A process for the preparation of hydrothermally stable alumina pellets containing molecular sieves

Abstract

The application provides a preparation method of hydrothermally stable alumina beads containing molecular sieve. The method first prepares pseudo-boehmite by an aluminum alcoholate hydrolysis method with aluminum alcoholate as raw material, then prepares aluminum sol by peptizing the pseudo-boehmite, mixes the aluminum sol with a solution of the molecular sieve after ball milling, adds a gelling agent, and then performs oil column molding, infrared-microwave combined aging, washing, drying and calcination to obtain alumina bead carriers. The alumina bead carriers are hydrothermally treated at a temperature of 650 DEG C for 100 h, and the specific surface area still maintains 200~210 m 2 / g, and the mechanical strength can reach 40~60 N / grain. The application combines infrared heating and microwave heating to age the molded beads by incorporating high specific surface area molecular sieve, thereby obtaining alumina spherical carriers with large pore volume, high specific surface area and high mechanical strength, and solving the problem of poor hydrothermal stability of alumina beads.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of chemical synthesis, and particularly relates to a method for preparing a pseudo-boehmite by hydrolyzing an aluminum alcoholate and then preparing a spherical alumina with a large pore volume, a high specific surface area and a high strength by doping a molecular sieve with the pseudo-boehmite. BACKGROUND

[0002] The γ-alumina spheres have a large specific surface area, a special pore structure, good adsorption and certain acidity, and are one of the most widely used catalyst carrier materials. For example, the fluidized bed of the mainstream process of important chemical processes such as catalytic reforming and dehydrogenation of alkanes uses a spherical alumina to support a catalyst. When the spherical alumina is used as a carrier in the field of petroleum chemical industry, it is usually used at a high operating temperature and in the presence of water vapor, and sintering and phase transformation easily occur during use, which greatly reduces the specific surface area of the spherical alumina and leads to irreversible deactivation of the catalyst. Therefore, the preparation method and process of the spherical alumina should be optimized to improve the hydrothermal stability thereof.

[0003] At present, the main methods for preparing the spherical alumina carrier include an oil-ammonia column forming method, a hot oil column forming method, a rotating forming method and a spray drying method. Compared with other forming methods, the alumina prepared by the oil column forming method and the oil-ammonia column forming method has the advantages of good sphericity, uniform and reliable particle size, smooth surface and high strength, and is the optimal method for preparing the spherical alumina for a fluidized bed. The properties of the alumina hydrate precursor used for drop ball, such as the pore volume and the specific surface area, are partially retained after calcination, the purity thereof affects the performance of the catalyst, and the peptization performance thereof affects the mechanical strength of the catalyst.

[0004] The preparation methods of the alumina hydrate precursor mainly include a carbonization method, an inorganic method and an organic method. The organic method mainly refers to an alcoholate hydrolysis method, that is, an organic alcoholate salt is used as a raw material, and the physicochemical properties of the pseudo-boehmite are regulated by controlling various parameters in the processes of hydrolysis, hydrothermal aging, filtration, washing and drying under certain conditions, so that the pseudo-boehmite with a certain crystal structure is obtained. Compared with other methods, the alcoholate hydrolysis method uses the alcoholate salt which is easy to purify, that is, the obtained alumina product has less impurities and high purity. In addition, the peptization performance of the product is enhanced, that is, the mechanical strength of the alumina carrier is improved, but the specific surface area decreases seriously after calcination, and the hydrothermal stability is poor when the temperature is increased or the aging time is prolonged during the hydrothermal aging process of the alumina hydrate precursor. Conversely, the two will show opposite trends. Therefore, the preparation of the spherical alumina carrier with excellent hydrothermal stability has become the focus of research in the related field.

[0005] Patent CN104891538A discloses a preparation method of spherical gamma-alumina, which adopts pseudo-boehmite as raw material, and is prepared into slurry by acidizing sol and adding pseudo-boehmite suspension liquid, prepared into molding solution, formed into small balls by oil ammonia column molding method, and obtained by high temperature calcination. The mechanical strength of the spherical gamma-alumina is 30-60 N / particle, and the specific surface area is 240-300 m 2 / g, but the specific surface area decreases to 180-185 m 2 / g after hydrothermal treatment for 192 h, and the hydrothermal stability is poor.

[0006] Patent CN112973771B discloses a spherical catalyst carrier containing molecular sieve and alumina, which is prepared by precipitating inorganic aluminum salt with ammonia water, filtering and washing multiple times to obtain wet filter cake, adding deionized water and inorganic strong acid for peptization, adding mixed solution of ball-milled pseudo-boehmite and molecular sieve and peptization modification additives to the sol, and the pH value of the aluminum sol is 2.8. The mechanical strength of the small ball after molding is 51 N / particle. This method adopts inorganic method to prepare pseudo-boehmite, which consumes a large amount of deionized water to wash the filter cake, and impurities are easily left.

