US3795694A - Preparation of cyano compounds - Google Patents

Abstract

THE PRESENT INVENTION IS CONCERNED WITH AN IMPROVED METHOD FOR THE PREPARATION OF AN ADIPONITRILE PRECURSOR AND ESPECIALLY TO THE PRODUCTION OF 1,4-DICYANOBUTENES FROM 2-METHYLENE GLUTARONITRILE IN ONE OR MORE PROCESSING STEPS, THUS PROVIDING A CONVENIENT OVERALL PROCESS WHEREBY ADIPONIRILE MAY BE PREPARED WITH A HIGH DEGREE OF EFFICIENCY STARTING WITH ACRYLONITRILE AS THE BASIC BEGINNING MATERIAL. ADDITIONAL ASPECTS OF THIS INVENTION INCLUDE FORMATION OF 1,2,4-TRICYANOBUTANE FROM 2-METHYLENE GLUTARONITRILE BY HYDROGEN CYANIDE ADDITION AND DEHYDROCYANATION OF 1,2,4-TRICYANOBUTANE.

Description

United States Patent 3,795,694 PREPARATION OF CYANO COMPOUNDS Olav Torgeir Onsager, Sulfern, N.Y., assignor to Halcon International, Inc.

No Drawing. Continuation-impart of applications Ser. No. 198,987, Nov. 15, 1971, Ser. No. 285,271 and Ser. No. 285,272, both Aug. 31, 1972, and Ser. No. 286,784, Sept. 6, 1972. This application Oct. 16, 1972, Ser. No. 298,115

Int. Cl. C07c 121/02, 04

US. Cl. 260-465.8 R 18 Claims ABSTRACT OF THE DISCLOSURE CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of co-pending applications, Ser. Nos. 198,987, filed Nov. 15, 1971; 285,- 271 and 285,272, both filed Aug. 31, 1972; and 286,784, filed Sept. 6, 1972.

This invention relates to a method for the production of 1,4-dicyanobutenes which are valuable intermediates in the production of adiponitrile.

Adiponitrile is a chemical of very great commercial importance since it can be conveniently converted into hexamethylene diamine, the latter being of course a component of nylon 6,6. With the developments made in the field of acrylonitrile production, acrylonitrile has become available in quantities and at a price which makes this material quite suitable as a potential raw material for the production of adiponitrile. Indeed, a great deal of work has been conducted in various laboratories in an effort to find a satisfactory route to adiponitrile employing acrylonitrile as the basic starting material.

One such route has involved the conversion of acrylonitrile to the 3-halo propionitrile derivative by the addition of hydrogen halide. Subsequently, this halopropionitrile is coupled through the use of certain coupling agents to form the product adiponitrile. Illustrative of the patents in this area are Belgian Pats. 746,415, 746,416; 758,- 035 and 746,417.

Other routes have involved the electrolytic conversion of acrylonitrile to adiponitrile or reductive coupling of acrylonitrile using various metal amalgams. The art is replete with patents concerning this process, an illustration being US. Pat. 3,462,478 as only one of a great many. In addition, reductive dimerizations of acrylonitrile in the presence of ruthenium type catalysts to produce adiponitrile have been proposed. In this regard, reference is made to Belgian Pat. 677,989 as one of a number of such references.

Still another method which has been considered is the direct dimerization of acrylonitrile to the linear 1,4-dicyano derivative or mixtures containing this derivative. In this regard, US. Pat. 3,538,141 provides a good analysis of the prior art in this area and presents a catalytic method for carrying out the linear dimerization.

For various reasons, the methods previously advanced for the conversion of acrylonitrile to adiponitrile have not been entirely satisfactory. Among the disadvantages of such prior procedures are high energy requirements, the use of expensive reagents or catalysts, low reaction rates or selectivities and the like.

As is known in the art, the dimerization of acrylonitrile will proceed at a rapid rate under convenient conditions but with the formation of the branched dimer, 2-methylene glutaronitrile, as the predominant product.

It has now been found that this Z-methylene glutaronitrile can readily be converted to the desired linear 1,4- dicyanobutenes. The predominant dicyanobutene produced is a mixture of a cis and trans 1,4-dicyano-l-butene, although cis and trans 1,4-dicyano-2-butene are also produced.

According to one embodiment of the invention a 1,4- dicyano butene is prepared by subjecting 1,2,4-tricyanobutane to dehydroeyanation conditions.

According to another embodiment of the invention Z-methylene glutaronitrile is subjected to an isomerization reaction and 1,4-dicyanobutenes are recovered.

Thus in the first embodiment for the overall process Z-methylene glutaronitrile is subjected to the addition thereto of hydrogen cyanide followed by the dehydrocyanation of the resulting product. Thus, in a first step, hydrogen cyanide is added to Z-methylene glutaronitrile to produce 1,2,4-tricyanobutane. In a second step, the 1,2, 4-trieyanobutane is subjected to a dehydrocyanation reaction whereby the resulting product contains the desired mixture of 1,4-dicyanobutenes formed by removal of the cyanide group from the 2 carbon atom. Both process steps are preferably carried out in the liquid phase using basic catalysts, though vapor phase techniques are also applicable.

For this embodiment of the process, the overall sequence of reactions, beginning with acrylonitrile, can thus be written as follows:

2CHa==CH-CEN NECECH;CHz-CEN The 1,4-dicyano-1-butene product shown in reaction c is a cis and trans mixture and represents the main product. Cis and trans 1,4-dicyano-2-butene are also formed. For convenience, this process carried out in accordance with the foregoing sequence will hereinafter be referred-to as the two-step process, the first step being reaction b of the above sequence (referred to for convenience as addition) and the second step being reaction c of the above sequence (referred to for convenience as pyrolysis and/or as dehydrocyanation).

In this two-step process, it has been found that most advantageous conditions in terms of yield and efliciency for the hydrogen cyanide addition involve use of liquid phase reaction techniques, with the reaction being conducted at temperatures from about 0 C. to about 300 C. in the presence of a basic catalyst. Although those conditions are preferred, other conditions can be used, including conditions analogous to those described in US. Pat. No. 2,434,606 for the addition of hydrogen cyanide to acrylonitrile. Additionally, it should be noted that the overall feasibility of this addition is described in French Pat. No. 1,411,003, while the preparation of 1,2,4-tricyanobutane is described in a still earlier reference, Chem. Abstracts, vol. 45, 9464g.

