Hydrogenation catalyst, process for its preparation and use

Abstract

The application belongs to the technical field of hydrogenation catalysts, and discloses a hydrogenation catalyst, a preparation method and application thereof, the catalyst containing Cu nano-particles and a Zn(Al)O composite oxide carrier, the surface of the Cu nano-particles having crystal boundaries and existing a ZnOx coating layer, 0 The catalyst is used for preparing methanol by CO2 hydrogenation, has high conversion rate and selectivity at low temperature and low pressure, and can realize simultaneous improvement of the conversion rate and the selectivity. The catalyst is used for selective hydrogenation of butadiene, has low price, and has optimal conversion rate and selectivity, and stable performance.

Description

Technical Field

[0001] This invention belongs to the field of hydrogenation catalyst technology, specifically, it relates to a hydrogenation catalyst and its preparation method, as well as the application of the catalyst in CO2 hydrogenation to methanol and selective hydrogenation of butadiene. Background Technology

[0002] The CO2 hydrogenation to methanol reaction is one of the important ways to convert and utilize CO2. Methanol is a basic organic chemical raw material with a wide range of uses. It can be used to synthesize chemical products such as fibers, formaldehyde, plastics, pharmaceuticals, pesticides, dyes, and synthetic proteins. It can also be used as a liquid fuel for direct methanol fuel cells and improved diesel engines.

[0003] ZnO-Al2O3 oxide-supported Cu catalysts exhibit good selectivity and stability and have been industrially applied in the hydrogenation of CO2 to methanol. However, while high conversion rates can be achieved under high temperature and high pressure conditions, competition from CO generated by the reverse water-gas shift reaction exists, resulting in a seesaw effect between conversion and selectivity in methanol synthesis. Currently, commonly used catalysts for the hydrogenation of CO2 to methanol operate at reaction temperatures of approximately 250–350 °C and reaction pressures of approximately 6–8 MPa. Under low temperature and low pressure conditions, catalyst activity and selectivity decrease significantly. Therefore, it is essential to prepare catalysts that simultaneously improve CO2 conversion and methanol selectivity under low temperature and low pressure conditions.

[0004] In industrial applications, Pd-based catalysts are commonly used for the selective hydrogenation of naphtha cracking products to remove trace amounts of 1,3-butadiene. However, since the generated butene is further hydrogenated to butane, maximizing feedstock utilization is difficult. For example, patent document CN109092302B mentions Pd nanoparticles supported on an alumina support with a Pd loading of 0.5 wt%. Even when the 1,3-butadiene conversion approaches 100%, there is still a slight loss of the original 1-butene in the reaction gas. Pd-based monometallic catalysts have relatively poor stability, and the formation of hydrocarbon and carbon deposits during the reaction easily deactivates the catalyst. Therefore, a second metal is added to improve the butene selectivity of the supported Pd nanocatalyst. However, the reactivity decreases after the addition of a second metal. For example, patent document CN109092302B mentions that when PdLa (or PdCe, PdLaCe) nanoparticles are loaded on an alumina support, at 40°C, when 1,3-butadiene is almost completely converted, the original 1-butene in the reaction gas is also slightly lost by about 3%, and the selectivity improvement is very limited. The original 1-butene in the reaction gas is also hydrogenated.

[0005] Pd-based catalysts have been widely used in industrial C4 fraction selective hydrogenation processes, but their scarcity and high cost have become bottlenecks for large-scale application. Therefore, research teams are dedicated to developing non-precious metal-based catalysts to replace precious metal Pd-based catalysts. Summary of the Invention

[0006] Based on the above, the purpose of this invention is to provide a hydrogenation catalyst, its preparation method, and its application. This catalyst exhibits excellent CO2 conversion and methanol selectivity at low temperature and low pressure, and both CO2 conversion and methanol selectivity can be improved simultaneously. When used for selective hydrogenation of butadiene, this catalyst achieves high butadiene conversion and butene selectivity, and its performance is stable.

