A method for producing spherical alumina by an oil column forming process

Abstract

The application discloses a method for preparing spherical alumina by an oil column forming process, which comprises the following steps: mixing pseudo-boehmite with water to form a pseudo-boehmite suspension, adding acid liquid and performing ultrasonic treatment to obtain an aluminum sol, mixing the obtained aluminum sol with a gelling agent, and performing oil column forming, microwave aging, washing, drying and calcination to obtain spherical alumina. The method combines ultrasonic technology with microwave technology, uses the super dispersion of ultrasonic waves to pretreat the aluminum sol suspension, and uses the volume heating of microwaves to age the formed balls, so that small balls with uniform and controllable strength are obtained, and the problem of uneven strength distribution of existing alumina small balls is solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalyst preparation, and particularly relates to a method for preparing spherical alumina by an oil column forming process. BACKGROUND

[0002] Active alumina is the most widely used industrial catalyst carrier due to its suitable pore distribution and large specific surface area. In the field of petroleum chemical industry, the continuous reforming catalyst used in the continuous reforming process is all based on spherical alumina as the carrier. The main methods for preparing the spherical alumina carrier include the oil-ammonia column forming method, the hot oil column forming method and the rotary forming method. Compared with other forming methods, the alumina prepared by the oil column forming method has the advantages of good sphericity, smooth surface and high strength.

[0003] The main steps of the hot oil column forming method for preparing alumina pellets are to drop the gelled aluminum sol into a hot oil column, under the action of surface tension, the sol particles shrink into balls in the oil phase, and gradually gel. After the gel pellets are solidified, they are taken out, dried and calcined to obtain spherical alumina solid particles. The spherical alumina produced by this method is widely used as fixed bed and moving bed catalysts, catalyst carriers and adsorbents.

[0004] At present, in the field of petroleum chemical industry, with the heavyening of processed oil products, it is required that the catalyst or catalyst carrier used has sufficient mechanical strength to withstand the mechanical and thermal impact during the reaction process. Therefore, the preparation of high-strength spherical alumina is increasingly concerned.

[0005] Patent CN 109692703A discloses a method for preparing molecular sieve pellets by hot oil column. In this method, aluminum hydroxide sol, molecular sieve, acid sol and hexamethyltetramine are mixed and dropped into a hot oil column for forming. This method is a common industrial practice, and can obtain pellets with a strength of about 60 N / pel. However, this method uses a large amount of amine / ammonia and oil, and the working environment is poor, and a large amount of wastewater is generated, which has gradually failed to meet the increasingly prominent environmental protection requirements. Patent CN 104891539A discloses a modification method of spherical alumina particles. In this method, liquid paraffin, different surfactants and activated carbon are added to modify the spherical alumina, so as to improve the pore volume and compressive strength of the product. However, this method has problems such as additive residue, reduction of product purity and poor stability. For example, patent CN 104477953A discloses a method for preparing pellets by dropping a mixed slurry of aluminum gel and sodium alginate into a metal salt solution. However, this method has difficulty in controlling the strength of the pellets, and the strength is not high, which limits the practical industrial application of this pellet dropping method.

[0006] Therefore, there is a need for a method that can effectively improve the strength of the pellets prepared by the pellet dropping method, while meeting the requirements of clean production. SUMMARY

[0007] The present application provides a method for preparing spherical alumina by an oil column forming process, which can effectively improve the drop ball forming strength and has a simple preparation method.

[0008] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0009] A method for preparing spherical alumina by an oil column forming process, comprising the following steps:

[0010] (1) mixing pseudo-boehmite and water and stirring uniformly to obtain a pseudo-boehmite suspension;

[0011] (2) mixing the obtained pseudo-boehmite suspension and an acid solution and stirring uniformly to obtain an initial aluminum sol slurry, and subjecting the slurry to ultrasonic treatment to obtain an aluminum sol;

[0012] (3) mixing the obtained aluminum sol with a gelling agent and dropping into a forming oil column for forming, and then subjecting to microwave aging, washing, drying and calcination to obtain spherical alumina.

[0013] Further, the pore volume of the pseudo-boehmite in step (1) is 0.6-1.2 mL / g.

[0014] Further, the content of alumina in the pseudo-boehmite suspension obtained in step (1) is 10-30 wt%, preferably 15-25 wt%.

[0015] Further, the acid solution in step (2) is an aqueous solution of nitric acid, hydrochloric acid or formic acid, and the concentration is 10-30 vol%, preferably a nitric acid solution with a concentration of 15-25 vol%.

[0016] Further, the H + The molar ratio of H in the acid solution to alumina in the pseudo-boehmite suspension is 0.02-0.10.

[0017] Further, the temperature of the stirring in step (2) is 30-80 ℃, and the time is 1-4 h.

[0018] Further, the ultrasonic treatment in step (2) has a frequency of 20 kHz-80 kHz, preferably 20 kHz-60 kHz, a power of 200 W-800 W, preferably 300 W-600 W, and a time of 5-30 min, preferably 10-20 min.

[0019] Further, the gelling agent in step (3) is one or more of hexamethylene tetramine, urea and ammonium chloride, preferably hexamethylene tetramine.

[0020] Further, the amount of the gelling agent added in step (3) is converted into 2.0%~15.0% of the mass of the alumina in the pseudo-boehmite suspension.

[0021] Further, the forming oil used in step (3) is one or more of vacuum pump oil, kerosene, white oil, and liquid paraffin, and preferably is vacuum pump oil, and the temperature thereof is 90~105 ℃.

[0022] Further, the frequency of the microwave aging in step (3) is 2450 MHz, the power is 400 W~1000 W, preferably 600 W~800 W, the temperature is 120~160 ℃, preferably 120~140 ℃, and the time is 8~48 h, preferably 12~14 h.

[0023] Further, the temperature of the drying in step (3) is 60~120 ℃, and the time is 12~24 h.

[0024] Further, the temperature of the calcination in step (3) is 550~650 ℃, and the time is 2~12 h.

[0025] The present application has the advantages of:

[0026] The present application combines ultrasonic technology with microwave technology, uses the super dispersion of the ultrasonic waves to pretreat the aluminum sol suspension to obtain sol particles with small and uniform particle sizes, thereby enhancing the adhesion of the sol and improving the strength of the spheres, and uses the "volume heating effect" of the microwaves to microwave age the formed spheres, thereby obtaining spheres with uniform strength. The method of the present application is simple to prepare, does not cause environmental pollution, and can solve the problem of uneven strength distribution of the alumina spheres, and obtain alumina spheres with controllable strength and meeting the use requirements of the catalyst carrier. DETAILED DESCRIPTION

[0027] A method for preparing spherical alumina by an oil column forming process, comprising the following steps:

[0028] (1) mixing pseudo-boehmite with water and stirring uniformly to obtain a pseudo-boehmite suspension, wherein the mass content of the alumina is 10~30%;

[0029] (2) mixing the obtained pseudo-boehmite suspension with an acid solution according to the molar ratio of H + to the alumina in the suspension is 0.02~0.10, and stirring uniformly at 30~80 ℃ for 1~4 h to obtain an initial aluminum sol slurry, and treating the slurry in ultrasonic waves with a frequency of 20 kHz~80 kHz and a power of 200 W~800 W for 5~30 min to obtain an aluminum sol;

[0030] (3) mixing the obtained aluminum sol with a gelling agent with 2.0% to 15.0% of the mass of aluminum oxide, and then dropping the mixture into a column of molding oil at 90 to 105 ℃ through a disperser to obtain gel balls, and then transferring the obtained gel balls to a microwave hydrothermal reactor, and aging the gel balls in a microwave at a frequency of 2450 MHz and a power of 400 W to 1000 W at 120 to 160 ℃ for 8 to 48 h, and then washing the obtained gel balls with petroleum ether until no obvious oil stains are present, and then drying the obtained gel balls at 60 to 120 ℃ for 12 to 24 h, and then calcining the obtained gel balls at 550 to 650 ℃ for 2 to 12 h to obtain spherical aluminum oxide.

[0031] In the step (1), the pseudo-boehmite has a pore volume of 0.6 to 1.2 mL / g.

[0032] In the step (2), the acid solution is an aqueous solution of nitric acid, hydrochloric acid or formic acid, and has a concentration of 10 to 30 vol%.

[0033] In the step (3), the gelling agent is one or more of hexamethylenetetramine, urea and ammonium chloride, and is preferably hexamethylenetetramine. The molding oil is one or more of vacuum pump oil, kerosene, white oil and liquid paraffin.

[0034] In order to make the content of the present application more convenient to understand, the technical solutions of the present application are further described below in combination with specific embodiments, but the present application is not limited thereto.

[0035] Example 1

[0036] (1) Preparation of aluminum sol: 40 g of commercial pseudo-boehmite (pore volume: 1.18 mL / g, specific surface area: 331 m 2 / g) was added to 100 g of deionized water, and stirred constantly at room temperature to obtain a pseudo-boehmite suspension with an aluminum oxide content of 20 wt%; 5 g of a 20 vol% nitric acid solution was then added dropwise, and stirred uniformly at 40 ℃ for 1 h, and then placed in an ultrasonic vibration instrument, and ultrasonically treated at a frequency of 20 kHz and a power of 600 W for 30 min to obtain an aluminum sol.

[0037] (2) Preparation of spherical aluminum oxide: 2.7 g of hexamethylenetetramine with a mass concentration of 35% was added to the aluminum sol at -15 ℃ to -5 ℃, and then mixed by stirring, and then dropped into a column of 100 ℃ vacuum pump oil through a 21# dispersing nozzle to form gel balls, and the formed gel balls were separated from the oil, and then aged in a microwave hydrothermal reactor at a frequency of 2450 MHz and a power of 600 W at 140 ℃ for 12 h, and then washed with petroleum ether until no obvious oil stains were present, and then dried at 60 ℃ to constant weight for 12 h, and then calcined at 650 ℃ for 4 h to obtain γ-Al2O3 balls.

[0038] Example 2

[0039] (1) Preparation of aluminum sol: 40 g of commercial pseudoboehmite (pore volume 1.18 mL / g, specific surface area 331 m 2 / g) was added to 100 g of deionized water, and stirred constantly at room temperature to obtain a pseudoboehmite suspension with an alumina content of 20 wt%; 5 g of a 20 vol% nitric acid solution was then added dropwise, and stirred uniformly at 40 °C for 1 h, and then placed in an ultrasonic vibration instrument, and ultrasonically treated at a frequency of 40 kHz and a power of 400 W for 30 min to obtain an aluminum sol.

[0040] (2) Preparation of spherical alumina: 2.7 g of hexamethylenetetramine with a mass concentration of 35% was added to the aluminum sol at -15 °C to -5 °C, and mixed by stirring, and then dropped into 100 °C vacuum pump oil using a 21# dispersion nozzle to form a gel ball, and the formed gel ball was separated from the oil, and then aged in a microwave hydrothermal reaction instrument at a frequency of 2450 MHz and a power of 600 W at 140 °C for 12 h, and then washed with petroleum ether until no obvious oil stains were present, and then dried at 60 °C for 12 h to a constant weight, and then calcined at 650 °C for 4 h to obtain γ-Al2O3 balls.

[0041] Example 3

[0042] (1) Preparation of aluminum sol: 40 g of commercial pseudoboehmite (pore volume 1.18 mL / g, specific surface area 331 m 2 / g) was added to 100 g of deionized water, and stirred constantly at room temperature to obtain a pseudoboehmite suspension with an alumina content of 20 wt%; 5 g of a 20 vol% nitric acid solution was then added dropwise, and stirred uniformly at 40 °C for 1 h, and then placed in an ultrasonic vibration instrument, and ultrasonically treated at a frequency of 20 kHz and a power of 600 W for 20 min to obtain an aluminum sol.

[0043] (2) Preparation of spherical alumina: 2.7 g of hexamethylenetetramine with a mass concentration of 35% was added to the aluminum sol at -15 °C to -5 °C, and mixed by stirring, and then dropped into 100 °C vacuum pump oil using a 21# dispersion nozzle to form a gel ball, and the formed gel ball was separated from the oil, and then aged in a microwave hydrothermal reaction instrument at a frequency of 2450 MHz and a power of 700 W at 140 °C for 12 h, and then washed with petroleum ether until no obvious oil stains were present, and then dried at 60 °C for 12 h to a constant weight, and then calcined at 650 °C for 4 h to obtain γ-Al2O3 balls.

