A 3D dendritic porous Ni 3 P / SiO 2 Catalyst and its preparation method and application

Abstract

The present invention discloses a 3D dendritic porous Ni3P / SiO2 catalyst and its preparation method and application. The catalyst comprises an active component of nickel phosphide alloy and a support of dendritic porous SiO2, wherein the content of metallic Ni is 22% - 32% of the total mass of the catalyst, the content of phosphorus element is 3.8% - 5.6% of the total mass of the catalyst, and the content of SiO2 is 74.2% - 62.4% of the total mass of the catalyst. This catalyst uses 3D-dendritic SiO2 as the support, and its three-dimensional open framework structure has a high pore permeability. The metal is loaded on the surface of the support by the impregnation method and enters its petal-shaped pores at the same time, which is beneficial to improving the dispersion degree of Ni3P nanoparticles. Compared with Cu-based and Ag-based catalysts, it shows remarkable stability at high temperatures, maintains a high selectivity for MG within a large stable range, and can realize the conversion of dual products MG and MA by regulating the reaction temperature respectively.

Description

Technical Field

[0001] The present invention relates to the technical field of dimethyl oxalate hydrogenation catalyst preparation, and in particular to a 3D dendritic porous Ni 3 P / SiO 2 Catalyst and its preparation method and application. Background Art

[0002] Methyl glycolate (MG) is an important raw material for the production of polyglycolic acid (PGA). At present, the main methods for synthesizing methyl glycolate are: addition and hydrolysis of formaldehyde and hydrocyanic acid; hydrolysis of chloroacetic acid; formaldehyde hydrogen carboxylation and esterification; coupling of methyl formate and formaldehyde or polyoxymethylene; one-step oxidation esterification of glyoxal or glyoxal acetal and methanol; hydrogenation reduction of dimethyl oxalate, etc. The development of technology for preparing methyl glycolate by hydrogenation of dimethyl oxalate (DMO) is not only conducive to reducing the production cost of PGA, but also has the advantage of green and environmentally friendly process routes.

[0003] The catalyst for the hydrogenation of dimethyl oxalate to methyl glycolate mainly uses copper and silver as active components, but the high price, low efficiency and easy sintering at high temperature of silver-based catalysts limit their further application in the industrial field. At the same time, the selective hydrogenation of DMO to MG on copper-based catalysts faces the challenge of strong copper hydrogenation ability, and it is easy to further hydrogenate to ethylene glycol (EG). Therefore, the reaction temperature range is narrow (10-20°C), and the reaction temperature requirement for DMO hydrogenation to MG is high. At the same time, DMO hydrogenation itself is an exothermic reaction. The heat generated during the production process can easily lead to an increase in the local temperature of the fixed bed, thereby promoting the formation of by-product EG and reducing the selectivity of MG. Such characteristics make it difficult to obtain a single high-purity product, causing further separation difficulties and increasing production costs. In addition, the local overheating caused by the exothermic hydrogenation of DMO and the poor thermal conductivity of the metal oxide carrier lead to severe sintering of nano Cu particles, limiting its industrial application.

[0004] There are few studies on the synthesis of methyl acetate (MA) by hydrogenation of dimethyl oxalate. 2 C or Fe 2 C is further reacted to produce ethanol (EtOH) by hydrogenating DMO to generate MA, but the selectivity for the single product MA is low, always less than 80%, and DMO is difficult to completely convert, resulting in difficulty in separating the later products. Therefore, it is difficult to produce MA from DMO hydrogenation. In addition, metal carbides are prone to coking and deactivation at high temperatures, making it difficult to meet the industrial demand for long-term stable reactions at high temperatures. Summary of the invention

[0005] The first object of the present invention is to provide a 3D dendritic porous Ni 3 P / SiO 2 Catalyst with high catalytic activity and good stability.

[0006] The second object of the present invention is to provide the above-mentioned 3D dendritic porous Ni 3 P / SiO 2 The preparation method of the catalyst has simple steps and can be applied industrially.