The dehydrocyanation reaction (c above) can be conducted over a broad range of conditions, illustratively at temperatures from about 100 C. to about 1000" C. in either vapor or liquid phase, with liquid phase reactions being preferred. Advantageously this dehydrocyanation, or pyrolysis, is conducted in the presence of a basic catalyst. Yet another feature of this invention, however, involves the conduct of this dehydrocyanation or pyrolysis under conditions giving extremely high selectivity to the 1,4-dicyanobutenes and to by-product Z-methylene glutaronitrile which is readily recycled to the hydrogen cyanide addition step (reaction b above). These optimum conditions involve the maintenance of low concentrations, not in excess of 40 mole percent, of the 1,4-dicyanobutenes plus Z-methylene glutaronitrile relative to 1,2,44ricyanobutane throughout the dehydrocyanation.

In another embodiment of this invention, referred to hereinafter as the one-step process, Z-methylene g'lutaronitrile isdirectly converted to the 1,4-dicyanobutenes by reaction, in accordance with the following chemical equation, in the presence of a basic catalyst and hydrogen cyanide or a hydrogen cyanide precursor capable of providing hydrogen cyanide under reaction conditions. This one-step process, though most advantageously carried out in the liquid phase, can also be conducted by employment of vapor phase procedures.

110 N N EN- CHaCHz-C EN As before, though the product is shown as being a 1,4- dicyano-l-butene (a cis and trans mixture), cis and trans 1,4-dicyano-2-butene are also formed. Although at first glance the chemical equation (often hereinafter referred to for convenience as isomerization) given for the onestep process is suggestive of a concurrent carrying-out of reactions b and c" of the two-step process in situ, it has not been established that this in fact occurs and the same or different reaction mechanisms may be involved. Accordingly, no representations are herein made as to whether the reaction mechanisms of the one-step process are the same as or different from those of the two-step process and no conclusion of similarity or dissimilarity should be drawn.

In carrying out the processes, acrylonitrile can be dimerized in accordance with known techniques to produce a mixture of linear and branched dimers. The linear dimers (i.e., the 1,4-dicyanobutenes) which are directly produced can conveniently be used in the preparation of adiponitrile, and such materials can if desired be directly separated from the dimerization efiluent for direct hydrogenation to adiponitrile. Suitable reaction conditions for employment in acrylonitrile dimerization include those illustrated in, for example, either French Pat. No. 1,385,- 883 or in US. Pat. No. 3,225,083. Illustratively, catalysts such as the tertiary phosphines can conveniently be employed, and the reaction is desirably carried out in the liquid phase. Generally, however, any of the known dimerization procedures can be employed.

2-methylene glutaronitrile is then converted into a mixture of the linear isomers (i.e., the 1,4-dicyanobutenes) by either the two-step or the one-step process.

Dealing first with the two-step process: Hydrogen cyanide is reacted with the Z-methylene glutaronitrile to form 1,2,4-tricyanobutane, preferably with a high degree of selectivity. Conditions suitably employed in this addition reaction include those closely analogous to the one set forth in US. Pat. No. 2,434,606, which describes the addition of hydrogen cyanide to acrylonitrile. Generally speaking, liquid or vapor phase procedures can be employed, with liquid phase techniques being preferred. Quite mild temperatures, illustratively ranging from about 0 C. to about 300 C., can be employed, although temperatures outside this range are also readily operative. It

is distinctly advantageous to carry out this reaction in the presence of basic catalysts.

Best results, however, for the conduct of the addition reaction are obtained when the reaction is carried out at temperatures broadly ranging from 0 C. to 300 0., preferably ranging from 40 C. to 150 C. and most advantageously from about 50 C. to about 125 C. As indicated, the process is most advantageously carried out in the liquid phase; accordingly, pressure sufficient to, or slightly above that necessary to maintain a liquid reaction phase can be employed. Illustrative pressures can thus range from about 0.03 to about 1000 atmospheres, with higher or lower pressures also being suitable.

Also as indicated, best results are obtained by use of a basic catalyst. The amount of such catalyst employed, however, can vary broadly, with quantities varying from 0.0001 to 10.0% by weight, based on the total charge, being employable. More desirably, catalyst concentrations from about 0.001 to about 5.0 wt. percent, based on total charge, can be employed while, preferably, from about 0.002 to 3.0 wt. percent of catalyst are used. As indicated, both soluble and insoluble basic catalyst forms are employable. Soluble catalysts are dissolved in the reaction mixture, most advantageously in the above-indicated amounts, while insoluble catalysts are dispersed in finely divided form in the reaction mixture while the reaction mixture is subjected to vigorous agitation in order to promote intimate contacting. Alternatively, of course, the basic catalyst substances can be deposited upon solid particulate supports, with the reagents being intimately contacted with the supported catalyst forms.

Alhough the addition reaction involves the reaction of 1 mole of hydrogen cyanide with 1 mole of 2-methylene glutaronitrile, the relative amounts of Z-methylene glutaronitrile and hydrogen cyanide charged to the reaction can vary widely. Generally, ratios ranging from about 1 mole of Z-methylene glutaronitrile per 100 moles of hydrogen cyanide to 100 moles of Z-methylene glutaronitrile per mole of hydrogen cyanide are employable. Preferably, the reagents are charged in a mole ratio of hydrogen cyanide to Z-methylene glutaronitrile of from about 0.9:1 to about 5:1 and more preferably from about 1:1 to 2:1.

It is most advantageous to operate with an excess of hydrogen cyanide over that stoichiometrically required in order to maximize conversion of 2-methylene glutaronitrile and to thereby minimize the amount of unreacted 2-methylene glutaronitrile to be recycled. Of course, any unreacted hyrogen cyanide can convenientlybe stripped from the eflluent mixture for recycle and re-use in the process.

In carrying out the addition reaction, both batch and continuous procedures can be employed, although, considering the modern trend to high-output chemical plants, continuous procedures are preferred. These can involve the use of a single reactor or a number of reactors in series or in parallel.

The addition reaction can be conducted in the presence of or in the absence of solvents, though the use of solvents is normally desirable. When used, solvents can range from about 5 to about 99% (by weight) of the reaction mixture, although it is generally preferred, where the solvent is neither a reactant nor a product, that the solvent be employed in amounts from about 20% to about (weight basis) of the total charge to the reaction. Concentrations of Z-methylene glutaronitrile of from about 3 wt. percent to about 60 wt. percent of the charge to the addition reaction are preferred, although 2-methylene glutaronitrile concentrations as low as 1 wt. percent or even lower can be employed, albeit with somewhat less advantageous results.

The second reaction of the two-step process results in dehydrocyanation of the 1,2,4-tricyanobutane by subjection of the 1,2,4-tricyanobutane to a pyrolysis-type reaction, thereby splitting out hydrogen cyanide. This reaction, too, can be carried out in the vapor or liquid phase.

Generally speaking, the pyrolysis is carried out at temperatures in the range of about 100 C. to about -1000 0., although this temperature can be varied as well. More desirably, the pyrolysis is carried out in the liquid phase at temperatures from about 100 C. and 700 C., more advantageously at temperatures between about 200 C. and about 500 C. and preferably at temperatures between about 220" C. and about 350 C.

