Catalyst for preparing acetic anhydride from ethanol as well as preparation method and application of catalyst

Abstract

The invention discloses a catalyst for preparing acetic anhydride from ethanol as well as a preparation method and application of the catalyst, and belongs to the field of catalysts. The catalyst comprises noble metal particles and a carrier, wherein the noble metal particles are loaded on the carrier; at least 50% of noble metal particles on the carrier have twin crystals and / or dislocations; the twin crystal and / or dislocation refers to that crystal lattice fringes of the nanoparticles are in an obvious short-distance ordered arrangement state, and the fringes slide, climb and / or are stacked and staggered. The catalyst provided by the invention improves the oxidation activity of ethanol and the selectivity of oxidizing ethanol into acetic anhydride; the method can be used for batch production of acetic anhydride catalysts prepared by ethanol oxidation.

Description

Technical Field

[0001] The present invention relates to the field of catalysts, and particularly to a catalyst for preparing acetic anhydride from ethanol, a preparation method thereof, and an application thereof. Background Art

[0002] Converting biomass into high-value-added chemicals helps alleviate humanity's dependence on fossil resources and is of greater economic value in an era of large fluctuations in oil prices. Against this backdrop, ethanol, as an important biomass molecule, has received extensive attention. Ethanol can be obtained from biomass precursors such as straw and starch and is inexpensive. It can be used as a fuel and added to gasoline as an oxygen-containing additive, and can also be converted into a variety of high-value-added chemicals through its rich reaction properties, including acetaldehyde, ethyl acetate, acetic acid, ethylene, 1,3-butadiene, etc.

[0003] Acetic anhydride is an important organic chemical raw material, mainly used for producing cellulose acetate and used as cigarette filters, photographic films, textile fibers, and celluloid plastics, etc. In addition, acetic anhydride is also an acetylation reagent in organic synthesis. The reaction of acetic anhydride with salicylic acid can be used to prepare drugs such as aspirin. In addition, acetic anhydride can also be used for the preparation of dyes.

[0004] At present, acetic anhydride is usually synthesized by the carbonylation of methyl acetate or the ketene method: for example, Patent CN101279294A discloses a rhodium catalyst for the carbonylation of methyl acetate to acetic anhydride. It is a cis-dicarbonylrhodium cationic structure catalyst formed by the action of rhodium carbonyl and a ligand, which is a chelated square planar complex. Its cation part is a cis-dicarbonylrhodium cation, and the ligand is acetylmorpholine. In the reaction of carbonylation of methyl acetate to acetic anhydride, this catalyst not only exhibits good thermal stability but also maintains good catalytic activity. At the same time, it can enhance the solubility of catalyst species in the reaction system, avoid adding acetic acid and / or acetic anhydride as catalyst solvents in industrial production, effectively reduce the flash evaporation and evaporation load, and improve the production efficiency of carbonylation to acetic anhydride. However, the carbonylation method requires high-purity carbon monoxide and high pressure, which has high requirements for equipment. At the same time, the rhodium-based catalyst is expensive, bringing cost pressure. Patent CN101006041A discloses a method for co-producing acetic anhydride and acetate esters, including: pyrolyzing acetic acid at an elevated temperature to prepare a first ketene stream, which is a vapor-phase stream including ketene, acetic acid, and water; cooling the first ketene stream to thereby condense acetic acid and water, thus producing (i) a weak acid-containing water stream and (ii) a ketene feed stream; feeding the ketene feed stream to an acetic anhydride reactor, where ketene reacts with acetic acid to produce acetic anhydride; simultaneously with step (c), feeding the weak acid-containing water stream to an esterification reactor, where acetic acid in the weak acid stream reacts with an organic alcohol to produce acetate esters. However, when preparing ketene by this method, high temperature is required, resulting in high energy consumption. In addition, special reactors are needed, resulting in high costs. And the yield of acetic anhydride in the product is low. Patent CN112441901A discloses a method for synthesizing acetic anhydride. This synthesis method uses acetyl chloride and glacial acetic acid as raw materials, including steps such as packing fillers, reflux reaction, first-stage vacuum distillation, and second-stage vacuum distillation, to achieve the synthesis of acetic anhydride from acetyl chloride and acetic acid at low temperature and normal pressure. Compared with the traditional acetic anhydride production method, this synthesis method has mild reaction conditions and high safety factors. At the same time, no catalyst is required, avoiding the separation and regeneration of the catalyst and reducing production costs. The one-time yield of acetic anhydride reaches 96-99%, and the purity reaches 99.2-99.6%. At the same time, pure hydrochloric acid with a content > 32% can be produced, increasing the product structure and market competitiveness of the industrial chain, and no three wastes are generated during the whole production process, which is suitable for industrial promotion and application. However, the total cost of acetyl chloride and acetic acid in this method has exceeded the cost of acetic anhydride, so the added value of the solid product is negative, and it can only be used for special high-purity experiments and has no value for large-scale production. Summary of the Invention