[0007] The third object of the present invention is to provide the above-mentioned 3D dendritic porous Ni 3 P / SiO 2 The catalyst is used in the catalytic hydrogenation of dimethyl oxalate to prepare methyl glycolate and methyl acetate.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0009] In the first aspect, the present invention provides a 3D dendritic porous Ni 3 P / SiO 2 Catalyst, comprising an active component and a carrier, wherein the active component is a nickel-phosphorus alloy, and the carrier is a 3D dendritic porous SiO 2 (named DPS), in which the content of metal Ni is 22% to 32% of the total mass of the catalyst, the content of phosphorus is 3.8% to 5.6% of the total mass of the catalyst, and the content of SiO 2 The content is 74.2% to 62.4% of the total mass of the catalyst.

[0010] In a second aspect, the present invention provides the above-mentioned 3D dendritic porous Ni 3 P / SiO 2 The method for preparing the catalyst comprises the following steps:

[0011] (1) Tetraethyl orthosilicate, cyclohexane and n-pentanol are fully mixed and stirred at 20-30° C. for 20-25 min; then water, urea and hexadecyltrimethylammonium bromide are added and stirred for 10 min to obtain a suspension, wherein the molar ratio of each component is: tetraethyl orthosilicate: cyclohexane: n-pentanol: water: urea: hexadecyltrimethylammonium bromide = 1:20.8:1.02:123.15:0.738:0.46;

[0012] (2) transferring the suspension obtained in step (1) to a hydrothermal reactor and reacting at 130° C. for 4.5 h;

[0013] (3) The white precipitate obtained in step (2) is centrifuged and washed, then dried and calcined to obtain a dendritic porous SiO 2 Carrier;

[0014] (4) Add nickel nitrate hexahydrate and diammonium hydrogen phosphate into water, wherein the molar ratio of nickel nitrate hexahydrate to diammonium hydrogen phosphate is 2.9-3, then ultrasonically vibrate for 10 minutes and dropwise add HNO 3 To clarify;

[0015] (5) The dendritic porous SiO prepared in step (3) 2 The carrier is added to the clear solution prepared in step (4) and ultrasonically shaken for 30 minutes, and then allowed to stand for 24 hours for impregnation;

[0016] (6) drying after impregnation and calcining at 600°C for 4 h under air conditions;

[0017] (7) The calcined catalyst is pressed into tablets, and the catalyst with a mesh size of 40 to 60 is cut and screened; the catalyst is reduced in a hydrogen atmosphere to finally obtain the catalyst xNi 3 P / DPS (x represents Ni loading amount).

[0018] Preferably, in step (3), the calcination temperature is 500-600° C. and the calcination time is 5-7 h.

[0019] Preferably, in step (3) and step (6), the drying temperature is 100° C. and the drying time is 12 h.

[0020] Preferably, in step (7), the reduction temperature is 650° C. and the reduction time is 2 h.

[0021] In a third aspect, the present invention provides the above-mentioned 3D dendritic porous Ni 3 P / SiO 2 The catalyst is used in the catalytic hydrogenation of dimethyl oxalate to prepare methyl glycolate and methyl acetate.

[0022] Hydrogen is used as the raw material gas, and a methanol solution containing 13% dimethyl oxalate by mass is used as the raw material liquid. The molar ratio of hydrogen to dimethyl oxalate in the reaction is 100, the reaction temperature range is 200-360°C, the reaction pressure is 2MPa, and the reaction space velocity is 0.8h -1 .

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The catalyst is 3D-branched SiO 2 As a carrier, its three-dimensional open framework structure has a high pore permeability, which is conducive to the transport of substances along the central-radial channels and their further reaction with the active sites on the inner surface. In addition, the metal is loaded on the surface of the carrier by impregnation and enters its petal-shaped pores at the same time, which is conducive to improving the Ni 3 Dispersion of P nanoparticles.

[0025] 2. When the catalyst is used in the reaction of hydrogenating dimethyl oxalate to synthesize methyl glycolate, the MG selectivity can be maintained above 90% in the temperature range of 200℃-260℃. When it is used in the reaction of hydrogenating dimethyl oxalate to synthesize methyl acetate, DMO is completely converted at 340℃, and the MA selectivity reaches above 90%. After running at a high temperature of 340℃ for 300 hours, the grain size does not increase significantly. Compared with Cu-based and Ag-based catalysts, it shows significant stability at high temperatures and maintains high selectivity of MG in a large stable range. And the conversion of the dual products MG and MA can be achieved separately by adjusting the reaction temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is the X-ray diffraction pattern of the supported nickel-based catalyst prepared in Examples 1 to 5;

