Magnesium-aluminum composite oxide and method for producing the same

Abstract

The present application relates to the field of magnesium-aluminum composite oxide preparation, and discloses a magnesium-aluminum composite oxide and a preparation method thereof.The method comprises the following steps: (1) under anhydrous conditions, performing a first reaction on aluminum and a first aliphatic alcohol to obtain an alkoxide aluminum-containing material; (2) under the action of a catalyst, performing a second reaction on the alkoxide aluminum-containing material obtained in step (1), magnesium and a second aliphatic alcohol under anhydrous conditions; (3) performing hydrolysis on the reaction product of step (2) to obtain a magnesium-aluminum bimetallic alkoxide, and then performing optional drying and calcination to obtain a magnesium-aluminum composite oxide; wherein the first aliphatic alcohol and the second aliphatic alcohol each independently comprise n-pentanol and optionally n-hexanol. The preparation method of the magnesium-aluminum composite oxide provided by the present application can obtain a high-purity magnesium-aluminum composite oxide without subsequent purification treatment, and has the advantages of short initiation time and short reaction time.

Description

Technical Field

[0001] The present invention relates to the field of preparation of magnesium-aluminum composite oxides, and in particular to a magnesium-aluminum composite oxide and a preparation method thereof. Background Art

[0002] High-purity, ultrafine magnesium-aluminum spinel powder (magnesium-aluminum composite oxide) refers to artificially synthesized, submicron to nanometer-sized solid particles with a purity generally exceeding 99.99%. Magnesium-aluminum spinel powder was previously primarily used in the refractory, wear-resistant, fine ceramic, and pigment industries. In recent years, its application has expanded to high-tech fields such as optical performance materials, catalysts, and their carrier materials. With the development of laser crystal materials and functional materials, higher requirements are being placed on the purity, particle size, and chemical uniformity of magnesium-aluminum spinel powder. Therefore, producing high-purity, ultrafine, and chemically uniform magnesium-aluminum spinel powder is crucial for its application.

[0003] Currently, there is extensive research on the preparation of magnesium-aluminum spinel, both domestically and internationally. The main methods used include solid-phase methods, precipitation methods, sol-gel methods, aluminum-magnesium bimetallic alkoxide hydrolysis methods, hydrothermal synthesis methods, combustion synthesis methods, and solution evaporation methods. The advantages of the aluminum-magnesium bimetallic alkoxide hydrolysis method are that it uses metallic aluminum, metallic magnesium, and fatty alcohols as raw materials, does not introduce impurity ions during the reaction, and can be further purified through vacuum distillation or recrystallization, resulting in a magnesium-aluminum spinel powder of higher purity.

[0004] US6514473B2, US6517795B1, US20010001653A1, CN1109576C, and CN1171979A disclose methods for preparing high-purity hydrotalcite by reacting an alcohol or alcohol mixture with at least one or more divalent metals and at least one or more trivalent metals, and then hydrolyzing the resulting alkoxide mixture with water. The corresponding metal oxide can be prepared by calcination. However, the reaction temperature required for the fatty alcohol and metallic aluminum and magnesium is much higher than the boiling point of the fatty alcohol, requiring a special reaction apparatus. The reaction conditions are harsh, and alcohol volatilization losses are significant, requiring multiple additions of alcohol for complete reaction. This complex operation and increased costs hinder industrial application. Furthermore, the addition of water-soluble organic or inorganic anions during the hydrolysis process introduces new impurities, resulting in a low-purity product that requires subsequent filtration and purification.

[0005] Therefore, there is an urgent need to develop a simple-to-operate process to prepare high-purity magnesia-alumina spinel powder. Summary of the Invention

[0006] The present invention aims to overcome the problems of the prior art and provide a magnesium-aluminum composite oxide and a method for preparing the same. The method for preparing the magnesium-aluminum composite oxide provided by the present invention can produce a high-purity magnesium-aluminum composite oxide without subsequent purification treatment, while also having the advantages of short initiation and reaction times.

