Spherical alumina, supported catalyst and preparation method and application thereof

Abstract

The invention belongs to the technical field of catalysts, and particularly relates to spherical aluminum oxide, a supported catalyst and a preparation method and application of the supported catalyst. The preparation method of the spherical aluminum oxide provided by the invention comprises the following steps: mixing and kneading aluminum oxide powder, an adhesive and water, and extruding into strips to obtain a strip-shaped sample; and rolling the strip-shaped sample, and carrying out first calcination to obtain the spherical aluminum oxide. According to the invention, the alumina powder is prepared into alumina balls with high sphericity through a process of combining kneading, strip extrusion and ball rolling, and the diameter of the spherical alumina can be regulated and controlled by regulating the diameter of a strip-shaped sample obtained by strip extrusion. The spherical aluminum oxide provided by the invention is used as a carrier to load noble metal to prepare a supported catalyst, and the supported catalyst can be used for a fixed bed reactor and has good catalytic activity and catalytic efficiency on hydrogenation and dehydrogenation reactions.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and particularly relates to a spherical alumina, a supported catalyst, and a preparation method and application thereof. Background Art

[0002] As a good hydrogenation catalytic carrier material, alumina has a wide range of applications in the refining industry. The particle size of the spherical alumina prepared by the existing preparation methods is mostly in the micron range. For example, micron-sized spherical alumina is prepared by a method of primary demagnetization and flame spraying. However, the micron-sized spherical alumina prepared according to the existing methods is mainly used as an inorganic filler material in the preparation of ceramic materials and glass fibers, and it is difficult to be used in a fixed-bed reactor, which will cause problems such as excessive bed pressure drop and bed plugging. Summary of the Invention

[0003] In view of this, the present invention provides a spherical alumina, a supported catalyst, and a preparation method and application thereof. The spherical alumina prepared according to the preparation method provided by the present invention has good sphericity and its diameter is controllable, and it can be directly used in a fixed-bed reactor. The supported catalyst prepared by using the spherical alumina provided by the present invention has good catalytic activity for both hydrogenation and dehydrogenation reactions.

[0004] In order to solve the above technical problems, the present invention provides a preparation method of spherical alumina, comprising the following steps:

[0005] Mix alumina powder, binder and water, and then extrude to obtain a strip-shaped sample;

[0006] Roll the strip-shaped sample into balls and then perform a first calcination to obtain the spherical alumina.

[0007] Preferably, the binder includes inorganic acid, formic acid, acetic acid or citric acid;

[0008] The mass ratio of the alumina powder to the binder is 100:0.5 - 6;

[0009] The mass ratio of the alumina powder to water is 1:0.5 - 2.0.

[0010] Preferably, the extrusion method includes using a single-screw automatic feeding extruder for extrusion;

[0011] The average diameter of the strip-shaped sample is 0.6 mm or more.

[0012] Preferably, the ball rolling method is to place the strip-shaped sample in a ball rolling machine for ball formation.

[0013] Preferably, the temperature of the first calcination is 500 - 600 °C, and the heat preservation time is 3 - 6 h.

[0014] The present invention also provides spherical alumina prepared by the preparation method according to the above technical solution. The average diameter of the spherical alumina is above 0.6 mm, the sphericity of the spherical alumina is 0.911 - 0.986, and the strength of the spherical alumina is 6.7 - 10.7 N / particle.

[0015] The present invention also provides the application of the spherical alumina according to the above technical solution as a catalyst support.

[0016] The present invention also provides a supported catalyst, which comprises a support and a catalytic active component supported on the support. The support is the spherical alumina according to the above technical solution, and the catalytic active component comprises a noble metal;

[0017] The loading amount of the catalytic active component in the supported catalyst is 0.5 - 4 wt%.

[0018] The present invention also provides a preparation method of the supported catalyst according to the above technical solution, which comprises the following steps:

[0019] Adopt the equal volume impregnation method to impregnate the noble metal salt solution onto the spherical alumina support to obtain spherical alumina loaded with noble metal salt;

[0020] Perform a second calcination on the spherical alumina loaded with noble metal salt to obtain the supported catalyst.