[0027] Figure 2 is a nitrogen physical adsorption diagram of the supported nickel-based catalysts prepared in Examples 1 to 5;

[0028] Figure 3 is the H of the supported nickel-based catalyst prepared in Examples 1 to 5 2 -TPR spectra;

[0029] Figure 4 SEM images of DPS carrier and supported nickel-based catalysts prepared in Examples 1, 3, and 5: (a) DPS; (b) 22% Ni 3 P / DPS; (c) 27% Ni 3 P / DPS; (d) 32% Ni 3 P / DPS;

[0030] Figure 5 is 27% Ni 3 P / DPS catalyst stability test results diagram;

[0031] Figure 6 is 27% Ni 3 TEM comparison of P / DPS catalyst before and after reaction at 340℃ for 300h: (a) before reaction; (b) after reaction. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] The raw materials and reagents described in the following examples are all commercially available products, and their purity is analytical grade or above.

[0034] Example 1

[0035] 9 mL of tetraethyl orthosilicate was added to 90 mL of cyclohexane, and 4.5 mL of n-pentanol was used as a cosolvent. The mixture was stirred at 20 ° C for 30 min, and 6 g of hexadecyltrimethylammonium bromide, 1.8 g of urea and 90 mL of deionized water were added while stirring. The mixture was then transferred to a 400 mL hydrothermal kettle and reacted at 130 ° C for 4.5 h. The collected precipitate was added with ethanol for centrifugal washing, dried at 100 ° C for 12 h, and calcined at 550 ° C in a muffle furnace for 6 h to obtain the carrier - dendritic porous silica-DPS.

[0036] Add 1.485 g Ni(NO 3 ) 2 6H 2 O and 0.232 g (NH 4 ) 2 HPO 4 , adding HNO 3 The solution was clarified. Then 1g of DPS carrier was added to the above solution, impregnated at room temperature for 24 hours, dried at 100℃ for 12 hours, and calcined in air at 600℃ for 4 hours. The calcined catalyst was pressed into tablets and cut and screened into catalysts with 40-60 mesh. -1 The temperature was raised to 650 ° C in a hydrogen flow and maintained for 2 h for reduction, and finally the catalyst 22% Ni 3 P / DPS.

[0037] Example 2

[0038] 9 mL of tetraethyl orthosilicate was added to 90 mL of cyclohexane, and 4.5 mL of n-pentanol was used as a cosolvent. The mixture was stirred at 20 ° C for 30 min, and 6 g of hexadecyltrimethylammonium bromide, 1.8 g of urea and 90 mL of deionized water were added while stirring. The mixture was then transferred to a 400 mL hydrothermal kettle and reacted at 130 ° C for 4.5 h. The collected precipitate was added with ethanol for centrifugal washing, dried at 100 ° C for 12 h, and calcined at 550 ° C in a muffle furnace for 6 h to obtain the carrier - dendritic porous silica-DPS.

[0039] Add 1.753 g Ni(NO 3 ) 2 6H 2 O and 0.265 g (NH 4 ) 2 HPO 4 , adding HNO 3The solution was clarified. Then 1g of DPS carrier was added to the above solution, impregnated at room temperature for 24 hours, dried at 100℃ for 12 hours, and calcined in air at 600℃ for 4 hours. The calcined catalyst was pressed into tablets and cut and screened into catalysts with 40-60 mesh. -1 The temperature was raised to 650 ° C in a hydrogen flow and maintained for 2 h for reduction, and finally the catalyst 25% Ni 3 P / DPS.

[0040] Example 3

[0041] 9 mL of tetraethyl orthosilicate was added to 90 mL of cyclohexane, and 4.5 mL of n-pentanol was used as a cosolvent. The mixture was stirred at 20 ° C for 30 min, and 6 g of hexadecyltrimethylammonium bromide, 1.8 g of urea and 90 mL of deionized water were added while stirring. The mixture was then transferred to a 400 mL hydrothermal kettle and reacted at 130 ° C for 4.5 h. The collected precipitate was added with ethanol for centrifugal washing, dried at 100 ° C for 12 h, and calcined at 550 ° C in a muffle furnace for 6 h to obtain the carrier - dendritic porous silica-DPS.

