatures higher than about 25C., e.g. from about 40 up to about 65C. or even higher, is very surprising in view of the much greater corrosion :::
~ of other anode materials such as iron, magnetite, etc., , ~::
,~ - 18 -, 105047~
in similar process use but under conditions generally con sidered far less corrosive, e.g. at much lower temperatures and/or anode current densities. As will be readily apparent, the use of carbon steel anodes having advantages of that magnitude in a process from which there are available hydrodimerization selectivities of at least about 75%, typically at least about 80% and commonly as high as 85~ or even higher has provided that process with a significant and unexpected commercial utility.
In addition, carbon steel does not contain substantial proportions of other metals (such as nickel, etc.) which are present in stainless and other alloy steels and which, if released into the electrolysis medium, e.g.
by corrosion of an anode containing such metals, may tend to plate out or otherwise become deposited on the cathode and thereon alter the nature of the cathodic surface so as to increase the generation of saturated starting material (e.g. propionitrile) at the expense of hydrodimer selectivity.
The following specific examples of the process of this invention are included for purposes of illustration only and do not imply any limitations on the scope of the invention. Also in the following Examples, acrylonitrile and adiponitrile are generally represented by AN and A~N, respectively.
.
-- lg --, : . . - . . . ~
~050476 EXAMPLE I
In a continuous process, a liquid electrolysis medium composed of about 99% by (1) an aqueous solution having dissolved therein between 1.4% and 1.6% AN, about 1.2% ADN, 10% of a mix-ture o~ sodium orthophosphates, 0.6-1.4 x 10 3 mol per liter of methyltribut~lphosphonium ions, about 0.5~ of Na4EDTA and the sodium borates produced by neutralizing orthoboric acid - in an amount corresponding to about 2% of the solution to the s.dution pH of about 8.5 and about 1% by (2) a dispersed but undissolved organic phase containing 27-29% AN, 54-58% ADN, 7-9% AN EHD byproducts and 8% water was circulated at 55C.
and 1.22 meters per second through an undivided electrolytic cell having an AISI 1020 carbon steel anode separated by a gap of 1.76 millimeters from a âadmium cathode composed of cadmium conforming to ASTM Designation B 440-66T (at least 99.9% Cd) and electrolyzed as it passed through the cell with a current density of 0.185 amp/cm of the surface of the anode (or cathode). Organic phase containing pxoduct ADN, , AN E~D byproducts and unreacted AN was separated from the i 20 electrolyzed medium and make-up AN was added after which the medium Was recirculated through the cell and electrolyzed again under the conditions just described. For each Faraday o~ current passed through the medium, 0.4 millimol of Na4EDTA was added to the circulating medium and about 12 grams ~ th solution were purged from the system and replaced with water containing sufficient dissolved methyltributylphosphonium ions and sodium orthophos~hates and borates to maintain the concentrations of those constituents of the solution at the aforedesc~ibed:levels and the total volume o~ the medium ,~ :30 essentlally constant. After 120 hours of electrolysis under , ....
: i ,: . :, .. , . ,..... ,, ;
1050~7~
those conditions, it was ~ound that AN had been converted to ADN with avera~e and ~inal selectivities of 88% and ~he steel anode had corroded at an average rate substantially lower than 0.5 millimeter per ~Par.
Although the rate of corrosion of the carbon steel anode is surprisingly low when the electrolysis medium contains an alkali metal phosphate but no alkali metal borate (e.g.
0.97 and 0.86 millimeter per year~, the rate of such corrosion is signi~icantly and even more surprisingly further lowered when the electrolysis medium contains an alkali metal phosphate and an alkali metal borate being no higher than 0.5 millimeter per year as shown in Example I.
EXAMPLE II
In processes essentially as described in Example I, except that the quaternary cations in the aqueous solution are any one or a mixture of those identified below instead of hexamethylenebis(ethyldibutylphosphonium) ions, the results, average and final selectivities of AN conversion to ADN and anodic surface corrosion, are substantially the , 20 same as those obtained in Example I.
Hexamethylenebis(tributylphosphonium) : Hexamethylenebis(amyldipropylphosphonium) Hexamethylenebis(tripropylphosphonium) Hexamethylenebis(methyldibutylphosphonium) Hexamethylenebis(ethyldihexylphosphonium) Hexamethylenebis(decyldiethylphosphonium) Pentamethylenebis(propyldibutylphosphonium) Pentamethylenebis(triamylphosphonium) Tetramethylenebis(ethyldibutylphosphonium) Tetramethylenebis(octyldipropylphosphonium) Heptamethylenebis(ethyldibutylphosphonium) . .
~05047~
EXAMPLE III
In processes essentially as described in Example I
except that the quaternary cations in the aqueous solution are any one or a mixture of those identified below instead of methyltributylphosphonium ion$, the results, average and final selectivities of AN conversion to ADN and anodic surface corrosion, are substantially the same as those obtained in Example I.
