Hydrogenation catalyst, process for its preparation and use in the hydrogenation of ethyl acetate to ethanol

Abstract

This invention discloses a hydrogenation catalyst, its preparation method, and its application in the hydrogenation of ethyl acetate to ethanol. The hydrogenation catalyst of this invention comprises a carbon-modified alumina support and an active component supported on the carbon-modified alumina support; the active component includes a main metal active component and an optional auxiliary metal active component; the main metal active component includes Cu; the auxiliary metal active component is selected from at least one of Zn and Mg; the specific surface area of ​​the carbon-modified alumina support is ≥300 m² / g. 2 / g. The catalyst of this invention, using carbon-modified alumina as a support, has a higher external surface area, higher utilization rate of active components, and higher catalytic activity. When using the catalyst of this invention for the hydrogenation of ethyl acetate to ethanol, the conversion rate of acetate and the selectivity of ethanol can be improved.

Description

Technical Field

[0001] This invention relates to the field of hydrogenation technology for the production of ethanol from ethyl acetate, and more specifically, to hydrogenation catalysts, their preparation methods, and their application in the hydrogenation of ethyl acetate to ethanol. Background Technology

[0002] Traditional ethanol production technologies mainly include ethylene hydration, bio-fermentation, and the hydrogenation of carboxylic acid esters. Ethylene hydration uses ethylene, a petroleum cracking product, as a raw material, and hydrates it to obtain ethanol—a petroleum route. Bio-fermentation uses various sugary agricultural products, agricultural and forestry byproducts, and wild plants as raw materials, hydrolyzing and fermenting disaccharides and polysaccharides to convert them into monosaccharides, which are then further converted into ethanol. Carboxylic acid ester hydrogenation refers to the hydrogenation of acetic acid or ethyl acetate to produce ethanol. Currently, acetic acid and acetate ester production technologies are mature and inexpensive; therefore, the hydrogenation of acetate esters to produce ethanol is a valuable industrial route that has attracted widespread attention.

[0003] CN1974510A discloses methods for homogeneous hydrogenation and liquid-solid phase hydrogenation of fatty acids and their derivatives on Ru-based catalysts to prepare alcohols. These techniques all involve relatively expensive metals and require relatively harsh reaction conditions.

[0004] CN101934228A discloses a catalyst for the hydrogenation of ethyl acetate to ethanol, its preparation method and application, wherein the main component of the catalyst is Cu or CuO, the support is SiO2 or Al2O3, the acetate conversion rate is greater than 80%, and the ethanol selectivity is greater than 90%.

[0005] CN102327774A discloses a copper-based catalyst for the hydrogenation of acetate to ethanol, which achieves a methyl acetate conversion rate of 85% and an ethanol selectivity of 91%, but has low reaction efficiency.

[0006] Currently, copper-based catalysts prepared by precipitation or impregnation methods are all oxide-supported catalysts, with alumina and silica supports being the most common choices. For example, CN102093162A discloses a method for preparing ethanol by hydrogenation of ethyl acetate, in which the main component of the catalyst is Cu or CuO, the support is SiO2, and transition metals are used as promoters. The selectivity of ethanol can reach up to 97%.

[0007] CN102093162A discloses a method for preparing ethanol by hydrogenation of ethyl acetate. The catalyst's main active component is Cu, with SiO2 as the support and at least one transition metal and / or alkali metal as an auxiliary agent. This method exhibits high space-time yield and high ethanol selectivity; under optimal process conditions, the ethanol selectivity can reach 97%.

[0008] While silica supports have their advantages, their low strength limits the application of catalysts, and their thermal conductivity is far inferior to that of aluminum-containing supports. Copper grains are also prone to aggregation, leading to a decrease in catalyst activity. Therefore, alumina supports have a better application prospect. However, the inventors have found that the acidity of alumina supports is unfavorable for the hydrogenation reaction of acetate esters, and the specific surface area of ​​alumina is smaller than that of silica, which is detrimental to the dispersion of active metals. How to solve the acidity of the support itself and increase its specific surface area has become a challenge in support research. Summary of the Invention

[0009] To address the problems in existing technologies, this invention proposes a hydrogenation catalyst, its preparation method, and its application in the hydrogenation of ethyl acetate to ethanol. The catalyst of this invention utilizes a carbon-modified alumina support with a large specific surface area. This large surface area and significantly reduced surface acidity help avoid byproducts generated by acid catalysis, thereby improving reaction selectivity. Using the catalyst of this invention for the hydrogenation of ethyl acetate to ethanol can improve both the conversion rate of acetate and the selectivity of ethanol.

