Copper-based catalyst, preparation method thereof and preparation method of 1, 4-butanediol

Abstract

The invention provides a copper-based catalyst, a preparation method of the copper-based catalyst and a preparation method of 1, 4-butanediol, and belongs to the technical field of catalysts. The copper-based catalyst is prepared by taking the copper salt and the iron salt as raw materials through the hydrothermal reaction, and the ratio of the amount of substance of the iron ions to the amount of substance of the copper ions is controlled, so that the copper-based catalyst has higher selectivity when the copper-based catalyst is used for preparing the 1, 4-butanediol through catalyzing the deep hydrogenation of the maleic anhydride. The result of the embodiment shows that the yield of the prepared copper-based catalyst can reach 92.7% when the copper-based catalyst is used for catalyzing deep hydrogenation of maleic anhydride to prepare 1, 4-butanediol, and the copper-based catalyst has good stability and can be repeatedly used.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts, and in particular relates to a copper-based catalyst and a preparation method thereof, and a preparation method of 1,4-butanediol. Background Art

[0002] With the increasing efforts in environmental protection, the demand for biodegradable plastics is growing. Therefore, the demand for 1,4-butanediol (BDO), a key upstream raw material for biodegradable plastics, has increased significantly.

[0003] Maleic anhydride, also known as maleic anhydride (MA), hydrogenation of MA and its derivatives is a method for preparing BDO. Maleic anhydride hydrogenation is divided into indirect hydrogenation and direct hydrogenation. Indirect hydrogenation is to first esterify maleic anhydride with alcohol, and then deeply hydrogenate the generated ester to obtain BDO. Direct hydrogenation of maleic anhydride refers to direct hydrogenation of maleic anhydride without esterification to obtain BDO. Direct deep hydrogenation of MA can convert it into BDO. However, there are side reactions such as parallel reactions and reversible reactions in the hydrogenation reaction of MA, which makes it very difficult to directly deeply hydrogenate MA to BDO. In current research, the hydrogenation reaction of MA is mostly focused on the production of succinic anhydride (SA) and γ-butyrolactone (GBL). However, there are relatively few reports on the direct hydrogenation of MA to prepare BDO, especially the use of non-precious metal copper-based catalysts. In the prior art, Cu-0.03Mo / SiO 2 The catalyst can achieve 100% MA conversion and 88.3% BDO selectivity at 200°C and 5MPa hydrogen pressure. However, the selectivity of the copper-based catalyst for direct deep hydrogenation of MA to obtain BDO still has a lot of room for improvement, so new catalysts still need to be developed to improve the performance in the deep hydrogenation of MA to BDO. Summary of the invention

[0004] The purpose of the present invention is to provide a copper-based catalyst and a preparation method thereof and a preparation method of 1,4-butanediol. The copper-based catalyst prepared by the present invention has higher selectivity when catalyzing the deep hydrogenation of maleic anhydride to prepare 1,4-butanediol.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a copper-based catalyst, comprising the following steps:

[0007] (1) mixing a copper salt, an iron salt, an ammonium salt and water to obtain a mixed solution; the molar ratio of the iron ions in the iron salt to the copper ions in the copper salt is (0.028-0.032):1;

[0008] (2) mixing the mixed solution obtained in step (1) with an alkali solution and a silicon source, and sequentially performing a hydrothermal reaction and calcining to obtain a precursor;

[0009] (3) Reducing the precursor obtained in step (2) to obtain a copper-based catalyst.

[0010] Preferably, in step (1), the mass ratio of copper salt to ammonium salt is (1.5-2):1.

[0011] Preferably, the pH value of the mixed solution and the alkali solution after mixing in step (2) is 9-12.

[0012] Preferably, the temperature of the hydrothermal reaction in step (2) is 180-200° C., and the time of the hydrothermal reaction is 45-50 h.

[0013] Preferably, the calcination temperature in step (2) is 400-500° C., and the calcination time is 3-5 hours.

[0014] Preferably, the reduction temperature in step (3) is 300-400° C., and the reduction time is 1-3 h.

[0015] The present invention also provides a copper-based catalyst prepared by the preparation method described in the above technical solution, comprising a silicon dioxide carrier and copper nanoparticles and iron oxides loaded on the surface of the silicon dioxide carrier.

[0016] The present invention also provides a method for preparing 1,4-butanediol, comprising:

[0017] A copper-based catalyst, maleic anhydride and a solvent are mixed, and hydrogen is introduced to carry out a hydrogenation reaction to obtain 1,4-butanediol; the copper-based catalyst is the copper-based catalyst described in the above technical solution.

[0018] Preferably, the mass ratio of the copper-based catalyst to maleic anhydride is (0.8-1.2):1.

[0019] Preferably, the temperature of the hydrogenation reaction is 185-195° C., the time of the hydrogenation reaction is 14-16 h, and the hydrogen pressure of the hydrogenation reaction is 5-7.5 MPa.

[0020] The present invention provides a method for preparing a copper-based catalyst, comprising the following steps: (1) mixing a copper salt, an iron salt, an ammonium salt and water to obtain a mixed solution; the molar ratio of the iron ions in the iron salt to the copper ions in the copper salt is (0.028-0.032):1; (2) mixing the mixed solution obtained in the step (1) with an alkali solution and a silicon source, and sequentially performing a hydrothermal reaction and calcination to obtain a precursor; (3) reducing the precursor obtained in the step (2) to obtain a copper-based catalyst. The present invention uses copper salt and iron salt as raw materials to prepare a copper-based catalyst through a hydrothermal reaction, and controls the molar ratio of the iron ions to the copper ions, so that the copper-based catalyst has a higher selectivity when catalyzing the deep hydrogenation of maleic anhydride to prepare 1,4-butanediol. The results of the examples show that when the copper-based catalyst prepared by the present invention catalyzes the deep hydrogenation of maleic anhydride to prepare 1,4-butanediol, the selectivity of 1,4-butanediol can reach 92.7% when the conversion rate is 100%, and the copper-based catalyst also has good stability and can be reused many times. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 XRD diagrams of the precursors prepared in Example 1 and Comparative Examples 1 to 3;

[0022] Figure 2 XRD diagrams of the copper-based catalysts prepared in Example 1 and Comparative Examples 1 to 3;

[0023] Figure 3 TEM image of the copper-based catalyst prepared in Example 1 and the particle size distribution of copper nanoparticles;

[0024] Figure 4 TEM image of the copper-based catalyst prepared in Comparative Example 1 and the particle size distribution of copper nanoparticles;

