A multi-modal alumina support and a method for its preparation

Abstract

The application discloses a multi-form alumina carrier and a preparation method thereof. The alumina carrier of the application has flaky alumina and vermicular alumina grains respectively grown in-situ on the outer surface and the inner spherical cavity. The preparation method is as follows: (1) micron spherical activated carbon, pseudo-boehmite and water are mixed to obtain a slurry, the slurry is filtered and dried, the dried material is mixed, formed, dried, and then calcined in an inert atmosphere to obtain an alumina carrier precursor I; (2) the alumina carrier precursor I is subjected to a first sealed heat treatment to obtain an alumina carrier precursor II; (3) the alumina carrier precursor II is subjected to a second sealed heat treatment to obtain the multi-form alumina carrier. The pore structure of the alumina carrier is better optimized and adjusted, the alumina carrier has better mass transfer and reaction space, and can be used for macromolecular heterogeneous catalytic reaction, and is particularly suitable for heavy oil and residual oil hydroprocessing.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of material synthesis, and particularly relates to a polymorph alumina carrier and a preparation method thereof. BACKGROUND

[0002] With the increasing requirement of raw material deep processing in the world, the main energy structure gradually develops towards macromolecules and high carbon, and this is particularly true for China where the crude oil is generally heavy. In order to effectively solve the problems of catalyst activity decline or deactivation caused by excessive diffusion resistance of heavy oil components in the catalyst pore, deposition of heavy metal impurities and coking, it is urgently required to widely use alumina carriers with large pore volume and large pore diameter in the petroleum chemical industry and other industries.

[0003] CN104646008A discloses a poor-quality heavy oil hydrodesulfurization and demetallization catalyst and a preparation method thereof. The catalyst uses alumina as the carrier, and uses group VIII and group VIB elements, especially Ni-Mo, as the active component. The pore volume of the catalyst is 0.61-0.70 mL / g, the specific surface area is 155-200 m 2 / g, and the average pore diameter is 13.0-18.0 nm. The preparation method of the catalyst is to treat the carrier particles after molding and calcination with an acid solution with continuously increasing concentration. Although this method can make the average pore diameter of the final catalyst gradually increase from the center to the outer surface along the radial direction of the catalyst particle to a certain extent, the surface pore of the carrier is small, which is not conducive to the diffusion of residual oil reactant molecules to the inside of the catalyst, and the surface resistance to metal deposition and carbon deposition is poor.

[0004] CN109718860A discloses an alumina carrier and a preparation method thereof. The alumina carrier prepared by the method includes main body alumina and rod-shaped structure alumina, and at least part of the rod-shaped structure alumina is distributed on the outer surface of the main body alumina carrier. The rod-shaped structure alumina has a length of 1-12 µm and a diameter of 100-300 nm. The preparation method of the alumina carrier includes mixing the alumina carrier, ammonium bicarbonate and water, and then performing sealed heat treatment. After the heat treatment, the material is dried and calcined to obtain the alumina carrier. This method adjusts the pore structure of the carrier by growing rod-shaped structure alumina on the surface of the alumina carrier, but the rod-shaped alumina grown on the surface is easy to fall off, and the optimization of the pore structure needs to be improved. SUMMARY

[0005] In view of the deficiencies in the prior art, the present application provides a polymorph alumina carrier and a preparation method thereof. The outer surface and the spherical cavity inside the alumina carrier of the present application respectively grow flaky alumina and vermicular alumina grains in situ, and the pore structure is better optimized and adjusted. The alumina carrier has better mass transfer and reaction space, and can be used for macromolecular heterogeneous catalytic reaction, and is particularly suitable for heavy oil and residual oil hydroprocessing.

[0006] The multi-morphology alumina carrier of the present application comprises an alumina matrix containing spherical cavities and sheet-shaped alumina grown in situ on the surface of the matrix, and worm-shaped alumina grown in situ in the spherical cavities.

