Method for preparing hexamethylenediamine by hydrogenating adiponitrile while suppressing the formation of diaminocyclohexane

Abstract

The present invention relates to a process for preparing hexamethylenediamine by hydrogenating adiponitrile in the presence of a Raney nickel catalyst, which process uses said Raney nickel catalyst modified by treatment with carbon monoxide or carbon dioxide in a liquid medium.

Description

[Technical Field]

[0001] The present invention relates to a process for preparing hexamethylenediamine by hydrogenating adiponitrile in the presence of a Raney nickel catalyst. [Background technology]

[0002] Hexamethylenediamine is a compound that has many uses, the primary uses of which include the production of polyamides, such as poly(hexamethylene adipamide), more commonly known as PA-6,6, and the production of hexamethylene diisocyanate.

[0003] Several processes for the production of hexamethylenediamine have been proposed, which generally consist of the hydrogenation of adiponitrile (tetramethylene dicyanide) in the presence of a hydrogenation catalyst. Two types of processes are commercially available, using different catalysts and different temperature and pressure conditions.

[0004] The first type of hydrogenation method used and described in the literature consists of hydrogenating nitrile compounds in the presence of ammonia under high pressure, for example using ruthenium-based catalysts. Iron-based catalysts have also been used under high pressure and temperature.

[0005] The second type of process consists in carrying out the hydrogenation of nitrile compounds under pressure and at moderate temperatures, for example at 25 bar and 80° C., in the presence of a basic compound and a Raney nickel-based catalyst.

[0006] In the latter type of process, the hydrogenation of nitrile compounds to amines is carried out 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 resulting catalysts consist of agglomerates of nickel crystallites with a high specific surface area and variable residual aluminum content.

[0007] It is known that adiponitrile can be reacted by hydrogenation to give the cyclic diamine, diaminocyclohexane (DCH). However, DCH is particularly troublesome because it has a boiling point close to that of the amine of interest, making it very difficult to separate.

[0008] There is an industrial need to optimize the hydrogenation of adiponitrile to hexamethylenediamine using Raney nickel catalysts, particularly in terms of the activity, selectivity, and deactivation behavior of the final catalyst. In particular, it is important to limit the formation of diaminecyclohexanes in order to obtain hexamethylenediamine that can be purified with minimal capital costs and minimal energy consumption.

[0009] U.S. Patent Publication No. 3,235,600 relates to a process for catalytic hydrogenation of adiponitrile to hexamethylenediamine, suppressing the formation of the by-product 1,2-diaminocyclohexane (DCH). This document generally describes passing adiponitrile, ammonia, hydrogen, and a DCH inhibitor compound selected from organic and inorganic carbonates, organic and inorganic carbamates, and carbon dioxide through or over a hydrogenation catalyst under high-temperature and high-pressure conditions. Hydrogenation catalysts mentioned include nickel, cobalt, copper, zinc, platinum, palladium, rubidium, and ruthenium, either in the form of the free metal or in the form of compounds such as oxides and salts. For the hydrogenation of adiponitrile to produce hexamethylenediamine, cobalt catalysts, particularly catalysts containing cobalt oxide, are preferred. In the examples, hexamethylenediamine carbonate and aminocapronitrile carbamate are used as DCH inhibitors along with sintered pellet-form cobalt catalysts. The full treatment of the catalyst prior to hydrogenation is not disclosed. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] U.S. Patent Publication No. 3,235,600 Summary of the Invention [Problem to be solved by the invention]

[0011] The object of the present invention is to provide a process for the preparation of hexamethylenediamine by hydrogenating adiponitrile in the presence of a Raney nickel catalyst, which is characterized by a reduced formation of diaminocyclohexane (DCH) as a by-product. [Means for solving the problem]

[0012] The object is achieved by a process for preparing hexamethylenediamine by hydrogenating adiponitrile in the presence of a Raney nickel catalyst, the process using a Raney nickel catalyst modified by treatment with carbon monoxide or carbon dioxide in a liquid medium. DETAILED DESCRIPTION OF THE INVENTION

[0013] In one embodiment of the present invention, the Raney nickel catalyst is modified prior to hydrogenation by pretreatment with carbon monoxide in pure form in an inert gas or in hydrogen, preferably in hydrogen.

[0014] Generally, carbon monoxide is applied in a concentration of 50 to 1000 ppm, preferably 100 to 500 ppm, in particular 150 to 350 ppm in hydrogen.

[0015] In a further embodiment, the Raney nickel catalyst is modified by pre-treatment with carbon dioxide in an inert gas prior to hydrogenation.

[0016] Generally, carbon dioxide is applied in an inert gas at a concentration of 1 to 100% by volume, preferably 1 to 25% by volume. Pure carbon dioxide can also be used.

[0017] Suitable inert gases are, for example, nitrogen and argon, in one particular embodiment, argon is used as the inert gas.

[0018] In the pretreatment step, the liquid medium is preferably water.