[0025] Figure 5 N of the precursor prepared in Example 1 and Comparative Example 1 2 Adsorption-desorption isotherms;

[0026] Figure 6 The pore size distribution curves of the precursors prepared in Example 1 and Comparative Example 1;

[0027] Figure 7 The XPS graphs of the copper-based catalysts prepared in Example 1 and Comparative Example 1;

[0028] Figure 8 Cu LMM spectra of the copper-based catalysts prepared in Example 1 and Comparative Example 1;

[0029] Fig. 9 The in-situ infrared spectra of CO adsorption of the precursors prepared in Example 1 and Comparative Example 1 after reduction at 350° C. for 1 h;

[0030] Fig.10 The NH 3 -TPD curve;

[0031] Fig.11 H of the precursor prepared in Example 1 and Comparative Example 1 2 -TPR curve;

[0032] Fig.12 The copper-based catalyst prepared in Example 1 was heated to 100 ℃ at different reaction temperatures (180 ℃, 190 ℃, 200 ℃, 210 ℃), 5 MPa H 2 The reaction results of generating BDO after 14 h of reaction under pressure;

[0033] Fig.13 The copper-based catalyst prepared in Example 1 was heated at 190°C and different H 2 The reaction results of generating BDO after 14 h of reaction under pressure (4 MPa, 5 MPa, 6 MPa);

[0034] Fig.14 The copper-based catalysts prepared in Example 1 and Comparative Examples 2 to 3 were heated at 190°C and 5 MPa H 2 The reaction results of generating BDO after 14 h of reaction under pressure;

[0035] Fig.15 The copper-based catalyst prepared in Example 1 was heated at 190°C and 5 MPa H 2 Kinetic curves of reaction under pressure at different times;

[0036] Fig.16 The copper-based catalyst prepared in Comparative Example 1 was heated at 190°C and 5 MPa H 2 Kinetic curves of reaction under pressure at different times;

[0037] Fig.17 is the reaction rate constant of the copper-based catalyst prepared in Example 1 when GBL is used as the substrate;

[0038] Fig.18 is the reaction rate constant of the copper-based catalyst prepared in Comparative Example 1 when GBL is used as the substrate;

[0039] Fig.19 This is a graph showing the reusability of the copper-based catalyst prepared in Example 1;

[0040] Fig. 20 This is a graph showing the reusability of the copper-based catalyst prepared in Comparative Example 1;

[0041] Fig.21 XRD patterns of the copper-based catalysts prepared in Example 1 and Comparative Example 1 after repeated use;

[0042] Fig. 22 The copper-based catalyst prepared in Comparative Example 1 was heated at different temperatures (180°C, 190°C, 200°C, 210°C), 5MPaH 2 The reaction results of BDO after 16 h of reaction under pressure;

[0043] Fig.23 The copper-based catalysts prepared in Comparative Examples 1 and 4-5 were heated at 190°C and 5 MPa H 2 The reaction results of generating BDO after 16 hours of reaction under pressure. DETAILED DESCRIPTION

[0044] The present invention provides a method for preparing a copper-based catalyst, comprising the following steps:

[0045] (1) mixing a copper salt, an iron salt, an ammonium salt and water to obtain a mixed solution; the molar ratio of the iron ions in the iron salt to the copper ions in the copper salt is (0.028-0.032):1;

[0046] (2) mixing the mixed solution obtained in step (1) with an alkali solution and a silicon source, and sequentially performing a hydrothermal reaction and calcining to obtain a precursor;

[0047] (3) Reducing the precursor obtained in step (2) to obtain a copper-based catalyst.

[0048] Unless otherwise specified, the present invention has no particular limitation on the sources of the raw materials, and commercially available products known to those skilled in the art may be used.

[0049] The invention mixes copper salt, iron salt, ammonium salt and water to obtain a mixed solution.

[0050] In the present invention, the copper salt preferably includes Cu(NO 3 ) 2 ·3H 2 O or cupric chloride.

[0051] In the present invention, the iron salt preferably includes Fe(NO 3 ) 3 9H 2 O or ferric chloride.

[0052] In the present invention, the molar ratio of the iron ions in the iron salt to the copper ions in the copper salt is (0.028-0.032):1. As an embodiment, the molar ratio of the iron ions in the iron salt to the copper ions in the copper salt may be specifically 0.028:1, 0.029:1, 0.030:1, 0.031:1 or 0.032:1. The present invention controls the molar ratio of the iron ions in the iron salt to the copper ions in the copper salt within the above range, which enables the copper-based catalyst to have higher selectivity when catalyzing the deep hydrogenation of maleic anhydride to prepare 1,4-butanediol.

[0053] In the present invention, the water is preferably deionized water.

[0054] In the present invention, the mass ratio of the copper salt to the volume of water is preferably (3-5) g:120 mL. As an embodiment, the mass ratio of the copper salt to the volume of water can be specifically 3 g:120 mL, 3.14 g:120 mL, 3.5 g:120 mL, 4 g:120 mL, 4.5 g:120 mL or 5 g:120 mL. The present invention controls the mass ratio of the copper salt to the volume of water within the above range, so that the raw material can be fully dissolved.

[0055] In the present invention, the ammonium salt preferably includes ammonium chloride, ammonium nitrate or ammonium sulfate. In the present invention, the ammonium salt is used to adjust the morphology of the catalyst.

[0056] In the present invention, the mass ratio of the copper salt to the ammonium salt is preferably (1.5-2):1, more preferably 1.76:1.

[0057] The present invention has no special limitation on the mixing operation of the copper salt, iron salt, ammonium salt and water, and the technical scheme of material mixing well known to those skilled in the art can be adopted.

[0058] After obtaining the mixed solution, the present invention mixes the mixed solution with an alkali solution and a silicon source, and sequentially performs hydrothermal reaction and calcination to obtain a precursor.

[0059] In the present invention, the alkali solution preferably includes ammonia water, sodium hydroxide or sodium carbonate, more preferably ammonia water. In the present invention, the alkali solution is used to adjust the pH value. The ammonia water in the present invention can form copper ammonia complex ions with copper salts, which is helpful for the interaction with the carrier, and has a better effect than other alkali solutions.

[0060] In the present invention, the pH value of the mixed solution and the alkali solution after mixing is preferably 9 to 12. As an embodiment, the pH value of the mixed solution and the alkali solution after mixing can be specifically 9, 9.5, 10, 10.5, 11, 11.5 or 12. The present invention controls the pH value of the mixed solution and the alkali solution after mixing within the above range, so that the subsequent silicon source can be hydrolyzed into silicon dioxide in the hydrothermal reaction.

