Copper-nickel monatomic catalyst based on MXene carrier as well as preparation method and application of copper-nickel monatomic catalyst

Abstract

The invention discloses a copper-nickel monatomic catalyst based on an MXene carrier and a preparation method and application thereof, and belongs to the technical field of catalysts.The copper-nickel monatomic catalyst comprises the MXene carrier, a copper-nickel monatomic active component is loaded on the MXene carrier, and the MXene carrier is coated with a nitrogen-doped carbon layer; wherein the content of the copper-nickel monatomic active component is 0.2-1.5 wt%, and the molar ratio of copper to nickel in the copper-nickel monatomic active component is (1: 0.3)-(1: 1.2); and the content of the nitrogen-doped carbon coating layer is 7-10 wt%. The copper-nickel monatomic catalyst does not contain toxic chromium metal, an MXene / copper-nickel monatomic / nitrogen-doped carbon layer ternary composite system is adopted, a few-layer MXene carrier provides rich surface active sites, copper-nickel monatomic active components are anchored through chemical adsorption, a dehydrogenation active center of copper atoms and a cyclization active center of nickel atoms have a synergistic effect, and the catalytic activity of the copper-nickel monatomic catalyst is improved. The oxidation resistance and the stability of the catalyst are remarkably improved through coating of the nitrogen-doped carbon layer, the technical bottlenecks of low activity, short service life and heavy pollution of a traditional catalyst are overcome, and an efficient solution is provided for green synthesis of lactone.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts. More specifically, the present invention relates to a copper-nickel single-atom catalyst based on an MXene support, and a preparation method and application thereof. Background Art

[0002] Lactones refer to cyclic esters with the functional group -COO-. They are an important class of organic compounds and intermediates, and are widely used in the fields of medicine, pesticides, and polymer materials. The chemical synthesis methods of lactones mainly include catalytic dehydrogenation of diols, hydrogenation of maleic anhydride, direct cyclization of unsaturated acids, Baeyer-Villiger oxidation, and intramolecular esterification. Among them, the catalytic dehydrogenation method of diols has become a lactone synthesis method with industrial production value due to its advantages such as simple process, mild reaction conditions, and easy separation of by-products.

[0003] Kangnian et al. prepared a series of SnO 2 supported Au-based catalysts for the dehydrogenation of 1,4-butanediol to prepare γ-butyrolactone. At 300 o °C and 2 MPa, after reacting for 10 h, the yield of γ-butyrolactone was only 88%. Liu et al. used a CuO / Cr 2 O 3 / Al 2 O 3 catalyst to catalytically dehydrogenate 1,6-hexanediol in the gas phase to prepare caprolactone. At a reaction temperature of 300 °C, a space velocity of 0.08 h -1 , a hydrogen-to-alcohol molar ratio of 8:2, the conversion rate of 1,6-hexanediol reached 100%, but the yield of caprolactone was only 66.2% (Modern Chemical Industry, Vol. 27, No. 10, P41). US Patent US Pat.2,807,629 prepared the target product by liquid-phase dehydrogenation and distillation purification of diethylene glycol by changing the chromium content in the copper / chromium compound catalyst to 10% - 50%, and the maximum yield was only increased to 81%. Zhao et al. prepared a series of Cu-Cr catalysts using ammonia water as a precipitant and used them in the dehydrogenation reaction of 1,4-butanediol. Under the conditions of 200 °C, 0.1 MPa, and a liquid volume space velocity of 0.3 h -1 , the highest yield of γ-butyrolactone could reach 94.1%. Patent CN112473675A prepared a catalyst with copper oxide and silica as active components by the coprecipitation method. Under the conditions of normal pressure, 260 °C, a gas space velocity of 240 h -1 , and a liquid space velocity of 0.3 h -1 , the conversion rate of diethylene glycol was 88.56%, and the selectivity to dioxane-2-one was 92.22%.

[0004] It is not difficult to see from the prior art disclosed at home and abroad that when preparing the corresponding lactone by the catalytic dehydrogenation method of diol, traditional catalysts such as Cu / Cr and Au / SnO 2 have a very low conversion rate of diol, require high reaction conditions or contain toxic chromium components. In addition, Al 2 O 3 , SiO 2 carriers often lead to easy sintering and deactivation of metal active components due to their low specific surface area and poor conductivity, resulting in a short catalyst life. In short, existing catalysts are difficult to achieve high conversion rate, high selectivity and long life at the same time, and the preparation process is complex and the cost is high. Summary of the Invention

[0005] An object of the present invention is to solve the above problems and / or deficiencies and provide the advantages described hereinafter.