Amyltributylphosphonium Tetrapropylphosphonium Diethyldihexylphosphonium Decyltriethylphosphonium Propyltributylphosphonium Tetraamylphosphonium Ethyltributylphosphonium Octyltributylphosphonium Diethyldibutylphosphonium - 22 - :
The invention may also be described in terms of electrol~zing an aqueous solution having dissolved therein certain proportions of the olefinic compound to be hydro-dimerized, quaternary phosphonium ions and an alkali metal phosphate, borate or carbonate. Such use of the term "aqueous solution" does not imply, however, that the electrolysis medium may not also contain an undissolved organic phase. To the contrary, the process of this invention can be carried out by electrolyzing the aqueous solution in an electrolysis lOS047~i medium containing the recited aqueous solution and a dis-persed but undissolved organic phase in any proportions at which the aqueous solution is the continuous phase of the electrolysis medium. Hence in some embodiments of the in-vention there may be suitably electrolyzed an aqueous solution containing essentially no undissolved organic phase, by which is meant either no measurable amount of undissolved organic phase or a minute proportion of undissolved organic phase having no significant effect on the hydrodimer selectivity achieved when the aqueous solution is electrolyzed in accordance with the process of this invention. Such a minute proportion, if present, would be typically less than 5% of the combined weight of the aqueous solution and the undissolved organic phase contained therein. In other embodiments, the invention can be carried out by electrolyzing the aqueous solution in an electrolysis medium consisting essentially of the recited aqueous solution and a dispersed but undissolved organic phase in a larger proportion te.g. up to about 15%, 20% or even more of the combined weight of the aqueous solution and the undissolved organic phase in the electrolysis medium) which may or may not significantly affect the hydrodimer selectivity depending on other conditions of the process. In some con-tinuous process embodiments involving recycle of unconverted olefinic compound and whether present in a minute or larger proportion, such an organic phase would be normally made up mainly (most commonly at least about 65% and even more typically at least about 75%~ of the olefinic compound to be hydrodimerized and the hydrodimer product with some minor amounts of organic hydrodimerization by-products, quaternary phosphonium ions, etc. possibly also present. Typically, such ~()5(~7t~
an organic phase contains at least about 10%, preferably between about 15~ and about 50%, and even more desirably between about 20% and about 40% of the olefinic compound to be hydrodimerized. In any event, however, the concentrations of the constituents dissolved in the aqueous solution to be electrolyzed as set forth in this specification and the - appended claims, are with reference to the recited aqueous solution alone and not the combined contents of said aqueous solution and an undissolved organic phase which, as aforesaid, may be present but need not be present in the electrolysis medium as the process of this invention is carried out. On the other hand, the weight percentages of undissolved organic phase described herein are based on the combined weight of the aqueous solution and the undissolved organic phase in the electrolysis medium.
Referring to the constituents of the aqueous phase, the olefinic compound to be hydrodimerized will be present in at least such a proportion that electrolysis of the solu-tion, as described herein, will result in a substantial amount of the desired hydrodimer being produced. That proportion is generally at least about 0.1% cf the aqueous solution, more typically at least about 0.5% of the aqueous solution and, in some embodiments of the invention, preferably at least about 1% of the aqueous solution. Inclusion of one or more additional constituents which increase the solubility of the olefinic compound in the solution may permit carrying out the process with the solution containing relatively high proportions of the olefinic compound, e.g. at least about 5~ or even 10%
or more, but in many embodiments of the invention, the aqueous solution contains less than about 5% (e.g. not more than ~%) of the olefinic compound and, in some of those embodiments, preferably not more than about 1.8% of the olefinic compound.
~()50~76 The minimum required proportion of quaternary phos-phonium ions is very small. In general, there need be only an amount sufficient to provide the desired hydrodimer selec-tivity (typically at least about 75%) although much higher proportions can be present if desired or convenient. In most cases, the quaternary phosphonium cations are present in a concentration of at least about 10 5 gram mol per liter of the aqueous solution. Even more typically their concentra-tion is at least about 10 gram mol per liter of the solution.
10 Although higher proportions may be present in some cases, as aforesaid, the quaternary phosphonium cations are generally present in the aqueous solutlon in a concentration not higher than about 0.5 gram mol per liter and even more usually, in a concentration not higher than about I0 l ~ra~ mol per liter.
In some preferred embodiments, the concentration of quaternary phosphonium ions in the solution is between about 10 4 and about 10 2 gram mol per liter.
The quaternary ions that are present in such concen-trations are those positively charged ions in which a phosphorus atom has a valence of five and is directly linked to other atoms (e.g. carbon3 satisfying four fifths of that valence. Such cations need contain only one penta-valent phosphorus atom but may contain more than one of such pentavalent atoms as in, e.g., various multivalent multi quaternary ions such as the bis-quaternary phosphonium ions referred to hereinafter. Suitable mono-quaternary ions may be cyclic, but they are more generally of the type in which a pentavalent phosphorus atom is directly linked to a total of four monovalent organic groups preferably devoid of olefinic 30 unsaturation and desirably selected from the group consisting of alkyl and aryl radicals and combinations thereof. Suitable , v ~, -- 7 --~05~)47~
multi-quaternary phosphonium i~ns may likewise by cyclic, and they are typically of a type in which the pentavalent phos-phorus atoms are linked to one another by at least one divalent organic (e.g. polymethylene) radical and each further substi-tuted by monovalent orsanic groups of the kind just mentioned sufficient in number tnormally two or three) that four fifths of the valence of each such pentavalent atom is satisfied by such divalent and monovalent organic radicals. As such mono-valent organic radicals, suitable aryl groups contain typically from six to twelve carbon atoms and preferably only one aromatic ring as in, for example, a phenyl or benzyl radical, and suitable alkyl groups can be straight-chain, branched or cyclic with each typically containing from one to twelve carbon atoms.
