Aluminum oxide with high specific surface area and preparation method thereof

Abstract

The invention belongs to the technical field of inorganic material preparation, and particularly relates to aluminum oxide with high specific surface area and a preparation method thereof. The preparation method of the aluminum oxide comprises the following steps: (1) preparing an aluminum salt solution, and adding long-chain alkyl quaternary ammonium salt into the aluminum salt solution; (2) preparing a meta-aluminate solution, and adding polyethylene glycol into the meta-aluminate solution; (3) dropwise adding the solution obtained in the step (2) into the solution obtained in the step (1) to obtain a final solution, and adjusting the pH of the final solution to be alkaline; and (4) carrying out heating reaction, and carrying out post-treatment to obtain the high-specific-surface-area aluminum oxide. The long-chain alkyl quaternary ammonium salt is adopted as a main template agent and a modifier, and a small amount of polyethylene glycol is added, so that the technical problems of low specific surface area and small pore diameter of an alumina material prepared from the long-chain alkyl quaternary ammonium salt are solved, an alumina product with high specific surface area is prepared, and the preparation method has the advantages of low energy consumption and good economical efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic material preparation, and particularly relates to a high specific surface area alumina and a preparation method thereof. Background Art

[0002] The carrier is an important component of the catalyst. It can increase the surface area, improve the heat resistance and mechanical strength, and sometimes can also act as a cocatalyst and a promoter. Common carrier materials include alumina, zirconia, titania, silica, molecular sieve, and composite oxides, etc. There are also many methods for preparing the carrier, such as the sol-gel method, the co-precipitation method, the mechanical method, etc.

[0003] Due to its advantages such as good mechanical strength, high thermal stability and chemical stability, adjustable surface acidity and basicity, and various different crystal phase structures, alumina has become the most widely used catalyst or catalyst carrier in the chemical industry. With the in-depth research work, it is recognized that for supported catalysts, the pore structure (specific surface area, pore volume, etc.) of the carrier not only has an important influence on the distribution of the supported active components, but also is closely related to the activity, selectivity and lifetime of the catalyst. For an alumina carrier with excellent structure, its large specific surface area can load more active components, thereby improving the reaction activity. The large pore volume will provide a space for accommodating substances such as coke and metal, and the large pore diameter means that the pore channels are not easily blocked, and the catalyst is not easily deactivated.

[0004] Among industrial catalyst carriers, alumina is the most widely used carrier. Alumina is cheap and can obtain the required crystal phase, surface area and pore size distribution, etc. by changing the preparation conditions. Alumina as a catalyst carrier has the characteristics of high temperature resistance and oxidation resistance, and is widely used as a carrier for catalysts such as automotive exhaust catalysts, petroleum refining catalysts, hydrogenation and hydrodesulfurization catalysts at home and abroad. The pores of alumina can generally be divided into three types: pores between fine particles, pores between primary particles, and pores formed during the shaping of the alumina product. The voids between particles are the source of the pores of alumina, and the size and shape of the pores completely depend on the particle size, shape and packing mode. With the in-depth application and development of alumina, the catalysts prepared with high specific surface area alumina carriers have higher activity, selectivity and conversion rate than those prepared with low specific surface area carriers. Therefore, developing high specific surface area alumina carriers is a future development direction.

[0005] The Chinese patent application with the publication number CN117142503A provides a preparation method of composite activated alumina powder, which in-situ prepares aluminum hydroxide colloid by using a specific template agent and obtains composite activated alumina powder with a better pore size distribution through further calcination. The Chinese patent application with the publication number CN115445598A provides a preparation method of a modified α-alumina carrier, which prepares a formed high specific surface area alumina carrier through processes such as kneading, extrusion molding, drying, and calcination. When using the above modified alumina carrier to prepare a methane steam reforming catalyst, compared with commercial catalysts, the catalyst prepared by the modified alumina carrier has higher methane conversion activity and better activity stability. A series of patents applied by Shandong Gongquan Chemical Co., Ltd. (CN118045581A, CN118788318A, CN118807722A, CN118929711A) also studied the effects of different surfactants or template agents on the performance of alumina catalyst carriers. Although this series of patents improved the specific surface area of alumina to a certain extent and improved the carrier performance, they all used various non-ionic surfactants as modifiers to prepare alumina carriers, which not only had complex processes and high costs, but also required complex washing processes, needed a large amount of washing liquid to wash alumina intermediates or products, had high energy consumption, and limited improvement in product performance. Although cationic surfactants (such as various quaternary ammonium salts) have also been studied as template agents in the preparation process of alumina, there are technical problems such as small pore size and relatively low specific surface area when using simple quaternary ammonium salts as template agents. Summary of the Invention

[0006] The purpose of the present invention is to provide a high specific surface area alumina and its preparation method. By using long-chain alkyl quaternary ammonium salts as the main template agent and modifier and adding a small amount of polyethylene glycol, it solves the technical problems of low specific surface area and small pore size of alumina materials prepared by long-chain alkyl quaternary ammonium salts, prepares an alumina product with a high specific surface area, and has the advantages of low energy consumption and good economy.