Most advantageously, abasic catalyst is employed in the dehydrocyanation. In vapor phase operation, the basic catalyst is preferably supported on a solid substrate such as coke, charcoal, alumina, silica-alumina, the aluminosilicates, silica gel or the like. In liquid phase reaction, the catalyst is most advantageously dissolved or suspend ed in the reaction mixture, and thus no support is required.

When using catalysts, as is preferred, the amounts employed can vary broadly. Generally, amounts sufiicient to provide 0.01 to 1000 millimoles of catalyst per liter of reaction solution, desirably 0.05 to 500 millimoles of catalyst per liter of reaction solution and preferably 0.1 to 400 millimoles of catalyst per liter of reaction solution are used.

Here, too, solvents can be employed in essentially the same amounts as are indicated above in connection with the addition step.

The pyrolyzate, i.e., the reaction mixture obtained from the pyrolysis or dehydrocyanation reaction, is processed by conventional means such as, for'example, distillation to recover product 1,4-dicyanobutenes. Cis and trans 1,4dicyano-l-butenes are the major components of the products obtained, although cis and trans 1,4-dicyano- 2-butene are also present. All of these materials are, of course, adiponitrile precursors. Any splitting-out of the cyano group on the l-carbon of the charge material .(1, 2,4-tricyano-butane) results in the production of 2-methylene glutaronitrile which obviously can conveniently be recycled to the addition step.

It is advantageous to .conduct the dehydrocyanation in a manner such that the hydrogen cyanide is removed from the reaction mixture as it is formed.

Obviously, itis desired to conduct the .1,2,4-tricyanobutane dehydrocyanation in such a manner as to achieve the highest selectivity to the desired 1,4 -dicyanobutenes and to 2-methylene glutaronitrile which can be recycled without significant yield loss. Therefore, in accordance with another embodiment of this invention, ithas been found that significantly improved dehydrocyanation selectivity is achieved by maintenance of low product con centrations during the pyrolysis. In this embodiment,.not more than 40 mole percent of 1,4-dicyanobutene plus 2'- methylene glutaronitrile are present .relativeto l,2,4-tri cyanobutane throughout the dehydrocyanation."Conduct of the pyrolysis in this fashion tends to minimize the extent to which other reactions occurrin during dehydro cyanation, and which give rise to the formation of 'un desirable by-products, take place. Even more'advantageous in terms of selectivity is maintenance of the con* centration in the dehydrocyanation reaction of 1,4;dicyanobutene plus 2-methylene glutaronitrile "relativeto 1,2,4-tricyanobutane at a level preferably not more'than 20 mole percent and most advantageously at a level-not more than mole percent throughout'thedehydrocyanation. Accordingly, throughout the dehydrocyanation, best results are obtained when the concentration' of 1,4'-dicyanobutenes plus Z-methylene glutaronitrile is maintained at not more than 4 moles per 10 moles of unreacted 1,2,4-tricyanobutane in the reaction mixture, preferably not more than 2 moles and most advantageously not-more than 1 mole per 10 moles of unreacted l, 2',4-tr icy'ano'- butane. L I 1 It has been found that'by carrying out the dehydrocyanation reaction while maintaining-but a minimum con-' centration of these dehydrocyanation products (i'.e'., the 1,4-dicyanobutenes and Z-methylen'e glutaronitrile) in the liquid reaction mixture the very highest selectivities to theseproducts are achieved. As a practical matter, the dehydrocyanation is carried out while maintaining the specified low product concentrations in any one of several ways. In a continuous reaction system the dehydrocyanation is advantageously carried out under conditions such that product 1,4-dicyanobutenes and 2-methylene glutaronitrile are immediately vaporized and removed from the reaction zone together with the hydrogen cyanide. One preferred method is to carry out the dehyrocyanation using a boiling reaction mixture and taking some of the tricyanobutane together with the dehydrocyanation products overhead. By appropriate temperature and pressure adjustment and return of boil-up tricyanobutane, the desired low concentrations of 1,4-dicyanobutenes and 2- methylene glutaronitrile are readily achieved. Thus, to facilitate concentration control, it is generally desirable to conduct the pyrolysis at pressures between about 0.01 atm. abs. and about 100 atm. abs. when conducting the pyrolysis at the normally desired and preferred temperatures. Greater pressures can, of course, be used, especially at higher pyrolysis temperatures. An alternative procedure in a continuous system is to provide a relatively higher boiling solvent, said solvent having a boiling point close to and preferably somewhat higher than the highest boiling l,4dicyanobutene isomer and boiling out this solvent and the dehydrocyanation products during the reaction. When such relatively higher boiling solvents are employed, the solvent can comprise from about 5% by weight to about 95% by weight of the liquid phase reaction mixture, desirably from about 10% by weight to about 90% by weight of the liquid phase reaction mixture and preferably from about 20% by weight to about by weight of the liquid phase reaction mixture.

In a batch system, the concentrations of the products can be controlled at a level below the above-specified maxima without removing dicyano products by controlling the dehydrocyanation conversion to an appropriately low level in each of the batch reactions, i.e., to a conversion of 28.6% or less, although higher conversions can be achieved with appropriate product removal during the reaction.

-By far the preferred procedure is a continuous system, with the 1,4-dicyanobutenes and 2-mcthylene glutaronitrile being constantly boiled out of the reaction mixture together with solvent or with some tricyanobutane and, of course, the hydrogen cyanide which is also a product of the dehydrocyanation. It is especially advantageous in such systems to provide a fractional distllation zone in direct association with the dehydrocyanation reactor so that the-vapors from the dehydrocyanation reaction mixture pass directly to the fractionation column whereby the desired products are separated as distillate from solvent or' tricyanobutane, the latter being returned to the dehydrocyanation zone.

It hasbeen found'that by maintaining low concentrations of ;the 2-methylene glutaronitrile and 1,4-dicyanobutenes in the dehydrocyanation reaction mixture, substantial yield improvements are achieved. For example, dehydrocyanation selectivities either to the desired 1,4- linear dicyano products and to the recyclable 2-methylene glutaronitrile of the order of -100% can be achieved. .By way of contrast, where significantly higher concentrations of these products are maintained in the reaction mixture,'lower selectivities are obtained.

The one-step process, involving the isomerization reaction hereinabove set forth, is most advantageously carried out inthe liquid phase although, here also, vapor phase procedures can be employed. The isomerization can be conducted'over a broad temperature range, temperatitres from about C. to about 700 C. being applicable, with temperatures between about 100 C. and about 400 C. being preferred and temperatures between about C. and about 350 C. having been found most'advantageous. As the 'isomerization can be carried out in the liquid phase, pressures sufiicient to, or slightly above that necessary to maintain a liquid reaction phase can be employed. Illustrative pressures can thus range from about 0.01 to 1000 atmospheres, with higher or lower pressures also being suitable.

