Preparation method of hemispherical alumina catalyst carrier

Abstract

The invention discloses a preparation method of a hemispherical aluminum oxide catalyst carrier, which comprises the following steps: by taking a spherical aluminum oxide catalyst carrier prepared by an oil column forming method as a precursor, modifying the precursor by using a calcium hydroxide aqueous solution, and then filling pores of the precursor by using a monosaccharide aqueous solution to modify a pore structure, thereby obtaining the hemispherical aluminum oxide catalyst carrier. And finally, soaking with a carbon dioxide aqueous solution to enable the original spherical aluminum oxide catalyst carrier to naturally crack into two hemispheres, and finally, washing, drying and roasting to obtain the hemispherical aluminum oxide catalyst carrier. The method is simple to operate, the yield of the hemispherical aluminum oxide catalyst carrier reaches 98% or above, the method has the advantages of being efficient, practical, high in yield and the like, industrial production can be achieved, the hemispherical aluminum oxide catalyst carrier retains the physical characteristics of an original spherical aluminum oxide carrier, and meanwhile the outer specific surface area is increased by 50%.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst carrier preparation, and particularly relates to a method for preparing a hemispherical alumina catalyst carrier. Background Art

[0002] The appearance of multiphase catalysts usually comes in two forms: powder and granular. Powdered catalysts are mostly used in intermittent kettle reactors, while granular catalysts are mostly used in fixed bed reactors. According to the requirements of different processes and application scenarios, the particles of fixed bed catalysts have various shapes and sizes. Common shapes of granular catalysts are mainly: spherical, cylindrical, annular, pressed tablets, mesh, irregular and strip-shaped. Common methods for forming granular catalysts include: tableting, extrusion, rolling, agglomeration into balls and spraying. In addition, the formed catalysts can be crushed and screened to obtain irregular granular catalysts with a certain particle size.

[0003] For fixed bed reactors of gas-liquid-solid three-phase reactions, catalyst particles of different shapes have different porosity and bulk density, which affects the flow characteristics of the liquid and gas phases. In a typical trickle bed reactor, the liquid phase flows over the surface of the catalyst particles in the form of a liquid film. The shape of the catalyst affects the thickness distribution and flow curve of the liquid film. Similarly, the gas phase flowing over the catalyst surface is also affected by the shape of the catalyst. The full contact between the liquid and gas phases on the catalyst surface directly affects the effect of the catalytic reaction.

[0004] The accumulation of spherical particles can obtain a relatively large packing density and a small porosity. The filling and stacking of spherical catalysts are closer to dense phase filling, the stacking is more compact, the bed resistance and pressure drop are higher, the gaps in the bed are more uniform, which is conducive to the distribution of gas and liquid, and there is almost no bridging problem. Therefore, spherical particle catalysts are widely used. In the bed of spherical particle catalysts, the flow characteristics of the material on the catalyst surface are single, and the flow path and curve are both arcs. Hemispherical catalyst particles of the same diameter can maintain the characteristics of spherical catalyst particles to the maximum extent, increasing the surface area of ​​the catalyst by 50% (because the surface area of ​​the sphere is 4πr 2 , the spherical catalyst splits into two hemispheres, increasing the area of ​​the two circles by 2πr 2 . ), and also provide a plane for the linear flow of materials, obtaining two flow characteristics. However, due to the limitations of processing methods and difficulty, it is difficult to realize the industrial application of hemispherical particle catalysts. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a method for preparing a hemispherical alumina particle catalyst carrier with simple operation and high yield.

[0006] The method for preparing the hemispherical alumina particle catalyst carrier provided by the present invention comprises the following steps:

[0007] Step 1: Use the spherical alumina catalyst carrier prepared by the oil column molding method as a precursor, spray the calcium hydroxide aqueous solution evenly on the surface of the precursor to completely cover the precursor, and then keep it for 30 to 50 minutes, place the solid-liquid mixture in a centrifuge for solid-liquid separation, collect the modified precursor and dry it.