[0007] In the multi-morphology alumina carrier of the present application, the worm-shaped alumina is grown in situ in the spherical cavities of the alumina matrix, the size of the worm-shaped alumina particles is 80-350 nm, the worm-shaped particles are packed to form 30-50 nm pores, the filling rate of the spherical cavities is 20%-50%, the diameter of the spherical cavities is 1-10 μm, preferably 1-5 μm, and more preferably 1-3 μm; wherein the filling rate refers to the percentage of the volume of the worm-shaped alumina particles in the spherical cavities in the volume of the micron-sized spherical cavities; the area percentage of the spherical cavities is 15%-30%; the area percentage of the spherical cavities refers to the percentage of the area of the spherical cavities in the cross section of the alumina carrier in the cross-sectional area.

[0008] In the multi-morphology alumina carrier of the present application, the sheet-shaped alumina is grown in situ on the outer surface of the alumina matrix, the size of the sheet-shaped alumina particles is 100 nm-600 nm, the sheet-shaped particles are packed to form 40-300 nm pores, and the coverage of the sheet-shaped particles on the outer surface of the alumina matrix is 85%-100%, wherein the coverage refers to the percentage of the surface of the sheet-shaped alumina particles on the outer surface of the alumina matrix in the outer surface of the alumina matrix.

[0009] In the multi-morphology alumina carrier of the present application, the alumina matrix is generally composed of spherical particles, and the size of the spherical particles is 20-100 nm.

[0010] The specific surface area of the multi-morphology alumina carrier of the present application is 180-320 m 2 / g, and the pore volume is 0.8-1.2 mL / g.

[0011] The preparation method of the multi-morphology alumina carrier of the present application comprises the following steps:

[0012] (1) micron-sized spherical activated carbon, pseudoboehmite and water are mixed to obtain a slurry, the slurry is filtered and dried, the dried material is mixed and kneaded, shaped, dried, and then calcined in an inert atmosphere to obtain an alumina carrier precursor I;

[0013] (2) the alumina carrier precursor I is immersed in an aqueous propylene oxide solution for a first sealed heat treatment, the treated material is subjected to solid-liquid separation, the solid material is dried and calcined to obtain an alumina carrier precursor II;

[0014] (3) the alumina carrier precursor II is immersed in an aqueous propylene oxide solution for a second sealed heat treatment, the treated material is subjected to solid-liquid separation, the solid material is dried and calcined to obtain a multi-morphology alumina carrier.

[0015] In the method of the present application, the pseudo-boehmite particles in step (1) have a general spherical morphology, which can be a commercially available product or prepared by methods such as acid precipitation, alkali precipitation, alcohol aluminum hydrolysis, etc. Preferably, the pseudo-boehmite has a pore size greater than 10 nm.

[0016] In the method of the present application, the microspherical activated carbon in step (1) can be prepared by existing methods or purchased. The microspherical activated carbon has a diameter of 1-10 μm, preferably 1-5 μm. The mass ratio of the microspherical activated carbon to the pseudo-boehmite is 1:4-1:19, preferably 1:10-1:5.5; and the liquid-solid mass ratio of the slurry is 5:1-10:1.

[0017] In the method of the present application, the kneading and forming in step (1) is performed by conventional methods in the art. During the forming process, a deagglomerating agent and a peptizing agent can be added as needed. The deagglomerating agent is pearl millet powder, and the amount added is 0.1wt%-0.5wt% of the weight of the alumina carrier. The peptizing agent is one or more of hydrochloric acid, nitric acid, sulfuric acid, acetic acid, and oxalic acid, and the amount added is 0.5wt%-1.5wt% of the weight of the alumina carrier.

[0018] In the method of the present application, the drying temperature in step (1) is 100-160℃, and the drying time is 6-10 hours; the inert atmosphere is nitrogen and / or an inert gas, the calcination temperature is 450-700℃, and the calcination time is 4-6 hours.

[0019] In the method of the present application, the mass percentage concentration of the propylene oxide aqueous solution in step (2) is 2.5%-12%, preferably 4%-8%, and the mass ratio of the propylene oxide aqueous solution to the alumina carrier precursor I is 3:1-10:1, preferably 4:1-8:1.

[0020] In the method of the present application, the first sealing heat treatment in step (2) is performed in a closed container, preferably an autoclave. The first sealing heat treatment conditions are: treatment at 60-100℃ for 1-4 hours, then heating to 110-180℃, preferably 120-160℃, and treatment for 14-20 hours.

[0021] In the method of the present application, the drying temperature in step (2) is 100-160℃, and the drying time is 2-8 hours; the calcination temperature is 450-750℃, and the calcination time is 4-6 hours, and the calcination is performed in an oxygen-containing atmosphere, preferably an air atmosphere.

[0022] In the method, the mass percentage concentration of the propylene oxide aqueous solution in step (3) is 2.5%-12%, preferably 4%-8%, and the mass ratio of the propylene oxide aqueous solution to the alumina carrier precursor II is 3:1-10:1, preferably 4:1-8:1.

[0023] In the method, the second sealing heat treatment in step (3) is carried out in a closed container, preferably an autoclave, and the second sealing heat treatment conditions are as follows: sealing heat treatment at 60-100℃ for 1-4 hours, then heating to 110-180℃, preferably 120-160℃, and sealing heat treatment for 2-6 hours.

[0024] In the method, the drying temperature in step (3) is 100-160℃, the drying time is 2-8 hours, the calcination temperature is 500-750℃, and the calcination time is 4-6 hours, and the calcination is carried out in an oxygen-containing atmosphere, preferably an air atmosphere.

[0025] The polymorphic alumina carrier of the application is suitable for use in macromolecular heterogeneous catalytic reactions, especially in heavy oil hydroprocessing.

[0026] Compared with the prior art, the application has the following advantages:

[0027] The polymorphic alumina carrier of the application comprises an alumina matrix composed of spherical particles, spherical cavities in the matrix with worm-like alumina growing therein, and an outer surface with flaky alumina growing thereon, the flaky particles have regular shapes and are stacked on the outer surface of the alumina carrier to form open channels with a diameter of 40-300nm, the flaky particles have strong interaction with the alumina matrix and are not easy to fall off; the worm-like particles are filled in the spherical cavities and stacked to form a large number of channels with a diameter of 30-50nm; the spherical particles are stacked to form mesoporous channels; and a gradient channel distribution is formed from the outside to the inside, which is beneficial to the diffusion and mass transfer of macromolecules and reactions, and the alumina carrier has strong impurity holding capacity and is suitable for use in macromolecular heterogeneous catalysis and adsorption reaction processes.

[0028] In the method, the alumina carrier precursor I containing microspherical activated carbon is first immersed in a propylene oxide solution for sealed hydrothermal treatment, the surface particles grow in situ and form flaky particles in the alkaline and alcohol solution under a sealed environment during the reaction process; the spherical activated carbon forms spherical cavities in the alumina matrix during calcination, the alumina carrier precursor II containing the spherical cavities is again immersed in a propylene oxide solution for sealed hydrothermal treatment, the reaction time is relatively short, the alumina grains on the surface of the spherical cavities re-hydrate and form worm-like particles, and the worm-like particles are filled in the spherical cavities and stacked to form a large number of channels with a diameter of 30-50nm. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1SEM image of the surface of the alumina support prepared in Example 1.

[0030] SEM image of the cross section of the alumina support prepared in Example 1.

[0031] Figure 3 SEM image of the surface of the alumina support prepared in Comparative Example 2.

[0032] Figure 4 SEM image of the cross section of the alumina support prepared in Comparative Example 2. DETAILED DESCRIPTION

[0033] The technical solutions and technical effects of the present application are further illustrated below in combination with examples, but are not limited to the following examples. BET method: N2 physical adsorption-desorption is applied to characterize the pore structure of the support in the examples and comparative examples, and the specific operation is as follows: an ASAP-2420 type N2 physical adsorption-desorption instrument is used to characterize the pore structure of the sample. A small amount of sample is vacuum treated at 300 DEG C for 3-4 hours, and finally the product is placed in liquid nitrogen low temperature (-200 DEG C) conditions for nitrogen adsorption-desorption test. Among them, the specific surface area is obtained according to the BET equation, and the distribution rate of the pore volume and the pore diameter below 30 nm is obtained according to the BJH model.

