Process for the preparation of hexamethylene diamine

Abstract

PROCESS FOR THE PREPARATION OF HEXAMETYLENEDIAMINE. The present invention relates to a process for the preparation of hexamethylenediamine by hydrogenation of adiponitrile in the presence of a Raney nickel catalyst, in which a Raney nickel catalyst modified by treatment with carbon monoxide or carbon dioxide in liquid medium is used.

Description

"PROCESS FOR THE PREPARATION OF HEXAMETHYLENEDIAMINE" Field of the Invention

[001] The present invention relates to a process for the preparation of hexamethylenediamine by hydrogenation of adiponitrile in the presence of a Raney nickel catalyst. Background of the Invention

[002] Hexamethylenediamine is a compound used in numerous applications, the main ones being the manufacture of polyamides such as poly(hexamethylene adipamide), better known as PA 6,6, and the manufacture of hexamethylene diisocyanate.

[003] Several hexamethylenediamine manufacturing processes have been proposed, which generally consist of a hydrogenation of adiponitrile (tetramethylene dicyanide) in the presence of a hydrogenation catalyst. Two types of processes are used industrially that employ different catalysts and different temperature and pressure conditions.

[004] Thus, a first type of hydrogenation process that is used and described in the literature consists of hydrogenating nitrile compounds in the presence of ammonia and under high pressure, with a ruthenium-based catalyst, for example. Iron-based catalysts under high pressure and temperature are also used.

[005] A second type of process consists of carrying out the hydrogenation of nitrile compounds under pressure and at a not very high temperature, for example at 2.5 x 106 Pa (25 bar) and 80 °C, in the presence of a basic compound and a Raney nickel-based catalyst.

[006] In this last type of process, the hydrogenation of nitrile compounds to amines occurs in the presence of an optionally doped Raney nickel-based catalyst. These catalysts are prepared by leaching aluminum from Ni-Al alloys in a strongly alkaline medium. The catalysts Petition 870250064589, dated 07 / 25 / 2025, page 15 / 35 2 / 10 obtained are composed of nickel crystallite clusters, with high specific surface area and variable residual aluminum content.

[007] Adiponitrile is known to react by hydrogenation to give a cyclic diamine, diaminocyclohexane (DCH). However, DCH is particularly problematic as it has a boiling point close to the boiling point of the target amine and is therefore very difficult to separate.

[008] There is an industrial need to optimize the hydrogenation of adiponitrile to hexamethylenediamine using Raney nickel catalysts, primarily with regard to the activity, selectivity, and deactivation behavior of the final catalyst. In particular, it is important to limit the formation of diaminocyclohexane to obtain a hexamethylenediamine that can be purified with minimal capital cost and minimal energy consumption.

[009] US patent 3,235,600 refers to a process for the catalytic hydrogenation of adiponitrile to hexamethylenediamine, in which the production of the byproduct 1,2-diaminocyclohexane (DCH) is suppressed. The document generally describes a process in which a mixture of adiponitrile, ammonia, hydrogen, and a DCH suppressor compound selected from organic and inorganic carbonates, organic and inorganic carbamates, and carbon dioxide is passed into or through a hydrogenation catalyst under elevated temperature and pressure conditions. Nickel, cobalt, copper, zinc, platinum, palladium, rubidium, and ruthenium are mentioned as hydrogenation catalysts, either in the form of free metals or in the form of compounds such as oxides or salts. For the hydrogenation of adiponitrile to hexamethylenediamine, cobalt catalysts are preferred, and in particular catalysts comprising cobalt oxide.In the examples, hexamethylenediamine carbonate and aminocapronitrile carbamate are used as DCH suppressors with a sintered pelletized cobalt catalyst. No. Petition 870250064589, dated 07 / 25 / 2025, page 16 / 35 On October 3rd, a pre-treatment of the catalyst prior to hydrogenation is disclosed.

[0010] It is an object of the present invention to provide a process for the preparation of hexamethylenediamine by hydrogenation of adiponitrile in the presence of a Raney nickel catalyst that is characterized by a low formation of diaminocyclohexane (DCH) as a by-product. Brief Description of the Invention

[0011] The objective is achieved by a process for the preparation of hexamethylenediamine by hydrogenation of adiponitrile in the presence of a Raney nickel catalyst, in which a Raney nickel catalyst modified by treatment with carbon monoxide or carbon dioxide in liquid medium is used. Detailed Description of the Invention

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

[0013] In general, carbon monoxide is applied at a concentration of 50 to 1,000 ppm, preferably 100 to 500 ppm, in particular 150 to 350 ppm in hydrogen.

