Bimetal nitrogen-doped catalyst, and preparation method and application thereof

Abstract

The invention discloses a bimetallic nitrogen-doped catalyst as well as a preparation method and application thereof. The bimetallic nitrogen-doped catalyst comprises a carrier and a bimetallic component loaded on the carrier, the carrier is an MCM-41 molecular sieve; the bimetallic component comprises precious metal elements and non-precious metal elements; doped nitrogen in the bimetallic nitrogen-doped catalyst is obtained by roasting a nitrogen-containing compound raw material. The active bimetallic particle size of the catalyst used in the method is small and stable, the catalyst interacts with a nitrogen-containing substance and a carrier, glycollic acid can be subjected to reductive amination to prepare glycine, and the catalyst is easy to separate and has excellent cycle stability. The application potential of the method and the catalyst is great, and wide prospects are brought to various fields in the future.

Description

Technical Field

[0001] The present application relates to a bimetallic nitrogen-doped catalyst and a preparation method and application thereof, belonging to the technical field of chemical synthesis. Background Art

[0002] Glycine is an important bioactive molecule, widely used in the fields of medicine, cosmetics and food industry. At present, the traditional method of preparing glycine from glycolic acid mainly includes the Strecker method and the chloroacetic acid ammonolysis method. The Strecker method is to use glycolic acid and diamino compounds (such as dimethylamine, diethylamine, etc.) to react under alkaline conditions to generate glycine. The product selectivity is high, the purity is relatively high, and the waste of resources is reduced, but the use of cyanide is toxic, the operation risk is high, the by-products generated are more, the process is more complicated, and the cost is relatively high. In contrast, the chloroacetic acid ammonolysis method is to use chloroacetic acid and ammonia to react in the presence of urotropine catalyst to generate glycine. The method is simple in process and raw materials are easy to obtain, but the by-products generated in the production process are difficult to remove, resulting in a low purity of glycine, and the urotropine catalyst cannot be recycled, resulting in a waste of resources, and there is also an environmental pollution problem (China invention application file CN102838497A). Therefore, it is urgent to develop a new method for preparing glycine from glycolic acid with high selectivity and environmental stability to meet the market demand for high-quality glycine, reduce production costs, and reduce environmental impact. Summary of the invention

[0003] The present invention aims to develop an efficient heterogeneous bimetallic nitrogen-doped catalyst to reduce and aminize the hydroxyl group in glycolic acid to obtain amine group and prepare glycine. Glycolic acid can be obtained from a variety of sources. Biomass conversion is an important source of glycolic acid, including plant materials and microbial fermentation products. Through the fermentation process, some microorganisms can convert substrates into glycolic acid, and glycolic acid can also be obtained from microorganisms, plants or other organisms through biomanufacturing methods.

[0004] The method for preparing glycine from glycolic acid provided in the present application has a simple reaction process, low reaction cost, and reduced environmental impact. The catalyst bimetallic catalyst used in the method and the doped nitrogen and the carrier MCM-41 molecular sieve act synergistically with each other, wherein the doped nitrogen has a certain alkalinity and can stably fix the metal so as to reduce the metal particle size, and the nitrogen doping improves the electron transfer and strengthens the interaction between the metal and the carrier, which is conducive to the dehydrogenation of hydroxyl groups and further reduction amination to generate amine groups, thereby achieving efficient preparation of glycine, and the catalyst is easy to separate, and has broad application prospects.

[0005] According to one aspect of the present application, a bimetallic nitrogen-doped catalyst is provided, the bimetallic nitrogen-doped catalyst comprising a carrier and a bimetallic component loaded on the carrier;

[0006] The carrier is nitrogen-doped MCM-41 molecular sieve;

[0007] The bimetallic component includes a noble metal element and a non-noble metal element.

[0008] Optionally, the nitrogen in the bimetallic nitrogen-doped catalyst is obtained by calcining a nitrogen-containing compound raw material.

[0009] Optionally, the precious metal element is selected from at least one of Au, Ag, Pd, Pt, Rh, and Ru.

[0010] Optionally, the non-precious metal element is selected from at least one of Zn, Fe, Co, Ni, Mn and Cu.

[0011] Optionally, in the bimetallic nitrogen-doped catalyst, the loading amount of the noble metal element is 0.2 to 8.0 wt.%, and the loading amount of the non-noble metal element is 5 to 25 wt.%.

