Manganese oxide loaded cobalt-chromium catalyst, preparation thereof, and use thereof in synthesis of p-chlorobenzaldehyde

Abstract

Disclosed in the present invention are a manganese oxide loaded cobalt-chromium catalyst and a preparation method therefor, and the use of the catalyst in the selective catalytic oxidation of p-chlorotoluene to prepare p-chlorobenzaldehyde. The preparation steps comprise: weighing a certain amount of a manganese salt, weighing cobalt and chromium precursor metal salts according to the loading amount, dissolving them in deionized water, and stirring same to obtain a mixed solution. After the above substances are fully dissolved at a certain temperature, a certain amount of acid is added, and the mixture is continuously heated and stirred. After the reaction is finished, the solid mixture is filtered under suction and washed, then roasted to obtain the catalyst, and finally the catalyst is used for the catalytic oxidation of p-chlorotoluene to prepare p-chlorobenzaldehyde. The catalyst of the present invention has a relatively low preparation cost, is easy to recycle subsequently, and is environmentally friendly and pollution-free. Moreover, the reaction conditions are relatively mild, and both the reaction conversion rate and selectivity are greatly improved. It has a good industrialization prospect.

Description

Manganese oxide supported cobalt chromium catalyst, preparation and application in synthesis of p-chlorobenzaldehyde Technical Field

[0001] The present invention relates to the technical field of organic catalysis, and in particular to a manganese oxide-supported cobalt-chromium catalyst and a preparation method thereof, as well as application of the catalyst in the preparation of p-chlorobenzaldehyde by highly selective catalytic oxidation of p-chlorotoluene. Background Art

[0002] p-Chlorobenzaldehyde is a widely used fine organic chemical intermediate in pharmaceuticals, dye intermediates, pesticides, and other fields. It is used to synthesize drugs such as fenalol and aminophenylbutyric acid, as well as plant growth regulators such as uniconazole and paclobutrazol. The traditional chlorination hydrolysis method uses chlorine gas and soluble metal salts for the reaction, but this method has the disadvantages of demanding equipment conditions and polluting the environment with wastewater. With the development of green chemistry, clean and environmentally friendly oxidants such as H2O2 and O2 have become increasingly popular in the fine chemical industry. While hydrogen peroxide plays an important role in reducing three wastes and achieving green chemical production, the risks associated with H2O2 storage and transportation make it unsuitable for industrial use. Oxygen, on the other hand, is cheap, readily available, safe, and convenient, making its use as an oxidant in the direct oxidation of p-chlorotoluene to produce p-chlorobenzaldehyde a hot research topic. However, this process places high demands on catalysts, and the development of highly active and selective catalysts is a key research priority.

[0003] Regarding this route, Cai Minmin (Air Oxidation of p-Chlorotoluene to Prepare p-Chlorobenzaldehyde, Cai Minmin, Wang Xueyan, Cai Chun, Wei Yunyang, Lü Chunxu, Chemistry World 2002) studied the oxidation of p-chlorotoluene in air and oxygen atmospheres and found that oxygen was more effective than air oxidation as an oxidant, with a yield of up to 28%, but the reaction activity was still too low. Hu Anjun et al. (Selective Oxidation of p-chlorotoluene with Co(OAc)2 / MnSO4 / KBr in acetic acid-water medium, Hu AJ, Lü C X, Wang HY, Li BD, Catalysis Communications 8, 2007, 1279-1283) used acetic acid-water as a reaction solvent and cobalt and manganese salts as catalysts to oxidize p-chlorotoluene to prepare p-chlorobenzaldehyde at normal pressure and low temperature. The conversion rate was 33.7% and the p-chlorobenzaldehyde selectivity was 66.6%. Although this method is simple and low in cost, it has disadvantages such as the difficulty in separating and recovering the homogeneous catalyst and the low selectivity of the target product. Patent document CN101138729A studied the use of metal active components cobalt and manganese loaded on Al2O3 for liquid-phase oxidation of para-chlorotoluene. After adjusting conditions such as oxygen flow rate, temperature, and the ratio of active components of the catalyst, the conversion rate of para-chlorotoluene reached 43.7%, but the catalytic activity of the catalyst still has room for improvement.

