CN1195582C - Spherical aluminium oxide carrier material and preparation process thereof - Google Patents

Abstract

The invention discloses a spherical alumina carrier material and a preparation method thereof. The carrier material contains 50-99% by weight of alumina and 1-50% by weight of magnetic particles, wherein the magnetic particles are covered by _SiO2 and one or more inner cores selected from Fe ₃ O ₄ , Fe and γ-Fe ₂ O ₃ , the weight ratio of said cladding layer to inner core is 0.01-6:1. The carrier material is obtained by slowly acidifying nano- _Fe3O4 particles in sodium silicate solution to form a _SiO2 coating layer, and then mixing them with aluminum hydroxide sol _and organic amine solution to form a uniformly dispersed aqueous phase, and then After forming water-in-oil droplets with the oil phase, the heating system makes the sol droplets in the water phase gel and solidify, and then it is obtained through conventional hydrothermal treatment, aging, drying and sintering processes. The spherical alumina carrier material provided by the invention has superparamagnetic properties, and can be used as a catalyst carrier in the reaction process of an external magnetic field. The external magnetic field is used to facilitate positioning control, separation and recovery, and achieve the purpose of repeated recycling.

Description

A kind of spherical alumina support material and preparation method thereof

technical field

The invention relates to a spherical alumina carrier material and a preparation method thereof.

technical background

Fine-grained catalytic materials have the advantages of large specific surface area, fast mass transfer rate, and high catalytic efficiency. The development of fine-grained catalysts is an important development direction of heterogeneous catalysis research in recent years. However, due to the small size of catalyst particles, it is difficult to control , and there is the problem that the separation and recovery of the catalyst after the reaction is difficult. The development of fine-grained magnetic catalysts and magnetically stable reaction technology (see "Research and Development of Industrial Catalysts", China Petrochemical Press, 1997, p. 195) has opened up a new way for the research and application of functionalized fine-grained catalysts.

In petrochemical industry, alumina, as the catalyst carrier with the largest demand, is widely used in various reactions such as oxidation, hydrogenation, dehydrogenation, reforming, isomerization, disproportionation, polymerization, etc., and can also be directly used as catalyst activity components and adsorbents.

There are many reports on alumina and its preparation methods. For example, the spherical alumina carrier disclosed in US Pat. 2,620,314 is formed by dropping a solution containing aluminum hydroxide sol and organic amine into a hot oil column through a plate hole for solidification, aging and sintering. The γ-Al ₂ O ₃ carrier disclosed in US.Pat.4,273,735 is that the solidified aluminum hydroxide obtained in the oil column is subjected to hydrothermal treatment in the oil medium to obtain aluminum hydroxide with a boehmite structure, which is aged and made after sintering. US.Pa t.4,315,839 discloses a high-strength, light-weight, high-pore-volume alumina carrier with good crystallinity, which is mixed with ultrafine boehmite or boehmite during the granulation and molding process of aluminum hydroxide. Stone, obtained after sintering. The alumina carrier disclosed in US.Pat.2,915,365, US.Pat.3,480,389 and US.Pat.3,628,914 has higher mechanical strength, specific surface area and higher activity after granulating the gibbsite containing trihydrate alumina The product is obtained by high-temperature hydrothermal treatment in an acid medium, and then sintered.

The above-mentioned documents mainly disclose the preparation of alumina and the control of alumina crystal form, structure or strength, etc., but none of them involve the magnetic properties of alumina. So far, no relevant alumina carrier materials with superparamagnetic properties have been found. reports.

The object of the present invention is to provide a spherical alumina carrier material with superparamagnetic properties and a preparation method thereof.

Contents of the invention

The spherical alumina carrier material provided by the invention contains 50-99% by weight of alumina and 1-50% by weight of magnetic particles, wherein said magnetic particles are coated with SiO ₂ and selected from Fe ₃ O ₄ , Fe and One or several inner cores in γ-Fe ₂ O ₃ , the weight ratio of the SiO ₂ cladding layer to the inner core is (0.01-6):1, preferably (0.3-4.0):1.

The spherical alumina carrier material provided by the invention has a particle diameter between 10 μm and 6 mm.

Said alumina is selected from amorphous alumina, various low-temperature transitional phase aluminas (ρ-, χ-, η-, γ-), various high-temperature transitional phase aluminas (κ-, δ-, θ-) Or one or more mixtures of α-alumina. The alumina is converted from the precursor of alumina, and the precursors of alumina are mainly basic aluminum salt, amorphous aluminum hydroxide, alumina trihydrate, gibbsite, and albite , Connaught diaspore, alumina monohydrate, diaspore and boehmite, false boehmite, etc.

In the spherical alumina carrier material provided by the present invention, the magnetic particles are uniformly dispersed in the structure of the alumina carrier (Fig. 3). Said magnetic particles, the core is one or more monodomain superparamagnetic particles with a particle size of 3 to 30 nanometers, and the cladding layer is an amorphous SiO ₂ layer (Fig. 1) tightly covering the core, which has a good Hydrophilicity, as shown by X-ray diffraction (XRD) spectrum, there is a large wave packet in the range of 2θ=20～30°, which is the characteristic peak of amorphous SiO ₂ (Figure 2), amorphous SiO ₂ The cladding layer and the inner core are firmly combined to form magnetic particles. For magnetic particles with multiple particles in the inner core, the particles are uniformly distributed due to the barrier of _SiO2 .