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

[0015] In general, carbon dioxide is applied at a concentration of 1 to 100% by volume, preferably 1 to 25% by volume in an inert gas. Pure carbon dioxide can also be used.

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

[0017] In the pretreatment stage, the liquid medium is Petition 870250064589, dated 07 / 25 / 2025, page 17 / 35 4 / 10 preferably water.

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

[0019] In general, pretreatment is carried out at a total pressure of 1.0 x 10⁵ to 5.0 x 10⁶ Pa (1 to 50 bar), preferably 2.0 x 10⁵ to 5.0 x 10⁶ Pa (2 to 50 bar), more preferably 5.0 x 10⁵ to 3.0 x 10⁶ Pa (5 to 30 bar), and generally at a temperature of 0 to 40 °C, preferably 10 to 30 °C. For example, pretreatment can be carried out for a time of 5 to 120 min, preferably 15 to 60 min.

[0020] In another embodiment, the Raney catalyst is modified during hydrogenation by the addition of carbon monoxide or carbon dioxide to the hydrogenation gas. In this embodiment, no separate pretreatment step is required. In certain embodiments, carbon monoxide is generally added at a concentration of 50 to 1,000 ppm, preferably 100 ppm to 500 ppm, in particular 150 to 350 ppm to the hydrogenation gas.

[0021] The hydrogenation reaction is generally carried out in the presence of a solvent advantageously composed of the amine obtained by hydrogenation. Thus, in the case of the hydrogenation of adiponitrile, hexamethylenediamine is advantageously used as the main component of the reaction medium. The amine concentration in the reaction medium is advantageously between 50% and 99% by weight, preferably between 60% and 99% by weight, of the liquid phase of the hydrogenation reaction medium.

[0022] The hydrogenation reaction is preferably carried out in the presence of water as another component of the reaction medium. This water is Petition 870250064589, dated 07 / 25 / 2025, page 18 / 35 5 / 10 generally present in an amount less than or equal to 50% by weight, advantageously less than or equal to 20% by weight, in the liquid phase of the total reaction medium and even more preferably between 0.1% and 15% by weight. Organic solvents may also be used as another component 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 preferably used.

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

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

[0026] The hydrogen pressure in the reactor is generally 1 to 100 bar (0.10 and 10 MPa), preferably 10 to 50 bar (1 to 5 MPa).

[0027] The Raney nickel catalyst used according to the invention may advantageously comprise one or more other elements, often referred to as dopants, such as, for example, chromium, titanium, molybdenum, tungsten, manganese, vanadium, zirconium, iron, zinc and more generally the elements of groups IIB, IVB, IIIB, VB, VIB, VIIB and VIII of the Periodic Table of Elements. Among these dopant elements, chromium, iron and / or zinc or a mixture of these elements are considered the most advantageous and are generally present in a weight concentration (expressed relative to Raney nickel metal) of less than 10%, preferably less than Petition 870250064589, dated 07 / 25 / 2025, p. 19 / 35 6 / 10 5%. For example, the iron concentration can be 1 to 2% by weight, the chromium concentration can be 0.5 to 5% by weight, and the zinc concentration can be 0.5 to 5% by weight.

[0028] Raney catalysts often comprise trace metals present in the alloy used to prepare said catalysts. Thus, aluminum is especially present in these catalysts. The concentration of aluminum can be from 2 to 10% by weight.

[0029] Optionally doped Raney Ni catalyst generally originates from a molten Ni-Al precursor alloy (Ni content, for example, 28 to 59% by weight), to which metallic doping elements, preferably iron, chromium and zinc, are added according to a doping procedure known as the “metallurgical” doping procedure. After cooling and milling, the doped precursor alloy is conventionally subjected to an alkaline attack that results in a greater or lesser removal of aluminum and, optionally, of a fraction of the doping element. The starting alloys used are advantageously chosen from the following forms of binary nickel / aluminum combinations: NiAl3, Ni2Al3 and proeutectic Al / NiAl3.

[0030] It is also possible to introduce dopants by means of “chemical” doping by impregnating the Raney Ni catalyst with a solution containing a precursor of the dopant element, precipitating the dopant element on the Raney Ni catalyst, or introducing the dopant precursor compound during the alkaline attack of the Raney alloy.

