A spinel-structured Cu 0.5 Co 0.5 Method for preparing o-nitrobenzaldehyde using Al2O4 catalyst

Abstract

The application discloses a spinel structure Cu 0.5 Co 0.5 Al2O4 catalyst and a method for catalytically preparing o-nitrobenzaldehyde, and belongs to the field of chemical synthesis. The method uses o-nitrobenzyl alcohol as a raw material, dissolves the raw material in an organic solvent, uses spinel structure Cu 0.5 Co 0.5 Al2O4 as a reaction system catalyst, adds TEMPO as a cocatalyst, and reacts in a fixed bed under the condition of oxygen being introduced. After the reaction is completed, the reaction system is cooled to normal temperature, is dissolved, and then a crude product is obtained. The conversion rate of the reaction is 100%, and the selectivity is 98.9%. The crude product is purified through recrystallization of n-hexane, and then o-nitrobenzaldehyde is obtained. The product has a gas phase purity of 99.95%. The spinel structure Cu 0.5 Co 0.5 Al2O4 spinel catalyst has high catalytic activity and high catalytic stability, and has recycling usability, and therefore provides an efficient, economical and green and environment-friendly synthesis method for o-nitrobenzaldehyde.

Description

Technical Field

[0001] This invention belongs to the field of chemical synthesis, specifically relating to a method for the efficient preparation of o-nitrobenzaldehyde. Background Technology

[0002] o-Nitrobenzaldehyde is an important intermediate in organic synthesis, widely used in pharmaceuticals, dyes, and pesticides. In pharmaceuticals, it is commonly used to synthesize drugs such as nifedipine, nisodipine, encaine, and ambroxol hydrochloride. Other downstream products derived from it, such as Solvent Yellow 114 and indigo, are used in the dye industry, demonstrating its broad applications in daily production and life. Currently, common oxidation processes for synthesizing o-nitrobenzaldehyde include nitric acid, copper amine catalytic systems, and Co(III)NaBr systems. However, these catalytic oxidation systems produce complex byproducts and associated products with low yields, which does not align with the current green, safe, and environmentally friendly development principles. Therefore, finding an efficient and suitable method for synthesizing o-nitrobenzaldehyde is imperative.

[0003] Tian Shu et al. synthesized o-nitrobenzaldehyde using a copper-amine reagent, diethyl hydrazine diacetate, and potassium carbonate system. This system operates under mild reaction conditions and achieves a yield of 70%. The reaction formula is as follows:

[0004]

[0005] This method has a lower product yield compared to the present method, and the catalyst is prone to losing its catalytic activity when recycled, which increases the economic cost and makes it too low in economic value to achieve industrialization.

[0006] The commonly used oxidation method is the one used by Zhu Yangfei et al., which involves oxidizing o-nitrobenzyl alcohol with 20% HNO3 at 80°C in a two-phase system of nitromethane and water to obtain the corresponding o-nitrobenzaldehyde, with a yield of 90%. The reaction formula is as follows:

[0007]

[0008] Although this method yields acceptable results, the vapor of CH3NO2 forms an explosive mixture upon contact with air, making the reaction too dangerous and requiring highly skilled equipment and operators, thus unsuitable for industrial production. Lian Yue et al. used palladium acetate and dimethylacetamide as catalysts to oxidize o-nitrobenzyl alcohol at 80°C with O2 as the oxidant, achieving a 65% yield of o-nitrobenzaldehyde. The reaction formula is as follows:

[0009]

[0010] While this method is simple to operate, the yield is not very high, and palladium salt catalysts are relatively expensive compared to the catalytic system used in this study, and recycling them is also difficult, making large-scale industrial production impractical. Manyar et al. used a supported polyoxometalate catalyst to oxidize o-nitrobenzyl alcohol to the desired aldehyde under mild conditions, achieving 100% selectivity, but the yield was only 26%. The reaction formula is as follows:

[0011]

[0012] Although this method has high selectivity, the yield is too low and it requires the preparation of supported polyoxometalate catalysts, which does not meet the principle of economic applicability and is not suitable for industrial production.