[0007] In order to achieve the above object, the present invention provides a method for preparing a magnesium-aluminum composite oxide, which comprises the following steps:

[0008] (1) Under anhydrous conditions, reacting aluminum with a first fatty alcohol to obtain a material containing aluminum alkoxide;

[0009] (2) in the presence of a catalyst, subjecting the alkoxyaluminum-containing material obtained in step (1), magnesium element, and a second fatty alcohol to a second reaction under anhydrous conditions;

[0010] (3) hydrolyzing the reaction product of step (2) to obtain a magnesium aluminum bimetallic alkoxide, and then optionally drying and calcining to obtain a magnesium aluminum composite oxide;

[0011] Wherein, the first fatty alcohol and the second fatty alcohol each independently include n-pentanol and optionally n-hexanol, and the molar ratio of n-pentanol to n-hexanol is 1:0-10.

[0012] In this area, those skilled in the art think that the positive alcohol reaction rate that carbon number is more is faster, but there is violent reaction, be difficult to control problem, simultaneously along with the growth of carbochain its viscosity is larger, be unfavorable for the carrying out of building-up reactions, usually adopt fatty alcohol of C2-C4 such as ethanol, Virahol, propyl carbinol to prepare magnesium-aluminum composite oxide.In addition, in the reaction of magnesium and fatty alcohol, magnesium metal and fatty alcohol reaction cause comparatively difficulty, usually adopt fatty alcohol of C2-C4 and magnesium metal to react under catalyzer and / or organic solvent as the condition of dispersion agent, and initiation time is longer, has also introduced new impurity.The inventor finds in the research process, under anhydrous condition, adopt the positive alcohol that comprises n-amyl alcohol and randomly n-hexyl alcohol to prepare magnesium-aluminum composite oxide with specific two-step reaction, need not to obtain highly purified magnesium-aluminum composite oxide through subsequent purification process (as underpressure distillation, recrystallization etc.), can shorten initiation time when adopting specific alcohol of the present invention to participate in reaction simultaneously, thereby shorten the reaction system overall reaction time.

[0013] The second aspect of the present invention provides a magnesium-aluminum composite oxide prepared by the preparation method described in the first aspect.

[0014] Through the above technical solution, the beneficial effects of the present invention include:

[0015] The preparation method provided by the present invention can obtain high-purity magnesium-aluminum composite oxide without subsequent purification treatment, with a purity greater than 99.99%. At the same time, the magnesium-aluminum ratio in the magnesium-aluminum composite oxide can be flexibly adjusted to meet actual needs.

[0016] The preparation method provided by the present invention preferably has the advantages of a short initiation time, a fast reaction rate, mild reaction conditions, and the absence of impurities other than those carried by the metal magnesium and aluminum. The preparation method provided by the present invention uses a small amount of catalyst, which can reduce preparation costs. DETAILED DESCRIPTION

[0017] 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.

[0018] In the present invention, the terms "first" and "second" do not limit the substances and operations, but are only used to distinguish substances introduced in different steps and operations performed in different stages.

[0019] One aspect of the present invention provides a method for preparing a magnesium-aluminum composite oxide, the method comprising the following steps:

[0020] (1) Under anhydrous conditions, reacting aluminum with a first fatty alcohol to obtain a material containing aluminum alkoxide;

[0021] (2) in the presence of a catalyst, subjecting the alkoxyaluminum-containing material obtained in step (1), magnesium element, and a second fatty alcohol to a second reaction under anhydrous conditions;

[0022] (3) hydrolyzing the reaction product of step (2) to obtain a magnesium aluminum bimetallic alkoxide, and then optionally drying and calcining to obtain a magnesium aluminum composite oxide;

[0023] Wherein, the first fatty alcohol and the second fatty alcohol each independently include n-pentanol and optionally n-hexanol, and the molar ratio of n-pentanol to n-hexanol is 1:0-10.

[0024] In the preparation method of the present invention, the reactions in step (1) and step (2) must be carried out under anhydrous conditions to avoid the problem that the alkoxyaluminum generated in step (1) and the alkoxymagnesium aluminum generated in step (2) are hydrolyzed to form hydroxides, which prevents the reaction from continuing.

[0025] The present invention is not particularly limited to the method for achieving anhydrous conditions, and conventional techniques in the art can be used. For example, the reaction of the present invention can be carried out in a three-necked flask. Before the reaction, the three-necked flask can be washed and dried in the air or in an oven to ensure that the three-necked flask is clean and free of water.

[0026] It should be noted that the anhydrous conditions described in the present invention do not require complete anhydrous conditions, but only mean that no additional water is introduced, but do not exclude a very small amount of water adsorbed in the air in the raw materials and / or catalysts.

