Composite metal oxide catalyst as well as preparation method and application thereof

Abstract

The invention provides a composite metal oxide catalyst and a preparation method and application thereof. The composite metal oxide catalyst comprises a compound with the chemical composition of AxDyEzOn, A comprises at least one of Cu, Fe and Ni, D comprises at least one of Si, Al, Mg and Zr, E comprises at least one of Al, Fe, Zn and Mg, A, D and E are different elements, x, y, z and n represent the atomic ratio of the elements, the value of x is 1-5, y is larger than 0, z is larger than 0, and n is larger than 0. The composite metal oxide catalyst has the advantages of high activity, high stability and cost, the conversion rate of dimethyl oxalate and the yield of ethanol can be remarkably improved, and the service life of the catalyst is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of petrochemical industry, and particularly relates to a composite metal oxide catalyst and a preparation method and application thereof. BACKGROUND

[0002] Ethanol, as an important chemical raw material and energy fuel, is widely used in chemical industry, medical and health, food industry, agricultural production and other fields. With the adjustment of global energy structure and the deepening of low-carbon policy, oxalic acid dimethyl ester hydrogenation method has become an important research direction for preparing ethanol because of stable raw material source. In the process of preparing ethanol by hydrogenation of oxalic acid dimethyl ester, the catalyst plays a decisive role, and its catalytic activity and stability directly determine the conversion rate of oxalic acid dimethyl ester. Therefore, optimizing the catalyst and its preparation method is a prerequisite for ensuring high-quality ethanol production.

[0003] The existing catalyst depends on rare metal resources, and the production cost is high, which limits its large-scale application. The conversion rate of oxalic acid dimethyl ester and the selectivity of ethanol are low in reaction performance, resulting in a high proportion of by-products, which further affects the product purity. In addition, the catalyst is quickly deactivated due to sintering and carbon deposition in a long time reaction, and the stability is insufficient and needs to be frequently replaced.

[0004] Therefore, it is crucial to develop a composite metal oxide catalyst with high activity, high stability and cost advantage. SUMMARY

[0005] The present application provides a composite metal oxide catalyst, which has high activity, high stability and cost advantage.

[0006] The present application also provides a preparation method of the above-mentioned composite metal oxide catalyst, which is used for preparing the above-mentioned composite metal oxide catalyst.

[0007] The present application also provides a preparation method of ethanol, which comprises the step of preparing ethanol by catalytic hydrogenation using oxalic acid dimethyl ester as raw material.

[0008] The first aspect of the present application provides a composite metal oxide catalyst, comprising: a compound with a chemical composition of A x D y E z O n , wherein A comprises at least one of Cu, Fe and Ni, D comprises at least one of Si, Al, Mg and Zr, E comprises at least one of Al, Fe, Zn and Mg, A, D and E are different elements, x, y, z and n represent the atomic ratio of each element, the value of x is 1-5, y>0, z>0 and n>0.

[0009] The catalyst as described above, wherein x=3, y is 3-15, and z is 1-5.

[0010] The catalyst as described above, wherein x=3, y is 3.2-10, and z is 1.5-4; and / or,

[0011] The particle size of the catalyst is 0.10-0.15 mm, the pore size is 2-5 nm, and the specific surface area is 50-100 m 2 / g.

[0012] The second aspect of the present application provides a preparation method of a composite metal oxide catalyst, comprising the following steps:

[0013] 1) adjusting the pH value of a mixed solution to be in the range of 10-12 by using a pH regulator to form a precipitate; the mixed solution comprises an A source, a D source and an E source;

[0014] 2) drying the precipitate to obtain a catalyst precursor;

[0015] 3) calcining the catalyst precursor to obtain a composite metal oxide catalyst.

[0016] The preparation method as described above, wherein the step 1) comprises: first adding the mixed solution into the pH regulator, and continuously adding the pH regulator while stirring until the pH value of the system is in the range of 10-12; and / or,

[0017] The pH regulator comprises at least one of an aqueous ammonia solution, an aqueous sodium hydroxide solution and an aqueous potassium hydroxide solution, and the mass concentration of the pH regulator is 10%-20%.