[0044] Example 4

[0045] (1) Preparation of aluminum sol: 40 g of commercial pseudoboehmite (pore volume 1.18 mL / g, specific surface area 331 m 2 / g) was added to 120 g of deionized water, and stirred constantly at room temperature to obtain a pseudoboehmite suspension with an alumina content of 18 wt%; 5.5 g of a 20 vol% nitric acid solution was then added dropwise, and stirred uniformly at 60 °C for 1 h, and then placed in an ultrasonic vibration instrument, and ultrasonically treated at a frequency of 40 kHz and a power of 300 W for 20 min to obtain an aluminum sol.

[0046] (2) Preparation of spherical alumina: 3.2 g of hexamethylenetetramine with a mass concentration of 35% was added to the aluminum sol at -15 °C to -5 °C, and mixed by stirring, and then dropped into 100 °C vacuum pump oil using a 21# dispersion nozzle to form a gel ball, and the formed gel ball was separated from the oil, and then aged in a microwave hydrothermal reaction instrument at a frequency of 2450 MHz and a power of 700 W at 140 °C for 12 h, and then washed with petroleum ether until no obvious oil stains were present, and then dried at 60 °C for 12 h to a constant weight, and then calcined at 650 °C for 4 h to obtain γ-Al2O3 small balls.

[0047] Example 5

[0048] (1) Preparation of aluminum sol: 40 g of commercial pseudoboehmite (pore volume 1.18 mL / g, specific surface area 331 m 2 / g) was added to 120 g of deionized water, and stirred constantly at room temperature to obtain a pseudoboehmite suspension with an alumina content of 18 wt%; 5.5 g of a 20 vol% nitric acid solution was then added dropwise, and stirred uniformly at 60 °C for 1 h, and then placed in an ultrasonic vibration instrument, and ultrasonically treated at a frequency of 40 kHz and a power of 300 W for 20 min to obtain an aluminum sol.

[0049] (2) Preparation of spherical alumina: 3.2 g of hexamethylenetetramine with a mass concentration of 35% was added to the aluminum sol at -15 °C to -5 °C, and mixed by stirring, and then dropped into 100 °C vacuum pump oil using a 21# dispersion nozzle to form a gel ball, and the formed gel ball was separated from the oil, and then aged in a microwave hydrothermal reaction instrument at a frequency of 2450 MHz and a power of 700 W at 140 °C for 12 h, and then washed with petroleum ether until no obvious oil stains were present, and then dried at 60 °C for 12 h to a constant weight, and then calcined at 650 °C for 4 h to obtain γ-Al2O3 small balls.

[0050] Example 6

[0051] (1) Preparation of aluminum sol: 40 g of commercial pseudoboehmite (pore volume 1.18 mL / g, specific surface area 331 m 2 / g) was added to 120 g of deionized water, and stirred constantly at room temperature to obtain a pseudoboehmite suspension with an alumina content of 18 wt%; 5.5 g of a 20 vol% nitric acid solution was then added dropwise, and stirred uniformly at 60 °C for 1 h, and then placed in an ultrasonic vibration instrument, and ultrasonically treated at a frequency of 40 kHz and a power of 300 W for 30 min to obtain an aluminum sol.

[0052] (2) Preparation of spherical alumina: 3.2 g of hexamethylenetetramine with a mass concentration of 35% was added to the aluminum sol at -15 °C to -5 °C, and mixed by stirring, and then dropped into 100 °C vacuum pump oil using a 21# dispersion nozzle to form a gel ball, and the formed gel ball was separated from the oil, and then aged in a microwave hydrothermal reaction instrument at a frequency of 2450 MHz and a power of 800 W at 120 °C for 12 h, and then washed with petroleum ether until no obvious oil stains were present, and then dried at 60 °C for 12 h to a constant weight, and then calcined at 650 °C for 4 h to obtain γ-Al2O3 balls.