The hysteresis loop measured by the spherical alumina carrier material provided by the present invention has no hysteresis, and when an external magnetic field exists, it has good magnetic properties. When the external magnetic field H=0, the residual magnetization Mr and the coercive force Hc are both It is zero and has superparamagnetism.

The spherical alumina carrier material provided by the present invention has a certain composition gradient and structural gradient formed between the inner magnetic core, the _SiO2 cladding layer on the surface and the carrier component alumina, and has good thermal stability and Corrosion resistance, due to the isolation effect of the SiO ₂ coating, the adverse reaction between the iron component in the inner core and the alumina component of the carrier can be avoided. In addition, during the application of the carrier material, the iron component in the inner core can also be avoided. poisoning of catalyst active components.

The present invention also provides a preparation method for the above-mentioned spherical alumina carrier material, which includes preparing _SiO2 coated magnetic component particles, adopting the process of molding in oil (inner gel) to prepare magnetic spherical alumina, and further reducing Or oxidation treatment, control the form of the magnetic particle core in the carrier and other steps.

More specifically, the preparation method of the spherical alumina carrier material provided by the present invention contains the following steps:

1. Add alkali to the aqueous solution containing Fe ²⁺ and Fe ³⁺ salt at 50-100°C, transfer the deposited nano-Fe ₃ O ₄ particles into sodium silicate solution, and add acid under the protection of inert gas Adjust the solution to neutral or below to obtain SiO ₂ coated Fe ₃ O ₄ particles of magnetic particles, wherein the molar ratio of Fe ²⁺ to Fe ³⁺ in said iron salt is 1:(0.5～2.5 ), preferably 1:(1.5～2), the molar ratio of the ^OH- of the alkali to Σ(Fe ²⁺ +Fe ³⁺ ) is 1:(0.1～1.0), the sodium silicate and Fe ₃ The molar ratio of _O4 is 1: (0.043～5.2), preferably 1: (0.065～0.864);

2. Mix the aluminum hydroxide sol, the organic amine solution and the magnetic particles in step 1 at -10 to 35°C to form a uniformly dispersed water phase, and set the volume ratio of the water phase to the oil phase to be 1:( 3 to 20), preferably 1: (4 to 10), are dispersed in the oil phase to form water-in-oil droplets, then the heating system makes the aluminum hydroxide sol droplets in the water phase gel and solidify, and then through conventional The hydrothermal treatment, aging, drying and sintering process to obtain a spherical carrier material, wherein the volume ratio of the organic amine solution to the aluminum hydroxide sol is 1: (0.3 to 2.5);

3. Carrying out heat treatment on the carrier in a reducing atmosphere or an oxidizing atmosphere or treating the carrier with an oxidizing agent or a reducing agent, so as to change the core type in the magnetic particles of the carrier material.

In the preparation method of the spherical alumina support material provided by the present invention, the base mentioned in step 1 is selected from one of KOH, NaOH, NH ₄ OH, Na ₂ CO ₃ or NaHCO ₃ or a mixture thereof. Said acid is selected from one or their mixtures in sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, formic acid or acetic acid.

In step 2, the organic amine solution, aluminum hydroxide sol and magnetic particles are uniformly mixed to form an aqueous phase by means of stirring, shaking, ultrasonic dispersion, etc.; wherein the mass concentration of the organic amine solution is 12% to 40% , the organic amine refers to a substance whose pH value is close to neutral at normal temperature, but which can release alkaline substances after thermal decomposition, such as urea or hexamethylenetetramine, which can be used alone or in combination.

The volume ratio of the organic amine solution to the aluminum hydroxide sol in step 2 is 1: (0.3-2.5), preferably 1: (0.8-1.3). Said aluminum hydroxide sol, its preparation method can refer to: the method described in patents such as US. Dissolved in aluminum salt solutions such as halogen aluminum salts, aluminum sulfate, aluminum nitrate, etc. The aluminum/chlorine weight ratio in is controlled at 0.3～2.0, and the preferred range is 1.3～1.6.

Said oil is immiscible with water, its density is close to or less than the density of aqueous phase solution, and can be selected from one or more oils including gasoline, kerosene, diesel oil, transformer oil, benzene, biphenyl, halogenated hydrocarbons, etc. A mixture of species can be used alone or in combination.

In step 2, an emulsifier may also be added to the oil phase, and the amount of the emulsifier added is 0.02-2.0% by volume of the oil phase. Said emulsifier refers to low-molecular surfactants with hydrophilic-lipophilic balance (HLB value) <9, such as Span80 (sorbitan monooleate), Span85 (sorbitan trioleate) , Span65 (Sorbitan Tristearate), Span60 (Sorbitan Monostearate), Span40 (Sorbitan Monopalmitate), Span20 (Sorbitan Monolaurate) , polyethylene glycol 200 dioleate, ethylene glycol monostearate, glycerol monostearate, polyoxyethylene fatty acid ester, polyethylene glycol 400 distearate, lanolin, etc., can It is an emulsifier with an HLB value <9 obtained by combining one of them or several surfactants among them.