[0007] A first aspect of the present invention provides a hydrogenation catalyst comprising Cu nanoparticles and a Zn(Al)O composite oxide support, wherein the surface of the Cu nanoparticles has grain boundaries and a ZnOx coating layer, where 0 < x < 1.

[0008] A second aspect of the present invention provides a method for preparing the above-described hydrogenation catalyst, the method comprising:

[0009] 1) Preparation of catalyst precursor CuZnAl-LDHs;

[0010] 2) The catalyst was obtained by reducing CuZnAl-LDHs under a hydrogen atmosphere. The reduction conditions included heating to 400-460℃ at a rate of 1-5℃ / min, holding the temperature for 5-30min, and then immediately cooling down.

[0011] A third aspect of the present invention provides the application of the above-described catalyst in the hydrogenation of CO2 to methanol.

[0012] A fourth aspect of the invention provides the application of the above-described catalyst in the selective hydrogenation of butadiene.

[0013] Compared with the prior art, the advantages of the present invention are as follows:

[0014] 1. The catalyst of the present invention is used for the hydrogenation of CO2 to methanol. It has high conversion rate and selectivity at lower pressure and temperature, and can improve both conversion rate and selectivity at the same time, thereby achieving a high yield of methanol.

[0015] 2. The catalyst of the present invention is used for selective hydrogenation of butadiene. The catalyst is inexpensive and has excellent conversion and selectivity, and its performance is stable.

[0016] 3. The catalyst of the present invention can be obtained by direct reduction of the hydrotalcite precursor. The preparation method is simple. By utilizing the different chemical microenvironments of the active metals in the hydrotalcite layers to induce surface defects of nanoparticles, a supported catalyst with grain boundaries and ZnOx coating layers on the surface of Cu nanoparticles can be obtained.

[0017] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0018] Figure 1 Butadiene conversion rate of each catalyst at different temperatures.

[0019] Figure 2 Butadiene conversion and corresponding butadiene selectivity for each catalyst. Detailed Implementation

[0020] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0021] According to a first aspect of the present invention, a hydrogenation catalyst is provided, the catalyst comprising Cu nanoparticles and a Zn(Al)O composite oxide support, wherein the surface of the Cu nanoparticles has grain boundaries and a ZnOx coating layer, 0 < x < 1.

[0022] In this invention, based on the total weight of the catalyst, the loading of Cu nanoparticles can be 8.0–30.0 wt%, preferably 10.0–25.0 wt%.

[0023] According to the present invention, the particle size of the Cu nanoparticles can be 2-8 nm, preferably 3-5 nm.

[0024] In this invention, XPS detection confirmed that ZnOx is a mixture, where 0 < x < 1.

[0025] According to a second aspect of the present invention, the present invention provides a method for preparing the above-described hydrogenation catalyst, the method comprising:

[0026] 1) Preparation of catalyst precursor CuZnAl-LDHs;

[0027] 2) The catalyst was obtained by reducing CuZnAl-LDHs under a hydrogen atmosphere. The reduction conditions included heating to 400-460℃ at a rate of 1-5℃ / min, holding the temperature for 5-30min, and then immediately cooling down.

[0028] In this invention, the CuZnAl-LDHs can be prepared using conventional methods in the prior art, such as a constant pH method, specifically including the following steps:

[0029] (1) Cu 2+ Zn 2+ Al 3+ Prepare a salt solution and prepare an alkaline solution from Na2CO3 and NaOH. Add the salt solution and alkaline solution dropwise to a stirred reaction vessel, controlling the pH of the reaction solution to be 9.5±0.2. After the salt solution is added, crystallize the reaction solution at a constant temperature of 60-80℃ for 10-30 hours.

[0030] (2) The reaction product was filtered, washed with deionized water, and dried to obtain CuZnAl-LDHs.

[0031] Other specific parameters in the above steps can be selected with reference to existing technologies. To obtain CuZnAl-LDHs with better crystal structure, preferably, in the salt solution, (Cu...) 2+ +Zn 2+ )∶Al 3+ The molar ratio of Cu is 3:1. 2+ ∶Zn 2+ The molar ratio of Cu is 1:1-10. 2+ Zn 2+ And Al 3+ The total molar concentration is 0.1-1 mol / L.