[0007] Patent CN104549554A introduces a method for preparing molecular sieve balls, which uniformly mixes molecular sieve powder and alumina powder, sprays aluminum sol in a rotating molding device to form balls, and the solid content of the aluminum sol is 10-25 wt%. The crushing strength of the molecular sieve balls prepared by this method can be increased to 30 N / particle, but it still cannot meet the requirements of the moving bed reaction. SUMMARY

[0008] The purpose of the present application is to provide a preparation method of hydrothermally stable alumina small balls containing molecular sieve. The method first prepares pseudo-boehmite by alcohol alumina hydrolysis method with alcohol alumina as raw material, then prepares aluminum sol by peptization, mixes with ball-milled molecular sieve solution, adds gelling agent, and then performs oil column molding, infrared-microwave combined aging, washing, drying and calcination to obtain alumina small ball carrier. After hydrothermal treatment at 650 ℃ for 100 h, the specific surface area of the alumina small ball carrier is still maintained at 200-210 m 2 / g, and the mechanical strength can reach 40-60 N / particle. The present application solves the problem of poor hydrothermal stability of alumina small balls by doping high specific surface area molecular sieve and adopting infrared heating combined with microwave heating to age the molded balls, thereby obtaining alumina spherical carrier with large pore volume, high specific surface area and high mechanical strength, which can completely meet the needs of oil processing.

[0009] The specific technical solutions of the present application are as follows:

[0010] A preparation method of a hydrothermally stable alumina pellet containing a molecular sieve, comprising the following steps:

[0011] (1) Dissolve aluminum alcoholate in an organic solvent at a certain temperature, and drop water into the solution at a constant speed until the aluminum alcoholate is completely hydrolyzed;

[0012] (2) Transfer the mixture after the reaction in step (1) to a hydrothermal aging kettle for aging treatment at a certain temperature and pressure, and then perform filtration, washing, drying, and pulverization to obtain pseudo-boehmite, wherein the D90 of the pseudo-boehmite particles after pulverization is 30 nm;

[0013] (3) Dissolve the pseudo-boehmite obtained in step (2) in deionized water to form a pseudo-boehmite suspension, add acid liquid to the suspension and mix uniformly to obtain a pseudo-boehmite sol;

[0014] (4) Add a high specific surface area molecular sieve to deionized water and perform ball milling to obtain a molecular sieve suspension;

[0015] (5) Add the molecular sieve suspension in step (4) to the sol in step (3) to obtain a mixed sol, add a gelling agent, and then drop the mixture into a column of molding oil for molding. The molded alumina pellets and the molding oil are first transferred to an infrared heating box for aging treatment, and then placed in a microwave heating box for further aging treatment for a period of time;

[0016] (6) Separate the aged alumina pellets, wash them with an organic solvent, and then dry and calcine them to obtain a molecular sieve-alumina pellet carrier with a large pore volume, a high specific surface area, and a high strength.

[0017] Further, the aluminum alcoholate in step (1) is one of isopropyl alcohol aluminum, n-butyl alcohol aluminum, sec-butyl alcohol aluminum, n-pentyl alcohol aluminum, n-hexyl alcohol aluminum, and isooctyl alcohol; the organic solvent is one or a mixture of two or more of C1-C8 alkanes, cycloalkanes, aromatic hydrocarbons, esters, and alcohols, and is preferably aromatic hydrocarbons, esters, and alcohols.

[0018] Further, the molar ratio of the aluminum alcoholate to the organic solvent in step (1) is 1:1-1:20, and the molar ratio of the aluminum alcoholate to water is 1:2-1:10.

[0019] Further, the aging temperature in step (2) is 80-200 ℃, and the aging time is 4-24 h.

[0020] Further, the mass content of alumina in the pseudo-boehmite suspension in step (3) is 10%-30%.

[0021] Further, the acid liquid in step (3) is an aqueous solution of nitric acid, hydrochloric acid, or formic acid with a mass percentage concentration of 10-30%, and the H +The molar ratio of the alumina to the pseudo-boehmite in the suspension is 0.02-0.10.

[0022] Further, the molecular sieve in step (4) is Y-type molecular sieve, and the specific surface area of the Y-type molecular sieve is 600-900 m 2 / g, preferably 800-900 m 2 / g, and the D90 of the particles in the suspension after ball milling is 30 nm.

[0023] Further, the mass percentage concentration of the alumina in the mixed sol in step (5) is 10-30%, and the mass percentage concentration of the molecular sieve is 5-20%.

[0024] Further, the gelling agent in step (5) is one or more of hexamethylenetetramine, urea and ammonium chloride, and the addition amount is converted into 2.0%-15.0% of the mass of the alumina in the pseudo-boehmite suspension.

[0025] Further, the hot oil column oil phase in step (5) is one or more of vacuum pump oil, kerosene, white oil and liquid paraffin, and the temperature of the hot oil column is 90-105 DEG C.

[0026] Further, the power of the infrared heating box in step (5) is 1500 W, the temperature is 120-160 DEG C, and the time is 4-10 h. The frequency of the microwave heating box is 2450 MHz, the power is 400 W-1000 W, the temperature is 120-160 DEG C, and the time is 4-10 h.

