IL26346A - Hydrodimerization process of acrylic compounds - Google Patents

Description

26346/2 Hydrodimerization process of acrylic compounds UCB(UNIQH OHIMIQUB-OHEHISCHB BEDBIJYEJ?)S.A. , C. 25087 The present invention is related to a new process for the hydrodime-rization of acrylic compounds, more particularly to the production of adipo-nitrile from acrylonitrile.

There are several types of processes for the hydrodimerization of acrylonitrile to adiponitrile, either by direct electrolysis or by the use of an amalgam of a reducing metal, a finely divided reducing metal or an organo-metallic complex. The process of the present invention belongs to the second of these categories.

A process for the hydrodimerization of acrylonitrile using sodium amalgam was reported in 1949 (0. BkYER, Angew.Chem.81, (1949) ,238). However, the yield of adiponitrile, referred to the amount of acrylonitrile used, was only 5 · Magnesium amalgam in presence of a methanolic solution has also been proposed (U.S.Patent Specification K8 2,439,308) but the adiponitrile yield, referred to the acrylonitrile used, is also insignificant. More recently (MUNYANTS and VYJiZANKIN, Doklady Akad.Nauk SSR,112,(l97),l2-15) this yield has been brought up to more than GOfo by treating a 2C solution of acrylonitrile in hydrochloric a*cid with potassium amalgam.

Since then, other suggestions have been made to improve IQMTyANT's method (loc.cit.), namely, the use of at least 0.5 mol of alkali metal or alkaline earth metal per mol of acrylonitrile (Canadian Patent Specification N° 649,789, the yield being at least 8 , referred to the amount of acrylonitrile consumed), the use of a polymerization inhibitor, of a salt of a transition metal and of acetone (French Patent Specification 1,289»071» the yield reaching as much as 75 referred to the acrylonitrile used), and the addition of various metallic salts to increase the adiponitrile/propionitrile ratio (Belgian Patent Specification No 644,877).

There is, however, no reference in any of these publications mentioned above to the yield of adiponitrile as referred to the amount of alkali metal or alkaline earth metal consumed.

Now, the hydrodimerization of acrylonitrile in an acid aqueous medium gives rise to considerably important secondary reactions, especially the liberation of hydrogen by the reaction of the reducing metal with the acid present in the reaction medium and the reduction of acrylonitrile to propionitrile.

In the processes described in the publications mentioned above, the first of these reactions is so important that, under the most favorable reaction conditions, a maximum of 30 of the reducing metal employed is used in the actual hydrodimerization of acrylonitrile to adiponitrile, i.e. more than 7<¾£ of it is consumed to form hydrogen. As the alkali metal or alkaline earth metal amalgam is produced by electrolysis, the cost of the electric power required must be taken into account as well as the increase in investment necessary to cover the low yield as referred to the reducing metal. Thus, in the process mentioned, the adiponitrile yield, referred to the amcount of electric power consumed in preparing the amalgam, is at most 3C^. In the description which follows, the expression "power efficiency" is used to represent this concept.

The second of the secondary reactions mentioned above, namely, the reduction of acrylonitrile to propionitrile, is also of importance. Indeed, since adiponitrile is the desired product, operational conditions have to be sought which will provide as high an adiponitrile/'propionitrile ratio as possible.

As will be seen below, the process of the present invention improves the power efficiency of the acrylonitrile hydrodimerization to adiponitrile and gives at the same time excellent yields of adiponitrile as referred to acrylonitrile as well as a high adiponitrile/propionitrile ratio.

According to the present invention, the process of hydrodimerization of acrylic compounds by action of an alkali or alkaline earth metal amalgam in presence of an organic or inorganic acid is characterized by the fact that it is carried out using a reaction medium of liquid consistency containing the acrylic compound, at least one amide and optionally water, the acid concentration being low enough to avoid the formation of hydrogen and to limit that of the hydrogenated product of said acrylic compound.

By acrylic compound is to be understood acrylonitrile, methacrylo-nitrile, acrylic and methacrylic esters, acrylamide and methacrylamide as well as their mixtures.

By reason of the commercial importance of adiponitrile, the present invention is described while referring more particularly to the hydrodimerization of acrylonitrile to adiponitrile, but it is to be understood that the process has a wider scope as is more specifically shown by the Examples 12 to 1β hereafter.