[0032] Preferably, in the alkaline solution, the molar concentration of Na2CO3 can be 0.05-0.5 mol / L and the molar concentration of NaOH can be 0.1-0.8 mol / L.

[0033] According to the present invention, the stirring speed, drying temperature, etc. of the reaction vessel can be conventionally selected, such as the stirring speed being 200-600 r / min and the drying temperature being 60-80℃.

[0034] According to a third aspect of the present invention, the present invention provides the application of the above-described catalyst in the production of methanol by CO2 hydrogenation.

[0035] According to the present invention, the reaction conditions for the hydrogenation of CO2 to methanol include: a reaction temperature of 150–240°C; a reaction pressure of 1.5–2.5 MPa; a feed composition of CO2∶H2∶Ar = 15–20∶65–75∶4 by volume; and a volume hourly space velocity of 3000–8000 h⁻¹. -1 The catalyst dosage is 0.50-2.0g.

[0036] According to a fourth aspect of the invention, the present invention provides the application of the above-described catalyst in the selective hydrogenation of butadiene.

[0037] According to the present invention, the reaction conditions for selective hydrogenation of butadiene include: a reaction temperature of 20–150°C;

[0038] The reaction pressure was 0.1 MPa; the feed composition, by volume ratio, was butadiene:hydrogen:argon = 1:3–8:40–50; the volume hourly space velocity was 3000–8000 h⁻¹. -1 The catalyst dosage is 0.10-2.0g.

[0039] In this invention, whether it is the reaction of CO2 hydrogenation to methanol or the selective hydrogenation of butadiene, the catalyst is pre-reduced before use. The pre-reduction conditions include: reduction at 250-350℃ for 0.5-1h in a hydrogen atmosphere.

[0040] The substances and parameters not limited in this invention can be selected according to existing technology, which is a conventional technical means in this field.

[0041] The present invention will be further described below with reference to embodiments. However, the invention is not limited to these embodiments.

[0042] Example 1

[0043] Step A: Accurately weigh 15 mmol Cu(NO3)2·3H2O, 52.5 mmol Zn(NO3)2·6H2O, and 22.5 mmol Al(NO3)3·9H2O, and place them in a beaker containing 200 mL of deionized water. Stir until completely dissolved to obtain a salt solution. Weigh 45 mmol Na2CO3 and 126 mmol NaOH and place them in a beaker containing 200 mL of deionized water. Stir until completely dissolved to obtain an alkaline solution. Place 200 mL of deionized water in a 1000 mL four-necked flask. Stir at 300 rpm at room temperature, and add the salt and alkaline solutions dropwise to the four-necked flask, controlling the pH value to 9.5. After the salt solution has been completely added, crystallize at 65 °C in a water bath for 24 h. Obtain the solid sample by vacuum filtration, wash with deionized water, dry in a 70 °C oven, grind to obtain Cu2Zn7Al3-LDHs powder, and store it dry.

[0044] Step B: The Cu2Zn7Al3-LDHs prepared above were reduced under a hydrogen atmosphere. The reduction program was as follows: the temperature was increased from room temperature to 450℃ at a heating rate of 2℃ / min, held at this temperature for 10 min, and then immediately cooled to obtain the supported Cu nanoparticle catalyst 11.2ZnO. x / Cu-Zn(Al)O.

[0045] ICP analysis showed that the actual loading of Cu nanoparticles in the catalyst was 11.2 wt%. Transmission electron microscopy revealed that the surface of the Cu nanoparticles had two grain boundaries and a ZnOx coating layer. The particle size of the Cu nanoparticles was 3.7 nm.