[0004] The method for preparing p-chlorobenzaldehyde by liquid-phase oxygen oxidation of p-chlorotoluene has the advantages of simple and mild conditions, low pollution, and easy separation of raw materials and solvents for recycling. While the above methods optimize and improve the preparation of p-chlorobenzaldehyde by oxidation of p-chlorotoluene from different perspectives, some problems still need to be addressed: low oxidant utilization efficiency and low catalyst activity; in addition to the target product p-chlorobenzaldehyde, the oxidation of p-chlorotoluene also easily produces byproducts such as p-chlorobenzyl alcohol, p-chlorobenzoic acid, and 4-chlorobenzyl acetate, resulting in low selectivity; homogeneous systems composed of manganese salts as catalysts produce a large amount of wastewater, and the catalyst cannot be recycled. Therefore, it is of great significance to develop heterogeneous catalysts suitable for this reaction to further improve the reaction activity and target product selectivity.

[0005] Summary of the Invention

[0006] To address the problems of low catalytic activity and selectivity in the prior art for preparing p-chlorobenzaldehyde, the present invention provides a supported cobalt-chromium catalyst and preparation method for the highly selective catalytic oxidation of p-chlorotoluene to produce p-chlorobenzaldehyde. The catalyst's active components and ratios are adjusted, and reaction system conditions are optimized to achieve highly selective preparation of p-chlorobenzaldehyde. Furthermore, the catalyst has a simple preparation process, is easily separable, and can be washed, dried, and reused after high-temperature calcination, facilitating industrial production.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0008] A method for preparing a manganese oxide-supported cobalt-chromium catalyst comprises: dissolving a manganese salt and cobalt and chromium precursor metal salts in deionized water, and stirring to obtain a mixed solution; adding acid to the mixed solution, heating and stirring to react, filtering after the reaction is completed, drying, and calcining to obtain the cobalt-chromium supported catalyst.

[0009] Furthermore, a method for preparing a manganese oxide-supported cobalt-chromium catalyst comprises the steps of:

[0010] (1) Weigh a certain amount of manganese salt, and weigh cobalt and chromium precursor metal salts according to the loading amount, dissolve them in deionized water, and stir to obtain a mixed solution.

[0011] (2) After the above substances are fully dissolved at a certain temperature, add a certain amount of acid and continue heating and stirring.

[0012] (3) After the reaction is completed, the solid mixture is filtered and washed, and then dried in an oven. The dark brown powder obtained after calcination is the cobalt-chromium supported catalyst.

[0013] In step (1), the manganese salt may be at least one of permanganate, chloride, acetate, acetylacetonate, and nitrate, or a mixture of more thereof; the manganese salt is preferably at least two of permanganate (sodium or potassium), acetate (manganese acetate), and nitrate (manganese nitrate). The metal salt may be at least one of chloride, acetate, acetylacetonate, and nitrate, or a mixture of more thereof; preferably, the metal salt is preferably one or both of acetate and nitrate. Specifically, the cobalt precursor metal salt is selected from at least one of cobalt chloride, cobalt acetate, cobalt acetylacetonate, and cobalt nitrate, or a mixture of more thereof; preferably, the cobalt precursor metal salt is selected from one or both of cobalt acetate and cobalt nitrate. The chromium precursor metal salt is selected from at least one of chromium chloride, chromium acetate, chromium acetylacetonate, and chromium nitrate, or a mixture of more thereof; preferably, the chromium precursor metal salt is selected from one or both of chromium acetate and chromium nitrate.

[0014] As a specific embodiment, the manganese salt is a mixture of permanganate (potassium salt, sodium salt, etc.) and manganese acetate, with a molar ratio of 1:1 to 2; more preferably 1:1 to 1.5.

[0015] In step (1), the loading amount of the Co and Cr metal elements is preferably 2 to 15 wt % of the mass of Mn in the support. As a specific option, the support is calculated based on the amount of potassium permanganate added. Based on the mass of manganese in potassium permanganate, the loading amount is 4 to 10%, more preferably 4 to 8%, and even more preferably 5 to 7%.

[0016] Preferably, the mass ratio of the elements Co and Cr is 1:3 to 3:1; more preferably 1:2 to 2:1; and even more preferably 1:1.