[0061] When the alkali solution is aqueous ammonia, the mass concentration of the aqueous ammonia is preferably 20-30%, more preferably 25%; the volume ratio of the mass of the copper salt to the alkali solution is preferably (3-4) g:10 mL, more preferably 3.14 g:10 mL.

[0062] In the present invention, the silicon source preferably includes silica sol or silicon dioxide aerosol, and more preferably silica sol. The silica sol in the present invention is liquid and has better dispersibility for copper salt and iron salt.

[0063] In the present invention, the mass ratio of the copper salt to the silicon source is preferably (1-2): 1. As an embodiment, the mass ratio of the copper salt to the silicon source may be specifically 1: 1, 1.1: 1, 1.2: 1, 1.3: 1, 1.4: 1, 1.5: 1, 1.6: 1, 1.7: 1, 1.8: 1, 1.9: 1 or 2: 1. The present invention controls the mass ratio of the copper salt to the silicon source within the above range, which can control the loading amount of the active components in the prepared copper-based catalyst, and further improve the catalytic performance of the copper-based catalyst.

[0064] In the present invention, the mixing of the mixed solution with the alkali solution and the silicon source is preferably performed by: under stirring, adding the alkali solution dropwise to the mixed solution, and then slowly adding the silicon source after the alkali solution is added dropwise, and stirring at room temperature for 3 to 5 hours. The present invention has no special limitation on the operations of adding dropwise, slowly adding the silicon source and stirring, and a technical solution well known to those skilled in the art can be used.

[0065] In the present invention, the temperature of the hydrothermal reaction is preferably 180-200° C. As an embodiment, the temperature of the hydrothermal reaction may be specifically 180° C., 190° C. or 200° C.

[0066] In the present invention, the time of the hydrothermal reaction is preferably 45 to 50 hours. As an embodiment, the time of the hydrothermal reaction can be specifically 45 hours, 46 hours, 47 hours, 48 ​​hours, 49 hours or 50 hours. The present invention controls the temperature and time of the hydrothermal reaction within the above range, so that the hydrothermal reaction can be fully carried out.

[0067] After the hydrothermal reaction is completed, the product of the hydrothermal reaction is preferably filtered, washed and dried in sequence, and then calcined.

[0068] The present invention has no special limitation on the operations of filtration, washing and drying, and the technical solutions well known to those skilled in the art can be adopted.

[0069] In the present invention, the calcination temperature is preferably 400-500° C. As an embodiment, the calcination temperature may be specifically 400° C., 410° C., 420° C., 430° C., 440° C., 450° C., 460° C., 470° C., 480° C., 490° C. or 500° C.

[0070] In the present invention, the calcination time is preferably 3 to 5 hours. As an embodiment, the calcination time can be specifically 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours.

[0071] After obtaining the precursor, the present invention reduces the precursor to obtain a copper-based catalyst.

[0072] In the present invention, the reduction is preferably performed in a hydrogen atmosphere.

[0073] In the present invention, the flow rate of hydrogen during the reduction is preferably 40 to 60 mL / min. As an embodiment, the flow rate of hydrogen during the reduction can be specifically 40 mL / min, 45 mL / min, 50 mL / min, 55 mL / min or 60 mL / min.

[0074] In the present invention, the reduction temperature is preferably 300-400° C. As an embodiment, the reduction temperature may be specifically 300° C., 310° C., 320° C., 330° C., 340° C., 350° C., 360° C., 370° C., 380° C., 390° C. or 400° C.

[0075] In the present invention, the reduction time is preferably 1 to 3 hours. As an embodiment, the reduction time may be specifically 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours. In the present invention, during the reduction process, the copper precursor copper silicate or copper oxide is reduced to copper and cuprous oxide, and the iron oxide is not reduced at this temperature and still exists in the form of oxide. The present invention controls the various parameters during reduction within the above range, so that the reduction can be fully carried out.

[0076] The present invention uses copper salt and iron salt as raw materials to prepare a copper-based catalyst through a hydrothermal reaction, and controls the molar ratio of iron ions to copper ions and other preparation process parameters, so that the copper-based catalyst has higher selectivity when catalyzing the deep hydrogenation of maleic anhydride to prepare 1,4-butanediol.

[0077] The present invention also provides a copper-based catalyst prepared by the preparation method described in the above technical solution, comprising a silicon dioxide carrier and copper nanoparticles and iron oxides loaded on the surface of the silicon dioxide carrier.

[0078] In the present invention, the pore size of the copper-based catalyst is preferably 10 to 30 nm; the specific surface area of ​​the copper-based catalyst is preferably 200 to 300 m 2 / g; the average particle size of the copper nanoparticles in the copper-based catalyst is preferably 3-4.5 nm; the copper loading in the copper-based catalyst is preferably 30-40%; the total acid content of the copper-based catalyst is preferably 1-2 mmol / g, of which the weak acid content is preferably 0.4-0.6 mmol / g, and the medium-strong acid content is preferably 0.4-1.6 mmol / g.

[0079] In the present invention, the copper in the copper nanoparticles preferably comprises Cu + and Cu 0 ; The Cu 0 / (Cu + +Cu 0 ) (amount ratio of substance) is preferably 30 to 90%.

[0080] The copper-based catalyst prepared by the present invention has a smaller copper particle size, a higher specific surface area and a suitable Cu 0 / (Cu + +Cu 0 ) and acid amount, so that the copper-based catalyst has better catalytic performance and stability and can be reused.

[0081] The present invention also provides a method for preparing 1,4-butanediol, comprising:

[0082] A copper-based catalyst, maleic anhydride (MA) and a solvent are mixed, and hydrogen is introduced to carry out a hydrogenation reaction to obtain 1,4-butanediol; the copper-based catalyst is the copper-based catalyst described in the above technical solution.

[0083] In the present invention, the mass ratio of the copper-based catalyst to maleic anhydride is preferably (0.8-1.2): 1. As an embodiment, the mass ratio of the copper-based catalyst to maleic anhydride may be specifically 0.8:1, 0.9:1, 1:1, 1.1:1 or 1.2:1.

[0084] In the present invention, the solvent preferably includes 1,4-dioxane.

