A method for producing alumina and alumina

Abstract

The present application relates to a preparation method of alumina and the alumina, the preparation method comprises the following steps: (1) reacting metal aluminum with fatty alcohol to obtain a fatty alcohol solution of alkoxy aluminum, adding water to the fatty alcohol solution of alkoxy aluminum to hydrolyze the alkoxy aluminum, and obtaining a first boehmite slurry containing fatty alcohol; (2) adjusting the molar ratio of aluminum to fatty alcohol in the first boehmite slurry to a target molar ratio, and obtaining a second boehmite slurry, the target molar ratio is 1:(1.5-4.0); (3) adding a non-ionic emulsifier to the second boehmite slurry, and then stirring, drying and calcining. The alumina obtained by the preparation method has high specific surface area, large pore volume and large most probable pore diameter; the specific surface area is greater than or equal to 250.0 m 2 .g ‑1 , the pore volume is greater than or equal to 0.750 cm 3 .g ‑1 , and the most probable pore diameter is greater than or equal to 10.0 nm; the aging step does not need a long time, the recovered fatty alcohol obtained by drying can be reused as a raw material for synthesizing alkoxy aluminum, the process is simple and suitable for continuous production.

Description

Technical Field

[0001] This invention relates to the field of alumina technology, specifically to a method for preparing alumina and alumina itself. Background Technology

[0002] Alumina, as a catalyst support, offers numerous loading sites for active centers if it possesses a high specific surface area. Furthermore, its large pore volume and diameter facilitate rapid diffusion of reactant and product molecules, improving the utilization rate of active sites and inhibiting surface coking. Clearly, alumina materials that combine high specific surface area and large pore size can fulfill all these advantages as catalyst supports and promote advancements in catalyst technology in fields such as catalytic cracking, reforming, and hydrogenation.

[0003] The alkoxyaluminum hydrolysis method uses metallic aluminum and fatty alcohols as raw materials. Besides yielding high-purity alumina, it also allows for the control of physicochemical properties such as grain size, specific surface area, and pore structure by adjusting the technical parameters of the preparation process. However, the aforementioned research revealed a negative correlation between the specific surface area and pore volume of alumina, making it difficult to achieve both simultaneously at high values.

[0004] CN201110138190.X discloses a macroporous alumina and its preparation method. This alumina also possesses a high specific surface area (150-450 m²). 2 .g -1 ) and macropore volume (1.1-3.5 cm) 3 .g -1 The preparation of this product employs a two-stage aging method. The first stage involves adjusting the pH of the precursor, pseudoboehmite slurry. The second stage involves adding a certain amount of fatty alcohol after the first stage. The resulting slurry is then subjected to alcohol removal, drying, and calcination to obtain the final product. However, this method is cumbersome, with the aging process taking up to 24 hours. Furthermore, the addition of alkali metal hydroxides or alkali metal alkoxides during the pH adjustment step in the first stage can negatively impact the purity of the product.

[0005] CN201110408487.3 proposes a method with a large pore volume (0.70-1.55 cm³). 3 .g -1 High specific surface area (220-480m²) 2 .g -1Preparation method of activated alumina. In this method, sodium aluminate is first dropped into nitric acid solution to form a sol with a certain pH value and then aged. After filtration and washing steps, it is mixed with n-butanol in a certain proportion and then co-distilled to obtain a dry precursor. Finally, the target product is obtained through drying and calcination, and the n-butanol vapor can be recycled. However, this method has cumbersome steps, and the aging step takes up to 10 hours at most. The whole process is not convenient for continuous production, and the alumina prepared by the inorganic method has the problem of low purity.

[0006] How to prepare alumina with high specific surface area, large pore volume and large most probable pore diameter by a simple, effective method that does not introduce main impurities and is conducive to continuous industrialization is a technical problem to be solved urgently at present. Summary of the Invention

[0007] The object of the present invention is to provide a preparation method of alumina and alumina, so as to prepare alumina with high specific surface area, large pore volume and large most probable pore diameter at the same time.

[0008] In the first aspect, the present invention relates to a preparation method of alumina, which includes the following steps: (1) reacting metallic aluminum with fatty alcohol to obtain a fatty alcohol solution of alkoxyaluminum, and adding water to the fatty alcohol solution of alkoxyaluminum to hydrolyze the alkoxyaluminum, obtaining a first pseudo-boehmite slurry containing fatty alcohol; (2) adjusting the molar ratio of aluminum to fatty alcohol in the first pseudo-boehmite slurry to a target molar ratio to obtain a second pseudo-boehmite slurry, and the target molar ratio is 1:(1.5 - 4.0); (3) adding a non-ionic emulsifier to the second pseudo-boehmite slurry, and then stirring, drying and calcining.