In step 2, the conventional hydrothermal treatment, aging, drying and sintering can refer to the content described in US. Pat. 2,620,314, US. Pat. 4,273,735 and other patent documents. Said hydrothermal treatment condition is to treat the solidified product of aluminum hydroxide sol droplets in an oil or water medium, preferably an oil medium, at 105-260°C, preferably 120-200°C, for 1-10 hours in an autoclave, preferably 2 to 5 hours.

The sintering treatment process is a process in which the alumina precursor formed by hydrothermal treatment, aging and drying is calcined at a corresponding temperature according to the requirements for the crystal form of the final product alumina. Said alumina precursor can be basic aluminum salt, amorphous aluminum hydroxide, alumina trihydrate, gibbsite, bayalite, gibbsite, alumina monohydrate, diaspore, bollite One of bauxite and boehmite or a mixture of them.

Step 3 is to reduce and oxidize the carrier material to transform the magnetic inner core of the magnetic component in the carrier to change the magnetic properties of the carrier material. The transformation law between the magnetic core Fe ₃ O ₄ , γ-Fe ₂ O ₃ and Fe is generally: the magnetic Fe ₃ O ₄ core is easily oxidized to γ-Fe ₂ O with weaker magnetic properties but stable performance under high temperature oxidizing atmosphere ₃ cores; and γ-Fe ₂ O ₃ cores can be reduced to Fe ₃ O ₄ cores in a reducing atmosphere around 300°C; Fe ₃ O ₄ or γ-Fe ₂ O ₃ cores can be reduced in a reducing atmosphere above 460°C Fe cores are obtained; in the case of insufficient reduction, the cores in the carrier may appear in the form of two or three cores coexisting; the carrier with the Fe ₃ O ₄ core is used in a higher temperature oxidizing atmosphere, partly Fe ₃ O ₄ will be oxidized to γ-Fe ₂ O ₃ , so that two forms of cores coexist in the support.

The spherical alumina carrier material provided by the invention has the following characteristics:

1. With good magnetic properties, SiO ₂ coated magnetic component particles are uniformly dispersed in alumina, in which the particle size of the magnetic inner core inside the coating is smaller than its critical spontaneous magnetization size, thus endowing the carrier with superparamagnetic characteristics , under the action of an external magnetic field, the positioning control, separation and recovery can be conveniently carried out in the reactor. When there is no external magnetic field, the particles do not magnetically aggregate, and the dispersion is good. Such characteristics make it possible to achieve the purpose of repeated recycling through the action of a magnetic field in the catalytic reaction, prevent the loss of catalyst or carrier material, and reduce the cost.

2. It has a special microstructure. The inner core is composed of iron or iron oxide magnetic core and the SiO ₂ coating layer firmly combined with the surface of the magnetic core to form magnetic particles. The relatively loose alumina component in the carrier forms a microstructure Gradients and ladders of components. Due to steric hindrance, the _SiO2 layer coated on the surface of iron or iron oxide improves the dispersion and stability of the core particles, and enhances its anti-corrosion and anti-oxidation properties; as a carrier material, the magnetic core does not Direct contact with the catalytically active components loaded in the subsequent application process can avoid the poisonous effect of the iron component on some catalysts, especially in the reaction of some acidic media, due to the protective effect of the SiO ₂ dense layer, the magnetic core group The fraction does not dissolve and the carrier is well tolerated.

Description of drawings

Fig. 1 is a schematic cross-sectional structure diagram of magnetic particles in a spherical alumina carrier material.

Fig. 2 is an XRD spectrum of magnetic particles in a spherical alumina carrier material.

Fig. 3 is a schematic cross-sectional structure diagram of a spherical alumina carrier material.

Figure 4 is a TEM photo of magnetic particles in a spherical alumina carrier material

FIG. 5 is the hysteresis loop of the magnetic particles in the spherical alumina carrier prepared in Example 1. FIG.

Fig. 6 is the hysteresis loops of spherical alumina carriers prepared in Examples 4, 5 and 6.

Figures 7 and 8 are the XRD spectra of the spherical alumina carriers prepared in Examples 4 and 9, respectively.

FIG. 9 is a SEM photo of the spherical alumina carrier prepared in Example 1.

FIG. 10 is a SEM photo of the spherical alumina carrier prepared in Example 4.

Detailed ways

The following examples will further illustrate the present invention, but the protection scope of the present invention is not limited by these examples.

In the example, the morphology of the sample was observed with a JSM-5800 scanning electron microscope and a H-8100 transmission electron microscope; the hysteresis curve of the sample was measured at room temperature with a Model-155 vibrating sample magnetometer, with a measurement range of 0-8 (kOe). X-ray diffraction (XRD) was carried out on D/Max-2400 Rigaku (Japan Rigaku) diffractometer, Cu target Kα ray, wavelength λ=1.54, scanning range 10-90°C.

