Alumina powder and preparation process thereof

Abstract

The invention relates to the technical field of alumina powder, in particular to alumina powder and a preparation process thereof. The method comprises the following steps: (a) preparing an aluminum source solution; (b) preparing an alkali solution; (c) preparing an aluminum oxide precursor; step (d) aging; step (e) drying; and (f) calcining to obtain uniformly dispersed aluminum oxide powder. The average grain size of the prepared alumina powder product is 35.9-40.1 nm, the specific surface area is 435-667 m < 2 > / g, the pore volume is 0.021-0.103 cm < 3 > / g, and the most probable pore size is 3.7-3.8 nm. The average grain size is small, the product particles are uniform, the specific surface area is large, the stability is good, the cost is low, the process is simple, and large-scale production operation is easy.

Description

Technical Field

[0001] The present invention relates to the technical field of alumina powder, and particularly relates to an alumina powder and a preparation process thereof. Background Art

[0002] Alumina is a white substance widely distributed in nature, with many excellent properties such as high melting point, good hardness, high activity, and strong corrosion resistance. It can be divided into two categories: hydrated alumina and anhydrous alumina. Among them, the variety of anhydrous alumina variants is determined by the different calcination temperatures of the precursor, and it can be divided into α-Al 2 O 3 、γ-Al 2 O 3 、η-Al 2 O 3 、δ-Al 2 O 3 、θ-Al 2 O 3 、χ-Al 2 O 3 、κ-Al 2 O 3 and various other variants such as amorphous alumina. When the calcination temperature is higher than 1200 °C, α-Al 2 O 3 is formed. α-Al 2 O 3 has no moisture inside, has high hardness, and is the most stable variant. Alumina has many crystal types, and there are significant differences in properties between different variants, which determines their roles in various fields.

[0003] Alumina is widely used in many fields such as adsorption, catalysis, ceramics, thermal conductive materials, and composite materials. The currently reported preparation methods of alumina can be divided into three categories: liquid phase method, solid phase method, and gas phase method. Specifically, the liquid phase method includes precipitation method, sol-gel method, hydrothermal method, and solvothermal method. These methods have the advantages of controllable chemical composition, good surface activity of the prepared particles, and excellent morphology of the products. The solid phase method includes combustion method, grinding method, and thermal decomposition method. The preparation process is simple, the yield of the obtained product is high, the output is large, the environmental pollution is small, and the industrial production cost is low. However, the obtained product is prone to agglomeration and the particle size is difficult to control. The gas phase method is chemical vapor deposition method. This method requires a high cost, is prone to sintering at low temperatures, has a low yield, and it is difficult to collect the powder, making it difficult to achieve industrial production. Summary of the Invention

[0004] In view of the problems in the background art, the present invention provides an alumina powder and a preparation process thereof, with a simple process and an increased specific surface area of the obtained product.

[0005] It is achieved through the following technical solutions:

[0006] A preparation process of alumina powder, comprising the following steps:

[0007] Step (a) Prepare an aluminum source solution: Accurately weigh a certain mass of hydrated aluminum nitrate and hydrated aluminum sulfate, add them to deionized water, and dissolve them under stirring to prepare a mixed aluminum source solution;

[0008] Step (b) Prepare an alkali solution: Weigh a certain amount of sodium hydroxide and add it to deionized water to prepare a sodium hydroxide solution;

[0009] Step (c) Prepare an alumina precursor: Under stirring with a collecting heat type constant temperature magnetic stirrer for the aluminum source solution, add a dispersant, and then slowly dropwise add the sodium hydroxide solution to it at 50°C. During this process, white flocculants will be generated. After reacting for 6 - 8 hours, measure its pH value. When it is greater than 9, stop the reaction to obtain a solid-liquid mixture;

[0010] Step (d) Aging: Let the solid-liquid mixture stand for aging for 24 hours, then perform vacuum filtration and washing to obtain a white precipitate;

[0011] Step (e) Drying: Place the white precipitate in a blast drying oven and dry it at 80°C for 12 hours;

[0012] Step (f) Calcination: Place the dried precipitate in a muffle furnace and calcine it at 500°C for 2 - 3 hours, then raise the temperature to 700°C and calcine it for 4 - 5 hours, and finally calcine it at 1100°C for 1 - 2 hours. After the temperature drops to room temperature, perform sand grinding to obtain a uniformly dispersed alumina powder.