[0012] The mass of the bimetallic nitrogen-doped catalyst is calculated based on the mass of the carrier, the mass of the noble metal element is calculated based on the mass of the noble metal element, and the mass of the non-noble metal element is calculated based on the mass of the non-noble metal element.

[0013] Optionally, in the bimetallic nitrogen-doped catalyst, the loading amount of the precious metal element is independently selected from any value of 0.2wt.%, 0.5wt.%, 1.0wt.%, 3.0wt.%, 5.0wt.%, 6.0wt.%, 8.0wt.% or a range between any two of the above.

[0014] Optionally, in the bimetallic nitrogen-doped catalyst, the loading amount of the non-precious metal element is independently selected from any value of 5wt%, 6wt.%, 8wt.%, 10wt.%, 15wt.%, 20wt%, 25wt.%, or a range between any two of the above.

[0015] Optionally, in the bimetallic nitrogen-doped catalyst, the loading amount of the noble metal element is 0.5-3.0 wt.%, and the loading amount of the non-noble metal element is 6-8 wt.%.

[0016] According to another aspect of the present application, a method for preparing the bimetallic nitrogen-doped catalyst described above is provided, the preparation method comprising:

[0017] The mixture containing a metal precursor, a nitrogen-containing compound, an organic solvent and a carrier is reacted, vacuum dried, dried, pyrolyzed and reduced to obtain the bimetallic nitrogen-doped catalyst.

[0018] Optionally, the preparation method of the bimetallic nitrogen-doped catalyst comprises:

[0019] (1) mixing and stirring a metal precursor, a nitrogen-containing compound and an organic solvent, adding MCM-41 molecular sieve, and continuing ultrasonication, refluxing, vacuum drying, and drying to obtain a catalyst precursor;

[0020] (2) pyrolyzing the catalyst precursor obtained in step (1) in a nitrogen atmosphere to obtain a pyrolyzed catalyst precursor;

[0021] (3) Reducing the pyrolyzed catalyst precursor under a hydrogen atmosphere to obtain the bimetallic nitrogen-doped catalyst.

[0022] As a specific implementation method, the bimetallic nitrogen-doped catalyst is prepared by the following method:

[0023] The metal precursor, the nitrogen-containing compound and the organic solvent are mixed and stirred at room temperature, and after adding the MCM-41 molecular sieve, the solvent is removed by ultrasonication, reflux and vacuum drying, and after drying, the catalyst precursor is ground to obtain the catalyst precursor, and the catalyst precursor is placed in a nitrogen atmosphere for pyrolysis, cooled to room temperature, and reduced in a hydrogen atmosphere to obtain the catalyst.

[0024] Optionally, the stirring time is independently selected from any value among 10 min, 20 min, 30 min, 40 min, 50 min, 60 min or a range between any two of the above.

[0025] Optionally, the ultrasound time is independently selected from any value among 2 min, 5 min, 10 min, 15 min, 20 min, 25 min, 30 min or a range between any two of the above.

[0026] Optionally, the metal precursor includes a noble metal precursor and a non-noble metal precursor.

[0027] Optionally, the noble metal precursor is selected from at least one of chloroauric acid, silver nitrate, hexachloroplatinic acid, palladium chloride, rhodium nitrate, and ruthenium chloride.

[0028] Optionally, the non-precious metal precursor is selected from at least one of zinc chloride, ferric nitrate, cobalt acetate, nickel nitrate, manganese nitrate and copper acetate.

[0029] Optionally, the nitrogen-containing compound is selected from at least one of o-phenanthroline, 2,2-bipyridine, o-diaminobenzene, terpyridine, triethylenediamine, and pyrimidine.

[0030] Optionally, the organic solvent is selected from at least one of methanol, ethanol, acetonitrile, tetrahydrofuran and chloroform.

[0031] Optionally, the molar ratio of the nitrogen-containing compound to the metal precursor is 1.5 to 5.0:1.

[0032] The molar amount of the metal precursor is calculated based on the molar amount of the metal element, and the nitrogen-containing compound is calculated based on the molar amount of the nitrogen-containing compound itself.

[0033] Optionally, the molar ratio of the nitrogen-containing compound to the metal precursor is independently selected from any value of 1.5:1, 2.0:1, 2.5:1, 3.0:1, 4.0:1, 5.0:1 or a range between any two of the above values.

[0034] Optionally, the reaction temperature is 45 to 90° C., and the reaction time is 2 to 12 hours.