[0027] In the present invention, unless otherwise specified, the term "optionally" refers to containing or not containing, adding or not adding, adopting or not adopting. Specifically, n-hexanol may or may not be added to the first and second fatty alcohols of the present invention.

[0028] According to the present invention, preferably, the first fatty alcohol comprises n-pentanol and n-hexanol, and the molar ratio of n-pentanol to n-hexanol is 1:0.1-1;

[0029] The second fatty alcohol is n-pentanol.

[0030] In the present invention, the molar ratio of n-pentanol to n-hexanol is 1:0.1-1, for example, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, and any value within the range formed by any two of these values. This preferred embodiment facilitates obtaining high-purity magnesium-aluminum composite oxides and shortening the reaction initiation time. When the molar ratio of n-pentanol to n-hexanol exceeds the above range, the first reaction initiation time is significantly increased, thereby extending the overall reaction time of the reaction system. When the molar ratio of n-pentanol to n-hexanol is below the above range, the purity of the magnesium-aluminum composite oxide is reduced.

[0031] According to the present invention, preferably, the temperature of the first reaction is 20°C below the boiling point of the first fatty alcohol to the boiling point of the first fatty alcohol, preferably 20°C below the boiling point of the first fatty alcohol to 2°C below the boiling point of the first fatty alcohol. This preferred embodiment can maintain a high reaction rate while avoiding incomplete reaction caused by volatilization loss of the first fatty alcohol due to excessively high temperatures.

[0032] When the first fatty alcohol includes n-pentanol and n-hexanol, the temperature of the first reaction is based on the boiling point of n-pentanol.

[0033] The initiation time of the present invention refers to the time from the start of heating to the reaction temperature to the observation of continuous large-scale bubble generation (or bubble generation in clusters) in the solution. The preparation method provided by the present invention can significantly shorten the initiation time of the first reaction. According to the present invention, preferably, the initiation time of the first reaction is 0.2-4.5h, preferably 0.2-0.5h.

[0034] The reaction time of the present invention refers to the time from the observation of continuous large-scale bubble generation (or bubble generation in clusters) of the solution to the observation of no obvious bubble generation of the solution. The preparation method provided by the present invention can significantly shorten the reaction time of the first reaction. Preferably, the reaction time of the first reaction is 0.4-4 hours, preferably 0.5-2 hours.

[0035] According to the present invention, preferably, the molar ratio of the aluminum element to the first fatty alcohol is 1:3-5, preferably 1:3.1-4.5. This preferred embodiment is conducive to the complete reaction of the aluminum element.

[0036] According to the present invention, preferably, the purity of the aluminum element is not less than 99.9% by mass. This preferred embodiment is conducive to obtaining a high-purity magnesium-aluminum composite oxide.

[0037] The present invention does not particularly limit the form of the aluminum element, and can be any conventional choice in the art. Preferably, the aluminum element is selected from at least one of aluminum blocks, aluminum beans, aluminum sheets, aluminum wires, and aluminum chips.

[0038] The aluminum blocks, aluminum beans, aluminum sheets, aluminum wires, and aluminum chips described in the present invention are well known to those skilled in the art and will not be described in detail herein.

[0039] According to a specific embodiment of the present invention, the alkoxyaluminum-containing material obtained in step (1) is first cooled to 80-100° C. before the second reaction is carried out. This preferred embodiment can effectively reduce the volatilization of alcohol.

[0040] According to the present invention, the temperature of the second reaction is preferably 20°C below the boiling point of the second fatty alcohol to 2°C below the boiling point of the second fatty alcohol, preferably 10°C below the boiling point of the second fatty alcohol to 2°C below the boiling point of the second fatty alcohol. In this preferred embodiment, if the second reaction temperature is below the above range, the reaction is difficult to initiate and the reaction rate is slow. If the second reaction temperature is above the above range, the fatty alcohol is easily volatilized and lost, resulting in incomplete reaction.

[0041] The definition of the initiation time of the second reaction of the present invention is the same as that of the initiation time of the first reaction.

[0042] The preparation method provided by the present invention can significantly shorten the initiation time of the second reaction. Preferably, the initiation time of the second reaction is 0.25-5h, more preferably 0.25-0.5h.

[0043] The definition of reaction time of the second reaction of the present invention is the same as that of the first reaction.