[0046] Example 2

[0047] Step A: Accurately weigh 22.5 mmol Cu(NO3)2·3H2O, 45.0 mmol Zn(NO3)2·6H2O, and 22.5 mmol Al(NO3)3·9H2O, and place them in a beaker containing 200 mL of deionized water. Stir until completely dissolved to obtain a salt solution. Weigh 45 mmol Na2CO3 and 126 mmol NaOH and place them in a beaker containing 200 mL of deionized water. Stir until completely dissolved to obtain an alkaline solution. Place 200 mL of deionized water in a 1000 mL four-necked flask. Stir at 300 rpm at room temperature, and add the salt and alkaline solutions dropwise to the four-necked flask, controlling the pH value to 9.5. After the salt solution has been completely added, crystallize at 65 °C in a water bath for 24 h. Obtain the solid sample by vacuum filtration, wash with deionized water, dry in a 70 °C oven, grind to obtain Cu3Zn6Al3-LDHs powder, and store it dry.

[0048] Step B: The Cu3Zn6Al3-LDHs obtained above were reduced under a hydrogen atmosphere. The reduction procedure was as follows: the temperature was increased from room temperature to 450℃ at a heating rate of 2℃ / min, held at this temperature for 10 min, and then immediately cooled to obtain the supported Cu nanoparticle catalyst 16.8ZnO. x / Cu-Zn(Al)O.

[0049] ICP analysis showed that the actual loading of Cu nanoparticles in the catalyst was 16.8 wt%. Transmission electron microscopy revealed that the surface of the Cu nanoparticles had three grain boundaries and a ZnOx coating layer. The particle size of the Cu nanoparticles was 4.2 nm.

[0050] Example 3

[0051] Step A: Accurately weigh 30.0 mmol Cu(NO3)2·3H2O, 37.5 mmol Zn(NO3)2·6H2O, and 22.5 mmol Al(NO3)3·9H2O, and place them in a beaker containing 200 mL of deionized water. Stir until completely dissolved to obtain a salt solution. Weigh 45 mmol Na2CO3 and 126 mmol NaOH and place them in a beaker containing 200 mL of deionized water. Stir until completely dissolved to obtain an alkaline solution. Place 200 mL of deionized water in a 1000 mL four-necked flask. Stir at 300 rpm at room temperature, and add the salt and alkaline solutions dropwise to the four-necked flask, controlling the pH value to 9.5. After the salt solution has been completely added, crystallize at 65 °C in a water bath for 24 h. Obtain the solid sample by vacuum filtration, wash with deionized water, dry in a 70 °C oven, grind to obtain Cu4Zn5Al3-LDHs powder, and store it dry.

[0052] Step B: The Cu4Zn5Al3-LDHs prepared above were reduced under a hydrogen atmosphere. The reduction program was as follows: the temperature was increased from room temperature to 450℃ at a heating rate of 2℃ / min, held at this temperature for 10 min, and then immediately cooled to obtain Cu nanoparticle catalyst 25.0ZnO. x / Cu-Zn(Al)O.

[0053] ICP analysis showed that the actual loading of Cu nanoparticles in the catalyst was 25.0 wt%. Transmission electron microscopy revealed that the surface of the Cu nanoparticles had five grain boundaries and a ZnOx coating layer, and the particle size of the Cu nanoparticles was 4.5 nm.

[0054] Comparative Example 1

[0055] Step A: Same as Example 1.

[0056] Step B: The prepared Cu2Zn7Al3-LDHs were reduced in a hydrogen atmosphere. The reduction procedure was as follows: the temperature was increased from room temperature to 500℃ at a heating rate of 2℃ / min, held for 10min, and then immediately cooled to obtain the supported Cu nanoparticle catalyst 11.2Cu-Zn(Al)O.

[0057] The catalyst has an actual Cu nanoparticle loading of 11.2 wt%, and the Cu nanoparticles have two grain boundaries on their surface but no ZnOx coating layer. The Cu nanoparticles have a particle size of 3.8 nm.

[0058] Comparative Example 2

[0059] Step A: Same as Example 2.

[0060] Step B: The prepared Cu3Zn6Al3-LDHs were reduced in a hydrogen atmosphere. The reduction procedure was as follows: the temperature was increased from room temperature to 500℃ at a heating rate of 2℃ / min, held for 10min, and then immediately cooled to obtain the supported Cu nanoparticle catalyst 16.8Cu-Zn(Al)O.

