阅读说明：本技术 一种微波辅助燃烧法制备改性γ-Al2O3粉体的方法 (Method for preparing modified gamma-Al 2O3 powder by microwave-assisted combustion method ) 是由 赵旭光 孟竺 吴钳 付丽婷 储刚 于 2020-08-03 设计创作，主要内容包括：本发明公开了一种微波辅助燃烧法制备掺杂改性γ-Al<Sub>2</Sub>O<Sub>3</Sub>粉体的方法,耦合了微波辅助强化技术与自蔓延燃烧合成技术,以硝酸铝、甘氨酸、柠檬酸为原料,添加硝酸钴和硝酸镝作改性剂制备Co-Dy共掺的γ-Al<Sub>2</Sub>O<Sub>3</Sub>粉体的工艺方法。与生产γ-Al<Sub>2</Sub>O<Sub>3</Sub>粉体的现有技术相比,本发明工艺合成的γ-Al<Sub>2</Sub>O<Sub>3</Sub>粉体在相同的特征尺寸下具有更高的热稳定性,是一种新型的高热稳定性催化载体材料。(The invention discloses a method for preparing doped modified gamma-Al by a microwave-assisted combustion method 2 O 3 A powder preparation method couples a microwave-assisted strengthening technology and a self-propagating combustion synthesis technology, takes aluminum nitrate, glycine and citric acid as raw materials, and adds cobalt nitrate and dysprosium nitrate as modifiers to prepare Co-Dy Co-doped gamma-Al 2 O 3 A powder process method. And production of gamma-Al 2 O 3 Compared with the prior art of powder, the gamma-Al synthesized by the process of the invention 2 O 3 The powder has higher thermal stability under the same characteristic size, and is a novel high-thermal-stability catalytic carrier material.)

1. Doped modified gamma-Al prepared by microwave-assisted combustion method₂O₃The powder preparation method is characterized by comprising the following steps: 1) preparing a precursor solution: accurately weighing a proper amount of aluminum salt, a combustion agent and a modifier according to a proportion, putting the weighed raw materials into a crucible, adding a proper amount of distilled water, and putting the crucible on a magnetic stirrer for fully stirring for a certain time to obtain a precursor solution; 2) powder synthesis: the precursor solution is placed in a sealed heating device with a microwave generator, the microwave generator is started and the power is regulated to a preset value, in the process, along with the continuous rising of the system temperature, the moisture gradually decreases, the solution slowly becomes gel, when the moisture is completely evaporated and reaches an ignition point, in a short time, a large amount of smoke is gradually released, then the microwave generator is closed, after cooling, the precursor solution is moved to a muffle furnace to be heated to reach a specified temperature and treatment time, and finally the obtained product is white powder which is fluffy and snowflake-like.

2. The method for preparing doped modified gamma-Al by microwave-assisted combustion as claimed in claim 1₂O₃In the powder preparation method, aluminum salt in the precursor solution preparation step is aluminum nitrate, the combustion agent comprises glycine and citric acid, and the modifier comprises cobalt nitrate and dysprosium nitrate.

3. The method for preparing doped modified gamma-Al by microwave-assisted combustion as claimed in claim 1₂O₃The powder is prepared by mixing a combustion agent and an aluminum salt at a molar ratio of 3: 1-1: 1, preferably 2: 1, more preferably 5: and 3, the molar ratio of the modifier to the aluminum salt is (0.01-0.05): 1, preferably 0.02: 1, more preferably 0.03: 1.

4. according to claim 1The microwave-assisted combustion method is used for preparing doped modified gamma-Al₂O₃According to the powder preparation method, the mass ratio of distilled water to raw materials is 3: 1-1: 1, preferably 2: 1.

5. the method for preparing doped modified gamma-Al by microwave-assisted combustion as claimed in claim 1₂O₃The precursor mixing temperature is 60 ℃, preferably 90 ℃, the stirring speed is 40 revolutions per minute, preferably 60 revolutions per minute, and the mixing time is 1 hour, preferably 2 hours.

6. The method for preparing doped modified gamma-Al by microwave-assisted combustion as claimed in claim 1₂O₃The microwave power of the microwave-assisted process in the powder synthesis step is 500 watts, preferably 800 watts, and more preferably 700 watts.

7. The method for preparing doped modified gamma-Al by microwave-assisted combustion as claimed in claim 1₂O₃According to the powder synthesis method, in the powder synthesis step, after microwave combustion reaction, the powder is placed in a muffle furnace, the heating rate is 300 ℃/h, preferably 200 ℃/h, the end point temperature is 700-1000 ℃, preferably 1000 ℃, and the calcination time is 2-6 h, preferably 3 h.