[0085] In the present invention, the mass ratio of the maleic anhydride to the volume ratio of the solvent is preferably 0.2g:(5-15)mL. As an embodiment, the mass ratio of the maleic anhydride to the volume ratio of the solvent can be specifically 0.2g:5mL, 0.2g:6mL, 0.2g:7mL, 0.2g:8mL, 0.2g:9mL, 0.2g:10mL, 0.2g:11mL, 0.2g:12mL, 0.2g:13mL, 0.2g:14mL or 0.2g:15mL.

[0086] In the present invention, the temperature of the hydrogenation reaction is preferably 185-195° C. As an embodiment, the temperature of the hydrogenation reaction may be specifically 185° C., 186° C., 187° C., 188° C., 189° C., 190° C., 191° C., 192° C., 193° C., 194° C. or 195° C.

[0087] In the present invention, the hydrogenation reaction time is preferably 14 to 16 hours. As an embodiment, the hydrogenation reaction time can be specifically 14 hours, 14.5 hours, 15 hours, 15.5 hours or 16 hours.

[0088] In the present invention, the hydrogenation reaction is preferably carried out under stirring conditions; the stirring speed is preferably 700 to 900 rpm, more preferably 800 rpm.

[0089] In the present invention, the hydrogen pressure of the hydrogenation reaction is preferably 5 to 7.5 MPa. As an embodiment, the hydrogen pressure of the hydrogenation reaction may be specifically 5 MPa, 5.5 MPa, 6 MPa, 6.5 MPa, 7 MPa or 7.5 MPa. The present invention controls the various parameters of the hydrogenation reaction within the above range, which can have better selectivity.

[0090] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0091] Sources of the substances in the examples: MA (Maclin, ≥ 99.0%), Cu (NO 3 ) 2 ·3H 2 O(Sinopharm, 99%), NH 4 Cl(Aladdin, 99.8%), Fe(NO 3 ) 3 9H 2 O(Sinopharm, 99%), NaOH(Sinopharm, 99%), NaCO 3 (Sinopharm, 99%), ammonia (Sinopharm, 25%-28%), and silica sol (Sigma-Aldrich, Ludox-HS, 40wt%) were purchased from commercial suppliers and used directly without any treatment. 1,4-Dioxane (≥99.0%) was purchased from Shanghai Runjie Chemical Reagent Co., Ltd. 2Gas (>99.999%) was purchased from Shanghai Pujiang Special Gas Co., Ltd.

[0092] Example 1

[0093] A method for preparing a copper-based catalyst: (1) 3.14 g Cu(NO 3 ) 2 ·3H 2 O, a certain amount of Fe(NO 3 ) 3 9H 2 O and 1.78 g ammonium chloride were dissolved in 120 mL deionized water. Fe(NO 3 ) 3 9H 2 O and Cu(NO 3 ) 2 ·3H 2 The molar ratio of copper ions in O is 0.03, Cu(NO 3 ) 2 ·3H 2 The mass ratio of O and ammonium chloride is 1.76:1 to obtain a mixed solution;

[0094] (2) Under stirring conditions, 10 mL of 25 wt% ammonia water was added dropwise to the mixed solution obtained in step (1), and after the addition was completed, 2.24 g of silica sol was slowly added, and the mixture was stirred at room temperature for 4 h. The obtained blue mixture was transferred to a high-pressure hydrothermal reactor lined with polytetrafluoroethylene, and the reaction was carried out at 190° C. for 48 h. The product after the reaction was filtered and washed, and the obtained solid was dried in a vacuum oven at 60° C. overnight, and then calcined at 450° C. for 4 h to obtain a precursor, which was recorded as Cu-0.03Fe / SiO 2 -MHT;

[0095] (3) The precursor obtained in step (2) was reduced at 350° C. in a hydrogen atmosphere for 2 h with a hydrogen flow rate of 50 mL / min, and then cooled to room temperature to obtain a copper-based catalyst.

[0096] Comparative Example 1

[0097] (1) 2.42 g Cu(NO 3 ) 2 ·3H 2 O and a certain amount of Fe(NO 3 ) 3 9H 2 O was dissolved in 30 mL of deionized water, Fe(NO 3 ) 3 9H 2 O and Cu(NO 3 ) 2·3H 2 The molar ratio of copper ions in O is 0.03, and a salt solution is obtained;

[0098] (2) Sodium hydroxide and sodium carbonate were dissolved in 30 mL of deionized water to obtain a mixed alkaline solution. The amount of hydroxide ions in the sodium hydroxide was about the same as that of Cu(NO 3 ) 2 ·3H 2 O and Fe(NO 3 ) 3 9H 2 The total molar ratio of copper ions to iron ions in sodium carbonate is 1.8:1, and the molar ratio of carbonate ions to Fe(NO 3 ) 3 9H 2 The molar ratio of iron ions in O is 2:1;

[0099] (3) Add 50 mL of deionized water to a 250 mL round-bottom flask and heat to 50° C., add 1.72 g of silica sol thereto, then drip the salt solution in step (1) and the mixed alkali solution in step (2) while stirring, maintain the pH value of the solution at 12, age at 50° C. for 5 h after the dripping is complete, filter, dry the obtained solid at 80° C. overnight, and then calcine at 450° C. for 4 h to obtain a precursor, recorded as Cu-0.03Fe / SiO 2 -CP;

[0100] (4) The precursor obtained in step (3) was reduced in a hydrogen atmosphere at 350° C. for 2 h with a hydrogen flow rate of 50 mL / min, and then cooled to room temperature to obtain a copper-based catalyst.

[0101] Comparative Example 2

[0102] In step (1) of Example 1, Fe(NO 3 ) 3 9H 2 O and Cu(NO 3 ) 2 ·3H 2 The molar ratio of copper ions in O was replaced by 0.02, and the other parameters were the same as those in Example 1 to obtain a copper-based catalyst, wherein the precursor was recorded as Cu-0.02Fe / SiO 2 -MHT.

[0103] Comparative Example 3

[0104] In step (1) of Example 1, Fe(NO 3 ) 3 9H 2 O and Cu(NO 3 ) 2 ·3H2 The molar ratio of copper ions in O was replaced by 0.04, and the other parameters were the same as those in Example 1 to obtain a copper-based catalyst, wherein the precursor was recorded as Cu-0.04Fe / SiO 2 -MHT.

[0105] Comparative Example 4

[0106] In step (1) of comparative example 1, Fe(NO 3 ) 3 9H 2 O and Cu(NO 3 ) 2 ·3H 2 The molar ratio of the copper ions in O was replaced by 0, and the other parameters were the same as those in Comparative Example 1 to obtain a copper-based catalyst, wherein the precursor was recorded as Cu-0Fe / SiO 2 -CP.

