Alumina particles and preparation method thereof

Abstract

The present invention relates to the field of catalyst carrier preparation and discloses alumina particles and a method for preparing the same. The method comprises: 1) mixing a chitosan polymer, an aluminum source, and optionally water to form a slurry; 2) dripping the slurry into an acidic solution to undergo a cross-linking reaction to produce solidified particles; and 3) calcining the solidified particles to produce the alumina particles. The method provides a method for preparing alumina particles using chitosan polymer-assisted molding. Compared to existing methods, the method is simpler to operate, has lower energy consumption, requires less equipment, and is a green and clean preparation process, effectively addressing the issue of pollutant emissions during catalyst carrier preparation.

Description

Technical Field

[0001] The present invention relates to the field of catalyst carrier preparation, and in particular to aluminum oxide particles and a preparation method thereof. Background Art

[0002] Catalyst carriers are important consumables in chemical and industrial catalysis. Alumina is widely used as a catalyst carrier in industry due to its excellent physical and chemical properties, including special pore structure, surface properties and good stability.

[0003] The drop ball method is a technology for forming alumina particles, primarily encompassing the hot oil column method and its improved oil-ammonia column method. The hot oil column method inevitably discharges large amounts of organic solvents during the preparation process, which are difficult to dispose of harmlessly. Because the binder needs to accelerate dehydration and aging, the oil column must be maintained at a certain temperature (98-180°C), consuming considerable energy. Furthermore, sufficient time is required to strengthen the droplets to prevent collisions and adhesion before they solidify. The oil-ammonia column method requires treatment of the oil and ammonia layers after a period of use, generating significant wastewater that requires disposal. Crucially, both oil and ammonia are volatile, posing a risk to the environment and human health. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing alumina particles by chitosan-based polymer-assisted molding. Compared with existing methods, the method has simple operation, low energy consumption, simple equipment, and a green and clean preparation process, which effectively solves the pollution emission problem in the catalyst carrier preparation process.

[0005] In order to achieve the above object, the present invention provides a method for preparing aluminum oxide particles, wherein the method comprises the following steps:

[0006] 1) mixing a chitosan polymer, an aluminum source, and optionally water to form a slurry;

[0007] 2) dropping the slurry into an acidic solution to undergo a cross-linking reaction to obtain solidified particles;

[0008] 3) calcining the solidified particles to obtain alumina particles.

[0009] Preferably, the weight ratio of the chitosan polymer to the aluminum source calculated as aluminum element is 1:0.1-50, preferably 1:1-10, more preferably 1:1-5, more preferably 1:1.3-3, and even more preferably 1:1.5-3.

[0010] Preferably, the content of the slurry in terms of aluminum element is 1-25% by weight, preferably 2-10% by weight, more preferably 3-8% by weight, and further preferably 5-6% by weight.

[0011] Preferably, the aluminum source is pseudo-boehmite and / or aluminum sol.

[0012] Preferably, the pseudo-boehmite has a mesh size of 80-800 meshes.

[0013] Preferably, the aluminum sol has an aluminum content of 1-50% by weight, preferably 2-10% by weight, more preferably 3-8% by weight, and further preferably 5-6% by weight.

[0014] Preferably, the aluminum sol is aluminum oxide hydrogel and / or nano aluminum oxide sol.

[0015] Preferably, the chitosan polymer is one or more of chitosan, carboxymethyl chitosan, hydroxyethyl chitosan, hydroxypropyl chitosan and carboxymethylated hydroxypropyl chitosan.

[0016] Preferably, the acidic solution is one or more of an aqueous sulfuric acid solution, an aqueous nitric acid solution, an aqueous hydrochloric acid solution, an aqueous acetic acid solution, an aqueous oxalic acid solution, and an aqueous citric acid solution;

[0017] Preferably, the molar concentration of the acidic solution is above 0.1 mol / L, preferably 0.1-17.5 mol / L.

[0018] Preferably, the amount of the acidic solution is 1-5 parts by weight relative to 1 part by weight of the slurry.

[0019] Preferably, the cross-linking reaction conditions include: temperature of 5-45° C. and time of 0.5-5 hours.

[0020] Preferably, the calcination conditions include: a temperature of 500-1200° C. and a time of 1-3 hours; more preferably, the calcination conditions include: a temperature of 600-800° C. and a time of 1-2 hours.

[0021] Preferably, the calcination conditions include: a temperature of 600-800° C. and a time of 1-4 hours.

[0022] According to a second aspect of the present invention, provided are aluminum oxide particles prepared by the method for preparing aluminum oxide particles of the present invention.