[0010] One objective of this invention is to provide a hydrogenation catalyst comprising a carbon-modified alumina support and an active component supported on the carbon-modified alumina support.

[0011] The active components include a primary metal active component and an optional auxiliary metal active component;

[0012] The main metal active component includes Cu;

[0013] The auxiliary metal active component is selected from at least one of Zn and Mg;

[0014] The specific surface area of ​​the carbon-modified alumina support is ≥300 m². 2 / g, preferably 320-460m 2 / g.

[0015] The catalyst of this invention, which uses carbon-modified alumina as a support, has a higher external surface area, higher utilization rate of active components, and higher catalytic activity.

[0016] In the hydrogenation catalyst described in this invention, preferably,

[0017] Based on the weight of the carbon-modified alumina support as 100%,

[0018] The carbon content in the carrier is 0.01–10 wt%; preferably 0.1–1 wt%.

[0019] In the hydrogenation catalyst described in this invention, preferably,

[0020] Based on the catalyst by weight of 100%,

[0021] The content of the main metal active component is 1-40 wt%, preferably 20-40 wt%.

[0022] When it contains a contributing metal active component, the mass ratio of the contributing metal active component to the metal in the main metal active component is 1:1-10, preferably 1:5-10.

[0023] A second objective of this invention is to provide a method for preparing the hydrogenation catalyst described in one objective of this invention, comprising the following steps:

[0024] (1) Boehmite was added to a nitrogen-containing polymer solution to react and obtain boehmite modified with nitrogen-containing polymer.

[0025] (2) The nitrogen-containing polymer-modified boehmite is calcined under a protective atmosphere to obtain a carbon-modified alumina support.

[0026] (3) The carbon-modified alumina support is contacted with the active component precursor solution, followed by post-treatment and calcination under a protective atmosphere to obtain the hydrogenation catalyst.

[0027] In the preparation method of the hydrogenation catalyst described in this invention, preferably,

[0028] In step (1), the preparation method of the boehmite includes the following steps:

[0029] (1-1) Add sodium aluminate solution dropwise to aluminum sulfate solution until alkaline, mix thoroughly, and obtain boehmite precursor;

[0030] (1-2) The boehmite precursor is subjected to crystallization treatment and post-treatment to obtain the boehmite.

[0031] In the preparation method of the hydrogenation catalyst described in this invention, preferably,

[0032] In step (1-1), the sodium-aluminum molar ratio in the sodium aluminate solution is 4.5:1; preferably, the sodium aluminate solution also contains sodium hydroxide.

[0033] Sodium hydroxide is used to adjust the pH value of the solution and also to stabilize sodium aluminate, because sodium aluminate reacts with carbon dioxide in the air in aqueous solution.

[0034] The concentration of aluminum ions in the sodium aluminate solution is 0.1-0.8 mol / L;

[0035] The concentration of aluminum sulfate solution is 0.1-0.7 mol / L;

[0036] The pH range corresponding to alkalinity is 8-11;

[0037] The mixing method is stirring, preferably for 10-60 minutes; and / or,

[0038] Steps (1-2),

[0039] The crystallization temperature is 50-120℃;

[0040] The crystallization process takes 2-12 hours.

[0041] Post-treatment methods include at least one of filtration and washing;

[0042] Preferably, the crystallization treatment is a hydrothermal crystallization treatment;

[0043] More preferably, the method for preparing the boehmite includes the following steps:

[0044] (1) Weigh 22.56g of sodium hydroxide and 17.5g of sodium aluminate and dissolve them in 250ml of deionized water for later use.