Important considerations in the practice of the isomerization reaction include provision both of a basic catalyst and hydrogen cyanide or a hydrogen cyanide precursor capable of providing hydrogen cyanide at the conditions of the isomerization reaction.

The catalyst employed can be soluble or insoluble in the isomerization reaction system. Insoluble catalysts can be suspended in the reaction system in finely dispersed form or they may be supported on suitable carriers of the type indicated above (coke, charcoal, alumina, silicaalumina, alumino-silicates, silica gel, etc.). Generally, the amount of catalyst employed is sufiicient to provide from about 0.01 to about 1000 millimoles of catalyst per liter of reaction solution, although amounts outside this range can also be employed. Preferably, the amount of catalysts employed is suificient to provide from about 0.05 to about 500 millimoles of catalyst per liter of reaction solution.

As indicated above, the isomerization reaction requires the presence of hydrogen cyanide or a hydrogen cyanide precursor within the reaction system during the isomerization. A hydrogen cyanide precursor is a material capable of providing hydrogen cyanide under the conditions of the reaction. By far the preferred precursor is 1,2,4-tricyanobutane since this material is clearly eflicacious and may well be an intermediate in the isomerization reaction, though this has not been established. Other precursors can also be employed in addition to or in lieu of hydrogen cyanide itself or the preferred 1,2,4-tricyanobutane hydrogen cyanide precursor including, for example, such materials as succinonitrile, acidified cyanide salts, tertiary phosphine-HON addition compounds and tertiary amine-HCN addition compounds. Obviously, mixtures of precursors or of hydrogen cyanide and precursors can be used. It should also be noted that, because of equilibrium reactions typified by:

2 methylene glutaronitrile+HCNS1,2,4-tricyanobutane the form of the precursor in the reaction mass may differ from the added form. The amount of hydrogen cyanide or precursor can vary widely in the practice of this embodiment of the invention. Where hydrogen cyanide itself is the predominant cyanide species present in the reaction mass, it can be present in amounts ranging from about 0.01 to about 5.0 moles per mole of Z-methylene glutaronitrile in the reaction zone. Where a precursor such as 1,2,4-tricyanobutane predominates, it can comprise from about 0.1 to about 99.9% by weight of the reaction mixture.

It has hereinabove been indicated that basic catalysts are preferably employed in the addition reaction, in the pyrolysis reaction, and in the isomerization reaction, and the amounts of such catalysts suitably employed have hereinabove been indicated. Exemplary of such basic catalysts are compounds having as the cation moiety an alkali metal; an alkaline earth metal; a metal from Groups II-B, III-B, IV-B, V-B, VI-B, VII-B and VIII of the Periodic Table; a metal of the lanthanide series; indium;

thallium; lead as well as ammonium or phosphonium cations. These cations can be associated with a wide variety of anions including cyanide, cyanate, acetate, propionate, butyrate, octoate, benzoate, salicylate, acetylacetonate as well as other anions derived from relatively weak acids. Phenolates, alkoxides, carbonates, sulfonates, amides, phosphates, polyphosphates, oxides, hydroxides and the like also are readily employable. Additional catalytic substances having basic characteristics which are active as catalysts in the various steps of this invention include heterocyclic amines (e.g., pyrrole and pyridine among others) as well as aryl, alkyl and cycloalkyl amines; phosphines; arsines and stibines and additionally, of course, quaternary ammonium and phosphonium hydroxides. Basic ion exchange resins are also suitable.

It should be noted that during the reactions occurring in this invention, in either the one-step or two-step processes, the catalyst may itself undergo chemical change. It is, for example, believed, though not confirmed, that catalysts which are supplied to the reaction systems in the form of compounds having anions other than cyanide are converted at least in part to the corresponding cyanides. Obviously, therefore, the anion moiety of the catalytic substance is not of particular criticality though it has been noted that anions of strong acids (such as nitrate, sulfate and the halides) tend to slow the reaction rates somewhat. It is also obvious that organo-metallic substances such as, for example, cyclopentadienyl-sodium and butyl-lithium also represent active catalytic species since it is known that compounds of these types can react with hydrogen cyanide and are thereby readily converted to the corresponding metal cyanides. Furthermore, it should be noted that quaternary ammonium and phosphonium compounds may well be generated by an in situ process of quaternarization during the reaction when heterocyclic amines, tertiary amines or tertiary phosphines are charged as catalysts to the systems employed. Compounds believed to undergo such typical quaternarization reactions include trioctyl amine, triphenyl phosphine, tributyl phosphine, tricyclohexyl phosphine and l,4-diazabicyclo(2,2,2)octane.

Typical catalysts are: Cs hydroxide, K cyanide, Na cyanide, Li oxide, Li amide, Li hydroxide, Ca carbonate, Sr hydroxide, Na methoxide, Ba oxide, Zr oxide, Mn hydroxide, Ni cyanide, Zn oxide, Cd cyanide, Tl hydroxide, Pb acetate, Benzyltrimethyl ammonium hydroxide, Ce hydroxide, Er acetate, K Fe(CN) and LiTl tartrate, Li acetate, Li butyrate, Li stearate, Li carbonate, Li benzoate, Li cyanide, Li acetylsalicylate, Li thiocyanate, Mg oxide, Mg cyanide, Ca cyanide, Ca hydroxide, Sr benzoate, Sr cyanide, Ba naphthenate, Ca naphthenate, Ce acetate and Er formate and Li isobutyrate.

Preferred catalysts are phosphines and amines and compounds of the following cations: K, Na, Li, Mg, Ca, Sr, Ba, Cd, Tl, Pb, Mn and a rare earth metal as well as, particularly for the addition reaction, the metals of Group VIII of the Periodic Table, especially Ni and Co.

Particularly preferred catalysts are tertiary phosphines and tertiary amines and compounds of the following cations: K, Na, Li, Ca, Sr, Ba and a rare earth metal, as

well as, particularly for the addition reaction, cations of v Group VIII of the Periodic Table, especially Ni and Co.

The most preferred catalysts for addition, pyrolysis and isomerization are the alkali and alkaline earth metals and especially Li compounds (hydroxide, oxide, cyanide, carbonate, etc.) as well as the aliphatic and cycloaliphatic tertiary phosphines, heterocyclic amines and .aliphatic tertiary amines. Preferred phosphine and amine catalysts are: triphenylphosphine; tributylphosphine; trioctylphosphine; tri-isopropylphosphine; tri-cyclohexylphosphine; trimethylamine; tributylamine; tricyclohexylamine; 1,4-diazabicyclo(2,2,2)octane and benzyltrimethyl ammonium hydroxide.