[0027] Further, the drying temperature of the alumina pellets in step (6) is 60-120 DEG C, and the drying time is 12-24 h. The calcination temperature is 550-650 DEG C, and the time is 2-12 h.

[0028] The present application has the following advantages:

[0029] The present application takes pseudo-boehmite prepared by hydrolysis of organic aluminum alcohol as raw material, and aging of the shaped ball is carried out by adding high specific surface area molecular sieve and combining infrared heating with microwave heating, so that the alumina spherical carrier with large pore volume, high specific surface area and high mechanical strength is obtained. Since the high specific surface area molecular sieve is not peptized, the prepared molecular sieve-alumina composite spherical carrier retains the high specific surface area characteristics of Y molecular sieve. Meanwhile, the combination of infrared heating and microwave heating makes up for the problem of uneven heating caused by using only one heating method. In the early stage of heating, the heating method is infrared heating from outside to inside and the heating rate is slow, which can avoid local overheating and reduce the excessive change or even damage of the internal structure of the small ball caused by rapid temperature rise; in the later stage of heating, microwave heating is used to supplement the heating of the internal object, so that the overall temperature is more uniform, the quality problem of the small ball caused by uneven temperature is reduced, and then the alumina small ball with large pore volume and uniform and high mechanical strength is obtained. DETAILED DESCRIPTION

[0030] The role and effect of the present application are further illustrated by the following examples, which are not limited to the following examples.

[0031] In the following examples, the pore volume and specific surface area of the alumina sample are determined by using the ASAP 2460 specific surface area and pore analyzer of the American Micromeritics company; the compressive strength is determined by using the DL 3 type particle strength tester of the Dalian Penghui Science and Technology Development Co., Ltd.; and the hydrothermal stability is determined by using the FD-HA hydrothermal aging device of Suzhou Furenande Experimental Equipment Co., Ltd.

[0032] Example 1

[0033] (1) Preparation of pseudo-boehmite: 200 g of aluminum isopropoxide is dissolved in 353 g of isopropyl alcohol at 60 ℃, and 70 g of water is added dropwise, and after the reaction is completed, the mixture after the reaction is transferred to an aging kettle and aged at 140 ℃ for 6 h, and then the aged mixture is filtered, washed and dried to obtain pseudo-boehmite.

[0034] (2) Preparation of aluminum sol: 40 g of the above prepared pseudo-boehmite is added to 100 g of deionized water for dissolution, and 5 g of 20% mass percentage nitric acid solution is added dropwise, and stirred at room temperature for 1 h to obtain pseudo-boehmite sol. 10 g of Y type molecular sieve with a specific surface area of 816 m 2 / g is added to 20 g of deionized water for ball milling, and the particle D90 in the suspension after ball milling is 30 nm. The molecular sieve suspension is added to the pseudo-boehmite sol to obtain a mixed sol, 2.7 g of 35% mass percentage hexamethylene tetramine solution is added to the mixed sol, and after stirring and mixing, it is dropped into 100 ℃ vacuum pump oil through a 21# dispersion dropper for shaping.

[0035] (3) Preparation of spherical alumina: the shaped alumina pellets and the shaping oil were first transferred to an infrared heating oven and aged at 120°C for 6 h; then placed in a microwave heating oven, under the conditions of a frequency of 2450 MHz and a power of 600 W, continued microwave aging at 120°C for 6 h. After that, the aged alumina pellets were separated, washed with petroleum ether until no obvious oil stains were present, then dried at 60°C to constant weight for 12 h, and then calcined at 650°C for 4 h to obtain γ-Al2O3 pellets, and the relevant physical property parameters are shown in Table 1.

[0036] Example 2

[0037] (1) Preparation of pseudo-boehmite: 200 g of aluminum isopropoxide was dissolved in 353 g of isopropyl alcohol at 60°C, and 70 g of water was added dropwise. After the reaction, the mixture was transferred to an aging kettle and aged at 140°C for 6 h. The aged mixture was filtered, washed, and dried to obtain pseudo-boehmite.

[0038] (2) Preparation of alumina sol: 40 g of the above-prepared pseudo-boehmite was added to 120 g of deionized water and dissolved, and 6 g of a 20% mass percent nitric acid solution was added dropwise. After stirring at room temperature for 1 h, a pseudo-boehmite sol was obtained. 15 g of Y-type molecular sieve with a specific surface area of 768 m 2 / g was added to 30 g of deionized water and ball milled. The D90 of the particles in the suspension after ball milling was 30 nm. The molecular sieve suspension was added to the pseudo-boehmite sol to obtain a mixed sol, and 3.5 g of a 35% mass percent hexamethylenetetramine solution was added to the mixed sol. After stirring and mixing, the mixture was shaped into pellets by dropping it into a 100°C vacuum pump oil using a 21# dispersion nozzle.

