A modified silicon-aluminum catalytic material, a preparation method and application thereof

Abstract

The present application relates to a kind of modified silicon-aluminum catalytic materials and its preparation method and application, which comprises: (1), the first electrically conductive object and the second electrically conductive object connected with the positive and negative of direct current power respectively are placed in aqueous solution containing silicon source and inorganic base, electrolysis is carried out under the voltage of 2-10V for 1-5 days, and mixed liquor is obtained;Wherein, the first electrically conductive object is graphite forming body;(2), the mixed liquor is mixed with silicon-aluminum catalytic material, then is transferred into heat-resistant closed container, and hydrothermal reaction is carried out under the condition of 100-250 DEG C, autogenous pressure for 12-36 hours, and solid product is collected and optionally calcined.The modified silicon-aluminum catalytic material prepared by the method of the present application has more optimal reaction activity, selectivity of target product and activity stability.

Description

Technical Field

[0001] This invention relates to a modified silicon-aluminum catalytic material, its preparation method, and its application. Background Technology

[0002] Carbon nanomaterials refer to tiny carbon particles with sizes ranging from 1 to 100 nm. Similar to ordinary nanomaterials, they also exhibit unique properties such as quantum size effects, small size effects, and macroscopic quantum tunneling effects in optics, electricity, and magnetism. Tiny carbon nanoparticles smaller than 10 nm, discovered during the purification of monolayer carbon nanotubes by electrophoresis, were first named carbon quantum dots (or simply carbon dots), a novel type of small-sized carbon nanomaterial. Due to their excellent fluorescence properties, carbon quantum dots are also known as fluorescent carbon quantum dots. In the short few years from their discovery to their application, they have become a rising star in the carbon nanomaterial family. In recent years, the properties and applications of carbon dots have been studied in increasingly detailed and comprehensive ways, ultimately achieving significant progress. Therefore, the study of the properties and applications of carbon dots has received increasing attention.

[0003] Silicon-aluminum catalysts can catalyze various types of organic reactions, such as olefin hydration, alkane isomerization, and alkylation, avoiding the problems of complex processes and environmental pollution. They possess unparalleled advantages over traditional catalytic systems, including energy saving, economy, and environmental friendliness, and exhibit good reaction selectivity, thus showing great promise for industrial application. However, the reproducibility, stability, and cost of current silicon-aluminum catalyst synthesis methods are not ideal. Therefore, improving the corresponding synthesis methods is key to the development of silicon-aluminum catalysts. Utilizing the characteristics of carbon points to modify catalytic materials is a worthwhile route for modifying silicon-aluminum catalysts. Summary of the Invention

[0004] The purpose of this invention is to provide a modified silicon-aluminum catalytic material, its preparation method, and its application. The modified silicon-aluminum catalytic material prepared by the method of this invention has multiple reactive centers and good stability, and exhibits superior reactivity and selectivity for the target product.

[0005] To achieve the above objectives, a first aspect of the present invention provides a method for modifying a silicon-aluminum catalyst, the method comprising:

[0006] (1) The first conductive material and the second conductive material, which are respectively connected to the positive and negative terminals of the DC power supply, are placed in an aqueous solution containing a silicon source and an inorganic base, and electrolyzed for 1-5 days at a voltage of 2-10V to obtain a mixed solution; wherein, the first conductive material is a graphite molded body.

[0007] (2) The mixture is mixed with the silicon-aluminum catalyst and then transferred into a heat-resistant sealed container. The mixture is subjected to a hydrothermal reaction at 100-250°C and autogenous pressure for 12-36 hours. The solid product is collected and optionally calcined.

[0008] Optionally, in step (1), the content of inorganic alkali in the aqueous solution containing silicon source and inorganic alkali is 0.5-20% by weight; the molar ratio of inorganic alkali to silicon source is 1:(0.1-1), wherein the inorganic alkali is in the form of OH- - The silicon source is calculated as SiO2; the concentration of carbon points in the mixture is 0.01-2 mg / L.