[0035] Optionally, the reaction temperature is 50-80° C., and the reaction time is 3-6 hours.

[0036] Optionally, the reaction time is 3 to 5 hours.

[0037] Optionally, the reaction temperature is independently selected from any value of 45°C, 50°C, 60°C, 70°C, 80°C, 90°C or a range between any two of the above values.

[0038] Optionally, the reaction time is independently selected from any value among 2h, 3h, 5h, 6h, 8h, 10h, 12h or a range between any two of the above.

[0039] Optionally, the vacuum drying temperature is 20-45°C.

[0040] Optionally, the vacuum drying temperature is independently selected from any value of 20°C, 25°C, 30°C, 35°C, 40°C, 45°C or a range between any two of the above values.

[0041] Optionally, the drying temperature is 70 to 90° C., and the drying time is 8 to 24 hours.

[0042] Optionally, the drying temperature is independently selected from any value of 70°C, 75°C, 80°C, 85°C, 90°C or a range between any two of the above values.

[0043] Optionally, the drying time is independently selected from any value among 8h, 10h, 12h, 15h, 18h, 20h, 24h or a range between any two of the above.

[0044] Optionally, the pyrolysis temperature is 500-1000° C., and the pyrolysis time is 1-5 hours.

[0045] Optionally, the pyrolysis temperature is independently selected from any value of 500°C, 600°C, 700°C, 800°C, 850°C, 900°C, 1000°C or a range between any two of the above values.

[0046] Optionally, the pyrolysis time is independently selected from any value among 1h, 2h, 3h, 4h, 5h or a range between any two of the above.

[0047] Optionally, the reduction temperature is 150-600° C., and the reduction time is 1-6 hours.

[0048] Optionally, the reduction temperature is independently selected from any value of 150°C, 200°C, 250°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C or a range between any two of the above values.

[0049] Optionally, the reduction time is independently selected from any value of 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, or a range between any two of the above values.

[0050] According to another aspect of the present application, a method for preparing glycine from glycolic acid is provided, the method comprising:

[0051] Passing hydrogen into a mixture containing glycolic acid, a catalyst and aqueous ammonia to perform a reductive amination reaction to obtain glycine;

[0052] The catalyst is selected from the bimetallic nitrogen-doped catalyst described above.

[0053] Optionally, the molar amount of the catalyst is 0.1 to 20.0% of the molar amount of the glycolic acid.

[0054] Optionally, the molar amount of the catalyst is any value independently selected from 0.1%, 0.3%, 0.5%, 0.7%, 1.0%, 5.0%, 8.0%, 10.0%, 15.0%, 18.0%, 20.0% of the molar amount of the glycolic acid, or a range between any two of the above values.

[0055] Wherein, the molar amount of the catalyst is calculated based on the molar amount of the precious metal element.

[0056] Optionally, the hydrogen partial pressure is 0.5-4.0 MPa.

[0057] Optionally, the hydrogen partial pressure is independently selected from any value among 0.5 MPa, 1.0 MPa, 1.5 MPa, 2.0 MPa, 2.5 MPa, 3.0 MPa, 3.5 MPa, 4.0 MPa or a range between any two of the above values.

[0058] Optionally, the hydrogen partial pressure is 1.0 to 2.0 MPa.

[0059] Optionally, the temperature of the reductive amination reaction is 160 to 240° C.; the time of the reductive amination reaction is 2 to 24 hours.

[0060] Optionally, the temperature of the reductive amination reaction is independently selected from any value of 160°C, 180°C, 200°C, 210°C, 220°C, 240°C or a range between any two of the above values.

[0061] Optionally, the time of the reductive amination reaction is independently selected from any value among 2h, 4h, 6h, 10h, 12h, 18h, 20h, 24h or a range between any two of the above.

[0062] Optionally, the temperature of the reductive amination reaction is 180-220° C.; the time of the reductive amination reaction is 6-12 h.

[0063] As a specific implementation method, glycolic acid, a catalyst and ammonia water are added into a reaction kettle, mixed, and heated to 160-240° C., with a hydrogen partial pressure of 0.5-4.0 MPa, and a reaction time of 2-24 hours, and glycolic acid is reductively aminated to glycine.