[0013] Liu Changchun et al. used an ionic liquid as the reaction medium and Ru(III)-modified hydroxyapatite (HAP) as a catalyst to catalyze the oxidation of o-nitrobenzyl alcohol with oxygen to obtain o-nitrobenzaldehyde, with a selectivity of 98.2% and a conversion rate of 93.4%. The reaction formula is as follows:

[0014]

[0015] This method has high selectivity and conversion rate, but the ionic liquid and Ru(III) modified hydroxyapatite (HAP) used in the reaction system have not yet been widely used in industrial production. Moreover, compared with this method, the selectivity and conversion rate of this method are both higher.

[0016] Hirano et al. significantly improved the catalytic efficiency of the cobalt acetate-catalyzed oxidation of o-nitrobenzyl alcohol by adding NaBr, achieving a 72% yield of o-nitrobenzaldehyde. The reaction formula is as follows:

[0017]

[0018] This method offers a moderate yield, but the NaBr used in the reaction system generates a large amount of saline wastewater, increasing the difficulty of post-treatment. Furthermore, the introduced cobalt acetate may not be effectively removed, making it unsuitable for large-scale industrial production. Sylvain Lemaitre et al. used cuprous chloride and TEMPO as catalysts to oxidize o-nitrobenzyl alcohol at 20°C with O2 as the oxidant, achieving a 73% yield of o-nitrobenzaldehyde. The reaction formula is as follows:

[0019]

[0020] While this method is simple to operate, the yield is not very high, and excessive oxidation to produce acid still occurs in this system, adding some trouble to the subsequent post-processing. This method has higher selectivity and conversion rate than this method, and the reaction does not have the problem of excessive oxidation, making subsequent post-processing simpler.

[0021] CN201410067833 mentions the oxidation of benzyl alcohol to aldehydes using manganese dioxide as a catalyst and 1,2-dichloroethane as a solvent, with a yield of 67%. The reaction formula is as follows:

[0022]

[0023] This method uses manganese dioxide oxidation. Although the catalyst is readily available, the excessive amount of manganese dioxide used and its difficult recovery result in significant waste. Furthermore, the yield is not very high, and post-processing separation is challenging, making it unsuitable for large-scale industrial production. The catalyst used in this invention is simple to prepare, has high catalytic activity, and the product is easily separated from the catalyst. Moreover, the continuous flow reaction is more suitable for large-scale industrial production. Summary of the Invention

[0024] This invention addresses the problems existing in commonly used oxidation reaction processes by providing an efficient, economical, green, and environmentally friendly method for preparing o-nitrobenzaldehyde.

[0025] This invention uses a highly efficient method for preparing o-nitrobenzaldehyde, the steps of which are as follows:

[0026] Using o-nitrobenzyl alcohol as a raw material, spinel-structured Cu 0.5 Co 0.5 Al2O4 was used as the catalyst in the reaction system, and peroxide was added as a co-catalyst. Oxygen was introduced into the organic solvent to carry out the reaction. After the reaction was completed, the mixture was cooled to room temperature and filtered to remove solvent, and the crude product was obtained. The crude product was then purified by recrystallization from n-hexane to obtain the product o-nitrobenzaldehyde.

[0027] Furthermore, Cu 0.5 Co 0.5 The preparation method of Al2O4 spinel catalyst is as follows:

[0028] Soluble copper salt, soluble cobalt salt, and soluble aluminum salt were weighed in a molar ratio of 1:1:4 to prepare a mixed aqueous solution of metal salts. NaOH solution was used as a precipitant to obtain a coprecipitate. The coprecipitate was aged in a water bath at 50–80°C for 8–24 hours, then filtered and washed until the filtrate was neutral. The filter cake was dried in an oven at 55°C for 20 hours. Finally, the spinel precursor was calcined in a muffle furnace at 600–1000°C for 5–10 hours to obtain Cu. 0.5 Co 0.5 Al2O4.