[0031] The present invention is further illustrated by the following examples. It should be understood that the following examples are for illustrative purposes only and are not used to limit the present invention to them. Examples

[0032] The amount of impurities was determined by gas chromatography using an internal standard. Petition 870250064589, dated 07 / 25 / 2025, page 20 / 35 7 / 10

[0033] Two general procedures were used to measure catalytic activity and selectivity respectively with a modified and unmodified catalyst. Catalytic activity was determined in a batch reactor while selectivity was measured in a semi-continuous reactor.

[0034] Two modifying agents were used: carbon monoxide (CO) and carbon dioxide (CO2). For both, a general procedure was used to pretreat the Raney nickel catalyst in a liquid medium consisting of water or another organic solvent. Hydrogenation was then carried out with pure hydrogen.

[0035] For CO, DNA hydrogenation was also carried out in 250 ppm CO at full H2 pressure, with an unmodified catalyst. Example 1: General Procedure for Measuring Catalytic Activity

[0036] In a dry N2 atmosphere, 0.19 g of Raney nickel catalyst were stirred with 2.8 g of water and 24.6 g of pure hexamethylenediamine and 20 µl of a 7 mol / l aqueous potassium hydroxide solution, corresponding to 0.8 mol OH⁻ / kg of Ni. The temperature was raised to 80 °C and 2.5 x 10⁶ Pa (25 bar) total hydrogen pressure. 2.5 g of adiponitrile were added at once to the autoclave and hydrogenated. Under these operating conditions, the catalytic activity is 90 x 10⁻⁵ mol H₂ / g catalyst / s. Example 2: General procedure for measuring selectivity

[0037] In a dry N2 atmosphere, 1.1 g of unmodified Raney nickel catalyst were stirred with 1.7 g of water and 15.2 g of pure hexamethylenediamine and 129 µl of a 7 mol / l aqueous potassium hydroxide solution, corresponding to 0.8 mol OH⁻¹ kg of Ni. The temperature was raised to 80 °C and 2.5 x 10⁶ Pa (25 bar) total hydrogen pressure. 10 g of adiponitrile (ADN) were added dropwise in the autoclave and hydrogenated. After 3 hours, the crude hexamethylenediamine produced was analyzed by gas chromatography. 0.1939% 1,2-diaminocyclohexane (DCH) Petition 870250064589, dated 07 / 25 / 2025, page 21 / 35 8 / 10 were produced under these operating conditions. Example 3: General procedure for measuring catalyst deactivation.

[0038] At the end of the DNA addition in the previous example, 2.5 g of DNA were added at once to the autoclave containing the catalyst used and the crude HMD produced in example 2 (without emptying the reaction mixture) and were hydrogenated (2.5 x 106 Pa (25 bar), 80 °C). Under these operating conditions, the catalytic activity is 37.4 x 10-5 mol H2 / gcatalyst / s which represents 58% of the activity loss (compared to the reference 90 x 10-5 mol H2 / gcatalyst / s). Example 4: General procedure for catalyst modification pre-treatment

[0039] The procedure of examples 1 and 2 was followed, except that before hydrogenation, 2 g of Raney nickel catalyst were stirred with 80 g of water at room temperature with 2.0 x 106 Pa (20 bar) of 250 ppm CO in H2 or 10% by vol. of CO2 in argon for 30 minutes. The modified catalyst was then decanted and used for the hydrogenation of adiponitrile with pure hydrogen.

[0040] The catalytic activity and weight percentage of 1,2-diaminocyclohexane (DCH) in the crude hexamethylenediamine are reported in Table 1 below. Table 1 Catalyst Activity (10-5 mol H2 / g / s) % [DCH] % reduction Unmodified (reference) 90 0.1939 x Modified with CO / H2 77 0.1922 -2.6% Modified with CO2 / Ar 61 0.1208 -38%

[0041] Modifying the catalyst with CO2 allows for a reduction in DCH and all impurities from the HMD process. In fact, the total amount of impurities decreases from 0.2540% (reference experiment) to 0.1710%. Example 5: Hydrogenation of adiponitrile with 250 ppm of CO₂ in H₂

[0042] The procedure of examples 1 and 2 was followed, except that the pure hydrogen used for the hydrogenation of adiponitrile was replaced by Petition 870250064589, dated 07 / 25 / 2025, page 22 / 35 9 / 10 250 ppm of CO in H2. Procedure for measuring catalytic activity below 250 ppm of CO₂ in H₂

