Alloy monatomic catalyst and preparation method and application thereof

Abstract

The invention discloses an alloy monatomic catalyst as well as a preparation method and application thereof. The alloy monatomic catalyst comprises a carrier and an active component, the active component comprises a first metal and a second metal; the first metal is dispersed in the transition metal in a monatomic form to form monatomic alloy and is loaded on the carrier; the first metal comprises one or more than two of gallium, tin, indium and bismuth; the second metal includes a transition metal. The catalyst developed by the invention can directly dehydrogenate an alcohol compound to obtain an aldehyde or ketone compound, can produce hydrogen as a byproduct, does not need carrier gas, has the advantages of high atom economy, green process, high aldehyde and ketone production efficiency, energy conservation, efficiency improvement and the like, and has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of bioenergy chemical industry, and more specifically, to an alloy single-atom catalyst and a preparation method and application thereof. Background Art

[0002] Small molecule alcohols, including primary alcohols such as ethanol and n-propanol and secondary alcohols such as isopropanol, are an important class of platform compounds with advantages such as abundant production and wide sources. In contrast, some aldehyde compounds and ketone compounds are difficult to prepare by conventional methods, and have disadvantages such as pollution during the synthesis process, equipment corrosion, and high carbon emissions. Therefore, it is urgent to develop new synthesis processes to achieve green preparation of aldehyde compounds and ketone compounds.

[0003] Take the catalytic conversion of ethanol to produce acetaldehyde as an example. At present, acetaldehyde is mainly produced by ethanol oxidation and dehydrogenation. This process reacts at 500℃~600℃, using air as an oxidant. The product after the reaction is absorbed by water and then separated by a tower to obtain pure acetaldehyde. Due to the high reaction temperature, this process consumes a lot of energy. In particular, it requires a water absorption step, which invisibly increases the separation cost. At the same time, the hydrogen and oxygen in this process react to produce water, and it is impossible to obtain green hydrogen of higher purity. Finally, the silver catalyst needs to be regenerated regularly.

[0004] In comparison, direct dehydrogenation of ethanol to produce acetaldehyde and hydrogen has the advantages of low reaction temperature, few by-products, and by-production of green hydrogen, making it an ideal way to prepare acetaldehyde. At the same time, direct dehydrogenation of ethanol is a key step in the catalytic conversion of ethanol, and plays a role as a bridge and link in the conversion of ethanol to produce high-value chemicals. Therefore, the research on direct dehydrogenation of ethanol has important application value and theoretical significance.

[0005] The direct dehydrogenation reaction of ethanol is a reversible reaction. Therefore, researchers generally use carrier gas to remove hydrogen to promote the reaction in the positive direction. However, this process results in a low hydrogen content in the product, which is difficult to utilize and has low economic efficiency in hydrogen recovery. On the other hand, existing copper-based catalysts have problems such as poor catalyst stability and easy aggregation and growth of copper particles, which adds challenges to the large-scale application of this technology. Summary of the invention

[0006] The purpose of the present invention is to overcome the above-mentioned defects of the prior art and to provide an alloy single-atom catalyst and a preparation method and application thereof. The catalyst developed by the present invention can directly dehydrogenate alcohol compounds to aldehydes or ketone compounds and produce hydrogen as a by-product without the need for a carrier gas. It has the advantages of high atom economy, green process, high efficiency in producing aldehydes and ketones, energy saving and efficiency improvement, and has broad application prospects.

[0007] To achieve the above object, the technical solution of the present invention is as follows:

[0008] An alloy single-atom catalyst comprises a carrier and an active component; the active component comprises a first metal and a second metal; the first metal is dispersed in the transition metal in the form of a single atom to form a single-atom alloy and is loaded on the carrier; the first metal comprises one or more of gallium, tin, indium and bismuth; the second metal comprises a transition metal.

[0009] Optionally, the carrier comprises aluminum oxide or silicon oxide.