[0013] Preferably, the concentration of the aluminum source solution prepared in step (a) is 0.2mol / L, 0.4mol / L, 0.6mol / L, 0.8mol / L.

[0014] Preferably, the concentration of the sodium hydroxide solution prepared in step (b) is 2mol / L.

[0015] Preferably, the dispersant in step (c) is selected from one or more of sodium laurate, polyethylene glycol 200, polyethylene glycol 400, sodium dodecylbenzenesulfonate, and sodium stearate.

[0016] Preferably, in step (d), the filtration and washing operation is to select a 60mm Buchner funnel, cut a filter paper to make it smaller than the Buchner funnel but able to cover all pores, drip deionized water to moisten the filter paper, open the air extraction valve to make the filter paper and the funnel tightly connected, slowly pour the solid-liquid mixture into the center of the Buchner funnel, and after filtration, wash it three times with ammonium chloride and deionized water respectively.

[0017] Preferably, the sanding operation in step (f) is to add the calcined alumina into a TYEE horizontal sand mill, set the rotation speed at 2500 r / min, and grind for 0.5 - 1 hour.

[0018] Preferably, the particle size of the prepared alumina powder is ≤200 nm.

[0019] An alumina powder, characterized in that it is obtained by the above method.

[0020] Compared with the existing technology, the present invention has the following technical advantages:

[0021] In the present invention, aluminum nitrate and aluminum sulfate are compounded in proportion as the aluminum source. The anions have large activity and high valence electron numbers, are more likely to precipitate, have better dispersibility, are not easily aggregated together, and the obtained product has high quality. The average grain size of the product is 35.9 - 40.1 nm, the specific surface area is 435 - 667 m 2 / g, the pore volume is 0.021 - 0.103 cm 3 / g, and the most probable pore diameter is 3.7 - 3.8 nm. Different reaction times will affect the morphology and particle size of the product. The powder prepared by reacting for 4 hours has high sphericity and good dispersibility. As the reaction time increases, some particles will stack up and the dispersibility becomes worse. At the same time, for the product prepared with an aluminum source concentration of 0.2 mol / L, the specific surface area is 667 m 2 / g, for the product prepared with 0.4 mol / L, the specific surface area is 612 m 2 / g, for the product prepared with 0.6 mol / L, the specific surface area is 596 m 2 / g, for the product prepared with 0.8 mol / L, the specific surface area is 435 m 2 / g. As the aluminum source concentration increases, the specific surface area of the product decreases significantly. The product has the best performance when the aluminum source concentration is 0.2 mol / L and the reaction time is 4 hours. Specific Embodiments

[0022] The embodiments of the technical solutions of the present invention will be described in detail below in conjunction with the examples. The following examples are only used to illustrate the technical solutions of the present invention more clearly, and therefore are only examples and cannot be used to limit the protection scope of the present invention.

[0023] It should be noted that the experimental methods used in the implementation examples are all conventional methods unless otherwise specified; the materials, reagents, etc. used, unless otherwise specified, can all be obtained from commercial channels.

[0024] In the present invention, unless otherwise specified, the numerical range "a to b" represents an abbreviated representation of any real number combination between a and b, where both a and b are real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" are fully listed herein, and "0 to 5" is only an abbreviated representation of these numerical combinations.

[0025] In the present invention, if there is no special instruction, all the embodiments and preferred embodiments mentioned herein can be combined with each other to form a new technical solution.

[0026] In the present invention, if there is no special instruction, all the steps mentioned herein can be carried out in sequence or randomly, but preferably in sequence; for example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out in sequence, or can also include steps (b) and (a) carried out in sequence; for example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b) and (c), or can also include steps (a), (c) and (b), or can also include steps (c), (a) and (b), etc.