[0042] Add 2.001 g Ni(NO 3 ) 2 6H 2 O and 0.312 g (NH 4 ) 2 HPO 4 , adding HNO 3 The solution was clarified. Then 1g of DPS carrier was added to the above solution, impregnated at room temperature for 24 hours, dried at 100℃ for 12 hours, and calcined in air at 600℃ for 4 hours. The calcined catalyst was pressed into tablets and cut and screened into catalysts with 40-60 mesh. -1 The temperature was raised to 650 ° C in a hydrogen flow and maintained for 2 h for reduction, and finally the catalyst 27% Ni 3 P / DPS.

[0043] Example 4

[0044] 9 mL of tetraethyl orthosilicate was added to 90 mL of cyclohexane, and 4.5 mL of n-pentanol was used as a cosolvent. The mixture was stirred at 20 ° C for 30 min, and 6 g of hexadecyltrimethylammonium bromide, 1.8 g of urea and 90 mL of deionized water were added while stirring. The mixture was then transferred to a 400 mL hydrothermal kettle and reacted at 130 ° C for 4.5 h. The collected precipitate was added with ethanol for centrifugal washing, dried at 100 ° C for 12 h, and calcined at 550 ° C in a muffle furnace for 6 h to obtain the carrier - dendritic porous silica-DPS.

[0045] Add 2.297 g Ni(NO 3 ) 2 6H 2 O and 0.348 g (NH 4 ) 2 HPO 4 , adding HNO 3 The solution was clarified. Then 1g of DPS carrier was added to the above solution, impregnated at room temperature for 24 hours, dried at 100℃ for 12 hours, and calcined in air at 600℃ for 4 hours. The calcined catalyst was pressed into tablets and cut and screened into catalysts with 40-60 mesh. -1 The temperature was raised to 650 ° C in a hydrogen flow and maintained for 2 h for reduction, and finally the catalyst 30% Ni 3 P / DPS.

[0046] Example 5

[0047] 9 mL of tetraethyl orthosilicate was added to 90 mL of cyclohexane, and 4.5 mL of n-pentanol was used as a cosolvent. The mixture was stirred at 20 ° C for 30 min, and 6 g of hexadecyltrimethylammonium bromide, 1.8 g of urea and 90 mL of deionized water were added while stirring. The mixture was then transferred to a 400 mL hydrothermal kettle and reacted at 130 ° C for 4.5 h. The collected precipitate was added with ethanol for centrifugal washing, dried at 100 ° C for 12 h, and calcined at 550 ° C in a muffle furnace for 6 h to obtain the carrier - dendritic porous silica-DPS.

[0048] Add 2.602 g Ni(NO 3 ) 2 6H 2 O and 0.407 g (NH 4 ) 2 HPO 4 , adding HNO 3 The solution was clarified. Then 1g of DPS carrier was added to the above solution, impregnated at room temperature for 24 hours, dried at 100℃ for 12 hours, and calcined in air at 600℃ for 4 hours. The calcined catalyst was pressed into tablets and cut and screened into catalysts with 40-60 mesh. -1 The temperature was raised to 650 ° C in a hydrogen flow and maintained for 2 h for reduction, and finally a catalyst 32% Ni 3 P / DPS.

[0049] according to Figure 1 The XRD results show that Ni 3 There are various phases of nickel phosphide in the P / DPS series catalysts, but the overall3 P (JCPDS 34 - 0501; 2θ≈36.42°, 41.76°, 42.82°, 43.63°, 45.21°, 46.61°, 50.55°, 52.71° corresponding to (031), (231), (330), (112), (240), (141), (222), (132) planes respectively) is dominant, indicating that the target alloy Ni 3 P is well formed on the surface of DPS. For 22% Ni 3 P mainly enters into the pores of DPS, and there is less metal attached to the surface of the carrier, resulting in relatively weak diffraction peaks of the crystal in the detection results and only showing Ni 3 P diffraction peaks. When the loading amount of Ni increases, the diffraction peak intensity of Ni 3 P increases.

[0050] All samples show similar type-IV isotherms and typical H3-hysteresis loops in the range of 0.2 < P / P0 < 1.0 ( Figure 2 ), which is attributed to the presence of slit-shaped mesopores with different sizes in the material. And when the isotherms of all samples do not tend to be stable near P / P0 = 1, this indicates that there are macropores in both the carrier and the catalyst.