[0010] Optionally, the second metal includes one or more of nickel, copper, cobalt and iron.

[0011] Optionally, the mass content of the second metal in the alloy single-atom catalyst is 2% to 80%.

[0012] Optionally, the mass content of the first metal in the alloy single-atom catalyst is 0.1% to 20%.

[0013] Optionally, the mass content of the second metal in the alloy single-atom catalyst is 5% to 60%.

[0014] Optionally, the mass content of the first metal in the alloy single-atom catalyst is 0.5% to 10%.

[0015] Optionally, the loading amount of the first metal and the second metal in the alloy single-atom catalyst is 2% to 90%.

[0016] Optionally, the particle size of the single-atom alloy in the alloy single-atom catalyst is 2 nm to 20 nm.

[0017] The present invention also discloses a method for preparing the alloy single-atom catalyst as described above, wherein the alloy single-atom catalyst is prepared by a coprecipitation method, comprising the following steps:

[0018] The first metal salt, the second metal salt and the carrier precursor are dissolved in a solvent, and a precipitant is added to form a mixed solution, followed by a coprecipitation reaction, and then the pH of the solution is adjusted to 8 to 10 to obtain a coprecipitation slurry;

[0019] The coprecipitation slurry is aged, filtered, washed and dried in sequence to obtain a precipitate;

[0020] The precipitate is calcined and reduced in sequence to obtain the alloy single-atom catalyst.

[0021] Optionally, the first metal salt and the second metal salt are respectively selected from one or more of metal nitrates, chlorides, sulfates, phosphates and acetates.

[0022] Optionally, the carrier precursor includes one or more of aluminum nitrate, tetraethyl orthosilicate and sodium silicate.

[0023] Optionally, the precipitant includes one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, ammonia water, urea, ammonium carbonate and ammonium bicarbonate.

[0024] Optionally, in the mixed solution, the metal ion concentrations of the first metal salt and the second metal salt are respectively 0.1 mol / L to 5 mol / L, the concentration of the precipitant is 0.1 mol / L to 10 mol / L, and the concentration of the carrier precursor is 0.1 mol / L to 5 mol / L.

[0025] Optionally, the coprecipitation reaction temperature is 0°C to 80°C.

[0026] Optionally, the aging temperature is 40°C to 90°C.

[0027] Optionally, the aging time is 3 hours to 24 hours.

[0028] Optionally, the drying temperature is 80° C. to 150° C.; and the drying time is 1 h to 24 h.

[0029] Optionally, the calcination temperature is 200° C. to 800° C., and the calcination time is 0.5 h to 20 h.

[0030] Optionally, the reduction temperature is 300° C. to 600° C., the reduction time is 0.5 h to 6 h, and the reduction atmosphere includes one or more of hydrogen, nitrogen and argon.

[0031] The present invention also discloses a method for preparing the alloy single-atom catalyst as described above, wherein the alloy single-atom catalyst is prepared by a coprecipitation-impregnation method, comprising the following steps:

[0032] The second metal salt and the carrier precursor are dissolved in a solvent to form a mixed solution, and a precipitant is added to form a mixed solution, and then a coprecipitation reaction is performed, and the pH of the solution is adjusted to 8 to 10 to obtain a coprecipitation slurry;

[0033] The coprecipitation slurry is aged, filtered, washed, and dried once to obtain a precipitate;

[0034] The precipitate is calcined and reduced to obtain a precursor;

[0035] The precursor is immersed in a first metal salt solution, so that the first metal is dispersed in the second metal in the form of single atoms to form a single-atom alloy and loaded on the carrier, and then subjected to secondary drying, calcination and reduction in sequence to obtain the alloy single-atom catalyst.

[0036] Optionally, the immersion temperature is 25°C to 35°C; and the immersion time is 1h to 24h.

[0037] Optionally, the first metal salt and the second metal salt are respectively selected from one or more of metal nitrates, chlorides, sulfates, phosphates and acetates.

