A method for the preparation of an alumina support

Abstract

The application aims to provide a preparation method of an alumina carrier, and belongs to the field of material synthesis. When the alumina carrier is prepared, pseudo-boehmite with an elliptical sheet shape is selected as part of raw materials. The pseudo-boehmite with the elliptical sheet shape is stacked to form a large number of large pore channels. Therefore, the pore channel structure of the carrier can be flexibly regulated by adjusting the addition amount of the pseudo-boehmite with the elliptical sheet shape, so as to meet the demand of different reactions on the pore channel structure of the catalyst.

Description

TECHNICAL FIELD

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

[0002] As a traditional catalyst carrier material, alumina has the characteristics of mature preparation technology, adjustable pore structure, low use cost and easy processing into a shape, and is widely used in the preparation of oil refining and chemical catalysts. As an important component of the catalyst, the carrier can improve the dispersion effect of the active component on the one hand, and on the other hand, its pore structure provides diffusion channels for reactant molecules and product molecules, thereby improving the utilization efficiency of the metal. Macroporous carrier materials have the characteristics of small mass transfer resistance and high efficiency. In recent years, as the core component of the catalyst, alumina, molecular sieve and activated carbon with macroporous structure have been widely studied to improve the use efficiency of the catalyst. According to the synthesis process, macroporous materials can be divided into two categories: one is to directly synthesize a new carrier material with macroporous structure in the synthesis process, and the other is to obtain a carrier material with macroporous structure by post-modification of the material.

[0003] CN201510191156.7 discloses a heavy oil hydrogenation catalyst and a preparation method thereof. The catalyst comprises an alumina carrier composed of flaky polycrystalline γ-alumina and hydrogenation active metal. The preparation method of the catalyst is as follows: flaky γ-polycrystalline alumina raw powder is added into a binder and a extrusion aid, kneaded, formed, dried and calcined to obtain an alumina carrier, and active metal is loaded on the obtained alumina carrier by using a conventional method. The preparation method of the flaky γ-polycrystalline alumina comprises the following steps: (1) mixing inorganic aluminum salt, low-carbon alcohol and / or water and low-carbon alkylene oxide uniformly to form a gel, and then aging the gel; (2) soaking the gel obtained in step (1) with low-carbon alcohol, and then drying and calcining; (3) immersing the material obtained in step (2) into ammonia water for closed hydrothermal treatment, solid-liquid separation, and drying to obtain flaky γ-polycrystalline alumina raw powder. The invention adjusts the pore structure of the carrier by adding flaky γ-polycrystalline alumina into the alumina carrier, but the preparation process of the flaky γ-polycrystalline alumina is relatively complex.

[0004] CN110467206A discloses a macroporous alumina carrier and a preparation method thereof. The preparation method of the macroporous alumina comprises the following contents: (1) preparing an aluminum sol; (2) mixing inorganic aluminum salt, polyethylene glycol, the aluminum sol obtained in step (1) and an organic compound containing an amide group with a low-carbon alcohol aqueous solution uniformly; (3) adding propylene oxide and / or pyridine into the mixture obtained in step (2) to mix uniformly to obtain a gel, aging to obtain an aged product; (4) soaking the aged product with a low-carbon alcohol aqueous solution, and then performing solid-liquid separation, drying and calcining the solid phase to obtain macroporous alumina. The preparation process of the alumina carrier is complicated and is not conducive to industrial production. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing an alumina support. This method is simple to prepare the alumina support, and the macroporous content in the alumina support is adjustable. This alumina support is suitable for preparing catalysts for heterogeneous catalytic reactions, and is particularly suitable for the field of heavy residue oil hydrotreating.

[0006] The present invention adopts the following technical solution:

[0007] A method for preparing an alumina support includes the following steps:

[0008] The first step is to calcine hydrated alumina to obtain γ-phase alumina powder;

[0009] The second step involves immersing the γ-phase alumina powder obtained in the first step into an organic alkali solution I for sealed preheating treatment. After treatment, the material undergoes liquid-solid separation.

