Process for the preparation of hexamethylenediamine by hydrogenation of adiponitrile and reduction of the formation of diaminocyclohexane

Abstract

This invention relates to a method for preparing hexamethylenediamine by hydrogenation of adiponitrile in the presence of a Raney nickel catalyst, wherein a Raney nickel catalyst modified by treatment with carbon monoxide or carbon dioxide in a liquid medium is used.

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. 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 hydrogenating nitriles under pressure and at not very high temperatures, such as 25 bar and 80 °C, in the presence of basic compounds and Raney nickel-based catalysts.

[0006] In the latter type of method, the hydrogenation of nitrile compounds to amines is carried out in the presence of a catalyst based on optionally doped Raney nickel. These catalysts are prepared by leaching aluminum from Ni-Al alloys 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.

[0007] 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.

[0008] 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.

[0009] US 3,235,600 relates to a method for the catalytic hydrogenation of adiponitrile to hexamethylenediamine, wherein the formation of the byproduct 1,2-diaminocyclohexane (DCH) is suppressed. In summary, the document describes a method in which a mixture of adiponitrile, ammonia, hydrogen, and a DCH-inhibiting compound selected from organic and inorganic carbonates, organic and inorganic carbamates, and carbon dioxide passes over or through a hydrogenation catalyst under high temperature and high pressure conditions. As hydrogenation catalysts, free metal forms or compound forms, such as oxides or salts, of nickel, cobalt, copper, zinc, platinum, palladium, rubidium, and ruthenium are mentioned. For the hydrogenation of adiponitrile to hexamethylenediamine, a cobalt catalyst, particularly a catalyst containing cobalt oxide, is preferred. In examples, when using a sintered pellet cobalt catalyst, hexamethylenediamine carbonate and aminohexanocyanate carbamate are used as DCH inhibitors. Pretreatment of the catalyst before hydrogenation is not disclosed.

[0010] One object of the present invention is to provide a method for preparing hexamethylenediamine by hydrogenation of adiponitrile in the presence of Raney nickel catalyst, characterized in that a small amount of diaminocyclohexane (DCH) is formed as a byproduct. Summary of the Invention

[0011] The objective is achieved by a method for preparing hexamethylenediamine by hydrogenating adiponitrile in the presence of a Raney nickel catalyst, wherein a Raney nickel catalyst modified by treatment with carbon monoxide or carbon dioxide in a liquid medium is used. Detailed Implementation

[0012] In one embodiment of the invention, the Raney nickel catalyst has been modified prior to hydrogenation by pretreatment with pure carbon monoxide, carbon monoxide in an inert gas or hydrogen, preferably carbon monoxide in hydrogen.

[0013] Typically, carbon monoxide is used in hydrogen at a concentration of 50 to 1000 ppm, preferably 100 to 500 ppm, and especially 150 to 350 ppm.

[0014] In another embodiment, the Raney nickel catalyst has been modified by pretreatment with carbon dioxide in an inert gas prior to hydrogenation.

[0015] Typically, carbon dioxide is used at a concentration of 1 to 100 vol%, preferably 1 to 25 vol%, in an inert gas atmosphere. Pure carbon dioxide may also be used.

[0016] Suitable inert gases include, for example, nitrogen and argon. In one particular embodiment, argon is used as the inert gas.

[0017] In the pretreatment step, the liquid medium is preferably water.

[0018] In the pretreatment step, powdered Raney nickel catalyst is contacted in a liquid medium with a pretreatment gas containing carbon monoxide in hydrogen or carbon dioxide in an inert gas. This contact can be carried out by stirring the powdered Raney nickel catalyst in an autoclave.

[0019] Typically, pretreatment is carried out at a total pressure of 1 to 50 bar, preferably 2 to 50 bar, more preferably 5 to 30 bar, and usually at a temperature of 0 to 40°C, preferably 10 to 30°C. For example, pretreatment can be carried out over a period of 5 to 120 minutes, preferably 15 to 60 minutes.

[0020] In another embodiment, the Raney catalyst is modified during hydrogenation by adding carbon monoxide or carbon dioxide to the hydrogenating gas. In this embodiment, no separate pretreatment step is required. In some embodiments, carbon monoxide is typically added to the hydrogenating gas at a concentration of 50 to 1000 ppm, preferably 100 to 500 ppm, and particularly 150 to 350 ppm.