[0018] The preparation method as described above, wherein before the drying in the step 2), the method further comprises: performing suction filtration and washing on the precipitate until the pH value of the washing liquid is 7, and the washing liquid is at least one of methanol, ethanol and water; and / or,

[0019] After the calcination in the step 3), the method further comprises: performing surface pickling or alkali treatment on the catalyst, the acid for the pickling is at least one of hydrochloric acid, nitric acid and citric acid, and the alkali for the alkali treatment is at least one of an aqueous sodium hydroxide solution, an aqueous sodium carbonate solution and aqueous ammonia.

[0020] The preparation method as described above, wherein in the mixed solution, the total mass concentration of the A source, the D source and the E source is 10%-15%, and the solvent in the mixed solution is at least one of methanol, ethanol and water; and / or,

[0021] The A source comprises at least one of a chloride salt, a nitrate salt, and a sulfate salt of element A, the D source comprises at least one of a chloride salt, a nitrate salt, and a sulfate salt of element D, and the E source comprises at least one of a chloride salt, a nitrate salt, and a sulfate salt of element E.

[0022] The preparation method as described above, wherein the drying is microwave drying, the temperature is 80-150 DEG C, and the time is 12-24 h; and / or,

[0023] The calcination temperature is 400-700 DEG C, and the time is 3-5 h.

[0024] The third aspect of the present application provides a preparation method of ethanol, comprising: using dimethyl oxalate as a raw material to prepare ethanol by catalytic hydrogenation, wherein the catalyst in the catalytic hydrogenation comprises the composite metal oxide catalyst according to any one of claims 1-3 or the composite metal oxide catalyst obtained by the preparation method according to any one of claims 4-8.

[0025] The preparation method as described above, wherein the molar ratio of hydrogen to dimethyl oxalate is 1:100-1:300, the reaction temperature is 200-250 DEG C, the reaction pressure is 2.5-3.5 MPa, the liquid hourly space velocity is 0.5-5 h -1 .

[0026] The composite metal oxide catalyst of the present application can reduce the cost of the catalyst by using a non-noble metal instead of a noble metal, and can enhance the hydrogenolysis ability of the C-O bond and the C=O bond of dimethyl oxalate and inhibit the occurrence of side reactions by using the electronic effect and synergistic effect between different metals, thereby achieving the technical effect of a composite metal oxide catalyst with high activity, high stability, and cost advantage. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The pore size structure diagram of the catalyst of Example 2 Cu3Zr 3.25 Zn 1.97 O 11.47 The life evaluation diagram of the catalyst;

[0028] Figure 2 The pore size structure diagram of the catalyst of Example 2 Cu3Zr 3.25 Zn 1.97 O 11.47 The pore size structure diagram of the catalyst of Example 2 Cu3Zr

[0029] Figure 3 The pore size structure diagram of the catalyst of Example 2 Cu3Zr 3.25 Zn 1.97 O 11.47 The specific surface area data diagram of the catalyst of Example 2 Cu3Zr

[0030] Figure 4 The specific surface area data diagram of the catalyst of Example 2 Cu3Zr3.25 Zn 1.97 O 11.47 SEM-EDS image of the catalyst. DETAILED DESCRIPTION

[0031] For the purposes of the present application, the technical solutions and advantages thereof will be more apparent from the following detailed description of the embodiments of the present application, which will be described in a clear and complete manner with reference to the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0032] Ethanol, as an important chemical raw material and potential energy, its demand is growing with the low-carbon adjustment of energy structure. Among them, oxalic acid dimethyl ester hydrogenation method has broad development prospects due to its stable raw material supply. In this process, the catalyst plays a key role, and its activity, selectivity and stability are the key to determine the success of the reaction.

[0033] The existing catalysts generally have problems of insufficient activity, poor stability, high cost and the like. The inventors have conducted research thereon and believe that by screening specific metal combinations, using the electronic effect and synergistic effect between different metals, the hydrogenolysis ability of the catalyst to the C-O bond and C=O bond of oxalic acid dimethyl ester can be enhanced, while the side reactions are inhibited, and the activity of the catalyst is improved; by controlling the pH value of the solution in the coprecipitation process, ensuring that different metal salts are uniformly precipitated simultaneously under the action of the precipitant, the difference in catalytic activity caused by uneven metal distribution can be avoided; by using non-noble metals to replace noble metals, combining with the coprecipitation method to simplify the preparation process, the cost of the catalyst can be effectively reduced, and at the same time, the thermal stability and carbon deposition resistance of the catalyst are further optimized through the calcination process, so that it meets the needs of industrial continuous reaction.