[0007] To achieve the above purpose, the present invention provides the following technical solutions: A preparation method of high specific surface area alumina, comprising the following steps: (1) Prepare an aluminum salt solution, add long-chain alkyl quaternary ammonium salt thereto, and disperse evenly by ultrasonic; the mass ratio of long-chain alkyl quaternary ammonium salt to aluminum salt is (0.04 - 0.2):1; (2) Prepare a meta-aluminate solution, add polyethylene glycol thereto, and stir to disperse evenly; the number average molecular weight of polyethylene glycol is 200 - 2000; the mass ratio of polyethylene glycol to long-chain alkyl quaternary ammonium salt is (0.1 - 0.4):1; To promote the dissolution of polyethylene glycol, appropriate heating can be carried out to accelerate the dissolution rate.

[0008] By separately adding long-chain alkyl quaternary ammonium salts and polyethylene glycol into aluminum salt solutions and meta-aluminate solutions, the dispersion of grains can be better promoted, and the occurrence of agglomeration can be prevented. Both the long-chain alkyl quaternary ammonium salts and the aluminum ions in the aluminum salt solutions carry positive charges. Pre-adding the long-chain alkyl quaternary ammonium salts into the aluminum salt solutions can better promote the dispersion of micelles. And adding the non-ionic surfactant (polyethylene glycol) into the meta-aluminate solutions can not only play the role of the polyethylene glycol template agent, but also make full use of the dispersion function of polyethylene glycol to promote the dispersion of grains.

[0009] If the long-chain alkyl quaternary ammonium salts are added into the meta-aluminate solutions, or the polyethylene glycol is added into the aluminum salt solutions, not only can the polyethylene glycol not play its role, but also it is easy to cause the positively charged long-chain alkyl quaternary ammonium salts to have a strong electrostatic interaction with the meta-aluminate in advance, which is not conducive to the dispersion of grains and affects the improvement of the specific surface area of the alumina products.

[0010] Polyethylene glycol with an appropriate molecular weight, while ensuring the templating effect, not only takes into account good solubility and dispersibility, but also can avoid the interaction with long-chain quaternary ammonium salts due to too high a molecular weight, which affects the dispersion of grains or precipitates. Further, the molecular weight of polyethylene glycol can be any value between 300 - 1800, or 400 - 1500, or 600 - 1400, or 800 - 1200.

[0011] (3) Drop the solution obtained in step (2) into the solution obtained in step (1) to obtain the final solution, and adjust the pH of the final solution to be alkaline; Among them, the specific process of step (3) is: first heat the solution obtained in step (1) to 50 - 70 °C, and then dropwise add the solution obtained in step (2) to it while stirring; the stirring rate is 200 - 300 rpm; the dropping rate is 5 - 15 mL / min; (4) Heat and react, and obtain high specific surface area alumina through post-treatment.

[0012] According to the different surface active template agents used, the common synthesis methods of alumina can be divided into: cationic template method, anionic template method, non-ionic template method. Among them, non-ionic surfactants (block copolymers, etc.) have the advantages of no ionization phenomenon in water, good compatibility with other solutes, not being affected by the solution pH, and high operation stability. They are the most common templates for preparing high specific surface area alumina at present. However, due to the generally large molecular weight of polymers, poor solubility, and relatively high prices of many types of non-ionic surfactants, they are not suitable for industrial production. Therefore, the present invention selects long-chain alkyl quaternary ammonium salts as the cationic template agent. The alumina materials synthesized with long-chain alkyl quaternary ammonium salts as the template agent have the advantages of regular mesopores, high order, and easy control of pore size distribution and pore size.

[0013] However, the pore size formed by using only long-chain alkyl quaternary ammonium salts as template agents is relatively small, and the specific surface area is relatively low. In actual production tests, the specific surface area of alumina prepared by using only long-chain alkyl quaternary ammonium salts as template agents in the aluminum salt-sodium aluminate reaction system can only reach 200 m 2 / g, and the pore volume and pore size are relatively low. Therefore, on the basis of the long-chain alkyl quaternary ammonium salt template agent, a small amount of polyethylene glycol non-ionic surfactant is added in the present invention to solve the problems existing in the long-chain alkyl quaternary ammonium salt as a cationic template agent. The pore size synthesized by the polyethylene glycol non-ionic surfactant is usually relatively large, the specific surface area is relatively high, and the pore size can be adjusted by changing the chain length of the molecule.

[0014] In a specific embodiment of the present invention, in step (1), the aluminum salt is at least one of aluminum nitrate, aluminum chloride, and aluminum sulfate; the concentration of the aluminum salt solution is 10-40 g / L.

[0015] In a specific embodiment of the present invention, in step (1), the ultrasonic power is 100-300 W; the long-chain alkyl quaternary ammonium salt is at least one of dodecyl trimethyl ammonium bromide, dodecyl trimethyl ammonium chloride, cetyl trimethyl ammonium bromide, cetyl trimethyl ammonium chloride, octadecyl trimethyl ammonium bromide, and octadecyl trimethyl ammonium chloride. By combining the long-chain alkyl quaternary ammonium salt with polyethylene glycol, the prepared alumina material not only has a large specific surface area, but also has a large pore size and a regular pore structure, which can allow relatively large molecules and groups to pass through smoothly and significantly reduce the internal diffusion resistance during the reaction process, and is an ideal catalyst carrier. The mass ratio of the long-chain alkyl quaternary ammonium salt to the aluminum salt is (0.04-0.2):1; specifically, the mass ratio of the long-chain alkyl quaternary ammonium salt to the aluminum salt can be specific values such as 0.06:1, 0.08:1, 0.1:1, 0.12:1, 0.15:1, 0.18:1, etc. By controlling the dosage of the long-chain alkyl quaternary ammonium salt within a suitable range, smaller crystal grains can be formed, and the phenomenon of pore collapse during the calcination process after the template agent is removed can be avoided.