Example 1

Dissolve 189g Na ₂ SiO ₃ ·9H ₂ O (Zhejiang Wenzhou Dongsheng Chemical Reagent Factory) in 800mL distilled water, slowly add 3mol/L HCl solution dropwise under stirring condition, adjust the pH value of the solution to 13, filter and set aside.

Add 23.4g FeCl ₃ 6H ₂ O (Beijing Chaoyang Tonghui Chemical Factory) and 8.6g FeCl ₂ 4H ₂ O (Beijing Shuanghuan Chemical Reagent Factory) into a 2-liter stirred reactor with 1000 mL of distilled water, under nitrogen Under protection, the temperature was raised to 85-90°C, and 30 mL of 25% NH ₃ ·H ₂ O solution was added during high-speed stirring, and after high-speed stirring for 3 minutes, the Fe ₃ O ₄ nanoparticle product was separated by a magnetic separator. Ultrasonically disperse the deposited product after cleaning in the above-mentioned pretreated Na ₂ SiO ₃ solution, then transfer it into a 2-liter stirred reactor, raise the temperature to 85°C, and slowly add a concentration of About 2mol/L HCl solution, adjust the pH value of the solution from 13 to 6. After the reaction, the product was separated and washed thoroughly to obtain SiO ₂ coated Fe ₃ O ₄ magnetic particles, marked as SF1.

The total weight of the magnetic particle product coated with Fe ₃ O ₄ particles is about 50 grams, which contains about 10 grams of Fe ₃ O ₄ and about 40 grams of SiO ₂ on the surface of Fe ₃ O ₄ , which is amorphous SiO ₂ . (SiO ₂ coating amount is about 400%). Observation by scanning electron microscope shows that the product is grape bunch-like (agglomerate) agglomerates with an average particle size of about 2 μm. Observation by transmission electron microscope shows that nano-Fe ₃ O ₄ magnetic particles are uniformly dispersed in the product, and the core Fe ₃ O ₄ magnetic particles are close to In spherical shape, the average particle size is 7 nanometers, and the periphery is covered by a dense SiO ₂ layer (see Figure 4, the black dots are nano-Fe ₃ O ₄ magnetic particles, and the light-colored objects are SiO ₂ coatings), through XRD The spectrogram (Fig. 2) found that there is a larger wave packet in the range of 2θ=20-30°, which is the characteristic peak of amorphous SiO ₂ . Shown by its hysteresis loop (Fig. 5), the magnetization curve and the demagnetization curve of the product coincide. When there is no external magnetic field (H=OkOe), the magnetization M=0. With the increase of the external magnetic field H, the total magnetization M increases rapidly until it reaches saturation, indicating that the magnetic particles have superparamagnetism, and the saturation magnetization is about 11emu/g (A·m ² /Kg).

Weigh 92.5 grams of AlCl ₃ 6H ₂ O (Tianjin Shuangchuan Chemical Reagent Factory), dissolve it in 600ml deionized water, heat to 80-100°C, slowly add 42.6 grams of high-purity aluminum foil (Beijing Xingjin Chemical Factory), and Keep at this temperature for 60-72 hours to fully dissolve the aluminum foil in the solution, then heat and concentrate the solution volume to 300ml to obtain a clear translucent sol, which is ready for use. The sol is composed of aluminum hydroxide and aluminum chloride (or basic aluminum chloride), wherein the aluminum/chlorine weight ratio is about 1.3:1.0, and the aluminum in the sol is converted into about 100 grams of aluminum oxide. This sol is labeled A1.

At room temperature, measure 100ml of A1 aluminum hydroxide sol, mix with 95ml of hexamethylenetetramine (Beijing Yili Fine Chemicals Co., Ltd.) with a concentration of 120g/L 10°C, stir well, then add 1.75g of SF1, stir A homogeneous aqueous solution was formed. Load 1400ml of sulfonated kerosene containing 0.05% by volume Span80 (Beijing Chemical Reagent Company) into a 3-liter cylindrical stirred reactor, add the above-mentioned aqueous phase solution into the sulfonated kerosene, and disperse evenly at room temperature at a rotating speed of 800rpm , to form a water-in-oil emulsion, and then raise the temperature of the system to 85-90°C and keep it for 15 minutes. At this time, the organic amine decomposes to release ammonia, and the pH value of the aqueous phase solution gradually increases, so that the aluminum hydroxide sol gels and solidifies into a magnetic spherical shape Al(OH) ₃ .

After the magnetic spherical Al(OH) ₃ product is cleaned and degreased, it is aged in 7 wt% ammonia water at room temperature for 6 hours, and after drying at 60°C, the gibbsite structure (β-Al ₂ O ₃ ·3H ₂ O) magnetic Al(OH) ₃ particles, the product is sintered in air at 400°C for 2 hours, and about 40g of magnetic spherical η-Al ₂ O ₃ carrier containing γ-Fe ₂ O ₃ magnetic inner core can be obtained.

The morphology photo of the prepared spherical alumina support material is shown in Fig. 9. It can be seen from Fig. 9 that the average particle size of the material is about 140 μm.