[0027] In the present invention, if there is no special instruction, the specific numerical values and specific substances in the embodiments of the present invention can be combined with other features in the description part of the present invention; for example, if the specification mentions that the reaction temperature is 10 to 100 °C, and the reaction temperature mentioned in the embodiment is 20 °C, then it can be considered that the present invention has specifically disclosed the range of 10 to 20 °C, or the range of 20 to 100 °C, and this range can be combined with other features in the description part to form a new technical solution.

[0028] Example 1:

[0029] Accurately weigh 112 g of aluminum nitrate hydrate and 133 g of aluminum sulfate hydrate, add them to 1 L of deionized water, and dissolve them under stirring to prepare a mixed aluminum source solution with a concentration of 0.2 mol / L;

[0030] Weigh 80 g of sodium hydroxide and add it to 1 L of deionized water to prepare a sodium hydroxide solution with a concentration of 2 mol / L;

[0031] Under stirring with a heating mantle magnetic stirrer, add sodium laurate to the aluminum source solution, and then slowly drop the sodium hydroxide solution into it at 50 °C. During this process, white flocculates will be produced. After reacting for 6 hours, measure its pH value. When the pH value is greater than 9, stop the reaction to obtain a solid-liquid mixture;

[0032] After allowing the solid-liquid mixture to stand and age for 24 hours, select a Buchner funnel with a diameter of 60 mm under reduced pressure. Trim the filter paper to be smaller than the Buchner funnel but cover all the pores, and add deionized water to moisten the filter paper. Open the air extraction valve to tightly connect the filter paper funnel. Slowly pour the solid-liquid mixture into the center of the Buchner funnel. After filtration, wash it three times with ammonium chloride and deionized water respectively to obtain a white precipitate.

[0033] Place the white precipitate in a blast drying oven and dry it at 80 °C for 12 hours.

[0034] Place the dried precipitate in a muffle furnace and calcine it at 500 °C for 2 hours, then raise the temperature to 700 °C and calcine it for 4 hours, and finally calcine it at 1100 °C for 1 hour. After the temperature drops to room temperature, add the calcined alumina to a TYEE horizontal sand mill, set the rotation speed to 2500 r / min, and grind for 0.5 hours to obtain uniformly dispersed alumina powder.

[0035] Example 2:

[0036] Accurately weigh 112 g of hydrated aluminum nitrate and 133 g of hydrated aluminum sulfate, add them to 1 L of deionized water, and dissolve them under stirring to prepare a mixed aluminum source solution with a concentration of 0.2 mol / L.

[0037] Weigh 80 g of sodium hydroxide and add it to 1 L of deionized water to prepare a sodium hydroxide solution with a concentration of 2 mol / L.

[0038] Under stirring with a heating mantle type constant temperature magnetic stirrer, add sodium laurate, polyethylene glycol 200, polyethylene glycol 400, sodium dodecylbenzenesulfonate, and sodium stearate to the aluminum source solution. Then, slowly add the sodium hydroxide solution dropwise to it at 50 °C. White flocculates will be produced during this process. After reacting for 7 hours, measure the pH value. When it is greater than 9, stop the reaction to obtain a solid-liquid mixture.

[0039] After allowing the solid-liquid mixture to stand and age for 24 hours, select a Buchner funnel with a diameter of 60 mm under reduced pressure. Trim the filter paper to be smaller than the Buchner funnel but cover all the pores, and add deionized water to moisten the filter paper. Open the air extraction valve to tightly connect the filter paper funnel. Slowly pour the solid-liquid mixture into the center of the Buchner funnel. After filtration, wash it three times with ammonium chloride and deionized water respectively to obtain a white precipitate.

[0040] Place the white precipitate in a blast drying oven and dry it at 80 °C for 12 hours.

[0041] The dried precipitate was placed in a muffle furnace and calcined at 500 °C for 2 hours, then the temperature was raised to 700 °C and calcined for 4 hours, and finally calcined at 1100 °C for 1 hour. After the temperature dropped to room temperature, the calcined alumina was added to a TYEE horizontal sand mill, the rotation speed was set at 2500 r / min, and it was ground for 0.5 hours to obtain uniformly dispersed alumina powder.

