Production of aliphatic secondary amines

Abstract: Disclosed is a process for preparing an unsaturated aliphatic primary or secondary amine from the corresponding unsaturates aliphatic nitrile without hydrogenating an olefinic bond in the molecule. The process employs a catalyst which is a combination of copper and specific metal.

Description: The present invention relates to a process for preparing an aliphatic secondary amine from an aliphatic nitrile. An aliphatic secondary amine, especially one containing an unsaturated group, is very useful for many applications or as intermediate. The amine is generally prepared by hydrogenating an unsaturated aliphatic nitrile in the presence of a catalyst for hydrogenation. For producing the aliphatic secondary amine, the use of a copper-chromium catalyst is proposed in UK Patent 773,432. However, since the copper-chromium catalyst is poor in catalyst activity, it takes a long time to terminate the reaction. Japanese Kokai Publication (unexamined) 55-9018 proposes a nickel containing catalyst which, however, hydrogenates a unsaturated group in the molecule as well as a nitrile group. Accordingly, it is difficult to selectively produce the unsaturated secondary amine. In order to resolve the above problems, Japanese Kokai Publication (unexamined) 62-175445 discloses that the hydrogenation is carried out in the presence of a nickel containing catalyst and a carboxylic amide. In this reaction, the carboxylic amide is brought into the reaction product and is quite difficult to remove or separate from the product. For producing an aliphatic primary amine, Japanese Patent Publication (examined) 38-21353 teaches that the hydrogenation of the unsaturated aliphatic nitrile is carried out in the presence of Raney nickel or Raney cobalt as well as an alkali (alkali metal hydroxide) or ammonia. This method also hydrogenates not only a nitrile group but also an unsaturated groups. It therefore is difficult to selectively produce an unsaturated primary amine. It has been found that, when copper is combined with a specific metal and employed as catalyst for hydrogenation, an unsaturated aliphatic secondary amine is selectively prepared from an unsaturated aliphatic nitrile, wherein the olefinic group remains unsaturated in the molecules. The process is applicable to the production of an aliphatic secondary amine having an unsaturated group, and is also effective for producing the saturated aliphatic secondary amine from the corresponding saturated nitriles. Accordingly, the present invention provides a process for preparing an aliphatic secondary amine comprising reacting a C₈-C₂₄ aliphatic nitrile with hydrogen at a temperature of from 150 to 250 °C and a hydrogen pressure of 1.013-50.662 bar (1 to 50 atm, gauge pressure) in the presence of a catalyst for hydrogenation while removing produced ammonia, wherein the catalyst contains (a) copper and (b) at least one metal selected from the group consisting of manganese, iron, cobalt, nickel and zinc in a metal weight ratio (a/b) of from 99/1 to 10/90. The catalyst for hydrogenation of the present invention comprises (a) copper and (b) at least one metal selected from the group consisting of manganese, iron, cobalt, nickel and zinc. The metal weight ratio of a/b is within the range of from 99/1 to 10/90, preferably from 99/1 to 50/50. If the metal weight ratio is outside the above range, it may hydrogenate-the olefinic group in the molecule, and production efficiency becomes poor. The catalyst may contain (c) an alkali metal or an alkali earth metal in a metal weight ratio (a/c) of from 1/1 to 1/0.01, preferably from 1/0.5 to 1/0.01. Typical examples of the alkali metals are lithium, sodium, potassium, rubidium and cesium. Typical examples of the alkali earth metals are magnesium, calcium, strontium and barium. If the amount of the component (c) is more than 1/1 in a metal weight ratio based on the amount of (a), catalyst activity becomes poor. The catalyst may further contain (d) at least one metal selected from the group consisting of aluminum, molybdenum and tungsten. The metal weight ratio of a/d is preferably within the range of from 1/1 to 1/0.01. If the amount of the component d exceeds 1/1, catalyst activity is poor. The metal mentioned above may be contained in the catalyst of the present invention in any form , such as the metal itself, as a metal oxide, metal hydroxide, metal salt and metal ion. In other words, the metals contained in the catalyst of the present invention are required to come into contact with the aliphatic nitrile in the reaction system, irrespective of the form in which the metal is employed. The catalyst of the present invention can be used in any form, such as in the form of the metal itself, as a metal-containing material (such as, metal oxide, metal hydroxide, metal salt and metal ion) which may be carried on a carrier. The metal contained in the catalyst may be a complex stabilized by chelation with an aliphatic carboxylic acid or a suitable ligand. The catalyst can be a combination of the above mentioned forms. It is preferred to use the metal carried on a suitable carrier, because of the stability of the catalyst metal and the resistance against a catalyst poison. Such carriers are alumina, silica, silica-alumina, diatmaceous earth, active carbon, zeolite and the like. The metal may be preferably present in the carrier in an amount of from 5 to 70 % by weight. A method for bringing the catalyst metal on the carrier is known in the art, for example an impregnating method wherein a carrier is poured in a solution containing a suitable metal salt for impregnating: a method wherein an alkali solution containing ammonia, sodium hydroxide, sodium carbonate and the like is added to a solution containing a carrier and a catalyst metal salt to precipitate the metal salt on the carrier; a method wherein an alkali solution and a metal salt solution are simultaneously added to a carrier slurry to precipitate the metal salt on the carrier; or an ion-exchange method wherein a catalyst metal is ion-exchanged with sodium or potassium in zeolite. The reaction of the present invention can be carried out by contacting the catalyst for hydrogenation with the aliphatic nitrile. The contact can be done in an art-known method. For example, since many aliphatic nitriles are liquid in ambient temperature, the above catalyst may be simply mixed with the aliphatic nitrile. After finishing the reaction, the catalyst can be separated from the reaction product. The aliphatic nitrile employed in the present invention is a saturated or unsaturated aliphatic nitrile having 8 to 24 carbon atoms, such as capronitrile, lauronitrile, coconut oil fatty acid nitrile, beef fatty acid nitrile, stearonitrile, cleonitrile, linolonitrile, linoleonitrile, eruconitrile, behenonitrile or a mixture thereof. A nitrile having a branch chain which is prepared from a synthetic fatty acid having a branch chain can also be used. The reaction can be carried out by charging the aliphatic nitrile and the catalyst for hydrogenation in a reaction vessel having a hydrogen introducing tube, a tube for sampling and a drain tube for the produced ammonia. The amount of the catalyst is not limited, but the preferred amount is generally from 1 to 5 % by weight based on the amount of the nitrile. The reaction vessel is filled with nitrogen and then substituted for hydrogen. The hydrogen pressure is controlled within 1.013-50.662 bat (1 to 50 atm, gauge pressure), preferably 5.006 to 30.397 bar (5 to 30 atm) during the reaction. The reaction vessel is then heated to a reaction temperature of from 150 to 250 °C, preferably from 180 to 230 °C. Ammonia produced during the reaction is continuously or intermittently drained off from the reaction vessel. After the completion of the reaction, the reaction product is distilled or filtered to separate from the catalyst. According to the present invention, a long chain unsaturated aliphatic amine can be selectively prepared employing a specific catalyst in a very small amount from the corresponding unsaturated aliphatic nitrile in a short period of time. The catalyst employed in the present invention can keep their high catalyst activity after being used several ten times. EXAMPLES The present invention is illustrated by the following examples which, however, are not construed as limiting the invention to their details. Example 1 and Comparative Example 1 A one liter flask was charged with 500 g of ion-exchanged water, 20 g of synthetic zeolite (MS-5A available from Toso Company), 30 g of copper nitrate and 10 g of zinc nitrate, and heated to 90 °C with stirring. At that temperature, 167 g of a 10 % sodium