The content ratio (weight ratio) of each component in the carrier is: γ-Fe ₂ O ₃ :SiO ₂ : _{Al 2} O ₃ =1:4:95 (in addition, the carrier also contains part of water). This carrier has superparamagnetic characteristics.

Example 2

Dissolve 28.4g Na ₂ SiO ₃ 9H ₂ O (Zhejiang Wenzhou Dongsheng Chemical Reagent Factory) in 600mL distilled water, slowly add 3mol/L HCl solution dropwise under stirring condition, adjust the pH value of the solution to 13, filter and set aside .

Add 46.7g FeCl ₃ 6H ₂ O (Beijing Chaoyang Tonghui Chemical Factory) and 17.2g FeCl ₂ 4H ₂ O (Beijing Shuanghuan Chemical Reagent Factory) to a 2-liter stirred reactor with 1000 mL of distilled water, under nitrogen Under protection, the temperature was raised to 85-90°C, and 160 mL of 6MolL NaOH solution was added during high-speed stirring, and after high-speed stirring for 3 minutes, the Fe ₃ O ₄ nanoparticle product was separated by a magnetic separator. Ultrasonically disperse the deposited product after cleaning in the above-mentioned pretreated Na ₂ SiO ₃ solution, then transfer it into a 2-liter stirred reactor, raise the temperature to 85°C, and slowly add a concentration of About 1.5mol/L HCl solution, the pH value of the solution was adjusted from 13 to 6 within about 3 hours. The magnetic particles of SiO ₂ coated Fe ₃ O ₄ particles were obtained, marked as SF2.

The total weight of the above-mentioned SiO ₂ coated Fe ₃ O ₄ particles is about 26 grams, which contains about 20 grams of Fe ₃ O ₄ and about 6 grams of SiO ₂ on the surface of Fe ₃ O ₄ , which is amorphous SiO ₂ . (SiO ₂ coating amount is about 30%). The magnetic hysteresis loop detected by the vibrating sample magnetometer (VSM) shows that the magnetic particles have superparamagnetism.

Weigh 75.1 grams of AlCl ₃ 6H ₂ O (Tianjin Shuangchuan Chemical Reagent Factory), dissolve it in 600ml of deionized water, heat to 80-100°C, slowly add 44.6 grams of 300-mesh fine aluminum powder (product of Institute of Mechanics, Chinese Academy of Sciences) in batches , kept at this temperature for 48 hours. After the aluminum powder was fully dissolved in the solution, the volume of the solution was heated and concentrated to 300ml to obtain a clear translucent sol, wherein the aluminum/chlorine weight ratio was about 1.6:1.0, and the sol The aluminum in it is converted into alumina to be about 100 grams. This sol is labeled A2.

At room temperature, measure 100ml of A2 aluminum hydroxide sol, mix with 80mL of hexamethylenetetramine (Beijing Yili Fine Chemicals Co., Ltd.) with a concentration of 400g/L and 10°C, stir well, then add 21.3g of SF2, stir A homogeneous aqueous solution was formed. 1300ml of sulfonated kerosene containing 0.02% by volume of Span60 (Qingming Chemical Plant, distributed by Beijing Purchasing and Supply Station of China Pharmaceutical Company) is loaded into 3 liters of cylindrical stirred reactor, the above-mentioned aqueous phase solution is added in the sulfonated kerosene, at room temperature At the speed of 400rpm, disperse evenly to form a water-in-oil emulsion, then raise the temperature of the system to 85-90°C, keep it for 15 minutes, cool down, and separate the product to obtain magnetic spherical Al(OH) ₃ . Marked as AL1.

The above-mentioned AL1 magnetic spherical Al(OH) ₃ product was washed with a solution containing a small amount of Tween80 to remove surface slick oil, aged in dilute ammonia water with pH=10 (measured at room temperature) at 80°C for 4 hours (to remove some of the impurities), After drying at 60°C, magnetic Al(OH) ₃ microspheres with an amorphous structure can be obtained. After sintering the product at 350°C for 2 hours in a hydrogen atmosphere, about 65 g of magnetic spherical amorphous particles containing Fe ₃ O ₄ magnetic cores can be obtained. Structured Al ₂ O ₃ support. The average particle size of the carrier material is about 1 mm, and the content ratio (weight ratio) of each component is: Fe ₃ O ₄ : SiO ₂ : Al ₂ O ₃ =30:9:61 (in addition, the carrier also contains part of water ). This carrier has superparamagnetic characteristics.

Example 3

Put the above-mentioned AL1 magnetic spherical Al(OH) ₃ product into a 1L autoclave containing 0.7L sulfonated kerosene medium, and conduct a hydrothermal treatment at 140°C for 3 hours under the protection of nitrogen. After aging in ammonia water (measured at room temperature) at 80°C for 6 hours (to remove some impurities), and drying at 60°C, a magnetic spherical Al(OH) _product with a boehmite structure (α-AlOOH) can be obtained. The product was sintered at 580° C. for 2 hours in an air atmosphere, and about 60 g of a spherical γ-Al ₂ O ₃ carrier containing a γ-Fe ₂ O ₃ magnetic core could be obtained. The content ratio (weight ratio) of each component in the carrier material is: γ-Fe ₂ O ₃ :SiO ₂ :Al ₂ O ₃ =30:9:61 (in addition, the carrier also contains part of water). This carrier has superparamagnetic characteristics.

Example 4

Dissolve 189g Na ₂ SiO ₃ ·9H ₂ O (Zhejiang Wenzhou Dongsheng Chemical Reagent Factory) in 1000mL distilled water, slowly add 3mol/L HCl solution dropwise under stirring condition, adjust the pH value of the solution to 13, filter and set aside.

Add 42.2g FeCl _{6H 2} O (Beijing Chaoyang Tonghui Chemical Plant) and 20.6g FeCl _{4H 2} O (Beijing Shuanghuan Chemical Reagent Factory) in the 3 liters of stirring reactor that 1200mL distilled water is housed, heat up to 85-90°C, add 60 mL of 25% NH ₃ ·H ₂ O solution during high-speed stirring, and after high-speed stirring for 3 minutes, use a magnetic separator to separate the Fe ₃ O ₄ nanoparticle product. Ultrasonically disperse the deposited product after cleaning in the above-mentioned pretreated Na ₂ SiO ₃ solution, then transfer it into a 3-liter stirred reactor, raise the temperature to 85°C, and slowly add a concentration of About 2mol/L HCl solution, the pH value of the solution was adjusted from 13 to 6 within about 3 hours. The magnetic particles of SiO ₂ coated Fe ₃ O ₄ particles were obtained.

The total weight of the above product magnetic particles is about 60 grams, which contains about 20 grams of Fe ₃ O ₄ and about 40 grams of SiO ₂ on the surface of Fe ₃ O ₄ , which is amorphous SiO ₂ . (SiO ₂ coating amount is about 200%). The magnetic hysteresis loop detected by the vibrating sample magnetometer (VSM) shows that the magnetic particles have superparamagnetism. This component is labeled SF3.

Weigh 80 grams of AlCl ₃ 6H ₂ O (Tianjin Shuangchuan Chemical Reagent Factory), dissolve it in 600ml deionized water, add 44 grams of high-purity aluminum foil (Beijing Xingjin Chemical Factory), and keep at 80-100°C for 60 -72 hours, after the aluminum foil is fully dissolved in the solution, the volume of the solution is heated and concentrated to 300ml to obtain a clear and translucent sol, wherein the weight ratio of aluminum/chlorine is about 1.5:1.0, and the aluminum in the sol is converted into alumina about for 100 grams. This sol is labeled A3.

At a temperature of 10°C, measure 100ml A3 aluminum hydroxide sol, and 90ml of organic amine solution (containing hexamethylenetetramine (Beijing Yili Fine Chemical Company) 300g/L and urea (Beijing Chemical Plant) 150g/L L) mixing, stirring evenly, then adding 7.3 grams of SF3 coated magnetic component particles, stirring to form a uniform aqueous solution. Load 1600ml of sulfonated kerosene containing 0.05% by volume Span80 (Beijing Chemical Reagent Company) into a 3-liter cylindrical stirred reactor, add the above-mentioned aqueous phase solution into the sulfonated kerosene, and disperse evenly at room temperature at a rotating speed of 700rpm , forming a water-in-oil emulsion, then raising the temperature of the system to 85-90° C., keeping it for 15 minutes, cooling, and separating the product to obtain magnetic spherical Al(OH) ₃ . Marked as AL2.

Put the above-mentioned magnetic spherical Al(OH) ₃ product of AL2 into a 1L autoclave containing 0.7L sulfonated kerosene medium, and conduct a hydrothermal treatment at 180°C for 2 hours under the protection of nitrogen. Aged in dilute ammonia water (measured at room temperature) at 80°C for 5 hours (to remove some of the impurities), and dried at 60°C, a magnetic spherical Al(OH) ₃ product with a boehmite structure (α-AlOOH) could be obtained . Marked as AL3. The XRD spectrum of the product is shown in Figure 7. The product is composed of α-AlOOH, Fe ₃ O ₄ and γ-Fe ₂ O _3. During the hydrothermal treatment, aging and drying process, the Fe ₃ O ₄ in the product is partially oxidized It is γ-Fe ₂ O ₃ .

The above-mentioned boehmite product AL3 is sintered in an air atmosphere at 580°C for 2 hours, and about 45 g of spherical γ-Al _{2 O 3 carriers containing γ-Fe 2 O 3 magnetic} cores can be obtained;

The average particle size of the carrier material is about 200 μm (Figure 10), and the content ratio (weight ratio) of each component is: γ-Fe ₂ O ₃ : SiO ₂ : _{Al 2} O ₃ = 6: 12: 82, measured by VSM , the carrier has superparamagnetic characteristics, and the specific saturation magnetization is 2.97A·m ² /Kg. The -●- curve in Figure 6 is the hysteresis loop of the carrier. As determined by the BET adsorption method, the specific surface of the carrier is about 200+10m ² /g, and the pore volume is about 0.75±0.1mL/g.

Example 5

Other conditions are the same as in Example 4, the difference is that the amount of SF3 coated magnetic component particles added to the system is adjusted to 3.3 grams, and about 40 g of spherical γ-Al ₂ O ₃ containing γ-Fe ₂ O ₃ magnetic cores can be obtained The carrier, wherein the content ratio (weight ratio) of each component is: γ-Fe ₂ O ₃ : SiO ₂ : Al ₂ O ₃ = 3: 6: 91, as determined by VSM, the carrier has superparamagnetic characteristics, and the specific saturation magnetization is 1.78A·m ² /Kg, and the -■-curve in Figure 6 is the hysteresis loop of the carrier.

Example 6

Other conditions are the same as in Example 4, except that the amount of SF3 coated magnetic component particles added to the system is adjusted to 12.3 grams, and about 50 g of spherical γ-Al ₂ O ₃ containing γ-Fe ₂ O ₃ magnetic cores can be obtained The carrier, wherein the content ratio (weight ratio) of each component is: γ-Fe ₂ O ₃ : SiO ₂ : Al ₂ O ₃ = 9: 18: 73, measured by VSM, the carrier has superparamagnetic characteristics, and the specific saturation magnetization It is 5.03A·m ² /Kg. The -▲-curve in Figure 6 is the hysteresis loop of the carrier.

Example 7

Other conditions are the same as in Example 4, except that the obtained boehmite product AL3 is sintered in an air atmosphere at 920°C for 2 hours, and about 42 g of a magnetic spherical δ-Al ₂ O ₃ carrier containing a γ-Fe ₂ O ₃ magnetic core can be obtained (which contains a small amount of θ-Al ₂ O ₃ ), the content ratio (weight ratio) of each component is: γ-Fe ₂ O ₃ : SiO ₂ : _{Al 2} O ₃ = 6: 12: 82, measured by VSM, The carrier has superparamagnetic characteristics.

Example 8

At room temperature, measure 100ml of A3 aluminum hydroxide sol, mix with 120mL of organic amine solution (containing hexamethylenetetramine (Beijing Yili Fine Chemicals Company) 400g/L) at 10°C, stir evenly, and then add 33g SF3-coated magnetic component particles, stirred to form a uniform aqueous solution. 1500ml of sulfonated kerosene containing 0.07vol.% Span80 (Beijing Chemical Reagent Company) is loaded into a 3-liter cylindrical stirred reactor, the above-mentioned aqueous phase solution is added in the sulfonated kerosene, and at room temperature at a rotating speed of 800rpm, disperse homogeneous, forming a water-in-oil emulsion, then raising the temperature of the system to 85-90°C and keeping it for 15 minutes to obtain magnetic spherical Al(OH) ₃ .

After cleaning and degreasing the magnetic spherical Al(OH) ₃ product, aging it in 7wt.% ammonia water at room temperature for 6 hours, and drying at 60°C, the gibbsite structure (β-Al ₂ O ₃ · 3H ₂ O) magnetic Al(OH) ₃ particles, the product is sintered in air at 920°C for 2 hours, and about 68g of spherical θ-Al ₂ O ₃ carrier containing γ-Fe ₂ O ₃ magnetic core can be obtained. The content ratio (weight ratio) of each component in the carrier is: γ-Fe ₂ O ₃ :SiO ₂ :Al ₂ O ₃ =16.7:33.3:50 (in addition, the carrier also contains part of water). This carrier has superparamagnetic characteristics.

Example 9

With the spherical Al(OH) product _AL2 obtained in Example 4, after cleaning and removing the slick oil on the surface, aging in 7% ammonia water at room temperature for 5 hours, after fully cleaning with deionized water, drying. The main components of the product at this time are gibbsite, SiO ₂ and Fe ₃ O ₄ . The product was sintered at 1180° C. for 2 hours under the protection of nitrogen to obtain about 41 g of spherical α-Al ₂ O ₃ supports containing metal Fe magnetic cores. The weight ratio of α-Al ₂ O ₃ in the support is about 82%. The XRD spectrum is shown in Figure 8, and it can be seen from Figure 8 that the carrier is mainly composed of α-Al ₂ O ₃ , SiO ₂ , aluminum silicate, and metallic iron. At high temperature, the residual organic amine in the particles decomposes to form a reducing atmosphere, which reduces the magnetic nano-Fe ₃ O ₄ core to a metal Fe core, and part of the SiO ₂ on the surface of Fe ₃ O ₄ reacts with Al ₂ O ₃ to form A small amount of aluminum silicate. The VSM test results show that the carrier has obvious superparamagnetic characteristics, and the specific saturation magnetization is about 7.0A·m ² /Kg.

Claims (24)

1. A spherical alumina carrier material, characterized in that the carrier material contains 50-99% by weight of alumina and 1-50% by weight of magnetic particles, wherein said magnetic particles have a weight ratio of 0.01-6:1 The SiO ₂ cladding layer and one or more inner cores selected from Fe ₃ O ₄ , Fe and γ-Fe ₂ O ₃ . 2. The carrier material according to claim 1, characterized in that said alumina is selected from one or more of the following mixtures: amorphous alumina, ρ-alumina, χ-alumina, η - Alumina, γ-alumina, κ-alumina, δ-alumina, θ-alumina, α-alumina. 3. The carrier material according to claim 1, characterized in that said magnetic particles consist of a coating layer and an inner core in a weight ratio of 0.3-4.0:1. 4. The carrier material according to claim 1 or 3, characterized in that the inner core of the magnetic particles is one or more single-domain superparamagnetic particles with a diameter of 3-30 nm. 5. The alumina support material according to claim 1, characterized in that the support material has a particle size of 10 μm to 6 mm. 6. The method for preparing spherical alumina carrier material according to claim 1, characterized in that the method comprises the following steps: (1) At 50-100°C, add alkali to the aqueous solution containing Fe ²⁺ and Fe ³⁺ salts, transfer the deposited nano-Fe ₃ O ₄ particles into sodium silicate solution, under the protection of inert gas, add acid to adjust the solution to neutral or below neutral to obtain SiO ₂ coated Fe ₃ O ₄ particles of magnetic particles, wherein the molar ratio of Fe ²⁺ to Fe ³⁺ in said iron salt is 1:(0.5～ 2.5), the molar ratio of ^OH- of said alkali to Σ(Fe ²⁺ +Fe ³⁺ ) is 1: (0.1～1.0), and the molar ratio of said sodium silicate to Fe ₃ O ₄ is 1: (0.043～5.2); (2) Mix aluminum hydroxide sol, organic amine solution, and magnetic particles in step (1) at -10 to 35°C to form a uniformly dispersed water phase, which is then dispersed in the oil phase to form an oil-in-oil phase After the water-type droplets, the heating system makes the aluminum hydroxide sol droplets in the water phase gel and solidify, and then undergoes conventional hydrothermal treatment, aging, drying and sintering. Among them, the volume ratio of the organic amine solution to the aluminum hydroxide sol 1: (0.3-2.5), the volume ratio of the water phase and the oil phase is 1: (3-20); (3) Carrying out heat treatment on the carrier in a reducing atmosphere or an oxidizing atmosphere or treating the carrier with an oxidizing agent or a reducing agent, so that the type of core in the magnetic particles of the carrier material is changed. 7. The method according to claim 6, characterized in that the base in step (1) is selected from one of KOH, NaOH, NH ₄ OH, Na ₂ CO ₃ or NaHCO ₃ or a mixture thereof. 8. The method according to claim 6, characterized in that in the iron salt in step (1), the molar ratio of Fe ²⁺ to Fe ³⁺ is 1: (1.5-2). 9. The method according to claim 6, characterized in that the molar ratio of sodium silicate to Fe ₃ O ₄ in step (1) is 1: (0.065-0.864). 10. The method according to claim 6, characterized in that the acid in step (1) is selected from sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, formic acid or acetic acid, or a mixture thereof. 11. The method according to claim 6, characterized in that the aluminum/chlorine weight ratio in the aluminum hydroxide sol in step (2) is 0.3-2.0. 12. The method according to claim 11, characterized in that the aluminum/chlorine weight ratio in the aluminum hydroxide sol in step (2) is 1.3-1.6. 13. The method according to claim 6, characterized in that the mass concentration of said organic amine solution in step (2) is 12%-40%. 14. The method according to claim 6, characterized in that the organic amine in step (2) is a substance whose pH value is close to neutral at room temperature, but which can release alkaline substances after thermal decomposition, which can be used alone or in combination use. 15. The method according to claim 14, characterized in that said organic amine is urea and/or hexamethylenetetramine. 16. The method according to claim 6, characterized in that the volume ratio of the organic amine solution to the aluminum hydroxide sol in step (2) is 1: (0.8-1.3). 17. The method according to claim 6, characterized in that the oil phase in step (2) is selected from one or more of gasoline, kerosene, diesel oil, transformer oil, benzene, biphenyl, and halogenated hydrocarbons mixture. 18. The method according to claim 6, characterized in that the volume ratio of the water phase to the oil phase in step (2) is 1: (4-10). 19. The method according to claim 6, characterized in that said oil phase in step (2) also contains 0.02-2.0% by volume of emulsifier. 20. The method of claim 19, wherein said emulsifier is one or more low molecular weight surfactants. 21. The method of claim 20, wherein said surfactant has a hydrophilic-lipophilic balance <9. 22. The method according to claim 20 or 21, characterized in that said surfactant is selected from Span80, Span85, Span65, Span60, Span40, Span20, polyethylene glycol 200 dioleate, ethylene glycol mono Stearate, Glyceryl Monostearate, Polyoxyethylene Fatty Acid Ester, Macrogol 400 Distearate, Lanolin. 23. The method according to claim 6, characterized in that the hydrothermal treatment process in step (2) is carried out in an autoclave, and the solidified product of aluminum hydroxide sol droplets is placed in an oil or water medium for 105 ~ Treat at 260°C for 1 to 10 hours. 24. The method according to claim 23, characterized in that the hydrothermal treatment process in step (2) is carried out in an autoclave, and the product obtained by gelling and solidifying the aluminum hydroxide sol droplets is placed in an oil medium at 120-200°C Treat for 2 to 5 hours.

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