Although quaternary phosphonium cations containing a combina-tion of such alkyl and aryl groups (e.g. benzyltriethylphos-phonium) ions can be used, many embodiments of the invention are carried out with quaternary cations having no olefinic or aromatic unsaturation. Good results are generally obtained with tetraalkylphosphonium ions containing at least three C2-C6 alkyl groups and a total of from 8 to 24 carbon atoms in the four alkyl groups, e.g. tetraethyl-, ethyltripropyl-, ethyltributyl-, ethyltriamyl-, ethyltrihexyl-, octyltriethyl-, tetrapropyl-, methyltripropyl-, decyltripropyl-, methyltributyl-, tetrabutyl-, amyltributyl-, tetraamyl-, tetrahexyl-, ethyltri-hexyl-, diethyldioctyl -phosphonium and many others referred to in the aforecited U.S. Patents 3,193,475-79 and '481-83.
Generally most practical from the economic standpoint are those C8-C20 tetraalkylphosphonium ions containing at least ` three C2-C5 alkyl groups, e.g. methyltributyl-, tetrapropyl-, ethyltriamyl-, octyltriethylphosphonium,etc. Particularly ~- .
_ ~ _ -()47~
useful are the C8-C16 tetraalkylphosphonium ions containing at least three C2-C4 alkyl groups. Similarly good results are obtained by use of the divalent polymethylenebis(trialkyl-phosphonium) ions, particularly those containing a total of from 17 to 36 carbon atoms and in which each trialkylphosphoniu~
radical contalns at least two C3-C6 alkyl groups and the polymethylene radical is C3~C8, i.e., a straight chain of from three of eight methylene radicals. Presently most attractive from the economic standpoint are the C18-C32 polymethylenebis (trialkylphosphonium) ions in which each trialkylphosphonium radical contains at least two C3-C5 alkyl groups and the polymethylene radical is C4-C6. In many embodiments of the invention employing such polymethylenebis(trialkylphosphonium) ions, the carbon atom content of such ions is preferably from 20 to 34. Presently of specific interest for potential com-mercial use in the process of this invention are the C20-C34 hexamethylenebis(trialkylphosphonium) ions, e.g. those in which each trialkylphosphonium radical contains at least two C3-C6 alkyl groups. Also generally preferred are the hexamethylene-bis(trialkylphosphonium) ions containing from 20 to 30 carbon atoms, e.g. those in which each trialkylphosphonium radical contains at least two C3-C5 alkyl groups, and especially the C24-C30 hexamethylenebis(trialkylphosphonium) ions in which each trialkylphosphonium radical contains at least one and preferably two n-butyl groups. Any of such cations can be incorporated into the aqueous solution to be electrolyzed in any convenient manner, e.g. by dissolving the .
' : , ' ' . ~ - . ' ' ~ 050476 hydroxide or a salt (e.g. a Cl-C2 alkylsulfa~e) of the desired quaternary phosphonium cation(s) in the solution in the amount required to provide the desired concentration of such cations.
One significant advantage of the polymethylenebis (trialkylphosphonium) ions for use in the present invention is that relative to most of the corresponding tetraalkyl-phosphonium ions of the type described hereinbefore, they tend to distribute themselves in higher proportion toward the aqueous phase of a mixture of an aqueous solution of the type electrolyzed in accordance with the present invention and the undissolved organic phase which, as aforesaid, may be present in the aqueous solution during the electrolysis.
Whether or not such an organic phase is present in substan-tial proportion in the aqueous solution during the electroly-sis, product hydrodimer is generally most conveniently removed from the electrolyzed solution by adding to the solution (either before or after the electrolysis) an amount of the olefinic starting material in excess of its solubility therein, mixing the solution and the excess olefinic compound until they are substantially equi]ibrated, and then separating (e.g.
decanting) from the resulting mixture a first portion thereof that is richer than said mixture in the olefinic compound and therefore richer than said mixture in the hydrodimer product which is normally substantially more soluble in the olefinic compound than in the electrol-yzed aqueous solution. Normally, the hydrodimer product is separated from said first portion of the mixture (e.g. by distillation) while a second portion .
of the mixture comprisin~ an aqueous solution of the type subjected to electrolysis in accordancewith the present inven-tion is recycled and the aqueous solution comprised by said ~05~76 second portion is subjected to ~ore of such electrolysis. In process embodiments in which the hydrodimer product is separated from the electrolyzed solution in t~ manner just described and in view of the importance of having sufficient quaternary phosphonium cations in the aqueous solution to maintain a high hydrodimer selectivity on further electrolysis of the solution, the use of a quaternary cation that distributes itself in relatively high proportion in the a~ueous portion of a sub-stantially equilibrated mixture of the type just described is highly attractive from the standpoint of lessening the costs of recovering such cations from the separated (e.g. decanted) organic portion of the mixture and/or loss of such cations due to incomplete recovery from said organic portion of the mixture.
Surprisingly, and despite their generally higher carbon content, various bis-quaternary cations of the class defined herein-before have been found to distribute themselves toward the aqueous solution in ratios significantly higher ~e.g. up to at least 3-4 times high~r) than those of the corresponding mono-quaternary cations.