[0005] The present invention provides a catalyst for preparing acetic anhydride from ethanol, a preparation method thereof, and an application thereof. The special noble metal catalyst prepared by the method of the present invention has extremely high ethanol oxidation activity, and can directly oxidize ethanol to prepare acetic anhydride in one step. The process is simple, and the catalyst cost is low, which is suitable for the industrial production of acetic anhydride.

[0006] The present invention first provides a catalyst, which comprises noble metal particles and a carrier, and the noble metal particles are loaded on the carrier; at least 50% of the noble metal particles on the carrier have twins and / or dislocations; The twins and / or dislocations refer to the state in which the lattice fringes of nanoparticles show obvious short-range ordered arrangement, and the fringes undergo slip, climb, and / or stacking faults.

[0007] The twin is: a orientation relationship in which two crystals (or two parts of a crystal) form a mirror symmetry along a common crystal plane (i.e., a specific orientation relationship) that can be observed on an electron microscope. A part of the atoms inside the crystal are symmetrically arranged along a certain specific crystal plane (called the twin plane) or crystal direction (called the twin direction), forming a region that is mirror-symmetric with the original crystal. The electron microscope can observe that two crystals (or two parts of a crystal) form a mirror-symmetric orientation relationship along a common crystal plane (i.e., a specific orientation relationship) (in a transmission electron microscope, the lattice fringes of the crystal remain unchanged, but the interface is symmetrically arranged).

[0008] The dislocation is: an internal microscopic defect of a crystal material, that is, a local irregular arrangement (crystallographic defect) of the nanoparticles in the crystal, which is manifested as the deformation of the lattice fringes inside the nanoparticles in an electron microscope. A line defect inside the crystal, which is a line defect in the crystal, is manifested as a local discontinuity in the atomic arrangement. The lattice atoms are locally misaligned along a line (the dislocation line), and the core is a linear distortion region. In a transmission electron microscope, the line defect will show structures such as local lattice fringe discontinuity, contrast change, and dislocation loops.

[0009] Both twins and dislocations are defects in crystals. However, twins are a type of plane defect in crystals, manifested as a part of the crystal being arranged in mirror symmetry with the original crystal, while dislocations are manifested as local discontinuities in the atomic arrangement, and the core is a linear distortion region.

[0010] In the above catalyst, 60% - 90% of the noble metal particles on the carrier have twins and / or dislocations; Preferably, 65% - 85% of the noble metal particles on the carrier have twins and / or dislocations.

[0011] In the above catalyst, the average particle diameter of the noble metal particles is 2 nm - 10 nm; specifically, it can be 6.2 nm, 4.3 nm, 5.7 nm, or 4.5 nm; The composition of the noble metal particles is one or more of platinum, palladium, gold, ruthenium and iridium; The carrier is any one of cerium oxide, alumina, titanium oxide, barium sulfate, silica, zirconia and activated carbon; specifically, it can be an α-Al2O3 carrier, a γ-Al2O3 carrier, zirconia or silica; Preferably, the surface acid amount of the carrier is less than 50 μmol / g.

[0012] The present invention also provides a preparation method of the above catalyst, which is Method 1 or Method 2: Method 1 includes the following steps: S1. Mix the carrier, the noble metal precursor and the dispersion medium; S2. Adjust the pH value of the mixture in S1 to 1-11, control the temperature and stir to obtain a second mixture; S3. Perform solid-liquid separation on the second mixture, and dry the obtained solid to obtain a third mixture; S4. Calcinate the third mixture to obtain the catalyst; The calcination is carried out in an atmosphere containing acetic anhydride or acetic acid, or first calcined in a hydrogen-containing atmosphere and then calcined in an atmosphere containing acetic anhydride or acetic acid; Method 2 includes the following steps: (1) Mix the carrier, the noble metal precursor and the dispersion medium to obtain mixture 1; (2) Heat the mixture 1 and add a reducing agent, and stir to obtain mixture 2; (3) Perform solid-liquid separation on the mixture 2, and dry the obtained solid to obtain mixture 3; (4) Calcinate the mixture 3 to obtain the catalyst; The calcination is carried out in an atmosphere containing acetic anhydride or acetic acid.