[0038] Optionally, the carrier precursor includes one or more of aluminum nitrate, tetraethyl orthosilicate and sodium silicate.

[0039] Optionally, the precipitant includes one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, ammonia water, urea, ammonium carbonate and ammonium bicarbonate.

[0040] Optionally, the concentration of metal ions in the second metal salt in the mixed solution is 0.1 mol / L to 5 mol / L, the concentration of the precipitant is 0.1 mol / L to 10 mol / L, and the concentration of the carrier precursor is 0.1 mol / L to 5 mol / L.

[0041] Optionally, the concentration of metal ions in the first metal salt is 0.1 mol / L to 5 mol / L.

[0042] Optionally, the coprecipitation reaction temperature is 0°C to 80°C.

[0043] Optionally, the aging temperature is 40° C. to 90° C.; and the aging time is 3 h to 24 h.

[0044] Optionally, the temperatures of the primary drying and the secondary drying are 80° C. to 150° C. respectively; and the times of the primary drying and the secondary drying are 1 h to 24 h respectively.

[0045] Optionally, the calcination temperature is 200° C. to 800° C., and the calcination time is 0.5 h to 20 h.

[0046] Optionally, the reduction temperature is 300° C. to 600° C., the reduction time is 0.5 h to 6 h, and the reduction atmosphere includes one or more of hydrogen, nitrogen and argon.

[0047] The invention also discloses an application of the alloy single-atom catalyst as mentioned above in the dehydrogenation reaction of monohydric alcohol.

[0048] Optionally, the monohydric alcohol includes one or more of ethanol, n-propanol, n-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, isopropanol, isobutanol, isopentanol, isohexanol and isoheptanol.

[0049] Optionally, the reaction is carried out in a fixed bed reactor, the reaction pressure is 0.01MPa to 0.5MPa, the reaction temperature is 150°C to 360°C; the mass space velocity of the catalytic reaction is 0.1h -1 ~20h -1 ; There is no carrier gas in the reaction.

[0050] Optionally, the reaction pressure is 0.01MPa to 0.2MPa, the reaction temperature is 200°C to 320°C, and the mass space velocity of the catalytic reaction is 0.5h -1 ~15h -1 ; There is no carrier gas in the reaction.

[0051] Optionally, the reaction products are mainly aldehydes and ketone compounds; when the raw material is a monohydric primary alcohol, the product is the corresponding aldehyde, for example, when ethanol is used as the raw material, the product is acetaldehyde; when the raw material is a secondary alcohol, the product is a ketone compound, for example, when the raw material is isopropanol, the product is acetone.

[0052] Optionally, the reaction product contains hydrogen, the purity of which exceeds 99%, and can be directly used for hydrogenation reaction without separation.

[0053] Optionally, the selectivity of the aldehyde and ketone compounds exceeds 80%, and the catalyst operates stably for more than 3000 hours.

[0054] Implementing the embodiments of the present invention will have the following beneficial effects:

[0055] 1. The present invention provides a method for preparing an alloy single-atom catalyst. The preparation method has the advantages of simple process, less generation of three wastes, high metal atom utilization rate, and effective metal atomic-level dispersion. After drying, calcination, and reduction, the catalyst has a large specific surface area and is not easy to sinter.

[0056] 2. The present invention uses monohydric alcohol as raw material, which has abundant reserves, multiple varieties, sufficient sources, large output and low pollution; aldehydes and ketones produced after dehydrogenation of monohydric alcohol have wide applications in the fields of fuels, chemicals, etc. In addition, pure hydrogen is produced as a by-product in the gas phase, which can be used in some hydrogenation reactions.

[0057] 3. The alloy single-atom catalyst prepared by the present invention exhibits unique selectivity in the dehydrogenation reaction of monohydric alcohols, produces few by-products, and significantly reduces separation costs.