The alkali metal salts which can be employed in the invention are those of sodium, potassium, lithium, cesium and rubidium. Generally preferred for economic reasons are those of lithium and especially sodium and potassium. Also preferred for such use are the alkali metal salts of inorganic and/or polyvalent acids, e.g. an alkali metal orthophosphate, borate or carbonate, and particularly an incompletely-substituted salt of that type, i.e. a salt in which the anion has at least one valence satisfied by hydrogen and at least one other valenae satisfied by an alkali metal. Examples of such salts include disodium phosphate (Na2HPO4), potassium acid phosphate (KH2PO4), sodium bicarbonate (NaHCO3) and dipotassium borate (K2HBO3). Also useful are the alkali metal salts of condensed acids such as pyrophosphoric, metaphos-. .
.
. . . .- ,~ ,, ~ . .
I osoY ~6 phoric, metaboric, py~oborîc and the like (e.g. sodium pyrophosphate, potassium metaborate, etc.). Depending on the acidity of the aqueous solution to be electrolyzed, the stoi-chiometric proPortions of such anions and alkali metal cations in the solution may correspond to a mixture of two or more of such salts, e.g. a mixture of sodium acid phosphate and diso-dium phosphate, and accordingly, such mixtures of salts (as well as mixtures of salts of different alkali metals and/or -different acids) are intended to be within the scope of the expression "alkali metal phosphate, borate or carbonate" as used herein. In fact, it has been found that the rates of corrosion of the carbon steel anodes employed in the process of this invention are significantly and surprisingly lower when the electrolyzed solution has dissolved therein certain mi~tures of such salts including mostnotably an alkali metal phosphate and an alkali metal borate. Any of the alkali metal salts may be dissolved in the aqueous solution as such or otherwise, e.g. as the alkali metal hydroxide and the acid necessary to neutralize the hydroxide to the extent of the desired acidity of the aqueous solution.
The concentration of alkali metal salt in the solution should be at least sufficient to substantially increase the electrical conductivity of the solution above its conductivity without such a salt being present. In general, there is also enough alkali metal salt dissolved in i the solution to provide alkali metal cations constituting more than half of the total weight of all cations in the solution.
In most cases, the solution has dissolved therein at least about 0.1% of alkali metal salt. More advantageous conductivity levels are achieved when the solution has dissolved therein at least about 1% of alkali metal salt or, even more preferably, at least about 2% of such a salt. In many cases, optimum . ~
~ . . . .. ~ . . ~
~()S047~
process conditions include the solution having dissolved therein more than 5~ (typically at least 5.5~) of alkali metal salt. The maximum amount of alkali metal salt in the solution is limited only by its solubility therein, which varies with the particular salt employed. With salts such as sodium or potassium phosphates and/or borates, it is generally most convenient when the solution contains between about 1% and about 15% of such a salt or mixture thereof~ When the solution contains an alkali metal phosphate and an alkali metal borate, especially low rates of anode corrosion are normally achieved when the solution has dissolved therein at least about 0.5%
and preferably at least about 2% of alkali metal phosphate and at least about 0.25%, preferably at least about 0.5%
but in some cases desirably not more than about 4% of alkali metal borate.
The acidity of the solution is preferably such that a neutral or alkaline condition prevails at the cathode. Since there is normally an acidity gradient across the cell, pH
at the anode can be lower than seven, if desired. In most cases, however, pH of the overall solution is at least about five, preferably at least about six and most conveniently at least about seven. Also in most cases, the overall solution pH is not higher than about twelve, typically not higher than about eleven and, with the use of sodium or potassium phosphates and/or borates as the main conductive salts, generally not substantially higher than about ten.
The temperature of the solution may be at any level compatible with e~istence as such of the solution itself, i.e., above its freezing point b~t below its boiling point under the pressure employed. Good results can be achieved between about 5 and about 75C. or at even higher temperatures if pressures substantially above one atmosphere are employed. The optimum : . ~ . : , . . - , .
: . .
. , . .. . . ~:
- . . - . ~ . -. .
. .
~OSV~7~
temperature range will vary with the specific olefinic compound and hydrodimer, among other factors, but in hydrodimerization of acrylonitrile to adiponitrile, electrolysis temperatures of at least about 25 are usually preferred and those between about 40 and about 65C. are especially desirable. In fact, it is an important advantage of the present invention that it can be carried out at such relatively high temperatures without an economically intolerable rate of anode corrosion.
Although not necessary, a liquid-impermeable cathode is usually preferred. With the use of such a cathode, the aqueous solution to be electrolyzed is generally passed between the anode and cathode at a linear velocity with ~-reference to the adjacent electrode surface of at least about 0.6 meter per second and even more preferably between about 0.9 and about 2.44 meters per second although a solution velocity up to 6 meters per second or higher can be employed, if desired. The gap between the anode and cathode can be very narrow, e.g. about 1.0 millimeter or less, or as wide as 1.27 centimeters or even wider, but is usually most conven-iently of a width between about 1.5 and about 6.35 millimeters.
ff As is well-known, electrolytic hydrodimerization ofan olefinic compound having a formula as set forth herein-before must be carried out in contact with a cathodic surface 1 ~ ~
7 having a cathode potential sufficient for hydrodimerization ~' of that compound. In the process of this invention, the ., ~
3~ cathodic surface can be made of virtually any material at ¦ which such a cathode potential can be provided and which is not dissolved, corroded or fouled by the electrolysis medium at ~ an intolerable rate. In general, the process is most s ~ 30 desirably carried out with a cathode consisting essentially ;~ of cadmium, mercury, thallium, lead, zinc, tin (possibly not suitable with some nitrile starting materials) or graphite, .