[0009] Optionally, in step (1), the fatty alcohol is selected from one or more of C4 - C6 fatty alcohols, and the fatty alcohol is a monohydric alcohol.

[0010] Optionally, in step (1), the feeding molar ratio of metallic aluminum to the fatty alcohol is 1:(3.2 - 4.0).

[0011] Optionally, in step (1), the reaction conditions include: first heating to 130 - 160 °C to initiate the reaction, and then reacting at 130 - 160 °C for 40 - 100 min.

[0012] Optionally, in step (1), the hydrolysis conditions include: temperature is 90 - 110 °C, and time is 30 - 60 min.

[0013] Optionally, in step (2), the target molar ratio is 1:R, 1.5 < R < 4, and R is an integer.

[0014] Optionally, in step (2), the adjustment includes: adding or separating an amount of the fatty alcohol corresponding to the difference between the molar ratio of metallic aluminum to the fatty alcohol in step (1) and the target molar ratio in step (2) into the first pseudoboehmite slurry.

[0015] Optionally, in step (3), the nonionic emulsifier is selected from one or more of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, polyoxyethylene alkylamine and polyoxyethylene alkylolamide.

[0016] Optionally, in step (3), the mass percentage of the added nonionic emulsifier is 1-10 wt%, based on the mass of the fatty alcohol in the second pseudoboehmite slurry.

[0017] Secondly, the present invention relates to an alumina prepared by the above-described method, wherein the alumina has a specific surface area ≥250.0 m². 2 .g -1 Hole volume ≥ 0.750 cm³ 3 .g -1 And the most probable pore size is ≥10.0nm.

[0018] Beneficial effects:

[0019] (1) The alumina prepared by the method of the present invention simultaneously possesses high specific surface area, large pore volume, and large most probable pore size; specific surface area ≥ 250.0 m² 2 .g -1 Hole volume ≥ 0.750 cm³ 3 .g -1 The most probable pore size is ≥10.0 nm;

[0020] (2) The preparation method of the present invention does not require a long aging step, and the fatty alcohol obtained by drying and recovery can be reused as a raw material for the synthesis of alkoxy aluminum. The process is simple and suitable for continuous production. Detailed Implementation

[0021] The present application will be further described in detail below through embodiments. Through these descriptions, the features and advantages of the present application will become clearer and more apparent.

[0022] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0023] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0024] In a first aspect, the present invention relates to a method for preparing alumina, comprising the following steps: (1) reacting metallic aluminum with a fatty alcohol to obtain an alkoxy aluminum fatty alcohol solution, adding water to the alkoxy aluminum fatty alcohol solution to hydrolyze the alkoxy aluminum to obtain a first pseudoboehmite slurry containing fatty alcohol; (2) adjusting the molar ratio of aluminum to fatty alcohol in the first pseudoboehmite slurry to a target molar ratio to obtain a second pseudoboehmite slurry, wherein the target molar ratio is 1:(1.5-4.0); (3) adding a nonionic emulsifier to the second pseudoboehmite slurry, and then stirring, drying and calcining.

[0025] It should be noted that in the preparation method of the present invention, after the alkoxyaluminum is completely hydrolyzed, the aluminum metal initially fed is completely converted from alkoxyaluminum to boehmite, and the alkoxy groups in the alkoxyaluminum are then completely converted back to fatty alcohols. Therefore, in the first boehmite slurry containing fatty alcohols obtained after hydrolysis in step (1), the molar ratio of aluminum to fatty alcohols is equal to the molar ratio of aluminum metal to fatty alcohols at the initial feeding stage. In step (2), the molar ratio of aluminum to fatty alcohols in the first boehmite slurry is adjusted to the target molar ratio, and the amount of aluminum in the molar ratio of aluminum to fatty alcohols refers to the molar amount of aluminum metal at the initial feeding stage.

[0026] It should be noted that in the preparation method of this invention, the molar ratio of aluminum to fatty alcohol in the second pseudo-boehmite slurry needs to be controlled within the target molar ratio range before adding the nonionic emulsifier. Only under such a system can subsequent stirring, drying, and calcination yield alumina with high specific surface area, large pore volume, and large most probable pore size. The alumina product finally obtained by the preparation method of this invention simultaneously satisfies: specific surface area ≥ 250.0 m². 2 .g -1 Hole volume ≥ 0.750 cm³ 3 .g -1 The most probable pore size is ≥10.0 nm.

[0027] According to one embodiment of the present invention, in step (1), the aluminum metal is selected from at least one of aluminum blocks, aluminum briquettes, aluminum foil, aluminum shavings and aluminum wire.