[0045] (2) Weigh 83.4g of aluminum sulfate into 250-2500ml of deionized water, add the sodium aluminate solution prepared in step 1) dropwise into the aluminum sulfate solution with a concentration of 0.1-0.7mol / L until the pH is 9.5-10, stir at room temperature for 10-60min to obtain boehmite precursor.

[0046] (3) Continue crystallization at 50-120℃ for 2-12 hours to obtain boehmite with a large specific surface area of ​​300-380 μm². 2 / g.

[0047] The boehmite prepared in this invention is a boehmite with a large specific surface area.

[0048] In the preparation method of the hydrogenation catalyst described in this invention, preferably,

[0049] In step (1),

[0050] The nitrogen-containing polymer is selected from one or a combination of polyvinylimidazolium, polyvinylpyrrolidone, or polyvinylpyridine; and / or,

[0051] In the nitrogen-containing polymer solution, the solvent is selected from one or a combination of methanol or ethanol; and / or,

[0052] The mass ratio of the boehmite to the nitrogen-containing polymer is 1-100:1; and / or,

[0053] The reaction temperature is 100–120°C; and / or,

[0054] The reaction time is 4–10 hours; and / or,

[0055] Preferably,

[0056] The concentration of the nitrogen-containing polymer solution is 0.1–2 wt%; more preferably 0.6–1.8 wt%.

[0057] In the preparation method of the hydrogenation catalyst described in this invention, preferably,

[0058] In step (2),

[0059] The roasting temperature is 400–800℃; and / or,

[0060] The roasting time is 2–10 hours; and / or,

[0061] The protective atmosphere is selected from at least one of nitrogen atmosphere and inert atmosphere, preferably, the inert atmosphere is at least one of nitrogen atmosphere, argon atmosphere and helium atmosphere.

[0062] In the preparation method of the hydrogenation catalyst described in this invention, preferably,

[0063] In step (3), the active component precursor solution includes a soluble metal salt of the main metal active component and, optionally, a soluble metal salt of the auxiliary metal active component; preferably,

[0064] When the soluble metal salt of the auxiliary metal active component is not present, the carbon-modified alumina support is first contacted once with the precursor solution of the main metal active component, followed by post-treatment and a single calcination under a protective atmosphere to obtain the primary calcined product or the catalyst. Optionally, the primary calcined product is contacted a second time with the precursor solution of the main metal active component, followed by post-treatment and a second calcination under a protective atmosphere to obtain the catalyst; or...

[0065] When a soluble metal salt containing a contributing metal active component is used, the carbon-modified alumina support is first contacted once with a precursor solution of the main metal active component, followed by post-treatment and calcination under a protective atmosphere to obtain a primary calcined product. Then, the primary calcined product is contacted a second time with a precursor solution of the contributing metal active component, followed by post-treatment and calcination under a protective atmosphere to obtain the catalyst.

[0066] In the preparation method of the hydrogenation catalyst described in this invention, preferably,

[0067] In step (3), the active component precursor solution includes a soluble metal salt of the main metal active component and, optionally, a soluble metal salt of the auxiliary metal active component.

[0068] Preferably,

[0069] The soluble metal salt of the main metal active component is selected from the soluble nitrate of the main metal active component; and / or,

[0070] The soluble metal salt of the auxiliary metal active component is selected from at least one of the soluble nitrate, soluble acetate, and soluble chloride salts of the auxiliary metal active component; and / or,

[0071] The calculation is based on the sum of the mass of the metal element in the soluble metal salt of the main metal active component, the mass of the metal element in the soluble metal salt of the optionally auxiliary metal active component, and the mass of the carrier, which is 100%.

[0072] The mass content of the metal element in the soluble metal salt of the main metal active component is 1-40 wt%, preferably 20-40 wt%.

[0073] When a metal-enhancing active component is present, the mass ratio of the metal element in the soluble metal salt of the main metal active component to the metal element in the soluble metal salt of the metal-enhancing active component in the precursor solution is 1:1-10, preferably 1:5-10; more preferably,

[0074] The concentration of the soluble metal salt of the main metal active component in the precursor solution is 20-66.7 wt%.