Technical Field

The invention belongs to the technical field of material synthesis processes, and particularly relates to a microwave-assisted combustion method for preparing gamma-Al with high thermal stability₂O₃And (3) powder processing.

Background

At present, there have been found various crystalline aluminas, including α type, kappa type, theta type, chi type, η type, gamma type, rho type and β type, and aluminas of different space structures, wherein the aluminas of α type, β type and gamma type have wide applicationFor example, the α and gamma aluminas are in sharp contrast, α -Al₂O₃Is a product formed at high temperature, in contrast to gamma-Al₂O₃Is a product formed at low temperature. Reference to "activated alumina" is intended to mean activated gamma-Al₂O₃Due to the activity of gamma-Al₂O₃Has good chemical properties, can be used for preparing ceramic and catalyst carriers, adsorbents and drying agents, and is preferentially developed in the industries of information technology, optics, aerospace and the like. With the excellent characteristics and wide application of alumina, the method has attracted keen attention and research of overseas and overseas people.

In recent years, gamma-Al has been improved₂O₃The heat stability method mainly comprises the following steps: adding different modifiers, different preparation methods and different preparation methods of precursor solutions. Research shows that lanthanum nitrate and cerium nitrate are used as modifiers, and La and Ce are co-doped, so that the thermal stability of alumina can be effectively improved, and further the following results are proved: the La and Ce are jointly modified more effectively than the La alone. Therefore, the invention adopts the method of adding cobalt nitrate and dysprosium nitrate as modifiers and adopting microwave-assisted combustion to prepare the doped modified gamma-Al₂O₃The powder can improve the thermal stability.

Disclosure of Invention

The invention aims to provide a microwave-assisted combustion method for preparing gamma-Al with high thermal stability₂O₃And (3) powder processing.

The invention carries out doping modification on the gamma-Al₂O₃And (4) synthesizing powder. The technological process adopts microwave-assisted combustion synthesis technology and device, and the precursor solution containing aluminium salt, combustion agent and modifying agent is undergone the process of oxidation-reduction reaction in reaction device, and after the reaction the fluffy white powder similar to snowflake can be obtained, so that it is a new material for catalytic carrier with high specific surface area, small uniform grain size and high thermal stability.

The invention comprises the following steps:

the raw material is Al (NO)₃)₃·9H₂O；C₂H₅NO₂，C₆H₈O₇，Dy(NO₃)₃·6H₂O，Co(NO₃)₂·6H₂And O. In the combustion reaction, Al (NO)₃)₃·9H₂O，Dy(NO₃)₃·6H₂O，Co(NO₃)₂·6H₂O and C₂H₅NO₂Or C₆H₈O₇The molar ratio of the nitrate (oxidant) to the fuel (reductant) is calculated according to the thermochemical theory in the propellant chemistry.

The molar ratio is as follows: the molar ratio of the combustion agent to the aluminum salt is 3: 1-1: 1, the molar ratio of the modifier to the aluminum salt is 0.01-0.05: 1, adding 1 to 3 times of distilled water, heating the mixed solution to 60 to 90 ℃ by using a magnetic stirrer with heating, stirring at 40 to 60 revolutions per minute and mixing for 1 to 2 hours. The precursor is uniformly stirred and then placed in a microwave generator, and the microwave power is 500-800 watts. The solution slowly becomes gel, when the moisture is completely evaporated and reaches the ignition point, a large amount of smoke is gradually discharged in a short time, the microwave generator is closed, the solution is moved to a muffle furnace after being cooled, the temperature is raised to reach the specified temperature (700-1000 ℃) by adopting a program, the heat preservation time is 2-6 hours, and finally the obtained product is fluffy white powder similar to snowflake.

Compared with the prior preparation process, the invention has the following advantages:

1. the method has the characteristics of simple process, short preparation period, low equipment requirement, high yield and uniform distribution of reaction products, and is easy to realize industrial production.

2. The method can prepare bulk powder doped modified gamma-Al with high thermal stability by controlling the raw material ratio, preparing the solution precursor and setting the microwave-assisted self-propagating post-roasting temperature and constant-temperature roasting time₂O₃The powder has short reaction time and violent impact of combustion airflow, is favorable for refining particles, reduces the agglomeration degree among the particles, and is easy to operate in the control process.

Drawings

FIG. 1. gamma. -Al₂O₃Scanning electron microscopy of the powder. .

FIG. 2. gamma. -Al₂O₃XRD pattern of powder.

FIG. 3. gamma. -Al₂O₃N of powder₂Adsorption and desorption isotherms.

Detailed Description

The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention.