Alumina support, method for preparing the same and use thereof

Abstract

The application discloses an alumina carrier and a preparation method and application thereof. The alumina carrier comprises bulk alumina and sheet alumina. The bulk alumina contains microspherical cavities, and the size of the spherical particles is 80-200 nm; the sheet alumina is in-situ grown on the outer surface of the bulk alumina and in the microspherical cavity channel, and the size of the sheet alumina grains is 100-600 nm; the sheet alumina grains on the outer surface are stacked to form a channel with a size of 40-300 nm, and the coverage rate of the outer surface is 85%-100%; the sheet alumina grains in the microspherical cavity are stacked to form a channel with a size of 50-100 nm, and the filling rate of the microspherical cavity channel is 40%-80%. The alumina carrier is obtained by treating the alumina carrier containing microspherical cavities in propylene oxide. The alumina carrier can be used for preparing a catalyst for a heterogeneous catalytic reaction, and is particularly suitable for the field of heavy oil hydroprocessing.

Description

TECHNICAL FIELD

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

[0002] Active 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 service life of the catalyst. With the increasing severity of crude oil, the traditional small-pore alumina cannot meet the production requirements, and the research and production of mesoporous and macroporous active alumina are increasingly important.

[0003] CN107913691A discloses an alumina carrier containing macropores and a preparation method thereof. First, pseudo-boehmite powder and sesbania powder are mixed uniformly in a kneader, then a butadiene-styrene rubber emulsion with a particle size of 10-500 nm is prepared, and an organic acid or an inorganic acid is added thereto; then the acid solution containing the butadiene-styrene rubber emulsion is added to the pseudo-boehmite powder and the sesbania powder and kneaded uniformly, and then extruded, molded, dried and calcined to obtain the alumina carrier containing macropores. The method uses butadiene-styrene rubber emulsion as a pore expander, and although a carrier material with a pore size distribution of 60-400 nm can be prepared, the large pore size of the carrier leads to low utilization of macropores. In addition, the high macropore size affects the mechanical strength of the carrier.

[0004] CN109718860A discloses an alumina carrier and a preparation method thereof. The alumina carrier prepared by the method comprises 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 has a length of 1-12 µm and a diameter of 100-300 nm. The preparation method of the alumina carrier comprises mixing the alumina carrier, ammonium bicarbonate and water, then sealing and heat-treating, and then drying and calcining the heat-treated material 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, but the rod-shaped alumina grown on the surface is easy to fall off, and the bonding strength with the main body alumina needs to be further improved. SUMMARY

[0005] In view of the deficiencies in the prior art, the present application provides an alumina carrier and a preparation method thereof. The alumina carrier prepared by the method has flaky alumina grains grown in situ on the outer surface and the micron-sized pores, the flaky alumina grains on the surface are stacked to form beneficial internal diffusion pores, and the flaky particles in the micron-sized pores are stacked to form through pores. The alumina carrier can be used to prepare a catalyst for a heterogeneous catalytic reaction, and is particularly suitable for the field of heavy oil hydroprocessing.

[0006] The alumina carrier of the present application comprises bulk alumina and sheet alumina. The bulk alumina is composed of spherical particles, the bulk alumina contains microspherical cavities, and the sheet alumina is grown in situ on the outer surface of the bulk alumina and in the microspherical cavities, and the sheet alumina has a grain size of 100-600 nm; the microspherical cavity filling rate is 40-80%, wherein the filling rate refers to the percentage of the volume of the sheet alumina grain in the microspherical cavity in the volume of the microspherical cavity.

[0007] In the alumina carrier of the present application, the sheet alumina grains in the microspherical cavities are stacked to form 50-100 nm channels.

[0008] In the alumina carrier of the present application, the sheet alumina grains on the outer surface of the bulk alumina are stacked to form 40-300 nm channels, and the outer surface coverage is 85-100%, wherein the coverage refers to the percentage of the surface occupied by the sheet alumina grains on the outer surface of the bulk alumina in the outer surface of the bulk alumina.

[0009] In the alumina carrier of the present application, the spherical particle grain size is 80-200 nm.