[0075] The concentration of the soluble metal salt of the auxiliary metal active component in the precursor solution is 4-20 wt%.

[0076] More preferably,

[0077] The mass ratio of the carbon-modified alumina support to the metal element in the soluble metal salt of the main metal active component is 1.5:1-4:1;

[0078] The mass ratio of the carbon-modified alumina support to the metal element in the soluble metal salt of the auxiliary metal active component is 11:1-24:1.

[0079] In the preparation method of the hydrogenation catalyst described in this invention, preferably,

[0080] In step (3), the methods of primary contact and secondary contact are each independently selected from at least one of immersion and spraying;

[0081] The temperatures for the first and second contacts are each independently 15-40℃; and / or,

[0082] The duration of the first and second contact is independently 10-60 minutes; and / or,

[0083] The temperatures for the first and second firings are each independently 400-800℃; and / or,

[0084] The initial and secondary roasting times are each 2-10 hours independently; and / or,

[0085] Post-processing methods each independently include drying; and / or,

[0086] The protective atmosphere is independently selected from at least one of nitrogen atmosphere and inert atmosphere;

[0087] Preferably, the drying temperature in the post-treatment is 100-130°C; and / or, the drying time is 8-15 hours.

[0088] The third objective of this invention is to provide a method for preparing ethanol by hydrogenation of ethyl acetate, comprising the following steps:

[0089] Ethyl acetate and hydrogen are hydrogenated in the presence of a catalyst to prepare a product containing ethanol.

[0090] The catalyst is the catalyst described in one of the objectives of this invention or the catalyst prepared by the preparation method described in another objective of this invention.

[0091] In the method for preparing ethanol by hydrogenation of ethyl acetate according to the present invention, preferably,

[0092] The liquid hourly space velocity (LHSV) of ethyl acetate is 0.1–4 h⁻¹. -1 The preferred value is 0.1-2. -1 ;

[0093] The molar ratio of hydrogen to ethyl acetate is (15-50):1; preferably (20-40):1.

[0094] The temperature for hydrogenation is 100-350℃; preferably 200-260℃.

[0095] The pressure for the hydrogenation reaction is 1–5 MPa; preferably 2–4 MPa.

[0096] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0097] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0098] Compared with the prior art, the present invention has at least the following advantages:

[0099] (1) The carbon-modified alumina supported catalyst used in this invention has a higher surface area, more uniform distribution of active components, higher utilization rate, and higher catalytic activity.

[0100] (2) The surface acidity of the carbon-modified large specific surface area alumina carrier used in this invention is significantly reduced, which helps to avoid byproducts generated by acid catalysis, thereby improving reaction selectivity.

[0101] In summary, the carbon-modified alumina-supported catalyst with a large specific surface area of ​​the present invention belongs to a new type of supported catalyst with a novel structure. The carbon supported on the surface effectively reduces the acidity of the catalyst and improves its selectivity, resulting in high catalytic activity and low loading of active components in the catalyst of the present invention. Detailed Implementation

[0102] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0103] It should also be noted that the various specific technical features described in the following embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this invention.

[0104] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0105] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0106] Characterization methods for XRF:

[0107] After the sample is pressed into a tablet, the elemental composition and relative content of the sample surface are analyzed using an X-ray photoelectron spectrometer after vacuuming.

[0108] Example 1

[0109] (1) Weigh 22.56g NaOH and 17.5g sodium aluminate and dissolve them in 250ml of deionized water to prepare a 0.5mol / L sodium aluminate solution.

[0110] (2) Weigh 88.4g of aluminum sulfate into 500ml of deionized water, add the sodium aluminate solution prepared in step 1) dropwise into the aluminum sulfate solution with a concentration of 0.5mol / L until the pH is 9.5, stir at room temperature for 30min to obtain boehmite precursor.

[0111] (3) The above suspension was transferred to a high-pressure reactor and crystallized at 80°C for 4 hours to obtain boehmite with a large specific surface area.