[0042] Example 3:

[0043] Accurately weigh 112 g of aluminum nitrate hydrate and 133 g of aluminum sulfate hydrate, add them to 1 L of deionized water, and dissolve them under stirring to prepare a mixed aluminum source solution with a concentration of 0.2 mol / L;

[0044] Weigh 80 g of sodium hydroxide and add it to 1 L of deionized water to prepare a sodium hydroxide solution with a concentration of 2 mol / L;

[0045] Under stirring with a heating magnetic stirrer, sodium laurate was added to the aluminum source solution, and then the sodium hydroxide solution was slowly added dropwise to it at 50 °C. During this process, white flocculates would be produced. After reacting for 8 hours, the reaction was stopped when the measured pH value was greater than 9 to obtain a solid-liquid mixture;

[0046] The solid-liquid mixture was allowed to stand and age for 24 hours, then a Buchner funnel with a diameter of 60 mm was selected under reduced pressure. The filter paper was trimmed to be smaller than the Buchner funnel but could cover all the pores, and deionized water was added dropwise to moisten the filter paper. The air extraction valve was opened to make the filter paper funnel tightly connected. The solid-liquid mixture was slowly poured into the center of the Buchner funnel. After filtration, it was washed three times with ammonium chloride and deionized water respectively to obtain a white precipitate;

[0047] The white precipitate was placed in a blast drying oven and dried at 80 °C for 12 hours;

[0048] The dried precipitate was placed in a muffle furnace and calcined at 500 °C for 2 hours, then the temperature was raised to 700 °C and calcined for 4 hours, and finally calcined at 1100 °C for 1 hour. After the temperature dropped to room temperature, the calcined alumina was added to a TYEE horizontal sand mill, the rotation speed was set at 2500 r / min, and it was ground for 0.5 hours to obtain uniformly dispersed alumina powder.

[0049] Example 4:

[0050] Accurately weigh 128 g of aluminum nitrate hydrate and 133 g of aluminum sulfate hydrate, add them to 1 L of deionized water, and dissolve them under stirring to prepare a mixed aluminum source solution with a concentration of 0.4 mol / L;

[0051] Weigh 80 g of sodium hydroxide and add it to 1 L of deionized water to prepare a sodium hydroxide solution with a concentration of 2 mol / L;

[0052] Under stirring with a heat - collecting type constant - temperature magnetic stirrer, add polyethylene glycol 200 to the aluminum source solution. Subsequently, slowly dropwise add sodium hydroxide solution to it at 50 °C. During this process, white flocculates will be produced. After reacting for 6 hours, stop the reaction when the measured pH value is greater than 9 to obtain a solid - liquid mixture;

[0053] Let the solid - liquid mixture stand and age for 24 hours. Then, under reduced pressure, select a Buchner funnel with a diameter of 60 mm. Trim the filter paper to be smaller than the Buchner funnel but able to cover all the pores, and drip deionized water to moisten the filter paper. Open the air - extraction valve to make the filter - paper funnel tightly connected. Slowly pour the solid - liquid mixture into the center of the Buchner funnel. After filtration, wash it three times each with ammonium chloride and deionized water to obtain a white precipitate;

[0054] Place the white precipitate in a blast drying oven and dry it at 80 °C for 12 hours;

[0055] Place the dried precipitate in a muffle furnace and calcine it at 500 °C for 2 hours, then raise the temperature to 700 °C and calcine it for 4 hours, and finally calcine it at 1100 °C for 1 hour. After the temperature drops to room temperature, add the calcined alumina to a TYEE horizontal sand mill, set the rotation speed to 2500 r / min, and grind for 1 hour to obtain a uniformly dispersed alumina powder.

