Process for the preparation of hexamethylenediamine by hydrogenation of adiponitrile in the presence of raney nickel and a basic cocatalyst

Abstract

The invention relates to a process for the preparation of hexamethylenediamine by hydrogenation of adiponitrile in the presence of a Raney nickel catalyst and a basic cocatalyst containing potassium hydroxide, wherein the basic cocatalyst contains a further basic compound selected from the group consisting of an alkali metal hydroxide, an earth alkali metal hydroxide and an ammonium hydroxide.

Description

Technical Field

[0001] This invention relates to a method for preparing hexamethylenediamine by hydrogenation of adiponitrile in the presence of a Raney nickel catalyst and a basic co-catalyst. Background Technology

[0002] Hexamethylenediamine is a compound used in a variety of applications, the main ones being the preparation of polyamides such as poly(hexamethylene adipamide) (more commonly known as PA 6,6) and hexamethylene diisocyanate.

[0003] Several methods have been proposed for the preparation of hexamethylenediamine, which typically involves the hydrogenation of adiponitrile (tetramethylenedicyanate) in the presence of a hydrogenation catalyst. Industrially, two types of methods are used, employing different catalysts and different temperature and pressure conditions.

[0004] Therefore, the first type of hydrogenation method used and documented in the literature involves the hydrogenation of nitrile compounds using, for example, ruthenium-based catalysts in the presence of ammonia and under high pressure. Iron-based catalysts are also used under high pressure and high temperature.

[0005] The second type of method involves the hydrogenation of nitrile compounds under pressure and at non-high-temperature conditions, such as 25°C and 80 bar, in the presence of an alkaline compound and a Raney nickel-based catalyst. In this latter type of method, the hydrogenation of the nitrile compound to an amine is carried out in the presence of a catalyst based on optionally doped Raney nickel. These catalysts are prepared by leaching aluminum from a Ni-Al alloy in a strongly alkaline medium. The resulting catalyst consists of agglomerates of nickel microcrystals, exhibiting a high specific surface area and variable residual aluminum content.

[0006] It is known that adiponitrile can be hydrogenated to produce a cyclic diamine—diaminocyclohexane (DCH). However, DCH is particularly troublesome because its boiling point is close to that of the target amine, making it difficult to separate.

[0007] Industrially, there is a need to optimize methods for the hydrogenation of adiponitrile to hexamethylenediamine using Raney nickel catalysts, particularly regarding the activity, selectivity, and deactivation behavior of the final catalyst. Specifically, it is important to limit the formation of diaminocyclohexane to obtain hexamethylenediamine that can be purified with minimal capital cost and energy consumption.

[0008] US2003 / 0144552 A1 discloses a method for hydrogenating adiponitrile to hexamethylenediamine in a solution containing hexamethylenediamine and KOH in the presence of chromium-doped Raney nickel. The use of other hydroxides is not described.

[0009] One object of the present invention is to provide a method for preparing hexamethylenediamine by hydrogenation of adiponitrile in the presence of a Raney nickel catalyst, characterized in that a small amount of diaminocyclohexane (DCH) is formed as a byproduct. Summary of the Invention

[0010] The objective is achieved by a method for preparing hexamethylenediamine by hydrogenation of adiponitrile in the presence of a Raney nickel catalyst and an alkaline co-catalyst containing potassium hydroxide, wherein the alkaline co-catalyst comprises other alkaline compounds selected from alkaline hydroxides, alkaline earth metal hydroxides, and ammonium hydroxide. Detailed Implementation

[0011] Furthermore, the basic hydroxides are hydroxides of Li, Na, Rb, and Cs. The alkaline earth metal hydroxides are hydroxides of Mg, Ca, Sr, and Ba.

[0012] In one embodiment, the basic co-catalyst comprises cesium hydroxide (CsOH) as another basic compound.

[0013] In a preferred embodiment, the alkaline co-catalyst comprises barium hydroxide Ba(OH)2 as another alkaline compound.

[0014] In other preferred embodiments, the alkaline co-catalyst comprises ammonium hydroxide of the general formula NR4OH, wherein each R is independently an alkyl group having 1 to 16 carbon atoms, preferably 1 to 4 carbon atoms.