[0006] To achieve these objects and other advantages of the present invention, a preparation method of a copper-nickel single-atom catalyst based on an MXene carrier is provided, including the following steps: S1. Add citric acid and ammonium chloride to water in sequence and stir until dissolved, adjust the pH to prepare an electrolyte; Ti 3 AlC 2 powder is mixed with a binder, coated on a titanium foil, dried and then placed in the electrolyte, and electrolysis is carried out by controlling the temperature and voltage to obtain an MXene carrier; the MXene carrier is placed in deionized water and ultrasonically dispersed to prepare a suspension; S2. Add a copper compound and a nickel compound to a mixed solution of water and ethanol to dissolve, add it to the suspension, stir and impregnate, and obtain an MXene carrier loaded with copper-nickel single atoms after drying, calcination and reduction; S3. Dissolve glucose and melamine in deionized water, add the MXene carrier loaded with copper-nickel single atoms, mix evenly and transfer to a reaction kettle, carry out hydrothermal reaction, then centrifuge, wash and dry, and carry out low-temperature carbonization in a tubular furnace to obtain a copper-nickel single-atom catalyst based on an MXene carrier coated with a nitrogen-doped carbon coating; Among them, the content of copper-nickel single atoms is 0.2-1.5 wt%, and the molar ratio of copper to nickel in the copper-nickel single atoms is 1:0.3-1:1.2; the content of the nitrogen-doped carbon coating is 7-10 wt%.

[0007] Preferably, in S1, the pH of the electrolyte is 3-5, the electrolysis temperature is 20-60 °C, and the voltage is 0.2-0.6 V; The MXene carrier is few-layer Ti 3 C 2 T X nanosheets with 2-5 layers; The specific surface area of the MXene support is > 250 m² / g, and the conductivity is > 6×10 5 S / m; The binder is polyvinylidene fluoride, and the mass ratio of Ti 3 AlC 2 powder to polyvinylidene fluoride is 9:1; The method for adjusting the pH value is to add a pH regulator, and the pH regulator includes any one or a combination of at least two of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate, ammonium bicarbonate, ammonia water, sodium hydroxide, potassium hydroxide, nitric acid, hydrochloric acid, sulfuric acid, acetic acid.

[0008] Preferably, in the S2, the molar ratio of copper in the copper compound to nickel in the nickel compound is 1:0.3 to 1:1.2, and the ratio of the total mass of the copper compound and the nickel compound to the amount of the mixed solution used is 1 g:10 mL to 1 g:13 mL; The copper compound includes any one or a combination of at least two of copper nitrate, copper carbonate, copper acetate, copper chloride, copper hydroxide, or copper sulfate; The nickel compound includes any one or a combination of at least two of nickel nitrate, nickel sulfate, nickel chloride, nickel phthalocyanine, nickel acetate, nickel citrate, nickel hydroxide; The calcination method is to heat in segments at a temperature of 250 to 500 °C for 3 to 8 h; The reduction treatment method is to heat at a temperature of 200 to 400 °C for 1 to 4 h in an atmosphere of one gas or a mixed gas of hydrogen, carbon monoxide, or nitrogen.

[0009] Preferably, in the S3, the hydrothermal reaction conditions are to react at a temperature of 150 to 220 °C for 6 to 24 h; The low-temperature carbonization treatment method is to heat at a temperature of 300 to 500 °C for 1 to 7 h; The mass ratio of glucose to melamine is 1:1 to 3:1, and the ratio of the total mass of glucose and melamine to the amount of deionized water used is 1 g:80 mL to 1 g:150 mL; The nitrogen-doped carbon layer content is 7 to 10 wt%, and the layer thickness is 1 to 3 nm.

[0010] A copper-nickel single-atom catalyst based on an MXene support, which is prepared by the preparation method of the above copper-nickel single-atom catalyst based on an MXene support.

[0011] An application of a copper-nickel single-atom catalyst based on an MXene support, and the copper-nickel single-atom catalyst based on an MXene support is applied to the catalytic dehydrogenation cyclization reaction of diols to prepare lactones.

[0012] Preferably, the diol includes any one or a combination of at least two of diethylene glycol, 1,6 - hexanediol, 1,5 - hexanediol, 1,4 - hexanediol, 1,5 - pentanediol, 1,4 - pentanediol, 1,4 - butanediol, or 1,3 - propanediol and their derivatives.

[0013] Preferably, the diol includes any one or a combination of at least two of 1,4 - butanediol, 1,5 - pentanediol, 1,6 - hexanediol, or diethylene glycol and their derivatives.