[0029] The further synthesis method is as follows:

[0030] Cu 0.5 Co 0.5Al₂O₄ spinel was used as a catalyst, granulated, and then loaded into a fixed-bed reactor. Oxygen was introduced and the pressure was kept constant at 0.5–3.0 MPa. The preheating temperature was 80°C, the reaction temperature in the reaction tube was 90–130°C, and the mass hourly space velocity (WHSV) was 0.25–1.0 h⁻¹. -1 o-Nitrobenzyl alcohol, peroxide auxiliaries and organic solvents were mixed in molar ratio to obtain a mixture. The mixture was introduced into a reactor for reaction. After the reaction, the reaction solution was collected and desolventized to obtain a crude product. The crude product was recrystallized to obtain o-nitrobenzaldehyde.

[0031] Furthermore, the peroxide auxiliary is TEMPO; wherein the molar ratio of o-nitrobenzyl alcohol, TEMPO, and organic solvent is 1:0.01 to 0.1:6. Preferably, the molar ratio of o-nitrobenzyl alcohol, peroxide auxiliary, and organic solvent is 1:0.05:6.

[0032] The organic solvent is one of dichloromethane, chloroform, water, and 1,2-dichloroethane. Dichloromethane is further preferred.

[0033] The reaction temperature is 90–120°C; more preferably, the reaction temperature is 120°C.

[0034] The mass hourly space velocity (MHSV) is 0.25–1.0 h⁻¹. -1 .

[0035] Preferably, the amount of oxygen introduced in the step is to maintain a constant pressure of 2.0 MPa.

[0036] Compared to existing technologies, the method for preparing o-nitrobenzaldehyde provided by this invention uses o-nitrobenzyl alcohol as a raw material, Cu 0.5 Co 0.5 Al₂O₄ was used as the catalyst in the reaction system, and an appropriate amount of TEMPO was added as a co-catalyst. Oxygen was introduced into a fixed bed for oxidation. The reaction had extremely high conversion and selectivity, and only water was produced besides the product o-nitrobenzaldehyde. 0.5 Co 0.5 The Al2O4 spinel catalyst showed no significant decrease in activity after 100 hours of continuous use, demonstrating good stability. An appropriate amount of peroxide promoter can be recovered and reused after recrystallization. This method is recyclable, green, safe, and environmentally friendly, aligning with current green chemistry development principles, and can significantly reduce costs. Attached Figure Description

[0037] Figure 1 Cu 0.5 Co 0.5 XRD characterization of Al2O4 catalyst.

[0038] Figure 2 Cu 0.5 Co0.5 Full spectrum of Al2O4 catalyst.

[0039] Figure 3 Cu 0.5 Co 0.5 Al2O4 catalyst Cu2p diagram.

[0040] Figure 4 Cu 0.5 Co 0.5 Co2p diagram of Al2O4 catalyst.

[0041] Figure 5 Cu 0.5 Co 0.5 Al2p diagram of Al2O4 catalyst.

[0042] Figure 6 Cu 0.5 Co 0.5 Statistical graph of the stable reaction of Al2O4 catalyst after 100h.

[0043] Figure 7 Cu 0.5 Co 0.5 SEM characterization of Al2O4 catalyst.

[0044] Figure 8 This is the GC-MAS plot after the reaction is complete. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments.

[0046] Example 1

[0047] Cu was prepared by co-precipitation method 0.5 Co 0.5 Al₂O₄. Cu(NO₃)₂·3H₂O, Co(NO₃)₂·6H₂O, and Al(NO₃)₂·9H₂O were weighed in a molar ratio of 1:1:4 to prepare a nitrate mixed aqueous solution. A 17% NaOH aqueous solution was used as a precipitant to maintain the pH at 9–10 until the reaction was complete, yielding a coprecipitate. The coprecipitate was then aged in a water bath at 55°C for 12 hours, followed by filtration and washing until the filtrate was neutral. The filter cake was dried in an oven at 55°C for 20 hours. Finally, the spinel precursor was calcined in a muffle furnace at 900°C for 6 hours to obtain Cu. 0.5 Co 0.5 Al2O4. Powdered Cu 0.5 Co 0.5Al2O4 catalyst, pseudoboehmite, and dilute nitric acid were mixed in a mass ratio of 6:1:3 to prepare a soft material. The soft material was then mechanically extruded to obtain wet particles, which were then dried at 150°C for 3 hours to obtain the desired catalyst particles.