[0034] Based on this, the first aspect of the present application provides a composite metal oxide catalyst, comprising: a compound with a chemical composition of A x D y E z O n , wherein A includes at least one of Cu, Fe and Ni, D includes at least one of Si, Al, Mg and Zr, E includes at least one of Al, Fe, Zn and Mg, A, D and E are different elements, x, y, z and n represent the atomic ratio of each element, the value of x is 1-5, y>0, z>0 and n>0.

[0035] The application forms a composite metal oxide catalyst with stable structure by combining three metal elements A, D and E in a specific atomic ratio. Metal A serves as an active metal responsible for providing core sites for hydrogenation reaction; metal D serves as a structure promoter that can effectively improve the specific surface area and pore structure of the catalyst carrier and prevent sintering of the active component; and metal E serves as an electronic promoter that can effectively enhance the selectivity of the active sites to the target product ethanol by regulating the electronic environment of the active sites. In particular, the atomic ratio x of A is limited to the range of 1-5, which is verified by experiments to be able to well balance the synergistic effect of the metal active component and the physical stability of the carrier structure. The design of the composite metal oxide catalyst can achieve the effect of synergistically improving the activity, selectivity and stability of the catalyst, thereby significantly improving the conversion rate of dimethyl oxalate and the yield of ethanol, and prolonging the service life of the catalyst.

[0036] In a specific embodiment, x=3, y is 3-15, and z is 1-5. This range is verified by experiments to ensure sufficient catalyst active sites, improve reaction conversion rate, effectively prevent aggregation and growth of active metals, and improve the stability of the structure and the dispersion of the active sites when x=3, y is 3-15, and z is 1-5. The current range perfectly balances the catalytic efficiency of the active component and the physical stability of the carrier structure, which is the key to achieving good synergistic effect.

[0037] Further, x=3, y is 3.2-10, and z is 1.5-4. The limitation of this parameter range is based on experimental data verification, and y of 3.2-10 can ensure the strength of the catalyst carrier structure, improve the mass transfer efficiency, and promote the dispersion of metal element A to improve the active site density. Z of 1.5-4 can fine-tune the reaction path to inhibit the generation of by-products.

[0038] In addition, the particle size of the catalyst is 0.10-0.15mm, the pore size is 2-5nm, and the specific surface area is 50-100m 2 / g. The small particle size of 0.10-0.15mm can ensure that the reactants and products can quickly diffuse inside the catalyst particles, avoiding internal blockage, wherein 0.10mm is the minimum value of the catalyst particle size and 0.15mm is the maximum value of the catalyst particle size; the concentrated pore size of 2-5nm can accurately guide the reactant molecules to enter and contact with the active sites, while being beneficial to the desorption of the target product ethanol and inhibiting side reactions; and the high specific surface area of 50-100m 2 / g provides a wide platform for highly dispersed active sites, so that they are fully exposed.

[0039] The second aspect of the application provides a preparation method of a composite metal oxide catalyst, comprising the following steps:

[0040] 1) adjusting the pH value of the mixed solution to be in the range of 10-12 by using a pH regulator, the mixed solution comprising A source, D source and E source;

[0041] 2) drying the precipitate to obtain a catalyst precursor;

[0042] 3) calcining the catalyst precursor to obtain a composite metal oxide catalyst.

[0043] The application adjusts the pH value of the mixed solution to be in the range of 10-12 by using a pH regulator, the mixed solution comprising A source, D source and E source, which can ensure the synchronous precipitation of metal ions and avoid the uneven distribution caused by the difference in the precipitation sequence of metal ions in the traditional coprecipitation method. Then the precipitate is dried to obtain a catalyst precursor, and finally the catalyst precursor is calcined to obtain a composite metal oxide catalyst.

[0044] In a specific embodiment, the mixed solution is first added to the pH regulator, and the pH regulator is continuously added while stirring until the pH value of the system is in the range of 10-12. By dynamically adding the pH regulator to maintain the pH stability, the standard deviation of the particle size distribution of the final precipitate can be effectively controlled.