[0061] The catalyst has an actual Cu nanoparticle loading of 16.8 wt%, and the Cu nanoparticles have three grain boundaries on their surface but no ZnOx coating layer. The Cu nanoparticles have a particle size of 4.2 nm.

[0062] Comparative Example 3

[0063] Step A: Same as Example 3.

[0064] Step B: The prepared Cu4Zn5Al3-LDHs were reduced under a hydrogen atmosphere. The reduction procedure was as follows: the temperature was increased from room temperature to 500℃ at a heating rate of 2℃ / min, held for 10min and then immediately cooled to obtain the supported Cu nanoparticle catalyst 25.0Cu-Zn(Al)O.

[0065] The catalyst has an actual loading of 25.0 wt% Cu nanoparticles. The surface of the Cu nanoparticles has five grain boundaries but no ZnOx coating layer. The particle size of the Cu nanoparticles is 4.6 nm.

[0066] Comparative Example 4

[0067] Step A: Accurately weigh 67.5 mmol Zn(NO3)2·6H2O and 22.5 mmol Al(NO3)3·9H2O, place them in a beaker containing 200 mL of deionized water, and stir until completely dissolved to obtain a salt solution. Weigh 45 mmol Na2CO3 and 126 mmol NaOH, place them in a beaker containing 200 mL of deionized water, and stir until completely dissolved to obtain an alkaline solution. Place 200 mL of deionized water in a 1000 mL four-necked flask. Stir at 300 rpm at room temperature, and add the salt and alkaline solutions dropwise to the four-necked flask, controlling the pH value to 9.5. After the salt solution has been completely added, crystallize at 65 °C in a water bath for 24 h. Obtain the solid sample by vacuum filtration, wash with deionized water, dry in a 70 °C oven, grind to obtain ZnAl-LDHs powder, and store in a dry place.

[0068] Step B: Immerse an equal volume of Cu(NO3)3·3H2O aqueous solution (concentration of 24wt%) in a round-bottom flask containing the ZnAl-LDHs prepared in step (A), shake until homogeneous, shake for 30 min, and dry at 120℃ for 2 h to obtain Cu / ZnAl-LDHs.

[0069] Step C: The Cu / ZnAl-LDHs prepared above were reduced in a hydrogen atmosphere. The reduction procedure was as follows: the temperature was increased from room temperature to 450℃ at a heating rate of 2℃ / min, held for 10min, and then immediately cooled to obtain the supported Cu nanoparticle catalyst 24.8Cu / Zn(Al)O.

[0070] The actual loading of Cu nanoparticles in the catalyst is 24.8 wt%. There are no grain boundaries or ZnOx coating on the surface of the Cu nanoparticles, and the particle size of the Cu nanoparticles is 4.7 nm.

[0071] The catalysts prepared in the various examples and comparative examples were compressed into 20-40 mesh granular catalysts. These granular catalysts were then loaded into a fixed-bed reactor and pretreated with H2 at a flow rate of 30 mL / min / g for 0.5 h at 300 °C. After cooling to 200 °C, the reaction feed was introduced to initiate the catalytic reaction at a pressure of 2.0 MPa. The volume ratio of the reaction feed was CO2:H2:Ar = 24:72:4, the flow rate was 100 mL / min, and the volume hourly space velocity (GHSV) was 6000 h⁻¹. -1 The catalyst dosage was 1.0 g. The reaction tail gas was fed into a gas chromatograph for quantitative analysis. The conversion rate of CO2 and the selectivity of CH3OH were calculated. The specific catalytic performance of the reaction is shown in Table 1.

[0072] Table 1

[0073]

[0074] As shown in Table 1, using the catalyst of this application, the conversion rate and selectivity of CO2 hydrogenation to methanol under low temperature and low pressure are higher, and the conversion rate and selectivity can be improved at the same time.