[0014] Preferably, the raw material for the dehydrogenative cyclization reaction of the diol is the diol, and the process of the dehydrogenative cyclization reaction of the diol is a mixed gasification dehydrogenative cyclization reaction of the diol with a mixed gas of hydrogen and nitrogen to generate the corresponding lactone.

[0015] Preferably, the temperature of the dehydrogenative cyclization reaction of the diol is 200 - 300 °C; the mass space velocity of the dehydrogenative cyclization reaction of the diol is 0.1 - 10 h -1 ; the molar ratio of hydrogen to nitrogen is 0.5:1 - 12:1; the molar ratio of the diol to the mixed gas of hydrogen and nitrogen is 1:1 - 10:1.

[0016] The present invention has at least the following beneficial effects: 1. The copper - nickel single - atom catalyst based on the MXene support provided by the present invention adopts a ternary composite system of MXene / copper - nickel single - atom / nitrogen - doped carbon layer. The MXene support provides rich surface active sites, anchors copper - nickel single - atoms through chemical adsorption to ensure atomic - level dispersion; the dehydrogenation active center of copper atoms and the cyclization active center of nickel atoms act synergistically, and the high conductivity of the support accelerates electron transfer, reduces the activation energy of the reaction, and achieves a double breakthrough of conversion rate > 99% and selectivity > 99%.

[0017] 2. For the copper - nickel single - atom catalyst based on the MXene support provided by the present invention, the surface functional groups (-OH) of the MXene support form covalent bonds of Ti - O - M (M = Cu / Ni) with copper - nickel single - atoms, effectively inhibiting metal migration and agglomeration at high temperatures. The coated nitrogen - doped carbon layer forms a C - Ti bonding interaction with MXene, significantly improving the antioxidant property and avoiding the inactivation of active sites. The catalyst life exceeds 2000 hours.

[0018] 3. The copper - nickel single - atom catalyst based on the MXene support provided by the present invention can be used in the dehydrogenative cyclization reaction of diols to generate the corresponding lactones, with strong universality. By precisely controlling the structure and electronic properties of the catalyst, high selectivity for the products of the dehydrogenative cyclization reaction of diols is achieved. The reaction by - product is high - purity hydrogen, which can be directly used in the hydrogenation process to realize resource recycling.

[0019] 4. The copper-nickel single-atom catalyst based on the MXene support provided by the present invention does not involve toxic chromium metal in the whole process, overcomes the technical bottlenecks of low activity, short lifespan, and heavy pollution of traditional catalysts, provides an efficient solution for the green synthesis of lactones, and has remarkable technological advancement and commercial potential. Description of the Drawings

[0020] Figure 1 It is a graph showing the change of the conversion rate of the catalytic dehydrogenation cyclization reaction of diethylene glycol with time by catalyst B prepared in Example 2; Figure 2 It is a graph showing the change of the selectivity for the formation of p-dicyclohexanone in the catalytic dehydrogenation cyclization reaction of diethylene glycol with time by catalyst B prepared in Example 2. Detailed Embodiments

[0021] The following further describes the present invention in detail with reference to the drawings, so that those skilled in the art can implement it according to the description in the specification.

[0022] It should be understood that the terms such as "having", "comprising", and "including" used herein do not exclude the presence or addition of one or more other elements or their combinations. Example 1 S1. Add 9.8 g of citric acid and 5.5 g of ammonium chloride to deionized water in sequence, stir until completely dissolved, add hydrochloric acid to adjust the pH to 3.0, and make up the volume to 200 mL with a volumetric flask to obtain an electrolyte solution for standby; add 9 g of Ti 3 AlC 2 powder and 1 g of polyvinylidene fluoride (PVDF) binder are mixed and coated on the titanium foil, dried and then placed in the electrolyte. The solid-liquid ratio of electrolytic stripping is 1 g:100 ml, electrolyze at a voltage of 0.4 V for 4 h. After the electrolysis is completed, perform ultrasonic treatment, and wash with deionized water by centrifugation until neutral to obtain dry few-layer Ti 3 C 2 T X nanosheet powder, that is, the MXene support. Disperse 1 g of Ti 3 C 2 T X nanosheet powder in 100 mL of deionized water, and perform ultrasonic treatment for 10 min to prepare a suspension; S2. Weigh 7.25 g of copper nitrate trihydrate and 4.24 g of nickel nitrate hexahydrate, dissolve them in a mixed solution of 60 mL of deionized water and 60 mL of ethanol, add them to the suspension, stir and impregnate at room temperature for 2 h, perform centrifugal separation, wash with deionized water, dry at 60 °C for 12 h, calcine in a muffle furnace at 350 °C for 2 h, and reduce with hydrogen at 300 °C for 2 h to obtain Ti 3 C 2 T X powder loaded with copper-nickel single atoms; S3. Dissolve 3 g of glucose and 2 g of melamine in 500 mL of deionized water, add the Ti powder loaded with copper and nickel single atoms, disperse it by ultrasonic wave, transfer it to a reaction kettle, carry out hydrothermal reaction at 180 °C for 12 h, then centrifuge, wash and dry. Carbonize it at 500 °C for 2 h in a tubular furnace under Ar atmosphere to obtain catalyst A (copper-nickel single atom catalyst based on MXene support). 3 C 2 T X Powder, disperse it by ultrasonic wave, transfer it to a reaction kettle, carry out hydrothermal reaction at 180 °C for 12 h, then centrifuge, wash and dry. Carbonize it at 500 °C for 2 h in a tubular furnace under Ar atmosphere to obtain catalyst A (copper-nickel single atom catalyst based on MXene support).