Thus, according to one of its aspects, the present invention is related to a process of hydrodimerization of acrylonitrile to adiponitrile by the action of an amalgam of an alkali metal or alkaline earth metal in the presence of an inorganic or organic acid characterized by the fact that it is carried out using a reaction medium of liquid consistency containing acrylonitrile, at least one amide and optionally water, the acid concentration being low enough to avoid the formation of hydrogen and to limit that of propionitrile.

Applying the methods proposed by the present invention, the adiponitrile yield, referred to the amount of acrylonitrile consumed, is at least 65 and may reach more than 9C > while the adiponitrile yield in relation to the amount of alkali metal or alkaline earth metal consumed (power efficiency) is at least 60 o and may exceed 9Q¾» The amount of metal consumed in the formation of gaseous hydrogen is always less than 10 and often nil. As far as is known, such power efficiencies have not been previously attained in hydrodimerization processes where the source of adiponitrile is exclusively acrylonitrile, which indicates the technical advance and economic interest of the process of the present invention. Furthermore, the adiponitrile/propionitrile ratio is very favorable and lies between 20/l and 50/1 and may even reach and exceed lOO/l.

In the following description, "reaction mixture" or "mixture" means the reaction medium, excluding the alkali metal or alkaline earth metal amalgam.

By alkali metal or alkaline earth metal amalgam, there is meant a mercury amalgam of a metal of Groups la and Ila of the Periodic System, the preferred metal being potassium. The concentration of alkali metal or alkaline earth metal in the amalgam is not critical and may range from 0.01 to 0.5 by weight but it is, in principle, possible to work outside these limits. However, below a concentration of 0.01 , extremely large quantities of mercury have to be used, while it is at present difficult to produce industrially amalgams containing more than 0.5 by weight of amalgamated metal.

The molar potassium/acrylonitrile ratio is determined by the desired acrylonitrile conversion rate. Since the formation of propionitrile requires per mole of converted acrylonitrile, twice as much potassium as that of adiponitrile, it may be necessary, for high conversions, for example, of the order of 90% and over and in cases where the formation of a small quantity of propionitrile is accepted, to use a molar potassiumacrylonitrile ratio of more than one. However, in order to maintain a good power efficiency, it is desirable not to exceed a ratio of 1.5 and preferably not even 1.1.

According to the present invention, at least one amide is used so that, under the reaction conditions, the reaction mixture is of liquid consistency. It is preferable to' se amides of carboxylic acids, which may be un~ substituted or substituted on the nitrogen, for example, formamide, N,N-dimethyl formamide, acetamide, N,N-dimethyl-acetamide, propionamide and the like. Sulfonamides, such as jv-toluene -sulfonamide and amides of inorganic acids, for example, hexamethyl phosphoramide and the like, may also be used. The preferred amide is formamide, a product of low cost which is readily available. The amount of amide used represents, by weight, 10 to % ■> preferably 20 to 0¾ of the reaction mixture. Instead of one amide, a mixture of two or more amides may also be used. The solubility of the amides in the mixture may be improved by the addition of auxiliary solvents, such as dioxane.

The inorganic or organic acid may be used either pure or in solution. The quantity used is frequently stoichiometrically equivalent to the quantity of alkali metal or alkaline earth metal consumed in the reaction. However, in order to avoid the liberation of hydrogen, which would reduce the power efficiency, the acid concentration in the reaction mixture should be between 0.1 and 100 meq (meq = milliequivalent) per liter. When the acid content is less than 0.1 meq/liter, there is an increased risk of secondary reactions, such as polymerization of the acrylonitrile and various cyanoathylation reactions, whereas, when it exceeds the upper limit, tha amount of hydrogen liberated becomes quite large.

In fact, when working within the above-mentioned limits, only minor quantities of high boiling products (cyanoethylation and polymerization products) are formed. Furthermore, the amount of hydrogen liberated is less than VJfo (in mols per equivalent of alkali metal or alkaline earth metal consumed) and is most often nil.

It is also possible to use an inorganic acid, such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, hydrofluoric acid, hydro-bromic acid and the like, or a mono- or polycarboxylic organic acid, such as formic acid, acetic acid, propionic acid, oxalic acid, tartaric acid and the like.