[0013] In the above preparation method, the atmosphere containing acetic anhydride or acetic acid is a nitrogen or air atmosphere containing acetic anhydride or acetic acid; the hydrogen-containing atmosphere is a nitrogen or air atmosphere containing hydrogen; The total pressure of the atmosphere containing acetic anhydride or acetic acid is normal pressure, and the partial pressure of acetic anhydride or acetic acid is 0.1 kPa-15 kPa, specifically 1 kPa or 1.5 kPa; The total pressure of the hydrogen-containing atmosphere is normal pressure, and the volume percentage of hydrogen is 5%-100%, specifically 20%.

[0014] In the above preparation method, in Method 1, the calcination is carried out in a hydrogen-containing atmosphere at a temperature of 373 K to 823 K (specifically, it can be 673 K, 573 K or 523 K); the calcination time is 30 min to 6 h (specifically, it can be 0.5 h or 2 h). In step S2 of Method 1, the pH can specifically be 6 - 11.

[0015] In the above preparation method, in both Method 1 and Method 2, the carrier is any one of cerium oxide, alumina, titanium oxide, barium sulfate, silica, zirconia and activated carbon; The noble metal precursor is at least one of sodium chloroplatinate, ammonium hexachloroplatinate, potassium hexachloroplatinate, sodium hexachloroplatinate, platinum tetrachloride, tetraammineplatinum nitrate, platinum nitrate, chloroplatinic acid, potassium chloroplatinate, sodium chloroplatinate, palladium chloride, palladium nitrate, tetraamminepalladium nitrate, palladium acetate, sodium chloropalladate, chloroauric acid, gold chloride, gold acetate, gold bromide and trichloropyridine gold; The dispersion medium is water and / or hydrochloric acid solution; specifically, the concentration of the hydrochloric acid solution is 25wt% - 38wt%; The mass ratio of the noble metal contained in the noble metal precursor to the mass of the carrier is 1:5 to 100; specifically, it can be 1:50, 1:13.6, 1:14, 1:66.7; The mass ratio of the noble metal precursor to the dispersion medium is 1:1 to 50; specifically, it can be 1:5, 1:6 or 1:18; The drying temperature is 313 K to 453K (40℃ to 180℃), specifically, it can be 333 K or 393 K; The calcination temperature is 373 K to 823 K (100℃ to 550℃); the calcination time is 30 min to 6 h.

[0016] Specifically, the calcination temperature is 400 K, 573 K or 523 K, and the calcination time is 2 h; In the above preparation method, in Method 1, the substance used to adjust the pH value is any one of sodium carbonate, hydrochloric acid solution, sodium hydroxide, sodium bicarbonate, sodium borohydride and ammonia water; In step S2, the stirring temperature is 300 K to 390 K, and the time is 0.5 h to 36 h; In Method 2, the reducing agent is at least one of sodium borohydride, vitamin C, formic acid, formaldehyde, citric acid, CO polyvinylpyrrolidone and hydrazine hydrate; The molar ratio of the noble metal precursor to the reducing agent is 1:4 to 500; In step (2), the heating temperature is 288 K to 373 K (15℃ to 100℃), specifically, it can be 353 K.

[0017] In the above preparation method, there is a step of cooling under the protection of an inert gas after calcination; specifically, the inert gas is nitrogen.

[0018] The present invention further provides the application of the above catalyst in the preparation of acetic anhydride by the directional conversion of ethanol.

[0019] Finally, the present invention provides a method for the directional conversion of ethanol to prepare acetic anhydride, which includes the following steps: passing a nitrogen-oxygen mixed dispersion gas containing ethanol gas through a fixed bed layer filled with the above catalyst.

[0020] In the above method, the reaction temperature of the fixed bed layer is 363 K - 423 K; In the mixed dispersion gas, the total atmosphere pressure is normal pressure, wherein the partial pressure of ethanol is 0.5 - 5 kPa, the partial pressure of oxygen is 6 kPa - 60 kPa, and the rest is balanced by nitrogen.