[0112] (4) 100g of the large specific surface area boehmite obtained above was immersed in an ethanol solution of polyvinyl imidazole with a concentration of 1wt% (where the amount of polyvinyl imidazole was 1g), and then transferred to a hydrothermal reactor and reacted at 100℃ for 10h. After cooling and filtration, it was dried at 80℃ for 4h, and then placed in a nitrogen atmosphere and calcined at 400℃ for 10h to obtain a support (carbon-modified alumina support).

[0113] (5) Place 20 g of the support in a 66.7 wt% copper nitrate aqueous solution (of which the mass of copper element is 6.69 g), immerse it at room temperature for 20 minutes, remove the support, drain it, dry it at 120 °C for 12 hours, and calcine it at 400 °C for 3 hours in a nitrogen atmosphere to obtain the catalyst.

[0114] The carbon-modified alumina support prepared by the above method has a specific surface area of ​​320 m². 2 / g; the carbon content in the carbon-modified alumina support is 0.12wt%.

[0115] XRF characterization showed that the copper loading in the catalyst was 25 wt%.

[0116] Example 2

[0117] Steps (1-4) are the same as in Example 1.

[0118] 5) Place 20 g of the support in a 66.7 wt% copper nitrate aqueous solution (of which the mass of copper element is 7.81 g), immerse for 20 minutes at room temperature, remove the support, drain, dry at 120 °C for 12 hours, and calcine at 400 °C for 3 hours in a nitrogen atmosphere to obtain the catalyst.

[0119] XRF characterization showed that the copper loading in the catalyst was 28 wt%.

[0120] Example 3

[0121] Steps (1-4) are the same as in Example 1.

[0122] (5) Place 20 g of the support in a 66.7% copper nitrate aqueous solution (with a copper content of 7.39 g), immerse it at room temperature for 20 minutes, remove the support, drain it, dry it at 120°C for 12 hours, and calcine it at 400°C for 3 hours in a nitrogen atmosphere to obtain a catalyst intermediate with a copper loading of 27 wt%.

[0123] (6) The catalyst intermediate prepared above was placed in a 66.7% copper nitrate aqueous solution (where the mass of copper element was 2.46 g), immersed at room temperature for 20 minutes, then removed from the support, drained, dried at 120°C for 12 hours, and calcined at 400°C for 3 hours in a nitrogen atmosphere to obtain the catalyst.

[0124] XRF characterization showed that the copper loading in the catalyst was 32.9 wt%.

[0125] Example 4

[0126] Steps (1-4) are the same as in Example 1.

[0127] (5) Place 20 g of the support in a 66.7% copper nitrate aqueous solution (with a copper content of 7.39 g), immerse it at room temperature for 20 minutes, remove the support, drain it, dry it at 120°C for 12 hours, and calcine it at 400°C for 3 hours in a nitrogen atmosphere to obtain a catalyst intermediate with a copper loading of 27 wt%.

[0128] (6) The catalyst intermediate prepared above was placed in a 66.7% copper nitrate aqueous solution (with a copper element mass of 5.39 g), immersed at room temperature for 20 minutes, then removed from the support, drained, dried at 120°C for 12 hours, and calcined at 400°C for 3 hours in a nitrogen atmosphere to obtain the catalyst.

[0129] XRF characterization showed that the copper loading in the catalyst was 38.9 wt%.

[0130] Example 5

[0131] Steps (1-4) are the same as in Example 1.

[0132] (5) Place 20 g of the support in a 66.7% copper nitrate aqueous solution (with a copper content of 7.39 g), immerse it at room temperature for 20 minutes, remove the support, drain it, dry it at 120°C for 12 hours, and calcine it at 400°C for 3 hours in a nitrogen atmosphere to obtain a catalyst intermediate with a copper loading of 27 wt%.

[0133] (6) The catalyst intermediate prepared above was placed in a 66.7 wt% copper nitrate aqueous solution and a 10 wt% magnesium nitrate aqueous solution (where the mass of copper element is 2.46 g and the content of magnesium is 1.1 g), immersed at room temperature for 20 minutes, then removed from the support, drained, dried at 120°C for 12 hours, and calcined at 400°C for 3 hours in a nitrogen atmosphere to obtain the catalyst.