[0034] The scanning electron microscope is applied to characterize the microstructure of the alumina support, and the specific operation is as follows: the JSM-7500F scanning electron microscope is used to characterize the microstructure of the support, the acceleration voltage is 5KV, the acceleration current is 20 mu A, and the working distance is 8mm.

[0035] Micron spherical activated carbon preparation:

[0036] The micron spherical activated carbon used in the method of the present application is prepared according to the method in the literature: Carboxymethyl Cellulose Hydrothermal Carbonization-CO2 Activation for Preparing Micron Spherical Activated Carbon [J]. Forest Products and Industry, 2015, 35 (4): 21-27. The prepared micron spherical activated carbon has a diameter of 1-5 microns. Example 1

[0037] (1) 13.5 grams of the above micron spherical activated carbon and 100 grams of pseudoboehmite are weighed, and the materials are mixed uniformly; then deionized water is added to make the liquid-solid mass ratio in the material 8:1, and the mixed material is mechanically stirred for 2 hours; after stirring, the mixed material is subjected to liquid-solid separation, and the solid material is dried at 130 DEG C for 6 hours; 0.5 grams of sesbania powder is added to the above dried material and mixed uniformly, then an appropriate amount of 0.5% acetic acid solution is added to the mixed material and kneaded uniformly, and the material is extruded into a strip, the formed material is dried at 120 DEG C for 8 hours, and then calcined at 500 DEG C in a nitrogen atmosphere for 5 hours, to obtain an alumina support precursor I.

[0038] (2) Take 100 grams of the alumina carrier precursor I of step (1), add 650 grams of propylene oxide aqueous solution with a mass concentration of 5.5%, and transfer the mixture into an autoclave. After sealing, the autoclave is placed in an oven, and first treated at 75°C for 2.5 hours, and then treated at 140°C for 18 hours. After cooling, the material is washed, filtered, and the solid material is dried at 120°C for 6 hours, and calcined at 500°C in air for 5 hours to obtain the alumina carrier precursor II of the present application.

[0039] (3) Take 100 grams of the alumina carrier precursor II of step (2), add 540 grams of propylene oxide aqueous solution with a mass concentration of 6.7%, and transfer the mixture into an autoclave. After sealing, the autoclave is placed in an oven, and first treated at 80°C for 2.5 hours, and then treated at 135°C for 5.5 hours. After cooling, the material is washed, filtered, and the solid material is dried at 120°C for 6 hours, and calcined at 500°C in air for 5 hours to obtain the alumina carrier S1 of the present application. The outer surface scanning electron microscope image of the carrier is shown in Figure 1 , the cross-section scanning electron microscope image is shown in Figure 2 , and the properties of the carrier are shown in Table 1. Example 2

[0040] The same as example 1, except that the amount of micron spherical activated carbon added in step (1) is 14.5 grams. The concentration of propylene oxide in step (2) is 7.5%, and the solution amount is 450 grams. During hydrothermal treatment, the temperature is raised to 130°C, and the treatment time is 17 hours. The concentration of propylene oxide in step (3) is 4.3%, and the solution amount is 720 grams. During hydrothermal treatment, the temperature is raised to 145°C, and the treatment time is 4.5 hours. The alumina carrier S2 of the present application is obtained, and the properties of the carrier are shown in Table 1. Example 3

[0041] The same as example 1, except that the amount of micron spherical activated carbon added in step (1) is 12.5 grams. The concentration of propylene oxide in step (2) is 6.5%, and the solution amount is 550 grams. During hydrothermal treatment, the temperature is raised to 120°C, and the treatment time is 19 hours. The concentration of propylene oxide in step (3) is 5.6%, and the solution amount is 630 grams. During hydrothermal treatment, the temperature is raised to 155°C, and the treatment time is 3.5 hours. The alumina carrier S3 of the present application is obtained, and the properties of the carrier are shown in Table 1. Example 4