[0064] In a specific embodiment, the present invention provides a method for preparing a bimetallic nitrogen-doped catalyst and its application in the efficient preparation of glycine from glycolic acid. The method comprises mixing a metal precursor, a nitrogen-containing compound and an organic solvent, stirring at room temperature, adding MCM-41 molecular sieve, ultrasonicating, refluxing, and vacuum drying to remove the solvent, and after drying, grinding to obtain a catalyst precursor, placing the catalyst precursor in a nitrogen atmosphere for pyrolysis, cooling to room temperature, and reducing it in a hydrogen atmosphere to obtain the catalyst. The active bimetallic particles of the catalyst used in the method are small and stable, and interact with nitrogen-containing substances and carriers to achieve the preparation of glycine by reductive amination of glycolic acid. The catalyst is easy to separate and has excellent cyclic stability. The method and catalyst have broad application potential, bringing broad prospects to various fields in the future.

[0065] The catalyst can further reduce and aminize the hydroxyl group of glycolic acid to prepare glycine. The catalyst has the characteristics of simple preparation, easy separation from the reaction system and maintaining high catalytic activity after multiple recycling uses.

[0066] The beneficial effects of this application include:

[0067] 1) The method for preparing glycine by reductive amination of glycolic acid provided in the present application can achieve high selectivity for glycine due to the interaction between the bimetal in the catalyst and the doped nitrogen and the MCM-41 molecular sieve.

[0068] 2) The catalyst system used in the method provided in the present application has good stability, can maintain high catalytic activity, has a high product yield, has a simple and easy preparation process, is easy to separate from the system, and saves resources.

[0069] 3) After the catalyst provided in the present application is recycled for five times, it can still maintain good stability, and the yield of the product is maintained at more than 55%. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 This is the H NMR spectrum of the reaction solution in Example 1 of the present application.

[0071] Figure 2 This is the NMR carbon spectrum of the reaction solution in Example 1 of the present application. DETAILED DESCRIPTION

[0072] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0073] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0074] The calculation of conversion rate and yield in the examples of this application is as follows:

[0075] Glycolic acid conversion rate (C mol%) = (glycolic acid feed amount - glycolic acid detected after reaction) / glycolic acid feed amount × 100%

[0076] Glycine yield (C mol%) = glycine detected amount / glycolic acid feed amount × 100%.

[0077] Example 1

[0078] 3.0wt% of ruthenium chloride (calculated as ruthenium element) with a carrier mass, 8wt% of copper acetate (calculated as copper element) with a carrier mass, and a nitrogen-containing compound are mixed with 50mL of ethanol, wherein: the nitrogen-containing compound is o-phenanthroline, and the molar ratio of the nitrogen-containing compound to the metal precursor is 2.0:1. The mixture is stirred at room temperature for 30min, 1g of the carrier MCM-41 molecular sieve is added, ultrasonicated for 10min, refluxed at 60°C for 5h, then vacuum dried at 35°C to remove the solvent, dried at 80°C for 18h, and the obtained catalyst precursor is ground. The catalyst precursor is placed in a nitrogen atmosphere, pyrolyzed at 700°C for 2h, cooled to room temperature, and reduced at 250°C for 2h in a hydrogen atmosphere to obtain a catalyst.

[0079] Application Example 1

[0080] Application of bimetallic nitrogen-doped MCM-41 molecular sieve catalyst in the reductive amination of glycolic acid to prepare glycine:

[0081] Add glycolic acid, the catalyst prepared in Example 1, and ammonia water (25wt%) into a reaction kettle, and close the kettle. The amount of glycolic acid is 0.5mmol, the molar amount of ruthenium in the catalyst is 1.0% of the molar amount of glycolic acid, and the amount of ammonia water is 2.5mL. Replace the air in the kettle with hydrogen for 3 times, fill with 1.0MPa hydrogen, raise the temperature to 180°C, and react at this temperature for 12h. After the reaction is completed, the reaction mixture is naturally cooled to room temperature, and the catalyst is filtered to remove the catalyst. The reaction solution is evaporated to remove the solvent ammonia water, and internal standard trioxane and deuterated water are added and mixed evenly. Samples are taken and subjected to nuclear magnetic quantitative analysis, such as Figure 1 As shown, 1 H NMR (400 MHz, D2O, 298K): δ = 3.57 (s, 1H). The methylene of glycine peaks at 3.57 ppm, trioxane as an internal standard peaks at 5.23 ppm, and water peaks at 4.79 ppm; Figure 2 As shown, 13 C NMR (100 MHz, D2O, 298K): δ = 172.40 (s), 93.46 (s), 41.41 (s). The carboxyl and methylene groups of glycine peak at 172.40 ppm and 41.41 ppm, and trioxane as an internal standard peaks at 93.46 ppm; the results of NMR analysis are the yields of the corresponding products. The conversion rate of glycolic acid is 99%, and the yield of glycine is 65%.