[0009] Optionally, in step (2), the weight ratio of the mixture to the silicon-aluminum catalyst is 100:(1-200), preferably 100:(5-50).

[0010] Optionally, the silicon-aluminum catalyst material is a microporous silicon-aluminum catalyst material, a mesoporous silicon-aluminum catalyst material, or an amorphous silicon-aluminum catalyst material, or a combination of two or three of them; the silicon-aluminum molar ratio of the silicon-aluminum catalyst material is 10-500, the average particle size is 0.2-5 μm, and the specific surface area is 300-1500 m². 2 / g.

[0011] Optionally, the inorganic base is sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, or ammonia, or a combination of two or three of them;

[0012] The silicon source is selected from silica sol and / or silica gel, with a content of 5-100% by weight, calculated as SiO2.

[0013] Optionally, in step (2), the conditions for the hydrothermal reaction include: a temperature of 140-180°C and a time of 12-30 hours.

[0014] Optionally, in step (2), the roasting conditions include: a temperature of 350-800℃ and a time of 1-12 hours.

[0015] The second aspect of the present invention provides a modified silicon-aluminum catalyst material prepared by the method provided in the first aspect of the present invention.

[0016] Optionally, the mesopore volume of the modified silicon-aluminum catalyst accounts for 30-70% of the total pore volume, and the ratio of the mesopore volume percentage to the mesopore specific surface area percentage is 1.2-3.0.

[0017] The third aspect of this invention provides the application of the modified silicon-aluminum catalyst provided in the second aspect of this invention in the olefin hydration reaction.

[0018] Through the above technical solutions, the modified silicon-aluminum catalytic material prepared by the method of the present invention has better reactivity, selectivity of the target product, and activity stability.

[0019] Other features and advantages of the present invention will be described in detail in the following detailed description section. Detailed Implementation

[0020] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0021] The first aspect of this invention provides a method for modifying a silicon-aluminum catalyst, the method comprising:

[0022] (1) The first conductive material and the second conductive material, which are respectively connected to the positive and negative terminals of the DC power supply, are placed in an aqueous solution containing a silicon source and an inorganic base, and electrolyzed for 1-5 days at a voltage of 2-10V to obtain a mixed solution; wherein, the first conductive material is a graphite molded body.

[0023] (2) The mixture is mixed with the silicon-aluminum catalyst and then transferred into a heat-resistant sealed container. The mixture is subjected to a hydrothermal reaction at 100-250°C and autogenous pressure for 12-36 hours. The solid product is collected and optionally calcined.

[0024] The method of the present invention, in the presence of a mixture containing carbon dots and silicon species, can cause certain defects in the silicon-aluminum catalyst during the treatment process. On the one hand, it can increase the reactive active centers of the silicon-aluminum catalyst and improve the accessibility of the active centers. On the other hand, it can increase the diffusion rate of reactants and products, thereby improving the reactivity and activity stability of the silicon-aluminum catalyst and also improving the selectivity of the target product.

[0025] According to the present invention, the graphite molded body can be a graphite rod or a graphite plate. There are no specific limitations on the dimensions of the graphite molded body and the second conductive material. Preferably, the dimensions of the graphite molded body match the dimensions of the conductive material. The dimensions of the graphite molded body can vary within a wide range. For example, when the graphite molded body is a graphite rod, the diameter of the graphite rod can be 1-18 mm, and the length can be 2-100 cm, where the length refers to the axial length of the graphite rod. When the graphite molded body is a graphite plate, the length of the graphite plate can be 10-80 cm, the width can be 1-50 cm, and the thickness can be 0.01-10 mm. The second conductive material can be any common conductive material, and there are no requirements on the material or shape. For example, the shape can be a common rod or plate, preferably a rod, such as an iron rod, graphite rod, or copper rod, and more preferably a graphite rod. There are no special limitations on the dimensions of the second conductive material, but the most preferred is a graphite rod that matches the dimensions of the graphite molded body. During electrolysis, a certain distance can be maintained between the first and second conductive materials, for example, 2-12 cm.