carbonate aqueous solution was added dropwise and then aged for one hour. The precipitate was filtered and rinsed with water. It was then dried at 100 °C for 10 hours and baked at 700 °C for 2 hours to form a copper-zinc catalyst carried on synthetic zeolite. Next, eruconitrile (90 % purity) was hydrogenated using the obtained catalyst as follow. For comparison, the same reaction was conducted using the copper-chromium catalyst which is proposed in UK Patent 773.432. A one liter reaction vessel having a hydrogen inlet, a sampling tube and an outlet for produced ammonia was charged with 400 g of eruconitrile and 4 g of the catalyst mentioned above and filled with nitrogen. Hydrogen was then introduced and pressured to 20.265 bar (20 atm). The reaction vessel was heated to 180 °C, keeping the hydrogen pressure at 20.265 bar (20 atm), and the reaction was started. Ammonia produced during the reaction was intermittently drained from the reaction vessel. After the completion of the reaction, the reaction product was filtered to separate from the catalyst. The reaction product was analyzed and the results are shown in Table 1. It is apparent that the catalyst of Example 1 has higher activity and can more selectively produce a long-chain unsaturated aliphatic secondary amine without hydrogenating the olefinic bond in a molecule, in comparison with Comparative Example 1. Example 2 and Comparative Example 2 A copper-cobalt catalyst was prepared as broadly described in Example 1, with the exception that cobalt nitrate was employed instead of zinc nitrate. The catalyst has a cooper/cobalt ratio of 5/1 and a metal support ratio of 20 % (wherein metal support ratio means the metal content (wt %) based on the catalyst.). Next, oleonitrile (96 % purity) was hydrogenated using the obtained catalyst as described in Example 1, with the exception that amounts and reaction conditions are as follows. For comparison, the same reaction was conducted using the copper-chromium catalyst which is proposed in UK Patent 773,432. The results are shown in Table 2. Oleonitrile 400 g Copper-cobalt catalyst (Ex.2) 8 g Copper-chromium catalyst (Comparative Ex.2) 8 g Reaction temperature 200 °C Hydrogen pressure 5.066 bar (5 atm, gauge pressure) It is apparent that the catalyst of Example 2 has higher activity and can more selectively produce a long-chain unsaturated aliphatic secondary amine without hydrogenating the unsaturated double bond in a molecule, in comparison with Comparative Example 2. Example 3 and Comparative Example 3 A copper-nickel-potassium catalyst was prepared as broadly described in Example 1, with the exception that nickel nitrate and potassium nitrate were employed instead of zinc nitrate. The catalyst has a copper/nickel/potassium ratio of 7/1/1 and a metal support ratio of 30 %. Next, linolonitrile (90 % purity) was hydrogenated using the obtained catalyst as described in Example 1, with the exception that amounts and reaction conditions are as follows. For comparison, the same reaction was conducted using the copper-chromium catalyst which is proposed in UK Patent 773,432. The results are shown in Table 3. Linolonitrile 400 g Copper-nickel-potassium(Ex.3) 12 g Copper-chromium catalyst (Comparative Example 3) 12 g Reaction temperature 210 °C Hydrogen pressure 25.331 bar (25 atm, gauge pressure) It is apparent that the catalyst of Example 3 has higher activity and can more selectively produce a long-chain unsaturated aliphatic secondary amine without hydrogenating the unsaturated double bond in a molecule, in comparison with Comparative Example 3. Example 4 and Comparative Example 4 A copper-iron-barium catalyst was prepared as broadly described in Example 1, with the exception that iron nitrate and barium nitrate were employed instead of zinc nitrate. The catalyst has a copper/iron/barium ratio of 8/1/0.5 and a metal support ratio of 20 %. Next, linolenonitrile (90 % purity) was hydrogenated using the obtained catalyst as described in Example 1, with the exception that amounts and reaction conditions are as follows. For comparison, the same reaction was conducted using the copper-chromium catalyst which is proposed in UK Patent 773,432. The results are shown in Table 4. Linolenonitrile 400 g Copper-iron-barium (Ex.4) 12 g Copper-chromium catalyst (Comparative Example 4) 12 g Reaction temperature 210 °C