[0017] As an option, in the mixed solution, the concentration of Co salt (cobalt precursor metal salt) is 3.5-18.5 g / L; more preferably 4-15 g / L, and even more preferably 4-10 g / L; the concentration of Cr salt (chromium precursor metal salt) is 5.5-35.5 g / L; more preferably 8-30 g / L; and even more preferably 10-20 g / L.

[0018] In step (2), the stirring time is 12 to 48 hours, more preferably 16 to 32 hours. The heating temperature is preferably 70 to 120°C, more preferably 90 to 110°C.

[0019] In step (2), the acid may be at least one of hydrochloric acid, acetic acid, nitric acid, sulfuric acid, and phosphoric acid, and is further optimized to be one of hydrochloric acid and nitric acid.

[0020] In step (2), taking the amount of potassium permanganate added as 7.08 g as an example, the amount of acid added is 2 to 8 mL, more preferably 3 to 5 mL. That is, the mass volume ratio of the acid added relative to potassium permanganate is 0.25 to 1.13 mL / g, more preferably 0.4 to 0.75 mL / g.

[0021] In step (3), the drying temperature is preferably 70 to 120° C., more preferably 80 to 100° C., and the drying time is preferably 4 to 15 hours, more preferably 8 to 10 hours.

[0022] In step (3), the calcination temperature is 300-700° C., more preferably 400-500° C., and the calcination time is preferably 3-6 hours, more preferably 4-5 hours.

[0023] The present invention provides a supported cobalt-chromium catalyst prepared by the preparation method. The supported cobalt-chromium catalyst is a multi-metal oxide formed by adding cobalt and chromium in a certain loading amount into a manganese oxide carrier.

[0024] Preferably, the cobalt and chromium loadings in the supported cobalt-chromium catalyst are 2 to 15 wt % respectively.

[0025] The present invention also provides application of the manganese oxide-supported cobalt-chromium catalyst in highly selectively catalyzing the oxidation of p-chlorotoluene to prepare p-chlorobenzaldehyde.

[0026] As a general inventive concept, the present invention also provides a method for preparing p-chlorobenzaldehyde by catalytic oxidation of p-chlorotoluene: after uniformly mixing the manganese oxide-supported cobalt-chromium catalyst, a solvent, a bromine initiator, and p-chlorotoluene, a certain amount of oxygen is introduced at 60-110° C. (preferably 80-110° C., more preferably 90-110° C.) to carry out a catalytic oxidation reaction to obtain the target product p-chlorobenzaldehyde.

[0027] The solvent is preferably at least one of acetic acid, acetonitrile, acetic anhydride, and water, more preferably acetic acid and water. The solvent is a mixed solvent of acetic acid and water, with the volume ratio of acetic acid to water being 3 to 8:1. The volume ratio of para-chlorotoluene to the added solvent is 1 / 3 to 14; preferably, the volume ratio of acetic acid to water is 4 to 6:1. The volume ratio of para-chlorotoluene to the added solvent is 1 / 5 to 14, and preferably, the volume ratio of para-chlorotoluene to the added solvent is 1 / 8 to 14.

[0028] The bromine initiator is preferably one of KBr, HBr, and NaBr. The volume ratio of the para-chlorotoluene to the bromine initiator is 1 mL / 20 to 100 μL, and the bromine initiator is hydrobromic acid having a mass percentage concentration of 30% to saturated concentration. As a further preferred embodiment, the volume ratio of the para-chlorotoluene to the bromine initiator is 1 mL / 35 to 70 μL; and even more preferably, 1 mL / 40 to 60 μL.

[0029] The volume ratio of the p-chlorotoluene, the solvent and the bromine initiator is preferably 1:(2-14):(0.01-0.1), and the oxygen flow rate is preferably 20-100 mL / min, more preferably 50-100 mL / min; and even more preferably 60-100 mL / min.

[0030] The mass ratio of the para-chlorotoluene to the highly selective manganese oxide-supported cobalt-chromium catalyst is preferably 1:(0.01-0.1); preferably, the mass ratio of the para-chlorotoluene to the highly selective manganese oxide-supported cobalt-chromium catalyst is 1:(0.03-0.1); further preferably, it is 1:(0.04-0.1).

[0031] The catalytic oxidation reaction time is preferably 4 to 24 hours, more preferably 10 to 24 hours, and even more preferably 6 to 12 hours.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The present invention provides a type of supported cobalt-chromium catalyst, which has a simple preparation method, readily available raw materials, low price, and is easy to separate and recover.