The acrylonitrile concentration in the reaction mixture is between 1 and 8Q¾ by weight, preferably between 5 and GQfo by weight. In the continuous process, the concentration of acrylonitrile may be kept as low as 5^ during the whole course of the reaction.

A. certain amount of water may be present in the reaction mixture, its concentration may vary from 0 to 5Q?o by weight and is preferably between 0 and lOfi by weight.

The technical acrylonitrile used in the hydrodimerization reaction according to the present invention is a product containing a polymerization inhibitor to ensure its stability during storage. The amount of inhibitor added to the product is sufficient to prevent the formation of polymers under the operational conditions. However, a further amount of polymerization inhibitor may be added to the acrylonitrile, for example, hydroquinone or its methyl ether, j£-tert.-butyl-catechol, alpha-amino-anthraquinone, phenothiazine and the like. Such further amount of inhibitor may vary from 0.01 to 1% by weight, referred to the acrylonitrile. The acrylonitrile used may be a commercial product, or it may contain acetonitrile as often does the product directly withdrawn from the purification cycle of an acrylonitrile synthesis unit from propylene, air and ammonia.

During the hydrodimerization of the acrylonitrile, the temperature is between 0 and 50aC, preferably between 10 and 30SC.

The process of the present invention may be carried out disconti-nuously, semi-continuously or entirely continuously; it offers the advantage that the hydrodimarization products can be easily isolated and recovered by the usual methods, such as distillation and extraction. 3-he process of the present invention is not limited to any particular apparatus. Any apparatus may be used which maintains an intimate contact between the amalgam of the reducing metal and the reaction mixture.

In the following Examples, the reactor used consists of a vertical tube filled with Raschig rings and surrounded by a sleeve serving for the thermostatic control of the reaction mixture, the latter being continuously recycled by a pump . The mercury amalgam is introduced into the top of th 2 tube and dispensed in droplets, the used mercury running out through the bottom of the reactor. The filling may be eliuiinated if one of the reaction products precipitates in solid form during the reaction (e.g. potassium chloride, potassium sulfate or potassium acetate). The neutralizing acid is introduced into the circulating reaction mixture by means of a metering pump.

The acid concentration is checked by measurement of the difference of potential existing between a glass electrode immersed in the reaction medium and a saturated calomel electrode. The millivolts are converted into acid concentrations(jnilliequivalents of acid per liter of reaction mixture) by means of a calibration curve.

In the following Examples, which are given for the purpose of illustrating the present invention, "conversion" means the proportion of reagent consumed in relation to the quantity used and "yield" means the proportion of product formed in relation to the reagent actually consumed. All parts and proportions are by weight unless otherwise indicated.

Example 1. 11.84 kg. potassium amalgam containing 17.08 g. potassium (0.144/& potassium/amalgam) is passed through the above-described apparatus, which contains a solution consisting initially of 27·5 g« acrylonitrile ( *8 by weight), 5.5 g. acetic acid, 27.5.g. water, 0.275 g« hydroquinone and 220 g. formamide. Tha temperature is maintained at 202C. At the same time as the amalgam, a stoichiometrically equivalent quantity of glacial acetic acid is added in such a manner that the acid concentration is maintained at 7 meq/liter during the reaction. The experiment lasts 90 minutes. The results obtained are as follows: Acrylonitrile conversion 82.0J Potassium conversion 100^ Adiponitrile yield in relation to acrylonitrile 69.5^ Adiponitrile yield in relation to potassium 68.O0 Propionitrile yield in relation to acrylonitrile 12.4 Propionitrile yield in relation to potassium 26.

Adiponitrile/propionitrile weight ratio 5.5 Gaseous hydrogen produced 2.055b Example 2.

In this Sxample, the water content of the reaction mixture is reduced.

A solution initially containing 23.0 g. acrylonitrile (9·9/& by weight), 4.6 g. glacial acetic acid, 1.5 g. water, 0.23 g. hydroquinone and 205.5 g« formamido is introduced into the reactor. 14.66 kg. potassium amalgam containing 19·5 8· potassium (0.113$ potassium/amalgam) are then passed through it. The temperature is maintained constant at 20°C. and a stoichiometricaUy equivalent quantity of glacial acetic acid is added at the same time as the amalgam so that the acid concentration is maintained at 10 meq/liter.

The experiment lasts 0 minutes. The results obtained are as follows: Acrylonitrile conversion 9¾S Potassium conversion 100 Adiponitrile yield in relation to acrylonitrile 76.0$ Adiponitrile yield in relation to potassium 60.2$ Propionitrile yield in relation to acrylonitrile 20.3 Propionitrile yield in relation to potassium 32.0$ Adiponitrile/propionitrile weight ratio 3.7 Gaseous hydrogen produced 3- 3$ Example 3» In this Example, the experiment is performed in the absence of water and the proportion of acrylonitrile in the reaction mixture is increased.

The mixture treated initially contains 6.0 g» acrylonitrile (34.3$ by weight), .5 g. glacial acetic acid and 179·0 g. formamide. No extra inhibitor is added. Hydrodimerization is effected with 12.34 kg. potassium amalgam containing 17.25 g. potassium (0.1395$ potassium/amalgam). As in the preceding Examples, the temperature is maintained constant at 20°C. and a stoichiometricaUy equivalent quantity of glacial acetic acid is added at the same time as the amalgam so that the acid concentration of the mixture is maintained at 1 meq/liter. The experiment lasts 0 minutes. The following results are obtained: Acrylonitrile conversion 21.9$ Potassium conversion 100$ Adiponitrile yield in relation to acrylonitrile 83$ Adiponitrile yield in relation to potassium 74«¾o Propionitrile yield in relation to acrylonitrile 8.3 Propionitrile yield in relation to potassium 14.45$ Adiponitrile/propionitrile weight ratio 10 Gaseous hydrogen produced 1.4$ Example 4« In this Example, the acetic acid is replaced "by gaseous hydrogen chloride (1.5 meq/liter). The quantities present initially are 27·5 g« acrylo-nitrile (10$ by weight), 27.5 g. water and 220 g. formamide. No extra inhibitor is added. 12.15' k . potassium amalgam containing 18.85 g. potassium (0.147$ potassium/amalgam) is used. A stoichiometrically equivalent quantity of hydrogen chloride is added at the same time as the amalgam so that the acid concentration is maintained at 1.5 meq/liter. The working temperature is 20QC. and the experiment lasts 0 minutes. The results obtained are as follows: Acrylonitrile conversion 85.0$ Potassium conversion 100 Adiponitrila yield in relation to acrylonitrile 78·8 Adiponitrile yield in relation to potassium 75·7$ Propionitrile yield in relation to acrylonitrile 11.55/» Propionitrile yield in relation to potassium 22.2 Adiponitrile/propionitrile weight ratio 6.7 Gaseous hydrogen produced undetermined Example 5.

In this Example, a higher proportion of acrylonitrile is used in the reaction mixture than in Example 3· The mixture treated initially contains 199 S* acrylonitrile (75$ by weight), 5·5 g. glacial acetic acid, 68 g. formamide and 2 g. hydroquinone. Hydrodimerization is effected with 10.3 kg. potassium amalgam containing 14.42 g. potassium (0,140$ potassium/amalgam). A stoichiometrically equivalent quantity of glacial acetic acid is added at the same time as the amalgam so that the acid concentration is 10 meq/liter during the reaction. The experiment lasts 0 minutes. The following results are obtained: Potassium conversion 100$ Adiponitrile yield in relation to potassium 77·6$ Propionitrile yield in relation to potassium 17·3*> Adiponitrile/propionitrile weight ratio 8.85 Gaseous hydrogen produced 0.2$ Example 6.

In this example, the acetic acid is replaced by sulfuric acid and various initial concentrations of acrylonitrile are used.

A solution containing various proportions (see table) of commercial acrylonitrile, formamide and l'o water is introduced into the reactor. A potassium amalgam containing 0. 2$ potassium is then passed through it. The temperature is kept at 20°C. and concentrated sulfuric acid is added at the same time as the amalgam so that the acid concentration is 10 meq/liter during the reaction. Potassium sulfate precipitates as soon as formed and is eliminated at the end of the reaction by filtration. The results obtained for the different acrylonitrile concentrations are shown in the following table: TABLE 6a 6b 6c 6d Initial mixture: acrylonitrile {%) 25 37.5 49 59 formamide ($) 74 61.5 50 40 water ($) 1 1 1 1 Potassium/acrylonitrile molar ratio 0.87 0.68 0.64 0.57 Acrylonitrile conversion ($) 8Θ 73.7 67 52 Potassium conversion ($) 100 100 87.4 65.Ο Adiponitrile yield in relation to acrylonitrile ($) 89 89.2 66.5 48.2 Adiponitrile yield in relation to potassium ($) 90.5 96.8 81.0 68 Propionitrile yield in relation to acrylonitrile ($) 3 2.1 3.6 9.5 Propionitrile yield in relation to potassium ($) 6.1 4.6 8.6 27 Adiponitrile/propionitrile weight ratio 28.8 41.3 18 5 Gaseous hydrogen produced ($) 0 0 0 0 Example 7.

In this example, sodium amalgam is substituted for potassium amalgam and the acid is sulfuric acid.

A solution initially containing 40 commercial acrylonitrile, $ formamide and 5$ water is introduced into the reactor. A sodium amalgam containing 0.12$ sodium is passed through it in such an amount that the sodium/ acrylonitrile molar ratio is 0.63 and concentrated sulfuric acid is added at the same time as the amalgam so that the concentration of the acid is maintained at 10 meq/liter. The temperature is kept at 20flC.

Acrylonitrile conversion 61.9 Sodium conversion 96.2% Adiponitrile yield in relation to acrylonitrile 72.5% Adiponitrile yield in relation to sodium 71.7% Propionitrile yield in relation to acrylonitrile 5.5% Propionitrile yield in relation to sodium 11.6% Adiponitrila/propionitrile weight ratio 12.1 Gaseous hydrogen produced 0 Example 8.

In this example, the amide is dimethylformamide.

A solution initially containing 10% commercial acrylonitrile, 80% dimethylformamide and 10% water is introduced into the reactor. potassium amalgam containing 0.2% potassium is passed through it in such an amount that the potassium/acrylonitrile molar ratio is 1.23 ad concentrated sulfuric acid is added at the same time as the amalgam so that the concentration of the acid is maintained at 1 to 2 raeq/liter. The experiment is carried out at 0SC.

Acrylonitrile conversion 95·2% Potassium conversion 75«0% Adiponitrile yield in relation to acrylonitrile 74» % Adiponitrile yield in relation to potassium 73· % Propionitrile yield in relation to acrylonitrile 9«6% Propionitrile yield in relation to potassium 19«4% Adiponitrile/propionitrile weight ratio 7·8 Gaseous hydrogen produced 0 Example 9.

In this example, the amide is acetamide.

A solution initially containing 24.4% acrylonitrile, 59·5% acetamide and 1 .6 water is introduced into the reactor. A potassium amalgam containing 0.2% potassium is thea passed through it in such an amount that the potassium/ acrylonitrile molar ratio is 0.66 and concentrated sulfuric acid is added at the same time as the amalgam so that the concentration of the acid is maintained at 3 to 5 meq/liter. The experiment is carried out at 20°C.

Acrylonitrile conversion Potassium conversion Adiponitrile yield in relation to acrylonitrile 58.5$ Adiponitrile yield in relation to potassium 59· 5$ Propionitrile yield in relation to acrylonitrile 13.8$ Propionitrile yield in relation to potassium 27.6$ Adiponitrile/propionitrilo weight ratio 4.2 Gaseous hydrogen produced 0 Examploi 10.

In this example, the amide is jj-toluene-sulfonamide mixed with dioxane.

A solution initially containing 2¾¾ acrylonitrile, 36· 7$ j-toluene-sulfonamide, 33.9$ dioxane and 6.4$ water is introduced into the reactor. A potassium amalgam containing 0.2 potassium is then passed through it in such an amount that the potassium/acrylonitrile molar ratio is 0,66 and concentrated sulfuric acic is added at the same time as the amalgam so that the concentration of the acid is maintained at 10 meq/liter. The experiment is carried out at 20^0.

Acrylonitrile conversion 44.5% Potassium conversion 100$ Adiponitrile yield in relation to acrylonitrile 0.9$ Adiponitrile yield in relation to potassium 27.6$ Propionitrile yield in relation to acrylonitrile 52.8$ Propionitrile yield in relation to potassium 71.5$ Adiponitrile/propionitrile weight ratio 0.8 Example 11.

This example illustrates a continuous process.