Hydrogen pressure 35.463 bar (35 atm, gauge pressure) It is apparent that the catalyst of Example 4 has higher activity and can more selectively produce a long-chain unsaturated aliphatic secondary amine without hydrogenating the unsaturated double bond in a molecule, in comparison with Comparative Example 4. Examples 5 and 6 A copper-manganese-aluminum catalyst was prepared as broadly described in Example 1, with the exception that manganese nitrate and aluminum nitrate were employed instead of zinc nitrate. The catalyst has a copper/manganese/aluminum ratio of 8/1/0.5, a metal support ratio of 20 %. Next, caprylonitrile (98 % purity) and branched nitrile (a branched nitrile having 18 carbon atoms derived from branched fatty acid available from Emery Company as Emasol 871) were hydrogenated using the catalyst obtained in Example 1, with the exception that amounts and reaction conditions are as follows. The results are shown in Table 5. Caprylonitrile (Ex.5) 400 g or Branched nitrile (Ex.6) 400 g Copper-manganese-aluminum 12 g Reaction temperature 210 °C Hydrogen pressure 25.331 bar (25 atm, gauge pressure) It is apparent that the catalyst of Examples 5 and 6 has higher activity and can more selectively produce a long-chain unsaturated aliphatic secondary amine without hydrogenating the unsaturated olefinic bond in a molecule. Example 7 This example shows the durability of the activity and selectivity of the catalyst obtained in Example 1 after repetitive cycles (5 times) of catalyst use and its successive recovery. Oleonitrile (90 % purity) was hydrogenated five times, with the exception that amounts and reaction conditions are as follows. The results are shown in Table 6. Catalyst/oleonitrile (wt %) 2/100 Reaction temperature 210 °C Hydrogen pressure 5.066 bar 5 atm, gauge pressure) It is apparent that the catalyst has a good activity and can selectively produce a long-chain unsaturated aliphatic secondary amine without hydrogenating the olefinic bond in a molecule, even after repeatedly being used five times. Production Example 6 The catalyst had a metal weight ratio (Cu/Zn) of 9/1. Example 8 A one liter reaction vessel having a hydrogen inlet, a sampling tube and an outlet for produced ammonia was charged with 300 g of oleonitrile or stearonitrile, sodium hydroxide (0.2 % by weight) and the catalyst mentioned above and filled with nitrogen. Hydrogen was then introduced and pressured to a pressure as shown in Table 7. The reaction vessel was heated to a temperature as shown in Table 7, keeping the hydrogen pressure, and the reaction was started. After the completion of the reaction, the reaction product was filtered to separate from the catalyst. The reaction product was analyzed and the results are shown in Table 7. Comparative Examples 5 and 6 The same experiments were conducted as broadly described in Example 8, with the conditions as shown in Table 7. The analysis and double bond retention are shown in Table 7. It is apparent that the catalyst of Example 8 has higher activity and can more selectively produce a long-chain unsaturated aliphatic secondary amine without hydrogenating the unsaturated double bond in a molecule, in comparison with Comparative Examples 5 and 6.

Claims: A process for preparing an aliphatic secondary amine comprising reacting a C₈-C₂₄ aliphatic nitrile with hydrogen at a temperature of 150 to 250 °C and a hydrogen pressure of 1.013 to 50.662 bar (1 to 50 atm, gauge pressure) in the presence of a catalyst for hydrogenation while removing produced ammonia, wherein the catalyst contains (a) copper and (b) at least one metal selected from the group consisting of manganese, iron, cobalt, nickel and zinc in a metal weight ratio (a/b) of from 99/1 to 10/90. The process according to Claim 1 wherein said catalyst further contains (c) an alkali or alkali earth metal in a metal weight ratio (a/c) of from 1/1 to 100/1. The process according to Claim 1 wherein said catalyst further contains (d) at least one metal selected from the group consisting of aluminum, molybdenum and tungsten in a metal weight ratio (a/d) of from 1/1 to 1/0.01.

Inventors: ABE HIROSHI, KATOH TOHRO, SOTOYA KOHSHIRO, TAJIMA HISAKAZU, ABE, HIROSHI, KATOH, TOHRO, SOTOYA, KOHSHIRO, TAJIMA, HISAKAZU
Applicants: KAO CORP, KAO CORPORATION
Application year: 1989
Main classification: C07C209
IPC codes: C07C209, B01J23