[0034] 2. The addition of cobalt and chromium into the manganese oxide catalyst increases the specific surface area of ​​the catalyst and improves the catalytic activity of the catalyst in the catalytic oxidation reaction.

[0035] 3. The catalytic oxidation conditions for preparing p-chlorobenzaldehyde from p-chlorotoluene provided by the present invention are mild, and the reaction conversion rate and selectivity are greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG1 is a SEM image of the cobalt- and chromium-doped manganese oxide catalyst (S1) prepared in Example 1.

[0037] FIG2 is a TEM image of the cobalt- and chromium-doped manganese oxide catalyst (S1) prepared in Example 1. DETAILED DESCRIPTION

[0038] The present invention will be further described below with reference to the accompanying drawings and specific examples. It should be understood that these examples are intended to illustrate the present invention only and are not intended to limit the scope of the present invention. The operating methods in the following examples where specific conditions are not specified are generally performed under conventional conditions or the conditions recommended by the manufacturer. The raw materials used in the following specific embodiments were purchased from the market. Unless otherwise specified, room temperature is 25°C.

[0039] Example 1

[0040] The first step is to prepare manganese oxide-supported cobalt-chromium catalyst:

[0041] The catalytic material was prepared by a high-temperature reflux method. First, 7.08 g of potassium permanganate and 14.7 g of manganese acetate tetrahydrate were weighed. Then, according to the metal loading mass of 6 wt%, and the mass ratio of Co and Cr was 1:1, 1.28 g of cobalt acetate and 3.29 g of chromium nitrate nine water were weighed and dissolved in 200 mL of deionized water. The mixture was thoroughly stirred at 90 ° C to form a mixed solution. Then, 3.5 mL of nitric acid was added to the mixed solution, and reflux stirring was continued for 24 hours. After the reaction was completed, the solid mixture was filtered and washed, and dried at 90 ° C overnight. The dried catalyst precursor was collected and heated to 400 ° C in a muffle furnace at a heating rate of 2 ° C / min and maintained for 4 hours. The prepared catalyst was named CoCr@MnO x (denoted as S1).

[0042] In the second step, catalytic oxidation reaction, the S1 catalyst (0.05 g) prepared in the first step and p-chlorotoluene (1 mL, 1.08 g) were added to 10 mL of acetic acid and 2 mL of water in a 50 mL three-necked flask. Then, 50 μL of HBr (40 wt%) was added and the mixture was reacted at 100°C and an oxygen flow rate of 80 mL / min for 12 hours. Gas chromatography analysis revealed a p-chlorotoluene conversion of 94.8%, a p-chlorobenzaldehyde selectivity of 94.3%, and a yield of 89.5%.

[0043] Comparative Example 1

[0044] The first step is to prepare the catalyst: different from Example 1, the above manganese oxide supported cobalt chromium catalyst CoCr@MnO is prepared by gel method. x . First weigh 14.7g of manganese acetate tetrahydrate, then weigh 1.28g of cobalt acetate and 3.29g of chromium nitrate nonahydrate according to the metal loading mass of 6wt% and the mass ratio of Co and Cr of 1:1, dissolve them in 50mL of anhydrous ethanol, and stir thoroughly at 60°C to form a purple-red mixed solution. Then add 3.24g of oxalic acid solution (oxalic acid is dissolved in 150mL of deionized water) to the above mixed solution, pour it into the above liquid, and continue magnetic stirring for 1h. After the reaction is completed, filter and wash the solid mixture, and dry it at 60°C overnight. Collect the dried catalyst precursor, heat it to 400°C in a muffle furnace at a heating rate of 2°C / min and maintain it for 4h. The prepared catalyst is named CoCr@MnO x (denoted as D1).

[0045] In the second step, catalytic oxidation reaction, 0.05 g of the D1 catalyst prepared in the first step and 1 mL of p-chlorotoluene (1.08 g) were added to 10 mL of acetic acid and 2 mL of water in a 50 mL three-necked flask. Then, 50 μL of HBr was added and the mixture was reacted at 100°C and an oxygen flow rate of 80 mL / min for 12 hours. Gas chromatography analysis revealed a p-chlorotoluene conversion of 76.4%, a p-chlorobenzaldehyde selectivity of 82.5%, and a yield of 63.0%.