[0016] In a specific embodiment of the present invention, in step (2), the sodium aluminate is at least one of sodium aluminate or potassium aluminate; the concentration of the sodium aluminate solution is 5-25 g / L.

[0017] In a specific embodiment of the present invention, in step (2), the mass ratio of the sodium aluminate to the aluminum salt in step (1) is (0.5-1):1; the stirring rate in step (2) is 300-600 rpm.

[0018] In a specific embodiment of the present invention, the pH value in step (3) is 7.5 - 10. The method of adjusting the pH is not particularly limited and can be adjusted by adding an acid or a base. Specifically, an acid substance such as hydrochloric acid, sulfuric acid or nitric acid, or an alkaline substance such as sodium hydroxide, potassium hydroxide or ammonia water is used for adjustment.

[0019] In a specific embodiment of the present invention, in step (4), the heating reaction temperature is 75 - 95 °C and the reaction time is 1 - 3 h. The reaction device is not particularly limited and can be carried out in a reaction kettle.

[0020] In a specific embodiment of the present invention, the post-treatment in step (4) is a process of filtration, washing, drying and calcination. The long-chain alkyl quaternary ammonium salt combined with polyethylene glycol as a composite template agent can participate in the precipitation or hydrolysis of components during the synthesis process, which is beneficial to the synthesis of porous materials with a large specific surface area.

[0021] In a specific embodiment of the present invention, drying in step (4) is carried out by oven drying; the calcination temperature is 550 - 650 °C and the calcination time is 5 - 6 h.

[0022] On the other hand, the present invention also provides a high specific surface area alumina obtained by the above preparation method, which has the characteristics of large pore volume and large surface area, and the preparation process is simple and can be used as an industrial catalyst carrier.

[0023] Beneficial effects: The present invention uses a long-chain alkyl quaternary ammonium salt as a template agent, and the synthesized alumina material has the advantages of regular mesopores, high order, easy control of pore size distribution and pore size. The pore size synthesized by the polyethylene glycol non-ionic surfactant is usually larger, and the pore size can be adjusted by changing the molecular chain length.

[0024] At the same time, adding two kinds of cationic and non-ionic surfactants, namely long-chain alkyl quaternary ammonium salt and polyethylene glycol, can give full play to the advantages of both: the long-chain alkyl quaternary ammonium salt cationic surfactant is easy to combine with the aluminum source during hydrolysis, and the polyethylene glycol non-ionic surfactant helps the formation of pores during precipitation and drying, so as to prepare an alumina product with a high surface area and pore volume, and solve the technical problem of low specific surface area caused by simply using long-chain alkyl quaternary ammonium salt. Specific embodiments

[0025] The examples given are for better illustration of the present invention, but the content of the present invention is not limited only to the examples given. Therefore, those skilled in the art who make non-essential improvements and adjustments to the implementation scheme according to the above invention content still fall within the protection scope of the present invention.

[0026] The terms used in this document are only for describing specific embodiments and are not intended to limit this disclosure. Unless there is an obviously different meaning in the context, the singular forms of expressions include the plural forms. As used herein, it should be understood that terms such as "including", "having", "containing" are intended to indicate the existence of features, numbers, operations, components, parts, elements, materials or combinations. Terms of the present invention are disclosed in the specification, and it is not intended to exclude the possibility that one or more other features, numbers, operations, components, parts, elements, materials or combinations may exist or can be added.

[0027] Example 1 A method for preparing high specific surface area alumina, comprising the following steps: (1) Prepare an aluminum salt solution, add a long-chain alkyl quaternary ammonium salt thereto, and disperse it evenly by ultrasonic wave; the mass ratio of the long-chain alkyl quaternary ammonium salt to the aluminum salt is 0.08:1; the aluminum salt is aluminum nitrate; the concentration of the aluminum salt solution is 16 g / L; the ultrasonic power is 200 W; the long-chain alkyl quaternary ammonium salt is cetyltrimethylammonium bromide; (2) Prepare a meta-aluminate solution, add polyethylene glycol thereto, and disperse it evenly by stirring; the number-average molecular weight of the polyethylene glycol is 800; the mass ratio of the polyethylene glycol to the long-chain alkyl quaternary ammonium salt is 0.1:1; the meta-aluminate is sodium meta-aluminate; the concentration of the meta-aluminate solution is 11 g / L; the stirring rate is 400 rpm; In the above step (2), the mass ratio of the meta-aluminate to the aluminum salt in step (1) is 0.6:1; (3) First heat the solution obtained in step (1) to 50 °C, then dropwise add the solution obtained in step (2) while stirring to obtain a final solution, and adjust the pH value of the final solution to 8; the stirring rate is 250 rpm; the dropping rate is 7 mL / min; (4) Heat and react, and obtain high specific surface area alumina through post-treatment; the heating reaction temperature is 75 °C, and the reaction time is 3 h; the post-treatment is a process of filtration, washing, drying, and calcination; drying is carried out by oven drying; the calcination temperature is 550 °C, and the calcination time is 6 h.