[0008] Step 2: Spray the pore-filling agent aqueous solution evenly on the surface of the modified precursor to completely wet the modified precursor, let it stand for 30 to 50 minutes, then transfer it to a centrifuge for drying, and finally place it in a drying and roasting integrated furnace for heat treatment; wherein the pore-filling agent aqueous solution is a monosaccharide aqueous solution.

[0009] Step 3: Soak the heat-treated precursor with a carbon dioxide aqueous solution, and the spherical alumina catalyst carrier naturally splits into two hemispheres. Then transfer the solid-liquid mixture to a centrifuge for solid-liquid separation, and then wash it with deionized water until the conductivity of the washing water is less than 300uS / cm. The obtained solid is transferred to a drying and roasting integrated furnace for heat treatment to obtain a hemispherical alumina catalyst carrier.

[0010] In the above step 1, the size of the spherical alumina catalyst carrier prepared by the oil column molding method is 1.5 to 3 mm, and the specific surface area is 70 to 210 m 2 / g, the pore volume is 0.5~0.7mL / g, and the pore diameter is 12~29nm.

[0011] In the above step 1, the mass concentration of the calcium hydroxide aqueous solution is preferably 0.08% to 0.11%.

[0012] In the above step 1, the drying temperature is preferably 100 to 120° C., and the drying time is 5 to 9 hours.

[0013] In the above step 2, preferably the monosaccharide is any one or two of glucose, galactose and mannose.

[0014] In the above step 2, it is further preferred that the mass concentration of the monosaccharide aqueous solution is 5% to 9%.

[0015] In the above step 2, the heat treatment is first drying at 100-120° C. for 5-9 hours, and then carbonizing at a constant temperature of 600-800° C. for 4-6 hours in a nitrogen atmosphere.

[0016] In the above step 3, the mass concentration of the carbon dioxide aqueous solution is preferably 0.08% to 0.11%.

[0017] In the above step 3, the heat treatment is first drying at 120-150° C. for 5-9 hours, and then calcining at a constant temperature of 500-600° C. for 4-8 hours in an air atmosphere.

[0018] The beneficial effects of the present invention are as follows:

[0019] The present invention uses a spherical alumina catalyst carrier prepared by an oil column forming method as a precursor, and after the precursor is modified by a calcium hydroxide aqueous solution, a monosaccharide is used as a filler to fill its pores and then heat-treated to transform its pore structure, and finally soaked in a carbon dioxide aqueous solution and stirred to allow it to quickly absorb water, generate a large amount of adsorption heat, so that a small amount of water adsorbed in the pores is quickly gasified, thereby cracking the spherical precursor, so that the originally spherical alumina catalyst carrier naturally cracks into two hemispheres. The method of the present invention is simple to operate, and the yield of the hemispherical alumina catalyst carrier is more than 98%. It has the advantages of high efficiency, practicality, high yield, etc., and can be industrially produced. The hemispherical alumina catalyst carrier retains the physical properties of the original spherical alumina carrier, while increasing the external specific surface area by 50%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 These are optical images of the spherical alumina catalyst support (left) and the hemispherical alumina catalyst support (right) in Example 3. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0022] Example 1

[0023] Step 1: Prepared by oil column molding method with a size of 1.5 mm and a specific surface area of ​​80 m 2 / g, a pore volume of 0.63mL / g, and a pore size of 29nm are used as a precursor. 100g of a calcium hydroxide aqueous solution with a mass concentration of 0.09% is slowly and evenly sprayed on 100g of the precursor and maintained for 30min. Then the solid-liquid mixture is placed in a centrifuge for solid centrifugation to remove excess calcium hydroxide aqueous solution. The modified precursor (with calcium hydroxide adsorbed) is collected and placed in an oven at 120°C for drying for 5h.

[0024] Step 2: Slowly and evenly spray 100g of 7% glucose aqueous solution on the precursor modified in step 1, let it stand for 30 minutes, then transfer it to a centrifuge for drying, and finally place it in a drying and roasting integrated furnace for heat treatment. The heat treatment is first dried at 120°C for 5 hours, then heated to 800°C in a nitrogen atmosphere, and carbonized at a constant temperature for 4 hours.

