An alumina support containing worm-like crystallites and a method for its preparation

Abstract

The application discloses an alumina carrier containing worm-like crystal grains and a preparation method thereof. The alumina carrier containing worm-like crystal grains comprises worm-like alumina crystal grains in-situ grown on the micro-sized spherical cavities and the outer surface of the alumina carrier, the filling rate of the micro-sized spherical cavities is 20-50%, and the coverage rate of the outer surface of the alumina carrier is 90-100%. The preparation method comprises the following steps: immersing the alumina carrier containing micro-sized spherical cavities into an aqueous propylene oxide solution, firstly carrying out sealed heat treatment at 60-100 DEG C for 1-4 hours, then carrying out sealed heat treatment at 110-180 DEG C for 2-6 hours, carrying out solid-liquid separation on the treated material, and carrying out drying and calcination on the solid-phase material to obtain the alumina carrier containing worm-like crystal grains. The worm-like alumina crystal grains in-situ grown on the outer surface and the micro-sized pores of the alumina carrier are stacked to form a large number of macroporous and mesoporous through pores, the alumina carrier can be used for preparing a catalyst for a heterogeneous catalytic reaction, and the preparation method is simple and suitable for industrial application.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of material synthesis, and particularly relates to an alumina carrier containing worm-like grains and a preparation method thereof. BACKGROUND

[0002] Activated alumina is a kind of porous material with excellent physicochemical properties, and is widely used as a catalyst or a carrier. The pore structure of the alumina carrier not only affects the dispersion of the loaded active components, but also is closely related to the activity, selectivity and catalyst life of the catalyst. With the increasing seriousness of crude oil heaviness, the traditional small-pore alumina has been unable to meet the production requirements, and the research and production of mesoporous and macroporous activated alumina are increasingly important.

[0003] CN105983412A discloses a hydrogenation catalyst with high denitrification performance and a preparation method thereof. First, a silicon-containing pseudo-boehmite is prepared, and a carrier is prepared by adding a phosphorus salt in a peptization process using the silicon-containing pseudo-boehmite as a raw material. Finally, the catalyst is prepared by loading active components. Although the catalyst prepared by the method has high pore volume, specific surface area, certain 20-30nm pore content and suitable acid properties, the pore structure on the surface of the catalyst is not conducive to the diffusion of reactant molecules.

[0004] CN109718860A discloses an alumina carrier and a preparation method thereof. The alumina carrier prepared by the method includes a 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 is 1-12μm long and 100-300nm in diameter. The preparation method of the alumina carrier includes mixing the alumina carrier, ammonium bicarbonate and water, then performing sealed heat treatment, and then drying and calcining the material after heat treatment to obtain the alumina carrier. The method adjusts the pore structure of the carrier by growing rod-shaped structure alumina on the surface of the alumina carrier, and the adjustment degree of the rod-shaped structure on the pore is limited. SUMMARY

[0005] In view of the deficiencies in the prior art, the present application provides an alumina carrier containing worm-like grains and a preparation method thereof. The outer surface and the micron-sized cavities of the alumina carrier are in-situ grown with worm-like alumina grains, which accumulate to form a large number of macroporous and mesoporous through pores. The alumina carrier can be used to prepare a catalyst for a heterogeneous catalytic reaction, and the preparation method is simple and suitable for industrial applications.

[0006] The alumina carrier containing worm-like grains of the present application includes worm-like alumina grains in-situ grown in the micron-sized spherical cavities and the outer surface of the alumina carrier.

[0007] The microspherical cavity filling rate of the alumina carrier is 20%-50%; wherein the filling rate refers to the percentage of the worm-like alumina crystal grains in the volume of the microspherical cavity.

[0008] The coverage of the outer surface of the alumina carrier is 90%-100%; wherein the coverage refers to the percentage of the worm-like alumina crystal grains in the area of the outer surface of the alumina carrier.

[0009] The size of the worm-like alumina crystal grains in the alumina carrier is 80nm-350nm.