[0134] XRF characterization showed that the catalyst contained 31 wt% copper and 3.4 wt% magnesium.

[0135] Example 6

[0136] Steps (1-4) are the same as in Example 1.

[0137] (5) Place 20 g of the support in a 66.7% copper nitrate aqueous solution (with a copper content of 7.39 g), immerse it at room temperature for 20 minutes, remove the support, drain it, dry it at 120°C for 12 hours, and calcine it at 400°C for 3 hours in a nitrogen atmosphere to obtain a catalyst intermediate with a copper loading of 27 wt%.

[0138] (6) The intermediate prepared above was placed in a mixed solution consisting of 66.7 wt% copper nitrate aqueous solution and 10 wt% zinc nitrate solution (where the mass of copper element is 2.46 g and the mass of zinc element is 1.71 g), immersed at room temperature for 20 minutes, then the support was removed, drained, dried at 120°C for 12 hours, and calcined at 400°C for 3 hours in a nitrogen atmosphere to obtain the catalyst.

[0139] XRF characterization showed that the catalyst contained 31 wt% copper and 5.1 wt% zinc.

[0140] Comparative Example 1

[0141] The catalyst was prepared according to the method of Example 1, except that conventional alumina (specific surface area 236 μm) was used directly. 2 / g) as a carrier.

[0142] The alumina support has a water absorption rate of 105%. 20 g of the support was placed in a 66.7 wt% copper nitrate aqueous solution (of which the mass of copper element was 6.69 g) and immersed for 20 minutes at room temperature. The support was then removed, drained, dried at 120 °C for 12 hours, and calcined at 400 °C for 3 hours in a nitrogen atmosphere to obtain the catalyst.

[0143] XRF characterization showed that the copper loading in the catalyst was 24 wt%.

[0144] Comparative Example 2

[0145] The catalyst was prepared according to the method in Example 5, except that a conventional alumina support (specific surface area 236 μm) was used. 2 / g).

[0146] XRF characterization showed that the catalyst contained 30.1 wt% copper and 3.1 wt% magnesium.

[0147] Comparative Example 3

[0148] The catalyst was prepared according to the method of Example 6, except that an alumina support was used.

[0149] XRF characterization showed that the catalyst contained 30.2 wt% copper and 4.9 wt% zinc.

[0150] Example 7

[0151] The catalyst performance was evaluated using a fixed-bed reactor for the gas-phase hydrogenation of ethyl acetate. 40 mL of catalyst was added to the fixed-bed reactor. The reaction conditions and test results are shown in Table 1. The reaction products were quantified using gas chromatography with an FID detector. Table 1 presents the analysis results after 80 hours of reaction.

[0152] Table 1

[0153]

[0154] The results from Comparative Example 1 and Example 1, Comparative Example 2 and Example 5, and Comparative Example 3 and Example 6 all show that the catalyst of the present invention exhibits better catalytic performance compared to the comparative examples. In summary, using the catalyst of the present invention for the hydrogenation of ethyl acetate to ethanol can improve the conversion rate of acetate and the selectivity of ethanol.

[0155] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A hydrogenation catalyst, characterized in that: The hydrogenation catalyst comprises a carbon-modified alumina support and an active component supported on the carbon-modified alumina support. The active components include a primary metal active component and an optional auxiliary metal active component; The main metal active component is Cu; The auxiliary metal active component is selected from at least one of Zn and Mg; The specific surface area of ​​the carbon-modified alumina support is ≥300 m². 2 / g; The method for preparing carbon-modified alumina support is as follows: boehmite is added to a nitrogen-containing polymer solution for reaction to obtain boehmite modified with nitrogen-containing polymer; the boehmite modified with nitrogen-containing polymer is calcined under a protective atmosphere to obtain carbon-modified alumina support; the nitrogen-containing polymer is selected from one or a combination of polyvinylimidazolium, polyvinylpyrrolidone, or polyvinylpyridine.

2. The hydrogenation catalyst according to claim 1, characterized in that: The specific surface area of ​​the carbon-modified alumina support is 320-460 m². 2 / g.