[0021] The present invention also provides the application of the supported catalyst according to the above technical solution or the supported catalyst prepared by the preparation method according to the above technical solution in a hydrogenation reaction or dehydrogenation reaction in a fixed bed reactor.

[0022] The present invention provides a preparation method of spherical alumina, which comprises the following steps: Knead alumina powder, binder and water, and then extrude to obtain a strip-shaped sample; Roll the strip-shaped sample into balls and then perform a first calcination to obtain the spherical alumina. The present invention prepares alumina powder into alumina balls with a relatively high sphericity through a process combining kneading, extrusion and ball rolling, and the diameter of the spherical alumina can be controlled by adjusting the diameter of the strip-shaped sample obtained by extrusion. Using the spherical alumina provided by the present invention as a support to load noble metal to prepare a supported catalyst, the supported catalyst can be used in a fixed bed reactor and has good catalytic activity and catalytic efficiency for both hydrogenation and dehydrogenation reactions. Description of the Drawings

[0023] Figure 1Photographs of the spherical alumina prepared in Examples 1-7, where a is the photograph of the spherical alumina prepared in Example 1, b is the photograph of the spherical alumina prepared in Example 2, c is the photograph of the spherical alumina prepared in Example 3, d is the photograph of the spherical alumina prepared in Example 4, e is the photograph of the spherical alumina prepared in Example 5, f is the photograph of the spherical alumina prepared in Example 6, and g is the photograph of the spherical alumina prepared in Example 7;

[0024] Figure 2 Nitrogen adsorption-desorption isotherms of the supported catalysts prepared in Examples 1-7. Detailed implementation manners

[0025] The present invention provides a method for preparing spherical alumina, comprising the following steps:

[0026] Mix alumina powder, binder and water by kneading and then extrude to obtain a strip-shaped sample;

[0027] Roll the strip-shaped sample into balls and then perform the first calcination to obtain the spherical alumina.

[0028] In the present invention, alumina powder, binder and water are mixed by kneading and then extruded to obtain a strip-shaped sample. As a specific implementation manner of the present invention, the average particle size of the alumina powder can be 10-100 μm, can also be 30-80 μm, and can further be 38-75 μm. As a specific implementation manner of the present invention, the binder may include inorganic acid, formic acid, acetic acid or citric acid; the inorganic acid may include nitric acid or hydrochloric acid, and the mass concentration of the inorganic acid can be 1-100%, can also be 10-98%. As a specific implementation manner of the present invention, the water can be deionized water or high-purity water. As a specific implementation manner of the present invention, the mass ratio of the alumina powder to the binder can be 100:0.5-6, specifically 100:2, 100:2.4, 100:3, 100:3.5 or 100:5; the mass ratio of the alumina powder to the water can be 1:0.5-2.0, specifically 1:0.5, 1:0.9, 1:1, 1:1.1, 1:1.5 or 1:1.8.

[0029] As a specific implementation manner of the present invention, the kneading can be carried out in a kneader. The kneading can first add the alumina powder to the kneader and then add the binder and water; the kneading time can be 4-6 min, specifically 4 min, 5 min or 6 min.

[0030] As a specific embodiment of the present invention, the method of extrusion molding may include using a single-screw automatic feeding extruder for extrusion, and the extrusion die of the single-screw automatic feeding extruder is a round-hole die; the diameter of the strip-shaped sample may be 0.6 mm or more, specifically 0.8 mm, 1 mm or 1.2 mm. In the present invention, the diameter of the strip-shaped sample is determined by the diameter of the round hole of the round-hole die. The present invention regulates the diameter of spherical alumina by adjusting the diameter of the strip-shaped sample, and the diameter of the strip-shaped sample is 0.2 - 0.3 mm smaller than the diameter of spherical alumina.

[0031] After obtaining the strip-shaped sample, the present invention rolls the strip-shaped sample into balls and then performs the first calcination to obtain the spherical alumina. As a specific embodiment of the present invention, the method of rolling into balls may be to place the strip-shaped sample in a ball rolling machine for ball forming; the air-blowing pressure of the ball rolling machine may be 0.2 - 0.22 MPa, the rotation speed may be 1800 - 1900 rpm, and the rolling time is 3 - 4 min.