[0023] Under atmospheric pressure, adjust the temperature to 220 °C. Mix the mixed gas of hydrogen and nitrogen with a molar ratio of 10:1 with diethylene glycol and continuously pass it through a vaporization superheater for vaporization, and then introduce it into a fixed-bed tubular reactor filled with 5 g of catalyst A (copper-nickel single atom catalyst based on MXene support) for contact reaction. The effluent after the reaction is condensed and separated to obtain the product. The liquid hourly space velocity of diethylene glycol is 0.5 h -1 . The reaction product is measured by a gas chromatograph equipped with a packed column GDX-102. The conversion rate of diethylene glycol is 99.1%, the selectivity to dioxane is 99.3%, and the service life of the catalyst can reach 180 days.

[0024] Example 2 S1. Add 9.8 g of citric acid and 5.5 g of ammonium chloride to deionized water in turn and stir until completely dissolved. Dropwise add hydrochloric acid to adjust the pH to 3.0, and make up the volume to 200 mL with a volumetric flask to prepare the electrolyte for standby; Mix 9 g of Ti 3 AlC 2 Powder and 1 g of PVDF binder are mixed and coated on the titanium foil. After drying, place it in the electrolyte. The solid-liquid ratio of electrolytic stripping is 1 g:80 ml, and electrolyze at a voltage of 0.4 V for 3 h. After the electrolysis is completed, carry out ultrasonic treatment for 20 min, and centrifuge and wash with deionized water until neutral to obtain dry few-layer Ti 3 C 2 T X Nanosheet powder; Disperse 1 g of Ti 3 C 2 T X Nanosheet powder in 100 mL of deionized water and carry out ultrasonic treatment for 10 min to prepare a suspension; S2. Weigh 6.04 g of copper nitrate trihydrate and 3.64 g of nickel nitrate hexahydrate and dissolve them in 100 mL of deionized water, add them to the suspension, stir and impregnate at room temperature for 2 h, centrifuge and separate, wash with deionized water, dry at 60 °C for 12 h, calcine in a muffle furnace at 400 °C for 2 h, and reduce with hydrogen at 300 °C for 2 h to obtain the Ti powder loaded with copper and nickel single atoms 3 C 2 T X Powder; S3. Dissolve 2 g of glucose and 1 g of melamine in 360 mL of deionized water, add the Ti powder loaded with copper and nickel single atoms, disperse it by ultrasonic wave, transfer it to a reaction kettle, carry out hydrothermal reaction at 180 °C for 12 h, then centrifuge, wash and dry it, and carbonize it at 500 °C for 2 h in a tubular furnace under Ar atmosphere to obtain catalyst B. 3 C 2 T X Powder, disperse it by ultrasonic wave, transfer it to a reaction kettle, carry out hydrothermal reaction at 180 °C for 12 h, then centrifuge, wash and dry it, and carbonize it at 500 °C for 2 h in a tubular furnace under Ar atmosphere to obtain catalyst B.

[0025] At atmospheric pressure, adjust the temperature to 230 °C. Mix the mixed gas of hydrogen and nitrogen with a molar ratio of 10:1 with diethylene glycol and continuously pass it through a vaporization superheater for vaporization, and then introduce it into a fixed-bed tubular reactor containing 6.5 g of catalyst B for contact reaction. The effluent after the reaction is condensed and separated to obtain the product. The liquid hourly space velocity of diethylene glycol is 0.8 h -1 , and the reaction product is analyzed by a gas chromatograph equipped with a packed column GDX-102, as shown in Figure 1 and Figure 2 . In the continuous catalytic reaction for 180 days, the conversion rate of diethylene glycol is measured to be greater than 99.9%, and the selectivity for dicyclohexanone is greater than 99.5%. This not only shows that catalyst B has a high conversion rate of diethylene glycol and selectivity for dicyclohexanone, but also in the continuous catalytic process for 180 days, catalyst B still maintains extremely high conversion rate and selectivity, indicating that the service life of catalyst B can reach 180 days.