[0107] Comparative Example 5

[0108] In step (1) of comparative example 1, Fe(NO 3 ) 3 9H 2 O and Cu(NO 3 ) 2 ·3H 2 The molar ratio of copper ions in O was replaced by 0.04, and the other parameters were the same as those in Comparative Example 1 to obtain a copper-based catalyst, wherein the precursor was recorded as Cu-0.04Fe / SiO 2 -CP.

[0109] The powder diffractometer was Bruker D8 Advance. The XRD patterns of the samples were collected under Cu Kα radiation at 35 kV and 25 mA, with a scanning range (2θ) of 10° to 80° and a scanning speed of 20° / min. Figure 1 The XRD patterns of the copper-based catalysts prepared in Example 1 and Comparative Examples 1 to 3 are shown in Figure 2 As shown. Figure 1 It can be seen that the precursors in Example 1 and Comparative Examples 2-3 have obvious diffraction lines at 2θ=30.8°, 34.8°, 57.4° and 62.9°, which can be attributed to layered copper silicate. The precursor in Comparative Example 1 has obvious diffraction lines at 2θ=35.5°, 38.7°, 48.7°, 61.5°, 66.2° and 67.9°, which can be attributed to copper oxide. No FeO was detected. x The crystalline phase of FeO x The species is highly dispersed. Figure 2It can be seen that at 350℃ H 2 After reduction in the flow for 2 h, the catalysts in Example 1 and Comparative Example 1 both had obvious diffraction peaks at 2θ=36.7° and 61.8°, which we attributed to Cu 2 O, while the diffraction peaks at 2θ=43.3°, 50.5° and 74.2° are attributed to metal Cu. According to the Scherrer equation of the metal Cu diffraction line at 2θ=43.3°, we calculated the Cu particle size of the two catalysts (Table 1). The catalyst grains of Example 1 are smaller than those of Comparative Example 1, which will inevitably lead to differences in the performance of the two catalysts. In addition, by comparing the diffraction patterns of catalysts with different ratios, it is not difficult to find that the crystals of the catalyst with a ratio of 0.03 (Example 1) are smaller than those of catalysts with other ratios, which also explains why the reaction performance of the catalyst with a ratio of 0.03 is better than that of catalysts with other ratios.

[0110] Transmission electron microscopy (TEM) was performed using a FEI Tecnai G2-TF30 microscope at an accelerating voltage of 300 kV. The TEM image of the copper-based catalyst prepared in Example 1 and the particle size distribution of the copper nanoparticles are shown in FIG. Figure 3 As shown, the TEM image of the copper-based catalyst prepared in Comparative Example 1 and the particle size distribution of the copper nanoparticles are as follows Figure 4 As shown. Figure 3 and Figure 4 It can be seen that the copper-based catalyst prepared in Example 1 can obviously be seen to have a layered structure, which is consistent with the XRD result. The average particle size of the copper nanoparticles in the copper-based catalyst prepared in Example 1 is 4.3 nm, while the average particle size of the copper nanoparticles in the copper-based catalyst prepared in Comparative Example 1 is 12.1 nm, which is also consistent with the calculation result of the Scherrer equation.

[0111] The N of the precursors prepared in Example 1 and Comparative Example 1 was measured using a Quantachrome Autosorb-3B system in a liquid nitrogen environment. 2 Adsorption-desorption isotherms, the results are as follows Figure 5 The specific surface area of ​​the sample was calculated by applying the BET (Brunauer-Emmett-Teller) equation to the adsorption branch, and the pore size distribution curve was calculated by the BJH (Barrett-Joyner-Halenda) method. 2 The adsorption-desorption isotherms show that both catalysts have type IV isotherms, which indicates that there are mesopores in the catalysts. The pore size distribution curves of the precursors prepared in Example 1 and Comparative Example 1 are shown in FIG. Figure 6The pore size of the precursor prepared in Example 1 is in the range of 10 to 30 nm, while the pore size of the precursor prepared in Comparative Example 1 is in the range of 10 to 120 nm. In addition, the BET specific surface area of ​​the precursor prepared in Example 1 is 257.5 m 2 / g, which is significantly higher than the BET specific surface area of ​​100.3 m 2 / g.

[0112] XPS spectroscopy was used to characterize the surface electronic properties of the copper-based catalysts prepared in Example 1 and Comparative Example 1. The results are as follows: Figure 7 Before X-ray photoelectron spectroscopy (XPS) analysis, the precursors prepared in Example 1 and Comparative Example 1 were first subjected to H at 350°C on an XPS spectrometer. 2 The sample was subjected to in-situ reduction in an atmosphere for 2 h, and then XPS characterization of Cu in the sample was performed using a Thermo Fisher ESCALAB250Xi spectrometer with 1486.6 eV Al Kα radiation as the incident beam, where all binding energies (BEs) were calibrated using the C1s peak of 284.8 eV. Figure 7 It can be seen that the two catalysts have two obvious peaks at 932.65eV and 952.44eV, which are respectively attributed to Cu2p 3 / 2 and Cu 2p 1 / 2 . Due to Cu 0 and Cu + The binding energies are very similar, so in order to distinguish the two, we measured the CuLMM spectrum (e.g. Figure 8 After deconvolution, 918 eV of kinetic energy is attributed to Cu 0 , 916 eV of kinetic energy is attributed to Cu + According to the Cu LMM spectrum, 0 and Cu + The peak areas of the two catalysts were calculated. 0 / (Cu + +Cu 0 ) ratio, Cu of catalyst in Example 1 0 / (Cu + +Cu 0 ) is 0.45, and the Cu of the catalyst in Comparative Example 1 0 / (Cu + +Cu 0 ) is 0.89. The results show that the Cu + The proportion is significantly higher than that of the catalyst in Comparative Example 1.

