Carbon-nitrogen materials, methods of making and using the same, and supported catalysts and uses thereof

Abstract

The application provides a biomass-based carbon-nitrogen material, a preparation method and application thereof, and a supported catalyst and application thereof, wherein the carbon-nitrogen material contains carbon elements, nitrogen elements and oxygen elements, has a specific surface area of 300 m 2 / g or below, and a pore volume of 0.4 cm 3 / g or below. The carbon-nitrogen material prepared by the method has the characteristics of adjustable specific surface area and pore volume, high nitrogen content, and the like, and the sample obtained by the application has special microscopic morphology and compact structure. The carbon-nitrogen material prepared by the method is used as a carrier to load a metal active component, and after activation, a supported metal catalyst can be prepared, which can be used for catalyzing selective hydrogenation of unsaturated functional groups, and especially, after loading of palladium, a better technical effect is achieved in the hydrogenation refining reaction of crude terephthalic acid.

Description

Technical Field

[0001] This invention belongs to the field of novel carbon material preparation technology, specifically relating to biomass-based carbon and nitrogen materials, their preparation methods and applications, as well as a supported catalyst and its applications. Background Technology

[0002] Biomass-based raw materials (cellulose, starch, glucose, fructose, sucrose, or rice husks, bamboo, etc.) are green and renewable resources, widely available in nature, inexpensive and readily available, making them ideal carbon sources for synthesizing carbon materials. Carbon materials synthesized from biomass-based raw materials can be used directly as catalysts or as supports for supported metal catalysts, exhibiting excellent catalytic performance. Currently, they show promising application prospects in catalytic hydrogenation, energy storage, lithium-ion batteries, and water treatment.

[0003] Methods for preparing carbon materials using biomass as a carbon source mainly include direct carbonization, hydrothermal carbonization, and template methods. To obtain carbon materials with porous structures and high strength, the main drawbacks of traditional preparation processes are high energy consumption and cumbersome procedures. Using template methods to prepare porous carbon materials not only increases production costs, but the removal of the template also leads to damage to the pore structure and surface functional groups. In recent years, with the emergence of various new material preparation methods, researchers have begun to explore a wide variety of raw materials and new technologies for synthesizing different types of carbon materials.

[0004] CN106783209B prepared a porous carbon material using glucose, thiourea, and sodium dodecyl sulfate as raw materials through hydrothermal and KOH activation methods. This material has a hollow structure composed of polymer microspheres and can be used as an electrode material in the field of supercapacitors.

[0005] CN108262077A reports a high-strength nitrogen-doped carbon monolithic catalytic material with hierarchical pores. Using nitrogen-containing organic matter and sugars as precursors, a nitrogen-doped carbon material with a hierarchical pore structure that has both micropores and mesopores was prepared through pre-carbonization and carbonization processes. It can be used in the fields of acetylene process to produce vinyl chloride and electrocatalysis. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing carbon material preparation technologies by providing a novel carbon-based material with a new structure and its preparation method. The carbon-nitrogen material of this invention has adjustable specific surface area and pore volume, high nitrogen content, and dense microstructure, which has significant value in industrial applications across various fields.

[0007] According to a first aspect of the present invention, the present invention provides a biomass-based carbon-nitrogen material, said carbon-nitrogen material containing carbon, nitrogen and oxygen elements, and having a specific surface area of ​​300 m². 2 / g or less, pore volume is 0.4cm³3 / g below.

[0008] According to a second aspect of the present application, the present application provides a method for preparing the biomass-based carbon-nitrogen material according to the present application, which comprises:

[0009] (1) forming an aqueous solution of a carbon source, a nitrogen source and an alkali metal salt, and performing a hydrothermal reaction under a sealed condition, and then obtaining a solid sample after cooling, washing and drying;

[0010] (2) calcining the solid sample in an oxygen-containing atmosphere.

[0011] According to a third aspect of the present application, the present application provides an application of the carbon-nitrogen material according to the present application as a catalyst carrier.

[0012] According to a fourth aspect of the present application, the present application provides a supported catalyst, wherein the carrier of the supported catalyst contains the carbon-nitrogen material according to the present application, preferably the active component of the supported catalyst is a metal active component, and more preferably the active component is palladium.

[0013] According to a fifth aspect of the present application, the present application provides an application of the carbon-nitrogen material according to the present application or the catalyst according to the present application in a selective hydrogenation reaction of an unsaturated functional group, preferably in a crude terephthalic acid hydrogenation refining reaction.