[0048] Figure 1 Cu 0.5 Co 0.5 XRD characterization of Al2O4 catalyst; Figure 1 The crystal plane indices corresponding to the XRD diffraction peaks point to (220), (311), (400), (422), (511), (440), (620), and (533), exhibiting a typical spinel structure. Figure 2 Cu 0.5 Co 0.5 Full spectrum of Al2O4 catalyst; Figure 2 It can be known that the catalyst is composed of Cu, Co, Al, and O. Figure 3 Cu 0.5 Co 0.5 Cu2p diagram of Al2O4 catalyst; from Figure 3 The binding energies for Cu 2p 1 / 2 and Cu 2p 3 / 2 are 954.5 eV and 934.7 eV, respectively, indicating that Cu in spinel is Cu 2+ . Figure 4 Cu 0.5 Co 0.5 Co2p diagram of Al2O4 catalyst; from Figure 4 The binding energies for Co 2p 1 / 2 and Co 2p 3 / 2 are 796.2 eV and 781.6 eV, respectively, indicating that Co in spinel is Co 2+ . Figure 5 Cu 0.5 Co 0.5 Al2p diagram of Al2O4 catalyst; from Figure 5 It can be seen that the low-side binding energy of Al2p is 74.1 eV and the high-side binding energy is 77.6 eV, which represent the Al2p atoms located in the spinel tetrahedron and spinel octahedron, respectively. 3+ .

[0049] 10g of Cu, which has been prepared into granular form, was packed into a fixed-bed reactor. 0.5 Co 0.5 Al2O4 catalyst, O2 introduced to maintain a constant pressure of 2.0 MPa, preheated to 80℃, reaction tube temperature 120℃, mass hourly space velocity 1.0 h⁻¹ -1The raw material ratio was: o-nitrobenzyl alcohol, TEMPO, and dichloromethane in a molar ratio of 1:0.1:6. A horizontal flow pump was used to introduce the mixture into the reactor. After cooling in a condenser, samples were taken for analysis. Gas chromatography analysis showed a conversion rate of 100% and a selectivity of 98.7%. The collected reaction solution was desolventized to obtain a crude product, which was recrystallized to obtain o-nitrobenzaldehyde with a purity of 99.93% (GC).

[0050] Example 2

[0051] 10g of Cu, which has been prepared into granular form, was packed into a fixed-bed reactor. 0.5 Co 0.5 Al2O4 catalyst, O2 was introduced to maintain a constant pressure of 2.0 MPa, preheated to 80°C, reaction tube temperature was 90°C, and mass hourly space velocity was 1.0 h⁻¹. -1 The raw material ratio was: o-nitrobenzyl alcohol, TEMPO, and dichloromethane in a molar ratio of 1:0.1:6. A horizontal flow pump was used to introduce the mixture into the reactor. After cooling in a condenser, samples were taken for analysis. Gas chromatography analysis showed a conversion rate of 21.2% and a selectivity of 98.3%.

[0052] Example 3

[0053] 10g of Cu, which has been prepared into granular form, was packed into a fixed-bed reactor. 0.5 Co 0.5 Al2O4 catalyst, O2 introduced to maintain a constant pressure of 2.0 MPa, preheated to 80℃, reaction tube temperature 130℃, mass hourly space velocity 1.0 h⁻¹ -1 The raw material ratio was: o-nitrobenzyl alcohol, TEMPO, and dichloromethane in a molar ratio of 1:0.1:6. A horizontal flow pump was used to introduce the mixture into the reactor. After cooling in a condenser, samples were taken for analysis. Gas chromatography analysis showed a conversion rate of 100% and a selectivity of 90.6%. The collected reaction solution was desolventized to obtain a crude product, which was recrystallized to obtain o-nitrobenzaldehyde with a purity of 99.87% (GC).

[0054] Example 4

[0055] A method for preparing o-nitrobenzaldehyde includes the following steps.