[0010] The third step involves immersing the solid material separated in the second step into organic alkali solution II for sealed hydrothermal treatment. After treatment, the material undergoes liquid-solid separation and drying to obtain elliptical, plate-shaped pseudoboehmite F1.

[0011] The fourth step involves mixing and kneading the elliptical sheet-like pseudoboehmite F1 obtained in the third step with pseudoboehmite F2 to form a mold. The molded material is then dried and calcined to obtain an alumina carrier.

[0012] Furthermore, the hydrated alumina mentioned in the first step is boehmite, which can be prepared or purchased by existing methods, and more preferably boehmite prepared by the aluminum sulfate-sodium aluminate method. The calcination temperature is 450-650℃ and the calcination time is 4-8 hours.

[0013] Furthermore, the organic base solution I mentioned in the second step includes one of tetramethylammonium hydroxide, tetraethylaluminum hydroxide, and tetrapropylammonium hydroxide, preferably tetraethylammonium hydroxide, and the mass concentration of the organic base in the organic base solution I is 0.8%-2.0%.

[0014] Furthermore, the sealing preheating treatment in the second step is carried out in a sealed container, preferably a high-pressure reactor, with a preheating temperature of 80-120°C and a preheating time of 1-4 hours.

[0015] Furthermore, the organic base solution II described in the third step comprises one of tetramethylammonium hydroxide, tetraethylaluminum hydroxide, and tetrapropylammonium hydroxide, preferably tetraethylammonium hydroxide. Organic base solution II may be the same as or different from organic base solution I, but is preferably the same. The mass concentration of the organic base in organic base solution II is 3.5%-12.5%.

[0016] Further, the sealing hydrothermal treatment in the third step is carried out in a sealed container, preferably a high-pressure reactor, at a temperature of 140-180℃ for 4-10 hours, and the drying temperature is 100-160℃, and the drying time is 6-10 hours.

[0017] Further, the pseudo-boehmite F2 in the fourth step can be prepared by any method, such as acid precipitation, alkali precipitation, and alcohol aluminum hydrolysis, and preferably has a pore size of 10-20 nm, and more preferably has a pore content of 50% or more.

[0018] Further, the mass ratio of the elliptical flaky pseudo-boehmite F1 to the pseudo-boehmite F2 in the fourth step is 1:4-2:3.

[0019] Further, the kneading and molding in the fourth step is carried out by a conventional method, the drying temperature is 100-160℃, the drying time is 6-10 hours, the calcination temperature is 550-750℃, and the calcination time is 4-6 hours.

[0020] The present application has the following advantages:

[0021] 1. In the preparation of the alumina carrier, the pseudo-boehmite with an elliptical flaky morphology is selected as part of the raw material, and the elliptical flaky pseudo-boehmite accumulates to form a large number of large pore channels, so that the pore structure of the carrier can be flexibly adjusted by adjusting the amount of the elliptical flaky pseudo-boehmite, thereby meeting the needs of different reactions for the pore structure of the catalyst.

[0022] 2. The preparation process of the elliptical flaky pseudo-boehmite is simple, the raw materials are easy to obtain, the elliptical flaky pseudo-boehmite has a uniform morphology, and the channels formed by the cross-accumulation of the flaky particles are wide.

[0023] 3. The alumina carrier is prepared using two pseudo-boehmites with different morphologies as raw materials, which effectively adjusts the pore structure of the carrier and adjusts the surface chemical properties of the carrier, thereby improving the catalytic activity of the corresponding catalyst. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a scanning electron microscope image of the elliptical flaky pseudo-boehmite prepared in Example 1.

[0025] Figure 2 is a scanning electron microscope image of the cross-section of the alumina carrier prepared in Example 1.

[0026] Figure 3 is a scanning electron microscope image of the cross-section of the alumina carrier prepared in Comparative Example 4. DETAILED DESCRIPTION

[0027] 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.

[0028] Sample pore structure characterization: the pore structure of the sample was characterized by using a Micromeritics Trister 3000 nitrogen physical adsorption instrument.

[0029] Distribution rate of pores with a diameter of 100 nm or more: the pore distribution of the sample was characterized by using an American Mac AutoPore9500 full-automatic mercury porosimeter.