[0028] Example 2 A method for preparing high specific surface area alumina, comprising the following steps: (1) Prepare an aluminum salt solution, add a long-chain alkyl quaternary ammonium salt thereto, and disperse it evenly by ultrasonic wave; the mass ratio of the long-chain alkyl quaternary ammonium salt to the aluminum salt is 0.15:1; the aluminum salt is aluminum nitrate; the concentration of the aluminum salt solution is 20 g / L; the ultrasonic power is 200 W; the long-chain alkyl quaternary ammonium salt is cetyltrimethylammonium bromide; (2) Prepare a meta-aluminate solution, add polyethylene glycol thereto, and stir to disperse evenly; the number-average molecular weight of polyethylene glycol is 1200; the mass ratio of polyethylene glycol to long-chain alkyl quaternary ammonium salt is 0.4:1; the meta-aluminate is sodium meta-aluminate; the concentration of the meta-aluminate solution is 14 g / L; the stirring rate is 400 rpm; In the above step (2), the mass ratio of the meta-aluminate to the aluminate in step (1) is 0.8:1; (3) First, heat the solution obtained in step (1) to 70 °C, then add dropwise the solution obtained in step (2) while stirring to obtain a final solution, and adjust the pH value of the final solution to 10; the stirring rate is 250 rpm; the dropping rate is 12 mL / min; (4) Heat for reaction, and obtain high specific surface area alumina through post-treatment; the heating reaction temperature is 95 °C, the reaction time is 1 h; the post-treatment is a process of filtration, washing, drying, and calcination; drying is carried out by oven drying; the calcination temperature is 650 °C, and the calcination time is 5 h.

[0029] Example 3 A method for preparing high specific surface area alumina, comprising the following steps: (1) Prepare an aluminate solution, add a long-chain alkyl quaternary ammonium salt thereto, and ultrasonically disperse evenly; the mass ratio of the long-chain alkyl quaternary ammonium salt to the aluminate is 0.04:1; the aluminate is aluminum nitrate; the concentration of the aluminate solution is 18 g / L; the ultrasonic power is 200 W; the long-chain alkyl quaternary ammonium salt is cetyltrimethylammonium bromide; (2) Prepare a meta-aluminate solution, add polyethylene glycol thereto, and stir to disperse evenly; the number-average molecular weight of polyethylene glycol is 1200; the mass ratio of polyethylene glycol to long-chain alkyl quaternary ammonium salt is 0.2:1; the meta-aluminate is sodium meta-aluminate; the concentration of the meta-aluminate solution is 12 g / L; the stirring rate is 400 rpm; In the above step (2), the mass ratio of the meta-aluminate to the aluminate in step (1) is 0.7:1; (3) First, heat the solution obtained in step (1) to 61 °C, then add dropwise the solution obtained in step (2) while stirring to obtain a final solution, and adjust the pH value of the final solution to 9; the stirring rate is 250 rpm; the dropping rate is 9 mL / min; (4) Heat for reaction, and obtain high specific surface area alumina through post-treatment; the heating reaction temperature is 84 °C, the reaction time is 2 h; the post-treatment is a process of filtration, washing, drying, and calcination; drying is carried out by oven drying; the calcination temperature is 600 °C, and the calcination time is 5.5 h.

[0030] Example 4 A method for preparing high specific surface area alumina, comprising the following steps: (1) Prepare an aluminum salt solution, add a long-chain alkyl quaternary ammonium salt thereto, and disperse evenly by ultrasonic treatment; the mass ratio of the long-chain alkyl quaternary ammonium salt to the aluminum salt is 0.15:1; the aluminum salt is aluminum nitrate; the concentration of the aluminum salt solution is 17 g / L; the ultrasonic power is 200 W; the long-chain alkyl quaternary ammonium salt is cetyltrimethylammonium bromide; (2) Prepare a meta-aluminate solution, add polyethylene glycol thereto, and disperse evenly by stirring; the number-average molecular weight of the polyethylene glycol is 1500; the mass ratio of the polyethylene glycol to the long-chain alkyl quaternary ammonium salt is 0.1:1; the meta-aluminate is sodium meta-aluminate; the concentration of the meta-aluminate solution is 14 g / L; the stirring rate is 400 rpm; In the above step (2), the mass ratio of the meta-aluminate to the aluminum salt in step (1) is 0.6:1; (3) First, heat the solution obtained in step (1) to 70 °C, then dropwise add the solution obtained in step (2) while stirring to obtain a final solution, and adjust the pH value of the final solution to 10; the stirring rate is 250 rpm; the dropping rate is 7 mL / min; (4) Carry out a heating reaction, and obtain high specific surface area alumina after post-treatment; the heating reaction temperature is 75 °C, and the reaction time is 1 h; the post-treatment is a process of filtration, washing, drying, and calcination; drying is carried out by oven drying; the calcination temperature is 650 °C, and the calcination time is 6 h.

[0031] Example 5 A method for preparing high specific surface area alumina, comprising the following steps: (1) Prepare an aluminum salt solution, add a long-chain alkyl quaternary ammonium salt thereto, and disperse evenly by ultrasonic treatment; the mass ratio of the long-chain alkyl quaternary ammonium salt to the aluminum salt is 0.2:1; the aluminum salt is aluminum nitrate; the concentration of the aluminum salt solution is 18 g / L; the ultrasonic power is 200 W; the long-chain alkyl quaternary ammonium salt is cetyltrimethylammonium bromide; (2) Prepare a meta-aluminate solution, add polyethylene glycol thereto, and disperse evenly by stirring; the number-average molecular weight of the polyethylene glycol is 1200; the mass ratio of the polyethylene glycol to the long-chain alkyl quaternary ammonium salt is 0.2:1; the meta-aluminate is sodium meta-aluminate; the concentration of the meta-aluminate solution is 12 g / L; the stirring rate is 400 rpm; In the above step (2), the mass ratio of the meta-aluminate to the aluminum salt in step (1) is 0.7:1; (3) First, heat the solution obtained in step (1) to 61 °C, then dropwise add the solution obtained in step (2) while stirring to obtain a final solution, and adjust the pH value of the final solution to 9; the stirring rate is 250 rpm; the dropping rate is 9 mL / min; (4) Heat the reaction mixture and obtain high specific surface area alumina after post-treatment; the heating reaction temperature is 84 °C, and the reaction time is 2 h; the post-treatment is a process of filtration, washing, drying, and calcination; drying is carried out using an oven; the calcination temperature is 600 °C, and the calcination time is 5.5 h.

[0032] Example 6 A method for preparing high specific surface area alumina, comprising the following steps: (1) Prepare an aluminum salt solution, add a long-chain alkyl quaternary ammonium salt thereto, and disperse it evenly by ultrasonic treatment; the mass ratio of the long-chain alkyl quaternary ammonium salt to the aluminum salt is 0.09:1; the aluminum salt is aluminum nitrate; the concentration of the aluminum salt solution is 17 g / L; the ultrasonic power is 200 W; the long-chain alkyl quaternary ammonium salt is cetyltrimethylammonium bromide; (2) Prepare a meta-aluminate solution, add polyethylene glycol thereto, and disperse it evenly by stirring; the number average molecular weight of the polyethylene glycol is 1000; the mass ratio of the polyethylene glycol to the long-chain alkyl quaternary ammonium salt is 0.2:1; the meta-aluminate is sodium meta-aluminate; the concentration of the meta-aluminate solution is 12 g / L; the stirring rate is 400 rpm; In the above step (2), the mass ratio of the meta-aluminate to the aluminum salt in step (1) is 0.65:1; (3) First, heat the solution obtained in step (1) to 56 °C, then dropwise add the solution obtained in step (2) while stirring to obtain a final solution, and adjust the pH value of the final solution to 8; the stirring rate is 250 rpm; the dropping rate is 8 mL / min; (4) Heat the reaction mixture and obtain high specific surface area alumina after post-treatment; the heating reaction temperature is 78 °C, and the reaction time is 2.4 h; the post-treatment is a process of filtration, washing, drying, and calcination; drying is carried out using an oven; the calcination temperature is 580 °C, and the calcination time is 5.7 h.

[0033] Example 7 A method for preparing high specific surface area alumina, comprising the following steps: (1) Prepare an aluminum salt solution, add a long-chain alkyl quaternary ammonium salt thereto, and disperse it evenly by ultrasonic treatment; the mass ratio of the long-chain alkyl quaternary ammonium salt to the aluminum salt is 0.12:1; the aluminum salt is aluminum nitrate; the concentration of the aluminum salt solution is 18 g / L; the ultrasonic power is 200 W; the long-chain alkyl quaternary ammonium salt is cetyltrimethylammonium bromide; (2) Prepare a meta-aluminate solution, add polyethylene glycol thereto, and disperse it evenly by stirring; the number average molecular weight of the polyethylene glycol is 200; the mass ratio of the polyethylene glycol to the long-chain alkyl quaternary ammonium salt is 0.2:1; the meta-aluminate is sodium meta-aluminate; the concentration of the meta-aluminate solution is 12 g / L; the stirring rate is 400 rpm; In the above step (2), the mass ratio of the meta-aluminate to the aluminum salt in step (1) is 0.7:1; (3) First, heat the solution obtained in step (1) to 61 °C, then dropwise add the solution obtained in step (2) while stirring to obtain the final solution, and adjust the pH value of the final solution to 9; the stirring rate is 250 rpm; the dropping rate is 9 mL / min; (4) Heat the reaction and obtain high specific surface area alumina after post-treatment; the heating reaction temperature is 84 °C, and the reaction time is 2 h; the post-treatment is a process of filtration, washing, drying, and calcination; drying is carried out using an oven; the calcination temperature is 600 °C, and the calcination time is 5.5 h. (5) (6)