[0053] Comparative Example 1

[0054] (1) Preparation of aluminum sol: 40 g of commercial pseudoboehmite (pore volume 1.18 mL / g, specific surface area 331 m 2 / g) was added to 100 g of deionized water, and stirred constantly at room temperature to obtain a pseudoboehmite suspension with an alumina content of 20 wt%; 5 g of a 20 vol% nitric acid solution was then added dropwise, and stirred uniformly at 40 °C for 1 h, and then placed in an ultrasonic vibration instrument, and ultrasonically treated at a frequency of 20 kHz and a power of 100 W for 30 min to obtain an aluminum sol.

[0055] (2) Preparation of spherical alumina: 2.7 g of hexamethylenetetramine with a mass concentration of 35% was added to the aluminum sol at -15 °C to -5 °C, and mixed by stirring, and then dropped into 100 °C vacuum pump oil using a 21# dispersion nozzle to form a gel ball, and the formed gel ball was separated from the oil, and then aged in a microwave hydrothermal reaction instrument at a frequency of 2450 MHz and a power of 600 W at 140 °C for 12 h, and then washed with petroleum ether until no obvious oil stains were present, and then dried at 60 °C for 12 h to a constant weight, and then calcined at 650 °C for 4 h to obtain γ-Al2O3 balls.

[0056] Comparative Example 2

[0057] (1) Preparation of aluminum sol: 40 g of commercial pseudoboehmite (pore volume 1.18 mL / g, specific surface area 331 m 2 / g) was added to 100 g of deionized water, and stirred constantly at room temperature to obtain a pseudoboehmite suspension with an alumina content of 20 wt%; 5 g of a 20 vol% nitric acid solution was then added dropwise, and stirred uniformly at 40 °C for 1 h, and then placed in an ultrasonic vibration instrument, and ultrasonically treated at a frequency of 10 kHz and a power of 600 W for 30 min to obtain an aluminum sol.

[0058] (2) Preparation of spherical alumina: 2.7 g of hexamethylenetetramine with a mass concentration of 35% was added to the aluminum sol at -15 °C to -5 °C, and mixed by stirring, and then dropped into 100 °C vacuum pump oil using a 21# dispersion nozzle to form a gel ball, and the formed gel ball was separated from the oil, and then aged in a microwave hydrothermal reaction instrument at a frequency of 2450 MHz and a power of 600 W at 140 °C for 12 h, and then washed with petroleum ether until no obvious oil stains were present, and then dried at 60 °C for 12 h to a constant weight, and then calcined at 650 °C for 4 h to obtain γ-Al2O3 balls.

[0059] Comparative Example 3

[0060] (1) Preparation of aluminum sol: 40 g of commercial pseudoboehmite (pore volume 1.18 mL / g, specific surface area 331 m 2 / g) was added to 100 g of deionized water, and stirred constantly at room temperature to obtain a pseudoboehmite suspension with an alumina content of 20 wt%; 5 g of a 20 vol% nitric acid solution was then added dropwise, and stirred uniformly at 40 °C for 1 h, and then placed in an ultrasonic vibration instrument, and ultrasonically treated at a frequency of 20 kHz and a power of 600 W for 30 min to obtain an aluminum sol.

[0061] (2) Preparation of spherical alumina: 2.7 g of hexamethylenetetramine with a mass concentration of 35% was added to the aluminum sol at -15 °C to -5 °C, and mixed by stirring, and then dropped into 100 °C vacuum pump oil using a 21# dispersion nozzle to form a gel ball, and the formed gel ball was separated from the oil, and then aged in a microwave hydrothermal reaction instrument at a frequency of 2450 MHz and a power of 200 W at 140 °C for 12 h, and then washed with petroleum ether until no obvious oil stains were present, and then dried at 60 °C for 12 h to a constant weight, and then calcined at 650 °C for 4 h to obtain γ-Al2O3 balls.

[0062] Comparative Example 4

[0063] (1) Preparation of aluminum sol: 40 g of commercial pseudo-boehmite (pore volume 1.18 mL / g, specific surface area 331 m 2 / g) was weighed into 100 g of deionized water, and constant stirring was carried out at room temperature to obtain a pseudo-boehmite suspension with an alumina content of 20 wt%; 5 g of a 20 vol% nitric acid solution was added dropwise, and uniform stirring was carried out at 40 ℃ for 1 h, and then the sample was placed in an ultrasonic vibration instrument, and ultrasonic treatment was carried out at a frequency of 20 kHz and a power of 600 W for 30 min to obtain an aluminum sol.