[0023] The method for preparing alumina particles according to the present invention has the advantages of simple operation, low energy consumption, simple equipment, and a green and clean preparation process, which effectively solves the pollution emission problem in the catalyst carrier preparation process. DETAILED DESCRIPTION

[0024] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0025] According to a first aspect of the present invention, a method for preparing aluminum oxide particles is provided, wherein the method comprises the following steps:

[0026] 1) mixing a chitosan polymer, an aluminum source, and optionally water to form a slurry;

[0027] 2) dropping the slurry into an acidic solution to undergo a cross-linking reaction to obtain solidified particles;

[0028] 3) calcining the solidified particles to obtain alumina particles.

[0029] According to the present invention, in step 1), the weight ratio of the chitosan polymer to the aluminum source calculated as aluminum element is 1:0.1-50, preferably 1:1-10, more preferably 1:1-5, more preferably 1:1.3-3, and even more preferably 1:1.5-3.

[0030] According to the present invention, preferably, the content of the slurry in terms of aluminum element is 1-25% by weight, preferably 2-10% by weight, more preferably 3-8% by weight, and further preferably 5-6% by weight.

[0031] According to the present invention, preferably, the aluminum source is pseudo-boehmite and / or aluminum sol.

[0032] According to the present invention, when the aluminum source is pseudo-boehmite, in order to prepare the slurry, the aluminum source, chitosan polymer and water can be mixed to prepare the slurry, and the amount of water used only needs to ensure that the aluminum content in the slurry is within the above range.

[0033] According to the present invention, preferably, the pseudo-boehmite has a mesh size of 80-800 meshes.

[0034] According to the present invention, preferably, the content of the aluminum sol in terms of aluminum element is 1-50 wt %, preferably 2-10 wt %, more preferably 3-8 wt %, and further preferably 5-6 wt %.

[0035] According to the present invention, preferably, the aluminum sol is aluminum oxide hydrogel and / or nano aluminum oxide sol.

[0036] Since the aluminum sol usually contains water, when the aluminum sol is mixed with the chitosan polymer to prepare a slurry, if the aluminum content in the slurry is within the above range, there is no need to add water. If it is not within the above range, water can be added to ensure that the aluminum content in the slurry is within the above range.

[0037] According to the present invention, preferably, the chitosan polymer is one or more of chitosan, carboxymethyl chitosan, hydroxyethyl chitosan, hydroxypropyl chitosan and carboxymethylated hydroxypropyl chitosan; more preferably, the chitosan polymer is one or more of chitosan, carboxymethyl chitosan, hydroxyethyl chitosan and hydroxypropyl chitosan; further preferably, the chitosan polymer is carboxymethyl chitosan.

[0038] According to the present invention, in step 1), the mixing temperature is not particularly limited, for example, it can be carried out at room temperature (5-45° C.), and the mixing time is not particularly limited, as long as a uniformly mixed slurry can be obtained.

[0039] According to the present invention, preferably, in step 2), the acidic solution is one or more of aqueous sulfuric acid, aqueous nitric acid, aqueous hydrochloric acid, aqueous acetic acid, aqueous oxalic acid and aqueous citric acid; more preferably, the acidic solution is aqueous acetic acid.

[0040] According to the present invention, preferably, the molar concentration of the acidic solution is above 0.1 mol / L; more preferably, the molar concentration of the acidic solution is 0.1-17.5 mol / L.

[0041] In a preferred embodiment of the present invention, the acidic solution is an aqueous solution of acetic acid with a concentration of 20-25% by weight.

[0042] According to the present invention, preferably, relative to 1 part by weight of the slurry B, the amount of the acidic solution is 0.1 parts by weight or more, preferably 1 part by weight or more, more preferably 2 parts by weight or more, more preferably 5 parts by weight or more, more preferably 10 parts by weight or more, and preferably 100 parts by weight or less, more preferably 50 parts by weight or less, more preferably 20 parts by weight or less.

[0043] According to the present invention, preferably, the conditions for the cross-linking reaction include: temperature of 5-45° C., and time of 0.5-5 hours; more preferably, the conditions for the cross-linking reaction include: temperature of 15-30° C., and time of 1-2 hours.

[0044] According to the present invention, after the cross-linking reaction is completed, the solidified particles can be separated from the reaction solvent. Preferably, the solidified particles are dried.

[0045] The separation can be carried out by a solid-liquid separation method commonly used in the art, for example, the solidified particles can be directly removed from the reaction solution or filtered to obtain solidified particles. In addition, the drying can be air-dried or oven-dried.

[0046] According to the present invention, preferably, in step 4), the calcination conditions include: temperature of 500-1200° C., time of 1-3 hours; more preferably, the calcination conditions include: temperature of 600-800° C., time of 1-2 hours.

[0047] According to a second aspect of the present invention, provided are aluminum oxide particles prepared by the method for preparing aluminum oxide particles of the present invention.