[0044] The preparation method provided by the present invention can significantly shorten the reaction time of the second reaction. Preferably, the reaction time of the second reaction is 0.4-4h, preferably 0.6-3h.

[0045] According to the present invention, preferably, the molar ratio of the magnesium element to the second fatty alcohol is 1:2-7, preferably 1:2-4. This preferred embodiment can quickly and fully complete the reaction while avoiding excessive waste of fatty alcohol, thereby saving costs.

[0046] Preferably, the molar ratio of the magnesium element to the aluminum element is 1:0.3-3, preferably 1:0.5-2. With this preferred embodiment, the alkoxy magnesium aluminum can be fully dispersed to ensure smooth reaction.

[0047] Preferably, the mass ratio of the catalyst to the total reactants of step (2) is 1:100-300, more preferably 1:100-200, wherein the total reactants are the alkoxyaluminum-containing material obtained in step (1), elemental magnesium, and the second fatty alcohol. This preferred method significantly reduces the amount of catalyst used while increasing the reaction rate, thereby reducing costs.

[0048] The present invention provides a wide range of catalyst types, which can be selected from conventional options in the art. Preferably, the catalyst is selected from at least one of elemental iodine, mercuric dichloride, and aluminum trichloride. To further increase the reaction rate and avoid introducing other impurities, the catalyst is preferably elemental iodine.

[0049] According to the present invention, preferably, the purity of the magnesium element is not less than 99.9% by mass. This preferred embodiment is conducive to obtaining a high-purity magnesium-aluminum composite oxide.

[0050] The present invention does not particularly limit the form of the magnesium element, which can be selected conventionally in the art. Preferably, the magnesium element is selected from at least one of magnesium blocks, magnesium sheets, magnesium wires, magnesium chips, magnesium granules, magnesium bars, and magnesium powder.

[0051] The magnesium blocks, magnesium sheets, magnesium wires, magnesium chips, magnesium particles, magnesium bars and magnesium powder of the present invention are well known to those skilled in the art and will not be described in detail herein.

[0052] According to the present invention, preferably, the first reaction and / or the second reaction is carried out under condensation reflux conditions.

[0053] Preferably, the reactor is purged with inert gas before adding the reaction materials in the first and second reactions, so as to replace the air in the reactor. With this preferred embodiment, the surface oxidation of elemental aluminum and elemental magnesium can be prevented while drying the inside of the reactor.

[0054] The kind of the inert gas is not particularly limited in the present application, and any gas that does not affect the reaction can be used. Preferably, the inert gas is nitrogen.

[0055] In the present application, no additives such as hydroxyl anion, organic anion (especially alkoxide anion, alkoxyl ether sulfate, aryl ether sulfate, glycol ether sulfate), inorganic anion (carbonate, bicarbonate, chloride, nitrate, sulfate, polyoxometalate) are added in the hydrolysis process, so as to achieve the purpose of complete hydrolysis, without introducing new impurities and without the need for subsequent impurity removal treatment. Moreover, in the hydrolysis process in step (3) of the present application, the hydrolysis temperature and the amount of water are controlled within the following ranges, which is beneficial to the complete hydrolysis of the alkoxymagnesium aluminum and reduces the amount of water used, thereby saving costs.

[0056] According to the present application, preferably, the temperature of the hydrolysis in step (3) is 60-100°C, preferably 85-95°C.

[0057] The time of the hydrolysis is not particularly limited in the present application, and the slurry after hydrolysis is preferably good in flowability and not adhered to the wall.

[0058] According to the present application, preferably, the mass ratio of the reaction product in step (2) to water is 1:1-5, preferably 1:1.1-3.5.

[0059] According to the present application, preferably, the method further comprises: separating the material obtained by the hydrolysis in step (3), and then optionally drying and calcining to obtain the magnesium-aluminum composite oxide.

[0060] The separation method is not particularly limited in the present application, and can be performed by using conventional techniques in the art.

[0061] In the present application, the term "optionally" means that something is contained or not contained, added or not added, or used or not used, unless otherwise specified. Specifically, the drying in step (3) of the present application can be performed or not performed.

[0062] The specific conditions of the drying are not particularly limited in the present application, and can be performed by using conventional methods in the art.