[0082] Example 2

[0083] 0.5 wt% of palladium chloride (calculated as palladium element) of the carrier mass, 6 wt% of nickel nitrate (calculated as nickel element) of the carrier mass, a nitrogen-containing compound and 50 mL of acetonitrile, wherein: the nitrogen-containing compound is 2,2-bipyridine, and the molar ratio of the nitrogen-containing compound to the metal precursor is 1.5:1, stirred at room temperature for 60 minutes, 1 g of the carrier MCM-41 molecular sieve was added, ultrasonicated for 2 minutes, refluxed at 80°C for 3 hours, then vacuum dried at 45°C to remove the solvent, dried at 70°C for 10 hours, ground the obtained catalyst precursor, placed the catalyst precursor in a nitrogen atmosphere, pyrolyzed at 900°C for 3 hours, cooled to room temperature, and reduced at 150°C for 4 hours in a hydrogen atmosphere to obtain a catalyst.

[0084] Application Example 2

[0085] Application of bimetallic nitrogen-doped MCM-41 molecular sieve catalyst in the reductive amination of glycolic acid to prepare glycine:

[0086] Add glycolic acid, the catalyst prepared in Example 2, and ammonia water (25wt%) into a reactor, and close the reactor. The amount of glycolic acid is 0.5mmol, the molar amount of palladium in the catalyst is 0.1% of the molar amount of glycolic acid, and the amount of ammonia water is 2.5mL; replace the air in the reactor with hydrogen for 3 times, fill with 2.0MPa hydrogen, heat to 220℃, and react at this temperature for 6h. After the reaction is completed, the reaction mixture is naturally cooled to room temperature and the catalyst is filtered to remove the solvent ammonia water. The reaction solution is evaporated to remove the solvent ammonia water, and internal standard trioxane and deuterated water are added and mixed evenly, and samples are taken and subjected to nuclear magnetic quantitative analysis; the result of nuclear magnetic analysis is the yield of the corresponding product. The conversion rate of glycolic acid is 99%, and the yield of glycine is 64%.

[0087] Example 3

[0088] 8.0 wt% of silver nitrate (calculated as silver element) of the carrier, 5 wt% of cobalt acetate (calculated as cobalt element) of the carrier, and a nitrogen-containing compound are mixed with 50 mL of methanol, wherein: the nitrogen-containing compound is o-diaminobenzene, and the molar ratio of the nitrogen-containing compound to the metal precursor is 5.0:1. The mixture is stirred at room temperature for 10 min, 1 g of the carrier MCM-41 molecular sieve is added, ultrasonicated for 30 min, refluxed at 50° C. for 6 h, then vacuum dried at 20° C. to remove the solvent, dried at 75° C. for 12 h, and the obtained catalyst precursor is ground. The catalyst precursor is placed in a nitrogen atmosphere, pyrolyzed at 850° C. for 1 h, cooled to room temperature, and reduced at 400° C. for 3 h in a hydrogen atmosphere to obtain a catalyst.

[0089] Application Example 3

[0090] Application of bimetallic nitrogen-doped MCM-41 molecular sieve catalyst in the reductive amination of glycolic acid to prepare glycine:

[0091] Add glycolic acid, the catalyst prepared in Example 3, and ammonia water (25wt%) into a reactor, and close the reactor. The amount of glycolic acid is 0.5mmol, the molar amount of silver in the catalyst is 10.0% of the molar amount of glycolic acid, and the amount of ammonia water is 2.5mL; replace the air in the reactor with hydrogen for 3 times, fill with 1.5MPa hydrogen, heat to 200℃, and react at this temperature for 10h. After the reaction is completed, the reaction mixture is naturally cooled to room temperature and the catalyst is filtered to remove the solvent ammonia water. The reaction solution is evaporated to remove the solvent ammonia water, and internal standard trioxane and deuterated water are added and mixed evenly, and samples are taken and subjected to nuclear magnetic quantitative analysis; the result of nuclear magnetic analysis is the yield of the corresponding product. The conversion rate of glycolic acid is 99%, and the yield of glycine is 63%.