[0026] Example 3 S1. Add 9.8 g of citric acid and 5.5 g of ammonium chloride to deionized water in turn, stir until completely dissolved, dropwise add hydrochloric acid to adjust the pH to 3.0, and make up the volume to 200 mL with a volumetric flask to prepare the electrolyte for standby; Mix 8 g of Ti 3 AlC 2 Powder and 1 g of PVDF binder are mixed and coated on the titanium foil, dried and placed in the electrolyte, electrolyzed at a voltage of 0.4 V for 4 h. After the electrolysis is completed, perform ultrasonic treatment, centrifuge and wash with deionized water until neutral to obtain dry few-layer Ti 3 C 2 T X nanosheet powder; S2. Weigh 7.25 g of copper nitrate trihydrate and 2.73 g of nickel nitrate hexahydrate and dissolve them in a mixed solution of 80 mL of deionized water and 50 mL of ethanol. Add 2 g of Ti 3 C 2 T X nanosheet powder, disperse it by ultrasonic wave for 15 min, stir and impregnate it at room temperature for 4 h, centrifuge and separate, wash it with deionized water, dry it at 60 °C for 12 h, calcine it in a muffle furnace at 350 °C for 2 h, and reduce it with hydrogen at 300 °C for 2 h to obtain the Ti 3 C 2 T X powder loaded with copper and nickel single atoms.

[0027] S3. Dissolve 1 g of glucose and 1 g of melamine in 260 mL of deionized water, add the Ti powder loaded with single-atom copper and nickel, ultrasonically disperse it, transfer it to a reaction kettle, carry out hydrothermal reaction at 180 °C for 14 h, then centrifuge, wash, and dry. Carbonize it at 500 °C for 2 h in a tubular furnace under Ar atmosphere to obtain catalyst C. 3 C 2 T X Powder, ultrasonically disperse, transfer to a reaction kettle, carry out hydrothermal reaction at 180 °C for 14 h, then centrifuge, wash, and dry. Carbonize it at 500 °C for 2 h in a tubular furnace under Ar atmosphere to obtain catalyst C.

[0028] Under atmospheric pressure, adjust the temperature to 230 °C. Mix the mixed gas of hydrogen and nitrogen with a molar ratio of 8:1 with diethylene glycol and continuously vaporize it through a vaporization superheater, and then introduce it into a fixed-bed tubular reactor containing 4 g of catalyst C for contact reaction. The effluent after the reaction is condensed and separated to obtain the product. The liquid hourly space velocity of diethylene glycol is 0.5 h -1 . The reaction product is measured by a gas chromatograph equipped with a packed column GDX-102. The conversion rate of diethylene glycol is 99.4%, the selectivity for dicyclohexanone is 98.3%, and the service life of the catalyst can reach 180 days.

[0029] Example 4 S1. Add 9.8 g of citric acid and 5.5 g of ammonium chloride to deionized water in sequence and stir until completely dissolved. Dropwise add hydrochloric acid to adjust the pH to 3.0, and make up the volume to 200 mL with a volumetric flask to prepare the electrolyte for standby; Mix 8 g of Ti 3 AlC 2 Powder and 1 g of PVDF binder are mixed and coated on the titanium foil. After drying, place it in the electrolyte. The solid-liquid ratio of electrolytic stripping is 2 g:80 ml, and electrolyze at a voltage of 0.5 V for 4 h. After the electrolysis is completed, carry out ultrasonic treatment, and centrifuge and wash with deionized water until neutral to obtain dry few-layer Ti 3 C 2 T X Nanosheet powder. Disperse 1 g of Ti 3 C 2 T X Nanosheet powder in 100 mL of deionized water and ultrasonically treat it for 10 min to prepare a suspension; S2. Weigh 7.25 g of copper nitrate trihydrate and 2.42 g of nickel nitrate hexahydrate and dissolve them in a mixed solution of 50 mL of water and 50 mL of ethanol. Add it to the suspension, stir and impregnate at room temperature for 2 h, centrifuge and separate, wash with deionized water, dry at 60 °C for 12 h, calcine in a muffle furnace at 350 °C for 2 h, and reduce with hydrogen at 300 °C for 2 h to obtain the Ti 3 C 2 T X Powder loaded with single-atom copper and nickel; S3. Dissolve 3 g of glucose and 1 g of melamine in 320 mL of deionized water, add the Ti powder loaded with single-atom copper and nickel 3 C 2T X The powder was ultrasonically dispersed, transferred to a reactor, hydrothermally reacted at 180 °C for 12 h, then centrifuged, washed, and dried. It was carbonized at 500 °C for 3 h in a tubular furnace under an Ar atmosphere to obtain the catalyst D of the present invention.