:::
1a~5C~47~i by which is meant that the cathodic surface contains a high percenta~e ~yenerall~ at least about 95% and prefer~bly at least about 98%1 of one or a combination (e.g. an alloy) of two or more of such materials, but it may contain a small amount of one or more other constituents that do not alter the nature of the cathodic surface so as to prevent substantial realization of the advantages of the present invention, parti-cularly as describea herein. Such other constituents, if present, are desirably other materials having relatively high hydrogen overvoltages. Of particular preference are cathodes consisting essentially of cadmium, mercury, thallium, lead or an alloy of at least one of such metals, and especially cathodes consisting essentially of ca~mium.
Cathodes employed in this invention can be prepared by various techniques such as, for example, electroplating of the desired cathode material on a suitably-s~aped substrate of some other material, e.~. a metal having greater structural rigidity, or by chemically, thermally and/or mechanically bonding a layer of the cathode material to a similar substrate.
Alternatively, a plate, sheet, rod or any other suitable con-figuration consisting essentially of the desired cathode material may be used without such a substrate, if convenient.
As aforesaid, the process of this invention is carried out in an electrolytic cell having an anode consisting essen-tially of carbon steel. By that is meant that the portion of the positive pole of the cell that is in contact with the solution undergoing electrolysis consists essentially of a steel of a type conventionally recognized as a carbon steel and not as iron or an alloy steel or stainless steel. A
standard definition of carbon steel, provided by the American -Iron and Steel Institute (AISI) is as follows: "Carbon steel is classed as such when no minimum content is specified or ~, - 15 -105047~
guaranteed for aluminum, ch~omium, columbium, molybdenum, nickel, titanium, tungsten, vanadium or zirconium; when the minimum for copper does not exceed 0.40 percent; or when the maximum content specifi~d or guaranteed for any of the following elements does not exceed the percentages noted:
manganese 1.65, silicon 0.60, copper 0.60." Carbon steels of various compositions are listed in the 1000, 1100 and 1200 series of AISI and SAE standard steel composition numbers, many of which may be found on page 62 of Volume 1, Metals Hand-book, 8th Edition (1961) published by the American Society for Metals, Metals Park, Ohio. Carbon steels are readily distinguishable from steels conventionally known as alloy steels and listed in the 1300 and higher series of the aforementioned standard steel composition numbers, from the special alloy steels that are conventionally known as stainless steels and normally contain substantial (usually more than 0.5~) other metals such as nickel and/or chromium, and from commercially-pure iron which, by definition, contains not more than about 0.01% carbon. In general, the carbon steels that can be used as anode materials in the process of this invention contain between about 0.02% carbon (more typically at least about 0.05% carbon) and about 2% carbon. Normally, carbon steels such as those of the AISI and SAE 1000 series of standard steel composition numbers are preferred and those containing between about 0.1% and about 1.5% carbon are typically most desirable. Such proportions are expressed, of course, without reference to any constituents of the electroly-sis medium althou~h in operation of the process, certain of those constituents may become associated with the surface of the anode, either transiently or otherwise, so as to act as a part of the anodic surface in the sense of serving as the positive pole of the electrolytic cell. For example, in ~ ' ~050~76 some embodiments of the process r it may be desirable to include in the electrolysis medium a small amount (generally between about 0.01~ and about 3%) o~ an inhibitor of corrosion of the anode (e.g. an alkali metal salt of a condensed phosphoric acid, such as tetrasodium pyrophosphate or the like) and/or a similarly small amount of a heavy metal chelating agent ~e.g.
an alkali metal salt of a nitrilocarboxylic acid, such as tetrasodium ethylenediaminetetraacetate or -t~trapropionate, trisodium hydroxyethyleth~lenediaminetriacetate, trisodium nitrilotriacetate or the like) and one or both of the same may in some cases (generally in only very minor quantities) become so associated with the carbon steel anode surface.
In operation of the undivided cell, in which an anode and a cathode of the cell are simultaneously in direct physical contact with the solution being electrolyzed, each anode may be in the form of a plate, sheet, strip, rod or any other suitable configuration. In a preferred embodiment, the anode is a sheet of carbon steel closely spaced from and essentially parallel to a sheet-like cathode in the same cell. As typically used in the process of this invention, carbon steel anodes are relatively inexpensive, highly conductive, have good mechanical properties including excellent structural strength and, as aforesaid, corrode at a rate that is lower, to a surprisingly great degree, than the corrosion rate of anode materials previously suggested for similar use. The corrosion rate of the carbon steel anode is particularly and importantly lower at relatively high current densities, permitting much greater hydrodimer productivity in a cell having a given anode surface area in contact with the 3~ electrolysis medium and thereby available for passage of the electric current employed in the process of this inven~ion.
.. . . . ............................ . . .
- ~ . .. .
In yeneral, there is no minimum current density with which the present process can be carried out but economic considerations usually requ~re the use of a current density of at least about 0.01 and preferably at least about 0.05 amp per square centimeter (amp/cm2~ o~ the anode surface in contact with the solution being electrolyzed. Similar processes employing more readily corroded anodes have had to be generally carried out, as aforesaid, with current densities substantially lower than 0.1 amp/cm2 of such anode surface, but the present process can be very conveniently carried out with anode current densi-A~ ties of at least about 0.1 amp/cm2 and, usually even more desirably from an economic standpoint, with anode current densities of at least about 0.15 amp/cm~ or even much higher.
