A composite catalyst, a preparation method and application thereof, and a method for co-producing trimethylhydroxyethyl ethylenediamine and pentamethyldiethylenetriamine

Abstract

The present application relates to a kind of composite catalyst and its preparation method and application, the method for coproducing five methyl divinyl triamine of trimethyl hydroxyethyl ethylenediamine, belong to organic synthesis technical field.The composite catalyst provided by the present application is used to catalyze N-methyldiethanolamine and dimethylamine amination preparation trimethyl hydroxyethyl ethylenediamine and five methyl divinyl triamine, can significantly improve the selectivity of target product.As shown in the test results of example, with the composite catalyst provided by the present application catalyzing N-methyldiethanolamine and dimethylamine amination preparation trimethyl hydroxyethyl ethylenediamine and five methyl divinyl triamine, raw material N-methyldiethanolamine conversion rate is 93.7~99.2%, trimethyl hydroxyethyl ethylenediamine selectivity is 67.5~76.6%, five methyl divinyl triamine selectivity is 19.7~23.4%, and the total selectivity of target product can reach 89.1~96.3%.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to a composite catalyst and its preparation method and application, and a method for the co-production of pentamethyldiethylenetriamine from trimethylhydroxyethylethylenediamine. Background Technology

[0002] Trimethylhydroxyethylethylenediamine (TMAEEA) is a reactive, non-emission, equilibrium tertiary amine catalyst widely used in polyether-type polyurethane flexible foams, molding foams, and semi-rigid foams for packaging. It is particularly suitable for automotive foams, does not corrode metals, and is non-polluting to PVC products. Pentamethyldiethylenetriamine (PC-5) is a highly active, strong foaming tertiary amine catalyst used to balance foaming and gelation reactions, and is widely used in various rigid polyurethane foams.

[0003] Currently, the existing methods for synthesizing trimethylhydroxyethyl ethylenediamine (TME) and pentamethyldiethylenetriamine mainly involve amination synthesis using N-methyldiethanolamine as the starting material under the action of a catalyst. For example, patent US6187957B1 discloses a method for synthesizing TME and pentamethyldiethylenetriamine using N-methyldiethanolamine (MDEA), dimethylamine, and hydrogen as raw materials, and 15.5 wt% Cu / TiO2 as a catalyst in a fixed-bed reactor at 200°C and a hydrogen pressure of 3 MPa. The conversion rate of N-methyldiethanolamine is 83.8%, the selectivity of TME is 51.2%, the selectivity of pentamethyldiethylenetriamine is 11.2%, and the overall selectivity is 62.4%. However, existing catalysts exhibit poor selectivity for the target products (TME and pentamethyldiethylenetriamine). Summary of the Invention

[0004] In view of this, the present invention aims to provide a composite catalyst, its preparation method and application, and a method for the co-production of pentamethyldiethylenetriamine from trimethylhydroxyethyl ethylenediamine. The composite catalyst provided by the present invention is used for catalytic amination reaction, and the target products trimethylhydroxyethyl ethylenediamine and pentamethyldiethylenetriamine have high selectivity.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The present invention provides a composite catalyst comprising a support and an active component loaded on the support; the active component comprises elemental silver, elemental cobalt and elemental copper; the support comprises alumina.

[0007] Preferably, the composite catalyst comprises the following components by mass percentage: 0.5-5% silver, 5-25% cobalt, 10-35% copper, and 40-80% alumina.

[0008] This invention provides a method for preparing the composite catalyst described in the above technical solution, comprising the following steps:

[0009] A soluble silver source, a soluble cobalt source, a soluble copper source, a soluble aluminum source, and a carbonate aqueous solution are mixed, allowed to stand for aging, and then calcined to obtain a precursor; the precursor includes silver oxide, cobalt oxide, copper oxide, and aluminum oxide.

[0010] The silver oxide, cobalt oxide, and copper oxide in the precursor are reduced to elemental silver, elemental cobalt, and elemental copper to obtain a composite catalyst.