[0092] Example 4

[0093] Rhodium nitrate (calculated as rhodium element) with a carrier mass of 0.2wt%, ferric nitrate (calculated as iron element) with a carrier mass of 25wt%, a nitrogen-containing compound and 50mL of chloroform, wherein: the nitrogen-containing compound is terpyridine, and the molar ratio of the nitrogen-containing compound to the metal precursor is 3.0:1, and the mixture is stirred at room temperature for 20min, 1g of the carrier MCM-41 molecular sieve is added, ultrasonicated for 15min, refluxed at 45°C for 12h, then vacuum dried at 30°C to remove the solvent, dried at 90°C for 8h, and the obtained catalyst precursor is ground, and the catalyst precursor is placed in a nitrogen atmosphere, pyrolyzed at 500°C for 5h, cooled to room temperature, and reduced at 200°C for 6h in a hydrogen atmosphere to obtain a catalyst.

[0094] Application Example 4

[0095] Application of bimetallic nitrogen-doped MCM-41 molecular sieve catalyst in the reductive amination of glycolic acid to prepare glycine:

[0096] Add glycolic acid, the catalyst prepared in Example 4, and ammonia water (25wt%) into a reactor, and close the reactor. The amount of glycolic acid is 0.5mmol, the molar amount of rhodium in the catalyst is 20.0% of the molar amount of glycolic acid, and the amount of ammonia water is 2.5mL; replace the air in the reactor with hydrogen for 3 times, fill with 4.0MPa hydrogen, heat to 160℃, and react at this temperature for 24h. After the reaction is completed, the reaction mixture is naturally cooled to room temperature and the catalyst is filtered to remove the solvent ammonia water. The reaction solution is evaporated to remove the solvent ammonia water, and the internal standard trioxane and deuterated water are added and mixed evenly, and the sample is taken and subjected to nuclear magnetic quantitative analysis; the result of nuclear magnetic analysis is the yield of the corresponding product. The conversion rate of glycolic acid is 99%, and the yield of glycine is 60%.

[0097] Example 5

[0098] Hexachloroplatinic acid (calculated as platinum element) with a carrier mass of 5.0wt%, manganese nitrate (calculated as manganese element) with a carrier mass of 10wt%, a nitrogen-containing compound and 50mL of tetrahydrofuran are mixed, wherein: the nitrogen-containing compound is triethylenediamine, and the molar ratio of the nitrogen-containing compound to the metal precursor is 4.0:1, and the mixture is stirred at room temperature for 40min, 1g of the carrier MCM-41 molecular sieve is added, ultrasonicated for 5min, refluxed at 90°C for 2h, then vacuum dried at 40°C to remove the solvent, dried at 70°C for 24h, and the obtained catalyst precursor is ground, and the catalyst precursor is placed in a nitrogen atmosphere, pyrolyzed at 1000°C for 1h, cooled to room temperature, and reduced at 600°C for 1h in a hydrogen atmosphere to obtain a catalyst.

[0099] Application Example 5

[0100] Application of bimetallic nitrogen-doped MCM-41 molecular sieve catalyst in the reductive amination of glycolic acid to prepare glycine:

[0101] Add glycolic acid, the catalyst prepared in Example 5, and ammonia water (25wt%) into a reactor, and close the reactor. The amount of glycolic acid is 0.5mmol, the molar amount of platinum in the catalyst is 0.7% of the molar amount of glycolic acid, and the amount of ammonia water is 2.5mL; replace the air in the reactor with hydrogen for 3 times, fill with 0.5MPa hydrogen, heat to 240℃, and react at this temperature for 2h. After the reaction is completed, the reaction mixture is naturally cooled to room temperature and the catalyst is filtered to remove the solvent ammonia water. The reaction solution is evaporated to remove the solvent ammonia water, and internal standard trioxane and deuterated water are added and mixed evenly, and samples are taken and subjected to nuclear magnetic quantitative analysis; the result of nuclear magnetic analysis is the yield of the corresponding product. The conversion rate of glycolic acid is 99%, and the yield of glycine is 61%.