[0051] Figure 3 The Ni 3 P / DPS catalyst precursors with different loadings shown 2 -TPR curves. The low-temperature reduction peak appearing near 400 °C is mainly attributed to the reduction of NiO, and the reduction peak near 500 °C is mainly due to the reduction of nickel silicate compounds and small particle NiO. With the increase of the loading amount, the dispersion of the metal decreases, and the particle size of the nickel silicate species increases, resulting in an increase in the reduction difficulty of the nickel silicate species and an increase in the reduction temperature. For 25% Ni 3 P / DPS and 30% Ni 3 P / DPS catalysts, due to the relatively large actual molar ratio of Ni / P, part of Ni is not combined with P, forming Ni 3 P alloy, so the area of the low-temperature reduction peak is larger. A relatively high reduction peak appears near 600 °C, corresponding to the reduction of P in the Ni 3 P alloy. This is because the P-O bond is very stable. When the phosphorus species are loaded on the surface of the carrier, the hydrophilic and difficult-to-reduce phosphorus species make it easy to form H 2 O or -OH on the catalyst surface, resulting in the difficulty of reducing nickel species, thus leading to a relatively high and large-area reduction peak near 600 °C for the Ni 3 P / DPS catalyst precursor. And the shoulder peak appearing at 680 °C corresponds to P x O yAs the P loading gradually increases, the catalyst specific surface area decreases, the dispersion of phosphorus species decreases, the particles increase, and H 2 With P x O y The contact opportunity becomes smaller, and the migration of hydrogen becomes more difficult, resulting in the appearance of a shoulder peak.

[0052] Figure 4 (a) shows that the porous channels of the DPS carrier extend radially outward from the center, and the overall structure is a petal-shaped three-dimensional framework. 2 Compared with the particles, the open three-dimensional structure of DPS is conducive to the transport of substances along the central-radial channels and their further reaction with the active sites on the inner surface. 2 The surface of the sphere can enter its petal-shaped pores, which is beneficial to increase the Ni 3 Dispersion of P nanoparticles. Figure 4 (b)-(d) represent the xNi with increasing Ni loading. 3 P / DPS catalyst, loaded with active component Ni 3 After P, the three-dimensional petal-shaped framework structure of the DPS body was basically not damaged.

[0053] Example 6

[0054] The catalysts prepared in Examples 1-5 were all prepared using a fixed bed reactor to investigate the specific catalytic performance of the catalyst for preparing methyl glycolate by selective hydrogenation of dimethyl oxalate:

[0055] A stainless steel reaction tube was used as the reactor, with an outer diameter of 20 mm, an inner diameter of 8 mm, and a length of 300 mm. The catalyst loading amount was 0.4 g. After the reaction tail gas was condensed and separated, a Fuli GC9790PLUS gas chromatograph was used to quantitatively analyze the product.

[0056] The conversion rate and selectivity were calculated using the normalization method:

[0057] Conversion rate (%) = (1-A DMO f DMO / ∑A i f i )×100%;

[0058] Selectivity (%) = (A i f i / ∑A i f i )×100%;

[0059] Among them A i represents the FID chromatographic peak area; f irepresents the FID relative molar correction factor.

[0060] Reaction conditions: hydrogen is used as the raw gas, and a methanol solution containing 13% dimethyl oxalate by mass is used as the raw liquid. The molar ratio of hydrogen to dimethyl oxalate in the reaction is 100, the reaction temperature range is 200-360°C, the reaction pressure is 2MPa, and the reaction space velocity is 0.8h -1 .

[0061] The reaction results are shown in the following table:

[0062]

[0063]

[0064] At different loading levels of Ni 3 Under the action of P / DPS catalyst, the conversion rate of DMO increases with the increase of reaction temperature, and at 340℃, the conversion rate of DMO reaches 100%. In the range of 200~260℃, MG has a high selectivity, which is always kept above 90%. 3 Taking P / DPS catalyst as an example, at 240℃, the conversion rate of DMO reached 93%, and EG maintained low selectivity during the entire reaction process. When the temperature was raised to 320℃, a large amount of MG began to convert to MA. At 340℃, the selectivity of MA reached 90%. After that, increasing the temperature had no significant effect on the catalyst activity. 3 The activity of the P / DPS catalyst also showed high selectivity for MG at low temperatures, and catalytic properties for the conversion of the main product from MG to MA when the temperature was increased.