[0039] (3) Preparation of spherical alumina: the shaped alumina pellets and the shaping oil were first transferred to an infrared heating oven and aged at 120°C for 6 h; then placed in a microwave heating oven, under the conditions of a frequency of 2450 MHz and a power of 600 W, continued microwave aging at 120°C for 6 h. After that, the aged alumina pellets were separated, washed with petroleum ether until no obvious oil stains were present, then dried at 60°C to constant weight for 12 h, and then calcined at 650°C for 4 h to obtain γ-Al2O3 pellets, and the relevant physical property parameters are shown in Table 1.

[0040] Example 3

[0041] (1) Preparation of pseudo-boehmite: 200 g aluminum isopropoxide was dissolved in 412 g isopropyl alcohol at 60 °C, 70 g water was added dropwise, and the reaction mixture was transferred to an aging kettle after the reaction was completed, and aged at 140 °C for 6 h. The aged mixture was filtered, washed and dried to obtain pseudo-boehmite.

[0042] (2) Preparation of aluminum sol: 40 g of the pseudo-boehmite prepared above was dissolved in 100 g of deionized water, and 5 g of 20% nitric acid solution was added dropwise. The mixture was stirred at room temperature for 1 h to obtain a pseudo-boehmite sol. 10 g of Y-type molecular sieve with a specific surface area of 816 m 2 / g was added to 20 g of deionized water and ball milled. The D90 of the particles in the suspension after ball milling was 30 nm. The molecular sieve suspension was added to the pseudo-boehmite sol to obtain a mixed sol, 2.7 g of 35% hexamethylenetetramine solution was added to the mixed sol, and the mixture was stirred and then dropped into 100 °C vacuum pump oil through a 21# dispersion nozzle. Finally, the molding oil and the molded composite alumina pellets were transferred to a kettle and aged at 120 °C for 8 h.

[0043] (3) Preparation of spherical alumina: The molded alumina pellets and molding oil were first transferred to an infrared heating oven and aged at 140 °C for 5 h, and then placed in a microwave heating oven and aged at 140 °C for 5 h under the conditions of a frequency of 2450 MHz and a power of 800 W. The aged alumina pellets were then separated, washed with petroleum ether until no obvious oil stains were observed, 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 pellets. The relevant physical property parameters are shown in Table 1.

[0044] Example 4

[0045] (1) Preparation of pseudo-boehmite: 200 g aluminum isopropoxide was dissolved in 412 g isopropyl alcohol at 60 °C, 70 g water was added dropwise, and the reaction mixture was transferred to an aging kettle after the reaction was completed, and aged at 140 °C for 6 h. The aged mixture was filtered, washed and dried to obtain pseudo-boehmite.

[0046] (2) Preparation of aluminum sol: 40 g of the pseudo-boehmite prepared above was dissolved in 100 g of deionized water, and 5 g of 20% nitric acid solution was added dropwise. The mixture was stirred at room temperature for 1 h to obtain a pseudo-boehmite sol. 10 g of Y-type molecular sieve with a specific surface area of 816 m 2The Y-type molecular sieve with a specific surface area of 816 m2 / g was added to 30 g of deionized water for ball milling. After ball milling, the particle D90 in the suspension was 30 nm. The molecular sieve suspension was added to the pseudoboehmite sol to obtain a mixed sol. 3.5 g of a hexamethylenetetramine solution with a mass percentage of 35% was added to the mixed sol. After sufficient stirring and mixing, the mixture was dropped into vacuum pump oil at 100 ℃ using a 21# dispersion nozzle to form a shape.

[0047] (3) Preparation of spherical alumina: the shaped alumina pellets and the molding oil were first transferred to an infrared heating oven and aged at 140 ℃ for 5 h; then placed in a microwave heating oven, under the conditions of a frequency of 2450 MHz and a power of 800 W, continued to be microwave aged at 140 ℃ for 5 h. After that, the aged alumina pellets were separated, washed with petroleum ether until no obvious oil stains were observed, then dried at 60 ℃ for 12 h to a constant weight, and then calcined at 650 ℃ for 4 h to obtain γ-Al2O3 pellets. The relevant physical property parameters are shown in Table 1.

[0048] Example 5

[0049] (1) Preparation of pseudoboehmite: 200 g of aluminum isopropoxide was dissolved in 540 g of toluene at 60 ℃. 70 g of water was added dropwise. After the reaction, the mixture was transferred to an aging kettle and aged at 140 ℃ for 6 h. The aged mixture was filtered, washed, and dried to obtain pseudoboehmite.

[0050] (2) Preparation of aluminum sol: 40 g of the above prepared pseudoboehmite was added to 100 g of deionized water for dissolution. 5 g of a nitric acid solution with a mass percentage of 20% was added dropwise. After stirring at room temperature for 1 h, a pseudoboehmite sol was obtained. 10 g of Y-type molecular sieve with a specific surface area of 816 m 2 / g was added to 20 g of deionized water for ball milling. After ball milling, the particle D90 in the suspension was 30 nm. The molecular sieve suspension was added to the pseudoboehmite sol to obtain a mixed sol. 2.7 g of a hexamethylenetetramine solution with a mass percentage of 35% was added to the mixed sol. After sufficient stirring and mixing, the mixture was dropped into vacuum pump oil at 100 ℃ using a 21# dispersion nozzle to form a shape.

[0051] (3) Preparation of spherical alumina: the shaped alumina pellets and the molding oil were first transferred to an infrared heating oven and aged at 140 ℃ for 5 h; then placed in a microwave heating oven, under the conditions of a frequency of 2450 MHz and a power of 800 W, continued to be microwave aged at 140 ℃ for 5 h. After that, the aged alumina pellets were separated, washed with petroleum ether until no obvious oil stains were observed, then dried at 60 ℃ for 12 h to a constant weight, and then calcined at 650 ℃ for 4 h to obtain γ-Al2O3 pellets. The relevant physical property parameters are shown in Table 1.

[0052] Example 6

[0053] (1) Preparation of pseudo-boehmite: 200 g aluminum isopropoxide was dissolved in 540 g of toluene at 60 °C, 70 g of water was added dropwise, and after the reaction was completed, the mixture was transferred to an aging kettle and aged at 140 °C for 6 h. The aged mixture was filtered, washed, and dried to obtain pseudo-boehmite.

[0054] (2) Preparation of aluminum sol: 40 g of the pseudo-boehmite prepared above was dissolved in 120 g of deionized water, and 6 g of a 20% mass percentage nitric acid solution was added dropwise. The mixture was stirred at room temperature for 1 h to obtain a pseudo-boehmite sol. 15 g of Y-type molecular sieve with a specific surface area of 768 m 2 / g was added to 30 g of deionized water and ball milled. The D90 of the particles in the suspension after ball milling was 30 nm. The molecular sieve suspension was added to the pseudo-boehmite sol to obtain a mixed sol, and 3.5 g of a 35% mass percentage hexamethylenetetramine solution was added to the mixed sol. After the mixture was stirred, it was dropped into vacuum pump oil at 100 °C using a 21# dispersion nozzle to form a spherical shape.

[0055] (3) Preparation of spherical alumina: The formed alumina pellets and the forming oil were first transferred to an infrared heating oven and aged at 140 °C for 4 h. Then, the mixture was placed in a microwave heating oven and aged at 120 °C for 6 h under the conditions of a frequency of 2450 MHz and a power of 800 W. After aging, the alumina pellets were separated, washed with petroleum ether until no obvious oil stains were present, and then dried at 60 °C for 12 h to a constant weight. The dried pellets were calcined at 650 °C for 4 h to obtain γ-Al2O3 pellets. The relevant physical property parameters of the pellets are shown in Table 1.

[0056] Comparative Example 1

[0057] (1) Preparation of pseudo-boehmite: 200 g aluminum isopropoxide was dissolved in 353 g of isopropyl alcohol at 60 °C, 70 g of water was added dropwise, and after the reaction was completed, the mixture was transferred to an aging kettle and aged at 140 °C for 6 h. The aged mixture was filtered, washed, and dried to obtain pseudo-boehmite.

[0058] (2) Preparation of aluminum sol: 40 g of the pseudo-boehmite prepared above was dissolved in 100 g of deionized water, and 5 g of a 20% mass percentage nitric acid solution was added dropwise. The mixture was stirred at room temperature for 1 h to obtain a pseudo-boehmite sol. 2.7 g of a 35% mass percentage hexamethylenetetramine solution was added to the sol, and after the mixture was stirred, it was dropped into vacuum pump oil at 100 °C using a 21# dispersion nozzle to form a spherical shape.

[0059] (3) Preparation of spherical alumina: The shaped alumina pellets and the shaping oil were first transferred to an infrared heating oven and aged at 120 °C for 6 h; then placed in a microwave heating oven, under the conditions of a frequency of 2450 MHz and a power of 600 W, continued to be microwave aged at 120 °C for 6 h. After that, the aged alumina pellets were separated, washed with petroleum ether until no obvious oil stains were present, then dried at 60 °C for 12 h to constant weight, and then calcined at 650 °C for 4 h to obtain γ-Al2O3 pellets, and the relevant physical property parameters are shown in Table 1.

[0060] Comparative Example 2

[0061] (1) Preparation of pseudoboehmite: 200 g of aluminum isopropoxide was dissolved in 353 g of isopropyl alcohol at 60 °C, and 70 g of water was added dropwise. After the reaction, the mixture was transferred to an aging kettle and aged at 140 °C for 6 h. The aged mixture was filtered, washed, and dried to obtain pseudoboehmite.

[0062] (2) Preparation of alumina sol: 40 g of the prepared pseudoboehmite was added to 100 g of deionized water and dissolved, and 5 g of a 20% mass percentage nitric acid solution was added dropwise. After stirring at room temperature for 1 h, a pseudoboehmite sol was obtained. 10 g of Y-type molecular sieve with a specific surface area of 816 m 2 / g was added to 20 g of deionized water and ball milled. The particle D90 in the suspension after ball milling was 30 nm. The molecular sieve suspension was added to the pseudoboehmite sol to obtain a mixed sol, and 2.7 g of a 35% mass percentage hexamethylenetetramine solution was added to the mixed sol. After stirring and mixing, the mixture was shaped into pellets by dropping into a 100 °C vacuum pump oil through a 21# dispersion nozzle.