[0113] The in-situ infrared spectroscopy characterization of CO adsorption was performed using an iS50 Fourier transform infrared spectrometer. The precursors prepared in Example 1 and Comparative Example 1 were first pressed into tablets and heated in an in-situ infrared cell at 350 °C for 1 hr. 2 Reduction for 1 h in N 2 The sample was then cooled to room temperature under a CO atmosphere and background spectra were collected. The sample was then kept under a CO atmosphere for 10 min and then heated with N 2 After purging for 30 minutes, the in-situ infrared spectra of CO adsorption were measured at room temperature. The in-situ infrared spectra of CO adsorption of the precursors prepared in Example 1 and Comparative Example 1 after reduction at 350°C for 1 hour are shown in FIG. Fig. 9 As shown. Fig. 9 It can be seen that Example 1 at 2120cm -1 An absorption peak appears around 100°, while Comparative Example 1 does not show an absorption peak. This is due to Cu 2+ Cu 0 The species interacts weakly with CO and easily disappears during the purge process, while Cu + The adsorption of CO is strong, and stable characteristic peaks can be shown. The characterization results also further confirm the analysis of the proportion of Cu species on the catalyst surface.

[0114] Using a Micromeritics AutoChem II chemical adsorption analyzer, 100 mg of the precursors prepared in Example 1 and Comparative Example 1 were first precipitated at 350° C. in a 10% (volume percentage) H 2 -Ar gas for 3 h, and then cooled to 60°C in He atmosphere. Maintaining 60°C, switch to 10% (volume percentage) NH 3 -He gas was used for 30 min to allow the sample to adsorb NH 3 to saturation, and then the temperature was raised to 100 °C to allow the gas phase and physically adsorbed NH 3 Then, the temperature was raised from 100°C to 800°C in a He atmosphere at a heating rate of 10°C / min and the NH 3 -TPD curve. NH 3 -TPD curve as Fig.10 As shown. Fig.10 It can be seen that both catalysts have NH 3 The desorption peaks, that is, weak acidity (100-200°C) and medium-strong acidity (200-400°C) are present. The total acid content of Example 1 is 1.33 mmol / g, while the total acid content of Comparative Example 1 is 0.68 mmol / g, and whether it is weak acid or medium-strong acid (Table 1), Example 1 is higher than Comparative Example 1.

[0115] 100 mg of the precursors prepared in Example 1 and Comparative Example 1 were first treated in a He atmosphere at 300° C. for 1 h using a Micromeritics AutoChem II chemical adsorption analyzer and a thermal conductivity detector (TCD). After cooling to room temperature, the precursors were heated in a 10% (volume percentage) H 2 The temperature was raised from 100°C to 800°C in Ar gas at a heating rate of 10°C / min. 2 -TPR curve, the results are as follows Fig.11 As shown. Fig.11 It can be seen that the precursor prepared in Example 1 has a hydrogen consumption peak at 208°C, and the precursor prepared in Comparative Example 1 has a hydrogen consumption peak at 224°C, which is attributed to the reduction of highly dispersed CuO to Cu 0 and the reduction of layered copper silicate to Cu 2 O, since the particles of the precursor prepared in Comparative Example 1 are relatively large, the temperature of its reduction peak is also higher. In addition, a relatively small hydrogen consumption peak can be observed at 307°C for the precursor prepared in Example 1, which is attributed to the well-dispersed Cu species and SiO 2 The reduction peak is generated by the strong interaction. This strong interaction is also beneficial to improving the stability and reusability of the catalyst. In addition, the actual hydrogen consumption of the two precursors per gram of Cu was calculated (Table 1). The amount of hydrogen required for the precursor prepared in Example 1 is 4.25mmol / g, and the actual hydrogen consumption per gram of Cu is 13.9mmol / g. The amount of hydrogen required for the precursor prepared in Comparative Example 1 is 3.33mmol / g, and the actual hydrogen consumption per gram of Cu is 9.51mmol / g. This may be because the existence form of layered copper silicate is more conducive to the reduction of copper species.

[0116] The precursors prepared in Example 1 and Comparative Example 1 and the parameters after being treated under different conditions are shown in Table 1.

[0117] Table 1 Precursors prepared in Example 1 and Comparative Example 1 and performance parameters after treatment under different conditions

[0118]

[0119] Table 1d cu Calculated by Scherrer equation; S BET 、V P , D P By N 2Physical adsorption determination; Cu loading was determined by ICP-OES analysis, where a small amount of sample was weighed and dissolved in aqua regia (0.1 g catalyst, 5 mL aqua regia) before the inductively coupled plasma atomic emission spectrometry (ICP-OES) test, transferred to a 50 mL volumetric flask and added with water to the scale line. The actual content of Cu and Fe was then determined using a ThermoElemental IRIS Intrepid II XSP inductively coupled plasma emission spectrometer; H 2 Consumption through H 2 -TRP analysis; acid content is determined by NH 3 - TPD analysis confirmed.

[0120] 0.2g of the copper-based catalyst prepared in Example 1 was placed in a quartz tube, 10mL of 1,4-dioxane was added, and the mixture was transferred to a 50mL stainless steel autoclave, and 0.2g of maleic anhydride was added. The autoclave was sealed and the air in the autoclave was replaced three times with hydrogen, and then hydrogen was introduced and pressurized to 5MPa. After the temperature reached the set value, the reaction was started at a stirring speed of 800rpm, and the reaction was stopped after a certain period of time. The product after the reaction was analyzed by TECHCOMP GC-7900Plus gas chromatography equipped with a flame ionization detector and a DM-5 capillary column (30m×0.32mm×1μm). The conversion rate of the reactants and the selectivity of the products were calculated by the correction normalization method.

[0121] The conversion rate and selectivity of the copper-based catalyst prepared in Example 1 at different temperatures and different times are shown in Table 2.

[0122] Table 2 Conversion rate and selectivity of the copper-based catalyst prepared in Example 1 at different temperatures and different times

[0123]

[0124] As can be seen from Table 2, at a reaction temperature of 200°C for 8h (Table 2, entry 1), a BDO selectivity of 65.8% was obtained, and the THF selectivity was 22.0%. It is speculated that this may be because the temperature is too high, resulting in partial dehydration of BDO to form THF. At 190°C for 8h (Table 2, entry 2), only a very small amount of BDO was generated, while the selectivity of GBL reached 94.8%. It is speculated that this is because the reaction time is too short and the reaction has not been completed. The reaction time was extended at 190°C (Table 2, entries 3 to 6). The experimental results show that the selectivity of BDO gradually increases with the extension of time. Under the conditions of 190°C and 14h, the selectivity of BDO reached a maximum of 92.7%. As the reaction time was further extended, the selectivity of BDO decreased slightly.