[0075] The catalysts prepared in the various examples and comparative examples were compressed into 20-40 mesh granular catalysts. These granular catalysts were then loaded into a fixed-bed reactor and pretreated with H2 at a flow rate of 30 mL / min / g for 0.5 h at 300 °C. After cooling to room temperature (20 °C), the reaction feed was introduced to initiate the catalytic reaction at an atmospheric pressure of 0.1 MPa. The composition of the reaction feed was 1,3-butadiene:H2:Ar = 2:10:88; the flow rate was 50 mL / min; and the volumetric hourly space velocity (GHSV) was 6000 h⁻¹. -1 The catalyst dosage was 0.25 g. The conversion rate and selectivity of butadiene were determined at different reaction temperatures. The reaction tail gas was fed into a gas chromatograph for quantitative analysis. The conversion rate and selectivity of butadiene, and the catalytic performance of the 1,3-butadiene hydrogenation reaction were analyzed. Figure 1 , Figure 2 As shown.

[0076] Depend on Figure 1 , Figure 2 It is known that the catalyst of this application can achieve a conversion rate of 100% for the selective hydrogenation of butadiene at a low reaction temperature of 0.1 MPa, and also has high butene selectivity and stability.

[0077] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. Use of a catalyst in the production of methanol by the hydrogenation of CO2, characterized in that, The catalyst contains Cu nanoparticles and a Zn(Al)O composite oxide support, the surface of the Cu nanoparticles has grain boundaries and ZnO is present x cladding layer, 0 < x < 1; The preparation method of the catalyst comprises: 1) preparing a catalyst precursor CuZnAl-LDHs; 2) reducing the CuZnAl-LDHs under a hydrogen atmosphere to obtain the catalyst, and the reduction conditions comprise: increasing the temperature to 400-460°C at a rate of 1-5°C / min, keeping the temperature constant for 5-30 min, and then immediately reducing the temperature.

2. Use of the catalyst according to claim 1 for the production of methanol by the hydrogenation of CO2, wherein, The loading amount of the Cu nanoparticles is 8.0-30.0 wt% based on the total weight of the catalyst.

3. Use of the catalyst according to claim 2 for the production of methanol by the hydrogenation of CO2, wherein, The loading amount of the Cu nanoparticles is 10.0-25.0 wt% based on the total weight of the catalyst.

4. Use of the catalyst according to claim 1 for the production of methanol by the hydrogenation of CO2, wherein, The particle size of the Cu nanoparticles is 2-8 nm.

5. Use of a catalyst according to claim 4 for the production of methanol by the hydrogenation of CO2, wherein, The particle size of the Cu nanoparticles is 3-5 nm.

6. Use of the catalyst according to claim 1 for the production of methanol by the hydrogenation of CO2, wherein, The CuZnAl-LDHs are prepared by a constant-pH method, which comprises the following steps: (1) Cu 2+ , Zn 2+ , Al 3+ are made into salt solution, Na2CO3, NaOH are made into alkali solution; the salt solution, alkali solution are added dropwise into the stirred reaction container, the pH of the reaction liquid is controlled at 9.5±0.2, after the salt solution is added dropwise, the reaction liquid is crystallized at 60-80℃ for 10-30h; (2) suction-filtering the reaction product, washing with deionized water, and drying to obtain the CuZnAl-LDHs.

7. Use of a catalyst according to claim 6 for the production of methanol by the hydrogenation of CO2, wherein, The molar ratio of Cu 2+ +Zn 2+ )∶Al 3+ = 3∶1, the molar ratio of Cu 2+ ∶Zn 2+ = 1∶1-10, and the total molar concentration of Cu 2+ , Zn 2+ and Al 3+ is 0.1-1 mol / L.

8. Use of the catalyst according to claim 6 for the production of methanol by the hydrogenation of CO2, wherein, In the alkaline solution, the molar concentration of Na2CO3 is 0.05-0.5 mol / L, and the molar concentration of NaOH is 0.1-0.8 mol / L.