[0063] (3) Preparation of spherical alumina: The shaping oil and the shaped composite alumina pellets were transferred to a kettle and aged at 120 °C for 8 h. After that, the aged alumina pellets were separated, washed with petroleum ether until no obvious oil stains were present, then dried at 60 °C for 12 h to constant weight, and then calcined at 650 °C for 4 h to obtain γ-Al2O3 pellets, and the relevant physical property parameters are shown in Table 1.

[0064] Comparative Example 3

[0065] (1) Preparation of pseudoboehmite: 200 g of aluminum isopropoxide was dissolved in 353 g of isopropyl alcohol at 60 °C, and 70 g of water was added dropwise. After the reaction, the mixture was transferred to an aging kettle and aged at 140 °C for 6 h. The aged mixture was filtered, washed, and dried to obtain pseudoboehmite.

[0066] (2) Preparation of aluminum sol: 40 g of the pseudo-boehmite prepared above was dissolved in 100 g of deionized water, and then 5 g of a 20% mass percentage nitric acid solution was added dropwise. The mixture was stirred at room temperature for 1 h to obtain a pseudo-boehmite sol. 10 g of Y-type molecular sieve with a specific surface area of 816 m 2 / g was added to 20 g of deionized water for ball milling. After ball milling, the particle D90 in the suspension was 30 nm. The molecular sieve suspension was added to the pseudo-boehmite sol to obtain a mixed sol. 2.7 g of a 35% mass percentage hexamethylenetetramine solution was added to the mixed sol, and the mixture was stirred thoroughly before being dropped into vacuum pump oil at 100 °C using a 21# dispersion nozzle for molding.

[0067] (3) Preparation of spherical alumina: The molding oil and the molded composite alumina pellets were transferred to a microwave heating box, and microwave aging was performed at a frequency of 2450 MHz and a power of 600 W at 120 °C for 12 h. After aging, the alumina pellets were separated, washed with petroleum ether until no obvious oil stains were present, and then dried at 60 °C for 12 h to a constant weight, followed by calcination at 650 °C for 4 h to obtain γ-Al2O3 pellets. The relevant physical property parameters are shown in Table 1.

[0068] Comparative Example 4

[0069] (1) Preparation of pseudo-boehmite: 200 g of aluminum isopropoxide was dissolved in 353 g of isopropyl alcohol at 60 °C, and then 70 g of water was added dropwise. After the reaction, the mixture was transferred to an aging kettle and aged at 140 °C for 6 h. The aged mixture was filtered, washed, and dried to obtain pseudo-boehmite.

[0070] (2) Preparation of aluminum sol: 40 g of the pseudo-boehmite prepared above was dissolved in 100 g of deionized water, and then 5 g of a 20% mass percentage nitric acid solution was added dropwise. The mixture was stirred at room temperature for 1 h to obtain a pseudo-boehmite sol. 10 g of Y-type molecular sieve with a specific surface area of 816 m 2 / g was added to 20 g of deionized water for ball milling. After ball milling, the particle D90 in the suspension was 30 nm. The molecular sieve suspension was added to the pseudo-boehmite sol to obtain a mixed sol. 2.7 g of a 35% mass percentage hexamethylenetetramine solution was added to the mixed sol, and the mixture was stirred thoroughly before being dropped into vacuum pump oil at 100 °C using a 21# dispersion nozzle for molding.

[0071] (3) Preparation of spherical alumina: The molding oil and the molded composite alumina pellets were transferred to an infrared heating oven, and aged at 120 °C for 12 h. Then the aged alumina pellets were separated, washed with petroleum ether until no obvious oil stains were observed, and then dried at 60 °C for 12 h to constant weight, and then calcined at 650 °C for 4 h to obtain γ-Al2O3 pellets, and the relevant physical property parameters are shown in Table 1.

[0072] Comparative Example 5

[0073] (1) Preparation of pseudoboehmite: 200 g aluminum isopropoxide was dissolved in 353 g isopropyl alcohol at 60 °C, and 70 g water was added dropwise, and after the reaction was completed, the reaction mixture was transferred to an aging kettle and aged at 140 °C for 6 h. The aged mixture was filtered, washed, and dried to obtain pseudoboehmite.

[0074] (2) Preparation of aluminum sol: 40 g of the above-prepared pseudoboehmite was dissolved in 100 g of deionized water, and 5 g of a 20% mass percentage nitric acid solution was added dropwise, and stirred at room temperature for 1 h to obtain a pseudoboehmite sol. 10 g of Y-type molecular sieve with a specific surface area of 816 m 2 / g was added to 20 g of deionized water for ball milling, and the particle D90 in the suspension after ball milling was 30 nm. The molecular sieve suspension was added to the pseudoboehmite sol to obtain a mixed sol, and 2.7 g of a 35% mass percentage hexamethylenetetramine solution was added to the mixed sol, and after stirring and mixing, it was formed into a pellet by dropping into 100 °C vacuum pump oil through a 21# dispersion dropper.