[0032] As a specific embodiment of the present invention, before the first calcination, it may further include: drying the product after rolling into balls at room temperature, and the temperature of the room temperature environment may be 20 - 35 °C, or 25 - 30 °C; the present invention has no special limitation on the drying time, as long as the solvent in the product after rolling into balls can be removed.

[0033] As a specific embodiment of the present invention, the temperature of the first calcination may be 500 - 600 °C, or 550 - 580 °C; the heat preservation time of the first calcination may be 3 - 6 h, or 4 - 5 h; the first calcination can be carried out in an air atmosphere.

[0034] Through the first calcination, the present invention can remove the adhesives and other impurities added during molding (extrusion), and γ-alumina can be obtained after the first calcination.

[0035] The preparation method provided by the present invention has a simple preparation process and a high ball forming rate.

[0036] The present invention also provides spherical alumina prepared by the preparation method according to the above technical solution. The average diameter of the spherical alumina is 0.6 mm or more, and can be 0.6 - 3 mm, specifically 1 mm, 1.2 mm or 1.5 mm; the sphericity of the spherical alumina is 0.911 - 0.986, specifically 0.911, 0.932, 0.939, 0.976, 0.981, 0.983 or 0.986; the strength of the spherical alumina is 6.7 - 10.7 N / particle, specifically 6.7 N / particle, 7.0 N / particle, 8.8 N / particle, 9.0 N / particle, 9.5 N / particle, 10 N / particle or 10.7 N / particle.

[0037] The spherical alumina provided by the present invention has high strength, uniform small particle size, and is not easy to agglomerate, which is beneficial to improving the catalytic performance of the supported catalyst with spherical alumina as the carrier. At the same time, the spherical alumina provided by the present invention has moderate acidity and high hydrogenation and dehydrogenation activities after loading precious metals.

[0038] The present invention also provides an application of the spherical alumina described in the above technical solution as a catalyst carrier.

[0039] The present invention also provides a supported catalyst, which includes a carrier and a catalytic active component supported on the carrier. The carrier is the spherical alumina described in the above technical solution, and the catalytic active component includes precious metals, and the precious metals can be platinum or palladium. The loading amount of the catalytic active component in the supported catalyst is 0.5-4 wt%, and can specifically be 1 wt%, 2 wt%, 3 wt% or 4 wt%.

[0040] The present invention also provides a preparation method of the supported catalyst described in the above technical solution, including the following steps:

[0041] The precious metal salt solution is impregnated onto the spherical alumina carrier by the equal-volume impregnation method to obtain spherical alumina loaded with precious metal salts.

[0042] The spherical alumina loaded with precious metal salts is subjected to a second calcination to obtain the supported catalyst.

[0043] In the present invention, the precious metal salt solution is impregnated onto the spherical alumina carrier by the equal-volume impregnation method to obtain spherical alumina loaded with precious metal salts. As a specific embodiment of the present invention, the precious metal salts in the precious metal salt solution may include chloroplatinic acid hexahydrate, tetraammineplatinum nitrate or palladium chloride. The present invention has no special limitation on the mass concentration and dosage of the precious metal salt solution, as long as the loading amount of the precious metal can be satisfied. As a specific embodiment of the present invention, the method of impregnating the precious metal salt solution onto the spherical alumina carrier may be spraying or dropping the precious metal salt solution onto the spherical alumina carrier.

[0044] After obtaining the spherical alumina loaded with precious metal salts, the present invention subjects the spherical alumina loaded with precious metal salts to a second calcination to obtain the supported catalyst. As a specific embodiment of the present invention, the temperature of the second calcination may be 300-500 °C, and may specifically be 350 °C, 400 °C or 450 °C; the time of the second calcination may be 2-6 h, and may also be 3-4 h.

[0045] The second calcination in the present invention can strengthen the interaction between the precious metal active phase and the carrier.

[0046] The supported catalyst provided by the present invention has high strength and is not easily broken even after loading noble metals by the equal-volume impregnation method, and has high catalytic efficiency.