[0021] In the above method, the yield of acetic anhydride prepared by the conversion of ethanol is 20% - 70%.

[0022] The present invention has the following beneficial effects: (1) At least 50% of the noble metal particles of the catalyst prepared by the present invention show twins and dislocations; the noble metal particles have good dispersion on the carrier; (2) The catalyst prepared by the present invention improves the ethanol oxidation activity and the selectivity of ethanol oxidation to acetic anhydride; (3) The preparation method of the catalyst of the present invention has the characteristics of batch repeatability and easy industrial scale-up, and can be used for the batch production of the catalyst for ethanol oxidation to prepare acetic anhydride. Description of the Drawings

[0023] Figure 1 TEM photograph of the catalyst prepared in Example 1.

[0024] Figure 2 TEM photograph of the catalyst prepared in Comparative Example 1.

[0025] Figure 3 Comparison of TEM images of nanometer particles containing twins and dislocations; among them, Figure 3 a - c are the catalysts prepared in Examples 2 - 4, and d is the catalyst prepared in Comparative Example 1.

[0026] Figure 4 Schematic diagram of the result processing of particle size statistics.

[0027] Figure 5 Schematic diagram of the result processing of the statistics of noble metal particles, twins, dislocations and ordinary particles. Detailed Embodiments

[0028] The present invention will be further described in detail below in conjunction with specific embodiments. The provided embodiments are only for clarifying the present invention and not for limiting the scope of the present invention.

[0029] In the following embodiments, the experimental methods are all conventional methods unless otherwise specified.

[0030] The materials, reagents, etc. used in the following embodiments can all be obtained from commercial sources unless otherwise specified.

[0031] The α-Al2O3 support, γ-Al2O3 support, zirconia, and silica in the following embodiments are all purchased from Alfa Aesar, and the surface acid amount is less than 50 μmol / g.

[0032] In the following embodiments and comparative examples, the pressures for treatment, calcination, roasting, etc. are all atmospheric pressure.

[0033] Example 1 0.067 g of PdCl2 was dispersed in 1 mL of concentrated hydrochloric acid (38 wt%), heated to complete dissolution of the powder at 60 °C, and 2 g of α-Al2O3 support was added. Then 1.2 g of Na2CO3 was added to adjust the pH to 10 - 11, and the mixture was stirred at 303 K for 16 h. The obtained mixture was centrifuged, and the resulting precipitate was washed 4 times with deionized water and 3 times with 0.1 M NaOH solution to remove Cl ions, and then washed with deionized water and ethanol, and dried in vacuo at 333 K. The obtained sample was calcined in a nitrogen atmosphere containing 20% (v / v) hydrogen at 673 K for 2 h, and then switched to a mixture of acetic anhydride / nitrogen (acetic anhydride partial pressure 1 kPa, the rest balanced with nitrogen), roasted at 400 K for 2 h, and cooled under nitrogen protection to obtain the catalyst. The TEM image of this catalyst is shown in Figure 1 。

[0034] Approximately 82% of the noble metal particles in this catalyst contain twin crystals and defective particles, and the average particle size of the noble metal particles is 6.2 nm.

[0035] 75 mg of the catalyst prepared above was placed in a fixed-bed reactor, and an atmospheric-pressure mixed gas of ethanol-oxygen-nitrogen was introduced at 393 K, where the partial pressure of ethanol was 2 kPa, the partial pressure of oxygen was 18 kPa, and the partial pressure of nitrogen was 80 kPa. In the fixed-bed reactor, after the reaction stabilized (after about 2 h), acetic anhydride could be continuously prepared by oxidizing ethanol, and the yield of acetic anhydride was 65%.

[0036] Comparative Example 1 0.067 g of PdCl2 was dispersed in 1 mL of concentrated hydrochloric acid (38 wt%), heated at 60 °C until the powder was completely dissolved, 2 g of α-Al2O3 support was added, and 1.2 g of Na2CO3 was added, and stirred at 303 K for 16 h. The resulting mixture was centrifuged, the precipitate was washed 4 times with deionized water and 3 times with 0.1 M NaOH solution to remove Cl ions, and then washed with deionized water and ethanol, and the sample was dried in vacuo at 333 K. The obtained sample was treated in a nitrogen atmosphere containing 20% (v / v) hydrogen at 673 K for 2 h, and cooled under nitrogen protection to obtain a catalyst, and the average particle size of the noble metal particles was 6.3 nm. The TEM image of this catalyst is shown in Figure 2 。

[0037] The twin and defective particles in the noble metal particles of this catalyst accounted for about 15% of the total particle amount.