[0025] Step 3: The precursor after the heat treatment in step 2 is quickly put into 100g of a carbon dioxide aqueous solution with a mass concentration of 0.09%, and is gently stirred to allow the precursor to absorb water quickly, generating a large amount of adsorption heat, so that the small amount of water adsorbed in the pores is quickly vaporized, thereby cracking the spherical precursor and naturally cracking it into two hemispheres; then the solid-liquid mixed solution is placed in a centrifuge for solid-liquid separation, and then fully washed with deionized water until the conductivity of the washing water is less than 300uS / cm. The obtained solid is transferred to a drying and roasting integrated furnace for heat treatment. The heat treatment is first dried at 130°C for 9h, then heated to 500°C in an air atmosphere, and roasted at a constant temperature for 8h, and finally a hemispherical alumina catalyst carrier is obtained with a yield of 98.5%.

[0026] Example 2

[0027] Step 1: Prepared by oil column molding method with a size of 3 mm and a specific surface area of ​​210 m 2 / g, a pore volume of 0.5mL / g, and a pore size of 12nm are used as a precursor. 150g of a calcium hydroxide aqueous solution with a mass concentration of 0.08% is slowly and evenly sprayed on 100g of the precursor and maintained for 30min. Then the solid-liquid mixture is placed in a centrifuge for solid centrifugation to remove excess calcium hydroxide aqueous solution. The modified precursor (with calcium hydroxide adsorbed) is collected and placed in an oven at 100°C for drying for 9h.

[0028] Step 2: Slowly and evenly spray 130g of a monosaccharide aqueous solution with a total mass concentration of 9% (the monosaccharide is a mixture of glucose and mannose in a mass ratio of 1:1) on the precursor modified in step 1, let it stand for 30 minutes, then transfer it to a centrifuge for drying, and finally place it in a drying and roasting integrated furnace for heat treatment. The heat treatment is first dried at 100°C for 9 hours, then heated to 700°C in a nitrogen atmosphere, and carbonized at a constant temperature for 5 hours.

[0029] Step 3: The precursor after the heat treatment in step 2 is quickly put into 100g of a carbon dioxide aqueous solution with a mass concentration of 0.08%, and is gently stirred to allow the precursor to absorb water quickly, generating a large amount of adsorption heat, so that the small amount of water adsorbed in the pores is quickly vaporized, thereby cracking the spherical precursor and naturally cracking it into two hemispheres; then the solid-liquid mixed solution is placed in a centrifuge for solid-liquid separation, and then fully washed with deionized water until the conductivity of the washing water is less than 300uS / cm. The obtained solid is transferred to a drying and roasting integrated furnace for heat treatment. The heat treatment is first dried at 150°C for 5h, then heated to 550°C in an air atmosphere, and calcined at a constant temperature for 6h, and finally a hemispherical alumina catalyst carrier is obtained with a yield of 99.2%.

[0030] Example 3

[0031] Step 1: Prepared by oil column molding method with a size of 2 mm and a specific surface area of ​​70 m 2 / g, a pore volume of 0.7mL / g, and a pore size of 20nm are used as a precursor. 130g of a calcium hydroxide aqueous solution with a mass concentration of 0.11% is slowly and evenly sprayed on 100g of the precursor and maintained for 30min. Then the solid-liquid mixture is placed in a centrifuge for solid centrifugation to remove excess calcium hydroxide aqueous solution. The modified precursor (with calcium hydroxide adsorbed) is collected and placed in an oven at 110°C for drying for 7h.

[0032] Step 2: Slowly and evenly spray 100g of 5% mass concentration galactose aqueous solution on the precursor modified in step 1, let it stand for 30 minutes, then transfer it to a centrifuge for drying, and finally place it in a drying and roasting integrated furnace for heat treatment. The heat treatment is first dried at 110°C for 7h, then heated to 600°C in a nitrogen atmosphere, and carbonized at a constant temperature for 6h.