[0056] Example Five:

[0057] Accurately weigh 112 g of aluminum nitrate hydrate and 200 g of aluminum sulfate hydrate, add them to 1 L of deionized water, and dissolve them under stirring to prepare a mixed aluminum source solution with a concentration of 0.6 mol / L;

[0058] Weigh 80 g of sodium hydroxide and add it to 1 L of deionized water to prepare a sodium hydroxide solution with a concentration of 2 mol / L;

[0059] Under stirring with a heat - collecting type constant - temperature magnetic stirrer, add polyethylene glycol 400 to the aluminum source solution. Subsequently, slowly dropwise add sodium hydroxide solution to it at 50 °C. During this process, white flocculates will be produced. After reacting for 8 hours, stop the reaction when the measured pH value is greater than 9 to obtain a solid - liquid mixture;

[0060] Let the solid - liquid mixture stand and age for 24 hours. Then, under reduced pressure, select a Buchner funnel with a diameter of 60 mm. Trim the filter paper to be smaller than the Buchner funnel but able to cover all the pores, and drip deionized water to moisten the filter paper. Open the air - extraction valve to make the filter - paper funnel tightly connected. Slowly pour the solid - liquid mixture into the center of the Buchner funnel. After filtration, wash it three times each with ammonium chloride and deionized water to obtain a white precipitate;

[0061] Place the white precipitate in a blast drying oven and dry it at 80 °C for 12 hours;

[0062] The dried precipitate was placed in a muffle furnace and calcined at 500 °C for 3 hours, then the temperature was raised to 700 °C and calcined for 5 hours, and finally calcined at 1100 °C for 2 hours. After the temperature dropped to room temperature, the calcined alumina was added to a TYEE horizontal sand mill, the rotation speed was set at 2500 r / min, and it was ground for 0.5 hours to obtain uniformly dispersed alumina powder.

[0063] Example 6:

[0064] Accurately weigh 300 g of aluminum nitrate hydrate and 267 g of aluminum sulfate hydrate, add them to 1 L of deionized water, and dissolve them under stirring to prepare a mixed aluminum source solution with a concentration of 0.8 mol / L.

[0065] Weigh 80 g of sodium hydroxide and add it to 1 L of deionized water to prepare a sodium hydroxide solution with a concentration of 2 mol / L.

[0066] Under stirring with a thermostatic magnetic stirrer with a heating mantle, add sodium dodecylbenzenesulfonate to the aluminum source solution, and then slowly drop the sodium hydroxide solution into it at 50 °C. White flocculants will be produced during this process. After reacting for 8 hours, stop the reaction when the measured pH value is greater than 9 to obtain a solid-liquid mixture.

[0067] After the solid-liquid mixture was allowed to stand and age for 24 hours, a Buchner funnel with a diameter of 60 mm was selected under reduced pressure. The filter paper was trimmed to be smaller than the Buchner funnel but could cover all the pores, and deionized water was added dropwise to moisten the filter paper. The air extraction valve was opened to make the filter paper funnel tightly connected. The solid-liquid mixture was slowly poured into the center of the Buchner funnel. After filtration, it was washed three times with ammonium chloride and deionized water respectively to obtain a white precipitate.

[0068] The white precipitate was placed in a forced-air drying oven and dried at 80 °C for 12 hours.

[0069] The dried precipitate was placed in a muffle furnace and calcined at 500 °C for 3 hours, then the temperature was raised to 700 °C and calcined for 4 hours, and finally calcined at 1100 °C for 1 hour. After the temperature dropped to room temperature, the calcined alumina was added to a TYEE horizontal sand mill, the rotation speed was set at 2500 r / min, and it was ground for 0.5 hours to obtain uniformly dispersed alumina powder.

[0070] Comparative Example 1:

[0071] The difference between this comparative example and Example 1 is that aluminum sulfate was used as the sole aluminum source, and the other operating steps were the same as those in Example 1.

[0072] Performance Test

[0073] The products in Examples 1 to 6 were subjected to performance tests, and the experimental results are shown in Table 1.

[0074] BET analysis: In a nitrogen adsorption and desorption instrument (BET), nitrogen is introduced into a container filled with powder materials under a certain pressure. Since any powder can adsorb nitrogen molecules, the nitrogen concentration in the container decreases. When the pressure returns to atmospheric pressure, the adsorbed nitrogen molecules desorb, and the nitrogen concentration in the container increases. By measuring the change in nitrogen concentration, the specific surface area of the powder material can be determined, etc.