[0038] 75 mg of the catalyst prepared above was placed in a fixed-bed reactor, and an atmospheric-pressure mixed gas of ethanol-oxygen-nitrogen was introduced at 393 K, where the partial pressure of ethanol was 2 kPa, the partial pressure of oxygen was 18 kPa, and the partial pressure of nitrogen was 80 kPa. Ethanol was oxidized to prepare acetic anhydride, and the yield of the obtained acetic anhydride was 11%.

[0039] Example 2 2 g of γ-Al2O3 support was mixed with 0.390 g of chloroplatinic acid hexahydrate, 2 mL of water was added, stirred evenly, 2 g of Na2CO3 was added, and the pH was adjusted to 10; stirred and heated at 383 K for 16 h. The resulting mixture was centrifuged, the precipitate was washed 4 times with deionized water and 3 times with 0.1 M NaOH solution to remove Cl ions, and then washed with deionized water and ethanol, and the sample was dried in vacuo at 333 K. The obtained sample was calcined in a nitrogen atmosphere containing 20% (v / v) hydrogen at 573 K for 2 h, and then switched to a mixed gas of acetic anhydride / nitrogen (the partial pressure of acetic anhydride was 1 kPa, and the rest was balanced with nitrogen), and calcined at 573 K for 2 h, and cooled under nitrogen protection to obtain a catalyst. The twin and defective particles in the noble metal particles of this catalyst accounted for about 67% of the total particle amount, and the average particle size of the noble metal particles was 4.3 nm.

[0040] 75 mg of the above catalyst was placed in a fixed-bed reactor, and an atmospheric-pressure mixed gas of ethanol-oxygen-nitrogen was introduced at 393 K, where the partial pressure of ethanol was 3 kPa, the partial pressure of oxygen was 18 kPa, and the partial pressure of nitrogen was 80 kPa. Ethanol was oxidized to prepare acetic anhydride, and the yield of the obtained acetic anhydride was 28%.

[0041] Example 3 2 g of zirconia support was mixed with 0.129 g of chloroauric acid and 0.19 g of sodium chloropalladate, 2 mL of water was added, 100 mg of polyvinylpyrrolidone (PVP) was added, and the mixture was stirred evenly. It was heated to 353 K, and 400 mg of vitamin C (VC) was added, and it was stirred for 8 h. The obtained mixture was centrifuged, the precipitate was washed 4 times with deionized water, and the precipitate was washed 3 times with 0.1 M NaOH solution to remove Cl ions, and then washed with deionized water and ethanol, and the sample was dried in vacuum at 333 K. The obtained sample was calcined in a nitrogen / acetic acid mixed gas (acetic acid partial pressure was 1 kPa) at 573 K for 2 h to obtain a catalyst. The twin and defective particles in the noble metal particles of this catalyst accounted for about 70% of the total particle amount, and the average particle size of the noble metal particles was 5.7 nm.

[0042] 75 mg of the above catalyst was taken and placed in a fixed-bed reactor. An atmospheric-pressure mixed gas of ethanol-oxygen-nitrogen was introduced at 393 K, in which the ethanol partial pressure was 2 kPa, the oxygen partial pressure was 18 kPa, and the nitrogen partial pressure was 80 kPa. Ethanol was oxidized to prepare acetic anhydride, and the yield of the obtained acetic anhydride was 45%.

[0043] Example 4 2 g of silica support was mixed with 0.6 mL of 15 wt% aqueous solution of tetraamminepalladium nitrate, the pH was adjusted to 6 with a very small amount of hydrochloric acid, and it was stirred at 303 K for 120 min to mix evenly. The solid-liquid separation and drying were carried out at 393 K. The obtained sample was calcined in a hydrogen / nitrogen mixed gas (hydrogen partial pressure was 20 kPa, balanced with nitrogen) at 523 K for 0.5 h, and then switched to an acetic acid / nitrogen (acetic acid partial pressure was 1.5 ka, and the rest was balanced with nitrogen) mixed gas, and it was calcined at 523 K for 2 h and cooled under nitrogen protection to obtain a catalyst. The average particle size of the noble metal particles of this catalyst was 4.5 nm, and the twin and defective particles accounted for about 63% of the total particle amount.