[0011] Preferably, the mass ratio of silver in the soluble silver source to cobalt in the soluble cobalt source is 1:1 to 50;

[0012] The mass ratio of silver in the soluble silver source to copper in the soluble copper source is 1:2 to 67;

[0013] The mass ratio of silver in the soluble silver source to aluminum in the soluble aluminum source is 1:1.6 to 40.

[0014] Preferably, the mass concentration of the carbonate aqueous solution is 10-30%;

[0015] The molar ratio of silver in the soluble silver source to carbonate in the carbonate aqueous solution is 1:8.3 to 1000.

[0016] Preferably, the gas used for reduction is hydrogen or a hydrogen-nitrogen mixture;

[0017] The volume ratio of hydrogen to nitrogen in the hydrogen-nitrogen mixture is 1 to 9:1.

[0018] This invention provides the application of the composite catalyst described in the above technical solution and the composite catalyst prepared by the above preparation method in the catalytic amination reaction of dimethylamine.

[0019] This invention provides a method for the co-production of pentamethyldiethylenetriamine from trimethylhydroxyethyl ethylenediamine, comprising the following steps:

[0020] In a hydrogen atmosphere, N-methyldiethanolamine, dimethylamine and a catalyst are mixed and subjected to a catalytic amination reaction to obtain trimethylhydroxyethylethylenediamine and pentamethyldiethylenetriamine;

[0021] The catalyst is the composite catalyst described in the above technical solution or the composite catalyst prepared by the preparation method described in the above technical solution.

[0022] Preferably, the mass ratio of N-methyldiethanolamine to catalyst is 5 to 100:1;

[0023] The molar ratio of N-methyldiethanolamine to dimethylamine is 1:1.1 to 2.

[0024] Preferably, the temperature of the catalytic amination reaction is 180–210°C, and the time is 5–14 h;

[0025] The pressure of the hydrogen atmosphere is 1–3 MPa.

[0026] This invention provides a composite catalyst comprising a support and an active component loaded on the support, wherein the active component comprises elemental silver, elemental cobalt, and elemental copper; the support comprises alumina. In the composite catalyst provided by this invention, elemental silver improves the dispersion of elemental cobalt and copper on the surface of the alumina support, thereby enhancing the activity of the composite catalyst. The addition of elemental silver also inhibits the disproportionation reaction of dimethylamine, significantly improving the selectivity for the target products (p-trimethylhydroxyethylethylenediamine and pentamethyldiethylenetriamine) when used for the amination of N-methyldiethanolamine and dimethylamine to prepare trimethylhydroxyethylethylenediamine and pentamethyldiethylenetriamine. Furthermore, the introduction of elemental silver increases the dispersion of elemental cobalt and copper on the catalyst surface or alters their surface structure, reducing the loss of active components (especially elemental copper). Therefore, the composite catalyst provided by this invention can be recycled, reducing catalyst costs. As shown in the test results of the examples, the composite catalyst provided by the present invention can be used to catalyze the amination of N-methyldiethanolamine and dimethylamine to prepare trimethylhydroxyethylethylenediamine and pentamethyldiethylenetriamine. The conversion rate of the raw material N-methyldiethanolamine is 93.7-99.2%, the selectivity of trimethylhydroxyethylethylenediamine is 67.5-76.6%, the selectivity of pentamethyldiethylenetriamine is 19.7-23.4%, and the total selectivity of the target product can reach 89.1-96.3%.

[0027] This invention provides a method for preparing the composite catalyst described in the above-mentioned technical solution. The method involves mixing soluble metal (silver, cobalt, copper, and aluminum) salts and carbonates, followed by static aging. The metal ions in the soluble metal salts react with the carbonates to form metal carbonate precipitates. After calcination, the metal carbonates form precursors in the form of metal oxides (silver oxide, cobalt oxide, copper oxide, and aluminum oxide). The alumina support is a porous oxide with a large specific surface area, and the precursors are adsorbed / attached to the surface or pores of the alumina. The silver oxide, cobalt oxide, and copper oxide in the precursors are then reduced to elemental silver, cobalt, and copper, respectively, to obtain the composite catalyst. This method is simple to operate, low in cost, and suitable for industrial production. Detailed Implementation

[0028] The present invention provides a composite catalyst comprising a support and an active component loaded on the support; the active component comprises elemental silver, elemental cobalt and elemental copper; the support comprises alumina.