[0075] Table 1 Properties of Alumina

[0076] Serial number Average grain size (nm) <![CDATA[Specific surface area (m 2 / g)]]> <![CDATA[Pore volume (cm 3 / g)]]> Most probable pore size (nm) Example 1 35.9 667 0.021 3.8 Example 2 36.5 641 0.023 3.7 Example 3 36.0 606 0.025 3.7 Example 4 37.5 612 0.054 3.7 Example 5 38.0 596 0.063 3.7 Example 6 40.1. 435 0.103 3.7 Comparative Example 1 100.1 61.2 0.141 2.6

[0077] As can be seen from the above table, the product prepared with an aluminum source concentration of 0.2 mol / L has a specific surface area of 667 m 2 / g, the product prepared with 0.4 mol / L has a specific surface area of 612 m 2 / g, the product prepared with 0.6 mol / L has a specific surface area of 596 m 2 / g, the product prepared with 0.8 mol / L has a specific surface area of 435 m 2 / g. As the aluminum source concentration increases, the specific surface area of the product decreases significantly. The pore volume shows the same trend of change.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered by the scope of the claims and the description of the present invention.

Claims

1. A process for preparing aluminum oxide powder, characterized in that: The following steps are involved: Step (a) preparing an aluminum source solution: accurately weighing a certain mass of hydrated aluminum nitrate and hydrated aluminum sulfate, adding them into deionized water, and dissolving them under stirring to prepare a mixed aluminum source solution; Step (b) preparing an alkaline solution: weighing a certain amount of sodium hydroxide and adding it to deionized water to prepare a sodium hydroxide solution; Step (c) preparing an alumina precursor: adding a dispersant to an aluminum source solution while stirring it with a heat-collecting constant-temperature magnetic stirrer, and then slowly dropping a sodium hydroxide solution thereto at 50° C., during which white floccules are produced. After reacting for 6 to 8 hours, the pH value is measured to be greater than 9 and then the reaction is stopped to obtain a solid-liquid mixture; Step (d) aging: the solid-liquid mixture was aged for 24 hours, then filtered under reduced pressure and washed to obtain a white precipitate; Step (e) drying: placing the white precipitate in a forced air drying oven and drying at 80° C. for 12 hours; Step (f) Calcination: The dried precipitate is placed in a muffle furnace and calcined at 500° C. for 2 to 3 hours, then heated to 700° C. for 4 to 5 hours, and finally calcined at 1100° C. for 1 to 2 hours. After the temperature is reduced to room temperature, the precipitate is sand-milled to obtain a uniformly dispersed alumina powder.

2. The process for preparing alumina powder according to claim 1, characterized in that: The concentrations of the aluminum source solution prepared in step (a) are 0.2 mol / L, 0.4 mol / L, 0.6 mol / L, and 0.8 mol / L.

3. The process for preparing alumina powder according to claim 1, characterized in that: The concentration of the sodium hydroxide solution prepared in step (b) is 2 mol / L.

4. The process for preparing alumina powder according to claim 1, characterized in that: The dispersant in step (c) is selected from one or more of sodium laurate, polyethylene glycol 200, polyethylene glycol 400, sodium dodecylbenzene sulfonate and sodium stearate.

5. The process for preparing alumina powder according to claim 1, characterized in that: The filtering and washing operation in the step (d) is to select a 60 mm Büchner funnel, trim the filter paper so that it is smaller than the Büchner funnel but can cover all the pores, and drip deionized water to wet the filter paper, open the vacuum valve to make the filter paper funnel tightly connected, and slowly pour the solid-liquid mixture into the center of the Büchner funnel. After the filtration is completed, wash it with ammonium chloride and deionized water three times each.

6. The process for preparing alumina powder according to claim 1, characterized in that: The sand milling operation in step (f) is to add the calcined alumina into a TYEE horizontal sand mill, set the rotation speed to 2500 r / min, and grind for 0.5 to 1 hour.

7. The process for preparing aluminum oxide powder according to claim 1, characterized in that: The particle size of the prepared alumina powder is ≤200nm.

8. Alumina powder, characterized in that: Obtained by the method described in claims 1 to 7.