[0010] The specific surface area of the alumina carrier of the present application is 160-320 m 2 / g, the pore volume is 0.8-1.2 mL / g, the most probable pore size is 10-30 nm, and the channels of 10-30 nm account for 55-80% of the total pore volume.

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

[0012] (1) preparing an alumina carrier precursor containing microspherical cavities;

[0013] (2) immersing the alumina carrier precursor obtained in step (1) in an aqueous propylene oxide solution and sealing for heat treatment, then separating the solid and liquid after treatment, drying and calcining the solid material to obtain the alumina carrier.

[0014] In the method of the present application, the alumina carrier precursor containing microspherical cavities in step (1) is γ-alumina; its shape can be the shape of a conventional alumina carrier, such as spherical, and its particle size is generally 2-8.0 mm, such as cylindrical bar, clover, four-leaf clover, etc., and its diameter is about 0.2-3.0 mm and its length is about 3-8.0 mm. The microspherical cavity diameter is 1-10 microns, and the microspherical cavity content can be controlled as needed, preferably the microspherical cavity pore volume accounts for 1-30% of the total pore volume of the alumina carrier precursor, more preferably 5-20%.

[0015] In the method, the alumina carrier precursor containing microspherical cavities in step (1) can be prepared by the following method: mixing microspherical activated carbon and pseudoboehmite, adding deionized water to the mixture and stirring, drying the mixture, and then mixing and kneading the dried mixture into a shape, drying and calcining the mixture to obtain the alumina carrier precursor; the microspherical activated carbon can be prepared by an existing method or purchased, and the diameter of the microspherical activated carbon is 1-10 microns; the mass ratio of the microspherical activated carbon to the pseudoboehmite is 1:4-1:9; the amount of the deionized water added is such that the mass ratio of liquid to solid in the slurry is 5:1-10:1; the stirring can be completed by magnetic stirring or mechanical stirring, and the stirring time is 1-4 hours; the mixing and kneading into a shape is performed by a conventional method in the art, and a deagglomeration agent and a peptizing agent can be added during the shaping process as needed; the deagglomeration agent is pearl millet powder, and the amount of the deagglomeration agent 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 of the peptizing agent added is 0.5wt%-1.5wt% of the weight of the alumina carrier; the drying temperature is 100-160℃, and the drying time is 6-10 hours; the calcination temperature is 450-700℃, and the calcination time is 4-6 hours; and the calcination is performed in an oxygen-containing atmosphere.

[0016] In the method, 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 amount of the propylene oxide aqueous solution to the alumina carrier precursor is 3:1-10:1, preferably 4:1-8:1.

[0017] In the method, the sealing heat treatment in step (2) is performed in a closed container, and the closed container is preferably an autoclave; the sealing heat treatment is first performed at a low temperature of 60-100℃ for 1-4 hours, and then performed at a temperature of 110-180℃, preferably 120-160℃, for 14-20 hours.

[0018] In the method, 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.

[0019] The application of the alumina carrier in the method to a heterogeneous catalytic reaction, and particularly to the field of heavy oil hydroprocessing.

[0020] The application also provides a hydrogenation catalyst, which comprises the alumina carrier.

[0021] Compared with the prior art, the present application has the following advantages: firstly, the alumina carrier precursor containing micrometer-sized channels is prepared, and then the alumina carrier precursor is immersed in a propylene oxide solution for sealed hydrothermal treatment. During the low-temperature sealed heat treatment, propylene oxide is hydrolyzed to form an alcohol solution, and the solution is weakly alkaline. During the high-temperature sealed hydrothermal treatment, the alumina grains on the surface of the alumina carrier and in the micrometer-sized channels grow in situ to form flaky alumina grains under the alkaline and alcohol solution environment. The flaky alumina grains on the surface are stacked to form open channels with a size of 40-300 nm, which is beneficial to the diffusion of reactant molecules, especially larger reactant molecules, into the interior of the carrier. The flaky alumina grains in the micrometer-sized channels are stacked to form channels with a size of 50-100 nm, which are well connected. The flaky alumina grains on the surface and in the micrometer-sized channels are uniform in size, and the flaky alumina coverage and filling rate on the surface and in the micrometer-sized channels are high, and the flaky alumina has a significant channel adjusting effect on the carrier. Due to the secondary growth of the alumina grains in the rest part of the carrier, the particle stacking state is changed, so that the carrier has a high content of channels with a size of 10-30 nm. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is an SEM image of the surface of the alumina carrier precursor prepared in Example 1.