[0029] In this invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art.

[0030] In this invention, the composite catalyst preferably comprises the following components by mass percentage: 0.5-5% silver, 5-25% cobalt, 10-35% copper, and 40-80% alumina.

[0031] In this invention, the composite catalyst preferably comprises 0.5-5% silver by mass percentage, more preferably 1-4%, and most preferably 2-3%. The inclusion of silver in the composite catalyst provided by this invention improves the dispersion of cobalt and copper on the alumina support surface, inhibits the disproportionation reaction of dimethylamine, and enhances the catalytic activity and selectivity of the composite catalyst for the target products (trimethylhydroxyethylethylenediamine and pentamethyldiethylenetriamine).

[0032] In this invention, the composite catalyst preferably comprises 5-25% cobalt by mass percentage, more preferably 10-20%, and most preferably 15-18%.

[0033] In this invention, the composite catalyst preferably comprises 10-35% copper by mass percentage, more preferably 15-30%, and most preferably 20-25%. This invention uses cobalt and copper as the active components in the catalytic reaction, which can significantly improve the selectivity of the target products (trimethylhydroxyethylethylenediamine and pentamethyldiethylenetriamine).

[0034] In this invention, the composite catalyst preferably comprises 40-80% alumina, more preferably 45-70%, and most preferably 50-60% by mass percentage.

[0035] This invention provides a method for preparing the composite catalyst described in the above technical solution, comprising the following steps:

[0036] A soluble silver source, a soluble cobalt source, a soluble copper source, a soluble aluminum source, and a carbonate aqueous solution are mixed, allowed to stand for aging, and then calcined to obtain a precursor; the precursor includes silver oxide, cobalt oxide, copper oxide, and aluminum oxide.

[0037] The silver oxide, cobalt oxide, and copper oxide in the precursor are reduced to elemental silver, elemental cobalt, and elemental copper to obtain a composite catalyst.

[0038] The present invention mixes a soluble silver source, a soluble cobalt source, a soluble copper source, a soluble aluminum source and a carbonate aqueous solution, allows them to stand for aging, and then calcines them to obtain a precursor; the precursor includes silver oxide, cobalt oxide, copper oxide and aluminum oxide.

[0039] In this invention, the soluble silver source preferably includes silver nitrate.

[0040] In this invention, the soluble cobalt source preferably includes cobalt nitrate, more preferably cobalt nitrate hexahydrate; the mass ratio of silver in the soluble silver source to cobalt in the soluble cobalt source is preferably 1:1 to 50, more preferably 1:5 to 30, and most preferably 1:10 to 20.

[0041] In this invention, the soluble copper source preferably includes copper nitrate, more preferably copper nitrate trihydrate; the mass ratio of silver in the soluble silver source to copper in the soluble copper source is 1:2 to 67, more preferably 1:10 to 60, and most preferably 1:25 to 40.

[0042] In this invention, the soluble aluminum source preferably includes aluminum nitrate, more preferably aluminum nitrate nonahydrate; the mass ratio of silver in the soluble silver source to aluminum in the soluble aluminum source is 1:1.6 to 40, more preferably 1:2 to 20, and most preferably 1:5 to 10.

[0043] In this invention, the carbonate is preferably sodium carbonate. In this invention, the mass concentration of the carbonate aqueous solution is preferably 10-30%, more preferably 15-25%, and most preferably 20-22%. In this invention, the molar ratio of silver in the soluble silver source to carbonate in the carbonate aqueous solution is preferably 1:8.3-1000, more preferably 1:10-500, and most preferably 1:12.5-200.