[0021] 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 major 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.

[0022] The hydrogenation reaction is preferably carried out in the presence of water, which is another component of the reaction medium. The amount of water in the liquid phase of the total reaction medium is generally less than or equal to 50% by weight, advantageously less than or equal to 20% by weight, and more preferably still 0.1% to 15% by weight. Organic solvents may also be used as other components of the reaction medium.

[0023] The hydrogenation reaction is carried out in the presence of a basic compound, preferably an inorganic base, such as LiOH, NaOH, KOH, RbOH, CsOH, and mixtures thereof. NaOH and KOH are preferred.

[0024] The amount of base added is determined to have at least 0.1 mol base per kg of catalyst, preferably 0.1 to 2 mol base per kg of catalyst, and more advantageously still 0.3 to 1.5 mol base per kg of catalyst.

[0025] The hydrogenation reaction is typically carried out at a temperature of less than or equal to 150°C, for example, 50 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 50°C to 100°C.

[0026] 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).

[0027] 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 dopant 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.

[0028] 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.

[0029] The optionally doped Raney nickel catalyst is typically derived from a molten Ni-Al precursor alloy (Ni content, for example, 28% to 59% by weight), with metallic dopant elements, preferably iron, chromium, and zinc, added according to a doping method known as a "metallurgical" doping process. 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.

[0030] Dopant can also be introduced via "chemical" doping: by impregnating the Raney nickel catalyst with a solution containing a precursor of 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.

[0031] 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.

[0032] Example

[0033] Impurities were determined using gas chromatography with an internal standard.

[0034] The catalytic activity and selectivity of the modified and unmodified catalysts were measured using two common methods. Catalytic activity was determined in a batch reactor, while selectivity was measured in a semi-continuous reactor.

[0035] Two modifiers were used: carbon monoxide (CO) and carbon dioxide (CO2). For both cases, the Raney nickel catalyst was pretreated in a liquid medium consisting of water or other organic solvents using a common method. It was then hydrogenated with pure hydrogen.

[0036] For CO, ADN hydrogenation is also carried out using an unmodified catalyst under a total H2 pressure containing 250 ppm CO.

[0037] Example 1: A General Method for Measuring Catalytic Activity

[0038] In a dry N2 atmosphere, 0.19 g of Raney nickel catalyst was stirred with 2.8 g of water, 24.6 g of pure hexamethylenediamine, and 20 μL of a 7 mol / L aqueous solution of potassium hydroxide, corresponding to 0.8 mol OH- / kg Ni. The temperature was increased to 80 °C and a total hydrogen pressure of 25 bar. 2.5 g of adiponitrile was then added in a single step to an autoclave for hydrogenation. Under those operating conditions, the catalytic activity was 90 × 10⁻⁶. -5 mol H2 / g 催化剂 / s.

[0039] Example 2: A general method for selective measurement:

[0040] In a dry N2 atmosphere, 1.1 g of unmodified Raney nickel catalyst was stirred with 1.7 g of water, 15.2 g of pure hexamethylenediamine, and 129 μL of a 7 mol / L aqueous solution of potassium hydroxide, corresponding to 0.8 mol OH- / kg Ni. The temperature was increased to 80 °C and a total hydrogen pressure of 25 bar. 10 g of adiponitrile (ADN) was added dropwise to an autoclave and hydrogenated. After 3 hours, the crude hexamethylenediamine produced was analyzed by gas chromatography. Under those operating conditions, 0.1939% 1,2-diaminocyclohexane (DCH) was produced.

[0041] Example 3: A general method for measuring catalyst deactivation:

[0042] At the end of the ADN addition in the preceding examples, 2.5 g of ADN was added at once to a high-pressure reactor containing the catalyst used and the crude HMD produced in Example 2 (without evacuating the reaction mixture) and hydrogenated (25 bar, 80 °C). Under those operating conditions, the catalytic activity was 37.4 × 10⁻⁶. -5 mol H2 / g 催化剂 / s, which represents a 58% loss of activity (compared to a reference of 90 × 10⁻⁶). -5 mol H2 / g 催化剂 / s compared to)

[0043] Example 4: A General Method for Catalyst Modification Pretreatment

[0044] According to Examples 1 and 2 method The procedure differs in that, prior to hydrogenation, 2g of Raney nickel catalyst and 80g of water are stirred for 30 minutes at room temperature with H2 containing 250ppm CO or argon containing 10% by volume CO2 at 20 bar. The modified catalyst is then decanted and used for the hydrogenation of adiponitrile with pure hydrogen.