[0044] 50 mg of the above catalyst was taken and placed in a fixed-bed reactor. An atmospheric-pressure mixed gas of ethanol-oxygen-nitrogen was introduced at 393 K, in which the ethanol partial pressure was 2 kPa, the oxygen partial pressure was 48 kPa, and the nitrogen partial pressure was 50 kPa. Acetic acid was oxidized to prepare acetic anhydride, and the yield of the obtained acetic anhydride was 53%.

[0045] Comparative Example 2 2 g of silica support was mixed with 10 mL of 15 wt% aqueous solution of tetraamminepalladium nitrate, and the pH was adjusted to 6 with a very small amount of hydrochloric acid. The mixture was stirred at 303 K for 120 min to be well mixed, and then solid-liquid separation was carried out and dried at 393 K. The obtained sample was treated with a 20% (v / v) hydrogen / nitrogen mixture at 400 K for 0.5 h and cooled under nitrogen protection to obtain the catalyst. The average particle size of the noble metal particles of this catalyst was 4.7 nm, and the particles with twins and defects accounted for about 15% of the total particle amount.

[0046] 50 mg of the above catalyst was taken and placed in a fixed-bed reactor. An atmospheric-pressure mixture of ethanol-oxygen-nitrogen was introduced at 393 K, where the partial pressure of ethanol was 2 kPa, the partial pressure of oxygen was 48 kPa, and the partial pressure of nitrogen was 50 kPa. Ethanol was oxidized to prepare acetic anhydride, and the yield of the obtained acetic anhydride was 7.5%.

[0047] Figure 3 For the comparison of TEM images of nanoparticles containing twins and dislocations; from Figure 3 It can be seen that twins are formed by a part of the atoms inside the crystal arranging symmetrically along a certain specific crystal plane (called the twin plane) or crystal direction (called the twin direction), forming a region that is mirror-symmetric with the original crystal. In the electron microscope, two crystals (or two parts of a crystal) can be observed to form a mirror-symmetric orientation relationship along a common crystal plane (i.e., a specific orientation relationship). (In the transmission electron microscope, the lattice fringes of the crystal remain unchanged, but the interface is symmetrically arranged). Dislocations are line defects inside the crystal, which are line defects in the crystal, manifested as local discontinuity of the atomic arrangement. The lattice atoms are locally misaligned along a line (the dislocation line), and the core is a linear distortion region. In the transmission electron microscope, line defects will show structures such as local discontinuity of lattice fringes, contrast change, and dislocation loops.

[0048] In the above examples and comparative examples, the test method for the average particle size of the noble metal particles of the catalyst was as follows: The sample was subjected to transmission electron microscopy analysis. Randomly select 8 non-overlapping and widely dispersed viewing areas of catalyst particles (magnification factor of 40,000 - 200,000 times), and randomly select 50 (a total of 400) noble metal particles in each area. The particle sizes were statistically analyzed, and finally the average value of the particle sizes was taken as the average particle size of the noble metal particles. Figure 4 It is a TEM image of the particle size statistics of Example 1.

[0049] The statistical method for the proportion of particles with twins and defects was as follows: At an electron microscope magnification of more than 100,000, 15 - 20 TEM photos were selected. Randomly select 10 - 15 noble metal particles in each area, and statistically analyze whether there are twins and dislocations. A total of 200 particles were counted, and the percentage of the total number of particles with twins and dislocations in the total number of particles was statistically analyzed. Figure 5A TEM image for the statistics of twins, dislocations of noble metal particles and ordinary particles in Example 1.

[0050] The above-mentioned lattice defects and particle sizes of noble metal particles were detected by a high-resolution aberration-corrected electron microscope. The aberration-corrected electron microscope analysis was carried out on a JEM-ARM300F or Philips Tecnai F30 FEG-TEM electron microscope purchased from JEOL Ltd.

Claims

1. A catalyst comprising noble metal particles and a carrier, wherein the noble metal particles are loaded on the carrier; at least 50% of the noble metal particles on the carrier have twins and / or dislocations; The twins and / or dislocations refer to the fact that the lattice fringes of the nanoparticles present an obvious short-range ordered arrangement state, and the fringes undergo slip, climb and / or stacking faults.