9. Use of the catalyst according to claim 1 for the production of methanol by the hydrogenation of CO2, wherein, The reaction conditions for the methanol production by CO2 hydrogenation include: reaction temperature of 150-240℃; reaction pressure of 1.5-2.5 MPa; reaction feed composition of CO2:H2:Ar = 15-20:65-75:4 by volume ratio; volume space velocity of 3000-8000 h -1 , and catalyst dosage of 0.50-2.0 g.

10. Use of the catalyst according to claim 1 for the production of methanol by the hydrogenation of CO2, wherein, The catalyst is used after pre-reduction, and the pre-reduction conditions comprise: reducing at 250-350°C for 0.5-1 h under a hydrogen atmosphere.

11. Use of a catalyst for the selective hydrogenation of butadiene, characterized in that, The catalyst contains Cu nanoparticles and a Zn(Al)O composite oxide support, the surface of the Cu nanoparticles has grain boundaries and ZnO is present x cladding layer, 0 < x < 1; The preparation method of the catalyst comprises: 1) preparing a catalyst precursor CuZnAl-LDHs; 2) reducing the CuZnAl-LDHs under a hydrogen atmosphere to obtain the catalyst, and the reduction conditions comprise: increasing the temperature to 400-460°C at a rate of 1-5°C / min, keeping the temperature constant for 5-30 min, and then immediately reducing the temperature.

12. Use of a catalyst according to claim 11 for the selective hydrogenation of butadiene, wherein, The loading amount of the Cu nanoparticles is 8.0-30.0 wt% based on the total weight of the catalyst.

13. Use of a catalyst according to claim 12 for the selective hydrogenation of butadiene, wherein, The loading amount of the Cu nanoparticles is 10.0-25.0 wt% based on the total weight of the catalyst.

14. Use of a catalyst according to claim 11 for the selective hydrogenation of butadiene, wherein, The particle size of the Cu nanoparticles is 2-8 nm.

15. Use of a catalyst according to claim 14 for the selective hydrogenation of butadiene, wherein, The particle size of the Cu nanoparticles is 3-5 nm.

16. Use of the catalyst according to claim 11 for the selective hydrogenation of butadiene, wherein, The CuZnAl-LDHs are prepared by a constant-pH method, which comprises the following steps: (1) Cu 2+ , Zn 2+ , Al 3+ are made into salt solution, Na2CO3, NaOH are made into alkali solution; the salt solution, alkali solution are added dropwise into the stirred reaction container, the pH of the reaction liquid is controlled at 9.5±0.2, after the salt solution is added dropwise, the reaction liquid is crystallized at 60-80℃ for 10-30h; (2) suction-filtering the reaction product, washing with deionized water, and drying to obtain the CuZnAl-LDHs.

17. Use of a catalyst according to claim 16 for the selective hydrogenation of butadiene, wherein, The molar ratio of Cu 2+ +Zn 2+ )∶Al 3+ = 3∶1, the molar ratio of Cu 2+ ∶Zn 2+ = 1∶1-10, and the total molar concentration of Cu 2+ , Zn 2+ and Al 3+ is 0.1-1 mol / L.

18. Use of a catalyst according to claim 16 for the selective hydrogenation of butadiene, wherein, In the alkaline solution, the molar concentration of Na2CO3 is 0.05-0.5 mol / L, and the molar concentration of NaOH is 0.1-0.8 mol / L.

19. Use of the catalyst according to claim 11 for the selective hydrogenation of butadiene, wherein, The reaction conditions for selective hydrogenation of butadiene include a reaction temperature of 20-150°C, a reaction pressure of 0.1 MPa, a reaction feed composition of butadiene:hydrogen:argon = 1:3-8:40-50 by volume, a volume space velocity of 3000-8000 h -1 , and a catalyst dosage of 0.10-2.0 g.

20. Use of the catalyst according to claim 11 for the selective hydrogenation of butadiene, wherein, The catalyst is used after pre-reduction, and the pre-reduction conditions comprise: reducing at 250-350°C for 0.5-1 h under a hydrogen atmosphere.

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