[0015] In a particularly preferred embodiment, each R in NR4OH is independently methyl, ethyl, propyl, or butyl.

[0016] In a highly preferred embodiment, each R in NR4OH is a methyl group, meaning the basic co-catalyst comprises tetramethylammonium hydroxide as another basic compound.

[0017] In another highly preferred embodiment, each R in NR4OH is n-butyl, meaning the basic co-catalyst comprises tetra(n-butyl)ammonium hydroxide as another basic compound.

[0018] Preferably, the alkaline co-catalyst comprises 50 to 95 mol% KOH and 5 to 50 mol% other alkaline compounds. More preferably, the alkaline co-catalyst comprises 70 to 90 mol% KOH and 10 to 30 mol% other alkaline compounds. In a particularly preferred embodiment, the alkaline co-catalyst comprises 75 to 85 mol% KOH and 15 to 25 mol% other alkaline compounds.

[0019] Hydrogenation reactions are typically carried out in the presence of a solvent advantageously composed of the amine obtained by hydrogenation. Therefore, in the case of hydrogenating adiponitrile, hexamethylenediamine is advantageously used as the main component of the reaction medium. The concentration of the amine in the reaction medium is advantageously 50% to 99% by weight, preferably 60% to 99% by weight, based on the liquid phase of the hydrogenation reaction medium.

[0020] The hydrogenation reaction is preferably carried out in the presence of water, which is another component of the reaction medium. The water is typically present in the liquid phase of the total reaction medium in an amount of less than or equal to 50% by weight, advantageously less than or equal to 20% by weight, and more preferably from 0.1% to 15% by weight.

[0021] The amount of alkali to be added is determined to have at least 0.1 mol alkali per kg nickel, preferably 0.1 to 2 mol alkali per kg nickel, and more advantageously 0.3 to 1.5 mol alkali per kg nickel.

[0022] For example, hydrogenation can be carried out in hexamethylenediamine in an aqueous solution containing 1 to 20 wt%, preferably 5 to 15 wt%, of an alkaline co-catalyst, based on the total amount of the reaction medium.

[0023] The hydrogenation reaction is typically carried out at a temperature of less than or equal to 150°C, for example, from 50°C to 150°C, preferably less than or equal to 120°C, and more preferably less than or equal to 100°C. The reaction temperature is most preferably from 50°C to 100°C.

[0024] The hydrogen pressure in the reactor is typically 1 to 100 bar (0.10 and 10 MPa), preferably 10 to 50 bar (1 to 5 MPa).

[0025] The Raney nickel catalyst used in this invention may advantageously contain one or more other elements, commonly referred to as dopants, such as chromium, titanium, molybdenum, tungsten, manganese, vanadium, zirconium, iron, zinc, and more generally elements from groups IIB, IVB, IIIB, VB, VIB, VIIB, and VIII of the periodic table. Of these doping elements, chromium, iron, and / or zinc, or mixtures of these elements, are considered most advantageous and are typically present at a concentration of less than 10% by weight, preferably less than 5% by weight (relative to Raney nickel metal). For example, the concentration of iron may be 1 to 2% by weight, the concentration of chromium may be 0.5 to 5% by weight, and the concentration of zinc may be 0.5 to 5% by weight.

[0026] Raney catalysts typically contain trace amounts of a metal present in the alloys used to prepare the catalyst. Therefore, aluminum is particularly present in these catalysts. The concentration of aluminum can be from 2% to 10% by weight.

[0027] The optionally doped Raney nickel catalyst is typically derived from molten Ni-Al precursor alloys (Ni content, for example, 28 to 59 wt%), to which metallic dopant elements, preferably iron, chromium, and zinc, are added according to a doping method known as "metallurgical" doping. After cooling and grinding, the doped precursor alloy is subjected to an alkaline attack in a conventional manner, which results in the removal of more or less aluminum and optionally some of the dopant elements. The starting alloy used is advantageously selected from binary nickel / aluminum compositions in the form of NiAl3, Ni2Al3, and pre-eutectic Al / NiAl3.

[0028] Dopant can also be introduced via "chemical" doping: by impregnating the Raney nickel catalyst with a precursor solution containing the dopant element, by precipitating the dopant element on the Raney nickel catalyst, or by introducing a precursor compound of the dopant during alkaline impregnation of the Raney alloy.