[0043] In a dry N2 atmosphere, 0.48 g of Raney nickel catalyst were stirred with 7.3 g of water and 65.6 g of pure hexamethylenediamine and 55 μL of a 7 mol / L aqueous potassium hydroxide solution, corresponding to 0.8 mol OH- / kg of Ni. The temperature was raised to 80 °C and 2.5 x 106 Pa (25 bar) of 250 ppm CO at full hydrogen pressure. 7.2 g of adiponitrile (ADN) were added at once to the autoclave and hydrogenated. Under these operating conditions, the catalytic activity is 96 x 10-5 mol H2 / g catalyst / s. Procedure for measuring selectivity below 250 ppm CO in H2

[0044] In a dry N2 atmosphere, 3 g of Raney nickel catalyst were stirred with 4.5 g of water and 40.5 g of pure hexamethylenediamine and 345 μl of a 7 mol / l aqueous potassium hydroxide solution, corresponding to 0.8 mol OH- / kg of Ni. The temperature was raised to 80 °C and 2.5 x 106 Pa (25 bar) of 250 ppm CO at full hydrogen pressure. 30 g of adiponitrile (ADN) were added dropwise at a mass flow rate of 10 g / h in the autoclave and hydrogenated. After 3 hours, the crude hexamethylenediamine produced was analyzed by gas chromatography. 0.1633% of 1,2-diaminocyclohexane (DCH) was produced under these operating conditions.

[0045] The catalytic activity and weight percentages of 1,2-diaminocyclohexane in crude hexamethylenediamine are reported in Table 2 below. TABLE 2 Catalyst Activity (10-5 mol H2 / g / s) % of [DCH] % reduction Pure H2 (reference) 111 0.1939 x 250 ppm CO in H2 96 0.1633 -10% Petition 870250064589, dated 07 / 25 / 2025, page 23 / 35 10 / 10 Example 6: Catalyst deactivation

[0046] The procedure of example 3 was followed for each experiment. The catalytic activities of the Raney nickel catalysts used are reported in Table 3 below. Table 3 Co-catalyst Activity (10-5 mol H2 / g / s) Activity Loss (%) Unmodified (reference) 37.4 - 58% Modified with CO2 / Ar 27.9 - 54%

[0047] No pronounced effect on catalyst deactivation was observed.

Claims

1. PROCESS FOR THE PREPARATION OF HEXAMETHYLENEDIAMINE, characterized by being carried out by hydrogenation of adiponitrile in the presence of a Raney nickel catalyst, in which a Raney nickel catalyst modified by treatment with carbon monoxide or carbon dioxide in liquid medium is used.

2. PROCESS, according to claim 1, characterized in that the Raney nickel catalyst has been modified by pretreatment with carbon monoxide to hydrogen prior to hydrogenation.

3. PROCESS, according to claim 2, characterized in that carbon monoxide is applied at a concentration of 50 to 1,000 ppm in hydrogen.

4. PROCESS, according to claim 1, characterized in that the Raney nickel catalyst has been modified by pretreatment with carbon dioxide in an inert gas prior to hydrogenation.

5. PROCESS, according to claim 4, characterized in that carbon dioxide is applied at a concentration of 1 to 25% by volume in an inert gas.

6. PROCESS, according to claim 5, characterized in that the inert gas is argon.

7. PROCESS, according to any one of claims 2 to 6, characterized in that the pretreatment is carried out in water.

8. PROCESS, according to any one of claims 2 to 7, characterized in that the pretreatment is carried out at a total pressure of 2.0 x 10⁵ to 5.0 x 10⁶ Pa (2 to 50 bar) at a temperature of 0 to 40 °C.

9. PROCESS, according to claim 1, characterized by the Raney nickel catalyst being modified during hydrogenation by the addition of carbon monoxide to the hydrogenation gas. Petition 870250064589, dated 07 / 25 / 2025, p. 25 / 35 2 / 2 10. PROCESS, according to claim 9, characterized in that carbon monoxide is added at a concentration of 50 to 1,000 ppm to the hydrogenation gas.

11. PROCESS, according to any one of claims 1 to 10, characterized in that hydrogenation is carried out at a temperature of 50 to 150 °C at a hydrogen pressure of 1.0 x 10⁵ to 1.0 x 10⁷ Pa (1 to 100 bar).