3. The hydrogenation catalyst according to claim 1, characterized in that: Based on the weight of the carbon-modified alumina carrier as 100%, The carbon content in the carrier is 0.01~10wt%.

4. The hydrogenation catalyst according to claim 3, characterized in that: Based on the weight of the carbon-modified alumina carrier as 100%, The carbon content in the carrier is 0.1~1wt%.

5. The hydrogenation catalyst according to claim 1, characterized in that: Based on the catalyst by weight of 100%, The content of the main metal active component is 1~40wt%; When it contains a contributing metal active component, the mass ratio of the contributing metal active component to the metal in the main metal active component is 1:1-10.

6. The hydrogenation catalyst according to claim 5, characterized in that: Based on the catalyst by weight of 100%, The content of the main metal active component is 20~40wt%; When it contains a contributing metal active component, the mass ratio of the contributing metal active component to the metal in the main metal active component is 1:5-10.

7. The method for preparing the hydrogenation catalyst according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Boehmite was added to a nitrogen-containing polymer solution and reacted to obtain boehmite modified with nitrogen-containing polymer. (2) The nitrogen-containing polymer-modified boehmite is calcined under a protective atmosphere to obtain a carbon-modified alumina support; (3) The carbon-modified alumina support is contacted with the active component precursor solution, followed by post-treatment and calcination under a protective atmosphere to obtain the hydrogenation catalyst.

8. The method for preparing the hydrogenation catalyst according to claim 7, characterized in that: In step (1), the preparation method of the boehmite includes the following steps: (1-1) Add sodium aluminate solution dropwise to aluminum sulfate solution until alkaline, mix thoroughly, and obtain boehmite precursor; (1-2) The boehmite precursor is crystallized and then post-treated to obtain the boehmite.

9. The method for preparing the hydrogenation catalyst according to claim 8, characterized in that: Step (1-1) The concentration of aluminum ions in the sodium aluminate solution is 0.1-0.8 mol / L; The concentration of aluminum sulfate solution is 0.1-0.7 mol / L; The pH range corresponding to alkalinity is 8-11; The mixing method is stirring; and / or, Steps (1-2) The crystallization temperature is 50-120℃; The crystallization process takes 2-12 hours. Post-treatment methods include at least one of filtration and washing.

10. The method for preparing the hydrogenation catalyst according to claim 9, characterized in that: Step (1-1) The stirring time is 10-60 minutes; and / or, Steps (1-2) The crystallization process employs hydrothermal crystallization.

11. The method for preparing the hydrogenation catalyst according to claim 7, characterized in that: In step (1), The nitrogen-containing polymer is selected from one or a combination of polyvinylimidazolium, polyvinylpyrrolidone, or polyvinylpyridine; and / or, In the nitrogen-containing polymer solution, the solvent is selected from one or a combination of methanol or ethanol; and / or, The mass ratio of the boehmite to the nitrogen-containing polymer is 1~100:1; and / or, The reaction temperature is 100~120℃; and / or, The reaction time is 4 to 10 hours.

12. The method for preparing the hydrogenation catalyst according to claim 11, characterized in that: The concentration of the nitrogen-containing polymer solution is 0.1~2 wt%.

13. The method for preparing the hydrogenation catalyst according to claim 12, characterized in that: The concentration of the nitrogen-containing polymer solution is 0.6~1.8 wt%.

14. The method for preparing the hydrogenation catalyst according to claim 7, characterized in that: In step (2), The roasting temperature is 400~800℃; and / or, The roasting time is 2-10 hours; and / or, The protective atmosphere is selected from at least one of nitrogen atmosphere and inert atmosphere.

15. The method for preparing the hydrogenation catalyst according to claim 7, characterized in that: In step (3), the active component precursor solution includes a soluble metal salt of the main metal active component and, optionally, a soluble metal salt of the auxiliary metal active component.