[0034] Example 8 (7) A preparation method of high specific surface area alumina, comprising the following steps: (8) (1) Prepare an aluminum salt solution, and add a long-chain alkyl quaternary ammonium salt thereto, and ultrasonically disperse evenly; the mass ratio of the long-chain alkyl quaternary ammonium salt to the aluminum salt is 0.14:1; the aluminum salt is aluminum nitrate; the concentration of the aluminum salt solution is 19 g / L; the ultrasonic power is 200 W; the long-chain alkyl quaternary ammonium salt is cetyltrimethylammonium bromide; (9) (2) Prepare a meta-aluminate solution, and add polyethylene glycol thereto, and stir and disperse evenly; the number average molecular weight of the polyethylene glycol is 1500; the mass ratio of the polyethylene glycol to the long-chain alkyl quaternary ammonium salt is 0.3:1; the meta-aluminate is sodium meta-aluminate; the concentration of the meta-aluminate solution is 12 g / L; the stirring rate is 400 rpm; (10) In the above step (2), the mass ratio of the meta-aluminate to the aluminum salt in step (1) is 0.75:1; (11) (3) First, heat the solution obtained in step (1) to 66 °C, then dropwise add the solution obtained in step (2) while stirring to obtain the final solution, and adjust the pH value of the final solution to 9; the stirring rate is 250 rpm; the dropping rate is 11 mL / min; (12) (4) Heat the reaction and obtain high specific surface area alumina after post-treatment; the heating reaction temperature is 90 °C, and the reaction time is 1.8 h; the post-treatment is a process of filtration, washing, drying, and calcination; drying is carried out using an oven; the calcination temperature is 620 °C, and the calcination time is 5.2 h. (13) (14)

[0035] Example 9 (15) A preparation method of high specific surface area alumina, comprising the following steps: (16) (1) Prepare an aluminum salt solution, and add a long-chain alkyl quaternary ammonium salt thereto, and ultrasonically disperse evenly; the mass ratio of the long-chain alkyl quaternary ammonium salt to the aluminum salt is 0.12:1; the aluminum salt is aluminum nitrate; the concentration of the aluminum salt solution is 18 g / L; the ultrasonic power is 200 W; the long-chain alkyl quaternary ammonium salt is cetyltrimethylammonium bromide; (17) (2) Prepare a meta-aluminate solution, add polyethylene glycol thereto, and stir to disperse evenly; the number-average molecular weight of the polyethylene glycol is 2000; the mass ratio of the polyethylene glycol to the long-chain alkyl quaternary ammonium salt is 0.2:1; the meta-aluminate is sodium meta-aluminate; the concentration of the meta-aluminate solution is 12 g / L; the stirring rate is 400 rpm; In the above step (2), the mass ratio of the meta-aluminate to the aluminate in step (1) is 0.7:1; (3) First heat the solution obtained in step (1) to 61 °C, then dropwise add the solution obtained in step (2) while stirring to obtain a final solution, and adjust the pH value of the final solution to 9; the stirring rate is 250 rpm; the dropping rate is 9 mL / min; (4) Carry out a heating reaction, and obtain high specific surface area alumina through post-treatment; the heating reaction temperature is 84 °C, and the reaction time is 2 h; the post-treatment is a process of filtration, washing, drying, and calcination; drying is carried out by oven drying; the calcination temperature is 600 °C, and the calcination time is 5.5 h.

[0036] Example 10 A method for preparing high specific surface area alumina, comprising the following steps: (1) Prepare an aluminate solution, add a long-chain alkyl quaternary ammonium salt thereto, and ultrasonically disperse evenly; the mass ratio of the long-chain alkyl quaternary ammonium salt to the aluminate is 0.13:1; the aluminate is aluminum nitrate; the concentration of the aluminate solution is 18 g / L; the ultrasonic power is 200 W; the long-chain alkyl quaternary ammonium salt is cetyltrimethylammonium bromide; (2) Prepare a meta-aluminate solution, add polyethylene glycol thereto, and stir to disperse evenly; the number-average molecular weight of the polyethylene glycol is 800; the mass ratio of the polyethylene glycol to the long-chain alkyl quaternary ammonium salt is 0.25:1; the meta-aluminate is sodium meta-aluminate; the concentration of the meta-aluminate solution is 12.5 g / L; the stirring rate is 400 rpm; In the above step (2), the mass ratio of the meta-aluminate to the aluminate in step (1) is 0.72:1; (3) First heat the solution obtained in step (1) to 64 °C, then dropwise add the solution obtained in step (2) while stirring to obtain a final solution, and adjust the pH value of the final solution to 8.5; the stirring rate is 250 rpm; the dropping rate is 8 mL / min; (4) Carry out a heating reaction, and obtain high specific surface area alumina through post-treatment; the heating reaction temperature is 87 °C, and the reaction time is 1.4 h; the post-treatment is a process of filtration, washing, drying, and calcination; drying is carried out by oven drying; the calcination temperature is 580 °C, and the calcination time is 5.8 h.

[0037] Example 11 A method for preparing high specific surface area alumina, comprising the following steps: (1) Prepare an aluminum salt solution, add a long-chain alkyl quaternary ammonium salt thereto, and disperse evenly by ultrasonic treatment; the mass ratio of the long-chain alkyl quaternary ammonium salt to the aluminum salt is 0.12:1; the aluminum salt is aluminum nitrate; the concentration of the aluminum salt solution is 18 g / L; the ultrasonic power is 200 W; the long-chain alkyl quaternary ammonium salt is cetyltrimethylammonium bromide; (2) Prepare a meta-aluminate solution, add polyethylene glycol thereto, and disperse evenly by stirring; the number-average molecular weight of the polyethylene glycol is 1200; the mass ratio of the polyethylene glycol to the long-chain alkyl quaternary ammonium salt is 0.2:1; the meta-aluminate is sodium meta-aluminate; the concentration of the meta-aluminate solution is 12 g / L; the stirring rate is 400 rpm; In the above step (2), the mass ratio of the meta-aluminate to the aluminum salt in step (1) is 0.7:1; (3) First, heat the solution obtained in step (1) to 61 °C, then dropwise add the solution obtained in step (2) while stirring to obtain a final solution, and adjust the pH value of the final solution to 9; the stirring rate is 250 rpm; the dropping rate is 9 mL / min; (4) Carry out a heating reaction, and obtain high specific surface area alumina after post-treatment; the heating reaction temperature is 84 °C, and the reaction time is 2 h; the post-treatment is a process of filtration, washing, drying, and calcination; drying is carried out by oven drying; the calcination temperature is 600 °C, and the calcination time is 5.5 h.

[0038] Comparative Example 1 A method for preparing high specific surface area alumina, comprising the following steps: (1) Prepare an aluminum salt solution, add polyethylene glycol thereto, and disperse evenly by ultrasonic treatment; the number-average molecular weight of the polyethylene glycol is 1200; the mass ratio of the polyethylene glycol to the long-chain alkyl quaternary ammonium salt is 0.2:1; the aluminum salt is aluminum nitrate; the concentration of the aluminum salt solution is 18 g / L; the ultrasonic power is 200 W; (2) Prepare a meta-aluminate solution, add a long-chain alkyl quaternary ammonium salt thereto, and disperse evenly by stirring; the mass ratio of the long-chain alkyl quaternary ammonium salt to the aluminum salt is 0.12:1; the long-chain alkyl quaternary ammonium salt is cetyltrimethylammonium bromide; the meta-aluminate is sodium meta-aluminate; the concentration of the meta-aluminate solution is 12 g / L; the stirring rate is 400 rpm; In the above step (2), the mass ratio of the meta-aluminate to the aluminum salt in step (1) is 0.7:1; (3) First, heat the solution obtained in step (1) to 61 °C, then dropwise add the solution obtained in step (2) while stirring to obtain a final solution, and adjust the pH value of the final solution to 9; the stirring rate is 250 rpm; the dropping rate is 9 mL / min; (4) Heat the reaction mixture and obtain high specific surface area alumina after post-treatment. The heating reaction temperature is 84 °C and the reaction time is 2 h. The post-treatment process includes filtration, washing, drying, and calcination. Oven drying is used for drying. The calcination temperature is 600 °C and the calcination time is 5.5 h.

[0039] Comparative Example 2 A method for preparing high specific surface area alumina, comprising the following steps: (1) Prepare an aluminum salt solution and add a long-chain alkyl quaternary ammonium salt thereto, followed by ultrasonic dispersion until homogeneous. The mass ratio of the long-chain alkyl quaternary ammonium salt to the aluminum salt is 0.12:1. The aluminum salt is aluminum nitrate. The concentration of the aluminum salt solution is 18 g / L. The ultrasonic power is 200 W. The long-chain alkyl quaternary ammonium salt is cetyltrimethylammonium bromide; (2) Prepare a meta-aluminate solution and add polyethylene glycol thereto, followed by stirring dispersion until homogeneous. The number-average molecular weight of the polyethylene glycol is 1200. The mass ratio of the polyethylene glycol to the long-chain alkyl quaternary ammonium salt is 1:1. The meta-aluminate is sodium meta-aluminate. The concentration of the meta-aluminate solution is 12 g / L. The stirring rate is 400 rpm; In the above step (2), the mass ratio of the meta-aluminate to the aluminum salt in step (1) is 0.7:1; (3) First, heat the solution obtained in step (1) to 61 °C, and then add dropwise the solution obtained in step (2) while stirring to obtain a final solution, and adjust the pH value of the final solution to 9. The stirring rate is 250 rpm. The dropping rate is 9 mL / min; (4) Heat the reaction mixture and obtain high specific surface area alumina after post-treatment. The heating reaction temperature is 84 °C and the reaction time is 2 h. The post-treatment process includes filtration, washing, drying, and calcination. Oven drying is used for drying. The calcination temperature is 600 °C and the calcination time is 5.5 h.

[0040] The specific surface area (m 2 / g), pore diameter (nm), and pore volume (cm 3 / g) and other properties of the high specific surface area alumina prepared in Examples 1 - 11 and Comparative Examples 1 - 2 were tested by the gas adsorption method (BET), as shown in Tables 1 - 2 specifically.