[0047] The present invention also provides the application of the supported catalyst described in the above technical solution or the supported catalyst prepared by the preparation method described in the above technical solution in the hydrogenation reaction or dehydrogenation reaction in a fixed-bed reactor. Before the catalytic hydrogenation reaction or catalytic dehydrogenation reaction of the supported catalyst of the present invention, reduction activation is required. The reduction activation can be to reduce the supported catalyst in a reducing atmosphere to obtain an activated catalyst. As a specific embodiment of the present invention, the reducing atmosphere can be hydrogen; the pressure of the reduction system can be 0.8 to 1.2 MPa, specifically 1 MPa; the reduction temperature can be 330 to 370 °C, specifically 350 °C; the reduction time can be 20 to 26 h, or 22 to 24 h. After reduction activation according to the present invention, the noble metal oxide in the supported catalyst can be reduced to noble metal.

[0048] The present invention has no special requirements for the catalytic hydrogenation reaction or catalytic dehydrogenation reaction using the supported catalyst, and the conventional methods in the art can be adopted.

[0049] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0050] Example 1

[0051] (1) Alumina powder with an average particle size of 75 μm was added to a kneader, and then nitric acid with a mass concentration of 68% and deionized water were added to the kneader, and stirred at room temperature (25 °C) for 5 min to obtain a mixed sample; the mass ratio of alumina powder to nitric acid was 100:1, and the weight ratio of deionized water to alumina powder was 1:1.

[0052] (2) The mixed sample was put into a single-screw automatic feeding and extrusion machine (the extrusion die was a round die with a diameter of 1.2 mm) for extrusion molding to obtain a strip-shaped sample with a diameter of 1.2 mm.

[0053] (3) The strip-shaped sample was put into a ball rolling machine for ball rolling. The obtained alumina balls with an average diameter of 1.5 mm were naturally dried at room temperature (25 °C) and then calcined in a muffle furnace at 550 °C for 4 h to obtain spherical alumina with an average diameter of 1.5 mm; the conditions for ball rolling were: air blowing pressure 0.2 MPa, rotation speed 1800 rpm, and rolling time 3 min.

[0054] (4) The noble metal Pt was loaded by the equal - volume impregnation method (spraying an aqueous solution of chloroplatinic acid onto spherical alumina), obtaining spherical alumina loaded with chloroplatinic acid. The mass concentration and dosage of the aqueous solution of chloroplatinic acid were calculated with the Pt loading amount of 1 wt% as the target.

[0055] (5) The spherical alumina loaded with chloroplatinic acid was calcined at 400 °C for 4 h, obtaining a Pt / 1.5 - mm alumina - supported catalyst with a Pt loading amount of 1 wt%.

[0056] Example 2

[0057] (1) Alumina powder with an average particle size of 50 μm was added to a kneader, and then acetic acid with a mass concentration of 99.5% and deionized water were added to the kneader. It was stirred at room temperature (25 °C) for 5 min to obtain a mixed sample; the mass ratio of alumina powder to acetic acid was 100:5, and the weight ratio of deionized water to alumina powder was 0.9:1.

[0058] (2) The mixed sample was put into a single - screw automatic feeding extrusion machine (the extrusion die was a round - hole die with a diameter of 1.0 mm) for extrusion molding to obtain a strip - shaped sample with a diameter of 1.0 mm.

[0059] (3) The strip - shaped sample was put into a ball - rolling machine for ball - rolling. The obtained alumina balls with an average diameter of 1.2 mm were naturally dried at room temperature (25 °C) and then calcined in a muffle furnace at 500 °C for 5 h to obtain spherical alumina with an average diameter of 1.2 mm; the conditions for ball - rolling were: blast pressure 0.22 MPa, rotation speed 1900 rpm, and rolling time 4 min.

[0060] (4) The noble metal Pt was loaded by the equal - volume impregnation method (spraying an aqueous solution of chloroplatinic acid onto spherical alumina), obtaining spherical alumina loaded with chloroplatinic acid. The mass concentration and dosage of the aqueous solution of chloroplatinic acid were calculated with the Pt loading amount of 2 wt% as the target;

[0061] (5) The spherical alumina loaded with palladium chloride was calcined at 450 °C for 4 h, obtaining a Pt / 1.2 - mm alumina - supported catalyst with a Pt loading amount of 2 wt%.

[0062] Example 3

[0063] (1) Alumina powder with an average particle size of 38 μm was added to a kneader, and then acetic acid with a mass concentration of 99.5% and deionized water were added to the kneader. It was stirred at room temperature (25 °C) for 5 min to obtain a mixed sample; the mass ratio of alumina powder to acetic acid was 100:3.5, and the weight ratio of deionized water to alumina powder was 1:1.

[0064] (2) Put the mixed sample into a single-screw automatic feeding and extrusion machine (the extrusion die is a round hole die with a diameter of 0.8 mm) for extrusion molding to obtain a strip-shaped sample with a diameter of 0.8 mm.

[0065] (3) Put the strip-shaped sample into a ball rolling machine for ball rolling. The obtained alumina balls with an average diameter of 1.0 mm are naturally dried at room temperature (25 °C) and then calcined in a muffle furnace at 600 °C for 3 h to obtain spherical alumina with an average diameter of 1.0 mm. The conditions for ball rolling are: blast pressure 0.22 MPa, rotation speed 1900 rpm, and rolling time 3 min.

[0066] (4) Use the equal-volume impregnation method (spray the aqueous solution of chloroplatinic acid onto the spherical alumina) to load the noble metal Pt to obtain spherical alumina loaded with chloroplatinic acid. Calculate the mass concentration and dosage of the aqueous solution of chloroplatinic acid with a Pt loading of 4 wt% as the target.

[0067] (5) Calcinate the spherical alumina loaded with palladium chloride at 350 °C for 5 h to obtain a Pt / 1.0 mm alumina-supported catalyst with a Pt loading of 4 wt%.

[0068] Example 4

[0069] Prepare the supported catalyst according to the method of Example 1, except that in step (1), the nitric acid with a mass concentration of 68% is replaced by citric acid with a mass concentration of 99%, and the mass ratio of alumina powder to citric acid is 100:3. The Pt loading in the obtained Pt / 1.5 mm alumina-supported catalyst is 3 wt%, and the mass concentration and dosage of the aqueous solution of chloroplatinic acid are calculated with a Pt loading of 3 wt% as the target during the equal-volume impregnation process.

[0070] Example 5

[0071] Prepare the supported catalyst according to the method of Example 2, except that in step (2), the diameter of the round hole of the extrusion die is replaced from 1.0 mm to 0.8 mm, and the Pt loading in the obtained Pt / 1.0 mm alumina-supported catalyst is 2 wt%.

[0072] Example 6

[0073] Prepare the supported catalyst according to the method of Example 3, except that in step (1), the acetic acid with a mass concentration of 99.5% is replaced by nitric acid with a mass concentration of 68%, and the mass ratio of alumina powder to nitric acid is adjusted from 100:3 to 100:2.4; in step (2), the diameter of the round hole of the extrusion die is adjusted from 0.8 mm to 1.0 mm. The Pt loading in the obtained Pt / 1.2 mm alumina-supported catalyst is 4 wt%.

[0074] Example 7

[0075] The supported catalyst was prepared according to the method of Example 1, except that in step (1), deionized water was replaced by high-purity water, and the weight ratio of high-purity water to alumina powder was adjusted to 1.1:1.

[0076] Figure 1 FIG. is a physical diagram of the spherical alumina prepared in Examples 1-7, where a is the physical diagram of the spherical alumina prepared in Example 1, b is the physical diagram of the spherical alumina prepared in Example 2, c is the physical diagram of the spherical alumina prepared in Example 3, d is the physical diagram of the spherical alumina prepared in Example 4, e is the physical diagram of the spherical alumina prepared in Example 5, f is the physical diagram of the supported catalyst prepared in Example 6, and g is the physical diagram of the spherical alumina prepared in Example 7. As can be seen from Figure 1 It can be seen that the spherical alumina prepared by this method has a high sphericity and uniform size.

[0077] The supported catalysts prepared in Examples 1-7 were subjected to nitrogen adsorption-desorption tests to obtain nitrogen adsorption-desorption curves, as Figure 2 shown. The specific surface areas and average pore diameters obtained from the nitrogen adsorption-desorption test results are listed in Table 1.

[0078] The particle strength of the supported catalysts prepared in Examples 1-7 was detected using a particle compressive strength tester, and the results are listed in Table 1.