A feed solution (constituted by 5 $ formamido, 4 $ acrylonitrile and 1$ normal aqueous solution of sulfuric acid), the amalgam containing 0.2$ potassium and the sulfuric acid meant to neutralize the consumed potassium are continuously introduced into the above described reactor. The exhausted mercury and the reaction suspension containing 10$ potassium sulfate are continuously withdrawn. The suspension is filtered in a continuous manner and a determined portion of the filtrate is recycled with the above described reagents in such a way that a 10$ concentration of potassium sulfate is maintained in the reactor and that the desired conversion of acr lonitrile is reached. The filtrate contains 57· 5$ formamide, 12.5$ acrylonitrile, adiponitrile , 0.7$ propionitrile and 1$ water, the balance being constituted by high boiling compounds. The acid concentration is automatically maintained at 10 meq/liter by means of a pH-meter controlled valve. Temperature is kept at 18-20aC.

Acrylonitrile conversion 68.8t> Potassium conversion 100$ Adiponitrile yield in relation to acrylonitrile 8 .4 Adiponitrile yield in relation to potassium 89$ Propionitrile yield in relation to acrylonitrile 2.5$ Propionitrile yield in relation to potassium $ Adiponitrile/propionitrile weight ratio 35· 8 Example 12.

In this example, acrylonitrile is replaced by ethyl acrylate.

A solution initially containing 20$ ethyl acrylate, 79$ formamide and 1$ water is introduced into the reactor. A potassium amalgam containing 0.2$ potassium is then passed through it in such an amount that the potassium/ethyl acrylate molar ratio is 0.945 an concentrated sulfuric acid is added at the same time as the amalgam so that the concentration of the acid is maintained at meq/liter. Temperature is kept at 208C.

Ethyl acrylate conversion 88$ Potassium conversion 89»2$ Diethyl adipate yield in relation to ethyl acrylate 80.6$ Diethyl adipate yield in relation to potassium 75$ Ethyl propionate yield: not detectable by gas chromatography.

Example 15.

This example describes the hydrodimerization of an equimolecular mixture of acrylonitrile and ethyl acrylate.

A solution initially containing 59$ formamide, 40$ equimolecular mixture of acrylonitrile and ethyl acrylate and 1$ water is introduced into the reactor. A potassium amalgam containing 0.2$ potassium is then passed through it in such an amount that the potassium/total amount of two monomers molar ratio is 0.58 and concentrated sulfuric acid is added at the same time as thj amalgam so that the concentration of the acid is maintained at 10 meq/liter. Temperature is kept at 20^0.

Acrylonitrile Ethyl acrylate Potassivua Conversion 55 $ 65. $ 100 $ Adiponitrile yield 22.9$ 11 « 5$ Diethyl adipate yield 51 $ 18.5 Ethyl cyanopentanoate yield 57· 3$ 48.1$ 57 $ Prop onitrile yield .7 ¾ 6.7$ Ethyl propionate yield 0 0 Example 14.

The example describes the hydrodimerization of an acrylonitrile-methacrylonitrile mixture.

A solution initially containing 59$ fonnamide, 40 equimolecular mixture of acrylonitrile and methacrylonitrile and 1$ water is introduced into the reactor. A potassium amalgam containing 0.2$ of potassium is then passed through it in such an amount that the potassium/total amount of two monomers molar ratio is 0.68 and concentrated sulfuric acid is added at the same time as the amalgam so that the concentration of the acid is maintained at 10 meq/liter. Temperature is kept at 20BC.

Acrylonitrile Methacrylonitrile Potassium Conversion 8. $ 17 $ 75 $ Adiponitrile yield 6 . $ 50 $ 2,7-dimethyladiponitrile yield traces traces 2-methyladiponitrile yield 11.7$ 67.6$ 16.7$ Propionitrile yield 0 0 Isobutyronitrile yield 21.2$ 5· 3$ Example 15.

This example describes the hydrodimerization of methacrylonitrile.

A solution initially containing 74$ formamide, 25$ methacrylonitrile and 1% water is introduced into the reactor. A potassium amalgam containing 0.2$ of potassium is then passed through it in such an amount that the consumed potassiumnethacrylonitrile molar ratio is 0.81 and concentrated sulfuric acid is added at the sano time as the amalgam so that the concentration of the acid is maintained below 5 meq/liter. Temperature is kept at 20sC. Analysis is carried out by gas chromatography wherein dimethyladiponitrile appears in the form of twin peaks.