[0048] The method for preparing alumina particles according to the present invention has the advantages of simple operation, low energy consumption, simple equipment, and a green and clean preparation process, which effectively solves the pollution emission problem in the catalyst carrier preparation process.

[0049] The present invention will be described in detail below through examples, but the present invention is not limited to the following examples.

[0050] In the following examples, the average strength was measured using the Standard Test Method for Single Particle Crush Strength of Molded Catalysts and Catalyst Carriers (ASTM D4179-11(2017)), and the specific surface area and pore volume were measured using the gas adsorption BET method (GB / T 19587-2017).

[0051] Example 1

[0052] 1.2 g of carboxymethyl chitosan (purchased from Aladdin Biochemical Technology Co., Ltd., the same below) was added to 40 g of aluminum sol (specifically nano-alumina sol, purchased from Hangzhou Zhitai Purification Technology Co., Ltd., with an aluminum content of 5.3% by weight, the same below), stirred and mixed to form a slurry without a sense of graininess (the slurry has an aluminum content of 5.1% by weight), and then dripped into an acetic acid aqueous solution with a concentration of 25% by weight (relative to 1 part by weight of the slurry, the amount of the acetic acid aqueous solution is 2 parts by weight) to form composite gel particles, which were removed after reacting for 1 hour and dried naturally. The dried composite gel particles were placed in a muffle furnace, heated to 650°C for 0.5 hours and maintained for 1 hour to obtain alumina particles. Analysis of the product showed that the particle size was 2.2±0.2 mm, the average strength was 11.2 N / particle, and the specific surface area was 193.1 m 2 / g, pore volume 0.38cm 3 / g.

[0053] Example 2

[0054] Add 1.2g of carboxymethyl chitosan to 40g of aluminum sol, stir and mix to form a slurry without particle feeling, drop into 25% by weight acetic acid aqueous solution (relative to 1 weight part of slurry, the amount of acetic acid aqueous solution is 2 weight parts) to form composite gel particles, react for 1 hour, remove and dry naturally. The dried composite gel particles are placed in a muffle furnace, heated to 650℃ for 0.5h and maintained for 2h to obtain alumina particles. Analysis of the product shows: particle size 2.2±0.2mm, average strength 14.3N / particle, specific surface area 216.7m 2 / g, pore volume 0.42cm 3 / g.

[0055] Example 3

[0056] Add 1.2g of carboxymethyl chitosan to 40g of aluminum sol, stir and mix to form a slurry without particle feeling, drop into 25% by weight acetic acid aqueous solution (relative to 1 weight part of slurry, the amount of acetic acid aqueous solution is 2 weight parts) to form composite gel particles, react for 1 hour, remove and dry naturally. The dried composite gel particles are placed in a muffle furnace, heated to 650℃ for 0.5h and maintained for 3h to obtain alumina particles. Analysis of the product shows: particle size 2.2±0.2mm, average strength 24.3N / particle, specific surface area 204.0m 2 / g, pore volume 0.43cm 3 / g.

[0057] Example 4

[0058] Add 0.96g of carboxymethyl chitosan to 40g of aluminum sol, stir and mix to form a slurry without particle feeling, drop into 25% by weight acetic acid aqueous solution (relative to 1 weight part of slurry, the amount of acetic acid aqueous solution is 2 weight parts) to form composite gel particles, react for 1 hour, remove and dry naturally. The dried composite gel particles are placed in a muffle furnace, heated to 650℃ for 0.5h and maintained for 1h to obtain alumina particles. Analysis of the product shows: particle size 2.2±0.2mm, average strength 21.9N / particle, specific surface area 210.0m 2 / g, pore volume 0.42cm 3 / g.

[0059] Example 5

[0060] Add 6g of pseudo-boehmite and 1.6g of carboxymethyl chitosan to 40g of deionized water, stir and mix to form a slurry without particle feeling (the aluminum content of the slurry is 5.3% by weight), drop into an acetic acid aqueous solution with a concentration of 25% by weight (relative to 1 part by weight of the slurry, the amount of the acetic acid aqueous solution is 2 parts by weight) to form composite gel particles, react for 2 hours, and remove and dry naturally. The dried composite gel particles are placed in a muffle furnace, heated to 650℃ for 0.5 hours and maintained for 3 hours to obtain alumina particles. Analysis of the product shows: particle size 1.7±0.2mm, average strength 10.0N / particle, specific surface area 141.9m 2 / g, pore volume 0.15cm 3 / g.