Although greater anode current densities may be practical in some instances, those employed in the present process are generally not higher than about 0.75 amp/cm2 and even more typically not higher than about 0.5 amp/cm of the anode surface area in contact with the solution being electrolyzed. -Depending on other process variables, anode current densities of not more than about 0.35 amp/cm2 may be preferred in some embodiments of the invention. However, the fact that any of the aforementioned anode current densities of at least ., " .
about 0.1, and particularly at least about 0.15 amp/cm can be advantageously employed in the process of this invention, and especially at temperatures higher than about 25C., e.g. from about 40 up to about 65C. or even higher, is very surprising in view of the much greater corrosion :::
~ of other anode materials such as iron, magnetite, etc., , ~::
,~ - 18 -, 105047~
in similar process use but under conditions generally con sidered far less corrosive, e.g. at much lower temperatures and/or anode current densities. As will be readily apparent, the use of carbon steel anodes having advantages of that magnitude in a process from which there are available hydrodimerization selectivities of at least about 75%, typically at least about 80% and commonly as high as 85~ or even higher has provided that process with a significant and unexpected commercial utility.
In addition, carbon steel does not contain substantial proportions of other metals (such as nickel, etc.) which are present in stainless and other alloy steels and which, if released into the electrolysis medium, e.g.
by corrosion of an anode containing such metals, may tend to plate out or otherwise become deposited on the cathode and thereon alter the nature of the cathodic surface so as to increase the generation of saturated starting material (e.g. propionitrile) at the expense of hydrodimer selectivity.
The following specific examples of the process of this invention are included for purposes of illustration only and do not imply any limitations on the scope of the invention. Also in the following Examples, acrylonitrile and adiponitrile are generally represented by AN and A~N, respectively.
.
-- lg --, : . . - . . . ~
~050476 EXAMPLE I
In a continuous process, a liquid electrolysis medium composed of about 99% by (1) an aqueous solution having dissolved therein between 1.4% and 1.6% AN, about 1.2% ADN, 10% of a mix-ture o~ sodium orthophosphates, 0.6-1.4 x 10 3 mol per liter of methyltribut~lphosphonium ions, about 0.5~ of Na4EDTA and the sodium borates produced by neutralizing orthoboric acid - in an amount corresponding to about 2% of the solution to the s.dution pH of about 8.5 and about 1% by (2) a dispersed but undissolved organic phase containing 27-29% AN, 54-58% ADN, 7-9% AN EHD byproducts and 8% water was circulated at 55C.
and 1.22 meters per second through an undivided electrolytic cell having an AISI 1020 carbon steel anode separated by a gap of 1.76 millimeters from a âadmium cathode composed of cadmium conforming to ASTM Designation B 440-66T (at least 99.9% Cd) and electrolyzed as it passed through the cell with a current density of 0.185 amp/cm of the surface of the anode (or cathode). Organic phase containing pxoduct ADN, , AN E~D byproducts and unreacted AN was separated from the i 20 electrolyzed medium and make-up AN was added after which the medium Was recirculated through the cell and electrolyzed again under the conditions just described. For each Faraday o~ current passed through the medium, 0.4 millimol of Na4EDTA was added to the circulating medium and about 12 grams ~ th solution were purged from the system and replaced with water containing sufficient dissolved methyltributylphosphonium ions and sodium orthophos~hates and borates to maintain the concentrations of those constituents of the solution at the aforedesc~ibed:levels and the total volume o~ the medium ,~ :30 essentlally constant. After 120 hours of electrolysis under , ....
: i ,: . :, .. , . ,..... ,, ;
1050~7~
those conditions, it was ~ound that AN had been converted to ADN with avera~e and ~inal selectivities of 88% and ~he steel anode had corroded at an average rate substantially lower than 0.5 millimeter per ~Par.
Although the rate of corrosion of the carbon steel anode is surprisingly low when the electrolysis medium contains an alkali metal phosphate but no alkali metal borate (e.g.
0.97 and 0.86 millimeter per year~, the rate of such corrosion is signi~icantly and even more surprisingly further lowered when the electrolysis medium contains an alkali metal phosphate and an alkali metal borate being no higher than 0.5 millimeter per year as shown in Example I.
EXAMPLE II
In processes essentially as described in Example I, except that the quaternary cations in the aqueous solution are any one or a mixture of those identified below instead of hexamethylenebis(ethyldibutylphosphonium) ions, the results, average and final selectivities of AN conversion to ADN and anodic surface corrosion, are substantially the , 20 same as those obtained in Example I.
Hexamethylenebis(tributylphosphonium) : Hexamethylenebis(amyldipropylphosphonium) Hexamethylenebis(tripropylphosphonium) Hexamethylenebis(methyldibutylphosphonium) Hexamethylenebis(ethyldihexylphosphonium) Hexamethylenebis(decyldiethylphosphonium) Pentamethylenebis(propyldibutylphosphonium) Pentamethylenebis(triamylphosphonium) Tetramethylenebis(ethyldibutylphosphonium) Tetramethylenebis(octyldipropylphosphonium) Heptamethylenebis(ethyldibutylphosphonium) . .
~05047~
EXAMPLE III
In processes essentially as described in Example I
except that the quaternary cations in the aqueous solution are any one or a mixture of those identified below instead of methyltributylphosphonium ion$, the results, average and final selectivities of AN conversion to ADN and anodic surface corrosion, are substantially the same as those obtained in Example I.