[0058] 4. The alloy single-atom catalyst provided by the present invention has good stability. When used for ethanol dehydrogenation reaction, the product is easy to separate and use. The whole process has good economy and practicality, meets the requirements of sustainable development, and has important economic value and industrial prospects in biomass conversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1This is a spherical aberration electron microscope photograph of the InNi-AlOx catalyst of Example 1 of the present invention (the white circle represents a single atom of In).

[0060] Figure 2 This is a transmission electron microscope photograph of the SnCu-AlOx catalyst of Example 2 of the present invention (the particle size of the catalyst bimetallic alloy is 10nm-15nm). DETAILED DESCRIPTION

[0061] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited in any way.

[0062] Example 1: InNi-AlOx Catalyst

[0063] 5.8 g Ni(NO3)2·6H2O, 0.8 g In(NO3)3·5H2O and 18.8 g Al(NO3)3·9H2O were dissolved in 50 mL of deionized water to obtain solution A. 4.6 g NaOH and 4.2 g Na2CO3 were dissolved in 100 mL of deionized water to obtain solution B.

[0064] Solution B was transferred to a hydrothermal device, placed in a 35°C water bath and mechanically stirred at 500rpm, and then solution A was added dropwise to solution B at a rate of 1mL / min. After precipitation, the pH of the solution was adjusted to about 10, and then the water bath temperature was increased to 65°C for dynamic aging for 18h. After aging, the solution was filtered, washed with 1L of deionized water and 100mL of ethanol in turn, the filter cake was taken out, dried at 80°C for 18h, calcined at 600°C for 2h, and reduced with H2 at 600°C for 1h to obtain a catalyst composed of InNi-AlOx. In this process, the catalyst metal In:Ni:Al molar ratio was 0.2:2:5.

[0065] Example 2: SnCu-AlOx Catalyst

[0066] The difference from Example 1 is that the active metals are Sn and Cu, the corresponding metal salts are tin acetate and copper nitrate, and the corresponding alkali amount is changed proportionally. Here, the precipitant is a mixed solution of potassium carbonate and potassium hydroxide, and the molar ratio of the two is the same as that of Preparation Example 1. After the adjustment, the molar ratio of the catalyst metal Sn:Cu:Al is 0.2:1:0.8.

[0067] Example 3: GaNi-AlOx Catalyst

[0068] The difference from Example 1 is that the precursor of the second metal is gallium nitrate, and the molar ratio of the catalyst metals Ga:Ni:Al is 0.2:2:5.

[0069] Example 4: InCo-SiO2 Catalyst

[0070] The difference from Example 1 is that the metal precursors are indium nitrate and copper nitrate, the precipitants are sodium hydroxide and ammonium carbonate, the silicon dioxide precursor is tetraethyl orthosilicate, and the molar ratio of the catalyst metal In:Co:Si is 0.2:2:5.

[0071] Example 5: BiFe-SiO2 Catalyst

[0072] The difference from Example 1 is that the metal precursors are bismuth nitrate and ferric chloride, the precipitants are potassium hydroxide and potassium carbonate, the silicon dioxide precursor is tetraethyl orthosilicate, and the catalyst metal Bi:Fe:Si molar ratio is 0.2:2:5.

[0073] Example 6: In / Ni-AlOx Catalyst

[0074] The difference from Example 1 is that Ni-AlOx is prepared by coprecipitation, and then In is loaded onto Ni-AlOx by impregnation. The impregnation temperature is 30° C., the impregnation time is 12 hours, and the molar ratio of catalyst metal In:Ni:Al is 0.2:2:5.

[0075] Comparative Example 1: NiAlOx Catalyst

[0076] The difference from Preparation Example 1 is that NiAlOx is prepared by coprecipitation method and is obtained directly after calcination and reduction. The molar ratio of catalyst metal Ni:Al is 2:5.

[0077] Comparative Example 2: CoSiO2 Catalyst

[0078] The difference from Preparation Example 1 is that the CoSiO2 catalyst is prepared by coprecipitation method and is obtained directly after calcination and reduction. The molar ratio of catalyst metal Co:Si is 2:5.