[0046] Comparative Example 2

[0047] The first step is to prepare the catalyst: different from Example 1, the coprecipitation method is used to prepare the above manganese oxide supported cobalt chromium catalyst CoCr@MnO x . First weigh 7.08g of potassium permanganate and 14.7g of manganese acetate tetrahydrate, then weigh 1.28g of cobalt acetate and 3.29g of chromium nitrate nonahydrate according to the metal loading mass of 6wt% and the mass ratio of Co and Cr of 1:1, dissolve them in 200mL of deionized water, and stir thoroughly at 90°C to form a mixed solution. Then add 5mL of NaOH solution precipitant with a concentration of 1mol / L to the above mixed solution, and continue stirring for 24h. The solid mixture was washed by filtration and dried at 90°C overnight. The dried catalyst precursor was collected and heated to 400°C in a muffle furnace at a heating rate of 2°C / min and maintained for 4h. The prepared catalyst is named CoCr@MnO x (denoted as D2).

[0048] In the second step, catalytic oxidation reaction, the D2 catalyst (0.05 g) prepared in the first step and p-chlorotoluene (1 mL, 1.08 g) were added to 10 mL of acetic acid and 2 mL of water in a 50 mL three-necked flask. Then, 50 μL of HBr was added and the mixture was reacted at 100°C and an oxygen flow rate of 80 mL / min for 12 hours. Gas chromatography analysis revealed a p-chlorotoluene conversion of 46.2%, a p-chlorobenzaldehyde selectivity of 62.1%, and a yield of 28.7%.

[0049] Comparative Example 3

[0050] The first step is catalyst preparation: According to a preparation method similar to that in Example 1, the catalyst is prepared without adding the doping components cobalt and chromium. First, weigh 7.08g of potassium permanganate and 14.7g of manganese acetate tetrahydrate, dissolve them in 200mL of deionized water, and stir them thoroughly at 90°C to form a mixed solution. Then add 3.5mL of nitric acid to the mixed solution, and continue to reflux and stir for 24h. After the reaction is completed, filter and wash the solid mixture, and dry it at 90°C overnight. Collect the dried catalyst precursor, heat it to 400°C in a muffle furnace at a heating rate of 2°C / min and maintain it for 4h. The prepared catalyst is named MnO x (denoted as D3).

[0051] In the second step, catalytic oxidation reaction, the D3 catalyst (0.05 g) prepared in the first step and p-chlorotoluene (1 mL, 1.08 g) were added to a 50 mL three-necked flask, along with 10 mL of acetic acid, 2 mL of water, and 50 μL of HBr. The reaction was carried out at 100°C and an oxygen flow rate of 80 mL / min for 12 hours. Gas chromatography analysis revealed a p-chlorotoluene conversion of 90.1%, a p-chlorobenzaldehyde selectivity of 67.9%, and a yield of 61.2%.

[0052] Example 2

[0053] The first step is to prepare manganese oxide-supported cobalt-chromium catalyst:

[0054] The catalytic material was prepared by a high-temperature reflux method. First, 7.08g of potassium permanganate and 14.7g of manganese acetate tetrahydrate were weighed. Then, according to the metal loading mass of 6wt% and the mass ratio of Co and Cr of 1:2, 1.28g of cobalt acetate and 6.58g of chromium nitrate nine water were weighed and dissolved in 200mL of deionized water. The mixture was thoroughly stirred at 90°C to form a mixed solution. Then, 3.5mL of nitric acid was added to the mixed solution, and reflux stirring was continued for 24h. After the reaction was completed, the solid mixture was filtered and washed, and dried at 90°C overnight. The dried catalyst precursor was collected and heated to 400°C in a muffle furnace at a heating rate of 2°C / min and maintained for 4h. The prepared catalyst was named CoCr2@MnO x(denoted as S2).

[0055] In the second step, catalytic oxidation reaction, the S2 catalyst (0.05 g) prepared in the first step and para-chlorotoluene (1 mL, 1.08 g) were added to a 50 mL three-necked flask, along with 10 mL of acetic acid, 2 mL of water, and 50 μL of HBr. The reaction was carried out at 100°C and an oxygen flow rate of 80 mL / min for 12 hours. Gas chromatography analysis revealed a para-chlorotoluene conversion of 92.1%, a selectivity of 81%, and a yield of 74.6%.