[0079] The sphericity results of the supported catalysts prepared in Examples 1-7 are listed in Table 1.

[0080] Table 1 Performance of the supported catalysts prepared in Examples 1-7

[0081]

[0082]

[0083] As can be seen from the results in Table 1, the spherical alumina prepared according to the preparation method provided by the present invention has a high sphericity; the supported catalyst prepared using the spherical alumina as a carrier has a large specific surface area and high particle strength.

[0084] The specific reaction processes of using the supported catalysts prepared in Examples 1-7 for hydrogenation and dehydrogenation reactions are as follows: The supported catalysts are respectively loaded into a fixed-bed reactor. Hydrogen is introduced, and the temperature is raised to 350 °C and maintained for 24 h under a pressure of 1 MPa to reduce and activate the supported catalysts. After the catalyst activation is completed, the system pressure is maintained at 0.2 MPa by adjusting the hydrogen flow rate, and the liquid injection rate is adjusted to carry out the catalytic dehydrogenation reaction of dibenzyltoluene at 350 °C (the temperature of the fixed-bed reactor). A gas mass flowmeter is connected to the tail end of the gas phase outlet of the fixed-bed reactor to observe the instantaneous flow rate of hydrogen in real time. According to the feed flow rate, the theoretical hydrogen flow rate after complete dehydrogenation can be calculated, and thus the hydrogen production rate of the catalyst can be calculated. The results are listed in Table 2.

[0085] Table 2 Catalytic performance of the supported catalysts prepared in Examples 1-7

[0086] Example Hydrogen production rate (%) Example 1 86.07 Example 2 87.62 Example 3 93.01 Example 4 89.17 Example 5 94.13 Example 6 92.80 Example 7 87.12

[0087] As can be seen from Table 2, the supported catalysts provided by the present invention have good catalytic performance and catalytic efficiency for hydrogenation and dehydrogenation reactions in a fixed-bed reactor.

[0088] Although the above embodiments have made a detailed description of the present invention, they are only a part of the embodiments of the present invention, rather than all embodiments. People can also obtain other embodiments based on these embodiments without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing spherical alumina, characterized in that: The following steps are involved: Alumina powder, adhesive and water are kneaded and then extruded to obtain a strip sample; The strip sample is ball-rolled and then subjected to a first calcination to obtain the spherical alumina.

2. The preparation method according to claim 1, characterized in that: The adhesive includes inorganic acid, formic acid, acetic acid or citric acid; The mass ratio of the alumina powder to the adhesive is 100:0.5-6; The mass ratio of the aluminum oxide powder to water is 1:0.5-2.

0.

3. The preparation method according to claim 1, characterized in that: The extrusion method includes using a single-screw automatic press extruder to extrude the strips; The average diameter of the strip samples is greater than 0.6 mm.

4. The preparation method according to claim 1, characterized in that: The ball rolling method is to place the strip sample in a ball rolling machine to form a ball.

5. The preparation method according to claim 1, characterized in that: The temperature of the first calcination is 500-600° C., and the holding time is 3-6 hours.

6. The spherical alumina prepared by the preparation method according to any one of claims 1 to 5, characterized in that: The average diameter of the spherical alumina is greater than 0.6 mm, the sphericity of the spherical alumina is 0.911 to 0.986, and the strength of the spherical alumina is 6.7 to 10.7 N / particle.

7. Use of the spherical alumina according to claim 6 as a catalyst carrier.

8. A supported catalyst, characterized in that It comprises a carrier and a catalytically active component supported in the carrier, wherein the carrier is the spherical alumina according to claim 6, and the catalytically active component comprises a noble metal; The loading amount of the catalytically active component in the supported catalyst is 0.5 to 4 wt%.

9. The method for preparing a supported catalyst according to claim 8, characterized in that: The following steps are involved: The noble metal salt solution is impregnated into the spherical alumina carrier by an equal volume impregnation method to obtain the spherical alumina loaded with the noble metal salt; The spherical alumina loaded with the noble metal salt is subjected to a second calcination to obtain the loaded catalyst.

10. Use of the supported catalyst according to claim 8 or the supported catalyst prepared by the preparation method according to claim 9 in a fixed bed reactor for hydrogenation reaction or dehydrogenation reaction.

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