[0041] Table 1 Properties of the high specific surface area alumina prepared in Examples 1 - 7

[0042] Table 2 Properties of the high specific surface area alumina prepared in Examples 8 - 11 and Comparative Examples 1 - 2

[0043] As can be seen from Table 1 and Table 2, the present invention uses a long-chain alkyl quaternary ammonium salt as the main template agent and modifier, and by adding a small amount of polyethylene glycol as an auxiliary surfactant, solves the technical problems of low specific surface area and small pore size of the alumina material prepared from the long-chain alkyl quaternary ammonium salt, and prepares an alumina product with a high specific surface area. The alumina material synthesized with the long-chain alkyl quaternary ammonium salt as the template agent has the advantages of regular mesopores, high order, easy control of pore size distribution and pore size. The pore size synthesized by the polyethylene glycol non-ionic surfactant is usually larger, and the pore size can be adjusted by changing the molecular chain length. At the same time, adding two kinds of cationic and non-ionic surfactants, namely the long-chain alkyl quaternary ammonium salt and polyethylene glycol, can give full play to the advantages of both: the long-chain alkyl quaternary ammonium salt cationic surfactant is easy to combine with the aluminum source during hydrolysis, while the polyethylene glycol non-ionic surfactant helps the formation of pores during precipitation and drying, thus preparing an alumina product with a high surface area and pore volume, and solving the technical problem of low specific surface area caused by simply using the long-chain alkyl quaternary ammonium salt.

[0044] Compared with Example 11, in Comparative Example 1, the long-chain alkyl quaternary ammonium salt was added to the meta-aluminate solution, and polyethylene glycol was added to the aluminum salt solution. Not only could polyethylene glycol not play its role, but also it was easy to cause a strong electrostatic interaction between the positively charged long-chain alkyl quaternary ammonium salt and the meta-aluminate, which was not conducive to the dispersion of crystal grains and affected the improvement of the specific surface area of the alumina product. Comparative Example 2 shows that since polyethylene glycol belongs to a polymer type surfactant, its own dosage can strongly affect the effect of the long-chain alkyl quaternary ammonium salt. Although polyethylene glycol has a templating effect, in this reaction system, its main role is to help the formation of pores during precipitation and drying, thus preparing an alumina product with a high surface area and pore volume; when the dosage of polyethylene glycol is too much, it will affect the formation of micelles and is not conducive to the improvement of the performance of the alumina product.

[0045] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention in other forms. Any person skilled in the art may use the technical content disclosed above to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing alumina with a high specific surface area, characterized in that, It includes the following steps: (1) Prepare an aluminum salt solution, add a long-chain alkyl quaternary ammonium salt thereto, and disperse uniformly by ultrasonic treatment; the mass ratio of the long-chain alkyl quaternary ammonium salt to the aluminum salt is (0.04 - 0.2):1; (2) Prepare a meta-aluminate solution, add polyethylene glycol thereto, and disperse uniformly by stirring; the number-average molecular weight of the polyethylene glycol is 200 - 2000; the mass ratio of the polyethylene glycol to the long-chain alkyl quaternary ammonium salt is (0.1 - 0.4):1; (3) Drop the solution obtained in step (2) into the solution obtained in step (1) to obtain a final solution, and adjust the pH of the final solution to be alkaline; (4) Carry out a heating reaction, and obtain high specific surface area alumina through post-treatment.

2. The preparation method of a high specific surface area alumina according to claim 1, characterized in that, In step (1), the aluminum salt is at least one of aluminum nitrate, aluminum chloride, and aluminum sulfate; the concentration of the aluminum salt solution is 10 - 40 g / L.

3. The preparation method of a high specific surface area alumina according to claim 1, characterized in that, In step (1), the ultrasonic power is 100 - 300 W; the long-chain alkyl quaternary ammonium salt is at least one of dodecyl trimethyl ammonium bromide, dodecyl trimethyl ammonium chloride, cetyl trimethyl ammonium bromide, cetyl trimethyl ammonium chloride, octadecyl trimethyl ammonium bromide, and octadecyl trimethyl ammonium chloride.

4. The preparation method of a high specific surface area alumina according to claim 1, characterized in that, In step (2), the meta-aluminate is at least one of sodium meta-aluminate or potassium meta-aluminate; the concentration of the meta-aluminate solution is 5 - 25 g / L.

5. The preparation method of a high specific surface area alumina according to claim 1, characterized in that, In step (2), the mass ratio of the meta-aluminate to the aluminum salt in step (1) is (0.5 - 1):1; the stirring rate in step (2) is 300 - 600 rpm.

6. The preparation method of a high specific surface area alumina according to claim 1, characterized in that, In step (3), the pH value is 7.5 - 10.

7. The preparation method of a high specific surface area alumina according to claim 1, characterized in that, In step (4), the heating reaction temperature is 75 - 95 °C, and the reaction time is 1 - 3 h.

8. The preparation method of a high specific surface area alumina according to claim 1, characterized in that, In step (4), the post-treatment is a process of filtration, washing, drying, and calcination.

9. The preparation method of a high specific surface area alumina according to claim 8, characterized in that, In step (4), drying is carried out by oven drying; the calcination temperature is 550 - 650 °C, and the calcination time is 5 - 6 h.

10. A high specific surface area alumina, characterized in that, It is prepared by the preparation method of a high specific surface area alumina according to any one of claims 1 - 9.

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