[0030] Sample microstructure characterization: the microstructure of the sample was characterized by using a Hitachi SU8220 scanning electron microscope (SEM).

[0031] Example 1

[0032] (1) A suitable amount of pseudo-boehmite prepared by the aluminum sulfate-sodium metaaluminate method was calcined at 500°C for 6 hours to obtain γ-phase alumina powder;

[0033] (2) A suitable amount of the γ-phase alumina powder of step (1) was weighed, a tetraethylammonium hydroxide solution with a concentration of 0.9wt% was added to completely immerse the γ-phase alumina powder, the mixture was stirred for 45 minutes, then the mixture was transferred into a high-pressure kettle for sealing and preheating treatment at 90°C for 3.5 hours, and after the treatment, the material was filtered to obtain a filter cake for standby;

[0034] (3) The filter cake obtained in step (2) was again loaded into the reaction liner of the high-pressure kettle, a tetraethylammonium hydroxide solution with a concentration of 6.5wt% was added to completely immerse the material, the mixture was stirred for 45 minutes, the high-pressure kettle was sealed and hydrothermally treated at 165°C for 6 hours, and after the treatment, the material was filtered, and the filter cake was dried at 140°C for 6 hours to prepare an ellipsoidal flaky pseudo-boehmite, and the scanning electron microscope image of the sample is shown in Figure 1 .

[0035] (4) 600 grams of pseudo-boehmite (10-20 nm pores accounting for 56.5% of the total pore volume) and 220 grams of the ellipsoidal flaky pseudo-boehmite prepared in step (3) were weighed, 3.5 grams of sesbania powder was added, the above materials were uniformly mixed, then a suitable amount of a peptizing agent was added and kneaded into a plastic body, and the strip-shaped carrier was dried at 140°C for 8 hours and calcined at 700°C for 6 hours to prepare the alumina carrier Z1 of the present application, and the properties of the carrier are shown in Table 1, and the scanning electron microscope image of the cross section of the carrier is shown in Figure 2 .

[0036] Example 2

[0037] The same as example 1, except that in step (2) the concentration of tetraethylammonium hydroxide is 1.3 wt%, the preheating treatment temperature is 100°C, and the treatment time is 2.5 hours. In step (3) the concentration of tetraethylammonium hydroxide is 8.5 wt%, the hydrothermal treatment temperature is 155°C, and the treatment time is 8.5 hours. In step (4) the amount of oval flaky pseudoboehmite added is 300 grams, and the alumina carrier Z2 of the present application is prepared. The properties of the carrier are shown in Table 1.

[0038] Example 3

[0039] The same as example 1, except that in step (2) the concentration of tetraethylammonium hydroxide is 1.6 wt%, the preheating treatment temperature is 80°C, and the treatment time is 4 hours. In step (3) the concentration of tetraethylammonium hydroxide is 10.5 wt%, the hydrothermal treatment temperature is 140°C, and the treatment time is 10 hours. In step (4) the amount of oval flaky pseudoboehmite added is 170 grams, and the alumina carrier Z3 of the present application is prepared. The properties of the carrier are shown in Table 1.

[0040] Example 4

[0041] The same as example 1, except that in step (2) tetraethylammonium hydroxide is replaced by tetrapropylammonium hydroxide, the solution concentration is 1.1 wt%, the preheating treatment temperature is 110°C, and the treatment time is 1.5 hours. In step (3) the concentration of tetraethylammonium hydroxide is 4.5 wt%, the hydrothermal treatment temperature is 175°C, and the treatment time is 4.5 hours. In step (4) the amount of oval flaky pseudoboehmite added is 400 grams, and the alumina carrier Z4 of the present application is prepared. The properties of the carrier are shown in Table 1.

[0042] Comparative Example 1

[0043] The same as example 1, except that in steps (2) and (3) the tetraethylammonium hydroxide solution is replaced by an aqueous ammonia solution of the same concentration, and the comparative alumina carrier Z5 is prepared. The properties of the carrier are shown in Table 1.