[0045] The catalytic activity and the weight percentage of 1,2-diaminocyclohexane (DCH) in crude hexamethylenediamine are recorded in Table 1 below.

[0046] Table 1

[0047]

[0048] Catalyst modification with CO2 allows for the reduction of DCH and all impurities from the HMD method. In fact, the total amount of impurities was reduced from 0.2540% (reference experiment) to 0.1710%.

[0049] Example 5: Hydrogenation of adiponitrile with H2 containing 250 ppm CO

[0050] According to Examples 1 and 2 method The process is different in that the pure hydrogen used for adiponitrile hydrogenation is replaced by H2 containing 250 ppm CO.

[0051] Method for measuring catalytic activity in H2 containing 250 ppm CO

[0052] In a dry N2 atmosphere, 0.48 g of Raney nickel catalyst was stirred with 7.3 g of water, 65.6 g of pure hexamethylenediamine, and 55 μL of a 7 mol / L aqueous solution of potassium hydroxide, corresponding to 0.8 mol OH- / kg Ni. The temperature was increased at 80 °C and a total H2 pressure of 25 bar containing 250 ppm CO. Then, 7.2 g of adiponitrile (ADN) was added in a single step to an autoclave and hydrogenation was carried out. Under those operating conditions, the catalytic activity was 96 × 10⁻⁶. -5 mol H2 / g 催化剂 / s.

[0053] Method for measuring selectivity in H2 containing 250 ppm CO

[0054] 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 a 7 mol / L aqueous solution of potassium hydroxide, corresponding to 0.8 mol OH- / kg Ni. The temperature was increased at 80 °C and a total hydrogen pressure of 25 bar containing 250 ppm CO. 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, 0.1633% 1,2-diaminocyclohexane (DCH) was produced.

[0055] The catalytic activity and the weight percentage of 1,2-diaminocyclohexane in crude hexamethylenediamine are recorded in Table 2 below.

[0056] Table 2

[0057]

[0058] Example 6: Catalyst Deactivation

[0059] 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 3 below.

[0060] Table 3

[0061]

[0062] No significant effect was observed on catalyst deactivation.

Claims

1. A method for preparing hexamethylenediamine by hydrogenation of adiponitrile in the presence of a Raney nickel catalyst, wherein a Raney nickel catalyst modified by treatment with carbon monoxide in a liquid medium is used, or A Raney nickel catalyst that has been modified by treatment with carbon dioxide in a liquid medium prior to hydrogenation was used.

2. The method according to claim 1, wherein the Raney nickel catalyst has been modified by pretreatment with carbon monoxide in hydrogen prior to hydrogenation.

3. The method of claim 2, wherein carbon monoxide is used in hydrogen at a concentration of 50 to 1000 ppm.

4. The method of claim 1, wherein the Raney nickel catalyst has been modified by pretreatment with carbon dioxide in an inert gas prior to hydrogenation.

5. The method of claim 4, wherein carbon dioxide is used at a concentration of 1 to 25% by volume in an inert gas.

6. The method according to claim 5, wherein the inert gas is argon.

7. The method according to any one of claims 2 to 6, wherein the pretreatment is carried out in water.

8. The method according to any one of claims 2 to 6, wherein the pretreatment is performed at a total pressure of 2 to 50 bar and a temperature of 0 to 40°C.

9. The method of claim 1, wherein the Raney nickel catalyst is modified during hydrogenation by adding carbon monoxide to the hydrogenation gas.

10. The method of claim 9, wherein carbon monoxide is added to the hydrogenation gas at a concentration of 50 to 1000 ppm.

11. The method according to any one of claims 1 to 6, wherein the hydrogenation is carried out in a reaction medium containing hexamethylenediamine as a solvent, the concentration of hexamethylenediamine being 50 to 90% by weight, based on the weight of the liquid phase of the reaction medium.

12. The method according to any one of claims 1 to 6, wherein the hydrogenation is carried out at a temperature of 50 to 150°C and a hydrogen pressure of 1 to 100 bar.

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