[0075] (3) Preparation of spherical alumina: The molding oil and the molded composite alumina pellets were transferred to an infrared heating oven, and aged at 120 °C for 12 h. Then the aged alumina pellets were separated, washed with petroleum ether until no obvious oil stains were observed, and then dried at 60 °C for 12 h to constant weight, and then calcined at 650 °C for 4 h to obtain γ-Al2O3 pellets, and the relevant physical property parameters are shown in Table 1.

[0076] Comparative Example 6

[0077] (1) Preparation of pseudoboehmite: 200 g aluminum isopropoxide was dissolved in 353 g isopropyl alcohol at 60 °C, and 70 g water was added dropwise, and after the reaction was completed, the reaction mixture was transferred to an aging kettle and aged at 140 °C for 6 h. The aged mixture was filtered, washed, and dried to obtain pseudoboehmite.

[0078] (2) Preparation of aluminum sol: 40 g of the prepared boehmite was dissolved in 100 g of deionized water, and then 5 g of 20% nitric acid solution was added dropwise. The mixture was stirred at room temperature for 1 h to obtain boehmite sol. 10 g of a solution with a specific surface area of ​​540 g / m² was then added. 2 Y-type molecular sieves were added to 14g of deionized water and ball-milled. The particle D90 in the suspension after ball milling was 30 nm. The molecular sieve suspension was added to a pseudoboehmite sol to obtain a mixed sol. 2.7g of a 35% (w / w) hexamethylenetetramine solution was added to the mixed sol, and after thorough mixing, it was dropped into vacuum pump oil at 100 °C using a No. 21 dispersing dropper to form the sol.

[0079] (3) Preparation of spherical alumina: The shaped alumina microspheres and the shaped oil were first transferred to an infrared heating box and aged at 120 °C for 6 h; then placed in a microwave heating box and microwave hydrothermal aging continued at 120 °C for 6 h at a frequency of 2450 MHz and a power of 600 W. After that, the aged alumina microspheres were separated, washed with petroleum ether until there were no obvious oil stains, dried at 60 °C for 12 h to constant weight, and then calcined at 650 °C for 4 h to obtain γ-Al2O3 microspheres. The relevant physical properties are shown in Table 1.

[0080] Comparative Example 7

[0081] (1) Preparation of pseudoboehmite: 375 g of aluminum nitrate was dissolved in 350 g of 8% ammonia solution and stirred at 60°C to allow the two to react fully. After the reaction was completed, the mixture was transferred to an aging vessel and aged at 140°C for 6 h. The aged mixture was then filtered, washed and dried to obtain pseudoboehmite.

[0082] (2) Preparation of aluminum sol: 40 g of the pseudoboehmite prepared by the above inorganic salt method was dissolved in 100 g of deionized water, and then 5 g of 20% nitric acid solution was added dropwise. The mixture was stirred at room temperature for 1 h to obtain pseudoboehmite sol. 10 g of a solution with a specific surface area of ​​816 m² was then added. 2 / g of Y-type molecular sieve was added to 20g of deionized water and ball-milled. The particle D90 in the suspension after ball milling was 30 nm. The molecular sieve suspension was added to a pseudoboehmite sol to obtain a mixed sol. 2.7g of a 35% (w / w) hexamethylenetetramine solution was added to the mixed sol, and after thorough mixing, it was dropped into vacuum pump oil at 100 °C using a No. 21 dispersing dropper to form the sol.

[0083] (3) Preparation of spherical alumina: the formed alumina pellets and forming oil were first transferred to an infrared heating box and aged at 120°C for 6 hours; then placed in a microwave heating box, under the conditions of frequency 2450 MHz, power 600 W, 120°C, continued microwave hydrothermal aging for 6 hours. After that, the aged alumina pellets were separated, washed with petroleum ether until no obvious oil stains, then dried at 60°C for 12 hours to constant weight, and then calcined at 650°C for 4 hours to obtain γ-Al2O3 pellets, and the relevant physical property parameters are shown in Table 1.

[0084] Hydrothermal stability is the specific surface area of the sample treated with water vapor at 650°C for 100 hours.

[0085] Table 1 is the performance test results of the alumina pellets prepared in the examples and comparative examples.