[0044] Comparative Example 2

[0045] The same as example 1, except that in steps (2) and (3) the tetraethylammonium hydroxide solution is replaced by an aqueous sodium hydroxide solution of the same concentration, and the comparative alumina carrier Z6 is prepared. The properties of the carrier are shown in Table 1.

[0046] Comparative Example 3

[0047] The same as example 1, except that in steps (2) and (3) the tetraethylammonium hydroxide solution is replaced by distilled water, and the comparative alumina carrier Z7 is prepared. The properties of the carrier are shown in Table 1.

[0048] Comparative Example 4

[0049] The same as example 1, except that step (1), step (2) and step (3) are not used, and directly using pseudo-boehmite (10-20 nm pore accounts for 56.5% of the total pore volume) as raw material, comparative alumina carrier Z8 is prepared, the properties of the carrier are shown in Table 1, and the cross-section scanning electron microscope image of the carrier is shown in Figure 3 .

[0050] Table 1: Properties of alumina carrier

[0051]

[0052] As shown in Table 1: Properties of alumina carrier, the alumina carrier prepared by using the pseudo-boehmite with elliptical flake shape as raw material by the method of the present application has higher content of pores larger than 100 nm compared with the alumina carrier of the comparative example.

[0053] As shown in Figure 1 and Figure 2 , the pseudo-boehmite with elliptical flake shape prepared by the method of the present application has uniform particle morphology, and a large number of macroporous structures are formed by the intersection of the flake particles. The macroporous channels formed by the intersection of the pseudo-boehmite with elliptical flake shape do not collapse during the shaping of the carrier, and are well maintained. Due to the addition of the pseudo-boehmite with elliptical flake shape in the carrier, the accumulation mode of the particles in the carrier is effectively adjusted, so that the carrier has higher macropore content.

Claims

1. A method for preparing an alumina support, characterized in that: Includes the following steps: The first step is to calcine pseudoboehmite to obtain γ-phase alumina powder; The second step involves immersing the γ-phase alumina powder obtained in the first step into an organic alkali solution I for sealed preheating treatment. This sealed preheating treatment is carried out in a sealed container at a temperature of 80-120°C for 1-4 hours. After treatment, the material undergoes liquid-solid separation. The organic alkali solution I comprises tetramethylammonium hydroxide or tetrapropylammonium hydroxide, and the mass concentration of the organic alkali in the organic alkali solution I is 0.8%-2.0%. The third step involves immersing the solid material separated in the second step again in an organic alkali solution II for sealed hydrothermal treatment. This sealed hydrothermal treatment is conducted in a sealed container at a temperature of 140-180℃ for 4-10 hours. After treatment, the material undergoes liquid-solid separation and drying to obtain elliptical, sheet-like pseudoboehmite F1. The organic alkali solution II comprises tetramethylammonium hydroxide or tetrapropylammonium hydroxide, and the mass concentration of the organic alkali in the organic alkali solution II is 3.5%-12.5%. The fourth step involves mixing and kneading the elliptical sheet-like pseudoboehmite F1 and pseudoboehmite F2 obtained in the third step into a molded shape. The molded material is then dried and calcined to obtain an alumina carrier. The pseudoboehmite F2 has a pore size of 10-20 nm, and the content of 10-20 nm pores accounts for more than 50% of the total pore volume. The mass ratio of the elliptical, plate-shaped pseudoboehmite F1 to pseudoboehmite F2 is 1:4-2:

3.

2. The method for preparing an alumina carrier according to claim 1, characterized in that: In the first step, the roasting temperature is 450-650℃ and the roasting time is 4-8 hours.

3. The method for preparing an alumina carrier according to claim 1, characterized in that: In the third step, the drying temperature is 100-160℃ and the drying time is 6-10 hours.

4. The method for preparing an alumina carrier according to claim 1, characterized in that: In the fourth step, the pseudoboehmite F2 is prepared by acid precipitation, alkaline precipitation or aluminum alkoxide hydrolysis.

5. The method for preparing an alumina carrier according to claim 1, characterized in that: In the fourth step, the drying temperature is 100-160℃ and the drying time is 6-10 hours; the calcination temperature is 550-750℃ and the calcination time is 4-6 hours.

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