[0023] Figure 2 Figure 2 is an SEM image of the cross section of the alumina carrier precursor prepared in Example 1.

[0024] Figure 3 Figure 3 is an SEM image of the surface of the alumina carrier prepared in Example 1.

[0025] Figure 4 is an SEM image of the cross section of the alumina carrier prepared in Example 1. EMBODIMENT

[0026] 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 used to characterize the pore structure of the carriers 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 samples. A small amount of sample is vacuum treated at 300°C for 3-4 hours, and finally the product is placed in liquid nitrogen at low temperature (-200°C) for nitrogen adsorption-desorption test. 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.

[0027] The scanning electron microscope is used to characterize the microstructure of the alumina carrier, and the specific operation is as follows: a JSM-7500F scanning electron microscope is 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.

[0028] Preparation of microspherical activated carbon:

[0029] The microspherical activated carbon used in the method of the present application is prepared according to the method in the document: Preparation of microspherical activated carbon by hydrothermal carbonization of carboxymethylcellulose-CO2 activation [J]. Wood Chemistry and Industry, 2015, 35(4): 21-27. The diameter of the prepared microspherical activated carbon is 1-10 microns. Example 1

[0030] (1) Preparation of alumina carrier precursor

[0031] 100 grams of the above microspherical activated carbon, 600 grams of pseudoboehmite, and deionized water were mixed to obtain a mixture with a liquid-to-solid mass ratio of 8:1. The mixture was mechanically stirred for 2 hours. After stirring, the mixture was subjected to liquid-solid separation, and the solid material was dried at 130°C for 6 hours. Then, 4.5 grams of sesbania powder was added to the dried material and mixed uniformly. An appropriate amount of 0.5% acetic acid solution was added to the mixture and kneaded uniformly. The mixture was extruded into a strip and dried at 130°C for 8 hours. The dried material was calcined at 600°C in an oxygen atmosphere for 5 hours to obtain the alumina carrier precursor S0. The properties of the alumina carrier precursor are shown in Table 1, the scanning electron microscope image of the outer surface of the carrier is shown in Figure 1 , and the cross-sectional scanning electron microscope image is shown in Figure 2 .

[0032] (2) Preparation of alumina carrier

[0033] 100 grams of the alumina carrier precursor prepared in step (1) was added to 650 grams of propylene oxide aqueous solution with a mass concentration of 5.2%. The mixture was transferred into an autoclave, which was then sealed and placed in an oven. The sealed autoclave was first treated at 85°C for 2 hours, and then treated at 150°C for 17 hours. After cooling, the material was washed and filtered. The solid material was dried at 120°C for 6 hours and calcined at 650°C for 5 hours to obtain the alumina carrier S1 of the present application. The properties of the alumina carrier are shown in Table 1, the scanning electron microscope image of the outer surface of the carrier is shown in Figure 3 , and the cross-sectional scanning electron microscope image is shown in Figure 4 . Example 2

[0034] The same as Example 1, except that the amount of pseudoboehmite added in step (1) was 700 grams, and the liquid-to-solid mass ratio during stirring was 7:1. In step (2), the concentration of propylene oxide was 6.5%, and the amount of solution used was 520 grams. During hydrothermal treatment, the sealed autoclave was first treated at 75°C for 2.5 hours, and then treated at 140°C for 18 hours to obtain the alumina carrier S2 of the present application. The properties of the alumina carrier are shown in Table 1. Example 3

[0035] The same as example 1, except that the amount of pseudo-boehmite added in step (1) is 500 g and the liquid-to-solid mass ratio during stirring is 6:1. In step (2), the concentration of propylene oxide is 4.6% and the amount of solution used is 740 g. During hydrothermal treatment, the temperature is first raised to 95°C and the mixture is treated for 1.5 hours in a sealed autoclave. Then the temperature is raised to 160°C and the mixture is treated for 16 hours. The alumina support S3 of the present application is obtained. The properties of the support are shown in Table 1. Example 4

[0036] The same as example 1, except that the amount of pseudo-boehmite added in step (1) is 800 g and the liquid-to-solid mass ratio during stirring is 9:1. In step (2), the concentration of propylene oxide is 7.7% and the amount of solution used is 450 g. During hydrothermal treatment, the temperature is first raised to 65°C and the mixture is treated for 3.5 hours in a sealed autoclave. Then the temperature is raised to 130°C and the mixture is treated for 19 hours. The alumina support S4 of the present application is obtained. The properties of the support are shown in Table 1.

[0037] Comparative Example 1

[0038] The same as example 3, except that the propylene oxide aqueous solution is replaced by an aqueous ammonia solution of the same mass concentration. The comparative alumina support S5 is obtained. The properties of the support are shown in Table 1.

[0039] Comparative Example 2

[0040] The same as example 3, except that the propylene oxide aqueous solution is replaced by an ethylene oxide solution of the same concentration. The comparative alumina support S6 is obtained. The properties of the support are shown in Table 1.

[0041] Comparative Example 3

[0042] The same as example 3, except that the concentration of propylene oxide is 1%. The comparative alumina support S7 is obtained. The properties of the support are shown in Table 1.

[0043] Comparative Example 4

[0044] The same as example 3, except that the sealed hydrothermal treatment is one-step hydrothermal treatment at a temperature of 85°C for 20 hours. The comparative alumina support S8 is obtained. The properties of the support are shown in Table 1.

[0045] Comparative Example 5

[0046] The same as example 3, except that the mixture is not transferred into an autoclave for sealed treatment, but is treated under normal pressure in a condensation reflux device. The comparative alumina support S9 is obtained. The properties of the support are shown in Table 1.

[0047] Table 1 Properties of alumina supports

[0048] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Support S0 S1 S2 S3 S4 S5 S6 S7 S8 S9 Specific surface area, m 2 / g]] 265 213 226 208 211 243 251 256 260 251 Pore volume, mL / g 0.89 0.90 0.91 0.89 0.93 0.85 0.88 0.87 0.88 0.82 10-30 nm pore content, % 45.3 62.7 58.2 64.2 58.3 47.3 46.5 47.1 46.9 46.4 Surface sheet alumina coverage, % — 93 90 94 96 — — — — — Crystal size of sheet alumina, nm — 120-580 110-550 100-560 130-550 — — — — — Pore size formed by accumulation of surface sheet alumina of the support, nm 10-130 45-260 50-255 55-270 45-240 10-150 10-130 15-145 10-140 15-150 Sheet alumina filling rate of micrometer scale pores, % — 43.5 45.7 50.1 49.6 — — — — — Pore size formed by accumulation of sheet alumina within micrometer scale pores, nm — 60-90 55-95 50-85 65-90 — — — — —

[0049] From Figure 1 、 2 , Figure 3 ,4 It can be seen that the surface accumulation of the flaky particles of the alumina support prepared by the method of the present application forms a large number of pores for the internal diffusion of macromolecular reactants, and the accumulation of the flaky alumina particles grown in situ in the microscale pores of the alumina support precursor forms a large number of through pores.

[0050] As can be seen from Table 1, the alumina support prepared by the method of the present application has a higher content of 10-30 nm pores, and the surface pores of the support are wide and the internal pores are better through.