Amyltributylphosphonium Tetrapropylphosphonium Diethyldihexylphosphonium Decyltriethylphosphonium Propyltributylphosphonium Tetraamylphosphonium Ethyltributylphosphonium Octyltributylphosphonium Diethyldibutylphosphonium - 22 - :
Claims (25)
1. In a process for hydrodimerizing an olefinic com-pound having the formula R2C=CR-X wherein -X is -CN, -CONR2 or -COOR', R is hydrogen or R' and R' is C1-C4 alkyl, which process comprises electrolyzing an aqueous solution having dissolved therein at least about 0.1% by weight of said ole-finic compound and at least about 0.1% by weight of alkali metal phosphate, borate or carbonate in a single-compartment cell having an anode consisting essentially of carbon steel, having between about 0.02% and about 2% by weight of carbon, the improvement wherein said solution includes quaternary phos-phonium cations in a concentration of at least about 10-5 gram mol per liter.
2. A process for hydrodimerizing an olefinic compound having the formula R2C=CR-X wherein -X is -CN, -CONR2 or -COOR', R is hydrogen or R', R' is C1-C4 alkyl and at least one R directly attached to either of the two carbon atoms joined by the double bond in said formula is hydrogen which comprises electrolyzing an aqueous solution having dissolved therein at least about 0.1% by weight of said olefinic compound, mono-quaternary phosphonium or multivalent, multi-quaternary phos-phonium ion in a concentration between about 10-5 and about 0.5 gram mol per liter and at least about 0.1% by weight of alkali metalphosphate, borate or carbonate in an undivided cell having an anode consisting essentially of carbon steel, having between about 0.02% and about 2% by weight of carbon.
3. The process of claim 1 or 2, said solution having dissolved therein less than about 5% by weight of said olefinic compound.
4. The process of claim 1 or 2, said solution having dissolved therein more than 5% by weight of the alkali metal phosphate, borate or carbonate.
5. The process of claim 1 or 2, said solution having dissolved therein less than about 5% by weight of olefinic compound.
6. The process of claim 2, said solution having dis-solved therein at least about 0.5% by weight of said olefinic compound, between about 10-5 and about 10-1 gram mol per liter of C17-C36 polymethylenebis(trialkylphosphonium) ions in which each trialkylphosphonium radical contains at least two C3-C6 alkyl groups and the polymethylene radical is C3-C8 and at least about 1% by weight of the alkali. metal phosphate, borate or carbonate.
7. The process of claim 6, said solution having dis-solved therein less than about 5% by weight of said olefinic compound.
8. The process of claim 2, said solution having dis-solved therein at least about 0.5% by weight of said olefinic compound, between about 10-5 and about 10-1 gram mol per liter of C8-C24 tetraalkylphosphonium ions containing at least three C2-C6 alkyl groups and at least about 1% of the alkali metal phosphate, borate or carbonate.
9. The process of claim 8, said solution having dis-solved therein less than 5% by weight of said olefinic compound.
10. A process for preparing adiponitrile which comprises electrolyzing an aqueous solution having dissolved therein at least about 0.5% by weight of acrylonitrile, between about 10-5 and about 10-1 gram mol per liter of quaternary phospho-nium ions and at least about 1% by weight of sodium or potas-sium salt selected from the group consisting of phosphate, borate and carbonate in an undivided cell having an anode con-sisting essentially of carbon steel, having between about 0.02 and about 2% by weight of carbon, with a current density of at least about 0.01 amp/cm2 of the surface of said anode in con-tact with the solution, said solution having a pH of at least about 5 and a temperature between about 5° and about 75°C.
11. The process of claim 10, said solution having dis-solved therein less than about 5% by weight of acrylonitrile.
12. The process of claim 11, said solution having dis-solved therein between about 10 5 and about 10 2 gram mol per liter of C8-C24 tetraalkylphosphonium ions containing at least three C2-C6 alkyl groups.
13. The process of claim 10, said solution having dis-solved therein more than 5% by weight of the sodium or potassium salt.
14. A process for preparing adiponitrile which comprises electrolyzing an aqueous solution having dissolved therein between about 1% and about 4% by weight of acrylonitrile, be-tween about 10-4 and about 10-1 gram mol per liter of C17-C36 polymethylenebis(trialkylphosphonium) ions in which each tri-alkylphosphonium radical contains at least two C3-C6 alkyl groups and the polymethylene radical is C3-C8 and at least about 1% by weight of sodium or potassium salt selected from the group consisting of phosphate and borate in an undivided cell having an anode consisting essentially of carbon steel, having between about 0.02% and about 2% by weight of carbon, with a current density between about 0.05 and about 0.5 amp/
cm2 of the surface of said anode in contact with the solution, said solution having a pH of at least about 6 and temperature between about 25° and about 65°C.
cm2 of the surface of said anode in contact with the solution, said solution having a pH of at least about 6 and temperature between about 25° and about 65°C.
15. The process of claim 14, said solution having dis-solved therein more than 5% by weight of the sodium or potas-sium salt.
16. The process of claim 14, wherein the solution is electrolyzed with a current density of at least about 0.1 amp/cm2 of said surface, said solution having a pH between about 7 and about 11 and a temperature of at least about 40°C.
17. The process of claim 14, wherein the aqueous solu-tion is electrolyzed in an electrolysis medium consisting essentially of said solution and up to about 20% by weight of an undissolved organic phase.