[0044] In this invention, the mixing is preferably achieved by stirring. The stirring speed is preferably 50–1000 rpm, more preferably 200–800 rpm, and most preferably 300–600 rpm.

[0045] In this invention, the mixing is preferably performed by mixing a soluble silver source, a soluble cobalt source, a soluble copper source, and a soluble aluminum source, followed by adding an aqueous carbonate solution. In this invention, the aqueous carbonate solution is preferably added dropwise. In this invention, the dropping rate of the aqueous carbonate solution is preferably 3–8 mL / min, more preferably 4–6 mL / min, and most preferably 5–7 mL / min. In this invention, the endpoint of adding the aqueous carbonate solution is preferably reached when the pH of the resulting mixed solution is 7–8, at which point the addition of the aqueous carbonate solution is stopped.

[0046] In this invention, the holding temperature for adding the carbonate aqueous solution is preferably 5–80°C, more preferably 10–60°C, and most preferably 25–50°C. This invention does not specifically limit the heating rate to the holding temperature; it is sufficient to reach 5–80°C, specifically preferably 5°C / min.

[0047] In this invention, the step of allowing the mixture to stand for aging preferably includes stirring the resulting liquid mixture. The stirring time is preferably 1-2 hours.

[0048] In this invention, the static aging time is preferably 12-16 hours, more preferably 13-15 hours, and most preferably 14-14.5 hours; the static aging temperature is preferably 0-100°C, more preferably 10-80°C, and most preferably 25-60°C. This invention involves mixing soluble metal (silver, cobalt, copper, and aluminum) salts and carbonates, followed by static aging. The metal ions in the soluble metal salts react with the carbonates to form metal carbonate precipitates.

[0049] In this invention, after the static aging process, the aging solution obtained from the static aging preferably further includes sequentially performing solid-liquid separation, water washing, drying, grinding, and sieving. This invention does not specifically limit the method of solid-liquid separation; any method well-known to those skilled in the art can be used to separate the solids and reaction liquid in the aging solution, specifically filtration is preferred. In this invention, the number of water washing cycles is preferably three. In this invention, the drying temperature is preferably 110–120°C, more preferably 112–118°C, and most preferably 114–116°C; the drying time is preferably 8–12 hours, more preferably 9–11 hours, and most preferably 10–10.5 hours. In this invention, the particle size of the solid powder obtained from sieving is preferably 120–200 mesh, more preferably 130–180 mesh, and most preferably 150–160 mesh. This invention does not specifically limit the grinding and sieving processes; any method well-known to those skilled in the art can be used to achieve the particle size of the solid powder within the above ranges.

[0050] In this invention, the calcination temperature is preferably 550–700°C, more preferably 600–650°C, and most preferably 610–630°C; the calcination time is preferably 4–6 hours, more preferably 5 hours. This invention, through calcination, transforms metal carbonate precipitates into oxidized precursors.

[0051] After obtaining the precursor, the present invention preferably reduces the silver oxide, cobalt oxide and copper oxide in the precursor to elemental silver, elemental cobalt and elemental copper to obtain a composite catalyst.

[0052] In this invention, the reduction method is preferably to purge the precursor with a gas. The gas used for reduction is preferably hydrogen or a hydrogen-nitrogen mixture. The volume ratio of hydrogen to nitrogen in the hydrogen-nitrogen mixture is preferably 1–9:1, more preferably 3–8:1, and most preferably 4–6:1. The reduction temperature is preferably 350–500°C, more preferably 380–480°C, and most preferably 400–450°C; the reduction time is preferably 0.5–1.5 h, more preferably 0.8–1.2 h, and most preferably 0.9–1 h. This invention uses hydrogen or a hydrogen-nitrogen mixture to purge the precursor, reducing silver oxide, cobalt oxide, and copper oxide in the precursor to elemental silver, cobalt, and copper. However, the oxygen and aluminum atoms in alumina have a strong bond and will not be reduced under the above conditions, thus remaining as alumina itself. This forms an active component comprising elemental silver, cobalt, and copper, as well as an alumina support for the active component, thus preparing a composite catalyst.