[0102] Example 6

[0103] 1.0 wt% of chloroauric acid (in terms of gold element) with a carrier mass, 15 wt% of zinc chloride (in terms of zinc element) with a carrier mass, a nitrogen-containing compound and 50 mL of ethanol are mixed, wherein: the nitrogen-containing compound is pyrimidine, and the molar ratio of the nitrogen-containing compound to the metal precursor is 2.5:1, and the mixture is stirred at room temperature for 50 min, 1 g of the carrier MCM-41 molecular sieve is added, ultrasonicated for 20 min, refluxed at 70°C for 10 h, then vacuum dried at 25°C to remove the solvent, dried at 85°C for 15 h, and the obtained catalyst precursor is ground, and the catalyst precursor is placed in a nitrogen atmosphere, pyrolyzed at 800°C for 4 h, cooled to room temperature, and reduced at 350°C for 5 h in a hydrogen atmosphere to obtain a catalyst.

[0104] Application Example 6

[0105] Application of bimetallic nitrogen-doped MCM-41 molecular sieve catalyst in the reductive amination of glycolic acid to prepare glycine:

[0106] Add glycolic acid, the catalyst prepared in Example 6, and ammonia water (25wt%) into a reactor, and close the reactor. The amount of glycolic acid is 0.5mmol, the molar amount of gold in the catalyst is 5.0% of the molar amount of glycolic acid, and the amount of ammonia water is 2.5mL; replace the air in the reactor with hydrogen for 3 times, fill with 3.0MPa hydrogen, heat to 210℃, and react at this temperature for 18h. After the reaction is completed, the reaction mixture is naturally cooled to room temperature and the catalyst is filtered to remove the solvent ammonia water. The reaction solution is evaporated to remove the solvent ammonia water, and internal standard trioxane and deuterated water are added and mixed evenly, and samples are taken and subjected to nuclear magnetic quantitative analysis; the result of nuclear magnetic analysis is the yield of the corresponding product. The conversion rate of glycolic acid is 99%, and the yield of glycine is 60%.

[0107] Application Example 7

[0108] After the catalyst was prepared and reduced according to the conditions of Example 1, it was used in the glycolic acid reduction amination reaction according to the conditions of Application Example 1. The difference from Application Example 1 was that after the reaction, the catalyst was centrifuged and washed with water for 5 times by centrifugation, and the glycolic acid reduction amination reaction was repeated again. The catalyst was recycled for 5 times. The results are shown in Table 1.

[0109] Table 1. Effect of catalyst on the recycling of glycolic acid reduction amination

[0110] Cycle times Glycolic acid conversion rate (C%) Yield of glycine (C%) 1 99 65 2 99 64 3 99 64 4 99 63 5 99 61

[0111] As can be seen from Table 1, the prepared catalyst can still maintain a high catalytic activity for the reductive amination of glycolic acid after being recycled for five times, and the yield of glycine is maintained at more than 61%. The catalysts provided in Examples 2 to 6 can also maintain a high catalytic activity when recycled under the same conditions, and the yield of glycine is maintained at more than 55% after being recycled for five times.

[0112] Comparative Example 1

[0113] The catalyst was prepared according to the conditions of Example 1 and then reduced for use in the reduction amination reaction of glycolic acid. The difference from Example 1 is that during the catalyst preparation process, the metal precursor was mixed with an organic solvent, stirred at room temperature, and then the MCM-41 molecular sieve-loaded bimetallic catalyst was obtained through subsequent operations. The conversion rate of glycolic acid was 99%, and the yield of glycine was 25%.

[0114] Comparative Example 2

[0115] The catalyst was prepared according to the conditions of Example 1, and the catalyst was reduced and then used for the reductive amination reaction of glycolic acid. The difference from Example 1 is that during the catalyst preparation process, the noble metal precursor, the nitrogen-containing compound and the organic solvent are mixed, stirred at room temperature, and then the MCM-41 molecular sieve-loaded noble metal-doped catalyst is obtained through subsequent operations. The conversion rate of glycolic acid is 99%, and the yield of glycine is 40%.

[0116] Comparative Example 3

[0117] The catalyst was prepared according to the conditions of Example 1, and the catalyst was reduced and then used for the reductive amination reaction of glycolic acid. The difference from Example 1 is that during the catalyst preparation process, the non-precious metal precursor, the nitrogen-containing compound and the organic solvent are mixed, stirred at room temperature, and then the MCM-41 molecular sieve-loaded non-precious metal-doped catalyst is obtained through subsequent operations. The conversion rate of glycolic acid is 99%, and the yield of glycine is 35%.

[0118] The bimetallic catalyst used in the preparation method of the present invention has a small and stable particle size, interacts with nitrogen-containing substances and carriers, can realize the reductive amination of glycolic acid to prepare glycine, the catalyst is easy to separate, and has excellent cyclic stability. The method and catalyst have wide application potential and bring broad prospects to various fields in the future.