18. A process for hydrodimerizing an olefinic compound having the formula R2C=CR-X wherein -X is -CN, -CONR2 or COOR', R is hydrogen or R', R' is C1-C4 alkyl and at least one R directly attached to either of the two carbon atoms joined by the double bond in said formula is hydrogen which com-prises electrolyzing an aqueous solution having dissolved therein at least about 0.1% by weight of said olefinic compound, monoquaternary phosphonium cations or multivalent, multi-quaternary phosphonium cations in a concentration between about 10-5 and about 0.5 gram mol per liter, at least about 0.5% by weight of alkali metal phosphate and at least about 0.25% by weight of an alkali metal borate in an undivided cell having an anode consisting essentially of carbon steel, having between about 0.02% and about 2% by weight of carbon, with a current density of at least about 0.05 amp/cm2 of the surface of said anode in contact with the solution, said solution having a pH
of at least about 6 and a temperature between about 25° and about 75°.
of at least about 6 and a temperature between about 25° and about 75°.
19. The process of claim 17, said solution having dis-solved therein between about 0.5% and about 4% by weight of an alkali metal borate.
20. The process of claim 18, said solution having dis-solved therein between about 10-5 and about 10-1 gram mol per liter of C17-C36 polymethylenebis(trialkylphosphonium) ions in which each trialkylphosphonium radical contains at least two C3-C6 alkyl groups and the polymethylene radical is C3-C8.
21. The process of claim 20, said solution having dis-solved therein between about 0.5% and about 4% by weight of alkali metal borate.
22. The process of claim 20, wherein the solution is electrolyzed with a current density of at least about 0.1 amp/cm of the surfaceof said anode in contact with the solution, said solution having a pH between about 7 and about 10 and a temperature be-tween about 40° and about 65°C.
23. The process of claim 22, said solution having dis-solved therein at least about 0.5% but less than about 5% of said olefinic compound, between about 0.5% and about 4% by weight of sodium or potassium borate and at least about 2% by weight of sodium or potassium-phosphate.
24. The process of claim 23, said solution having dis-solved therein between about 10-4 and about 10-2 gram mol per liter of said tetraalkylphosphonium ions.
25. The process of claim 24, wherein the olefinic com-pound is acrylonitrile.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US497800A US3897318A (en) | 1973-08-06 | 1974-08-15 | Single-compartment electrolytic hydrodimerization process |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1050476A true CA1050476A (en) | 1979-03-13 |
Family
ID=23978364
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA232,364A Expired CA1050476A (en) | 1974-08-15 | 1975-07-28 | Single-compartment electrolytic hydrodimerization process |
Country Status (3)
| Country | Link |
|---|---|
| BR (1) | BR7504825A (en) |
| CA (1) | CA1050476A (en) |
| GB (1) | GB1477783A (en) |
-
1975
- 1975-07-28 GB GB3145675A patent/GB1477783A/en not_active Expired
- 1975-07-28 BR BR7504825*A patent/BR7504825A/en unknown
- 1975-07-28 CA CA232,364A patent/CA1050476A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB1477783A (en) | 1977-06-29 |
| BR7504825A (en) | 1976-08-03 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP0270390B1 (en) | A method for producing adiponitrile | |
| IL32339A (en) | Process for the production of adiponitrile | |
| CA1098074A (en) | Electrohydrodimerization process improvement and improved electrolyte recovery process | |
| CA1050476A (en) | Single-compartment electrolytic hydrodimerization process | |
| US3897318A (en) | Single-compartment electrolytic hydrodimerization process | |
| US3898140A (en) | Electrolytic hydrodimerization process improvement | |
| US3960679A (en) | Process for hydrodimerizing olefinic compounds | |
| CA1067450A (en) | Process for hydrodimerizing olefinic compounds | |
| US4306949A (en) | Electrohydrodimerization process | |
| US3966566A (en) | Electrolytic hydrodimerization process improvement | |
| Wendt | The Reactivity of Primary Free Radicals and Radical Ions, Mass Transfer, and Electrosorption—The Fundamental Factors for Selectivity in Electrochemical Syntheses of Organic Compounds | |
| CA1039230A (en) | Single-compartment electrolytic hydrodimerization process | |
| US3919057A (en) | Process for the electrochemical fluorination of organic acid halides | |
| US4046651A (en) | Electrolytic hydrodimerization process improvement | |
| CA1051819A (en) | Electrolytic hydrodimerization of acrylonitrile using a nitrilocarboxylic acid compound | |
| CA1039229A (en) | Process for hydrodimerizing olefinic compounds | |
| CA1039233A (en) | Reductive coupling process improvement | |
| US3193483A (en) | Electrolysis of acrylamides | |
| US4157286A (en) | Production of 1,2-bis(hydroxyphenyl)ethane-1,2-diols by electrolytic reduction | |
| CA1039231A (en) | Electrolytic hydrodimerization process improvement | |
| JPS6227583A (en) | Method for electrolytically dimerizing acrylonitrile | |
| DE2344294C3 (en) | Process for the hydrodimerization of an olefin compound | |
| US3556961A (en) | Electrolytic hydrodimerisation | |
| Weinberg et al. | Electrohydrodimerization: Comparison of Acrylonitrile and Formaldehyde | |
| Cipris | Electrochemical Synthesis of N‐Alkylformamides |