Methacrlonitrile conversion 49.3$ Dimeth ladiponitrile yield in relation to methacrylonitrile 49 $ Dimethyladiponitrile yield in relation to potassium 29 % Isobutyronirile yield in relation to mdthacrylonitrile 58.5% Isobutyronitrile yield in relation to potassium 70 $ Dimethyladiponitrilo/isobutyronitrile weight ratio 0.Θ2 Example 16.

This example is a variation of Example 15· solution initially containing 83$ dimthylformamide, 15$ methacrylonitrile and 2$ water is introduced into the reactor. A potassium amalgam containing 0.2$ potassium is then passed through it in such an amount that the consumed potassiummethacrylonitrile molar ratio is 0.3 and concentrated sulfuric acid is added at the same time as the amalgam so that the concentration of the acid is maintained below 5 meq/liter. Temperature is kept at 40BC.

Methacrylonitrile conversion 33 $ Dimethyladiponitrile yield in relation to methacrylonitrile 33· 5$ Dimethyladiponitrile yield in relation to potassium 36·4 Isobutyronitrile yield in relation to methacrylonitrile 19·5$ Isobutyronitrile yield in relation to potassium 41» 6$ Dimethyladiponitrile/isobutyronitrile weight ratio 1.72

Claims (8)

1. H&VIHS HOW particularly described and ascertained the nature s ou said invention and in what manner the earn© is to be performed* e declare %at wha we claim iss~ 1. Process of hydrodimerization of acrylic compounds by the action of an alkali metal or alkaline earth metal amalgam in presence of an inorganic or organic acid which comprises reacting in a medium of liquid consistency containing the acrylic compound s&lected from the group consisting of aciylonitrile, methacrylonitrile, acrylic and methacrylic esters, acrylamide and methacryl-amide, at least one amide selected from the group consisting of nitrogen substituted and unsubstituted carboxylic acid amides, sulfonamides and inorganic amides and optionally water, the concentration of the acid in the reaction medium being sufficiently weak ao as to prevent the formation of hydrogen and to limit that of the hydrogenated product of said acrylic compound.

2. Process of hydrodimerization of acrylonitrile by the action of an alkali metal or alkaline earth metal amalgam in presence of an inorganic or organic acid which comprises reacting in a medium of liquid consistency containing acrylonitrile, at least one amide selected from the group consisting of nitrogen substituted and unsubstituted carboxylic acid amides, sulfonamides and inorganic amides and optionally water, the concentration of the acid in the reaction medium being sufficiently weak so as to prevent the formation of hydrogen and to limit that of propionitrile.

3. Process as claimed in claim 1, wherein the concentration of the metal in the amalgam ranges from 0.Q1 to 0.¾¾ by weight.

4. Process as claimed in claim 1, wherein the metal of the amalgam is potassium.

5. Process as claimed in claim 1, wherein the potassium/acrylic compound molar ratio does not exceed 1.5/1·

6. Process as claimed in claim 1, wherein the potassium/acrylic compound molar ratio does not exceed l.l/l.

7. Process as claimed in claim 1, wherein the amide is formamide.

8. Process as claimed in claim 1, wherein the acid is selected from the group consisting of acetic acid,hydrochloric acid and sulfuric acid. 9· Process as claimed in claim 1, wherein the concentration of the acid in the reaction mixture is maintained between 0.1 and 100 milliequivalents per liter of said reaction mixture. - - 10. Process as claimed in claim 1, wherein the concentration of the acrylic compound in the initial mixture is comprised between 1 and 80^ by weight. 11. Process as claimed in claim 1, wherein the concentration of the acrylic compound in the initial mixture is comprised between 5 and 60 by weight. 12· Process as claimed in claim 1, wherein the amount of water in the initial mixture is comprised between 0 and 50$ by weight. 15. Process as claimed in claim 1, wherein the amount of water in the initial mixture is comprised between 0 and 10 by weight. 14· Process as claimed in claim 1, wherein hydrodimerization is carried out at a temperature comprised between 0 and 50*C. 15· Process as claimed in claim 1, wherein hydrodimerization is carried out at a temperature comprised between 10 and 3 °C» Bated this 15th day of Augus , 1966 for the Applicants BR. REINHOLD COM & 00. - 2 -