[0014] The carbon-nitrogen material prepared by the method of the present application has the characteristics of adjustable specific surface area and pore volume, high nitrogen content, etc. The method of the present application is different from the carbon spheres and other structures prepared by the previous hydrothermal method, and the obtained sample has a special micro-morphology and a dense structure.

[0015] The carbon-nitrogen material prepared by the method of the present application is used as a carrier to load a metal active component, and a supported metal catalyst can be prepared after activation, which can be used for catalyzing a selective hydrogenation reaction of an unsaturated functional group, especially after loading palladium, a good technical effect is achieved in a crude terephthalic acid hydrogenation refining reaction.

[0016] Compared with the prior art, the present application has the following beneficial effects:

[0017] (1) The process of the present application is simple, and the specific surface area, pore volume and nitrogen content of the obtained carbon-nitrogen material are controllable, which can be realized by controlling the ratio of the carbon source, the nitrogen source and the preparation conditions;

[0018] (2) The carbon source involved in the present application can be obtained from renewable resources, which is widely available and low in price, and is conducive to the popularization and application of planning.

[0019] (3) The carbon-nitrogen material prepared by the present application has a dense structure, and the nitrogen doping amount can be accurately controlled according to specific needs.

[0020] (4) The carbon-nitrogen material obtained by the method has excellent catalytic carrier performance, and can be widely used in the preparation of metal catalysts.

[0021] Specifically, the palladium catalyst prepared by using the carbon-nitrogen carrier obtained by the method has higher activity and stability than the traditional coconut shell carbon supported palladium catalyst, and has the advantage of high selectivity to generate intermediate product 4-hydroxymethyl benzoic acid, which is beneficial to reduce the energy consumption of subsequent product separation and purification. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a scanning electron microscope image of the sample prepared in Example 5;

[0023] Figure 2 is a scanning electron microscope image of the sample prepared in Example 5 at a magnification of 1000 times;

[0024] Figure 3 is a scanning electron microscope image of the sample prepared in Comparative Example 1;

[0025] Figure 4 is a scanning electron microscope image of the sample prepared in Comparative Example 5. DETAILED DESCRIPTION

[0026] The endpoints of the ranges and any values claimed herein are not to be understood as being limited to the exact values recited as the exact dimensions are not to be understood as being measured with infinite precision, and are intended in a meaningful numerical limit sense only. For numeric ranges, the endpoints of each range, the endpoints of each range and individual point values, and individual point values can be combined with each other to generate one or more new numeric ranges, which are to be considered as being specifically disclosed herein.

[0027] The present application provides a biomass-based carbon-nitrogen material, which contains carbon element, nitrogen element and oxygen element, has a specific surface area of 300 m 2 / g or less, and a pore volume of 0.4 cm 3 / g or less. The method of the present application has the characteristics of adjustable specific surface area and pore volume, and high nitrogen content. The method of the present application is different from the conventional hydrothermal method for preparing carbon spheres and other structures, and the obtained sample has a special micro-morphology and a dense structure.

[0028] According to the present application, the micro-morphology of the carbon-nitrogen material is preferably a dense structure with a block shape. The dense structure has the advantage of better dispersion and stable active metal nanoparticles compared with the loose structure of conventional nanometer carbon spheres. The material of the present application has a dense structure, and is not composed of conventional nanometer carbon spheres, has a specific surface area of 5 m 2 / g or more, preferably 60-280 m 2 / g, and the pore volume is preferably 0.01-0.40 cm 3 / g. The specific surface area and pore volume of the carbon-nitrogen material can be precisely controlled by reaction parameters.

[0029] According to the present application, the content of nitrogen element is preferably 6-15 at.%, and the rest is carbon element and oxygen element, based on the total weight of the carbon-nitrogen material.

[0030] According to the present application, the content of nitrogen element is preferably 7.5-12.5 at.%, the content of carbon element is 80-95 at.%, and the content of oxygen element is 5-10 at.%, based on the total weight of the carbon-nitrogen material.