[0026] In a preferred embodiment of the present invention, in step (1), the electrolysis conditions include: a voltage of 2-8V and a time of 1-3 days.

[0027] According to the present invention, an aqueous solution containing a silicon source and an inorganic base is used as the electrolyte, and the content of the inorganic base in the aqueous solution containing the silicon source and the inorganic base can vary within a wide range. In a specific embodiment of the present invention, in step (1), the content of the inorganic base in the aqueous solution containing the silicon source and the inorganic base is 0.5-20% by weight, preferably 1-10% by weight. The molar ratio of the inorganic base to the silicon source is 1:(0.1-1), preferably 1:(0.2-0.7), wherein the inorganic base is in the form of OH... - The silicon source is calculated as SiO2.

[0028] In one specific embodiment of the present invention, in step (1), the concentration of carbon dots in the mixture is 0.01-2 mg / L, preferably 0.05-1.5 mg / L. Preferably, step (1) may include: concentrating the mixture. Concentration is a technique commonly used by those skilled in the art, such as membrane separation concentration, which will not be elaborated here. The carbon dot concentration of the mixture obtained after concentration can be 0.05-2 mg / mL, and more preferably, the carbon dot concentration of the carbon dot solution obtained after concentration is 0.1-1 mg / mL.

[0029] In one embodiment, the weight ratio of the mixture to the silicon-aluminum catalyst can vary within a wide range. In a specific embodiment of the present invention, in step (2), the weight ratio of the mixture to the silicon-aluminum catalyst is 100:(1-200), preferably 100:(5-50).

[0030] In one specific embodiment of the present invention, the silicon-aluminum catalytic material is a microporous silicon-aluminum catalytic material, a mesoporous silicon-aluminum catalytic material, or an amorphous silicon-aluminum catalytic material, or a combination of two or three thereof; the silicon-aluminum molar ratio of the silicon-aluminum catalytic material is 10-500, the average particle size is 0.2-5 μm, and the specific surface area is 300-1500 m². 2 / g, the average particle size refers to the average particle size detected by transmission electron microscopy or other methods on a randomly selected number of silicon-aluminum catalyst particles, such as 50. The inorganic base is sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, or ammonia, or a combination of two or three of them; the silicon source is selected from silica sol and / or silica gel, with a content of 5-100% by weight as SiO2.

[0031] According to the present invention, hydrothermal reactions are well known to those skilled in the art. In one specific embodiment of the present invention, in step (2), the conditions for the hydrothermal reaction include: a temperature of 140-180°C and a time of 12-30 hours. The present invention does not impose specific limitations on the pressure of the hydrothermal reaction; it can be the system's own pressure or it can be carried out under additional pressure, preferably under its own pressure.

[0032] According to the present invention, calcination is an operation well known to those skilled in the art. In one specific embodiment, calcination can be carried out in a muffle furnace or a tube furnace. The present invention does not impose specific limitations on the calcination atmosphere; for example, it can be an air atmosphere or an inert gas atmosphere. In one specific embodiment of the present invention, in step (2), the calcination conditions include: a temperature of 350-800°C, a time of 1-12 hours, and an atmosphere of air or nitrogen. In a preferred specific embodiment, in step (2), the collected solid product is washed and dried before calcination. The present invention does not impose specific limitations on the washing solution; for example, it can be deionized water.

[0033] According to the present invention, the method for collecting solid products is not specifically limited, and methods well known to those skilled in the art can be used, such as filtration, centrifugation, etc.

[0034] A second aspect of this invention provides a modified silica-alumina catalyst prepared by the method provided in the first aspect of this invention. Applying the method of this invention to olefin hydration reactions can improve the conversion rate of raw materials and the selectivity for target products.