The tri-alkyl and cycloalkyl phosphines surprisingly are much more effective catalysts than the corresponding amines. This would not be expected since the phosphines are much weaker bases than the amines and thus would be anticipated to be less active. The phosphines are as active as the strong base LiOH on a molar basis and are unique since their activity is not wholly due to their strength as bases. The tricycloal-kyl phosphines such as tricyclohexyl phosphine, tricyclooctyl phosphine and tricyclopentyl phosphine together with K, Na, Li, Sr, Ba and the lanthanide salts are especially outstanding catalysts for isomerization and are also entirely suitable for use in the addition and pyrolysis reactions. The alkali and alkaline earth metals as well as the tertiary alkyl and cycloalkyl phosphines are especially outstanding catalysts in pyrolysis as well.

Also as indicated above, solvents can be employed in each of the two reactions of the two-step process and can also be employed in conduct of the isomerization re-. action of the one-step process. Suitable solvents include hydrocarbons (paraflins, cycloparaflins and aromatics), ethers, alcohols, esters, dialkyl sulfoxides, dialkyl amides and nitriles. It is generally preferred, however, to employ polar solvents rather than non-polar ones since it has been observed that the presence of polar solvents tends to give increased reaction rates as compared with systems using nonpolar solvents. Preferred solvents for the addition and isomerization reactions thus include generally any polar material which does not react with methylene glutaronitrile, hydrogen cyanide or dicyanobutenes under reaction conditions. Exemplary of such preferred solvents for the addition reaction are the nitriles including propionitrile; acetonitrile; adiponitrile; 2-methylene glutaronitrile itself and most preferably 1,2,4-tricyanobutane. For the isomerization reaction, the same solvents are preferred. Boiling point characteristics result in a slightly different class of particularly preferred solvents for the pyrolysis reaction of the two-step process, exemplary of which are adiponitrile, stearonitrile, synthetic baybcrry wax (chiefly palmitin), polyglycol 600 and polyglycol 600 distearate.

Small amounts of conventional polymerization-inhibitors (e.g., t-butylcatechol, sulfur, hydroquinone, and the like) can often be employed with advantage in each of the reactions of both the one and two step processes to minimize the extent of possible polymerization that might sometimes otherwise occur.

Through the procedures described above it can be seen that acrylonitrile is elfectively converted to a linear 1,4- dicyanobutene precursor of both adiponitrile and hexamethylene diamine by eflicient, effective, straightforward means. Use of expensive reagents and energy requirements of the prior art are substantially avoided. The process is simple and very highly effective and eflicient.

In order to more clearly illustrate the invention, the following examples illustrate various embodiments thereof:

EXAMPLE '1 Dehydrocyanation of 1,2,4-tricyanobutane A vertical, A inch stainless steel tube (20 inches long) provided with an inlet at the top and an outlet at the bottom was heated in an electric furnace. A layer of stainless steel wool was placed in the bottom of the tube upon which was placed the dehydrocyanating catalyst; 5 ml. of active carbon containing 15% by weight of potassium cyanide on the surface. On the top of the catalyst was placed a six inch layer of small glass beads. A thermocouple was used to measure the temperature in the reaction zone. A slow stream of molten 1,2,4-tricyanobutane was introduced in the top of the tube and diluted with nitrogen which was used as carrier gas. The 1,2,4- tricyanobutane was vaporized on contact with the hot glass beads, and the vapors were immediately subjected to the reaction temperature. The reaction products were condensed in a glass condenser after passing the outlet of the tube and collected in acetone/Dry Ice cooled receivers.

In operation, under the following conditions: temperature=350 C., feed rate=0.25 mole 1,2,4-tricyanobutane per hour and 0.75 mol nitrogen per hour, about 25% of the tricyanobutane reacted and a reaction product composed of 1,4-dicyano-1-butene (trans/cis), 5% 1,4- dicyano-Z-butene (trans/cis) and 40% Z-methylene glutaronitrile based on gas-liquid chromatographic analysis was recovered.

10 EXAMPLE 2 Dehydrocyanation of 1,2,4-tricyanobutane The experiment described in Example 1 was repeated at a temperature of 450 C. with the difference that no dehydrocyanating catalyst was used. The space between the glass beads and the stainless steel wool was filled with silicon carbide (Carborundum). In this experiment a reaction product having the following composition was recovered: 25% 1,4-dicyano-1-butene (trans/cis), 2% 1,4- dicyano-Z-butene (trans/cis) and 73% Z-methylene glutaronitrile.

EXAMPLE 3 (a) Dimerization of acrylonitrile A mixture of 160 grams of acrylonitrile, 10 grams hydroquinone, and 600 ml. dioxane were heated to reflux at one atmosphere pressure under an atmosphere of prepurified argon. A solution containing 6 grams tricyclohexyl phosphine in 200 ml. dioxane was added gradually over a period of 20 minutes. The mixture was heated to reflux for an additional 20 minutes, then fractionated through a 20 plate one-inch Oldershaw column. grams of Z-methylene glutaronitrile of purity was recovered as the cut distilling between 138 C. and 142 C. ata pressure of 16 mm. Hg.

(b) Preparation of 1,2,4-tricyanobutane 64 grams Z-methylene glutaronitrile (from Example 3a), 60 ml. propionitrile and 1 gram triethylamine were charged to a 200 ml. glass reaction flask provided with magnetic stirring, reflux condenser and gas inlet. This mixture was cooled to 80 C. and 16.2 grams hydrogen cyanide gas were condensed into the cooled mixture. The resulting mixture was then allowed to warm up to room temperature and was stirred at 25 C. for 48 hours. Gas liquid chromatography analysis of the reaction mixture indicated that the hydrocyanation of the 2-methylene glutaronitrile was near completion. Solvent (propionitrile) catalyst (triethylamine) and unconverted 2-methylene glutaronitrile were removed from the reaction product by flash distillation under reduced pressure. As reaction product was obtained 69 grams'of 1,2,4-tricyanobutane. This raw product was further purified by treatment with active carbon and crystallization from absolute ethanol. 60 grams of pure white crystalline material with a melting point of 53-54 C. were recovered. This reaction product was by means of infra red spectroscopic analysis shown to be identical with 1,2,4-tricyanobutane made by known literature procedure.