[0019] In the pretreatment step, a finely divided Raney nickel catalyst is contacted in a liquid medium with a pretreatment gas comprising carbon monoxide in hydrogen or carbon dioxide in an inert gas, which may be carried out by stirring the finely divided Raney nickel catalyst in an autoclave.

[0020] Typically, the 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 at a temperature of typically 0 to 40° C., preferably 10 to 30° C. For example, the pretreatment may be carried out for a time period of 5 to 120 minutes, preferably 15 to 60 minutes.

[0021] In a further embodiment, the Raney catalyst is modified during hydrogenation by adding carbon monoxide or carbon dioxide to the hydrogenation gas. In this embodiment, no separate pretreatment step is required. In a particular embodiment, carbon monoxide is added to the hydrogenation gas at a concentration of generally 50 to 1000 ppm, preferably 100 to 500 ppm, and in particular 150 to 350 ppm.

[0022] The hydrogenation reaction is generally carried out in the presence of a solvent, preferably an amine obtained by hydrogenation. Thus, when 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, of the liquid phase of the hydrogenation reaction medium.

[0023] The hydrogenation reaction is preferably carried out in the presence of water as another component of the reaction medium. This water is generally present in an amount of not more than 50% by weight, advantageously not more than 20% by weight, and more preferably in an amount of 0.1% to 15% by weight of the liquid phase of the total reaction medium. Organic solvents can also be used as another component of the reaction medium.

[0024] 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.

[0025] The amount of base added is determined so as to have at least 0.1 mol of base per kg of catalyst, preferably 0.1 to 2 mol of base per kg of catalyst, and more advantageously 0.3 to 1.5 mol of base per kg of catalyst.

[0026] The hydrogenation reaction is generally carried out at a temperature of 150° C. or lower, for example, 50 to 150° C., preferably 120° C. or lower, and more preferably 100° C. or lower. The reaction temperature is most preferably 50 to 100° C.

[0027] The hydrogen pressure in the reactor is generally 1 to 100 bar (0.10 to 10 MPa), preferably 10 to 50 bar (1 to 5 MPa).

[0028] The Raney nickel catalyst used in accordance with the present invention may advantageously contain one or more other elements, commonly referred to as dopants, such as, for example, chromium, titanium, molybdenum, tungsten, manganese, vanadium, zirconium, iron, zinc, and more generally, elements of groups IIB, IVB, IIIB, VB, VIB, VIIB, and VIII of the periodic table. Among these dopant elements, chromium, iron, and / or zinc or mixtures of these elements are considered most advantageous and are usually present in concentrations (expressed relative to Raney nickel metal) of less than 10% by weight, preferably less than 5%. For example, the iron concentration may be 1-2% by weight, the chromium concentration may be 0.5-5% by weight, and the zinc concentration may be 0.5-5% by weight.

[0029] Raney catalysts often contain trace amounts of metals present in the alloys used to prepare the catalyst. Aluminum is therefore particularly present in these catalysts. The aluminum concentration may be between 2 and 10% by weight.

[0030] Optionally doped Raney nickel catalysts are generally derived from molten Ni-Al precursor alloys (e.g., containing 28-59% by weight of Ni) to which metallic dopant elements, preferably iron, chromium, and zinc, are added according to a doping process known as the "metallurgical" doping process. After cooling and grinding, the doped precursor alloy is subjected to alkaline attack in a conventional manner, which removes more or less of the aluminum and, optionally, a portion of the dopant elements. The starting alloys used are advantageously selected from the following forms of binary nickel / aluminum combinations: NiAl3, Ni2Al3, and primary Al / NiAl3.

[0031] It is also possible to introduce dopants via "chemical" doping, by depositing the dopant element on the Raney nickel catalyst by impregnating the Raney nickel catalyst with a solution containing a precursor of the dopant element, or by introducing a precursor compound of the dopant during alkaline attack of the Raney alloy.

[0032] The present invention is further illustrated by the following examples, which should be understood as being for illustrative purposes only and are not to be used to limit the present invention. [Example]

[0033] The amount of impurities was determined by gas chromatography using an internal standard.

[0034] Two general procedures were used to measure the catalytic activity and selectivity of the modified and unmodified catalysts, respectively: catalytic activity was determined in a batch reactor, and selectivity was measured in a semi-continuous reactor.

[0035] Two types of modifying reagents were used: carbon monoxide (CO) and carbon dioxide (CO). In both cases, a nickel Raney catalyst was pretreated in a liquid medium consisting of water or other organic solvents using a common procedure. Then, hydrogenation was carried out with pure hydrogen.

[0036] For CO, ADN hydrogenation was also carried out over the unmodified catalyst in 250 ppm CO under total H2 pressure.

[0037] Example 1: General procedure for measuring catalytic activity In a dry N2 atmosphere, 0.19 g of nickel Raney catalyst was stirred with 2.8 g of water, 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 a total hydrogen pressure of 25 bar was applied. In an autoclave, 2.5 g of adiponitrile was added in one portion and hydrogenated. Under these operating conditions, the catalytic activity was 90 × 10 -5 molH2 / g 触媒 / s.