[0035] In one specific embodiment of the present invention, the mesopore volume of the modified silicon-aluminum catalyst accounts for 30-70% of the total pore volume, and the ratio of the mesopore volume percentage to the mesopore specific surface area percentage is 1.2-3.0. Here, the mesopore volume percentage refers to the proportion of mesopore volume to the total pore volume, and the mesopore specific surface area percentage refers to the proportion of mesopore specific surface area to the total pore specific surface area. The mesopore volume, total pore volume, mesopore specific surface area, and total pore specific surface area are measured using the nitrogen adsorption capacity method and calculated according to the BJH calculation method.

[0036] The third aspect of this invention provides the application of the modified silicon-aluminum catalyst provided in the second aspect of this invention in the olefin hydration reaction.

[0037] The present invention will be further illustrated by the following examples, but the present invention is not limited thereto.

[0038] Unless otherwise specified, all raw materials used in the following examples and comparative examples were commercially available. The silicon-aluminum catalyst CAT-1 was purchased from Hunan Jianchang Petrochemical Technology Co., Ltd., with a silicon-aluminum molar ratio of 35, an average particle size of 0.5 micrometers, and a specific surface area of ​​430 m². 2 / g.

[0039] In the examples and comparative examples, the mesoporous specific surface area, total specific surface area, mesoporous volume and total pore volume were measured by the nitrogen adsorption capacity method and calculated according to the BJH calculation method (see Petrochemical Analytical Methods (RIPP Test Methods), RIPP151-90, Science Press, published in 1990).

[0040] Example 1

[0041] (1) At room temperature and pressure, add 800 mL of water, silica gel, and sodium hydroxide (8% by weight) to a 1000 mL beaker as the electrolyte. Place two identical graphite rods (8 mm in diameter and 50 cm in length) in the beaker, keeping the distance between the graphite rods at 5 cm. Connect the graphite rods to the positive and negative terminals of a DC power supply respectively, apply a voltage of 5 V, and electrolyze for 4 days to obtain a mixed solution. The molar ratio of sodium hydroxide to silica gel is 1:0.2, and the sodium hydroxide is in the form of OH groups. - The silica gel is calculated as SiO2; the carbon point concentration in the mixture is 0.1 mg / mL.

[0042] (2) A mixture of 2:1 by weight of the mixture and the silicon-aluminum catalyst CAT-1 was placed in a sealed high-pressure reactor and hydrothermally treated at 150°C and autogenous pressure for 8 hours. The resulting material was filtered, washed with water, naturally dried, and then calcined at 550°C for 3 hours to obtain the modified silicon-aluminum catalyst A1. Calculations showed that the mesopore volume of the modified silicon-aluminum catalyst A1 accounted for 46% of the total pore volume, and the ratio of the mesopore volume percentage to the mesopore specific surface area percentage was 1.8.

[0043] Example 2

[0044] The silicon-aluminum catalyst was modified using the same method as in Example 1 to obtain modified catalyst A2, the only difference being that in step (1), the sodium hydroxide content in the electrolyte was 25% by weight. The resulting mixture had a carbon point concentration of 2 mg / mL. Calculations showed that the mesopore volume of modified silicon-aluminum catalyst A2 accounted for 62% of the total pore volume, and the ratio of mesopore volume percentage to mesopore specific surface area percentage was 2.7.

[0045] Example 3

[0046] The silicon-aluminum catalyst was modified using the same method as in Example 1 to obtain modified catalyst A3, the only difference being that in step (1), the sodium hydroxide content in the electrolyte was 0.1% by weight. The carbon point concentration in the resulting mixture was 0.01 mg / mL. Calculations showed that the mesopore volume of the modified silicon-aluminum catalyst A3 accounted for 31% of the total pore volume, and the ratio of mesopore volume percentage to mesopore specific surface area percentage was 1.2.

[0047] Example 4

[0048] The silicon-aluminum catalyst was modified using the same method as in Example 1 to obtain modified catalyst A4, except that in step (2), the weight ratio of silicon-aluminum catalyst to the mixture was 1:0.5. Calculations showed that the mesopore volume of the modified silicon-aluminum catalyst A4 accounted for 33% of the total pore volume, and the ratio of mesopore volume percentage to mesopore specific surface area percentage was 1.4.