[0064] (2) Preparation of spherical alumina: 2.7 g of hexamethylenetetramine with a mass concentration of 35% was added to the aluminum sol at -15 ℃ to -5 ℃, and the mixture was stirred and mixed, and then a 21# dispersion nozzle was used to drop the mixture into 100 ℃ vacuum pump oil to form a gel ball, the formed gel ball was separated from the oil, and then the gel ball was placed in a microwave hydrothermal reaction instrument, and microwave hydrothermal aging was carried out at a frequency of 2450 MHz and a power of 1100 W at 140 ℃ for 12 h, then the aged gel ball was washed with petroleum ether until no obvious oil stains were observed, and then the gel ball was dried at 60 ℃ to constant weight for 12 h, and then the gel ball was calcined at 650 ℃ for 4 h to obtain γ-Al2O3 small balls.

[0065] The DL4 type particle strength tester was used to test the crushing strength of the alumina small balls, 50 samples were tested, one maximum value and one minimum value were removed, and then the average value was taken as the crushing strength of the alumina small balls, and the results are shown in Table 1.

[0066] Table 1 Crushing strength of spherical alumina prepared in examples and comparative examples

[0067]

[0068] As shown in Table 1, under a specific frequency and power, the crushing strength of the alumina small balls prepared by using ultrasonic and microwave technologies is all above 75 N / ball, which can meet the strength requirement of the reforming catalyst carrier.

[0069] The above only describes the preferred embodiments of the present application, and any equivalent changes and modifications made within the scope of the present application should be included in the scope of the present application.

Claims

1. A method of preparing a spheroidal alumina by an oil column forming process, characterized by, The method comprises the following steps: (1) mixing pseudo-boehmite with water and stirring to obtain a pseudo-boehmite suspension; (2) mixing the obtained pseudo-boehmite suspension with an acid solution and stirring to obtain an initial aluminum sol slurry, and performing ultrasonic treatment on the slurry to obtain an aluminum sol; (3) mixing the obtained aluminum sol with a gelling agent and dropping into a column of molding oil for molding, and then performing microwave aging, washing, drying and calcination to obtain spherical alumina. The ultrasonic treatment in step (2) has a frequency of 20 kHz to 80 kHz, a power of 200 W to 800 W and a time of 5 to 30 min. The microwave aging in step (3) has a frequency of 2450 MHz, a power of 400 W to 1000 W, a temperature of 120 to 160 ℃ and a time of 8 to 48 h.

2. The method of claim 1, wherein the oil column forming process for preparing the spherical alumina is characterized by, The pseudo-boehmite in step (1) has a pore volume of 0.6 to 1.2 mL / g.

3. The method for preparing spherical alumina using the oil column forming process according to claim 1, characterized in that, The pseudo-boehmite suspension obtained in step (1) has an aluminum oxide content of 10 to 30 wt%.

4. The method of claim 1, wherein the oil column forming process for preparing the spherical alumina is characterized by, The acid solution in step (2) is an aqueous solution of nitric acid, hydrochloric acid or formic acid, and has a concentration of 10 to 30 vol%.

5. The method of claim 1, wherein the oil column forming process for preparing the spherical alumina is characterized by, H of the acid solution used in step (2) + The molar ratio of alumina to pseudoboehmite in the suspension is 0.02 to 0.

10.

6. The method of claim 1, wherein the oil column forming process for preparing the spherical alumina is characterized by, The gelling agent in step (3) is one or more of hexamethylenetetramine, urea and ammonium chloride, and is added in an amount of 2.0% to 15.0% of the mass of aluminum oxide in the pseudo-boehmite suspension.

7. The method of claim 1, wherein the oil column forming process for preparing the spherical alumina is characterized by, The drying in step (3) is performed at a temperature of 60 to 120 ℃ for 12 to 24 h.

8. The method of claim 1, wherein the spherical alumina is prepared by the oil column forming process, characterized in that, The calcination in step (3) is performed at a temperature of 550 to 650 ℃ for 2 to 12 h.

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