[0042] The same as example 1, except that the amount of microspherical activated carbon added in step (1) is 15.5 g. The concentration of propylene oxide in step (2) is 4.5%, and the amount of solution used is 750 g. During the hydrothermal treatment, the temperature is raised to 150°C, and the treatment time is 16 hours. The concentration of propylene oxide in step (3) is 7.8%, and the amount of solution used is 460 g. During the hydrothermal treatment, the temperature is raised to 125°C, and the treatment time is 6 hours. The alumina carrier S4 of the present application is prepared, and the properties of the carrier are shown in Table 1.

[0043] Comparative Example 1

[0044] The same as example 3, except that the aqueous propylene oxide solution in step (2) and step (3) is replaced by an aqueous ammonia solution of the same mass concentration, and the comparative alumina carrier S5 is prepared. The properties of the carrier are shown in Table 1.

[0045] Comparative Example 2

[0046] The same as example 3, except that the aqueous propylene oxide solution in step (2) and step (3) is replaced by an ethylene oxide solution of the same concentration, and the comparative alumina carrier S6 is prepared. The outer surface scanning electron micrograph of the carrier is shown in Figure 3 , the cross-sectional scanning electron micrograph is shown in Figure 4 , and the properties of the carrier are shown in Table 1.

[0047] Comparative Example 3

[0048] The same as example 3, except that the concentration of propylene oxide in step (2) and step (3) is 1%, and the comparative alumina carrier S7 is prepared. The properties of the carrier are shown in Table 1.

[0049] Comparative Example 4

[0050] The same as example 3, except that the sealed heat treatment in step (2) is a one-step hydrothermal treatment at a temperature of 75°C for a time of 20 hours, and the sealed heat treatment in step (3) is a one-step hydrothermal treatment at a temperature of 80°C for a time of 8 hours, and the comparative alumina carrier S8 is prepared. The properties of the carrier are shown in Table 1.

[0051] Table 1 Properties of Alumina Carriers

[0052] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Support S1 S2 S3 S4 S5 S6 S7 S8 Specific surface area, m 2 / g]] 240 220 218 232 207 212 219 226 Pore volume, mL / g 0.93 0.95 0.91 0.92 0.85 0.87 0.88 0.88 Platelet particle size, nm 120-540 110-530 130-550 125-560 — — — — Pore channel size formed by accumulation of support surface particles, nm 50-260 55-275 60-280 60-270 10-150 15-145 15-160 10-165 Surface platelet particle coverage, % 96 93 91 92 — — — — Worm particle size, nm 85-320 80-330 90-325 80-335 — — — — Spherical cavity filling rate, % 26.5 31.3 35.1 30.7 — — — — Pore channel size formed by accumulation of spherical cavity particles, nm 30-45 30-50 35-45 35-50 5-15 5-15 5-17.5 5-20

[0053] As can be seen from the drawings and Table 1, the alumina carrier prepared by the method of the present application has flaky particles grown in situ on the surface, the coverage of the flaky particles on the surface of the carrier is high, and the flaky particles accumulate to form more open channels. The spherical cavities of the carrier are filled with worm-like particles, and the worm-like particles accumulate to form through channels.