[0049] Comparative Example 1

[0050] The silicon-aluminum catalyst was modified using the same method as in Example 1 to obtain modified catalyst DA1, the only difference being that no silicon source was added in step (1).

[0051] (1) At room temperature and pressure, add 800 mL of water and sodium hydroxide (sodium hydroxide content is 8% by weight) to a 1000 mL beaker as electrolyte. Place two identical graphite rods (diameter 8 mm, length 50 cm) in the beaker, keeping the distance between the graphite rods at 5 cm. Connect the graphite rods to the positive and negative terminals of a DC power supply respectively, apply a voltage of 5 V and electrolyze for 4 days to obtain a mixed solution. The carbon point concentration in the mixed solution is 0.14 mg / mL.

[0052] (2) A mixture of 2:1 by weight was mixed with CAT-1, a silicon-aluminum catalyst, and placed in a sealed high-pressure reactor. The mixture was hydrothermally treated at 150°C and autogenous pressure for 8 hours. The resulting material was filtered, washed with water, naturally dried, and then calcined at 550°C for 3 hours to obtain modified silicon-aluminum catalyst DA1. Calculations showed that the mesopore volume of modified silicon-aluminum catalyst DA1 accounted for 72% of the total pore volume, and the ratio of mesopore volume percentage to mesopore specific surface area percentage was 3.3.

[0053] Comparative Example 2

[0054] A sodium hydroxide aqueous solution with a weight ratio of 2:1 was stirred and mixed evenly with the silicon-aluminum catalyst. The resulting mixture was placed in a sealed high-pressure reactor and hydrothermally treated at 150°C and autogenous pressure for 48 hours. The resulting material was filtered, washed with water, naturally dried, and then calcined at 550°C for 3 hours to obtain the modified silicon-aluminum catalyst DA2. Calculations showed that the mesopore volume of the modified silicon-aluminum catalyst DA2 accounted for 71% of the total pore volume, and the ratio of mesopore volume percentage to mesopore specific surface area percentage was 3.5.

[0055] The sodium hydroxide content in the aqueous solution is the same as the sodium hydroxide content in the mixture in Example 1.

[0056] Comparative Example 3

[0057] (1) At room temperature and pressure, add 800 mL of water and sodium hydroxide (sodium hydroxide content is 8% by weight) to a 1000 mL beaker as electrolyte. Place two identical graphite rods (diameter 8 mm, length 50 cm) in the beaker, keeping the distance between the graphite rods at 5 cm. Connect the graphite rods to the positive and negative terminals of a DC power supply respectively, apply a voltage of 5 V and electrolyze for 4 days to obtain an alkaline carbon point solution; the carbon point concentration in the mixture is 0.14 mg / mL.

[0058] (2) The silica gel and the alkaline carbon dot solution are mixed for the first time to obtain a mixture; wherein the molar ratio of sodium hydroxide in step (1) to silica gel in step (2) is 1:0.2, and the sodium hydroxide is in the form of OH groups. - The silica gel is calculated as SiO2.

[0059] (3) A mixture of 2:1 by weight was mixed with CAT-1, a silicon-aluminum catalyst, and placed in a sealed high-pressure reactor. The mixture was hydrothermally treated at 150°C and autogenous pressure for 8 hours. The resulting material was filtered, washed with water, naturally dried, and then calcined at 550°C for 3 hours to obtain the modified silicon-aluminum catalyst DA3. Calculations showed that the mesopore volume of the modified silicon-aluminum catalyst DA3 accounted for 22% of the total pore volume, and the ratio of mesopore volume percentage to mesopore specific surface area percentage was 1.0.

[0060] Test Example 1

[0061] The unmodified silica-alumina catalyst CAT, as well as the modified catalysts prepared in the examples and comparative examples, were used as catalysts for the cyclohexene catalytic hydration reaction.