[0079] Reaction Example 1

[0080] The catalytic conversion experiment was carried out in a fixed bed reactor, and the specific conditions were as follows: the catalysts prepared in Examples 1-6 and Comparative Examples 1-2 were used to carry out the dehydrogenation reaction of monohydric alcohol, the reaction temperature was 200°C to 360°C, the reaction pressure was 0.1 MPa, and the reaction mass space velocity was 9.8 h -1 The amount of catalyst used was 10 g, and the catalyst was added to the fixed bed reactor for online hydrogen reduction, with a gas flow rate of 200 mL / min, a reduction temperature of 400 ° C, and a reduction time of 2 h. After reduction, the temperature was lowered to the reaction temperature, the raw materials were pumped in, and the gas phase products were analyzed by online gas chromatography.

[0081] The reaction results of using the catalysts prepared in Examples 1-6 and Comparative Examples 1-2 for ethanol dehydrogenation are shown in Table 1-2.

[0082] Table 1 Results of ethanol catalytic dehydrogenation reaction using different catalysts (reaction temperature 300°C, results after stable reaction for 4 hours)

[0083]

[0084]

[0085] Table 2 Catalysts prepared under different conditions for ethanol catalytic dehydrogenation reaction results (reaction temperature 300 ° C, reaction stable 4h results)

[0086]

[0087] Table 1 compares the product changes of different catalysts for ethanol dehydrogenation reactions. From the reaction data, it can be seen that compared with the single metal catalysts such as Ni or Co in the comparative example, the bimetallic catalyst prepared by coprecipitation or coprecipitation-impregnation method has good reaction activity and product selectivity. In particular, the InNi-AlOx catalyst of Example 1 has an acetaldehyde selectivity of 86.7%, a hydrogen selectivity of 99.5%, and a by-product ethyl acetate selectivity of 12.2%, showing good and excellent product selectivity. In addition, alloy single atoms synthesized from Ga, Bi and Co, Ni, Fe, etc. also have excellent acetaldehyde and hydrogen selectivity.

[0088] Table 2 compares the product changes of catalysts with different doping amounts for ethanol dehydrogenation reactions. From the reaction data, it can be seen that different metal doping amounts also have a certain influence on the reaction activity and product selectivity of the bimetallic catalyst. Therefore, the present application adjusts the optimal doping amount so that the prepared catalyst has the best catalytic performance.

[0089] Reaction Example 2

[0090] The specific reaction conditions are the same as those in Reaction Example 1, except that the monohydric alcohol is expanded from ethanol to other alcohols. The results are shown in Table 3:

[0091] The catalysts prepared in Example 1 were used for the catalytic dehydrogenation of monohydric alcohols (reaction temperature 300°C, reaction mass space velocity 8.9h -1 ), and the results are shown in Table 3.

[0092] Table 3 Conversion results of different monohydric alcohols on InNi-AlOx catalyst (results after 4h reaction)

[0093]

[0094] From the reaction data in Table 2, we can see that although the type of monohydric primary alcohol has changed, it can be converted into corresponding aldehyde compounds and hydrogen (hydrogen selectivity is greater than 99%), showing good universality. In addition, when monohydric secondary alcohol is used as the raw material, the product is mainly ketone compounds, and the product selectivity is also greater than 80%.

[0095] Reaction Example 3

[0096] Except for the reaction conditions specially described in Table 4, other reaction conditions are the same as those in Reaction Example 1. The results of using the catalyst GaNi-AlOx in Preparation Example 3 for catalytic dehydrogenation of ethanol (300° C.) are shown in Table 4.