[0119] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A bimetallic nitrogen-doped catalyst, It is characterized in that The bimetallic nitrogen-doped catalyst comprises a carrier and a bimetallic component supported on the carrier; The carrier is nitrogen-doped MCM-41 molecular sieve; The bimetallic component includes a noble metal element and a non-noble metal element.

2. The bimetallic nitrogen-doped catalyst according to claim 1, It is characterized in that The noble metal element is selected from at least one of Au, Ag, Pd, Pt, Rh and Ru; Preferably, the non-precious metal element is selected from at least one of Zn, Fe, Co, Ni, Mn and Cu; Preferably, in the bimetallic nitrogen-doped catalyst, the loading amount of the noble metal element is 0.2-8.0 wt.%, and the loading amount of the non-noble metal element is 5-25 wt.%. Wherein, the mass of the bimetallic nitrogen-doped catalyst is calculated based on the mass of the carrier, the mass of the noble metal element is calculated based on the mass of the noble metal element, and the mass of the non-noble metal element is calculated based on the mass of the non-noble metal element; Preferably, in the bimetallic nitrogen-doped catalyst, the loading amount of the noble metal element is 0.5-3.0 wt.%, and the loading amount of the non-noble metal element is 6-8 wt.%.

3. A method for preparing the bimetallic nitrogen-doped catalyst according to any one of claims 1 to 2, It is characterized in that The preparation method comprises: The mixture containing a metal precursor, a nitrogen-containing compound, an organic solvent and a carrier is reacted, vacuum dried, dried, pyrolyzed and reduced to obtain the bimetallic nitrogen-doped catalyst.

4. The preparation method according to claim 3, It is characterized in that The metal precursor includes a noble metal precursor and a non-noble metal precursor; Preferably, the noble metal precursor is selected from at least one of chloroauric acid, silver nitrate, hexachloroplatinic acid, palladium chloride, rhodium nitrate, and ruthenium chloride; Preferably, the non-precious metal precursor is selected from at least one of zinc chloride, ferric nitrate, cobalt acetate, nickel nitrate, manganese nitrate, and copper acetate; Preferably, the nitrogen-containing compound is selected from at least one of o-phenanthroline, 2,2-bipyridine, o-diaminobenzene, terpyridine, triethylenediamine, and pyrimidine; Preferably, the organic solvent is selected from at least one of methanol, ethanol, acetonitrile, tetrahydrofuran and chloroform.

5. The preparation method according to claim 3, It is characterized in that The molar ratio of the nitrogen-containing compound to the metal precursor is 1.5 to 5.0:

1. The molar amount of the metal precursor is calculated based on the molar amount of the metal element, and the nitrogen-containing compound is calculated based on the molar amount of the nitrogen-containing compound itself.

6. The preparation method according to claim 3, It is characterized in that The reaction temperature is 45 to 90° C. and the reaction time is 2 to 12 hours; Preferably, the vacuum drying temperature is 20-45°C; Preferably, the drying temperature is 70 to 90° C., and the drying time is 8 to 24 hours.

7. The preparation method according to claim 3, It is characterized in that The pyrolysis temperature is 500-1000°C and the pyrolysis time is 1-5h; Preferably, the reduction temperature is 150-600° C., and the reduction time is 1-6 hours.

8. A method for preparing glycine from glycolic acid, It is characterized in that The method comprises: Passing hydrogen into a mixture containing glycolic acid, a catalyst and aqueous ammonia to perform a reductive amination reaction to obtain glycine; The catalyst is selected from the bimetallic nitrogen-doped catalyst according to any one of claims 1 to 2.

9. The method according to claim 8, It is characterized in that The molar amount of the catalyst is 0.1 to 20.0% of the molar amount of the glycolic acid. Wherein, the molar amount of the catalyst is calculated based on the molar amount of the precious metal element.

10. The method according to claim 8, It is characterized in that The hydrogen partial pressure is 0.5-4.0 MPa; Preferably, the hydrogen partial pressure is 1.0 to 2.0 MPa; Preferably, the temperature of the reductive amination reaction is 160 to 240° C.; the time of the reductive amination reaction is 2 to 24 hours; Preferably, the temperature of the reductive amination reaction is 180-220° C.; and the time of the reductive amination reaction is 6-12 h.

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