[0125] 0.2g of the copper-based catalyst prepared in Example 1 and Comparative Examples 2 to 3 was placed in a quartz tube, 10mL of 1,4-dioxane was added, and the mixture was transferred to a 50mL stainless steel autoclave, and 0.2g of maleic anhydride was added. The autoclave was sealed and the air in the autoclave was replaced three times with hydrogen, and then hydrogen was introduced and pressurized to a certain pressure. After the temperature reached the set value, the reaction was started at a stirring speed of 800rpm, and the reaction was stopped after 14h. The products after the reaction were analyzed by TECHCOMP GC-7900Plus gas chromatography equipped with a flame ionization detector and a DM-5 capillary column (30m×0.32mm×1μm). The conversion rate of the reactants and the selectivity of the products were calculated by the correction normalization method.

[0126] The copper-based catalyst prepared in Example 1 was heated to 200 °C at different reaction temperatures (180 °C, 190 °C, 200 °C, 210 °C) and 5 MPaH 2 The reaction results of BDO after 14 hours of reaction under pressure are as follows Fig.12 shown.

[0127] The copper-based catalyst prepared in Example 1 was heated at 190°C and different H 2 The reaction results of BDO after 14h of reaction under pressure (4MPa, 5MPa, 6MPa) are as follows Fig.13 shown.

[0128] The copper-based catalysts prepared in Example 1 and Comparative Examples 2-3 were heated at 190°C and 5 MPa H 2 The reaction results of BDO after 14 hours of reaction under pressure are as follows Fig.14 As shown. Figures 12-14 It can be seen that no BDO is generated after 14h of reaction at 180℃, which indicates that too low temperature is not conducive to the ring opening of GBL to generate BDO. In the process of increasing the reaction temperature from 190℃ to 210℃, the selectivity of BDO gradually decreased from 92.7% to 61.7%, while the selectivity of THF gradually increased from 6.3% to 29.8%, which indicates that at higher temperatures, BDO is more likely to dehydrate and cyclize to generate THF, which also verifies the previous speculation. However, regardless of the temperature, the conversion rate of MA reached 100% and SA was not detected in the product, indicating that the reaction temperature mainly affects the process of hydrogenation of GBL to BDO, and has little effect on the process of hydrogenation of MA to generate SA and the process of hydrogenation of SA to GBL. Therefore, the optimal reaction conditions for deep hydrogenation of MA to BDO were determined to be 190℃, 14h. Under the optimal reaction conditions, the catalyst prepared in Example 1 showed the best BDO selectivity of 92.7%. The increase or decrease of the Fe ratio would lead to the increase of EtOH and THF selectivity, while the selectivity of BDO was greatly reduced. This shows that the selectivity of Cu / SiO 2Doping an appropriate amount of Fe in the catalyst is beneficial to the formation of BDO.

[0129] 0.2g of the copper-based catalyst prepared in Example 1 and Comparative Example 1 was placed in a quartz tube, 10mL of 1,4-dioxane was added, and the mixture was transferred to a 50mL stainless steel autoclave, and 0.2g of maleic anhydride was added. The autoclave was sealed and the air in the autoclave was replaced three times with hydrogen, and then hydrogen was introduced and pressurized to 5MPa. After the temperature reached 190°C, the reaction was started at a stirring speed of 800rpm, and the reaction was stopped after different reaction times. The products after the reaction were analyzed by TECHCOMP GC-7900Plus gas chromatography equipped with a flame ionization detector and a DM-5 capillary column (30m×0.32mm×1μm). The conversion rate of the reactants and the selectivity of the products were calculated by the correction normalization method.

[0130] The copper-based catalysts prepared in Example 1 and Comparative Example 1 were heated to 190°C and 5 MPa H 2 The kinetic curves of the reaction under pressure at different times are as follows: Fig.15 and Fig.16 As shown. Fig.15 It can be seen from the kinetic curve of the copper-based catalyst prepared in Example 1 that the conversion of MA to SA is a rapid process, and MA has been completely converted to SA within 2 hours. The process of SA to GBL is relatively slow. When the reaction time is extended to 8 hours, SA is completely converted to GBL, and a small amount of BDO is generated at the same time. At this time, the selectivity of GBL reaches the highest. Continue to extend the reaction time, GBL will gradually convert into BDO, and the selectivity of BDO reaches a maximum value of 92.7% at 14 hours. As the reaction time continues to increase, BDO will dehydrate to form THF, resulting in a certain decrease in the selectivity of BDO. This kinetic result also further confirms the above-mentioned reaction pathway. And in Fig.16 It can be seen from the kinetic curve of the copper-based catalyst prepared in Comparative Example 1 that the selectivity of BDO reaches the maximum value of 94.4% after 16 hours, that is, to achieve a similar level of BDO selectivity, the time required for the catalyst of Example 1 is less than that of the catalyst of Comparative Example 1. From the comparison of the figures, it can be seen that the speed difference between the two is mainly concentrated in the process of converting GBL to BDO.

[0131] 0.2g of the copper-based catalyst prepared in Example 1 and Comparative Example 1 was placed in a quartz tube, 10mL of 1,4-dioxane was added, and the mixture was transferred to a 50mL stainless steel autoclave, and 0.2g of GBL was added. The autoclave was sealed and the air in the autoclave was replaced three times with hydrogen, and then hydrogen was introduced and pressurized to 5MPa. After the temperature reached 190°C, the reaction was started at a stirring speed of 800rpm, and the reaction was stopped after different reaction times. The products after the reaction were analyzed by TECHCOMP GC-7900Plus gas chromatography equipped with a flame ionization detector and a DM-5 capillary column (30m×0.32mm×1μm). The conversion rate of the reactants and the selectivity of the products were calculated by the correction normalization method.

[0132] When GBL is used as the substrate, the reaction rate constants of the copper-based catalysts prepared in Example 1 and Comparative Example 1 are as follows: Figures 17-18 As shown. Fig.17 and Fig.18 It can be seen that the reaction rate constant of the catalyst in Example 1 is 0.064 min -1 The reaction rate constant of the catalyst in comparative example 1 is 0.089 min -1 .