[0065] Example 7

[0066] Reaction conditions: hydrogen was used as the raw gas, and a methanol solution containing 13% dimethyl oxalate by mass was used as the raw liquid. The molar ratio of hydrogen to dimethyl oxalate in the reaction was 100, and 27% Ni 3 P / DPS catalyst, at a reaction temperature of 340°C, a reaction pressure of 2MPa, and a reaction space velocity of 0.8h -1 The stability test was carried out for 300 hours under the conditions of

[0067] according to Figure 5 As shown in the figure, under the reaction conditions of 340℃, the DMO conversion rate reaches 100%, and the MA selectivity is about 89%. At the same time, it can achieve stable operation for 300h at high temperature without deactivation. Figure 6 TEM characterization shows that after the reaction, Ni 3The particle size of P increased from 13.26nm to 13.54nm, which was not a dramatic increase and was within an acceptable range. Therefore, it was proved that the petal-shaped three-dimensional framework structure of DPS had a significant effect on Ni 3 P nanoparticles play an excellent dispersing role and avoid Ni 3 The migration and agglomeration growth of P on the surface of the carrier ensures that Ni 3 The P / DPS catalyst exhibits good stability in long-term high-temperature catalytic reactions.

[0068] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. Application of a 3D dendritic porous Ni3P / SiO2 catalyst in the catalytic preparation of methyl acetate by hydrogenation of dimethyl oxalate, characterized in that: The catalyst comprises an active component and a carrier, wherein the active component is a nickel-phosphorus alloy, and the carrier is a 3D dendritic porous SiO2, wherein the content of metal Ni is 22% to 32% of the total mass of the catalyst, the content of phosphorus is 3.8% to 5.6% of the total mass of the catalyst, and the content of SiO2 is 74.2% to 62.4% of the total mass of the catalyst; The catalyst is prepared by the following steps: (1) Tetraethyl orthosilicate, cyclohexane and n-pentanol are fully mixed and stirred at 20-30°C for 20-25 minutes; then water, urea and hexadecyltrimethylammonium bromide are added and stirred for 10 minutes to obtain a suspension, wherein the molar ratio of each component is: tetraethyl orthosilicate: cyclohexane: n-pentanol: water: urea: hexadecyltrimethylammonium bromide = 1: 20.8: 1.02: 123.15: 0.738: 0.46; (2) The suspension obtained in step (1) was transferred to a hydrothermal reactor and reacted at 130° C. for 4.5 h; (3) The white precipitate obtained in step (2) is centrifuged and washed, then dried and calcined to obtain a dendritic porous SiO2 carrier; (4) adding nickel nitrate hexahydrate and diammonium hydrogen phosphate into water, wherein the molar ratio of nickel nitrate hexahydrate to diammonium hydrogen phosphate is 2.9-3, then ultrasonically shaking for 10 min and adding HNO3 dropwise until clarified; (5) Add 1 g of the dendritic porous SiO2 carrier prepared in step (3) to the clear solution prepared in step (4) and ultrasonically vibrate for 30 min, then let it stand for 24 h for impregnation; (6) After impregnation, the mixture is dried and calcined at 600 °C for 4 h under air conditions; (7) Pressing the calcined catalyst into tablets, and cutting and screening the catalyst with a mesh size of 40 to 60; reducing the catalyst in a hydrogen atmosphere to finally obtain the catalyst xNi3P / DPS, where x represents the Ni loading amount; The specific steps are: using hydrogen as the raw gas, and a methanol solution containing 13% of dimethyl oxalate by mass as the raw liquid; the molar ratio of hydrogen to dimethyl oxalate in the reaction is 100, the reaction temperature range is 340-360°C, the reaction pressure is 2MPa, and the reaction space velocity is 0.8h -1 .

2. The use according to claim 1, characterized in that: In step (3), the calcination temperature is 500-600°C and the calcination time is 5-7h.

3. The use according to claim 1, characterized in that: In step (3) and step (6), the drying temperature is 100° C. and the drying time is 12 h.

4. The use according to claim 1, characterized in that: In step (7), the reduction temperature is 650° C. and the reduction time is 2 h.

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