[0031] The carbon-nitrogen material having the aforementioned features of the present application can achieve the purpose of the present application, and there is no special requirement for the preparation method thereof. For the present application, a preparation method of the biomass-based carbon-nitrogen material is provided, which comprises:

[0032] (1) forming an aqueous solution of a carbon source, a nitrogen source and an alkali metal salt, and performing a hydrothermal reaction under sealed conditions, and then obtaining a solid sample after cooling, washing and drying;

[0033] (2) calcining the solid sample in an oxygen-containing atmosphere. By using the method of the present application, the carbon-nitrogen material having the features of the present application can be prepared.

[0034] According to the present application, the optional range of the hydrothermal reaction conditions is relatively wide. For the present application, the hydrothermal reaction conditions in step (1) preferably include a temperature of 140-200°C, preferably 160-180°C.

[0035] According to the present application, the time of the hydrothermal reaction can be determined according to the temperature. Specifically, the time of the hydrothermal reaction is preferably 2-10 h, preferably 4-7 h.

[0036] According to the present application, the optional range of the amount of each substance is relatively wide. For the present application, the mass ratio of the carbon source, the nitrogen source and the alkali metal salt is preferably 5-20:1-6:1, preferably 10-15:1-6:1.

[0037] According to the present application, the optional range of the concentration of the carbon source in the aqueous solution is relatively wide. For the present application, the concentration of the carbon source in the aqueous solution in step (1) is preferably 8-12 wt.%.

[0038] According to the present application, the optional range of the calcination conditions is relatively wide. For the present application, the calcination conditions in step (2) preferably include a temperature of 450-950°C, preferably 650-800°C.

[0039] According to the present application, the time of the calcination is determined according to the temperature, and preferably for the present application, the calcination conditions in step (2) include: the time is 0.5-3h, preferably 1-2h.

[0040] According to a preferred embodiment of the present application, preferably the calcination conditions include: using step-by-step calcination in an oxygen-containing atmosphere, first pre-treating at a low temperature of 200-300℃ for 0.5-1h, and then calcining at a temperature of 450-950℃ for 0.5-3h.

[0041] According to a preferred embodiment of the present application, the calcination is carried out in a tube furnace.

[0042] According to a preferred embodiment of the present application, the oxygen concentration in the oxygen-containing atmosphere is 15-25vol%.

[0043] According to the present application, the oxygen-containing atmosphere is, for example, air, nitrogen or argon mixed with oxygen, etc. Preferably, the atmosphere is air.

[0044] In the present application, the types of carbon sources can be selected in a wide range, and preferably for the present application, the carbon source can be various biomass carbon sources, specifically, the carbon source is one or more of glucose, fructose, xylose, sucrose, chitosan and cellulose; and preferably for the present application, the carbon source is glucose and / or fructose.

[0045] In the present application, the types of nitrogen sources can be selected in a wide range, and preferably for the present application, the nitrogen source is urea and / or melamine, more preferably urea.

[0046] In the present application, the types of alkali metal salts can be selected in a wide range, and preferably for the present application, the alkali metal salt is one or more of potassium sulfate, sodium sulfate, sodium carbonate, potassium carbonate, sodium chloride and potassium chloride, more preferably one or more of potassium sulfate, sodium sulfate, sodium carbonate and potassium carbonate, and more preferably sodium sulfate.

[0047] According to a preferred embodiment of the present application, the method of the present application includes:

[0048] (1) dissolving the carbon source, the nitrogen source and the alkali metal salt in water according to the ratio, and then transferring to a reaction kettle, and reacting at 140-200℃ for 2-10h, and after natural cooling, washing and drying to obtain a solid sample;

[0049] (2) placing the solid sample in a tube furnace, and calcining at 450-950℃ for 0.5-3h in an oxygen-containing atmosphere.

[0050] According to a preferred embodiment of the present application, the method of the present application comprises: dissolving carbon source, nitrogen source and potassium sulfate in water in a certain proportion, then transferring into a reaction kettle, reacting at 140-200℃ for 2-10h, after natural cooling, washing and drying to obtain a solid sample; calcining the solid sample in air atmosphere at 450-950℃ for 0.5-3h to obtain the biomass-based carbon-nitrogen material.

[0051] The method of the present application can be used to prepare the carbon-nitrogen material with the special properties of the present application. It is particularly suitable for use as a catalyst carrier.

[0052] The present application provides the use of the carbon-nitrogen material of the present application as a catalyst carrier.

[0053] The present application provides a supported catalyst, the carrier of which contains the carbon-nitrogen material of the present application, preferably the active component of the supported catalyst is a metal active component, the type of the metal active component can be selected in a wide range, and for the present application, the active component is preferably palladium.