[0053] This invention provides the application of the composite catalyst described in the above technical solution and the composite catalyst prepared by the above preparation method in the catalytic amination reaction of dimethylamine.

[0054] This invention provides a method for the co-production of pentamethyldiethylenetriamine from trimethylhydroxyethyl ethylenediamine, comprising the following steps:

[0055] In a hydrogen atmosphere, N-methyldiethanolamine, dimethylamine and a catalyst are mixed and subjected to a catalytic amination reaction to obtain trimethylhydroxyethylethylenediamine and pentamethyldiethylenetriamine;

[0056] The catalyst is the composite catalyst described in the above technical solution or the composite catalyst prepared by the preparation method described in the above technical solution.

[0057] In this invention, the mass ratio of N-methyldiethanolamine to catalyst is preferably 5 to 100:1, more preferably 20 to 80:1, and most preferably 40 to 60:1.

[0058] In this invention, the purity of the dimethylamine is preferably ≥98wt%. In this invention, the molar ratio of N-methyldiethanolamine to dimethylamine is preferably 1:1.1–2, more preferably 1:1.4–1.8, and most preferably 1:1.5–1.6.

[0059] In this invention, the pressure of the hydrogen atmosphere is preferably 1 to 3 MPa, more preferably 2 MPa.

[0060] In this invention, the temperature of the catalytic amination reaction is preferably 180–210°C, more preferably 190–200°C, and most preferably 192–195°C; the time of the catalytic amination reaction is preferably 5–14 h, more preferably 6–12 h, and most preferably 8–10 h; the pressure of the catalytic amination reaction is preferably 5–8 MPa, more preferably 5.5–7 MPa, and most preferably 6–6.5 MPa. In this invention, the obtained trimethylhydroxyethylethylenediamine and pentamethyldiethylenetriamine are preferably a mixture.

[0061] To further illustrate the present invention, the following detailed descriptions, in conjunction with embodiments, describe the composite catalyst provided by the present invention, its preparation method and application, and the method for co-producing pentamethyldiethylenetriamine from trimethylhydroxyethyl ethylenediamine, but these descriptions should not be construed as limiting the scope of protection of the present invention.

[0062] In all embodiments and comparative examples of the present invention, the hydrogen gas is high-purity hydrogen gas, and the nitrogen gas is high-purity nitrogen gas.

[0063] Example 1

[0064] Dissolve 7.1g silver nitrate, 125.9g cobalt nitrate hexahydrate, 114g copper nitrate trihydrate, and 331.1g aluminum nitrate nonahydrate in 1500g water. Start stirring (at 350rpm) and heat to 50℃ at a rate of 5℃ / min. Add a 20wt% sodium carbonate aqueous solution dropwise at a rate of 5mL / min using a horizontal flow pump. When the pH of the system reaches 7–8, stop adding the sodium carbonate aqueous solution and continue stirring for 1 hour. Then turn off the stirring. The catalyst was allowed to stand and age at 35°C for 12 hours, filtered, and the filter cake was washed three times with 1000g of deionized water. It was then dried at 120°C for 12 hours, ground and sieved to 150 mesh, and calcined at 600°C for 4 hours to obtain 127g of oxidized catalyst. After activation with high-purity hydrogen at 450°C for 2 hours, the temperature was lowered to 55°C, purged with high-purity nitrogen for 1 hour, and then cooled to room temperature to obtain a 3wt% silver, 17wt% cobalt, and 20wt% copper / alumina catalyst.

[0065] Example 2

[0066] The composite catalyst was prepared according to the preparation method of Example 1, except that the activation temperature was 350°C, and a 3wt% silver, 17wt% cobalt, and 20wt% copper / alumina catalyst was obtained.