[0045] It should be noted that the pH regulator comprises at least one of aqueous ammonia solution, aqueous sodium hydroxide solution and aqueous potassium hydroxide solution, and the mass concentration of the pH regulator is 10%-20%. The selection of aqueous ammonia solution is based on its weak alkaline buffering capacity, and the mass concentration of 10%-20% can effectively neutralize the acidic substances generated by the hydrolysis of metal salts, and can also avoid excessive aggregation of metal hydroxides caused by excessive alkali.

[0046] Based on the further research of the inventor, it is found that before drying, the precipitate is also subjected to suction filtration and washing until the pH value of the washing liquid is 7, and the washing liquid is at least one of methanol, ethanol and water. Suction filtration and washing until the pH value of the washing liquid is 7 can completely remove the soluble salt by-products and excess ions generated in the precipitation reaction and mixed in the solid precipitate; for example, ethanol as the washing liquid can very effectively maintain the nanopore structure of the catalyst precursor and high specific surface area, preventing particle agglomeration and pore collapse.

[0047] It should be added that after calcination, the catalyst is also subjected to surface pickling or alkali treatment, the acid for pickling being at least one of hydrochloric acid, nitric acid and citric acid, and the alkali for alkali treatment being at least one of aqueous sodium hydroxide solution, aqueous sodium carbonate solution and aqueous ammonia. After calcination, the catalyst is subjected to surface pickling or alkali treatment to regulate the exposed crystal face of the surface metal oxide, and by preferentially exposing the crystal face with high catalytic activity (such as the (111) face of CuO), the adsorption and activation capacity of the catalyst for reactants can be enhanced, and the deactivation phenomenon caused by surface defects can be reduced.

[0048] Further, the total mass concentration of the A source, the D source and the E source in the mixed solution is 10% to 15%, and the solvent in the mixed solution is at least one of methanol, ethanol and water. Exemplarily, when the total mass concentration of the A source, the D source and the E source is 15%, the A source, the D source and the E source have better solubility in the ethanol-water mixed solvent.

[0049] The application does not limit the A source, the D source and the E source. In an embodiment, the A source includes at least one of a chloride salt, a nitrate salt and a sulfate salt of element A, the D source includes at least one of a chloride salt, a nitrate salt and a sulfate salt of element D, and the E source includes at least one of a chloride salt, a nitrate salt and a sulfate salt of element E. Most of the nitrate salts and the chloride salts are easily soluble in water, and can form a uniform and clear mixed solution, thereby ensuring that the three metal ions of A, D and E are mixed at the atomic level, which is the basis for forming uniform and highly dispersed active sites. Moreover, the anions of the three types of salts are volatile or decomposable, and can be completely removed in the calcination process, thereby avoiding the residual anions from poisoning the catalyst.

[0050] In an embodiment, the drying is microwave drying, the temperature is 80 to 150°C, and the time is 12 to 24 hours. Compared with the traditional oven drying, the process can effectively shorten the drying period and reduce the particle agglomeration caused by thermal stress.

[0051] Further, the calcination temperature is 400 to 700°C, and the time is 3 to 5 hours. Exemplarily, the high temperature of 700°C can make the metal oxide grains grow to a stable size, and enhance the thermal stability of the carrier through the phase transition of ZrO2 (from monoclinic phase to tetragonal phase).

[0052] The third aspect of the application provides a preparation method of ethanol, which comprises the step of preparing ethanol by catalytic hydrogenation of dimethyl oxalate as a raw material. The catalyst in the catalytic hydrogenation comprises the composite metal oxide catalyst according to any one of claims 1 to 3, or the composite metal oxide catalyst obtained by the preparation method according to any one of claims 4 to 8.

[0053] In an embodiment, the molar ratio of dimethyl oxalate to hydrogen is 1:100 to 1:300, the reaction temperature is 200 to 250°C, the reaction pressure is 2.5 to 3.5 MPa, and the liquid hourly space velocity is 0.5 to 5 h -1 . Exemplarily, when the molar ratio of dimethyl oxalate to hydrogen is 1:150, the reaction temperature is 230°C, the reaction pressure is 3.0 MPa, and the liquid hourly space velocity is 0.6 h -1 , the Cu-Zn bimetallic active site is at an excellent activation temperature, and dimethyl oxalate can be completely gasified in the gasification chamber, thereby avoiding the limitation of liquid phase mass transfer.