[0056] 10g of Cu, which has been prepared into granular form, was packed into a fixed-bed reactor. 0.5 Co 0.5 Al2O4 catalyst, O2 introduced to maintain a constant pressure of 2.0 MPa, preheated to 80℃, reaction tube temperature 120℃, mass hourly space velocity 1.0 h⁻¹ -1The raw material ratio was: o-nitrobenzyl alcohol, TEMPO, and dichloromethane in a molar ratio of 1:0.05:6. A horizontal flow pump was used to introduce the mixture into the reactor. After cooling in a condenser, samples were taken for analysis. Gas chromatography analysis showed a conversion rate of 100% and a selectivity of 98.8%. The collected reaction solution was desolventized to obtain a crude product, which was then recrystallized to obtain o-nitrobenzaldehyde with a purity of 99.89% (GC).

[0057] Example 5

[0058] A method for preparing o-nitrobenzaldehyde includes the following steps.

[0059] 10g of Cu, which has been prepared into granular form, was packed into a fixed-bed reactor. 0.5 Co 0.5 Al2O4 catalyst, O2 introduced to maintain a constant pressure of 2.0 MPa, preheated to 80℃, reaction tube temperature 120℃, mass hourly space velocity 1.0 h⁻¹ -1 The raw material ratio was: o-nitrobenzyl alcohol, TEMPO, and dichloromethane in a molar ratio of 1:0.03:6. A horizontal flow pump was used to introduce the mixture into the reactor. After cooling in a condenser, samples were taken for analysis. Gas chromatography analysis showed a conversion rate of 90.11% and a selectivity of 75.3%.

[0060] Example 6

[0061] A method for preparing o-nitrobenzaldehyde includes the following steps.

[0062] 10g of Cu, which has been prepared into granular form, was packed into a fixed-bed reactor. 0.5 Co 0.5 Al2O4 catalyst, O2 introduced to maintain a constant pressure of 2.0 MPa, preheated to 80℃, reaction tube temperature 120℃, mass hourly space velocity (WHSV) 0.5 h⁻¹ -1 The raw material ratio was: o-nitrobenzyl alcohol, TEMPO, and dichloromethane in a molar ratio of 1:0.03:6. A horizontal flow pump was used to introduce the mixture into the reactor. After cooling in a condenser, samples were taken for analysis. Gas chromatography analysis showed a conversion rate of 100% and a selectivity of 98.8%. The collected reaction solution was desolvated to obtain a crude product, which was recrystallized to obtain o-nitrobenzaldehyde with a purity of 99.91% (GC).

[0063] Example 7

[0064] 10g of Cu, which has been prepared into granular form, was packed into a fixed-bed reactor. 0.5 Co 0.5 Al2O4 catalyst, O2 introduced to maintain a constant pressure of 2.0 MPa, preheated to 80℃, reaction tube temperature 120℃, mass hourly space velocity (WHSV) 0.5 h⁻¹ -1The raw material ratio was: o-nitrobenzyl alcohol, TEMPO, and dichloromethane in a molar ratio of 1:0.01:6. A horizontal flow pump was used to introduce the mixture into the reactor. After cooling in a condenser, samples were taken for analysis. Gas chromatography analysis showed a conversion rate of 81.9% and a selectivity of 100%.

[0065] Example 8

[0066] A method for preparing o-nitrobenzaldehyde includes the following steps.

[0067] 10g of Cu, which has been prepared into granular form, was packed into a fixed-bed reactor. 0.5 Co 0.5 Al2O4 catalyst, O2 was introduced to maintain a constant pressure of 2.0 MPa, preheated to 80℃, reaction tube temperature 120℃, and mass hourly space velocity (WHSV) 0.25 h⁻¹. -1 The raw material ratio was: o-nitrobenzyl alcohol, TEMPO, and dichloromethane in a molar ratio of 1:0.01:6. A horizontal flow pump was used to introduce the mixture into the reactor. After cooling in a condenser, samples were taken for analysis. Gas chromatography analysis showed a conversion rate of 100% and a selectivity of 98.9%. The collected reaction solution was desolvated to obtain a crude product, which was then recrystallized to obtain o-nitrobenzaldehyde with a purity of 99.95% (GC).