[0010] The worm-like alumina crystal grains in the microspherical cavity of the alumina carrier accumulate to form 30-50nm channels.

[0011] The worm-like alumina crystal grains on the outer surface of the alumina carrier accumulate to form 30-100nm channels.

[0012] The size of the microspherical cavity in the alumina carrier is preferably 1-3μm.

[0013] The alumina carrier further comprises spherical crystal grains constituting the alumina carrier, and the size of the crystal grains is 80-200nm.

[0014] The specific surface area of the alumina carrier is 170-310m 2 / g, the pore volume is 0.8-1.0mL / g, and the channels of 8.5-20nm account for 50%-75% of the total pore volume.

[0015] The method for preparing the alumina carrier containing worm-like crystal grains comprises the following steps: immersing the alumina carrier containing microspherical cavities into an aqueous propylene oxide solution, first carrying out sealed heat treatment at 60-100℃ for 1-4 hours, then carrying out sealed heat treatment at 110-180℃ for 2-6 hours, carrying out solid-liquid separation on the treated material, and carrying out drying and calcination on the solid material to obtain the alumina carrier containing worm-like crystal grains.

[0016] In the method, the alumina carrier containing microspherical cavities is prepared by the following method: mixing pseudo-boehmite and microspherical activated carbon, adding deionized water into the mixture to form a slurry, carrying out liquid-solid separation and drying treatment on the slurry, and carrying out mixing, molding, drying and calcination on the dried material to obtain the alumina carrier containing microspherical cavities.

[0017] The pseudo-boehmite particles are generally in the form of granules, which can be commercially available products or prepared by methods such as acid precipitation, alkali precipitation and alcohol aluminum hydrolysis, and the pseudo-boehmite with a pore diameter of 8.5-15nm is preferred.

[0018] The micrometer spherical activated carbon has a diameter of 1-3 micrometers, which can be prepared by existing methods or purchased.

[0019] The mass ratio of the activated carbon to pseudo-boehmite is 1:19-1:32, and the amount of deionized water added is such that the mass ratio of liquid to solid in the slurry is 5:1-10:1.

[0020] The kneading and molding are performed by conventional methods in the art, and an extrusion aid and a peptizing agent are added as needed during molding. The extrusion aid is pearl millet powder, and the amount added is 0.1wt%-0.5wt% of the weight of the final 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 0.1wt%-1.5wt% of the weight of the alumina carrier, and the final amount is determined according to the molding effect. The drying temperature is 100-160℃, and the drying time is 4-10 hours; the calcination temperature is 450-700℃, preferably 450-600℃, and the calcination time is 4-6 hours; and the calcination is performed in an oxygen-containing atmosphere.

[0021] In the method of the application, the mass percentage concentration of the propylene oxide aqueous solution is 2.5%-12%, preferably 4%-8%, and the mass ratio of the amount of propylene oxide aqueous solution to the mass of the alumina carrier precursor is 3:1-10:1, preferably 4:1-8:1.

[0022] In the method of the application, the sealing heat treatment is preferably performed in a sealed autoclave, and the sealing heat treatment is preferably first performed at 60-100℃ for 1-4 hours, and then performed at 120-160℃ for 2-6 hours.

[0023] In the method of the application, the drying temperature is 100-160℃, and 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 performed in an oxygen-containing atmosphere, preferably an air atmosphere.

[0024] The application of the alumina carrier of the application in macromolecular heterogeneous catalytic reactions is particularly suitable for the field of heavy oil hydroprocessing.

[0025] The application also provides a hydrogenation catalyst comprising the alumina carrier described above.

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

[0027] The inventive alumina carrier has worm-like alumina grains in-situ grown on the surface and in the micro-sized cavities. The worm-like grains on the surface of the carrier are accumulated to form open channels of 30-100 nm in size, which are beneficial for the diffusion of reactant molecules. The worm-like alumina grains in the micro-sized spherical cavities are accumulated to form channels of 30-50 nm in size, and the content of channels of 8.5-20 nm in size in the interior of the carrier is high. The inventive alumina carrier has a channel distribution suitable for the mass transfer of macromolecular materials, and can be used to prepare catalysts for macromolecular heterogeneous catalytic reactions. The preparation method is simple and suitable for industrial applications. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is an SEM image of the surface of the alumina carrier prepared in Example 1.