[0029] The present invention is further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention thereto.

[0030] Example

[0031] Example 1: A General Method for Measuring Catalytic Activity

[0032] In a dry N2 atmosphere, 0.48 g of Raney nickel catalyst was stirred with 7.3 g of water, 65.55 g of pure hexamethylenediamine, and 55 μL of 7 mol / L potassium hydroxide aqueous solution, corresponding to 0.8 mol OH- / kg Ni. The temperature was increased at 80 °C and a total hydrogen pressure of 25 bar. 2.5 g of adiponitrile (ADN) was added in a single step to the autoclave and hydrogenated. Under those operating conditions, the catalytic activity was 111 × 10⁻⁶. -5 mol H2 / g 催化剂 / s.

[0033] Example 2: A General Method for Selective Measurement

[0034] In a dry N2 atmosphere, 3 g of Raney nickel catalyst was stirred with 4.5 g of water, 40.5 g of pure hexamethylenediamine, and 345 μL of 7 mol / L potassium hydroxide aqueous solution, corresponding to 0.8 mol OH- / kg Ni. The temperature was increased at 80 °C and a total hydrogen pressure of 25 bar. 30 g of adiponitrile (ADN) was added dropwise to the autoclave at a mass flow rate of 10 g / h and hydrogenation was carried out. After 3 hours, the crude hexamethylenediamine produced was analyzed by gas chromatography. Under those operating conditions, 0.1812% 1,2-diaminocyclohexane (DCH) was produced.

[0035] Example 3: A General Method for Measuring Catalyst Deactivation

[0036] At the end of the ADN addition in the preceding examples, 2.5 g of ADN was added in a single batch to an autoclave containing the catalyst used and the crude HMD (non-evacuated reaction mixture) produced in Example 2, and hydrogenated (80°C, 25 bar). Under those operating conditions, the catalytic activity was 44.6 × 10⁻⁶. -5 mol H2 / g 催化剂 / s, which represents a 60% loss of activity (compared to 111 × 10⁻⁶). -5 (mol H2 / g catalyst / s compared to).

[0037] Example 4: Modification of co-catalysts for catalytic activity measurement

[0038] The procedure was carried out according to Example 1, except that 20 mol% of a fresh co-catalyst (XOH) aqueous solution and 80 mol% of potassium hydroxide (KOH) aqueous solution were added to the reactor instead of 100% KOH. The total amount of OH- was maintained at 0.8 mol / kg Ni.

[0039] The catalytic activity is recorded in Table 1 below.

[0040] Table 1

[0041]

[0042] Example 5: Modification of a co-catalyst for selective measurement

[0043] The procedure was carried out according to Example 2, except that 20 mol% of a fresh co-catalyst (XOH) aqueous solution and 80 mol% of potassium hydroxide (KOH) aqueous solution were added to the reactor instead of 100% KOH. The total amount of OH- was maintained at 0.8 mol / kg Ni.

[0044] The weight percentage of 1,2-diaminocyclohexane (DCH) in crude hexamethylenediamine is recorded in Table 2 below.

[0045] Table 2

[0046] KOH (100%, reference experiment) 100 / 0 0.1812 x CsOH 80 / 20 0.1800 -0.6％ <![CDATA[N(CH3)4OH]]> 80 / 20 0.1380 -24％ <![CDATA[Ba(OH)2]]> 80 / 20 0.1723 -4.9％ <![CDATA[NH4OH]]> 80 / 20 0.1910 +5.4％ <![CDATA[N(CH3CH2CH2CH2)4OH]]> 80 / 20 0.1159 -36％ <![CDATA[N(CH3)3BzOH]]> 80 / 20 0.2196 +21％

[0047] Example 6: Modification of the molar percentage of XOH used for catalytic activity measurement

[0048] The procedure was carried out according to Example 1, except that 50 mol% of a fresh co-catalyst (XOH) aqueous solution and 50 mol% of potassium hydroxide (KOH) aqueous solution were added to the reactor instead of 100% KOH. The total amount of OH- was maintained at 0.8 mol / kg Ni.