[0054] The application will be further described below through specific examples.

[0055] Example 1

[0056] The present embodiment provides a preparation method of a CuO-ZrO2-Fe2O3 catalyst, comprising the following steps:

[0057] 1) 9.06 g of copper nitrate, 17.42 g of zirconium nitrate and 5.05 g of iron nitrate were dissolved in 100 mL of a mixed solvent of deionized water and ethanol to obtain a mixed metal salt solution;

[0058] 2) 180 g of an ammonia water solution with a mass concentration of 15% was prepared and divided into two portions, the mixed metal salt solution was slowly added to one portion of the ammonia water solution, and another portion of the ammonia water was added, the mixed metal salt solution was continuously stirred during the process, and the pH value of the precipitation process was controlled to be 12;

[0059] 3) the precipitate was washed by suction filtration with deionized water for 5 times until the pH value of the suction filtration liquid was 7;

[0060] 4) the precipitate after suction filtration was dried by microwave at 120°C for 12 h to obtain a catalyst precursor;

[0061] 5) after the catalyst precursor was calcined at 700°C for 4 h, the surface thereof was pickled with 0.5 mol / L of hydrochloric acid, a catalyst with a particle size of 0.1-0.15 mm was obtained, then tabletting was performed, and screening was performed to obtain particles with a particle size of 20-40 mesh, that is, a finished product Cu3Zr 3.25 Fe2O 12.5 .

[0062] Example 2

[0063] The preparation method of the present embodiment is basically the same as that of Example 1, the difference lies in that the E source is zinc nitrate. That is, in step 1), 9.06 g of copper nitrate, 17.42 g of zirconium nitrate and 7.31 g of zinc nitrate are dissolved in 100 mL of a mixed solvent of deionized water and ethanol; in step 5), a finished product Cu3Z r3.25 Zn 1.97 O 11.47 .

[0064] Example 3

[0065] The preparation method of the present embodiment is basically the same as that of Example 1, the difference lies in that the E source is magnesium nitrate. That is, in step 1), 9.06 g of copper nitrate, 17.42 g of zirconium nitrate and 12.724 g of magnesium nitrate are dissolved in 100 mL of a mixed solvent of deionized water and ethanol; in step 5), a finished product Cu3Zr 3.25 Mg 3.97 O13.47 .

[0066] Example 4

[0067] The preparation method of this example is basically the same as that of Example 1, except that the source of D is aluminum nitrate and the source of E is zinc nitrate. That is, in step 1), 9.06 g of copper nitrate, 18.389 g of aluminum nitrate, and 7.31 g of zinc nitrate are weighed and dissolved in 100 mL of a mixed solvent of deionized water and ethanol; in step 5), the finished product of the catalyst Cu3Al 7.84 Zn 1.97 O 16.73 .

[0068] Example 5

[0069] The preparation method of this example is basically the same as that of Example 1, except that the source of D is magnesium nitrate and the source of E is zinc nitrate. That is, in step 1), 9.06 g of copper nitrate, 31.809 g of magnesium nitrate, and 7.31 g of zinc nitrate are weighed and dissolved in 100 mL of a mixed solvent of deionized water and ethanol; in step 5), the finished product of the catalyst Cu3Mg 9.92 Zn 1.97 O 14.89 .

[0070] Example 6

[0071] The preparation method of this example is basically the same as that of Example 1, except that the source of D is zirconium nitrate and the source of E is aluminum nitrate. That is, in step 1), 9.06 g of copper nitrate, 17.42 g of zirconium nitrate, and 7.355 g of aluminum nitrate are weighed and dissolved in 100 mL of a mixed solvent of deionized water and ethanol; in step 5), the finished product of the catalyst Cu3Zr 3.25 Al 3.14 O 14.21 .

[0072] Example 7

[0073] The preparation method of this example is basically the same as that of Example 1, except that the source of A is iron nitrate, the source of D is zirconium nitrate, and the source of E is aluminum nitrate. That is, in step 1), 7.575 g of iron nitrate, 17.42 g of zirconium nitrate, and 7.355 g of aluminum nitrate are weighed and dissolved in 100 mL of a mixed solvent of deionized water and ethanol; in step 5), the finished product of the catalyst Fe3Zr 3.25 Al 3.14 O 15.71 .