[0029] Figure 2 Figure 2 is an SEM image of the cross-section of the alumina carrier prepared in Example 1.

[0030] Figure 3 is an SEM image of the surface of the alumina carrier prepared in Comparative Example 2.

[0031] Figure 4 Figure 4 is an SEM image of the cross-section of the alumina carrier prepared in Comparative Example 2. DETAILED DESCRIPTION

[0032] The technical solutions and technical effects of the present application will be further illustrated below in combination with examples, but are not limited to the following examples. In the present application, wt% represents mass fraction.

[0033] BET method: N2 physical adsorption-desorption was used to characterize the pore structure of the carriers in the examples and comparative examples, and the specific operation was as follows: an ASAP-2420 type N2 physical adsorption-desorption instrument was used to characterize the pore structure of the samples. A small amount of sample was vacuum treated at 300℃ for 3-4 hours, and finally the product was placed in liquid nitrogen at low temperature (-200℃) for nitrogen adsorption-desorption test. The specific surface area was obtained according to the BET equation, and the distribution rate of pore volume and pore diameter below 30 nm was obtained according to the BJH model.

[0034] Scanning electron microscopy was used to characterize the microstructure of the alumina carrier, and the specific operation was as follows: a JSM-7500F scanning electron microscope was used to characterize the microstructure of the carrier, with an acceleration voltage of 5KV, an acceleration current of 20µA, and a working distance of 8mm. Example 1

[0035] (1) Take 500 grams of pseudo-boehmite (with a few pores of 10 nm in diameter), 24 grams of micron-spherical activated carbon with a diameter of 1-3 microns, mix them well, then add 3000 grams of deionized water and stir for 2 hours. Filter the mixture and dry it at 140°C for 6 hours. Add 1.8 grams of sesbania powder to the dried material, mix well, then add an appropriate amount of 0.5% acetic acid solution to the mixture and knead it well. Extrude the mixture into strips, dry the strips at 145°C for 6 hours, and calcine them at 500°C for 5 hours to obtain an alumina carrier precursor.

[0036] (2) Take 100 grams of the alumina carrier precursor obtained in step (1), add 550 grams of a propylene oxide aqueous solution with a mass concentration of 6.4%, and transfer the mixture into an autoclave. Seal the autoclave and place it in an oven for sealed treatment at 85°C for 2 hours, then raise the temperature to 145°C for sealed treatment for 3.5 hours. After the treatment, cool the material, wash it, filter it, dry the solid material at 140°C for 6 hours, and calcine it at 550°C for 5 hours to obtain an alumina carrier S1. The outer surface scanning electron microscope image of the alumina carrier S1 is shown in Figure 1 , the cross-sectional scanning electron microscope image is shown in Figure 2 , and the carrier properties are shown in Table 1. Example 2

[0037] The same as in Example 1, except that the amount of micron-spherical activated carbon added in step (1) is 18 grams. In step (2), the concentration of propylene oxide is 5.5%, and the amount of solution used is 650 grams. During the hydrothermal treatment, first treat at 75°C for 2.5 hours, then at 135°C for 4.5 hours to obtain an alumina carrier S2. The carrier properties are shown in Table 1. Example 3

[0038] The same as in Example 1, except that the amount of micron-spherical activated carbon added in step (1) is 16 grams. In step (2), the concentration of propylene oxide is 7.7%, and the amount of solution used is 450 grams. During the hydrothermal treatment, first treat at 65°C for 3 hours, then at 155°C for 2.5 hours to obtain an alumina carrier S3. The carrier properties are shown in Table 1. Example 4

[0039] The same as in Example 1, except that the amount of micron-spherical activated carbon added in step (1) is 25 grams. In step (2), the concentration of propylene oxide is 4.3%, and the amount of solution used is 750 grams. During the hydrothermal treatment, first treat at 95°C for 1.5 hours, then at 125°C for 5.5 hours to obtain an alumina carrier S4. The carrier properties are shown in Table 1.

[0040] Comparative Example 1

[0041] The same as in Example 1, except that in step (2), the propylene oxide aqueous solution is replaced by an ammonia solution with the same mass concentration to obtain an alumina carrier S5. The carrier properties are shown in Table 1.

[0042] Comparative Example 2

[0043] The same as Example 1 except that in step (2) the propylene oxide aqueous solution is replaced by an ethylene oxide solution of the same concentration to produce an alumina carrier S6. The outer surface scanning electron micrograph of the alumina carrier is shown in Figure 3 , the cross-section scanning electron micrograph is shown in Figure 4 , and the carrier properties are shown in Table 1.

[0044] Comparative Example 3

[0045] The same as Example 1 except that in step (2) the propylene oxide concentration is 0.8% to produce an alumina carrier S7. The carrier properties are shown in Table 1.

[0046] Comparative Example 4

[0047] The same as Example 1 except that in step (2) the hydrothermal treatment is one-step hydrothermal treatment at 85°C for 5.5 hours to produce an alumina carrier S8. The carrier properties are shown in Table 1.

[0048] Table 1 Alumina Carrier Properties

[0049] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Catalyst S1 S2 S3 S4 S5 S6 S7 S8 Specific surface area, m 2 / g]] 225 236 218 247 203 192 213 218 Pore volume, mL / g 0.92 0.93 0.95 0.91 0.81 0.83 0.85 0.86 8.5-20 nm pore content, % 63.3 61.1 57.9 65.2 41.1 42.6 45.2 45.6 Support surface vermicular alumina coverage, % 95 93 96 91 — — — 96 Support surface vermicular alumina stacking pore size, nm 30-90 40-95 35-95 35-90 10-90 10-95 15-90 10-90 Micron-sized spherical cavity vermicular alumina filling rate, % 33.5 29.5 35.5 31.5 — — — — Micron-sized spherical cavity vermicular alumina stacking pore size, nm 30-45 30-40 30-50 35-45 — — — —

[0050] From the data in Table 1 and Figures 1-4 it can be seen that compared with the comparative alumina carrier, the alumina carrier produced by the method of the present application has a wide open surface macropore channel and a high content of 8.5-20 nm channels in the carrier interior.

Claims

1. An alumina carrier containing worm-like grains, characterized in that: The alumina carrier includes micron-sized spherical cavities and worm-like alumina grains on its outer surface, which are grown in situ on an alumina support. The preparation method of the alumina support containing worm-like grains includes the following steps: immersing the alumina support containing micron-sized spherical cavities in an aqueous solution of propylene oxide; first, performing a sealed heat treatment at 60-100℃ for 1-4 hours, then performing a sealed heat treatment at 110-180℃ for 2-6 hours; after treatment, the material undergoes solid-liquid separation, and the solid phase is dried and calcined to obtain the alumina support containing worm-like grains; the alumina support containing micron-sized spherical cavities is prepared by the following method: mixing boehmite and micron-sized spherical activated carbon; adding deionized water to the mixed material to form a slurry; performing liquid-solid separation and drying treatment; and then kneading, shaping, drying, and calcining the dried material. The process involves calcination to obtain an alumina support containing micron-sized spherical cavities. The mass ratio of activated carbon to boehmite is 1:19-1:32, and the amount of deionized water added is such that the liquid-solid mass ratio in the slurry is 5:1-10:

1. The mass percentage concentration of the propylene oxide aqueous solution is 4%-12%, and the mass ratio of the propylene oxide aqueous solution to the alumina support precursor is 3:1-10:

1. The sealing heat treatment is carried out in a closed high-pressure autoclave, first at 60-100℃ for 1-4 hours, and then at 120-160℃ for 2-6 hours. The drying temperature is 100-160℃, and the drying time is 2-8 hours. The calcination temperature is 500-750℃, and the calcination time is 4-6 hours, calcined in an oxygen-containing atmosphere.