[0056] Example 3

[0057] The first step is to prepare manganese oxide-supported cobalt-chromium catalyst:

[0058] The catalytic material was prepared by a high-temperature reflux method. First, 7.08g of potassium permanganate and 14.7g of manganese acetate tetrahydrate were weighed. Then, according to the metal loading mass of 6wt% and the mass ratio of Co and Cr of 2:1, 2.56g of cobalt acetate and 3.29g of chromium nitrate nonahydrate were weighed and dissolved in 200mL of deionized water. The mixture was thoroughly stirred at 90°C to form a mixed solution. Then, 3.5mL of nitric acid was added to the mixed solution, and reflux stirring was continued for 24h. After the reaction was completed, the solid mixture was filtered and washed, and dried at 90°C overnight. The dried catalyst precursor was collected and heated to 400°C in a muffle furnace at a heating rate of 2°C / min and maintained for 4h. The prepared catalyst was named Co2Cr@MnO x (denoted as S3).

[0059] In the second step, catalytic oxidation reaction, the S3 catalyst (0.05 g) prepared in the first step and p-chlorotoluene (1 mL, 1.08 g) were added to a 50 mL three-necked flask, along with 10 mL of acetic acid, 2 mL of water, and 50 μL of HBr. The reaction was carried out at 100°C and an oxygen flow rate of 80 mL / min for 12 hours. Gas chromatography analysis revealed a p-chlorotoluene conversion of 67.5%, a selectivity of 92.1%, and a yield of 62.1%.

[0060] Example 4

[0061] The first step is to prepare the manganese oxide-supported cobalt catalyst:

[0062] The catalytic material was prepared by a high-temperature reflux method. First, 7.08 g of potassium permanganate and 14.7 g of manganese acetate tetrahydrate were weighed, and then 1.28 g of cobalt acetate was weighed according to the metal loading mass of 6 wt%, dissolved in 200 mL of deionized water, and thoroughly stirred at 90 ° C to form a mixed solution. Then 3.5 mL of nitric acid was added to the above mixed solution, and reflux stirring was continued for 24 hours. After the reaction was completed, the solid mixture was filtered and washed, and dried at 90 ° C overnight. The dried catalyst precursor was collected and heated to 400 ° C in a muffle furnace at a heating rate of 2 ° C / min and maintained for 4 hours. The prepared catalyst was named Co@MnO x (denoted as S4).

[0063] In the second step, catalytic oxidation reaction, the S4 catalyst (0.05 g) prepared in the first step and p-chlorotoluene (1 mL, 1.08 g) were added to a 50 mL three-necked flask, along with 10 mL of acetic acid, 2 mL of water, and 50 μL of HBr. The reaction was carried out at 100°C and an oxygen flow rate of 80 mL / min for 12 hours. Gas chromatography analysis revealed a p-chlorotoluene conversion of 85.5%, a p-chlorobenzaldehyde selectivity of 71.9%, and a yield of 61.5%.

[0064] Example 5

[0065] The first step is to prepare manganese oxide-supported cobalt-chromium catalyst:

[0066] The catalytic material was prepared by a high-temperature reflux method. First, 7.08 g of potassium permanganate and 14.7 g of manganese acetate tetrahydrate were weighed, and then 3.29 g of chromium nitrate nine water was weighed according to the metal loading mass of 6 wt%, dissolved in 200 mL of deionized water, and thoroughly stirred at 90 ° C to form a mixed solution. Then, 3.5 mL of nitric acid was added to the above mixed solution, and reflux stirring was continued for 24 hours. After the reaction was completed, the solid mixture was filtered and washed, and dried at 90 ° C overnight. The dried catalyst precursor was collected and heated to 400 ° C in a muffle furnace at a heating rate of 2 ° C / min and maintained for 4 hours. The prepared catalyst was named Cr@MnO x (denoted as S5).