[0062] The silicon-aluminum catalyst (modified or unmodified), cyclohexene, and water were sealed in a high-pressure reactor at a weight ratio of silicon-aluminum catalyst:cyclohexene:water = 4:100:900, and reacted at an autogenous pressure of 140°C for 2 hours.

[0063] The product distribution of the reaction products was determined by a Varian 3400 gas chromatograph with a capillary column (30m × 0.25mm) and FFAP. The results are shown in Table 1.

[0064] The following formulas are used to calculate the feed conversion rate and target product selectivity:

[0065] Cyclohexene conversion rate = (molar amount of cyclohexene added before reaction - molar amount of cyclohexene remaining after reaction) / molar amount of cyclohexene added before reaction × 100%.

[0066] Cyclohexanol selectivity = (molar amount of cyclohexanol produced in the reaction) / (molar amount of cyclohexene added before the reaction - molar amount of cyclohexene remaining after the reaction) × 100%.

[0067] Table 1

[0068] Cyclohexene conversion, % Cyclohexanol selectivity, % CAT 79 90 Example 1 95 98 Example 2 93 94 Example 3 96 96 Example 4 94 93 Comparative Example 1 83 89 Comparative Example 2 86 75 Comparative Example 3 77 81

[0069] Test Example 2

[0070] The catalysts used in Test Example 1, Examples 1-4, and Comparative Examples 1-3 were filtered and removed, and then subjected to olefin hydration reaction again under the conditions of Test Example 1. The test results after 5 repetitions are shown in Table 2.

[0071] Table 2

[0072]

[0073]

[0074] As can be seen from the above, the modified catalytic material prepared by the method of the present invention has better reactivity, selectivity of the target product, and activity stability in olefin hydration reaction.

[0075] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0076] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0077] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. The application of a modified silica-alumina catalyst in the hydration reaction of olefins, wherein the modified silica-alumina catalyst is prepared by the following method, the method comprising: (1) A first conductive material and a second conductive material, respectively connected to the positive and negative terminals of a DC power supply, are placed in an aqueous solution containing a silicon source and an inorganic alkali, and electrolyzed for 1-5 days at a voltage of 2-10V to obtain a mixed solution; wherein, the first conductive material is a graphite molded body; wherein, the content of inorganic alkali in the aqueous solution containing the silicon source and the inorganic alkali is 0.5-20% by weight; the molar ratio of the inorganic alkali to the silicon source is 1:(0.1-1), wherein the inorganic alkali is in the form of OH... - The silicon source is calculated as SiO2; the concentration of carbon points in the mixture is 0.01-2 mg / L; the silicon source is selected from silica sol and / or silica gel, and its content as SiO2 is 5-100% by weight%. (2) The mixture is mixed with the silicon-aluminum catalyst and then transferred to a heat-resistant sealed container. A hydrothermal reaction is carried out at 100-250°C and under autogenous pressure for 12-36 hours. The solid product is collected and optionally calcined. The weight ratio of the mixture to the silicon-aluminum catalyst is 100:(5-50). The silicon-aluminum molar ratio of the silicon-aluminum catalyst is 10-500, the average particle size is 0.2-5 μm, and the specific surface area is 300-1500 m². 2 / g.

2. The application according to claim 1, wherein, The silicon-aluminum catalytic material is a microporous silicon-aluminum catalytic material, a mesoporous silicon-aluminum catalytic material, or an amorphous silicon-aluminum catalytic material, or a combination of two or three of them.

3. The application according to claim 1, wherein, The inorganic base is sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, or ammonia, or a combination of two or three of them.

4. The application according to claim 1, wherein, In step (2), the conditions for the hydrothermal reaction include: a temperature of 140-180℃ and a time of 12-30 hours.

5. The application according to claim 1, wherein, In step (2), the roasting conditions include: a temperature of 350-800℃ and a time of 1-12 hours.

6. The application according to claim 1, wherein, The modified silicon-aluminum catalyst material has a mesopore volume accounting for 30-70% of the total pore volume, and the ratio of mesopore volume to mesopore specific surface area is 1.2-3.0.

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