2. The alumina carrier according to claim 1, characterized in that: The micron-sized spherical cavity has a filling rate of 20%-50%; wherein the filling rate refers to the percentage of worm-like alumina grains in the volume of the micron-sized spherical cavity.

3. The alumina carrier according to claim 1, characterized in that: The coverage rate of the outer surface of the alumina carrier is 90%-100%; wherein the coverage rate refers to the percentage of the area of ​​the outer surface of the alumina carrier occupied by worm-like alumina grains.

4. The alumina carrier according to claim 1, characterized in that: The worm-like alumina grains have a size of 80nm-350nm.

5. The alumina carrier according to claim 1, characterized in that: The micron-sized spherical cavity contains worm-like alumina grains that accumulate to form pores of 30-50 nm.

6. The alumina carrier according to claim 1, characterized in that: The worm-like alumina grains on the outer surface of the alumina carrier accumulate to form pores of 30-100 nm.

7. The alumina carrier according to claim 1, characterized in that: The size of the micron-sized spherical cavity is 1-3 μm.

8. The alumina carrier according to claim 1, characterized in that: The alumina support also includes spherical grains that constitute the alumina support, with a grain size of 80-200 nm.

9. The alumina carrier according to claim 1, characterized in that: The specific surface area of ​​the alumina carrier is 170-310 m². 2 / g, with a pore volume of 0.8-1.0mL / g, and pores of 8.5-20nm accounting for 50%-75% of the total pore volume.

10. A method for preparing an alumina carrier containing worm-like grains as described in any one of claims 1 to 8, characterized in that... The process includes the following steps: immersing an alumina carrier containing micron-sized spherical cavities into an aqueous solution of propylene oxide, first performing a sealed heat treatment at 60-100℃ for 1-4 hours, then performing a sealed heat treatment at 110-180℃ for 2-6 hours, and finally performing solid-liquid separation on the treated material. The solid phase material is then dried and calcined to obtain an alumina carrier containing worm-like crystals.

11. The method according to claim 10, characterized in that: The alumina carrier containing micron-sized spherical cavities is prepared by the following method: Boehmite and micron-sized spherical activated carbon are mixed, and deionized water is added to the mixed material to form a slurry. After liquid-solid separation and drying, the dried material is kneaded, shaped, dried and calcined to obtain the alumina carrier containing micron-sized spherical cavities.

12. The method according to claim 11, characterized in that: The pseudoboehmite particles are granular in shape, and the approximate pore size of the pseudoboehmite is 8.5-15 nm.

13. The method according to claim 11, characterized in that: The diameter of the micron-sized spherical activated carbon is 1-3 μm.

14. The method according to claim 11, characterized in that: The mass ratio of activated carbon to boehmite is 1:19-1:32, and the amount of deionized water added is such that the liquid-solid mass ratio in the slurry is 5:1-10:

1.

15. The method according to claim 10, characterized in that: The propylene oxide aqueous solution has a mass percentage concentration of 4%-12%, and the mass ratio of the propylene oxide aqueous solution to the alumina carrier precursor is 3:1-10:

1.

16. The method according to claim 10, characterized in that: The sealing heat treatment is carried out in a closed high-pressure autoclave; the sealing heat treatment is first performed at 60-100℃ for 1-4 hours, and then at 120-160℃ for 2-6 hours.

17. The method according to claim 11, characterized in that: The drying temperature is 100-160℃, and 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.

18. The application of the alumina support containing worm-like crystals as described in any one of claims 1 to 8 in macromolecular heterogeneous catalytic reactions.

19. A hydrogenation catalyst, characterized in that: The catalyst comprises the alumina support containing worm-like crystals as described in any one of claims 1 to 8.

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