[0086] Table 1

[0087]

[0088] As can be seen from Table 1, using pseudo-boehmite prepared by hydrolysis of organic aluminum alcohol as raw material, by adding high specific surface area molecular sieve and using infrared heating combined with microwave heating method to age the formed pellets, the specific surface area of the molecular sieve-alumina composite pellet carrier is all above 250 m 2 / g, the pore volume is all above 0.70 cm 3 / g, and the mechanical strength is all above 70 N / pellet; after being treated with water vapor at 650°C for 100 hours, the specific surface area is still above 200 m 2 / g, the pore volume is above 0.60 cm 3 / g, and the mechanical strength is all above 40 N / pellet, which has excellent hydrothermal stability. The specific surface area of the pseudo-boehmite prepared by the inorganic salt method in Comparative Examples 1-7 is less than 600 m 2 / g or the specific surface area of Y molecular sieve, or the spherical carrier prepared by the traditional single aging method, the specific surface area, pore volume and mechanical strength all decrease greatly after being treated with water vapor at 650°C for 100 hours, and the hydrothermal stability is poor. Therefore, compared with the comparative examples, the spherical alumina prepared by the method provided by the present application has better specific surface area, pore volume and crushing strength, and the hydrothermal stability is obviously enhanced.

[0089] The above only describes the preferred embodiments of the present application, and any equivalent changes and modifications made within the scope of the patent application of the present application shall be included in the scope of the present application.

Claims

1. A process for preparing hydrothermally stable alumina pellets containing molecular sieves, characterized by, The method comprises the following steps: (1) dissolving aluminum alcohol in an organic solvent at a certain temperature, and adding water into the solution at a constant speed until the aluminum alcohol is completely hydrolyzed; (2) transferring the mixture after the reaction in step (1) into a hydrothermal aging kettle, and performing aging treatment at a certain temperature and pressure, and then performing filtration, washing, drying, and pulverization to obtain pseudo-boehmite; (3) dissolving the pseudo-boehmite obtained in step (2) in deionized water to form a pseudo-boehmite suspension, adding acid liquid into the suspension, and uniformly mixing to obtain a pseudo-boehmite sol; (4) adding a high specific surface area molecular sieve into deionized water, and performing ball milling to obtain a molecular sieve suspension; (5) adding the molecular sieve suspension in step (4) into the sol in step (3) to obtain a mixed sol, adding a gelling agent, and then adding into a hot oil column to perform molding, and then transferring the molded alumina pellets and the hot oil into an infrared heating box to perform aging treatment, and then transferring the alumina pellets into a microwave heating box to continue aging treatment for a period of time; (6) separating the aged alumina pellets, washing with an organic solvent, and then drying and calcining to obtain molecular sieve-alumina pellet carriers with large pore volume, high specific surface area, and high strength. The molecular sieve in step (4) is Y-type molecular sieve, and its specific surface area is 600-900 m 2 / g.

2. The process for preparing a hydrothermally stable alumina pellet containing molecular sieve according to claim 1, characterized by, The aluminum alcohol in step (1) is one of isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, n-pentyl alcohol, n-hexyl alcohol, and isooctyl alcohol; the organic solvent is one or a mixture of two or more of C1-C8 alkanes, cycloalkanes, arenes, esters, and alcohols; the molar ratio of the aluminum alcohol to the organic solvent is 1:1-1:20, and the molar ratio of the aluminum alcohol to water is 1:2-1:

10.

3. The process for preparing a hydrothermally stable alumina pellet containing molecular sieve according to claim 1, characterized by, The aging temperature in step (2) is 80-200 ℃, and the aging time is 4-24 h; the D90 of the pseudo-boehmite particles after pulverization is 30 nm.

4. The process for preparing a hydrothermally stable alumina pellet containing molecular sieve according to claim 1, characterized by, The mass content of alumina in the pseudoboehmite suspension in step (3) is 10% to 30%; the acid liquid is a 10 to 30% mass percent aqueous solution of nitric acid, hydrochloric acid or formic acid, and the H + The molar ratio of the acid liquid to the alumina in the pseudoboehmite suspension is 0.02 to 0.

10.

5. The process for preparing a hydrothermally stable alumina pellet containing molecular sieve according to claim 1, characterized by, The mass percentage concentration of the alumina in the mixed sol in step (5) is 10-30%, and the mass percentage concentration of the molecular sieve is 5-20%.

6. The process for preparing a hydrothermally stable alumina pellet containing molecular sieve according to claim 1, characterized by, The gelling agent in step (5) is one or more of hexamethylenetetramine, urea, and ammonium chloride, and the addition amount is 2.0%-15.0% of the mass of the alumina in the pseudo-boehmite suspension.

7. The process for preparing a hydrothermally stable alumina pellet containing molecular sieve according to claim 1, characterized by, The oil phase of the hot oil column in step (5) is one or several of vacuum pump oil, kerosene, white oil, and liquid paraffin; and the temperature of the hot oil column is 90-105 ℃.

8. The process for preparing a hydrothermally stable alumina pellet containing molecular sieve according to claim 1, characterized by, The power of the infrared aging in step (5) is 1500 W, the temperature is 120-160 ℃, and the time is 4-10 h; the frequency of the microwave aging is 2450 MHz, the power is 400 W-1000 W, the temperature is 120-160 ℃, and the time is 4-10 h.

9. The process for preparing a hydrothermally stable alumina pellet containing molecular sieve according to claim 1, characterized by, The drying temperature of the alumina pellets in step (6) is 60-120 ℃, the drying time is 12-24 h, the calcination temperature is 550-650 ℃, and the time is 2-12 h.

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