[0067] In the second step, catalytic oxidation reaction, the S5 catalyst (0.05 g) prepared in the first step and p-chlorotoluene (1 mL, 1.08 g) were added to 10 mL of acetic acid and 2 mL of water in a 50 mL three-necked flask. Then, 50 μL of HBr was added and the mixture was reacted at 100°C and an oxygen flow rate of 80 mL / min for 12 hours. Gas chromatography analysis revealed a p-chlorotoluene conversion of 87.6%, a p-chlorobenzaldehyde selectivity of 75.2%, and a yield of 65.8%.

[0068] Example 6

[0069] Catalyst S1 (0.05 g) and p-chlorotoluene (1 mL, 1.08 g) were added to 10 mL of acetic acid, 2 mL of water, and 25 μL of HBr. The reaction was carried out at 100°C and an oxygen flow rate of 80 mL / min for 12 h. Gas chromatography analysis revealed a p-chlorotoluene conversion of 34%, a p-chlorobenzaldehyde selectivity of 87.5%, and a yield of 29.8%.

[0070] Example 7

[0071] Catalyst S1 (0.05 g) and p-chlorotoluene (1 mL, 1.08 g) were added to 10 mL of acetic acid and 2 mL of water, followed by 75 μL of HBr. The reaction was carried out at 100°C and an oxygen flow rate of 80 mL / min for 12 h. Gas chromatography analysis revealed a p-chlorotoluene conversion of 29.8%, a p-chlorobenzaldehyde selectivity of 74.2%, and a yield of 22.1%.

[0072] Example 8

[0073] Catalyst S1 (0.05 g) and p-chlorotoluene (1 mL, 1.08 g) were added to 10 mL of acetic acid and 2 mL of water, followed by 50 μL of HBr. The reaction was carried out at 90°C and an oxygen flow rate of 80 mL / min for 12 h. Gas chromatography-mass spectrometry analysis revealed a p-chlorotoluene conversion of 87.6%, a p-chlorobenzaldehyde selectivity of 73.7%, and a yield of 64.6%.

[0074] Example 9

[0075] Catalyst S1 (0.05 g) and p-chlorotoluene (1 mL, 1.08 g) were added to 10 mL of acetic acid and 2 mL of water, followed by 50 μL of HBr. The reaction was carried out at 80°C and an oxygen flow rate of 80 mL / min for 12 h. Gas chromatography analysis revealed a p-chlorotoluene conversion of 92%, a p-chlorobenzaldehyde selectivity of 64.6%, and a yield of 59.4%.

[0076] Example 10

[0077] Catalyst S1 (0.05 g) and p-chlorotoluene (1 mL, 1.08 g) were added to 10 mL of acetic acid and 2 mL of water, followed by 50 μL of HBr. The reaction was carried out at 110°C and an oxygen flow rate of 80 mL / min for 12 h. Gas chromatography analysis revealed a p-chlorotoluene conversion of 98.1%, a p-chlorobenzaldehyde selectivity of 79.1%, and a yield of 77.5%.

[0078] Example 11

[0079] Catalyst S1 (0.05 g) and p-chlorotoluene (1 mL, 1.08 g) were added to 8 mL of acetic acid, 2 mL of water, and 50 μL of HBr. The reaction was carried out at 100°C and an oxygen flow rate of 80 mL / min for 12 h. Gas chromatography analysis revealed a p-chlorotoluene conversion of 99%, a p-chlorobenzaldehyde selectivity of 75.3%, and a yield of 74.5%.

[0080] Example 12

[0081] Catalyst S1 (0.05 g) and p-chlorotoluene (1 mL, 1.08 g) were added to 12 mL of acetic acid, 2 mL of water, and 50 μL of HBr. The reaction was continued at 100°C with an oxygen flow rate of 80 mL / min for 12 h. Gas chromatography analysis revealed a p-chlorotoluene conversion of 90.9%, a p-chlorobenzaldehyde selectivity of 85.2%, and a yield of 77.5%.

[0082] Example 13

[0083] Catalyst S1 (0.05 g) and p-chlorotoluene (1 mL, 1.08 g) were added to 10 mL of acetic acid, 1 mL of water, and 50 μL of HBr. The reaction was carried out at 100°C and an oxygen flow rate of 80 mL / min for 12 h. Gas chromatography analysis revealed a p-chlorotoluene conversion of 31%, a p-chlorobenzaldehyde selectivity of 71.9%, and a yield of 22.3%.