[0038] Example 2: General procedure for selectivity measurements In a dry N2 atmosphere, 1.1 g of unmodified nickel Raney catalyst was stirred with 1.7 g of water, 15.2 g of pure hexamethylenediamine, and 129 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 a total hydrogen pressure of 25 bar was applied. In an autoclave, 10 g of adiponitrile (ADN) was added dropwise and hydrogenated. After 3 h, the crude hexamethylenediamine produced was analyzed by gas chromatography. Under these operating conditions, 0.1939% of 1,2-diaminocyclohexane (DCH) was produced.

[0039] Example 3: General procedure for catalyst deactivation measurements In the autoclave containing the catalyst used in Example 2 and the crude HMD produced after the addition of ADN from the previous example (without emptying the reaction mixture), 2.5 g of ADN was added in one portion and hydrogenated (25 bar, 80°C). Under these operating conditions, the catalytic activity was (90 x 10 -5 molH2 / g 触媒 / s), a 58% loss of activity of 37.4 × 10 -5 molH2 / g 触媒 / s.

[0040] Example 4: General procedure for catalyst modification pretreatment Following the procedures of Examples 1 and 2, except before hydrogenation, 2 g of nickel Raney catalyst was stirred at room temperature with 80 g of water and 250 ppm CO in H at 20 bar or 10% by volume CO in argon for 30 minutes. The modified catalyst was then decanted off and used in the hydrogenation of adiponitrile with pure hydrogen.

[0041] The catalyst activity and the weight percent of 1,2-diaminocyclohexane (DCH) in the crude hexamethylenediamine are reported in Table 1 below.

[0042] [Table 1]

[0043] Catalytic modification with CO2 can reduce all impurities from the DCH and HMD processes. In particular, the total amount of impurities was reduced from 0.2540% (control experiment) to 0.1710%.

[0044] Example 5: Hydrogenation of adiponitrile with 250 ppm CO in H The procedures of Examples 1 and 2 were followed, except that instead of using pure hydrogen for the hydrogenation of adiponitrile, 250 ppm CO in H2 was used.

[0045] Procedure for measuring catalytic activity under 250 ppm CO in H2 In a dry N2 atmosphere, 0.48 g of nickel Raney catalyst was stirred with 7.3 g of water, 65.6 g of pure hexamethylenediamine, and 55 μL of 7 mol / L aqueous potassium hydroxide solution, corresponding to 0.8 mol OH / kg of Ni. The temperature was increased to 80 °C under a total hydrogen pressure of 25 bar and 250 ppm CO. 7.2 g of adiponitrile (ADN) was added in one portion and hydrogenated in an autoclave. Under these operating conditions, the catalytic activity was 96 × 10 -5 molH2 / g 触媒 / s.

[0046] Procedure for measuring selectivity at 250 ppm CO in H2 In a dry N2 atmosphere, 3 g of nickel Raney catalyst was stirred with 4.5 g of water, 40.5 g of pure hexamethylenediamine, and 345 μL of 7 mol / L aqueous potassium hydroxide solution, corresponding to 0.8 mol OH / kg of Ni. The temperature was increased to 80 °C and the total hydrogen pressure was adjusted to 25 bar and 250 ppm CO. In an autoclave, 30 g of adiponitrile (ADN) was added dropwise at a mass flow rate of 10 g / h and hydrogenated. After 3 h, the crude hexamethylenediamine produced was analyzed by gas chromatography. Under these operating conditions, 0.1633% of 1,2-diaminocyclohexane (DCH) was produced.

[0047] The catalyst activity and the weight percent of 1,2-diaminocyclohexane in the crude hexamethylenediamine are reported in Table 2 below.

[0048] [Table 2]

[0049] Example 6: Catalyst deactivation In each experiment, the procedure of Example 3 was followed. The catalytic activities of the nickel Raney catalysts used are reported in Table 3 below.

[0050] [Table 3]

[0051] No significant effect on catalyst deactivation was observed.

Claims

1. 1. A process for preparing hexamethylenediamine by hydrogenating adiponitrile in the presence of a Raney® nickel catalyst, comprising: A process using the Raney nickel catalyst modified by treatment with carbon monoxide or carbon dioxide in a liquid medium.

2. The Raney nickel catalyst is 10. The process of claim 1, wherein the olefin is modified by pretreatment with carbon monoxide in hydrogen prior to hydrogenation.

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

4. The Raney nickel catalyst is 10. The process of claim 1, wherein the hydrogenation is preceded by a pretreatment with carbon dioxide in an inert gas.

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

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

7. The method according to any one of claims 2 to 6, wherein the liquid medium is water.

8. 8. The process according to any one of claims 2 to 7, wherein the pretreatment is carried out at a temperature of from 0 to 40°C and a total pressure of from 2 to 50 bar.

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

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

11. 11. The process according to any one of claims 1 to 10, wherein the hydrogenation is carried out at a temperature of from 50 to 150°C and a hydrogen pressure of from 1 to 100 bar.

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