[0063] According to the present application, preferably, the conditions of the calcination in step (3) include: temperature of 550-850℃, time of 4-8h. The calcination is generally carried out in an air atmosphere, which can include a flowing atmosphere or a static atmosphere.

[0064] According to a particularly preferred embodiment of the present application, a method for preparing a magnesium-aluminum composite oxide, the method comprises the following steps:

[0065] (1) under anhydrous conditions, subjecting aluminum element and a first fatty alcohol to a first reaction to obtain an alkoxide-containing aluminum material;

[0066] (2) under the action of a catalyst, subjecting the alkoxide-containing aluminum material obtained in step (1), magnesium element and a second fatty alcohol to a second reaction under anhydrous conditions;

[0067] (3) subjecting the reaction product of step (2) to hydrolysis to obtain a magnesium-aluminum bimetallic alcohol salt, and then subjecting the magnesium-aluminum bimetallic alcohol salt to optional drying and calcination to obtain a magnesium-aluminum composite oxide;

[0068] wherein the first fatty alcohol includes n-pentanol and n-hexanol, the molar amount ratio of the n-pentanol and the n-hexanol is 1:0.1-1, and the second fatty alcohol is n-pentanol;

[0069] The temperature of the second reaction is 20℃ below the boiling point of the second fatty alcohol to 2℃ below the boiling point of the second fatty alcohol, preferably 10℃ below the boiling point of the second fatty alcohol to 2℃ below the boiling point of the second fatty alcohol;

[0070] The initiation time of the second reaction is 0.25-0.5h;

[0071] The reaction time of the second reaction is 0.6-3h;

[0072] The molar ratio of the magnesium element to the second fatty alcohol is 1:2-4;

[0073] The molar ratio of the magnesium element to the aluminum element is 1:0.5-2.

[0074] The specific preparation method provided by the present application can obtain a magnesium-aluminum composite oxide with high purity without subsequent purification treatment, and the purity is higher than 99.99%. Meanwhile, the preparation method provided by the present application has the advantages of mild reaction conditions, short initiation time, fast reaction rate, and no introduction of impurities other than the impurities brought by magnesium and aluminum. Preferably, the preparation method provided by the present application has a small amount of catalyst, which can reduce the preparation cost.

[0075] The present application provides a magnesium-aluminum composite oxide prepared by the preparation method of the first aspect.

[0076] The high-purity magnesium-aluminum composite oxide prepared by the method of the present invention has a wide range of applications, for example, it can be used in catalyst preparation. According to the present invention, preferably, the purity of the magnesium-aluminum composite oxide is greater than 99.99%.

[0077] The present invention will be described in detail below through examples.

[0078] In the following examples, the magnesium-aluminum ratio and product purity of the magnesium-aluminum composite oxide were measured by inductively coupled plasma (ICP);

[0079] In the following examples, all reagents used were commercially available and of analytical grade.

[0080] Example 1

[0081] (1) The three-necked flask was cleaned and placed in an oven to dry in advance to ensure that the three-necked flask was clean and free of water. The three-necked flask was purged with nitrogen before the test. 6.76 g of aluminum wire with a purity of 99.996% by mass was added to the three-necked flask equipped with a heating and condensing system. 86.85 g of n-pentanol was added to the three-necked flask to submerge the aluminum wire. The temperature was gradually raised to 135°C (the boiling point of n-pentanol is 137.8°C) and refluxed until the solution had no obvious bubbles and no aluminum wire was present. The temperature was then lowered to 100°C. The initiation time and reaction time of the reaction are shown in Table 1.

[0082] (2) To 92.86 g of the n-pentyl aluminum solution in n-pentanol obtained by the above reaction, 3.01 g of magnesium chips with a purity of 99.9% by mass, 0.67 g of iodine with a purity of 99.8% by mass, and 35.42 g of n-pentanol were added to a three-necked flask; the temperature was gradually raised to 135° C., and reflux was maintained until no obvious bubbles were generated in the solution and no magnesium chips remained in the solution, and the reaction was completed. The initiation time and reaction time of the reaction are shown in Table 1.

[0083] (3) 131.04 g of the n-pentanol solution of n-pentoxy magnesium aluminum obtained in step (2) was maintained at 90° C. and transferred to a 1000 mL beaker. 90° C. deionized water was added for hydrolysis until the solution was separated and the lower slurry had good fluidity and did not adhere to the wall. 350 g of deionized water was used. A magnesium aluminum hydroxide slurry phase and an n-pentanol phase were obtained. The upper n-pentanol phase was separated. The magnesium aluminum hydroxide slurry was placed in a blast constant temperature drying oven and dried at 120° C. for 12 hours. It was then placed in a muffle furnace and calcined at 600° C. for 6 hours to obtain a magnesium aluminum composite oxide. The magnesium aluminum ratio and product purity were obtained by inductively coupled plasma (ICP) analysis and are shown in Table 2.

[0084] Example 2

[0085] (1) Wash the three-necked flask in advance and place it in an oven to dry to ensure that the three-necked flask is clean and free of water. Purge the three-necked flask with nitrogen before the test. Add 2.69g of the aluminum wire used in Example 1 to the three-necked flask equipped with a heating and condensing system. Take 28.30g of n-pentanol and 10.22g of n-hexanol and add them to the three-necked flask to immerse the aluminum wire. Gradually raise the temperature to 135°C and maintain condensation and reflux until the solution has no obvious bubbles and no aluminum wire in the solution. Then cool it down to 100°C. The initiation time and reaction time of the reaction are shown in Table 1.

[0086] (2) 2.40 g of the magnesium chips used in Example 1 were added to 39.06 g of the solution obtained by the above reaction, 0.50 g of iodine with a purity of 99.8% by mass, and 27.24 g of n-amyl alcohol were added to a three-necked flask; the temperature was gradually raised to 130 ° C., and condensation reflux was maintained until the solution had no obvious bubbles and no magnesium chips remained in the solution, and the reaction was terminated. The initiation time and reaction time of the reaction are shown in Table 1.

[0087] (3) 68.5 g of the n-pentanol solution of the alkoxy magnesium aluminum obtained in step (2) was maintained at 90° C. and transferred to a 1000 mL beaker. Deionized water at 90° C. was added for hydrolysis until the solution was separated and the lower slurry had good fluidity and did not adhere to the wall. 210 g of deionized water was used. A magnesium aluminum hydroxide slurry phase and an n-pentanol phase were obtained. The upper n-pentanol phase was separated. The magnesium aluminum hydroxide slurry was placed in a blast constant temperature drying oven and dried at 120° C. for 12 hours. It was then placed in a muffle furnace and calcined at 600° C. for 6 hours to obtain a magnesium aluminum composite oxide. The magnesium aluminum ratio and product purity were obtained by inductively coupled plasma (ICP) analysis and are shown in Table 2.

[0088] Example 3

[0089] The method of Example 1 was followed, except that the n-pentanol in step (1) was replaced with 44.08 g of n-pentanol and 49.56 g of n-hexanol to obtain a magnesium-aluminum composite oxide. The magnesium-aluminum ratio and product purity were determined by inductively coupled plasma (ICP) analysis and are shown in Table 2.

[0090] Example 4

[0091] The method of Example 1 was followed, except that the temperature for the first and second reactions was 137° C. After the first reaction, unreacted aluminum chips remained, requiring replenishment of n-pentanol solution until the reaction was complete. After the second reaction, unreacted magnesium chips remained, requiring replenishment of n-pentanol solution until the reaction was complete. This cumbersome operation increased costs and was not conducive to industrial application.

[0092] The magnesium-aluminum composite oxide was obtained, and its magnesium-aluminum ratio and product purity were obtained by inductively coupled plasma (ICP) analysis, as shown in Table 2.

[0093] Comparative Example 1

[0094] High-purity alkoxymagnesium aluminum was prepared according to the method of Example 1, except that 6.78 g of the aluminum wire used in Example 1, 3.01 g of the magnesium chips used in Example 1, and 0.60 g of the iodine element used in Example 1 were added simultaneously into a three-necked flask and reacted together with 106.27 g of n-pentanol at 135° C. After 36 hours of reaction, a large amount of aluminum wire and magnesium chips (about 9.02 g) still remained, indicating that the reaction was not complete.

[0095] The magnesium-aluminum composite oxide was obtained, and its magnesium-aluminum ratio and product purity were obtained by inductively coupled plasma (ICP) analysis, as shown in Table 2.