Claims

1. A method for preparing a multi-morphological alumina carrier, characterized in that... The process includes the following: (1) mixing micron-sized spherical activated carbon, boehmite, and water to obtain a slurry. The slurry is then filtered and dried. The dried material is kneaded, shaped, and dried again, and then calcined under an inert atmosphere to obtain alumina carrier precursor I; (2) immersing alumina carrier precursor I in an aqueous propylene oxide solution for a first sealed heat treatment. After treatment, the material is separated into solid and liquid phases. The solid phase is dried and calcined to obtain alumina carrier precursor II; (3) immersing alumina carrier precursor II in an aqueous propylene oxide solution for a second sealed heat treatment. After treatment, the material is separated into solid and liquid phases. The solid material is separated, dried, and calcined to obtain alumina carriers in various forms; the diameter of the micron-sized spherical activated carbon in step (1) is 1-10 μm; the mass ratio of the micron-sized spherical activated carbon to boehmite is 1:4-1:19; the liquid-solid mass ratio of the slurry is 5:1-10:1; the drying temperature in step (1) is 100-160℃, and the drying time is 6-10 hours; the inert atmosphere is nitrogen and / or inert gas, the calcination temperature is 450-700℃, and the calcination time is 4-6 hours; the mass percentage concentration of the propylene oxide aqueous solution in step (2) is 4%- 12%; the mass ratio of propylene oxide aqueous solution to alumina carrier precursor I is 4:1-8:1; the first sealed heat treatment in step (2) is carried out in a sealed container, and the conditions for the first sealed heat treatment are: treatment at 60-100℃ for 1-4 hours, then heating to 110-180℃ for 14-20 hours; the drying temperature in step (2) is 100-160℃, and the drying time is 2-8 hours; the calcination temperature is 450-750℃, and the calcination time is 4-6 hours, and the calcination is carried out in an oxygen-containing atmosphere; the propylene oxide aqueous solution in step (3) The liquid mass percentage concentration is 4%-12%; the mass ratio of propylene oxide aqueous solution to alumina carrier precursor II is 3:1-10:1; the second sealing heat treatment in step (3) is carried out in a sealed container, and the conditions for the second sealing heat treatment are: sealing heat treatment at 60-100℃ for 1-4 hours, then raising the temperature to 110-180℃ and sealing heat treatment for 2-6 hours; the drying temperature in step (3) is 100-160℃, the drying time is 2-8 hours, the calcination temperature is 500-750℃, the calcination time is 4-6 hours, and the calcination is carried out in an oxygen-containing atmosphere.

2. The method according to claim 1, characterized in that: The pseudoboehmite particles described in step (1) have a spherical microstructure and a probable pore size greater than 10 nm.

3. The method according to claim 1, characterized in that: The diameter of the micron-sized spherical activated carbon in step (1) is 1-5 μm; the mass ratio of the micron-sized spherical activated carbon to boehmite is 1:10-1:5.

5.

4. A polymorphic alumina carrier prepared by the method according to any one of claims 1 to 3, characterized in that: The alumina carrier includes an alumina matrix containing spherical cavities and sheet-like alumina grown in situ on the matrix surface, wherein worm-like alumina grows in situ within the spherical cavities.

5. The multimorphic alumina carrier according to claim 4, characterized in that: Worm-like alumina grows in situ in the spherical cavities of the alumina matrix. The size of the worm-like alumina particles is 80-350 nm. The worm-like particles accumulate to form channels of 30-50 nm. The spherical cavity filling rate is 20%-50%.

6. The multimorphic alumina carrier according to claim 4, characterized in that: The diameter of the spherical cavity is 1~10μm; the area of ​​the spherical cavity accounts for 15%~30%.

7. The multimorphic alumina carrier according to claim 4, characterized in that: In situ, lamellar alumina grows on the outer surface of the alumina substrate. The size of the lamellar alumina particles is 100nm-600nm. The lamellar alumina particles are stacked to form channels of 40-300nm. The coverage of the lamellar particles on the outer surface of the alumina substrate is 85%-100%.

8. The multimorphic alumina carrier according to claim 4, characterized in that: The specific surface area of ​​the multi-morphological alumina carrier is 180-320 m². 2 / g, with a pore volume of 0.8-1.2mL / g.

9. The application of a multimorphic alumina support prepared by any one of claims 1 to 3 in macromolecular heterogeneous catalytic reactions or adsorption processes.

10. A hydrogenation catalyst, characterized in that: The catalyst comprises a polymorphic alumina support prepared by any one of claims 1 to 3.

11. The application of the hydrogenation catalyst according to claim 10 in the heavy oil hydrogenation process.

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