[0030] The system pressure was adjusted to 0.3 Mpa and the temperature to 275 °C. A mixed gas of hydrogen and nitrogen with a molar ratio of 8:1 was mixed with 1,6 - hexanediol and continuously vaporized through a vaporization superheater, and then introduced into a fixed - bed tubular reactor containing 6.5 g of catalyst D for contact reaction. The effluent after the reaction was condensed and separated to obtain a liquid product. The liquid hourly space velocity of 1,6 - hexanediol was 0.8 h -1 , and the reaction product was measured by a gas chromatograph equipped with a capillary column OV - 1. The conversion rate of 1,6 - hexanediol was 99.2%, and the selectivity of ε - caprolactone was 97.9%. The service life of the catalyst D prepared in this example could reach 180 days.

[0031] Example 5 S1. 9.8 g of citric acid and 5.5 g of ammonium chloride were successively added to deionized water and stirred until completely dissolved. Hydrochloric acid was added dropwise to adjust the pH to 3.0, and the solution was made up to the mark in a 200 - mL volumetric flask to prepare an electrolyte for standby. 9 g of Ti 3 AlC 2 The powder was mixed with 1 g of PVDF binder, coated on a titanium foil, dried, and placed in the electrolyte. The solid - liquid ratio for electrolytic stripping was 1 g:80 ml, and electrolysis was carried out at a voltage of 0.4 V for 3 h. After the electrolysis, ultrasonic treatment was carried out, and it was centrifuged and washed with deionized water until neutral to obtain dry few - layer Ti 3 C 2 T X nanosheet powder. 1 g of Ti 3 C 2 T X nanosheet powder was dispersed in 100 mL of deionized water, and ultrasonic treatment was carried out for 10 min to prepare a suspension; S2. 6.04 g of copper nitrate trihydrate and 3.64 g of nickel nitrate hexahydrate were dissolved in 100 mL of deionized water, added to the suspension, stirred and impregnated at room temperature for 2 h, centrifuged and separated, washed with deionized water, dried at 60 °C for 12 h, calcined in a muffle furnace at 400 °C for 2 h, and reduced with hydrogen at 300 °C for 2 h to obtain Ti loaded with copper and nickel single atoms 3 C 2 T X powder; S3. 2 g of glucose and 1.2 g of melamine were dissolved in 380 mL of deionized water, and Ti loaded with copper and nickel single atoms 3 C 2 T XThe powder was ultrasonically dispersed, transferred to a reactor, and subjected to hydrothermal reaction at 180 °C for 12 h. After centrifugation, washing, and drying, it was carbonized at 500 °C for 2 h in a tubular furnace under an Ar atmosphere to obtain catalyst E.

[0032] The temperature was adjusted to 250 °C. A mixed gas of hydrogen and nitrogen with a molar ratio of 10:1 was mixed with 1,6 - hexanediol at a molar ratio of 1:1 and continuously vaporized through a vaporization superheater, and then introduced into a fixed - bed tubular reactor containing 7.5 g of catalyst E for contact reaction. The effluent after the reaction was condensed and separated to obtain a liquid product. The liquid hourly space velocity of 1,6 - hexanediol was 1 h -1 , and the reaction product was measured by a gas chromatograph equipped with a capillary column OV - 1. The conversion rate of 1,6 - hexanediol was 99.5%, and the selectivity of ε - caprolactone was 99.2%. The service life of catalyst E prepared in this example could reach 180 days.

[0033] Comparative Example 1 S1. 1 g of graphene powder was dispersed in 100 mL of deionized water and ultrasonicated for 10 min to prepare a suspension; S2. 6.04 g of copper nitrate trihydrate and 3.64 g of nickel nitrate hexahydrate were dissolved in 200 mL of deionized water, added to the graphene suspension, stirred and impregnated at room temperature for 2 h, centrifuged, washed with deionized water, dried at 60 °C for 12 h, calcined in a muffle furnace at 400 °C for 2 h, and reduced with hydrogen at 300 °C for 2 h to obtain Comparative Catalyst 1 (graphene powder loaded with copper and nickel single atoms); S3. 2 g of glucose and 1 g of melamine were dissolved in 360 mL of deionized water, added with the graphene powder loaded with copper and nickel single atoms, ultrasonically dispersed, transferred to a reactor, and subjected to hydrothermal reaction at 180 °C for 12 h. After centrifugation, washing, and drying, it was carbonized at 500 °C for 2 h in a tubular furnace under an Ar atmosphere to obtain Comparative Catalyst B1.

[0034] Under atmospheric pressure, the temperature was adjusted to 230 °C. A mixed gas of hydrogen and nitrogen with a molar ratio of 10:1 was mixed with diethylene glycol and continuously vaporized through a vaporization superheater, and then introduced into a fixed - bed tubular reactor containing 6.5 g of Comparative Catalyst B1 for contact reaction. The effluent after the reaction was condensed and separated to obtain a product. The liquid hourly space velocity of diethylene glycol was 0.8 h -1 , and the reaction product was measured by a gas chromatograph equipped with a packed column GDX - 102. The conversion rate of diethylene glycol was 76.5%, and the selectivity for dicyclohexanone was 80.4%.

[0035] Comparative Example 2 S1. 1 g of MoS 2 powder was dispersed in 100 mL of deionized water and ultrasonicated for 10 min to prepare a suspension.

[0036] S2. Weigh 6.04 g of copper nitrate trihydrate and 3.64 g of nickel nitrate hexahydrate, dissolve them in 200 mL of deionized water, add them to the graphene suspension, stir and impregnate at room temperature for 2 h, centrifuge and separate, wash with deionized water, dry at 60 °C for 12 h, calcine in a muffle furnace at 400 °C for 2 h, and reduce with hydrogen at 300 °C for 2 h to obtain the comparative catalyst C1.

[0037] Under atmospheric pressure, adjust the temperature to 230 °C. Mix a hydrogen-nitrogen mixed gas with a molar ratio of 8:1 with diethylene glycol and continuously pass it through a vaporization superheater for vaporization, and then introduce it into a fixed-bed tubular reactor containing 4 g of the comparative catalyst C1 for contact reaction. After the reaction, the effluent is condensed and separated to obtain the product. The liquid hourly space velocity of diethylene glycol is 0.5 h -1 . The reaction product is measured by a gas chromatograph equipped with a packed column GDX-102. The conversion rate of diethylene glycol is 64.7%, the selectivity to dicyclohexanone is 73.8%, and the service life of the catalyst is 380 hours.

[0038] Comparative Example 3 Prepare a mixed solution containing copper nitrate, chromium nitrate and aluminum nitrate (molar ratio 2∶2∶1). Under stirring at 70 °C, dropwise add the Na 2 CO 3 solution into the above mixed solution. The obtained precipitate is centrifuged, washed, dried at 100 °C for 24 h, then calcined for 3 h, and tableted to form the catalyst CuO / Cr 2 O 3 / Al 2 O 3 (Modern Chemical Industry, Vol. 27, No. 10, P41).

[0039] Adjust the temperature to 250 °C. Mix a hydrogen-nitrogen mixed gas with a molar ratio of 10:1 with 1,6-hexanediol at a molar ratio of 1:1 and continuously pass it through a vaporization superheater for vaporization, and then introduce it into a fixed-bed tubular reactor containing 6.5 g of the catalyst CuO / Cr 2 O 3 / Al 2 O 3 for contact reaction. After the reaction, the effluent is condensed and separated to obtain the liquid product. The liquid hourly space velocity of 1,6-hexanediol is 1 h -1 . The reaction product is measured by a gas chromatograph equipped with a capillary column OV-1. The conversion rate of 1,6-hexanediol is 85.7%, and the selectivity to ε-caprolactone is 52.3%.

[0040] The equipment quantities and processing scales described here are used to simplify the description of the present invention. Applications, modifications and variations of the present invention will be apparent to those skilled in the art.

[0041] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those skilled in the art, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and the examples shown and described herein.

Claims

1. A method for preparing a copper-nickel single-atom catalyst based on a MXene carrier, characterized in that: The following steps are involved: S1. Add citric acid and ammonium chloride into water in sequence and stir until dissolved, adjust the pH to prepare an electrolyte; Ti3AlC2 powder and a binder are mixed and coated on a titanium foil, dried, and placed in an electrolyte, and the temperature and voltage are controlled for electrolysis to obtain a MXene carrier; the MXene carrier is placed in deionized water and ultrasonically dispersed to obtain a suspension; S2, adding a copper compound and a nickel compound to a mixed solution of water and ethanol to dissolve, adding the mixture to the suspension, stirring and impregnating, and drying, calcining and reducing to obtain a MXene carrier loaded with copper and nickel single atoms; S3, dissolving glucose and melamine in deionized water, adding a MXene carrier loaded with copper-nickel single atoms, mixing evenly and transferring to a reactor, centrifuging, washing, drying, and carbonizing in a tubular furnace at low temperature after hydrothermal reaction, to obtain a copper-nickel single atom catalyst based on a MXene carrier coated with a nitrogen-doped carbon coating layer; Among them, the content of copper-nickel single atoms is 0.2~1.5wt%, and the molar ratio of copper and nickel in the copper-nickel single atoms is 1:0.3~1:1.2; the content of the nitrogen-doped carbon coating layer is 7~10wt%.