[0084] Example 14

[0085] Catalyst S1 (0.05 g) and p-chlorotoluene (1 mL, 1.08 g) were added to 10 mL of acetic acid and 2 mL of water, followed by 50 μL of HBr. The reaction was carried out at 100°C and an oxygen flow rate of 60 mL / min for 12 h. Gas chromatography analysis revealed a p-chlorotoluene conversion of 92.8%, a p-chlorobenzaldehyde selectivity of 74.4%, and a yield of 69.1%.

[0086] Example 15

[0087] Catalyst S1 (0.05 g) and p-chlorotoluene (1 mL, 1.08 g) were added to 10 mL of acetic acid, 2 mL of water, and 50 μL of HBr. The reaction was continued at 100°C with an oxygen flow rate of 100 mL / min for 12 h. Gas chromatography analysis revealed a p-chlorotoluene conversion of 99%, a p-chlorobenzaldehyde selectivity of 78.9%, and a yield of 78.1%.

[0088] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A method for preparing a manganese oxide-supported cobalt-chromium catalyst, characterized in that: include: Dissolving manganese salt and cobalt and chromium precursor metal salts in deionized water, and stirring to obtain a mixed solution; Acid is added to the mixed solution, and the mixture is heated and stirred for reaction. After the reaction is completed, the mixture is filtered, dried, and calcined to obtain the cobalt-chromium supported catalyst.

2. The preparation method according to claim 1, characterized in that: The manganese salt is selected from one or more of permanganate, chloride, acetate, acetylacetonate, and nitrate; the cobalt and chromium precursor metal salts are selected from one or more of chloride, acetate, acetylacetonate, and nitrate of cobalt and chromium, respectively.

3. The preparation method according to claim 1, characterized in that: The loading amounts of Co and Cr metal elements are 2 to 15 wt % based on the manganese element in the carrier, and the mass ratio of the two is 1:3 to 3:

1.

4. The preparation method according to claim 1, characterized in that: After adding the acid, the stirring time is 12 to 48 hours; the heating temperature is 70 to 120° C.; the acid is selected from one or more of hydrochloric acid, acetic acid, nitric acid, sulfuric acid, and phosphoric acid; when the manganese salt is potassium permanganate and manganese acetate, the mass volume ratio of the acid added is 0.25 to 1.13 mL / g relative to potassium permanganate.

5. The preparation method according to claim 1, characterized in that: The drying temperature is 80-100° C. and the time is 8-10 hours; the calcination temperature is 400-500° C. and the time is 4-5 hours.

6. The manganese oxide-supported cobalt-chromium catalyst prepared by the preparation method according to any one of claims 1 to 5.

7. A method for preparing p-chlorobenzaldehyde by catalytically oxidizing p-chlorotoluene with high selectivity, characterized in that: After uniformly mixing the manganese oxide-supported cobalt-chromium catalyst, solvent, bromine initiator and p-chlorotoluene as claimed in claim 6, oxygen is introduced at 60-110° C. to carry out catalytic oxidation reaction to obtain the target product p-chlorobenzaldehyde.

8. The method for preparing p-chlorobenzaldehyde by catalytically highly selective oxidation of p-chlorotoluene according to claim 7, characterized in that: The solvent is one or more of acetic acid, acetonitrile, acetic anhydride and water; the bromine initiator is one or more of KBr, HBr and NaBr.

9. The method for preparing p-chlorobenzaldehyde by catalytically highly selective oxidation of p-chlorotoluene according to claim 7, characterized in that: The volume ratio of the p-chlorotoluene to the bromine initiator is 1 mL / 20 to 100 μL, the bromine initiator is hydrobromic acid with a mass percentage concentration of 30% to a saturated concentration, and the oxygen flow rate is 20 to 100 mL / min; the mass ratio of the p-chlorotoluene to the manganese oxide-loaded cobalt-chromium catalyst is 1:(0.01 to 0.1); and the time of the catalytic oxidation reaction is 6 to 14 hours.

10. The method for preparing p-chlorobenzaldehyde by catalytically highly selective oxidation of p-chlorotoluene according to claim 7, characterized in that: The reaction is carried out at 80-110° C.; the solvent is a mixed solvent of acetic acid and water, and the volume ratio of acetic acid to water is 3-8:1; the volume ratio of p-chlorotoluene to the bromine initiator is 1 mL / 40-60 μL.

Images