[0074] Example 8

[0075] The preparation method of this example is basically the same as that of Example 1, except that the A source is nickel nitrate, the D source is zirconium nitrate, and the E source is aluminum nitrate. That is, in step 1), 11.679 g of nickel nitrate, 17.42 g of zirconium nitrate, and 7.355 g of aluminum nitrate are weighed and dissolved in 100 mL of a mixed solvent of deionized water and ethanol; and in step 5), the finished product of the catalyst is Ni3Zr 3.03 Al 2.93 O 13.46 。

[0076] Comparative Example 1

[0077] The preparation method of this comparative example is basically the same as that of Example 1, except that there is no A source. That is, in step 1), 23.26 g of zirconium nitrate and 6.74 g of iron nitrate are weighed and dissolved in 100 mL of a mixed solvent of deionized water and ethanol; and in step 5), the finished product of the catalyst is Zr3Fe 1.85 O 8.78 。

[0078] Test Example 1

[0079] The catalysts of the examples and comparative examples are tested. A fixed bed reactor is used, the catalyst is pressed, crushed, and sieved to obtain particles with a particle size of 20-40 mesh, and the loading amount is 4.8 g. The reactor is reduced at 230°C for 3 h at a hydrogen flow rate of 30 mL / min and a temperature increase rate of 2.5°C / min, after which the hydrogen flow rate is adjusted to 70 mL / min, the reaction raw material, 15%wt dimethyl oxalate methanol solution, is fed into the reactor at a feeding rate of 0.4 mL / min through a high-pressure feeding pump after being vaporized in a vaporization chamber at 160°C, the reaction temperature is 230°C, the pressure is 3.0 MPa, the molar ratio of dimethyl oxalate to hydrogen is 1:150, and the liquid hourly space velocity is 0.6 h -1 After the reaction, the liquid product is collected, analyzed by an Agilent 7890A gas chromatograph, and calculated using the following formula, and the results are shown in Table 1.

[0080] Conversion rate of dimethyl oxalate:

[0081] 1-(liquid product mass x dimethyl oxalate concentration in the product) / (reaction feed amount x dimethyl oxalate concentration in the raw material) x 100%

[0082] Selectivity of ethanol:

[0083] (liquid product mass x ethanol concentration in the product x 118 ÷ 46) / (reaction feed amount x dimethyl oxalate concentration in the raw material - liquid product mass x dimethyl oxalate concentration in the product) x 100%

[0084] Selectivity of ethylene glycol:

[0085] (liquid product mass x glycol concentration in product x 118 ÷ 62) / (reaction feed amount x dimethyl oxalate concentration in raw material - liquid product mass x dimethyl oxalate concentration in product) x 100%

[0086] Methyl glycolate selectivity:

[0087] (liquid product mass x methyl glycolate concentration in product x 118 ÷ 90) / (reaction feed amount x dimethyl oxalate concentration in raw material - liquid product mass x dimethyl oxalate concentration in product) x 100%

[0088] Table 1

[0089]

[0090] Test Example 2

[0091] As can be seen from Test Example 1, the Cu3Zr 3.25 Zn 1.97 O 11.47 catalyst of Example 2 exhibited high dimethyl oxalate conversion and selectivity to ethanol. Therefore, the Cu3Zr 3.25 Zn 1.97 O 11.47 catalyst of Example 2 was further tested, including:

[0092] 1) Catalyst life evaluation: The catalyst life was evaluated by a fixed bed evaluation device, and the evaluation method was as described in Test Example 1 above, and the results are shown in Table 2. After 800 h of reaction, the catalyst still maintained high dimethyl oxalate conversion and selectivity to ethanol, indicating that the catalyst had high activity and stability. Figure 1

[0093] 2) Catalyst pore structure: The catalyst pore structure was characterized and calculated by a low-temperature nitrogen adsorption-desorption experiment using the BJH method, and the results are shown in Table 3. As can be seen from the figure, the catalyst pore size distribution was concentrated and uniform, with most of the pores concentrated at about 3.8 nm. Figure 2