[0067] Example 3

[0068] The composite catalyst was prepared according to the preparation method of Example 1, except that the mass of silver nitrate was reduced from 7.1g to 2.4g and the mass of aluminum nitrate nonahydrate was increased from 331.1g to 342.2g, resulting in a 1wt% silver, 17wt% cobalt, and 20wt% copper / alumina catalyst.

[0069] Example 4

[0070] The recovered (after one-time catalytic use) 3wt% silver 17wt% cobalt 20wt% copper / alumina catalyst was washed with water three times, dried at 120℃ for 8 hours, activated with high-purity hydrogen at 450℃ for 2 hours, cooled to 55℃, purged with high-purity nitrogen for 1 hour, and then cooled to room temperature to obtain the recovered 3wt% silver 17wt% cobalt 20wt% copper / alumina catalyst.

[0071] Comparative Example 1

[0072] The composite catalyst was prepared according to the preparation method of Example 1. The only difference from Example 1 was that silver nitrate and cobalt nitrate hexahydrate were not added, and the mass of aluminum nitrate nonahydrate was increased from 331.1 g to 441.5 g to obtain a 20 wt% copper / alumina catalyst.

[0073] Comparative Example 2

[0074] The composite catalyst was prepared according to the preparation method of Comparative Example 1, except that the activation temperature was 250℃, and a 20wt% copper / alumina catalyst was obtained.

[0075] Comparative Example 3

[0076] The composite catalyst was prepared according to the preparation method of Example 1. The only difference from Example 1 was that silver nitrate and copper nitrate trihydrate were not added, and the mass of aluminum nitrate nonahydrate was increased from 331.1 g to 458.1 g, resulting in a 17 wt% cobalt / alumina catalyst.

[0077] Comparative Example 4

[0078] The composite catalyst was prepared according to the preparation method of Example 1. The only difference from Example 1 was that silver nitrate was not added, and the mass of aluminum nitrate nonahydrate was increased from 331.1 g to 347.7 g, resulting in a 7 wt% cobalt 20 wt% copper / alumina catalyst.

[0079] Comparative Example 5

[0080] The composite catalyst was prepared according to the preparation method of Example 1, except that cobalt nitrate hexahydrate was not added, the mass of aluminum nitrate nonahydrate was increased from 331.1 g to 424.9 g, and the activation temperature was 250 °C, resulting in a 3 wt% silver 20 wt% copper / alumina catalyst.

[0081] Comparative Example 6

[0082] The composite catalyst was prepared according to the preparation method of Example 1. The only difference from Example 1 was that copper nitrate trihydrate was not added, and the mass of aluminum nitrate nonahydrate was increased from 331.1 g to 441.5 g, resulting in a 3 wt% silver 17 wt% cobalt / alumina catalyst.

[0083] Example 5

[0084] 10g of the composite catalysts prepared in Examples 1-4 and Comparative Examples 1-6 and 120g of N-methyldiethanolamine were added to a 500mL reactor. The reactor was tightened and purged with high-purity nitrogen for 5min at room temperature to remove air. 68g of liquid dimethylamine was pumped into the reactor using a plunger pump, and 1.5MPa of hydrogen gas was introduced. Stirring was started (stirring speed was 600rpm), and the temperature was increased to 200℃ at a rate of 10℃ / min. The reaction was carried out at a pressure of 6MPa for 10h. The reaction solution was cooled to room temperature, the catalyst was recovered by filtration, and the reaction solution was analyzed by gas chromatography. The analysis results are shown in Table 1.

[0085] The gas chromatography analysis conditions were as follows: HP-5 column; vaporization chamber temperature 300℃; FID detector temperature 300℃; column oven temperature programmed: 0–2 min, 120℃; 2–18.5 min, uniformly increased from 120℃ to 285℃; 18.5–28.5 min, 285℃.

[0086] Table 1. Results of the reaction catalyzed by the composite catalyst for the synthesis of trimethylhydroxyethylethylenediamine and pentamethyldiethylenetriamine via the amination of N-methyldiethanolamine and dimethylamine.