[0054] The aforementioned supported catalyst of the present application is particularly suitable for use in the selective hydrogenation reaction of unsaturated functional groups, preferably in the hydrogenation purification reaction of crude terephthalic acid.

[0055] The supported catalyst of the present application can be used in the catalytic selective hydrogenation reaction of unsaturated functional groups. Preferably, the supported palladium active component can be used to prepare a palladium-carbon catalyst, which is preferably used in the catalytic hydrogenation purification reaction of crude terephthalic acid.

[0056] In order to more clearly illustrate the technical solutions of the present application, the following specific embodiments are listed.

[0057] The purpose of calcining and activating the solid sample is to etch the surface of carbon, burn off amorphous carbon, and reconstruct C-C and C-N bonds, while also forming some pore structures, finally forming a carbon-nitrogen material with stable structure. Therefore, there will be a mass loss after calcination compared with before calcination, which is defined as the yield. The yield of the sample refers to the percentage of the mass of the sample after calcination to the mass of the sample before calcination.

[0058] Example 1

[0059] Weigh 6.0g of glucose, 1.5g of urea and 0.5g of sodium sulfate, dissolve in 60.0g of water, transfer into a reaction kettle, react at 160℃ for 6h, after natural cooling, wash and dry to obtain a solid sample; place the obtained solid sample in a tube furnace and calcine at 650℃ in air atmosphere for 1h, and naturally cool to room temperature to obtain the biomass-based carbon-nitrogen material, with a yield of 41.1%.

[0060] Example 2

[0061] Take fructose 6.0 g, urea 1.5 g and sodium sulfate 0.5 g, dissolved in 60.0 g of water, transferred to the reaction kettle, reacted at 160℃ for 6h, after natural cooling, washed, dried to get solid sample; the obtained solid sample was placed in a tube furnace at 650℃ for 1h under air atmosphere, and then naturally cooled to room temperature to obtain biomass-based carbon-nitrogen material, with a yield of 42.3%.

[0062] Example 3

[0063] Take fructose 6.0 g, urea 1.5 g and sodium sulfate 0.5 g, dissolved in 60.0 g of water, transferred to the reaction kettle, reacted at 160℃ for 6h, after natural cooling, washed, dried to get solid sample; the obtained solid sample was placed in a tube furnace at 650℃ for 1h under air atmosphere, and then naturally cooled to room temperature to obtain biomass-based carbon-nitrogen material, with a yield of 42.3%.

[0064] Example 4

[0065] Take fructose 6.0 g, urea 1.5 g and sodium sulfate 0.5 g, dissolved in 60.0 g of water, transferred to the reaction kettle, reacted at 160℃ for 6h, after natural cooling, washed, dried to get solid sample; the obtained solid sample was placed in a tube furnace at 650℃ for 1h under air atmosphere, and then naturally cooled to room temperature to obtain biomass-based carbon-nitrogen material, with a yield of 42.3%.

[0066] Example 5

[0067] Take fructose 6.0 g, urea 1.5 g and sodium sulfate 0.5 g, dissolved in 60.0 g of water, transferred to the reaction kettle, reacted at 160℃ for 6h, after natural cooling, washed, dried to get solid sample; the obtained solid sample was placed in a tube furnace at 650℃ for 1h under air atmosphere, and then naturally cooled to room temperature to obtain biomass-based carbon-nitrogen material, with a yield of 42.3%. Figure 1 and Figure 2 as shown in the scanning electron microscope images of the sample. Figure 1 The synthesized carbon-nitrogen material is composed of dense block structure, and Figure 2 is Figure 1 Further magnification of the morphology can be observed that the surface of the synthesized carbon-nitrogen material is flat at the micro size, and no obvious macroporous structure is observed.

[0068] Example 6

[0069] Take glucose 6.0 g, urea 3.0 g and sodium sulfate 0.5 g, dissolved in 60.0 g of water, transferred to the reaction kettle, reacted at 180℃ for 6h, after natural cooling, washed, dried to get solid sample; the obtained solid sample was placed in a tube furnace at 750℃ for 1h under air atmosphere, and then naturally cooled to room temperature to obtain biomass-based carbon-nitrogen material, with a yield of 40.5%.

[0070] Example 7

[0071] Take glucose 6.0 g, urea 1.5 g and sodium sulfate 0.5 g, dissolved in 60.0 g of water, transferred to the reaction kettle, reacted at 180℃ for 6h, after natural cooling, washed, dried to get solid sample; the obtained solid sample was placed in a tube furnace at 850℃ for 1h under air atmosphere, and then naturally cooled to room temperature to obtain biomass-based carbon-nitrogen material, with a yield of 43.2%.

[0072] Example 8

[0073] Take glucose 6.0 g, melamine 0.5 g and sodium sulfate 0.5 g, dissolved in 60.0 g of water, transferred to the reaction kettle, reacted at 180℃ for 6h, after natural cooling, washed, dried to get solid sample; the obtained solid sample was placed in a tube furnace at 750℃ for 1h under air atmosphere, and then naturally cooled to room temperature to obtain biomass-based carbon-nitrogen material, with a yield of 43.7%.

[0074] Example 9

[0075] Take glucose 6.0 g, melamine 1.5 g and sodium sulfate 0.5 g, dissolved in 60.0 g of water, transferred to the reaction kettle, reacted at 180℃ for 6h, after natural cooling, washed, dried to get solid sample; the obtained solid sample was placed in a tube furnace at 750℃ for 1h under air atmosphere, and then naturally cooled to room temperature to obtain biomass-based carbon-nitrogen material, with a yield of 42.9%.

[0076] Example 10

[0077] According to the method of Example 5, except that the carbon source is changed to xylose, and the rest of the conditions are the same.

[0078] Example 11

[0079] According to the method of Example 5, except that the solution reaction conditions are changed to keep at 140℃ for 6h, and the rest of the conditions are the same.

[0080] Example 12

[0081] According to the method of Example 5, except that the type of metal salt is changed to sodium carbonate, and the rest of the conditions are the same. The yield of the obtained carbon-nitrogen material is 33.6%.

[0082] Example 13

[0083] The method of Example 5 was followed, except that the calcination was changed to a two-step calcination, first at 200°C for 0.5h, then at 750°C for 1h, with the same other conditions.

[0084] Example 14

[0085] The method of Example 5 was followed, except that the calcination was changed to a two-step calcination, first at 300°C for 0.5h, then at 750°C for 1h, with the same other conditions.

[0086] Example 15

[0087] The method of Example 5 was followed, except that the amount of carbon source was changed, with 4g of glucose added, with the same other conditions. The yield of the carbon-nitrogen material was 21.7%.

[0088] Example 16

[0089] The method of Example 5 was followed, except that the amount of carbon source was changed, with 9g of glucose added, with the same other conditions. The yield of the carbon-nitrogen material was 23.4%.

[0090] Comparative Example 1

[0091] Glucose 6.0g and sodium sulfate 0.5g were weighed out and dissolved in 60.0g of water, which was transferred to a reaction kettle and reacted at 180°C for 6h. After natural cooling, the sample was washed and dried to obtain a solid sample. The solid sample was placed in a tube furnace and calcined at 750°C for 1h in an air atmosphere, and naturally cooled to room temperature to obtain a biomass-based carbon-nitrogen material, with a yield of 17.3%. The scanning electron microscope image of the sample is shown in Figure 1. Figure 3 .

[0092] Comparative Example 2

[0093] Glucose 6.0g, urea 1.5g and sodium sulfate 0.5g were weighed out and dissolved in 60.0g of water, which was transferred to a reaction kettle and reacted at 180°C for 6h. After natural cooling, the sample was washed and dried to obtain a nitrogen-doped carbon sample. The sample was not subjected to subsequent calcination in an air atmosphere.

[0094] Comparative Example 3

[0095] Commercially available coconut shell activated carbon of 4-6 mesh was broken to obtain 20-40 mesh particles, and the obtained solid was used as a carrier for a palladium catalyst.

[0096] Comparative Example 4

[0097] Using urea as the nitrogen source, 6g of coconut shell char was mixed with 3g of urea and placed in a tube furnace. The mixture was then calcined at 750℃ for 1 hour under a nitrogen atmosphere to obtain nitrogen-doped coconut shell char. The scanning electron microscope image of the sample is shown below. Figure 4 .