[0094] 3) Catalyst specific surface area: The catalyst specific surface area was further characterized by nitrogen adsorption-desorption, and the calculation method was the BET method, and the results are shown in Table 4. The overall height of the curve in the Y-axis direction reflects that the catalyst has a large specific surface area and pore volume. Figure 3

[0095] 4) Catalyst micro-morphology and element distribution: To further analyze the micro-morphology and element distribution of the catalyst, scanning electron microscopy and energy spectrum tests were performed, and the results are shown in Table 5. Figure 4 ​​​The Cu, Zn and Zr metal elements in the catalyst are uniformly distributed, that is, by controlling the pH value of the solution in the coprecipitation process, uniform precipitation of each metal component can be achieved, thereby prolonging the service life of the catalyst.

[0096] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A composite metal oxide catalyst characterized by, comprising: Chemical composition A x D y E z O n , wherein A includes at least one of Cu, Fe, and Ni, D includes at least one of Si, Al, Mg, and Zr, E includes at least one of Al, Fe, Zn, and Mg, A, D, and E are mutually different elements, x, y, z, and n represent atomic ratios of the respective elements, x is 1 to 5, y > 0, z > 0, and n > 0.

2. The catalyst according to claim 1, characterized in that, x = 3, y is 3-15, and z is 1-5.

3. Catalyst according to claim 1 or 2, characterized in that x = 3, y is 3.2-10, and z is 1.5-4; and / or, The particle size of the catalyst is 0.10-0.15 mm, the pore size is 2-5 nm, and the specific surface area is 50-100 m 2 / g.

4. A process for the preparation of a catalyst as claimed in any one of claims 1 to 3, characterized in that comprising the steps of: 1) adjusting the pH value of a mixed solution to be in the range of 10-12 using a pH adjuster to form a precipitate; the mixed solution comprising an A source, a D source, and an E source; 2) drying the precipitate to obtain a catalyst precursor; 3) calcining the catalyst precursor to obtain a composite metal oxide catalyst.

5. The preparation method according to claim 4, characterized in that, The step 1) comprises: first adding the mixed solution into the pH adjuster, and continuously adding the pH adjuster while stirring until the pH value of the system is in the range of 10-12; and / or, The pH adjuster comprises at least one of an aqueous ammonia solution, an aqueous sodium hydroxide solution, and an aqueous potassium hydroxide solution, and the mass concentration of the pH adjuster is 10%-20%.

6. The production method according to claim 4 or 5, characterized by, Before the step 2) drying, the precipitate is further subjected to suction filtration and washing until the pH value of the washing liquid is 7, and the washing liquid is at least one of methanol, ethanol, and water; and / or, After the step 3) calcining, the catalyst is further subjected to surface pickling or alkali treatment, the acid for the pickling is at least one of hydrochloric acid, nitric acid, and citric acid, and the alkali for the alkali treatment is at least one of an aqueous sodium hydroxide solution, an aqueous sodium carbonate solution, and aqueous ammonia.

7. The method of any one of claims 4-6, wherein the method further comprises, In the mixed solution, the total mass concentration of the A source, the D source, and the E source is 10%-15%, and the solvent in the mixed solution is at least one of methanol, ethanol, and water; and / or, The A source comprises at least one of a chloride salt, a nitrate salt, and a sulfate salt of element A, the D source comprises at least one of a chloride salt, a nitrate salt, and a sulfate salt of element D, and the E source comprises at least one of a chloride salt, a nitrate salt, and a sulfate salt of element E.

8. The method of any one of claims 4-7, wherein, The drying is microwave drying, the temperature is 80-150°C, and the time is 12-24h; and / or, The calcination temperature is 400-700°C, and the time is 3-5h.

9. A method of producing ethanol, characterized by, comprising the step of preparing ethanol by catalytic hydrogenation of dimethyl oxalate as a raw material, wherein the catalyst in the catalytic hydrogenation comprises the composite metal oxide catalyst according to any one of claims 1-3, or the composite metal oxide catalyst obtained by the preparation method according to any one of claims 4-8.

10. The method of claim 9, wherein, The molar ratio of the dimethyl oxalate to hydrogen is 1:100-1:300, the reaction temperature is 200-250℃, the reaction pressure is 2.5-3.5MPa, and the liquid hourly space velocity is 0.5-5h -1 .

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