[0028] According to one embodiment of the present invention, in step (1), the fatty alcohol is selected from one or more of C4 to C6 fatty alcohols, and the fatty alcohol is a monohydric alcohol, preferably n-butanol, n-pentanol or n-hexanol.

[0029] According to one embodiment of the present invention, in step (1), the molar ratio of the aluminum metal to the fatty alcohol is 1:(3.2-4.0).

[0030] It should be noted that the fatty alcohol is a monohydric alcohol, and the molar ratio of metallic aluminum to the fatty alcohol during the reaction is 1:3. Therefore, when the molar ratio of metallic aluminum to the fatty alcohol in the feeding is within the above range, the metallic aluminum can completely react and be entirely converted into aluminum alkoxide. Preferably, the molar ratio of metallic aluminum to the fatty alcohol in the feeding is 1:(3.6 - 4.0).

[0031] According to an embodiment of the present invention, in step (1), the reaction conditions include: first heating up to 130 - 160 °C to initiate the reaction, and then reacting at 130 - 160 °C for 40 - 100 min.

[0032] It should be noted that the temperature for initiating the reaction and the temperature for the subsequent reaction can be different. The temperature for initiating the reaction can be 140 °C, and the temperature for the reaction can be 145 °C.

[0033] According to an embodiment of the present invention, in step (1), the hydrolysis conditions include: the temperature is 90 - 110 °C, and the time is 30 - 60 min.

[0034] It should be noted that the amount of water added is not less than the amount of water required for the complete hydrolysis of the aluminum alkoxide. The mass of the water is 18 - 30 times, preferably 18 - 22 times, the mass of the metallic aluminum in step (1). In the above reaction system, adding water according to the above mass ratio can completely hydrolyze the aluminum alkoxide, and the dispersion degree of boehmite in the system is controlled within the preferred range.

[0035] According to an embodiment of the present invention, in step (2), the target molar ratio is 1:R, 1.5 < R < 4, and R is an integer.

[0036] According to an embodiment of the present invention, in step (2), the adjustment includes: according to the difference between the molar ratio of metallic aluminum to the fatty alcohol in step (1) and the target molar ratio in step (2), adding to or separating from the first boehmite slurry the amount of the fatty alcohol corresponding to the difference.

[0037] It should be noted that after the complete hydrolysis of alkoxyaluminum in step (1), the molar ratio of aluminum to alcohol in the slurry system is the same as the molar ratio of raw material aluminum to alcohol in the system before the start of the synthesis reaction. Then, by separating or adding the fatty alcohol, the molar ratio of aluminum to alcohol in the slurry system is adjusted to 1:(1.5-4.0), more preferably 1:(1.5-3.0). For example, if the molar ratio of raw material aluminum to alcohol is 1:1, the target molar ratio is 1:3, and the initial molar amount of aluminum is known, for example, n, then 2n amounts of fatty alcohol need to be added to the first pseudoboehmite slurry to adjust the molar ratio of aluminum to fatty alcohol to the target molar ratio. Conversely, if the molar ratio of raw material aluminum to alcohol is 1:5, the target molar ratio is 1:3, and the initial molar amount of aluminum is known, for example, n, then 2n amounts of fatty alcohol need to be separated from the first pseudoboehmite slurry to adjust the molar ratio of aluminum to fatty alcohol to the target molar ratio.

[0038] According to one embodiment of the present invention, the separation includes: pouring or aspirating the amount of supernatant corresponding to the difference in the first pseudo-boehmite slurry, or separating the supernatant through a separating funnel.

[0039] It should be noted that the first pseudoboehmite slurry separates into an upper clear liquid (fatty alcohol) and a lower slurry, and the separation method is not limited to the method described above. Any method capable of separating the upper clear liquid, i.e., fatty alcohol, such as phase separation methods, can be used.

[0040] According to one embodiment of the present invention, in step (3), the nonionic emulsifier is selected from one or more of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, polyoxyethylene alkylamine and polyoxyethylene alkylolamide.

[0041] It should be noted that in the preparation method of the present invention, the presence of nonionic emulsifier enables fatty alcohol to be well dispersed in the slurry system. By controlling the molar ratio of aluminum to fatty alcohol, and selecting the fatty alcohol and nonionic emulsifier as described above, and following the steps (1)-(3) of the preparation method of the present invention, aluminum oxide with high specific surface area, large pore volume and large most probable pore size can be prepared.

[0042] According to one embodiment of the present invention, in step (3), the added nonionic emulsifier accounts for 1-10 wt% by mass, based on the mass of the fatty alcohol in the second pseudoboehmite slurry. Preferably, the added nonionic emulsifier accounts for 1-5 wt% by mass (based on the same standard as above).

[0043] It should be noted that the combination of the fatty alcohol and the nonionic emulsifier within the preferred range can further improve the dispersibility of the fatty alcohol in the slurry system, thereby further improving the performance parameters of the prepared alumina.

[0044] According to one embodiment of the present invention, in step (3), the stirring conditions include: a stirring rate of 300-800 rpm and a stirring time of 30-90 min. Preferably, the stirring rate is 400-500 rpm and the stirring time is 40-60 min.

[0045] In a second aspect, the present invention relates to an alumina prepared by the above-described preparation method, wherein the alumina has a specific surface area ≥250.0 m2.g-1, a pore volume ≥0.750 cm3.g-1, and a most probable pore diameter ≥10.0 nm.

[0046] The present invention will be further described in detail below through examples. All reagents used in the following examples are commercially available reagents.

[0047] Example 1

[0048] 9 g (0.33 mol) of aluminum shavings (99.996% by mass purity) and 151 mL (1.2 mol) of n-hexanol were added to a reaction vessel as reactants. The temperature was raised to 140 °C to initiate the reaction, and the temperature was controlled at 145 °C for 60 minutes to allow the aluminum shavings to react completely to form a n-hexanol solution of aluminum hexoxy. 180 mL (10 mol) of deionized water was added to hydrolyze the aluminum hexoxy at 90 °C for 40 minutes until hydrolysis was complete, yielding an aluminum hydroxide slurry containing n-hexanol, with an aluminum to alcohol molar ratio of 1:3.6.

[0049] The supernatant was separated using a separatory funnel to obtain 20.43 g (0.2 mol) of n-hexanol. At this point, the molar ratio of aluminum to alcohol in the slurry system was 1:3. Then, 5.11 g (5% of the remaining alcohol mass in the system) of AEO-3 reagent (a type of fatty alcohol polyoxyethylene ether) was added. The slurry was then stirred at 500 rpm for 60 min. The stirred slurry was dried at 120 °C for 12 h to obtain aluminum hydroxide. The aluminum hydroxide was then calcined at 550 °C for 6 h to obtain alumina product. The specific surface area, pore volume, and most probable pore size of the alumina product are shown in Table 1.

[0050] Example 2

[0051] The alumina product was obtained according to the method of Example 1, except that the amount of AEO-3 reagent added was 1.02 g (1% of the mass of the remaining alcohol in the system). The specific surface area, pore volume, and most probable pore size of the alumina product are shown in Table 1.

[0052] Example 3

[0053] 9 g (0.33 mol) of aluminum scrap (99.996% by mass purity) and 129 mL (1.2 mol) of n-pentanol were added to a reaction vessel as reactants. The temperature was raised to 130 °C to initiate the reaction, and the temperature was controlled at 136 °C for 60 minutes to allow the aluminum scrap to react completely to form a n-pentanol solution of aluminum pentoxy. 180 mL (10 mol) of deionized water was added to hydrolyze the aluminum pentoxy at 90 °C for 40 minutes until hydrolysis was complete, yielding an aluminum hydroxide slurry containing n-pentanol, with an aluminum to alcohol molar ratio of 1:3.6.

[0054] 17.63 g (0.2 mol) of n-pentanol was separated, bringing the aluminum-to-alcohol molar ratio in the slurry system to 1:3. Then, 4.41 g (5% of the remaining alcohol mass) of AEO-3 reagent was added, and the slurry was stirred at 500 rpm for 60 min. The stirred slurry was dried at 120 °C for 12 h to obtain aluminum hydroxide, which was then calcined at 550 °C for 6 h to obtain alumina. The specific surface area, pore volume, and most probable pore size of this alumina product are shown in Table 1.

[0055] Example 4

[0056] The alumina product was obtained according to the method in Example 1, except that 72.02 g (0.705 mol) of n-hexanol was separated after the hydrolysis of aluminum alkoxy. At this point, the molar ratio of aluminum to alcohol in the slurry system was 1:1.5, and then 2.55 g (5% of the remaining alcohol mass in the system) of AEO-3 reagent was added. The specific surface area, pore volume, and most probable pore size of the alumina product are shown in Table 1.

[0057] Example 5

[0058] The alumina product was obtained according to the method of Example 1, except that 5.11 g (5% of the mass of the remaining alcohol in the system) of LAE-4 reagent (a type of fatty acid polyoxyethylene ester) was added after the alcohol was separated. The specific surface area, pore volume and most probable pore size of the alumina product are shown in Table 1.

[0059] Comparative Example 1

[0060] 9 g (0.33 mol) of aluminum shavings (99.996% by mass purity) and 151 mL (1.2 mol) of n-hexanol were added to a reaction vessel as reactants. The temperature was raised to 140 °C to initiate the reaction, and the temperature was controlled at 145 °C for 60 minutes to allow the aluminum shavings to react completely to form a n-hexanol solution of aluminum hexoxy. 180 mL (10 mol) of deionized water was added to hydrolyze the aluminum hexoxy at 90 °C for 40 minutes until hydrolysis was complete, yielding an aluminum hydroxide slurry containing n-hexanol, with an aluminum to alcohol molar ratio of 1:3.6.

[0061] All alcohol phases were separated, and at this point, apart from trace amounts of alcohol entrained in the slurry, no other n-hexanol was present in the system. The slurry was stirred at 500 rpm for 60 min. The stirred slurry was dried at 120 °C for 12 h to obtain aluminum hydroxide, which was then calcined at 550 °C for 6 h to obtain alumina product. The specific surface area, pore volume, and most probable pore size of this alumina product are shown in Table 1.

[0062] Comparative Example 2

[0063] The alumina product was obtained using the method of Comparative Example 1, except that after separating all the alcohol phases, 1.02 g of AEO-3 reagent (same as in Example 2) was added. The specific surface area, pore volume, and most probable pore size of the alumina product are shown in Table 1.

[0064] Comparative Example 3

[0065] The alumina product was obtained according to the method of Example 1, except that the molar ratio of aluminum to alcohol was 1:2 after separating the alcohol phase, and no emulsifier was added. The specific surface area, pore volume, and most probable pore size of the alumina product are shown in Table 1.

[0066] Test Example 1

[0067] The specific surface area, pore volume, and most probable pore size of the alumina prepared in Examples 1-5 and Comparative Examples 1-3 were measured and analyzed by the BET method. The results are detailed in Table 1 below.

[0068] Table 1

[0069]

[0070] The present application has been described above with reference to preferred embodiments; however, these embodiments are merely exemplary and illustrative. Various substitutions and modifications can be made to the present application based on these embodiments, all of which fall within the protection scope of the present application.

Claims

1. A method for preparing alumina, characterized in that, It includes the following steps: (1) React metallic aluminum with a fatty alcohol to obtain a fatty alcohol solution of aluminum alkoxide, add water to the fatty alcohol solution of aluminum alkoxide to hydrolyze the aluminum alkoxide, and obtain a first pseudoboehmite slurry containing a fatty alcohol, wherein the fatty alcohol is a monohydric alcohol; (2) Adjust the molar ratio of aluminum to the fatty alcohol in the first pseudoboehmite slurry to a target molar ratio to obtain a second pseudoboehmite slurry, and the target molar ratio is 1:(1.5 - 4.0); (3) Add a non-ionic emulsifier to the second pseudoboehmite slurry, and then stir, dry and calcine.

2. The preparation method according to claim 1, characterized in that, In step (1), the fatty alcohol is selected from one or more of fatty alcohols with C4 - C6; 3. The preparation method according to claim 2, characterized in that, In step (1), the feed molar ratio of the metallic aluminum to the fatty alcohol is 1:(3.2 - 4.0); 4. The preparation method according to claim 3, characterized in that, In step (1), the reaction conditions include: first raise the temperature to 130 - 160 °C to initiate the reaction, and then react at 130 - 160 °C for 40 - 100 min; 5. The preparation method according to claim 4, characterized in that, In step (1), the hydrolysis conditions include: the temperature is 90 - 110 °C and the time is 30 - 60 min; 6. The preparation method according to claim 5, characterized in that, In step (2), the target molar ratio is 1:R, 1.5 < R < 4, and R is an integer; 7. The preparation method according to claim 1 or 6, characterized in that, In step (2), the adjustment includes: According to the difference between the feed molar ratio of the metallic aluminum to the fatty alcohol in step (1) and the target molar ratio in step (2), add or separate the amount of the fatty alcohol corresponding to the difference from the first pseudoboehmite slurry; 8. The preparation method according to claim 7, characterized in that, In step (3), the non-ionic emulsifier is selected from one or more of fatty alcohol polyoxyethylene ethers, alkylphenol polyoxyethylene ethers, fatty acid polyoxyethylene esters, polyoxyethylene alkylamines, and polyoxyethylene alkyl alcohol amides; 9. The preparation method according to claim 8, characterized in that, In step (3), the mass ratio of the added non-ionic emulsifier is 1 - 10 wt%, based on the mass of the fatty alcohol in the second pseudoboehmite slurry.

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