[0087]

[0088] Table 1 shows the reaction results of the composite catalyst catalyzing the synthesis of trimethylhydroxyethyl ethylenediamine and pentamethyldiethylenetriamine from N-methyldiethanolamine and dimethylamine. As shown in Table 1, under the same reaction conditions, the addition of silver significantly improves both the activity and selectivity of the composite catalyst for trimethylhydroxyethyl ethylenediamine. Using the composite catalyst provided in this invention, in the catalytic synthesis of trimethylhydroxyethyl ethylenediamine and pentamethyldiethylenetriamine from N-methyldiethanolamine, the conversion rate of the raw material N-methyldiethanolamine is 93.7–99.2%, the selectivity of trimethylhydroxyethyl ethylenediamine is 67.5–76.6%, the selectivity of pentamethyldiethylenetriamine is 19.7–23.4%, and the total selectivity of the target products can reach 89.1–96.3%, indicating high selectivity for the target products (trimethylhydroxyethyl ethylenediamine and pentamethyldiethylenetriamine). In addition, the composite catalyst prepared in Example 4 was used for catalysis, and the catalyst performance was comparable to that of the newly prepared composite catalyst. This indicates that after the composite catalyst has been used once, it can still be used for the reaction after filtration, recovery, water washing and drying, and the catalyst performance has hardly decreased.

[0089] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A composite catalyst, comprising a carrier and an active component supported on the carrier; the active component is silver, cobalt and copper; the carrier is alumina; the composite catalyst comprises the following components in mass percentage: silver 0.5-5%, cobalt 5-25%, copper 10-35% and alumina 40-80%. The method comprises the following steps:

2. A process for the preparation of the composite catalyst of claim 1, characterized in that, mixing a soluble silver source, a soluble cobalt source, a soluble copper source, a soluble aluminum source and an aqueous carbonate solution, aging, calcining to obtain a precursor; the precursor comprises silver oxide, cobalt oxide, copper oxide and alumina; reducing the silver oxide, cobalt oxide and copper oxide in the precursor to silver, cobalt and copper to obtain the composite catalyst. The mass ratio of silver in the soluble silver source to cobalt in the soluble cobalt source is 1:1-50; 3. The production method according to claim 2, characterized by, The mass ratio of silver in the soluble silver source to copper in the soluble copper source is 1:2-67; The mass ratio of silver in the soluble silver source to aluminum in the soluble aluminum source is 1:1.6-40. The mass concentration of the aqueous carbonate solution is 10-30%; 4. The production method according to claim 2 or 3, characterized by, The molar ratio of silver in the soluble silver source to carbonate in the aqueous carbonate solution is 1:8.3-1000. The gas used for reduction is hydrogen or hydrogen-nitrogen mixed gas; 5. The production method according to claim 2 or 3, characterized by, The volume ratio of hydrogen to nitrogen in the hydrogen-nitrogen mixed gas is 1-9:

1.

6. The use of the composite catalyst of claim 1 or the composite catalyst prepared by the method of any one of claims 2-5 in catalyzing the amination reaction of dimethylamine. The method comprises the following steps:

7. A process for the co-production of trimethylhydroxyethyl ethylenediamine and pentamethyldiethylenetriamine, characterized in that, mixing N-methyl diethanolamine, dimethylamine and a catalyst in a hydrogen atmosphere to perform a catalytic amination reaction to obtain trimethylhydroxyethyl ethylenediamine and pentamethyl diethylenetriamine; The catalyst is the composite catalyst of claim 1 or the composite catalyst prepared by the method of any one of claims 2-5. The mass ratio of N-methyl diethanolamine to catalyst is 5-100:1; 8. The method of claim 7, wherein, The molar ratio of N-methyl diethanolamine to dimethylamine is 1:1.1-2. The temperature of the catalytic amination reaction is 180-210°C and the time is 5-14h; 9. The method according to claim 7 or 8, characterized in that, The pressure of the hydrogen atmosphere is 1-3 MPa. ​

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