(0) Dehydrocyanation of 1,2,4-tricyanobutane in the liquid phase grams of a 50:50 mixture by weight of 1,2,4- tricyanobutane (from Example 3b) and propionitrile was slowly (approximately 1 gram/min.) added to a well'agi tated reaction flaskcontaining a suspension of 20 grams sodium cyanide in 50 ml. eicosane at a temperature of 300:10 C. The reaction flask was provided with a small Vigreux column which was connected'to a water cooled 1 1 tionated through a 20 plate Oldershaw column and the following four cuts were collected:

(1) cut 25-35 C./1 atmosphere (HCN) (2) cut 35100 C./ 1 atmosphere (propionitrile, sol- Runs made in 'a manner similar to the above with sodium hydroxide as catalyst did not result in HCN or methylene glutaronitrile conversion due, it is believed, to insolubility of catalyst and lack of agitation during the run and as regards magnesium hydroxide to low catavent) (3) cut 138 1 (V16 mm Hg (zqnethylene glutaro lyst actlvlty at the reactlon conditions. The 1,2,4-tr1cyanonitrne) butane was converted to 1,4-d1cyanobutene by dehydro- (4) cut 142170 C./16 mm. Hg (1,4-dicyanobutenes) cyanatlon The hydrogen cyanide (recovered as cut 1) and the EXAMPLE 6 Z-methylene glutaronitrile (recovered as cut 4) were converted into l,2,4tricyanobutane using triethylamine as 0116 llter autoclave 18 charged Wlth 500 cc. of catalyst in accordance with the procedure described in q y blanketed 2 heated t0 Example 3b. The tricyanobutane so obtained was found Llquld z-methylene glutafonltrlle 1 fed t0 the I to be physically as well as chemically identical with 1,2,4- 15 actor at fate 103 grams/ 1101111 y p P tricyanobutane made from Z-methylene glutaronitrile obcatalyst 15 contamed the PY glutaromtl'lle tamed by dimerization f acrylonitrile. stream at a concentration of 0.33 weight percent. Hydrogen cyanide gas is bubbled into the autoclave at a rate EXAMPLE 4 of 28.9 grams/hour. Constant liquid level is maintained Preparation of 1,2,4-tricyanobutane 2 by withdrawing liquid from the reactor at a rate of about 0 150 cc./hour. The autoclave is allowed to operate for charge conslstlng 0f g m Y F f" four hours, at which time a steady state is achieved as mm grams of a 5 of HCN 111 P P Q indicated by the constancy of the efiluent analyses. mmle, 6J5 glams ploplomtrllP and 0-025 grams of An efiluent sample is accumulated for one hour. The y p p was Placed m a 30 heavy wallefl composition of the sample is 92.1 weight percent tricyanoglass ampoule and sealed under an argon atmosphere- Thls butane, 3.9 weight percent 2-methylene gl-utaronitrile. This P to a 1/1 IIIOlaI' HCN t0 methylene glutafo corresponds to a 95% conversion of fed Z-methylene mtrile ratio and 0.25 wt. percent catalyst. The tube was glutaronitrile and is selectivity of 98% to 1,2,4-tricyano- Placed m a 50 water bath for f the tube butane based on consumed 2-methy1ene glutaronitrile. The coolefl and opened and acetlc acld added to 1,2,4-tricyanobutane was converted to 1,4-dicyanobutene deactivate the catalyst. The reaction eflluent was then by dehydrocyanation' analyzed by titer and by gas liquid chromatography. The HCN conversion was 93.3% while that for methylene EXAMPLE 7 glutaronitrile was 99.6%, substantially all of the HCN reacted was converted to 1,2,4tricyanobutane. The 1,2,4- Batch type dehydrocyanation of 1,2,4-tricyanobutane tricyanobutane was converted to 1,4-dicyanobutene by dehydrocyanation. Forty grams 1,2,4-tr1cyanobutane (TCB) are charged EXAMPLE 5 to a 100 ml. stirred glass reactor and heated to 240 C. The reaction is then started by the addition of 0.013 A series of runs were made using various catalysts and grams lithium acetate catalyst and 100 mL/min. argon using propionitrile solvent in a manner similar to that gas is passed through the reaction liquid and into a 250 given for Example 4. In each case the designated mate ml. stirred flask containing 125 ml. 0.2 molar ammonia rials were charged to heavy walled glass reactors, sealed wherein the hydrogen cyanide reaction product is absorbed under argon and heated at the designated temperature for and titrated with 1 N silver nitrate. During the reaction the designated time. The reactions were thencooled and four 2 ml. samples of reaction mixture were withdrawn the contents analyzed by titration and gas chromatography and analyzed for content of 1,4-dicyanobutenes (1,4 DCB) for HCN and 2-methylene glutaronitrile conversion. The and Z-methylene glutaronitrile (2 MGN). The converclose agreement in these conversion figures indicated in sion was calculated based on the amount of hydrogen each case a selectivity to l,2,4-tricyanobutane of about cyanide determined. The results so obtained are given in 95 or better. the following table and clearly demonstrate the relation- TABLE 1 Feed Conditions Conversion, Mol ratio Wt. percent Wt. percent HCN] percent Temp., Time, MGN GN Catalyst catalyst 0. hrs. HCN MGN 1/1 TEA 1.0 2 49 .2 51.0 2/1 TEA 1.0 50 2 36.7 70.5 1/1 TEA 1.0 50 2 85.0 30.0 1/1 TBP 1.0 50 2 96.0 94.5 1/1 TB}? 0.1 50 2 93.2 96.0 1/1 TBP 0.1 50 2 59.0 62.0 1 1 TBP 0.01 50 2 10.2 8.8 1/1 TBP 1.0 30 2 88.0 98.8 1.03/1 TBP 0.25 50 2 90.2 99.6 1.03/1 TBP 0.25 50 1 85.6 94.3 1/1 MOE 1.0 50 2 99.5 95.0 1/1 MOE 0.1 50 2 97.0 95.2 1.03/1 LiOH 0.05 50 2 93.0 94.5 1.03/1 LiOH 0.01 50 2 32.8 28.2 2/1 Dowex-3 3.0 50 2 13.8 31.6

=2-methylene glutaronitrile; 'ICB=1,2,4-trieyanobutane; TEA=trlethyl- 1 3 ship between the concentration of 1,4-dicyanobutenes+2- methylene glutaronitrile and the selectivity of reaction:

1 See the following:

Mols 1,4 DOB 2 MGN X100 Mols TCB 1 See the following:

Mols 1,4 DCB 2 MGN formed X100 Mols TCB reacted EXAMPLE 8 Concentration Conversion 1.4 DOB 2- Overall Reaction time, MGN, mol selectivity, hr. 1, percent II, percent percent 1 percent 2 1 See the following:

Mols 1,4 DOB 2 MGN Mols TCB 2 See the following:

Mols 1,4 DOB 2 MGN formed x Mols TCB reacted EXAMPLE 9 Continuous dehydrocyanation of 1,2,4-tricyanobutane A continuous dehydrocyanation of 1,2,4tricyanobutane was carried out using a jacketed glass rota-film molecular still, model 50-2, which was fabricated by Arthur F. Smith, Inc. The inside condenser was cooled with circulating water at 25 C. and the outside jacketwas heated by dimethylphthalate vapor at 284 C. The film reactor was evacuated to 45:5 mm. Hgand 300 mL/min. preheated argon was passed through the reactor from the bottom. Overhead reaction products were trapped out at Dry Ice/acetone temperature (-80 C.) 300 grs. of 1,2,4- tricyanobutane mixed with 3 grs. lithium stearate preheated to 150 C. were fed to the reactor per hour. During the reaction condensed products were collected on the inside condenser as well as in the Dry Ice/ acetone cooled trap. Unconverted 1,2,4-tricyanobutane which did not vaporize during the reaction was collected as residue together with some byproducts and the catalyst. The following results were obtained for one hour reaction time: combined content of trap and overhead collected products were analyzed and found to be composed of 7.3 grams hydrogen cyanide, 9.4 grams. of Z-methylene glutaronitrile, 9.1 grams 1,4-dicyanobutene-1 (trans), 9.1 grams 1,4-dicyarro-butene-1 (cis) and 235 grams of 1,2,4- tricyanobutane. The residue was analyzed and found to have the following composition: 1.1 grams byproducts, 3 grams catalyst, 28.8 grams 1,2,4-tricyanobutane and less than 1 mol percent 2-methylene glutaronitrileand l.4-dicyano butenes.

Based on the obtained data the conversion of 1,2,4- tricyanobutane was calculated to 12% and the selectivity of the dehydrocyanation was computed to be 96%.

EXAMPLE 10 The procedure described in Example 9- was repeated at 740 mm. Hg pressure. At this pressure a decreased amount of boil-up was obtained compared with Example 9. The relative concentration of Z-methylene glutaronitrile and 1,4-dicyano butenes in the residue was analyzed to be 5 mol percent and the selectivity of reaction was calculated to be 50% at a 13% 1,2,4-tricyanobutane conversion.

EXAMPLE 11 Continuous dehydrocyanation of 1,2,4-tricyanobutane in a boiling reactor Seventy grams/hr. of 1,2,4-tricyano butane and 3 grams/hr. of lithium stearate was preheated to 150 C. and fed continuously to a 304 stainless steel falling film reactor (evaporator). The reactor had an I.D.=2 in. and an evaporative area of 50 sq. in. and was on the top directly connected to a one in. fractionation column with approximately 5 theoretical plates. The column was provided with a reflux splitter on the top which was connected to a vacuum system at 45 mm. Hg pressure. The reactor was heated with a salt bath and the temperature was controlled at 285 :3 C. 300 mL/min. (25 C.) preheated argon (285 C.) were fed through the reactor from the bottom in counterstream with the falling film of reaction mixtures. The evaporative areas was wiped with carbon wipers in order to improve the rate of evaporation. During the run, product was continuously collected overhead at a reflux ratio of 1 to 4 (back) and unconvereted 1,2,4-tricyanobutane together with the catalyst, heavies (byproduct) and some product withdrawn from the bottom of the reactor. The following results were obtained per hour reaction time: Overhead product: 28 grs. 2 methylene glutaronitrile and 1,4-dicyanobutenes, 3 grams 1,2,4-tricyanobutane and 7.9 grams of hydrogen cyanide. Product drained from' the bottom of the reactor: 30 grams 1,2,4-tricyanobutane, 3 grams lithium stearate, 2.5 grams byproducts (heavies) and 0.6 gram 2-methy1ene glutaronitrile and 1,4-dicyano butenes (corresponding to a relative concentration of 2.5 mol percent). The 1,2,4- tricyanobutane conversion was calculated to 55.7% and the selectivity of the reaction was determined to be 92%.

The overhead product was fractionated through a 40 plate Oldershaw column and 8 grams of practically pure Z-methylene glutaronitrile was collected as the cut boiling ctw enli f. an 3. C- tr flinmi. H P essure- The s-o-obtained Z-methylene glutaronitrile was converted back to 1,2,4-tricyanobutane in reaction with hydrogen cyanideat 50 C. using tributylphosphine as the catalyst. The so-made 1,2,4-tricyanobutane was found to be physically and chemically identical with 1,2,4 tricyanobutane made fronr commercial 2-methylene glutaronitrile and hydrogen cyanide under the same conditions.

EXAMPLE 12 Preparation of 1,4-dicyanobutenes Using thesame equipment as described in Example 1, a mixture containing 0.5 mol Z-methylene glutaronitrile and 0.25 'mol hydrogen cyanide was reacted by passing it through the reaction tube which contained 5 ml. of a catalyst composed of active carbon (support) and 10% cesium cyanide at a temperature of 255 C. At a feed rate of approximately 0.75 mol/hour a reaction productwas collected in the product receiver which was analyzed by gas-liquid chromatography and found to contain by weight'4% of 1,4-dicyano-l-butene (trans/cis), 0.1% 1, 4-dicyano-2-butene (trans/cis) in addition to 1,2,4'-tricyanobutane and unconverted Z-methylcne glutaronitrile.

15 EXAMPLE 13 A mixture composed of 4.5 millimols Z-methylene glutaronitrile, 37 millimols 1,2,4-tricyanobutane and 1 milligram LiOH in 40 m1. adiponitrile was heated in a closed system at 248 C. for 15 minutes under an argon atmosphere. The reaction mixture was then cooled to room temperature, extracted with 45 ml. water to remove the basic catalyst and analyzed by gas liquid chromatography. Analysis indicated the mixture contained 0.7 millimols 2-methylene glutaronitrile and 3.1 millimols 1,4-dicyanobutene (composed of approximately 95% of the 1,4-dicyano-l-butene trans and cis isomers.) The 1,2,4-tricyanobutane was analyzed to be unchanged in amount at 37 millimols.

I EXAMPLE 14 A mixture composed of 40 millimols 2-methylene glutaronitrile, 36 millimols hydrogen cyanide and 2 milligrams 'LiCN in 40 ml. adiponitrile was heated up to 253 C. in a closed system under an atmosphere of nitrogen and held at that temperature for 20 minutes. The reaction mixture was then cooled to room temperature and extracted with 40 ml. water. By gas liquid chromatographic analysis the mixture was found to contain 2.8 millimols 1,4-dicyano-1-butene (trans/cis) and 35 millimols 1,2,4-tricyanobutane based on gas liquid chromatographic analysis.