[0098] Comparative Example 5 ( Figure 1 and Figure 2 ) and the sample of Comparative Example 1 ( Figure 3 The scanning electron microscope (SEM) images show that the addition of a nitrogen source significantly alters the morphology of the carbon material. The carbon-nitrogen material obtained without urea consists of carbon microspheres of varying sizes (e.g., ...). Figure 3 The addition of urea resulted in a carbon-nitrogen material that did not consist of polymer microspheres but formed a dense, blocky structure. The microstructure of nitrogen-doped coconut shell carbon in Comparative Example 4 is shown below. Figure 4 A rich macroporous structure can be observed on the surface.

[0099] Using the samples obtained in Examples 1-16 and Comparative Examples 1-4 as supports, and following the same preparation steps, with PdCl2 aqueous solution as a precursor, palladium catalysts with a loading of 0.4 wt.% were obtained after impregnation at room temperature and reduction treatment with 5% sodium formate at 50°C for 2 h.

[0100] The fresh catalysts prepared from the supports in Examples 1-16 and Comparative Examples 1-4 were used to evaluate the performance of crude terephthalic acid hydrogenation purification. The evaluation results are shown in Table 2.

[0101] The specific reaction conditions were as follows: 2.0 g catalyst, 30.0 g crude terephthalic acid (containing approximately 3300 ppm 4-CBA), 1000.0 ml aqueous solution, reaction pressure 5.5 MPa, reaction temperature 280℃, and reaction time 1.0 h. The liquid product after the reaction was quantitatively analyzed by high-performance liquid chromatography with a UV detector. The catalyst activity was evaluated by calculating the remaining 4-CBA content; the lower the remaining 4-CBA content, the higher the catalytic efficiency of the catalyst.

[0102] The fresh catalysts obtained from the supports prepared in Examples 1-16 and Comparative Examples 1-4 were subjected to aging treatment: Specifically, fresh palladium catalysts were added to a high-pressure reactor under conditions similar to the initial performance evaluation conditions and processes, except that the reaction time was extended to 17 hours. The aged catalysts were then filtered, washed, and dried, and their hydrogenation refining performance was evaluated again. The results are shown in Table 2. All treatment conditions and hydrogenation performance evaluation conditions for the obtained palladium catalysts were the same.

[0103] Table 1 Physicochemical properties of different carbon-nitrogen materials

[0104]

[0105]

[0106] The physical and chemical properties of Examples 1-16 and Comparative Examples 1 and 2 were compared (see Table 1), which confirmed that the biomass-based carbon-nitrogen material prepared by the present application had adjustable specific surface area and pore volume, and high nitrogen content. In Comparative Example 1, no nitrogen source was added, and the obtained carbon material had extremely low specific surface area (<5 m 2 / g), no pore structure, and extremely low nitrogen content. In Comparative Example 2, although a nitrogen source was added, the nitrogen content of the obtained sample was high, but because of the lack of an air calcination step, the specific surface area of the obtained sample was less than 5 m 2 / g. Therefore, the present application provides a carbon-nitrogen composite material with a porous structure, high nitrogen content, and compact structure, which can be obtained by hydrothermal reaction and air calcination under a suitable ratio of raw materials.

[0107] Table 2

[0108]

[0109]

[0110] The purpose of the aging treatment was to test the stability of the catalyst. How much the conversion rate of the catalyst decreased after the aging treatment reflected the stability of the catalyst. The smaller the conversion rate loss after aging, the better the stability of the catalyst. As can be seen from the test results in Table 2, the catalysts prepared by the present application all had high conversion efficiency of 4-CBA. Compared with the traditional coconut shell-based activated carbon-supported palladium catalyst (Comparative Example 3), the carbon-nitrogen material-supported palladium catalyst of Comparative Example 1 without nitrogen, and the three catalysts of Comparative Example 2 without air calcination, the series of biomass-based carbon-nitrogen material-supported palladium catalysts obtained by the present application all had high conversion efficiency of 4-CBA and good stability. In summary, the present application provides a new type of carbon-nitrogen material, a preparation method and catalytic application, and tests have confirmed that the carbon-nitrogen material loaded with palladium is used for crude terephthalic acid hydrogenation refining and good technical effects are achieved.