[0068] Example 9

[0069] 10g of Cu, which has been prepared into granular form, was packed into a fixed-bed reactor. 0.5 Co 0.5 Al2O4 catalyst, O2 was introduced to maintain a constant pressure of 2.0 MPa, preheated to 80℃, reaction tube temperature 120℃, and mass hourly space velocity (WHSV) 0.25 h⁻¹. -1 The raw material ratio was: o-nitrobenzyl alcohol, TEMPO, and 1,2-dichloroethane in a molar ratio of 1:0.01:6. A horizontal flow pump was used to introduce the mixture into the reactor. After cooling in a condenser, samples were taken for analysis. Gas chromatography analysis showed a conversion rate of 100% and a selectivity of 95.3%. The collected reaction solution was desolvated to obtain a crude product, which was recrystallized to obtain o-nitrobenzaldehyde with a purity of 99.91% (GC).

[0070] Example 10

[0071] A method for preparing o-nitrobenzaldehyde includes the following steps.

[0072] 10g of Cu, which has been prepared into granular form, was packed into a fixed-bed reactor. 0.5 Co 0.5 Al2O4 catalyst, O2 was introduced to maintain a constant pressure of 2.0 MPa, preheated to 80℃, reaction tube temperature 120℃, and mass hourly space velocity (WHSV) 0.25 h⁻¹. -1The raw material ratio was: o-nitrobenzyl alcohol, TEMPO, and hot water at 50℃ in a molar ratio of 1:0.01:6. A horizontal flow pump was used to introduce the mixture into the reactor. After cooling in a condenser, samples were taken for analysis. Gas chromatography analysis showed a conversion rate of 81.2% and a selectivity of 90.6%.

[0073] Example 11

[0074] A method for preparing o-nitrobenzaldehyde includes the following steps.

[0075] 10g of Cu, which has been prepared into granular form, was packed into a fixed-bed reactor. 0.5 Co 0.5 Al2O4 catalyst, O2 was introduced to maintain a constant pressure of 2.0 MPa, preheated to 80℃, reaction tube temperature 120℃, and mass hourly space velocity (WHSV) 0.25 h⁻¹. -1 The raw material ratio was: o-nitrobenzyl alcohol, TEMPO, and chloroform in a molar ratio of 1:0.01:6. A horizontal flow pump was used to introduce the mixture into the reactor. After cooling in a condenser, samples were taken for analysis. Gas chromatography analysis showed a conversion rate of 100% and a selectivity of 97.8%. The collected reaction solution was desolventized to obtain a crude product, which was recrystallized to obtain o-nitrobenzaldehyde with a purity of 99.87% (GC).

[0076] Comparative Example 1

[0077] 10g of granular CuAl2O4 catalyst was packed into a fixed-bed reactor, O2 was introduced to maintain a constant pressure of 2.0 MPa, the preheating temperature was 80℃, the reaction tube temperature was 120℃, and the mass hourly space velocity was 0.25 h⁻¹. -1 The raw material ratio was: o-nitrobenzyl alcohol, TEMPO, and chloroform in a molar ratio of 1:0.01:6. A horizontal flow pump was used to introduce the mixture into the reactor. After cooling in a condenser, samples were taken for analysis. Gas chromatography analysis showed a conversion rate of 90.1% and a selectivity of 88.2%.

[0078] Comparative Example 2

[0079] 10g of granulated CoAl2O4 catalyst was packed into a fixed-bed reactor, O2 was introduced to maintain a constant pressure of 2.0 MPa, the preheating temperature was 80℃, the reaction tube temperature was 120℃, and the mass hourly space velocity was 0.25 h⁻¹. -1 The raw material ratio was: o-nitrobenzyl alcohol, TEMPO, and chloroform in a molar ratio of 1:0.01:6. A horizontal flow pump was used to introduce the mixture into the reactor. After cooling in a condenser, samples were taken for analysis. Gas chromatography analysis showed a conversion rate of 83.2% and a selectivity of 89.6%.