2. The method for preparing a copper-nickel single-atom catalyst based on a MXene carrier according to claim 1, characterized in that: In S1, the pH of the electrolyte is 3-5, the electrolysis temperature is 20-60°C, and the voltage is 0.2-0.6V; The MXene carrier is a few-layer Ti3C2T X Nanosheets, 2 to 5 layers; The MXene carrier has a specific surface area of ​​>250m² / g and a conductivity of >6×10 5 S / m; The binder is polyvinylidene fluoride, and the mass ratio of Ti3AlC2 powder to polyvinylidene fluoride is 9:1; The method for adjusting the pH value is to add a pH adjuster, and the pH adjuster includes any one of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate, ammonium bicarbonate, ammonia water, sodium hydroxide, potassium hydroxide, nitric acid, hydrochloric acid, sulfuric acid, and acetic acid, or a combination of at least two thereof.

3. The method for preparing a copper-nickel single-atom catalyst based on a MXene carrier according to claim 1, characterized in that: In S2, the molar ratio of copper in the copper compound to nickel in the nickel compound is 1:0.3 to 1:1.2, and the total mass of the copper compound and the nickel compound to the amount of the mixed solution is 1 g:10 mL to 1 g:13 mL; The copper compound includes any one of copper nitrate, copper carbonate, copper acetate, copper chloride, copper hydroxide or copper sulfate, or a combination of at least two thereof; The nickel compound includes any one of nickel nitrate, nickel sulfate, nickel chloride, nickel phthalocyanine, nickel acetate, nickel citrate, and nickel hydroxide, or a combination of at least two thereof; The calcination method is to heat in stages at a temperature of 250-500° C. for 3-8 hours; The reduction treatment method is to heat at a temperature of 200-400° C. for 1-4 hours in an atmosphere of hydrogen, carbon monoxide or nitrogen or a mixed gas.

4. The method for preparing a copper-nickel single-atom catalyst based on a MXene carrier according to claim 1, characterized in that: In S3, the hydrothermal reaction conditions are 150-220° C. for 6-24 hours; The low-temperature carbonization treatment method is heating at 300~500℃ for 1~7h; The mass ratio of glucose to melamine is 1:1-3:1, and the dosage ratio of the total mass of glucose and melamine to deionized water is 1g:80mL-1g:150mL; The nitrogen-doped carbon layer has a content of 7-10 wt % and a layer thickness of 1-3 nm.

5. A copper-nickel single-atom catalyst based on a MXene support, characterized in that: The copper-nickel single-atom catalyst based on a MXene carrier is prepared by the preparation method of the copper-nickel single-atom catalyst based on a MXene carrier according to any one of claims 1 to 4.

6. An application of the copper-nickel single-atom catalyst based on a MXene carrier according to claim 5, characterized in that: The MXene-supported copper-nickel single-atom catalyst is used to catalyze the dehydrogenation cyclization reaction of diols to prepare lactones.

7. The use of the copper-nickel single-atom catalyst based on a MXene carrier according to claim 6, characterized in that: The diol includes any one or a combination of at least two of diethylene glycol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 1,5-pentanediol, 1,4, pentanediol, 1,4-butanediol or 1,3-propylene glycol and derivatives thereof.

8. The use of the copper-nickel single-atom catalyst based on a MXene carrier according to claim 6, characterized in that: The diol includes any one of 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol or diethylene glycol and derivatives thereof, or a combination of at least two thereof.

9. The use of the copper-nickel single-atom catalyst based on a MXene carrier according to claim 6 or 7, characterized in that: The raw material of the diol dehydrogenation cyclization reaction is diol, and the process of the diol dehydrogenation cyclization reaction is a mixed gasification dehydrogenation cyclization reaction of diol with a mixed gas of hydrogen and nitrogen to generate the corresponding lactone.

10. The use of the copper-nickel single-atom catalyst based on a MXene carrier according to claim 9, characterized in that: The temperature of the diol dehydrogenation cyclization reaction is 200-300°C; the mass space velocity of the diol dehydrogenation cyclization reaction is 0.1-10h -1 ; The molar ratio of hydrogen to nitrogen is 0.5:1~12:1; the molar ratio of glycol to the mixed gas of hydrogen and nitrogen is 1:1~10:1.

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