[0097] Table 4 Results of ethanol catalytic dehydrogenation on GaNi-AlOx catalyst under different conditions (results after the reaction was stable for 3h)

[0098] Different reaction conditions Ethanol conversion rate / % Acetaldehyde selectivity / % Hydrogen selectivity / % <![CDATA[The airspeed increases to 12h -1 > 32.3 84.6 99.3 <![CDATA[The airspeed is reduced to 5.2 h -1 > 65.9 86.5 99.4 The temperature rises to 320°C 53.4 88.2 99.1 The temperature is reduced to 250°C 22.9 84.6 99.2

[0099] By changing the reaction conditions, the ethanol conversion rate can reach more than 60%, and the selectivity of acetaldehyde and hydrogen can reach 86% and 99% respectively.

[0100] Reaction Example 4

[0101] Except for the reaction conditions specially indicated in Table 5, the other reaction conditions were the same as those in Reaction Example 1. The catalyst GaNi-AlOx in Preparation Example 3 was used for catalytic dehydrogenation of propanol (300°C, space velocity 10.0 h -1 ), as shown in Table 5.

[0102] Table 5 Propanol catalytic results on GaNi-AlOx catalysts prepared under different conditions (results after the reaction was stable for 3h)

[0103]

[0104] The order of feed in the catalyst preparation method has little effect on the propanol conversion, but the catalyst calcination temperature has a greater impact on the reaction results. In particular, when the calcination temperature reaches 900°C, the active center of the catalyst is partially sintered and the activity is significantly reduced. In contrast, calcination within 200°C to 800°C can maintain a higher propanol conversion rate and product selectivity.

[0105] Reaction Example 5

[0106] Comparison of catalyst stability:

[0107] The InNi-AlOx catalyst prepared in Example 1 was used for a stability test, the reaction time was 500 hours, and the reaction conditions were the same as those in Example 1. Table 6 shows a comparison of the experimental results of the present invention with those of the prior art.

[0108] Table 6 Comparison of ethanol dehydrogenation catalysts in the present invention and the prior art (ethanol concentration 98wt%, temperature 300°C, space velocity 9.8h-1)

[0109]

[0110] By comparing with the literature (Table 5), it can be found that the experimental results of the present invention have relatively outstanding substantial progress in terms of reaction activity and catalyst stability. The catalyst of the present invention is easy to prepare, the reaction conditions are milder, and it has ultra-high stability and high practicality.

[0111] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An alloy single-atom catalyst, characterized in that: The alloy single-atom catalyst comprises a carrier and an active component; The active component includes a first metal and a second metal; the first metal is dispersed in the transition metal in a single-atom form to form a single-atom alloy and is loaded on the carrier; The first metal includes one or more of gallium, tin, indium and bismuth; The second metal includes a transition metal.

2. The alloy single-atom catalyst according to claim 1, characterized in that: The mass content of the second metal in the alloy single-atom catalyst is 2% to 80%; The mass content of the first metal in the alloy single-atom catalyst is 0.1% to 20%; The loading amount of the first metal and the second metal in the alloy single-atom catalyst is 2% to 90%; The particle size of the single-atom alloy in the alloy single-atom catalyst is 2nm to 20nm.

3. The alloy single-atom catalyst according to claim 1, characterized in that: The carrier comprises aluminum oxide or silicon oxide; The second metal includes one or more of nickel, copper, cobalt and iron.

4. A method for preparing an alloy single-atom catalyst as claimed in any one of claims 1 to 3, characterized in that: The alloy single-atom catalyst is prepared by a coprecipitation method, which comprises the following steps: The first metal salt, the second metal salt and the carrier precursor are dissolved in a solvent, and a precipitant is added to form a mixed solution, followed by a coprecipitation reaction, and then the pH of the solution is adjusted to 8 to 10 to obtain a coprecipitation slurry; The coprecipitation slurry is aged, filtered, washed and dried in sequence to obtain a precipitate; The precipitate is calcined and reduced to obtain the alloy single-atom catalyst.