[0061] Example 6

[0062] 8g of pseudo-boehmite and 1.6g of carboxymethyl chitosan were added to 40g of deionized water, stirred and mixed to form a slurry without particle feeling (the aluminum content of the slurry is 6.8% by weight), and then dropped into an acetic acid aqueous solution with a concentration of 25% by weight (relative to 1 part by weight of the slurry, the amount of the acetic acid aqueous solution is 2 parts by weight) to form composite gel particles. After reacting for 2 hours, the particles were fished out and dried naturally. The dried composite gel particles were placed in a muffle furnace, heated to 650°C for 0.5 hours and maintained for 3 hours to obtain alumina particles. Analysis of the product showed that the particle size was 1.7±0.2mm, the average strength was 14.7N / particle, and the specific surface area was 166.9m 2 / g, pore volume 0.17cm 3 / g.

[0063] Example 7

[0064] Add 10g of pseudo-boehmite and 1.6g of carboxymethyl chitosan to 40g of deionized water, stir and mix to form a slurry without particle feeling (the aluminum content of the slurry is 8.2% by weight), drop into a 25% by weight acetic acid aqueous solution (relative to 1 part by weight of the slurry, the amount of the acetic acid aqueous solution is 2 parts by weight) to form composite gel particles, react for 2 hours, and remove and dry naturally. The dried composite gel particles are placed in a muffle furnace, heated to 650℃ for 0.5 hours and maintained for 1 hour to obtain alumina particles. Analysis of the product shows: particle size 1.7±0.2mm, average strength 12.6N / particle, specific surface area 158.7m 2 / g, pore volume 0.17cm 3 / g.

[0065] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing aluminum oxide particles, characterized in that: The method comprises the following steps, 1) mixing a chitosan polymer, an aluminum source, and optionally water to form a slurry; 2) dropping the slurry into an acidic solution to undergo a cross-linking reaction to obtain solidified particles; 3) calcining the solidified particles to obtain alumina particles, Wherein, the weight ratio of the chitosan polymer to the aluminum source calculated as aluminum element is 1: 0.1-50， The content of the slurry in terms of aluminum element is 1-25% by weight. The acidic solution is one or more of a sulfuric acid aqueous solution, a nitric acid aqueous solution, a hydrochloric acid aqueous solution, an acetic acid aqueous solution, an oxalic acid aqueous solution and a citric acid aqueous solution. The chitosan polymer is carboxymethyl chitosan.

2. The method according to claim 1, wherein The weight ratio of the chitosan polymer to the aluminum source calculated as aluminum element is 1:1-10.

3. The method according to claim 2, wherein: The weight ratio of the chitosan polymer to the aluminum source calculated as aluminum element is 1:1-5.

4. The method according to claim 3, wherein: The weight ratio of the chitosan polymer to the aluminum source calculated as aluminum element is 1:1.3-3.

5. The method according to claim 4, wherein The weight ratio of the chitosan polymer to the aluminum source calculated as aluminum element is 1:1.5-3.

6. The method according to claim 1, wherein The content of the slurry in terms of aluminum element is 2-10% by weight.

7. The method according to claim 6, wherein: The content of the slurry in terms of aluminum element is 3-8% by weight.

8. The method according to claim 7, wherein: The content of the slurry in terms of aluminum element is 5-6% by weight.

9. The method according to any one of claims 1 to 8, wherein: The aluminum source is pseudo-boehmite and / or aluminum sol.

10. The method according to claim 9, wherein: The mesh number of the pseudo-boehmite is 80-800 meshes.

11. The method according to claim 9, wherein The aluminum sol has an aluminum content of 1-50% by weight.

12. The method according to claim 11, wherein The aluminum sol has an aluminum content of 2-10% by weight.

13. The method according to claim 12, wherein: The aluminum sol has an aluminum content of 3-8% by weight.

14. The method according to claim 13, wherein The aluminum sol has an aluminum content of 5-6% by weight.

15. The method according to claim 9, wherein The aluminum sol is aluminum oxide hydrogel and / or nano aluminum oxide sol.

16. The method according to any one of claims 1 to 8, wherein: The molar concentration of the acidic solution is greater than 0.1 mol / L.

17. The method according to claim 16, wherein The molar concentration of the acidic solution is 0.1-17.5 mol / L.

18. The method according to any one of claims 1 to 8, wherein: The amount of the acidic solution is 1-5 parts by weight relative to 1 part by weight of the slurry.

19. The method according to any one of claims 1 to 8, wherein: The cross-linking reaction conditions include: temperature of 5-45° C. and time of 0.5-5 hours.

20. The method according to any one of claims 1 to 8, wherein: The calcination conditions include: a temperature of 500-1200° C. and a time of 1-3 hours.

21. The method according to claim 20, wherein The calcination conditions include: a temperature of 600-800° C. and a time of 1-2 hours.

22. Alumina particles prepared by the method for preparing alumina particles according to any one of claims 1 to 21.