Claims

1. An alumina support, characterized by: The alumina carrier comprises a main body alumina and flaky alumina, the main body alumina is composed of spherical particles, the main body alumina contains microspherical cavities, the flaky alumina is in-situ grown on the outer surface of the main body alumina and in the microspherical cavities, the flaky alumina has a grain size of 100-600 nm; the microspherical cavity filling rate is 40-80%, wherein the filling rate refers to the percentage of the volume of the flaky alumina grains in the microspherical cavities to the volume of the microspherical cavities; the flaky alumina grains in the microspherical cavities are stacked to form 50-100 nm channels; the flaky alumina grains on the outer surface of the main body alumina are stacked to form 40-300 nm channels, and the outer surface coverage is 85-100%, wherein the coverage refers to the percentage of the surface of the main body alumina covered by the flaky alumina grains to the outer surface of the main body alumina; the preparation method of the alumina carrier comprises the following steps: (1) preparing an alumina carrier precursor containing microspherical cavities; (2) immersing the alumina carrier precursor obtained in step (1) in an aqueous propylene oxide solution for sealed heat treatment, performing solid-liquid separation on the treated material, drying and calcining the solid-phase material to obtain the alumina carrier; the alumina carrier precursor containing microspherical cavities in step (1) is prepared by the following method: mixing microspherical activated carbon and pseudoboehmite, adding deionized water to the mixture and stirring, drying the stirred material, and mixing and kneading the dried material into a shape, drying and calcining to obtain the alumina carrier precursor; the microspherical activated carbon has a diameter of 1-10 microns; the mass ratio of the microspherical activated carbon to the pseudoboehmite is 1:4-1:9; the amount of deionized water added is such that the liquid-solid mass ratio of the stirred material is 5:1-10:1; the drying temperature is 100-160 DEG C, and the drying time is 6-10 hours; the calcination temperature is 450-700 DEG C, the calcination time is 4-6 hours, and the calcination is performed in an oxygen-containing atmosphere; the aqueous propylene oxide solution has a mass percentage concentration of 2.5-12%, and the mass ratio of the aqueous propylene oxide solution to the alumina carrier precursor is 3:1-10:1; the sealed heat treatment in step (2) is performed in a sealed container, and the sealed heat treatment is first performed at a low temperature of 60-100 DEG C for 1-4 hours, and then performed at 110-180 DEG C for 14-20 hours.

2. The alumina support of claim 1, wherein: The spherical particle has a grain size of 80-200 nm.

3. The alumina support of claim 1, wherein: The specific surface area is 160-320 m 2 / g, the pore volume is 0.8-1.2 mL / g, the most probable pore diameter is 10-30 nm, and the pores with a diameter of 10-30 nm account for 55%-80% of the total pore volume.

4. A process for the production of the alumina carrier according to any one of claims 1 to 3, characterized in that The method comprises the following steps: (1) preparing an alumina carrier precursor containing microspherical cavities; (2) immersing the alumina carrier precursor obtained in step (1) in an aqueous propylene oxide solution for sealed heat treatment, performing solid-liquid separation on the treated material, drying and calcining the solid-phase material to obtain the alumina carrier.

5. The method of claim 4, wherein: The alumina carrier precursor containing microspherical cavities in step (1) is γ-phase alumina; the microspherical cavities have a diameter of 1-10 microns, and the microspherical cavity pore volume accounts for 1-30% of the total pore volume of the alumina carrier precursor.

6. The method of claim 4, wherein: The alumina carrier precursor containing microspherical cavities in step (1) is prepared by the following method: micron spherical activated carbon is mixed with pseudoboehmite, deionized water is added to the mixture and stirred, the stirred mixture is dried, the dried mixture is kneaded, shaped, dried and calcined to obtain the alumina carrier precursor; the micron spherical activated carbon has a diameter of 1-10 microns; the mass ratio of the micron spherical activated carbon to the pseudoboehmite is 1:4-1:9; the amount of the deionized water added is such that the liquid-solid mass ratio of the stirred mixture is 5:1-10:1; the drying temperature is 100-160°C, and the drying time is 6-10 hours; the calcination temperature is 450-700°C, and the calcination time is 4-6 hours, and the calcination is performed in an oxygen-containing atmosphere.

7. The method of claim 4, wherein: The mass percentage concentration of the propylene oxide aqueous solution in step (2) is 2.5%-12%, and the mass ratio of the propylene oxide aqueous solution to the alumina carrier precursor is 3:1-10:

1.

8. The method of claim 4, wherein: The sealing heat treatment in step (2) is performed in a sealed container, and the sealing heat treatment is first performed at a low temperature of 60-100°C for 1-4 hours, and then performed at a temperature of 110-180°C for 14-20 hours.

9. The method of claim 4, wherein: The drying temperature in step (2) is 100-160°C, the drying time is 2-8 hours, the calcination temperature is 450-750°C, and the calcination time is 4-6 hours, and the calcination is performed in an oxygen-containing atmosphere.

10. Use of the alumina carrier in any one of claims 1-3 in a heterogeneous catalytic reaction.

11. A hydrogenation catalyst characterized by: The catalyst comprises the alumina carrier in any one of claims 1-3.

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