16. The method for preparing the hydrogenation catalyst according to claim 15, characterized in that: When there is no soluble metal salt containing a supporting metal active component, the carbon-modified alumina support is first contacted with the precursor solution of the main metal active component once, followed by post-treatment and calcination under a protective atmosphere to obtain the primary calcined product or the catalyst. Optionally, the primary calcined product is contacted with the precursor solution of the main metal active component a second time, followed by post-treatment and calcination under a protective atmosphere to obtain the catalyst. or, When a soluble metal salt containing a contributing metal active component is used, the carbon-modified alumina support is first contacted once with a precursor solution of the main metal active component, followed by post-treatment and calcination under a protective atmosphere to obtain a primary calcined product. Then, the primary calcined product is contacted a second time with a precursor solution of the contributing metal active component, followed by post-treatment and calcination under a protective atmosphere to obtain the catalyst.

17. The method for preparing the hydrogenation catalyst according to claim 15, characterized in that: The soluble metal salt of the main metal active component is selected from the soluble nitrate of the main metal active component; and / or, The soluble metal salt of the auxiliary metal active component is selected from at least one of the soluble nitrate, soluble acetate, and soluble chloride salts of the auxiliary metal active component; and / or, The calculation is based on the sum of the mass of the metal element in the soluble metal salt of the main metal active component, the mass of the metal element in the soluble metal salt of the optionally auxiliary metal active component, and the mass of the carrier, which is 100%. The mass content of the metal element in the soluble metal salt of the main metal active component is 1~40wt%; When a metal-assisted active component is present, the mass ratio of the metal element in the soluble metal salt of the metal-assisted active component to the metal element in the soluble metal salt of the main metal active component in the precursor solution is 1:1-10.

18. The method for preparing the hydrogenation catalyst according to claim 17, characterized in that: The calculation is based on the sum of the mass of the metal element in the soluble metal salt of the main metal active component, the mass of the metal element in the soluble metal salt of the optionally auxiliary metal active component, and the mass of the carrier, which is 100%. The mass content of the metal element in the soluble metal salt of the main metal active component is 20~40 wt%; When a metal-assisted active component is present, the mass ratio of the metal element in the soluble metal salt of the metal-assisted active component to the metal element in the soluble metal salt of the main metal active component in the precursor solution is 1:5-10.

19. The method for preparing the hydrogenation catalyst according to claim 18, characterized in that: The concentration of the soluble metal salt of the main metal active component in the precursor solution is 20-66.7 wt%. The concentration of the soluble metal salt of the auxiliary metal active component in the precursor solution is 4-20 wt%.

20. The method for preparing the hydrogenation catalyst according to claim 16, characterized in that: In step (3), the methods of primary contact and secondary contact are each independently selected from at least one of immersion and spraying; The temperatures for the first and second contacts are each independently 15-40℃; and / or, The duration of the first and second contact is independently 10-60 minutes; and / or, The temperatures for the first and second firings are each independently 400-800℃; and / or, The initial and secondary roasting times are each 2-10 hours independently; and / or, Post-processing methods each independently include drying; and / or, The protective atmosphere is independently selected from at least one of nitrogen atmosphere and inert atmosphere.

21. A method for preparing ethanol by hydrogenation of ethyl acetate, characterized in that, Includes the following steps: Ethyl acetate and hydrogen are hydrogenated in the presence of a catalyst to prepare a product containing ethanol. The catalyst is the catalyst according to any one of claims 1-6 or the catalyst prepared by any one of claims 7-20.

22. The method for preparing ethanol by hydrogenation of ethyl acetate according to claim 21, characterized in that: The liquid hourly space velocity (LHSV) of ethyl acetate is 0.1–4 h⁻¹. -1 ; The molar ratio of hydrogen to ethyl acetate is (15-50):1; The temperature for hydrogenation reactions is 100-350℃; The pressure for the hydrogenation reaction is 1~5 MPa.

23. The method for preparing ethanol by hydrogenation of ethyl acetate according to claim 22, characterized in that: The liquid hourly space velocity (LHSV) of ethyl acetate is 0.1-2 h⁻¹. -1 ; The molar ratio of hydrogen to ethyl acetate is (20-40):1; The temperature for hydrogenation is 200-260℃; The pressure for the hydrogenation reaction is 2-4 MPa.

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