[0133] 0.2 g of the copper-based catalyst prepared in Example 1 and Comparative Example 1 was placed in a quartz tube, 10 mL of 1,4-dioxane was added, and the mixture was transferred to a 50 mL stainless steel autoclave. 0.2 g of maleic anhydride was added, the autoclave was sealed, and the air in the autoclave was replaced three times with hydrogen. Then, hydrogen was introduced and pressurized to 5 MPa. After the temperature reached 190°C, the reaction was started at a stirring speed of 800 rpm, and the reaction was stopped after 14 hours. The products after the reaction were analyzed by TECHCOMP GC-7900Plus gas chromatography equipped with a flame ionization detector and a DM-5 capillary column (30 m×0.32 mm×1 μm). The conversion rate of the reactants and the selectivity of the products were calculated by the correction normalization method. The same method was repeated several times. The reusability of the copper-based catalysts prepared in Example 1 and Comparative Example 1 is as follows: Figures 19-20 As shown. Fig.19 and Fig. 20 It can be seen that under the optimal conditions, the catalyst of Example 1 can be recycled at least 4 times, and the activity and BDO selectivity do not decrease significantly. At the same time, the product distribution does not change significantly during the cyclic experiment. However, the performance of the catalyst of Comparative Example 1 decreased significantly when it was used for the second time, and the BDO selectivity decreased to 14.4%, and GBL was the main product, indicating that the stability of the catalyst of Comparative Example 1 is not as good as that of the catalyst of Example 1.

[0134] The XRD patterns of the copper-based catalysts prepared in Example 1 and Comparative Example 1 after repeated use are as follows: Fig.21 shown.

[0135] 0.2g of the copper-based catalyst prepared in Comparative Examples 1 and 4-5 was placed in a quartz tube, 10mL of 1,4-dioxane was added, and the mixture was transferred to a 50mL stainless steel autoclave, and 0.2g of maleic anhydride was added. The autoclave was sealed and the air in the autoclave was replaced three times with hydrogen, and then hydrogen was introduced and pressurized to 5MPa. After the temperature reached the set temperature, the reaction was started at a stirring speed of 800rpm, and the reaction was stopped after 16h. The products after the reaction were analyzed by TECHCOMP GC-7900Plus gas chromatography equipped with a flame ionization detector and a DM-5 capillary column (30m×0.32mm×1μm). The conversion rate of the reactants and the selectivity of the products were calculated by the correction normalization method.

[0136] The copper-based catalyst prepared in Comparative Example 1 was heated to 200 °C at different temperatures (180 °C, 190 °C, 200 °C, 210 °C), 5 MPa H 2 The reaction results of BDO after 16 hours of reaction under pressure are as follows Fig. 22 shown.

[0137] The copper-based catalysts prepared in Comparative Examples 1 and 4-5 were heated at 190°C and 5 MPa H 2 The reaction results of BDO after 16 hours of reaction under pressure are as follows Fig.23 shown.

[0138] Based on the above results, the intrinsic correlation between catalyst structure and performance was explored. The copper particle size of the catalyst in Example 1 is smaller than that of the catalyst in Comparative Example 1, and the BET specific surface area is higher, which is more conducive to the reaction. 0 Can dissociate H 2 , Cu + Can adsorb and activate C=O, so the reaction requires a balanced Cu 0 / (Cu + +Cu 0 ) ratio. Compared with the catalyst in Comparative Example 1, the Cu + The proportion is relatively high, which means that the activation of the catalyst will be easier during the reaction, which can explain why the catalyst in Example 1 achieves a similar level of BDO selectivity faster than the catalyst in Comparative Example 1. In addition, GBL or BDO may undergo a side reaction of dehydration to produce THF during the reaction, and the strength of the catalyst acidity will have a certain impact on this. An increase in the amount of catalyst acid will intensify the dehydration reaction, resulting in an increase in THF selectivity. According to the above characterization results, the acidity of the catalyst in Example 1 is significantly higher than that of the catalyst in Comparative Example 1, so the THF selectivity of the catalyst in Example 1 is higher, and the BDO selectivity will be slightly lower than that of the catalyst in Comparative Example 1. And the well-dispersed Cu species in the catalyst in Example 1 and SiO2 The strong interaction also gives it better stability and reusability, allowing it to be recycled four times without significant performance degradation.

[0139] In summary, the copper-based catalyst was prepared by hydrothermal method. At 190℃ and 5MPa hydrogen pressure, the conversion rate of MA reached 100% and the BDO selectivity reached 92.7%. The catalyst required a shorter time to achieve a similar level of BDO selectivity. Through relevant characterization, it was found that the catalyst had a smaller copper particle size, a higher BET specific surface area, and a suitable Cu 0 / (Cu + +Cu 0 ) ratio and acid amount. In addition, the catalyst has better stability and reusability, and can be recycled 4 times without obvious performance degradation. The present invention provides a new idea for realizing the deep hydrogenation synthesis of MA into BDO using a non-precious metal catalyst.

[0140] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a copper-based catalyst, comprising the following steps: (1) mixing a copper salt, an iron salt, an ammonium salt and water to obtain a mixed solution; the molar ratio of the iron ions in the iron salt to the copper ions in the copper salt is (0.028-0.032):1; (2) mixing the mixed solution obtained in step (1) with an alkali solution and a silicon source, and sequentially performing a hydrothermal reaction and calcining to obtain a precursor; (3) Reducing the precursor obtained in step (2) to obtain a copper-based catalyst.

2. The preparation method according to claim 1, characterized in that: The mass ratio of the copper salt to the ammonium salt in the step (1) is (1.5-2):

1.

3. The preparation method according to claim 1, characterized in that: The pH value of the mixed solution and the alkali solution after mixing in the step (2) is 9-12.

4. The preparation method according to claim 1, characterized in that: The temperature of the hydrothermal reaction in step (2) is 180-200° C., and the time of the hydrothermal reaction is 45-50 hours.

5. The preparation method according to claim 1, characterized in that: In the step (2), the calcination temperature is 400-500° C., and the calcination time is 3-5 hours.

6. The preparation method according to claim 1, characterized in that: The reduction temperature in step (3) is 300-400° C., and the reduction time is 1-3 hours.

7. The copper-based catalyst prepared by the preparation method according to any one of claims 1 to 6 comprises a silica carrier and copper nanoparticles and iron oxides supported on the surface of the silica carrier.

8. A method for preparing 1,4-butanediol, comprising: A copper-based catalyst, maleic anhydride and a solvent are mixed, and hydrogen is introduced to carry out a hydrogenation reaction to obtain 1,4-butanediol; The copper-based catalyst is the copper-based catalyst according to claim 7.

9. The preparation method according to claim 8, characterized in that: The mass ratio of the copper-based catalyst to maleic anhydride is (0.8-1.2):

1.

10. The preparation method according to claim 8, characterized in that: The temperature of the hydrogenation reaction is 185-195° C., the time of the hydrogenation reaction is 14-16 hours, and the hydrogen pressure of the hydrogenation reaction is 5-7.5 MPa.

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