[0049] The catalytic activity is recorded in Table 3 below.

[0050] Table 3

[0051]

[0052] Example 7: Modification of the molar percentage of XOH for selective measurement

[0053] The procedure was carried out according to Example 1, except that 50 mol% of a fresh co-catalyst (XOH) aqueous solution and 50 mol% of potassium hydroxide (KOH) aqueous solution were added to the reactor instead of 100% KOH. The total amount of OH- was maintained at 0.8 mol / kg Ni.

[0054] The weight percentage of 1,2-diaminocyclohexane in crude hexamethylenediamine is recorded in Table 4 below.

[0055] Table 4

[0056]

[0057] Example 8: Deactivation of catalyst.

[0058] All experiments were conducted according to the method described in Example 3. The catalytic activity of the Raney nickel catalyst used is recorded in Table 5 below and compared with the initial activity (111 × 10⁻⁶). -5 mol H2 / g 催化剂 / s) comparison.

[0059] Table 5

[0060]

[0061] Using the new cocatalysts N(CH3)4OH and N(CH3CH2CH2CH2)4OH, the catalyst is less deactivated.

Claims

1. A method for preparing hexamethylenediamine by hydrogenation of adiponitrile in the presence of a Raney nickel catalyst and a basic co-catalyst containing potassium hydroxide. The alkaline co-catalyst mentioned above includes barium hydroxide as another alkaline compound. or The alkaline cocatalyst comprises ammonium hydroxide of the general formula NR4OH as other alkaline compounds, wherein each R is independently an alkyl group having 1 to 4 carbon atoms. The alkaline co-catalyst comprises 50 to 95 mol% KOH and 5 to 50 mol% other alkaline compounds.

2. The method according to claim 1, wherein each R is independently methyl or butyl.

3. The method according to claim 2, wherein R is methyl.

4. The method according to claim 2, wherein R is n-butyl.

5. The method according to any one of claims 1 to 4, wherein the alkaline co-catalyst comprises 70 to 90 mol% KOH and 10 to 30 mol% other alkaline compounds.

6. The method according to claim 5, wherein the alkaline co-catalyst comprises 75 to 85 mol% KOH and 15 to 25 mol% other alkaline compounds.

7. The method according to any one of claims 1 to 4, wherein the alkaline co-catalyst is present at 0.1 to 2.0 mol OH - The amount of Ni present is per kg.

8. The method according to any one of claims 1 to 4, wherein the hydrogenation is carried out in hexamethylenediamine containing 1 to 20% by weight of an aqueous solution of an alkaline co-catalyst as a solvent.

9. The method according to any one of claims 1 to 4, wherein the hydrogenation is carried out at a temperature of 50 to 150°C and a hydrogen pressure of 1 to 100 bar.

10. The method according to any one of claims 1 to 4, wherein the Raney nickel catalyst comprises one or more dopants selected from chromium, titanium, molybdenum, tungsten, manganese, vanadium, zirconium, iron, and zinc.

11. A method for preparing hexamethylenediamine by hydrogenation of adiponitrile in the presence of a Raney nickel catalyst and a basic co-catalyst containing potassium hydroxide. The alkaline co-catalyst mentioned above includes cesium hydroxide as another alkaline compound. The alkaline co-catalyst comprises 70 to 90 mol% KOH and 10 to 30 mol% cesium hydroxide.

12. The method according to claim 11, wherein the alkaline co-catalyst comprises 75 to 85 mol% KOH and 15 to 25 mol% other alkaline compounds.

13. The method according to claim 11, wherein the alkaline co-catalyst is present at 0.1 to 2.0 mol OH - The amount of Ni present is per kg.

14. The method of claim 11, wherein the hydrogenation is carried out in hexamethylenediamine comprising 1 to 20% by weight of an aqueous solution of a basic co-catalyst as a solvent.

15. The method of claim 11, wherein the hydrogenation is carried out at a temperature of 50 to 150°C and a hydrogen pressure of 1 to 100 bar.

16. The method of claim 11, wherein the Raney nickel catalyst comprises one or more dopants selected from chromium, titanium, molybdenum, tungsten, manganese, vanadium, zirconium, iron, and zinc.

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