[0111] Table 3

[0112] Conversion of 4-CBA (%) Selectivity of 4-HMBA (%) Example 1 98.6 67.3 Comparative Example 1 96.7 10.2 Comparative Example 2 97.9 23.4 Comparative Example 3 97.4 9.3 Comparative Example 4 97.8 20.1

[0113] In addition, it can be seen from the catalytic performance evaluation results in Table 3 that the biomass-based carbon-nitrogen material supported palladium catalyst prepared by the present application is used for the hydrorefining reaction of crude terephthalic acid, not only can efficiently hydrogenate and convert the impurity 4-CBA, but also can highly selectively convert 4-CBA into the intermediate product 4-HMBA (hydroxymethylbenzoic acid), and the solubility of the hydrogenation product 4-HMBA in water is much greater than that of the hydrogenation product 4-PT (p-tolylbenzoic acid). The high selectivity of obtaining 4-HMBA is advantageous for subsequent product separation and purification to obtain high-purity terephthalic acid, which can effectively reduce operating costs and save energy consumption.

[0114] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and belong to the protection scope of the present application.

Claims

1. The application of a supported catalyst in the hydrogenation purification reaction of crude terephthalic acid, characterized in that, The supported catalyst is supported on a carbon-nitrogen material, and the active component is palladium; the carbon-nitrogen material contains carbon, nitrogen, and oxygen elements, and has a specific surface area of ​​5-300 m². 2 / g, pore volume 0.01-0.4cm³ 3 / g; Based on the total weight of carbon and nitrogen materials, the nitrogen content is 7.5-12.5 at.%, the carbon content is 80-95 at.%, and the oxygen content is 5-10 at.%.

2. The application according to claim 1, wherein, The carbon-nitrogen material has a blocky, dense structure in its microstructure.

3. The application according to claim 1, wherein, The specific surface area of ​​the carbon-nitrogen material is 60-280 m². 2 / g.

4. The application according to claim 1, wherein, The preparation method of the carbon-nitrogen material includes the following steps: (1) A carbon source, nitrogen source and alkali metal salt are formed into an aqueous solution, and a hydrothermal reaction is carried out under sealed conditions. After cooling, washing and drying, a solid sample is obtained. (2) The solid sample is roasted in an oxygen-containing atmosphere.

5. The application according to claim 4, wherein, The hydrothermal reaction conditions in step (1) include: a temperature of 140-200℃; and / or a time of 2-10h; and / or The mass ratio of carbon source, nitrogen source and alkali metal salt is 5-20:1-6:1; and / or In step (1), the concentration of the carbon source in the aqueous solution is 8-12% by weight.

6. The application according to claim 5, wherein, The hydrothermal reaction conditions in step (1) include: a temperature of 160-180℃; and / or a time of 4-7 hours; and / or The mass ratio of carbon source, nitrogen source and alkali metal salt is 10-15:1-6:

1.

7. The application according to claim 4, wherein, In step (2), Calcination conditions include: a temperature of 450-950℃; and / or a time of 0.5-3 hours; and / or The roasting is carried out in a tube furnace; and / or The oxygen concentration in the oxygen-containing atmosphere is 15-25% by volume.

8. The application according to claim 7, wherein, In step (2), Calcination conditions include: a temperature of 650-800℃; and / or a time of 1-2 hours; and / or The roasting conditions include: roasting in an oxygen-containing atmosphere using a stepwise method, first pre-treating at a low temperature of 200-300℃ for 0.5-1h, and then roasting at 450-950℃ for 0.5-3h.

9. The application according to claim 4, wherein, The carbon source is one or more of glucose, fructose, xylose, sucrose, chitosan, and cellulose; and / or The nitrogen source is urea and / or melamine; and / or The alkali metal salt is one or more of potassium sulfate, sodium sulfate, sodium carbonate, potassium carbonate, sodium chloride, and potassium chloride.

10. The application according to claim 9, wherein, The carbon source is glucose and / or fructose; and / or The nitrogen source is urea; and / or The alkali metal salt is one or more of potassium sulfate, sodium sulfate, sodium carbonate, and potassium carbonate.

11. The application according to claim 9, wherein, The alkali metal salt is sodium sulfate.

12. The application according to any one of claims 4-11, wherein, The preparation method of the carbon-nitrogen material includes the following steps: (1) Dissolve carbon source, nitrogen source and alkali metal salt in water in proportion, then transfer to reaction vessel, react at 140-200℃ for 2-10h, and after natural cooling, obtain solid sample by washing and drying. (2) Place the solid sample in a tube furnace and calcine it at 450-950°C for 0.5-3 hours in an oxygen-containing atmosphere.

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