2. The catalyst according to claim 1, characterized in that: 60% to 90% of the noble metal particles on the carrier have twins and / or dislocations; Preferably, 65% to 85% of the precious metal particles on the carrier have twins and / or dislocations.

3. The catalyst according to claim 1 or 2, characterized in that: The average particle diameter of the noble metal particles is 2 nm to 10 nm; The precious metal particles are composed of one or more of platinum, palladium, gold, ruthenium and iridium; The carrier is any one of cerium oxide, aluminum oxide, titanium oxide, barium sulfate, silicon oxide, zirconium oxide and activated carbon; Preferably, the surface acidity of the carrier is less than 50 μmol / g.

4. The method for preparing the catalyst according to any one of claims 1 to 3, which is method 1 or method 2: The method 1 comprises the following steps: S1, mixing a carrier, a noble metal precursor and a dispersion medium; S2, adjusting the pH value of the mixture in S1 to 1-11, controlling the temperature and stirring to obtain a second mixture; S3, performing solid-liquid separation on the second mixture, and drying the obtained solid to obtain a third mixture; S4, calcining the third mixture to obtain the catalyst; The calcination is carried out in an atmosphere containing acetic anhydride or acetic acid, or firstly in an atmosphere containing hydrogen, and then in an atmosphere containing acetic anhydride or acetic acid for calcination; The second method comprises the following steps: (1) mixing a carrier, a noble metal precursor and a dispersion medium to obtain a mixture 1; (2) heating the mixture 1, adding a reducing agent, and stirring to obtain a mixture 2; (3) subjecting the mixture 2 to solid-liquid separation, and drying the obtained solid to obtain a mixture 3; (4) calcining the mixture 3 to obtain the catalyst; The calcination is performed in an atmosphere containing acetic anhydride or acetic acid.

5. The preparation method according to claim 4, characterized in that: In the method 1 and the method 2, the carrier is any one of cerium oxide, aluminum oxide, titanium oxide, barium sulfate, silicon oxide, zirconium oxide and activated carbon; The noble metal precursor is at least one of sodium chloroplatinite, ammonium hexachloroplatinate, potassium hexachloroplatinate, sodium hexachloroplatinate, platinum tetrachloride, tetraammine platinum nitrate, platinum nitrate, chloroplatinic acid, potassium chloroplatinate, sodium chloroplatinate, palladium chloride, palladium nitrate, tetraammine palladium nitrate, palladium acetate, sodium chloropalladate, chloroauric acid, gold chloride, gold acetate, gold bromide and gold trichloride; The dispersion medium is water and / or hydrochloric acid solution; The mass ratio of the precious metal contained in the precious metal precursor to the mass ratio of the carrier is 1:5-100; The mass ratio of the noble metal precursor to the dispersion medium is 1:1-50; The drying temperature is 313 K ~ 453 K; The calcination temperature is 373 K to 823 K; the calcination time is 30 min to 6 h.

6. The preparation method according to claim 4 or 5, characterized in that: In the method 1, the substance used to adjust the pH value is any one of sodium carbonate, hydrochloric acid solution, sodium hydroxide, sodium bicarbonate, sodium borohydride and ammonia water; In step S2, the stirring temperature is 300 K to 390 K, and the stirring time is 0.5 h to 36 h; In the second method, the reducing agent is at least one of sodium borohydride, vitamin C, formic acid, formaldehyde, citric acid, CO polyvinyl pyrrolidone and hydrazine hydrate; The molar ratio of the noble metal precursor to the reducing agent is 1:4-500; In step (2), the heating temperature is 288 K~373 K.

7. Use of the catalyst according to any one of claims 1 to 3 in the directional conversion of ethanol to produce acetic anhydride.

8. A method for preparing acetic anhydride by directional conversion of ethanol, comprising the following steps: passing a nitrogen-oxygen mixed dispersed gas containing ethanol gas through a fixed bed layer containing the catalyst according to any one of claims 1 to 3.

9. The method according to claim 8, characterized in that: The reaction temperature of the fixed bed is 363 K ~ 423 K; In the mixed dispersed gas, the total atmosphere pressure is normal pressure, wherein the ethanol partial pressure is 0.5-5 kPa, the oxygen partial pressure is 6 kPa-60 kPa, and the rest is nitrogen balance.

10. The method according to claim 9, characterized in that: The yield of acetic anhydride prepared by converting ethanol is 20%~70%.

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