[0033] Step 3: Quickly put the precursor after the heat treatment in step 2 into 100g of a carbon dioxide aqueous solution with a mass concentration of 0.11%, and stir it slightly to make the precursor absorb water quickly, generating a large amount of adsorption heat, so that the small amount of water adsorbed in the pores is quickly vaporized, thereby cracking the spherical precursor and naturally splitting it into two hemispheres; then place the solid-liquid mixed solution in a centrifuge for solid-liquid separation, and then wash it thoroughly with deionized water until the conductivity of the washing water is less than 300uS / cm. The obtained solid is transferred to a drying and roasting integrated furnace for heat treatment. The heat treatment is first dried at 120°C for 7h, then heated to 600°C in an air atmosphere, and roasted at a constant temperature for 4h. Finally, a hemispherical alumina catalyst carrier is obtained with a yield of 99.0%. Figure 1 It can be seen that the prepared hemispherical alumina carrier particles are relatively uniform, and the original spherical carrier is just split into two halves.

Claims

1. A method for preparing a hemispherical alumina catalyst carrier, characterized in that: The preparation method comprises the following steps: Step 1: Using a spherical alumina catalyst carrier prepared by an oil column molding method as a precursor, spraying a calcium hydroxide aqueous solution evenly on the surface of the precursor so that the calcium hydroxide aqueous solution completely covers the precursor, and then maintaining it for 30 to 50 minutes, placing the solid-liquid mixture in a centrifuge for solid-liquid separation, and collecting the modified precursor and drying it; Step 2: spraying the pore-filling agent aqueous solution evenly on the surface of the modified precursor to completely wet the modified precursor, leaving it to stand for 30 to 50 minutes, then transferring it to a centrifuge for drying, and finally placing it in a drying and roasting integrated furnace for heat treatment; wherein the pore-filling agent aqueous solution is a monosaccharide aqueous solution; Step 3: Soak the heat-treated precursor with a carbon dioxide aqueous solution, and the spherical alumina catalyst carrier naturally splits into two hemispheres. Then transfer the solid-liquid mixture to a centrifuge for solid-liquid separation, and then wash it with deionized water until the conductivity of the washing water is less than 300uS / cm. The obtained solid is transferred to a drying and roasting integrated furnace for heat treatment to obtain a hemispherical alumina catalyst carrier.

2. The method for preparing a hemispherical alumina catalyst carrier according to claim 1, characterized in that: In step 1, the spherical alumina catalyst carrier prepared by the oil column molding method has a size of 1.5 to 3 mm and a specific surface area of ​​70 to 210 m 2 / g, the pore volume is 0.5~0.7mL / g, and the pore diameter is 12~29nm.

3. The method for preparing a hemispherical alumina catalyst carrier according to claim 1, characterized in that: In step 1, the mass concentration of the calcium hydroxide aqueous solution is 0.08% to 0.11%.

4. The method for preparing a hemispherical alumina catalyst carrier according to claim 1, characterized in that: In step 1, the drying temperature is 100-120° C., and the drying time is 5-9 hours.

5. The method for preparing a hemispherical alumina catalyst carrier according to claim 1, characterized in that: In step 2, the monosaccharide is selected from any one or two of glucose, galactose and mannose.

6. The method for preparing a hemispherical alumina catalyst carrier according to claim 1 or 5, characterized in that: In step 2, the mass concentration of the monosaccharide aqueous solution is 5% to 9%.

7. The method for preparing a hemispherical alumina catalyst carrier according to claim 1, characterized in that: In step 2, the heat treatment is first drying at 100-120° C. for 5-9 hours, and then carbonizing at a constant temperature of 600-800° C. for 4-6 hours in a nitrogen atmosphere.

8. The method for preparing a hemispherical alumina catalyst carrier according to claim 1, characterized in that: In step 3, the mass concentration of the carbon dioxide aqueous solution is 0.08% to 0.11%.

9. The method for preparing a hemispherical alumina catalyst carrier according to claim 1, characterized in that: In step 3, the heat treatment is first drying at 120-150° C. for 5-9 hours, and then calcining at a constant temperature of 500-600° C. for 4-8 hours in an air atmosphere.

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