5. The preparation method according to claim 4, characterized in that: The first metal salt and the second metal salt are respectively selected from one or more of metal nitrates, chlorides, sulfates, phosphates and acetates; The carrier precursor includes one or more of aluminum nitrate, tetraethyl orthosilicate and sodium silicate; The precipitant includes one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, ammonia water, urea, ammonium carbonate and ammonium bicarbonate.

6. The preparation method according to claim 4, characterized in that: In the mixed solution, the concentration of metal ions in the first metal salt and the second metal salt is 0.1 mol / L to 5 mol / L, respectively, the concentration of the precipitant is 0.1 mol / L to 10 mol / L, and the concentration of the carrier precursor is 0.1 mol / L to 5 mol / L; The temperature of the coprecipitation reaction is 0°C to 80°C; The aging temperature is 40°C to 90°C; The aging time is 3h to 24h; The drying temperature is 80°C to 150°C; the drying time is 1h to 24h; The calcination temperature is 200°C to 800°C, and the calcination time is 0.5h to 20h; The reduction temperature is 300° C. to 600° C., the reduction time is 0.5 h to 6 h, and the reduction atmosphere includes one or more of hydrogen, nitrogen and argon.

7. A method for preparing an alloy single-atom catalyst as claimed in any one of claims 1 to 3, characterized in that: The alloy single-atom catalyst is prepared by a coprecipitation-impregnation method, comprising the following steps: The second metal salt and the carrier precursor are dissolved in a solvent, and a precipitant is added to form a mixed solution, followed by a coprecipitation reaction, and the pH of the solution is adjusted to 8 to 10 to obtain a coprecipitation slurry; The coprecipitation slurry is aged, filtered, washed, and dried once to obtain a precipitate; The precipitate is calcined and reduced to obtain a precursor; The precursor is immersed in a first metal salt solution, so that the first metal is dispersed in the second metal in the form of single atoms to form a single-atom alloy and loaded on a carrier, and then subjected to secondary drying, calcination and reduction in sequence to obtain the alloy single-atom catalyst.

8. The preparation method according to claim 7, characterized in that: The immersion temperature is 25°C to 35°C; the immersion time is 1h to 24h; The first metal salt and the second metal salt are respectively selected from one or more of metal nitrates, chlorides, sulfates, phosphates and acetates; The carrier precursor includes one or more of aluminum nitrate, tetraethyl orthosilicate and sodium silicate; The precipitant includes one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, ammonia water, urea, ammonium carbonate and ammonium bicarbonate; The metal ion concentration of the second metal salt in the mixed solution is 0.1 mol / L to 5 mol / L, the concentration of the precipitant is 0.1 mol / L to 10 mol / L, and the concentration of the carrier precursor is 0.1 mol / L to 5 mol / L; The metal ion concentration in the first metal salt solution is 0.1 mol / L to 5 mol / L; The temperature of the coprecipitation reaction is 0°C to 80°C; The aging temperature is 40°C to 90°C; The aging time is 3h to 24h; The temperatures of the primary drying and the secondary drying are 80°C to 150°C respectively; the times of the primary drying and the secondary drying are 1h to 24h respectively; The calcination temperature is 200°C to 800°C, and the calcination time is 0.5h to 20h; The reduction temperature is 300° C. to 600° C., the reduction time is 0.5 h to 6 h, and the reduction atmosphere includes one or more of hydrogen, nitrogen and argon.

9. Use of the alloy single-atom catalyst as claimed in any one of claims 1 to 3 in the dehydrogenation reaction of monohydric alcohol.

10. The use according to claim 9, characterized in that: The monohydric alcohol includes one or more of ethanol, n-propanol, n-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, isopropanol, isobutanol, isopentanol, isohexanol and isoheptanol; The reaction is carried out in a fixed bed reactor at a reaction pressure of 0.01 MPa to 0.5 MPa and a reaction temperature of 150° C. to 360° C. The mass space velocity of the catalytic reaction is 0.1 h -1 ~20h -1 ; There is no carrier gas in the reaction.

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