[0080] Comparative Example 3

[0081] 10g of granular CuCoAl2O4 catalyst (calcined at 400℃, lacking spinel structure) was packed into a fixed-bed reactor. O2 was introduced to maintain a constant pressure of 2.0 MPa, the preheating temperature was 80℃, the reaction tube temperature was 120℃, and the mass hourly space velocity was 0.25 h⁻¹. -1 The raw material ratio was: o-nitrobenzyl alcohol, TEMPO, and chloroform in a molar ratio of 1:0.01:6. A horizontal flow pump was used to introduce the mixture into the reactor. After cooling in a condenser, samples were taken for analysis. Gas chromatography analysis showed a conversion rate of 40.1% and a selectivity of 78.7%.

Claims

1. A spinel-structured Cu 0.5 Co 0.5 The method for preparing o-nitrobenzaldehyde by Al2O4 catalyst is characterized by... Using o-nitrobenzyl alcohol as a raw material, dissolved in an organic solvent, Cu 0.5 Co 0.5 Al2O4 spinel was used as a catalyst, TEMPO was added as a co-catalyst, and oxygen was introduced into a fixed bed to carry out the reaction. After the reaction was completed, o-nitrobenzaldehyde was obtained.

2. The spinel structure Cu according to claim 1 0.5 Co 0.5 A method for preparing o-nitrobenzaldehyde catalyzed by Al2O4 catalyst, characterized in that: Cu 0.5 Co 0.5 The preparation method of Al2O4 spinel catalyst is as follows: Soluble copper salt, soluble cobalt salt, and soluble aluminum salt were weighed in a molar ratio of 1:1:4 to prepare a mixed aqueous solution of metal salts. NaOH solution was used as a precipitant to obtain a coprecipitate. The coprecipitate was aged in a water bath at 55 °C for 12 h, then filtered and washed until the filtrate was neutral. The filter cake was dried, and finally, the spinel precursor was calcined in a muffle furnace at 900 °C for 6 h to obtain Cu. 0.5 Co 0.5 Al2O4.

3. The spinel structure Cu according to claim 2 0.5 Co 0.5 A method for preparing o-nitrobenzaldehyde catalyzed by Al2O4 catalyst, characterized in that: Cu 0.5 Co 0.5 Al₂O₄ spinel was used as a catalyst and granulated. The catalyst granules were loaded into a fixed-bed reactor, oxygen was introduced and the pressure was kept constant at 2.0 MPa, the preheating temperature was 80℃, the reaction temperature in the reaction tube was 90~120℃, and the mass hourly space velocity was 0.25~1.0 h⁻¹. -1 ; o-Nitrobenzyl alcohol, a co-catalyst, and an organic solvent were mixed in a molar ratio to obtain a mixture. The mixture was introduced into a reactor for reaction. After the reaction, the reaction solution was collected and desolventized to obtain a crude product. The crude product was recrystallized to obtain o-nitrobenzaldehyde.

4. The spinel structure Cu according to any one of claims 1-3 0.5 Co 0.5 A method for preparing o-nitrobenzaldehyde catalyzed by Al2O4 catalyst, characterized in that: The organic solvent is one of dichloromethane, chloroform, water, and 1,2-dichloroethane.

5. The spinel structure Cu according to claim 4 0.5 Co 0.5 A method for preparing o-nitrobenzaldehyde catalyzed by Al2O4 catalyst, characterized in that: The organic solvent is dichloromethane.

6. The spinel structure Cu according to claim 3 0.5 Co 0.5 A method for preparing o-nitrobenzaldehyde catalyzed by Al2O4 catalyst, characterized in that: The reaction temperature is 120 ℃.

7. The spinel structure Cu according to any one of claims 1-3 0.5 Co 0.5 A method for preparing o-nitrobenzaldehyde catalyzed by Al2O4 catalyst, characterized in that: The molar ratio of o-nitrobenzyl alcohol, co-catalyst, and organic solvent is 1:0.01~0.1:6.

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