[0096] Comparative Example 2

[0097] In a three-necked flask equipped with a heating and condensing system, 3.42 g of the magnesium chips used in Example 1 were first added, followed by 33.50 g of n-pentanol to submerge the magnesium chips. The temperature was gradually raised to 135°C while maintaining reflux. The resulting magnesium alkoxide adhered to the bottom of the flask, preventing the reaction from proceeding further and preventing the production of a magnesium-aluminum composite oxide.

[0098] Comparative Example 3

[0099] The method of Example 1 was followed, except that the n-pentanol in step (1) and step (2) was replaced by an equimolar amount of n-butanol, respectively. The reaction temperature was 115° C. (the boiling point of n-butanol is 117.25° C.) to obtain a magnesium-aluminum composite oxide. The magnesium-aluminum ratio and product purity obtained by inductively coupled plasma (ICP) analysis are shown in Table 2.

[0100] Comparative Example 4

[0101] The method of Example 2 was followed, except that n-pentanol and n-hexanol in step (1) were replaced by 43.02 g of n-hexanol, and the reaction temperature was 150° C. to obtain a magnesium-aluminum composite oxide. The magnesium-aluminum ratio and product purity were obtained by inductively coupled plasma (ICP) analysis and are shown in Table 2.

[0102] Comparative Example 5

[0103] (1) The three-necked flask was placed in an oven for drying in advance to ensure that it was clean and free of water. The three-necked flask was purged with nitrogen before the test. 6.77 g of the aluminum wire used in Example 1 was added to the three-necked flask equipped with a heating and condensing system. 106.33 g of n-hexanol was added to the three-necked flask to submerge the aluminum metal. The temperature was gradually raised to 150°C (the boiling point of n-hexanol is 157°C) to allow the n-hexanol and high-purity aluminum wire to react. The solution was kept under condensation and reflux until no obvious bubbles were generated in the solution and no high-purity aluminum wire was present in the solution. The temperature was then lowered to 100°C. The initiation time and reaction time of the reaction are shown in Table 1.

[0104] (2) In 112.35 g of n-hexyloxyaluminum solution obtained from the above reaction, 6.01 g of magnesium turnings used in step (1) and 101 g of n-hexanol were added into a three-necked flask; the n-hexanol and the high-purity magnesium turnings were reacted by gradually heating to 150°C and keeping condensation reflux until no obvious bubbles were generated in the solution and no magnesium turnings remained in the solution, and the reaction was completed. The initiation time and the reaction time are shown in Table 1.

[0105] (3) The 218.86 g of n-hexyloxy magnesium aluminum solution was transferred into a 1000 mL beaker and maintained at 90°C, and deionized water was added for hydrolysis until the solution was layered and the lower slurry had good flowability, and the deionized water used was 315 g. A magnesium aluminum hydroxide slurry phase and an n-hexanol phase were generated, the upper n-hexanol phase was separated, and the magnesium aluminum hydroxide slurry was placed in a blast constant temperature drying oven and dried at 120°C for 12 hours to obtain a high-purity magnesium aluminum hydroxide complex. The above magnesium aluminum hydroxide complex was calcined in a muffle furnace at 600°C for 6 hours to obtain a high-purity magnesium aluminum composite oxide, and the magnesium aluminum ratio and the product purity were analyzed by inductively coupled plasma (ICP) and are shown in Table 2.

[0106] Table 1

[0107]

[0108]

[0109] Table 2

[0110]

[0111] As can be seen from the results in Table 2, the high-purity magnesium aluminum composite oxide with a purity greater than 99.99% can be obtained without subsequent purification treatment by using the specific preparation method described in the present application. Meanwhile, the magnesium aluminum ratio in the magnesium aluminum composite oxide can be flexibly adjusted to meet actual needs.

[0112] As can be seen from the results in Table 1, the preparation method provided in the present application has the advantages of short initiation time and fast reaction rate.

[0113] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed in the present application and fall within the protection scope of the present application.

Claims

1. A method for preparing a magnesium-aluminum composite oxide, characterized in that: The method comprises the following steps: (1) Under anhydrous conditions, reacting aluminum element and a first fatty alcohol to obtain a material containing aluminum alkoxide; (2) in the presence of a catalyst, subjecting the alkoxyaluminum-containing material obtained in step (1), magnesium element, and the second fatty alcohol to a second reaction under anhydrous conditions; (3) hydrolyzing the reaction product of step (2) to obtain a magnesium aluminum bimetallic alkoxide, and then optionally drying and calcining to obtain a magnesium aluminum composite oxide; Wherein, the first fatty alcohol and the second fatty alcohol each independently include n-pentanol and optionally n-hexanol, and the molar ratio of n-pentanol to n-hexanol is 1:0-10.

2. The method according to claim 1, wherein The first fatty alcohol includes n-pentanol and n-hexanol, and the molar ratio of n-pentanol to n-hexanol is 1:0.1-1; The second fatty alcohol is n-pentanol.

3. The method according to claim 1, wherein The temperature of the first reaction is 20° C. below the boiling point of the first fatty alcohol to the boiling point of the first fatty alcohol.

4. The method according to claim 3, wherein: The temperature of the first reaction is 20° C. below the boiling point of the first fatty alcohol to 2° C. below the boiling point of the first fatty alcohol.

5. The method according to claim 1, wherein The initiation time of the first reaction is 0.2-4.5h.

6. The method according to claim 5, wherein: The initiation time of the first reaction is 0.2-0.5h.

7. The method according to claim 1, wherein The reaction time of the first reaction is 0.4-4h.

8. The method according to claim 7, wherein: The reaction time of the first reaction is 0.5-2h.

9. The method according to claim 1, wherein The molar ratio of the aluminum element to the first fatty alcohol is 1:3-5.

10. The method according to claim 9, wherein: The molar ratio of the aluminum element to the first fatty alcohol is 1:3.1-4.

5.

11. The method according to claim 1, wherein The purity of the aluminum element is not less than 99.9% by mass.

12. The method according to any one of claims 1 to 11, wherein: The temperature of the second reaction is 20° C. below the boiling point of the second fatty alcohol to 2° C. below the boiling point of the second fatty alcohol.

13. The method according to claim 12, wherein: The temperature of the second reaction is 10° C. below the boiling point of the second fatty alcohol to 2° C. below the boiling point of the second fatty alcohol.

14. The method according to any one of claims 1 to 11, wherein: The initiation time of the second reaction is 0.25-5h.

15. The method according to claim 14, wherein The initiation time of the second reaction is 0.25-0.5h.

16. The method according to any one of claims 1 to 11, wherein: The reaction time of the second reaction is 0.4-4h.

17. The method according to claim 16, wherein The reaction time of the second reaction is 0.6-3h.

18. The method according to any one of claims 1 to 11, wherein: The molar ratio of the magnesium element to the second fatty alcohol is 1:2-7.

19. The method according to claim 18, wherein The molar ratio of the magnesium element to the second fatty alcohol is 1:2-4.

20. The method according to any one of claims 1 to 11, wherein: The molar ratio of the magnesium element to the aluminum element is 1:0.3-3.

21. The method according to claim 20, wherein The molar ratio of the magnesium element to the aluminum element is 1:0.5-2.

22. The method according to any one of claims 1 to 11, wherein: The mass ratio of the catalyst to the total reactants of step (2) is 1:100-300, wherein the total reactants are the alkoxyaluminum-containing material obtained in step (1), magnesium element and the second fatty alcohol.

23. The method according to claim 22, wherein The mass ratio of the catalyst to the total reactants of step (2) is 1:100-200.

24. The method according to any one of claims 1 to 11, wherein: The catalyst is selected from at least one of elemental iodine, mercuric dichloride and aluminum trichloride.

25. The method according to claim 24, wherein The catalyst is elemental iodine.

26. The method according to any one of claims 1 to 11, wherein: The purity of the magnesium element is not less than 99.9% by mass.

27. The method according to any one of claims 1 to 11, wherein: The first reaction and / or the second reaction is carried out under condensation reflux conditions.

28. The method according to any one of claims 1 to 11, wherein: The hydrolysis temperature in step (3) is 60-100°C; The mass ratio of the reaction product of step (2) to water is 1:1-5.

29. The method according to claim 28, wherein The hydrolysis temperature in step (3) is 85-95°C; The mass ratio of the reaction product of step (2) to water is 1:1.1-3.

5.

30. The method according to any one of claims 1 to 11, wherein: The calcination conditions in step (3) include: a temperature of 550-850°C and a time of 4-8 hours.

31. A magnesium-aluminum composite oxide prepared by the preparation method according to any one of claims 1 to 30; The purity of the magnesium-aluminum composite oxide is greater than 99.99%.

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