EXAMPLE 15 EXAMPLE 16 A mixture composed of 4.5 millimols 2-methylene glutaronitrile, 37 millimols 1,2,4-tricyanobutane, 20 ml. adiponitrile and 1 milligram NaCN was heated in'a closed system at 250 C. for 60 minutes under an argon atmosphere. During this time three 2 ml. samples were withdrawn from the reaction mixture, extracted with 2 ml. of water and analyzed by gas liquid chromatography. The following results illustrate the reaction time/conversion relationship of the system:

Product analysis,'mil1imols 2 MGN 1,4 D013 1 (trans/cis) Reaction time, min;

1 1,4-dieyano-l-butene.

EXAMPLE 17 Example 16 was repeated in the presence of 0.5 ml. Sulfolane-W (Shell Chemical Co.). The isomerization reaction was found to be complete after rninutesreaction time resulting in a reaction mixture containing 10 mol percent Z-methylene glutaronitrile and 90 mol percent 1,4-dicyanobutenes.

EXAMPLE 18 A mixture composed of 4.5 millimols 2 methylene glutaronitrile, 37 millimols 1,2,4-tricyano butane, 20 ml. adiponitrile and 10 milligrams 1,4-diazabicyclo-(2,2,2.) octane (triethylene diamine) was heated for 2 hours at 250 C. in a closed glass reactor under an argonatmosphere. The mixture was then cooled to room temperature,

' 16 extracted with 45 ml. water containing 0.1 gram acetic acid and analyzed by gas liquid chromatography. The yield of 1,4-dicyano-1-butene (trans/cis) was 14% and the conversion of 2-methylene glutaronitrile was determined to be 3 4%.

EXAMPLE 19 In continuous fashion Z-methylene glutaronitrile is isomerized to 1,4-dicyano butenes in a reactor equipped with agitating and heating means. To the reactor are fed 0.30 mol/hour 2-methylene glutaronitrile, 10 mols/hour 1,2,4-tricyanobutane and 0.0015 mol/hour LiCN catalyst. The reaction mixture is maintained at 255 C. and residence time in the reactor is 0.3 hour. A liquid product stream is continuously withdrawn and passed to a distillation column wherein a mixture of Z-methylene glutaronitrile and 1,4-dicyano butenes are separated as overhead at C. and 22 mm. Hg absolute pressure from a bot toms comprising 1,2,4-tricyano butane, some heavy byproducts and catalyst. The bottoms stream containing 9.9 mols per hour of the tricyanobutane is separated from heavies and catalyst and recycled as part of the feed to the reactor. The overhead fraction is condensed and further distilled in order to separate 0.08 mol per hour of 2-methylene glutaronitrile (containing 2% 1,4-dicyano-1-butene trans) as overhead at C. and 50 mm. Hg absolute pressure and this material is condensed and returned as part of the feed to the reactor. The bottoms stream comprised of a mixture of the cis and trans forms of 1,4-dicyano-l-butene and 1,4-dicyano-2-butene is recovered at a rate of 0.19 mol per hour as product.

What is claimed is:

1. The method of preparing a mixture of at least one 1,4-dicyano butene and Z-methylene glutaronitrile which comprises dehydrocyanating 1,2,4-tricyano butane at a temperature in the range of l00-l000 C.

2. The method of claim 1 wherein the dehydrocyanation is carried out in the presence of a basic catalyst.

3. The method of claim 1 wherein the dehydrocyanation is carried out in the liquid phase.

4. The method of claim 2 wherein the basiccatalyst is an alkali or alkaline earth metal catalysts 5. The method of claim 2 wherein the basic catalyst is a lithium catalyst.

6. The method of claim 2 wherein the basic catalyst is a phosphine catalyst.

'7." The method of claim 3 wherein'the concentration of 1,4-dicyano butenes and Z-methylene glutaronitrile relative to 1,2,4-tricyano butane is maintained at a level not greater than 40 mol percent in the liquid reaction mixture during the dehydrocyanation.

8. The method of claim 7 wherein the, concentration is maintained not greater than 20 molperccnt.

9. The method of claim 7 wherein the concentrationis maintained not greater than 10 mol percent.

10. The method of claim 3 wherein a product mixture of 1,4-dicyano butene and Z-methyleneglutaronitrile is removed as vapor from the reaction mixture and passed directly to a fractional distillation zone, and the 1,4-dicyano butene and Z-methylene glutaronitrile are "recovered by fractional distillation.

11. The method of preparing a 1,4-dicyano butene which comprises isomerizing 2-methyl ene glutaronitrile at a temperature in the range of 100 7 00 C. in the presence of hydrogen cyanide or a hydrogen cyanide precursor capable of providing hydrogen cyanide under the conditions of the isomerization reaction and recovering product 1,4-dicyano butene.

12. The method of claim 11 wherein the 'isomerization is carried out in the presence of a basic catalyst. I

13. The method of claim 11 wherein the isomerization is carried out in the liquid phase. V

14. The method for preparing a 1,4-dicyano'butene which comprises isomerizing Z-methyIene glutaronitrile at a temperature in the range of l0Q-7QQ C. in the presence 17 of hydrogen cyanide and a basic catalyst, and recovering product 1,4-dicyano butene.

15. The method for preparing a 1,4-dicyano butene which comprises isomerizing Z-methylene glutaronitrile at a temperature in the range of 100-700 C. in the presence of 1,2,4-tricyano butane and a basic catalyst, and recovering product 1,4-dicyano butene.

16. The method of claim 12 wherein the basic catalyst is an alkali or alkaline earth metal catalyst.

17. The method of claim 12 wherein the basic catalyst is a lithium catalyst.

18. The method of claim 12 wherein the basic catalyst is a phosphine catalyst.

References Cited UNITED STATES PATENTS 18 3,567,760 3/1971 Feldman et al. 260564.8 D 3,574,702 4/1971 Feldman et al. 260-465.8 D 3,666,766 5/1970 Pedigo et a1 260465.8 D 3,225,083 12/ 1965 McClure 260465.8 D 3,686,264 8/1972 Albanese et al 260465.3 3,697,578 10/1972 Pasquino et al 2604659 3,564,040 2/1971 Downing et a1. 260465.8 R 3,536,748 10/ 1970 Drinkard, Jr. et a1. 2604659 3,522,288 7/1970 Drinkard, Jr. et al.- 260465.9 X

FOREIGN PATENTS 1,097,360 1/1968 Great Britain 260465.8 D

OTHER REFERENCES Doering et al., C. A., 52 (1958), p. 17170.

Hauser et al., J.A.C.S., 82 (1960), pp. 1786-1789. I

Hauser et al., I.A.C.S., 78 (1956), pp. 82-83.

Organic Reactions, vol. 5, 1949, pp. 97-98 (Bruson, Cyanoethylation) The Chemistry of Organic Cyanogen Compounds, Migrdichion, 1947, pp. 219-220.

JOSEPH PAUL BRUST, Primary Examiner