Background technology
At present, the alkoxide method has been widely used to produce high-purity 5N aluminum isopropoxide (that is, aluminum isopropoxide with a mass purity of 99.999%). Isopropyl alcohol is used to react with aluminum, and different types of reagents are used as initiators. Agent, the initiators used here mainly include HgCl2, HgI2, anhydrous AlCl3, I2, and aluminum isopropoxide.
1. Use mercuric chloride and mercuric iodide as initiators. Although they are highly efficient, they are highly toxic, and the Hg generated during the reaction will enter the product, which has certain effects on the use of the product. Impact.
2. Anhydrous aluminum trichloride is used as a catalyst to synthesize aluminum isopropoxide. The aluminum chloride needs to be dissolved in isopropyl alcohol at low temperature and then added to the reactor. This reactor equipment has strict requirements and cannot be used. Stainless steel reactors, only enamel reactors can be used. The mass fraction of the catalyst anhydrous aluminum chloride in isopropyl alcohol is 0.2% -0.4%.
3. Use I2 as a catalyst in a larger amount, with a mass concentration of 1.3mg/ml in isopropyl alcohol. Not suitable for application in industrial production.
4. Using aluminum isopropoxide as an initiator can reduce the introduction of impurities, but the reaction rate cannot be improved.
The problems existing in the above-mentioned technologies have always been something that various business units need to urgently solve. In view of the problems existing in the prior art, the present invention adopts a new initiator to replace mercuric chloride, mercuric iodide and aluminum isopropoxide in the original process. It can improve the efficiency of the reaction without affecting the product quality.
Content of the invention
In view of the problems existing in the existing technology, this invention uses new initiators to replace mercury chloride, mercury iodide and aluminum isopropoxide in the original process, and invented a preparation of high-purity 5N aluminum isopropoxide. method. It can improve the efficiency of the reaction without affecting the product quality.
The technical solution of the present invention is:
A method for preparing high-purity 5N aluminum isopropoxide, using isopropyl alcohol and metallic aluminum as raw materials, using a mixture of anhydrous aluminum trichloride and 5N aluminum isopropoxide as a catalyst, characterized by isopropyl alcohol Aluminum is added in two steps during the preparation process. The aluminum isopropoxide added in the first step removes the water in isopropyl alcohol. In the second step, aluminum isopropoxide and aluminum trichloride are added simultaneously to act as a catalyst. The preparation steps are as follows:
(1) Add isopropyl alcohol to the reaction kettle. According to the moisture content in isopropyl alcohol, add 5N aluminum isopropoxide into isopropyl alcohol. The molar ratio of water to aluminum isopropoxide is 3:1- 2. Stir at room temperature;
(2) Add anhydrous aluminum trichloride and 5N aluminum isopropoxide to the isopropyl alcohol from which water has been removed in step (I) at the same time. The temperature is normal temperature and stirred for 3-10 minutes. The mass ratio is: anhydrous Aluminum trichloride:aluminum isopropoxide:isopropyl alcohol=0.05-0.1:0.25-0.5:100;
(3) Add the metal aluminum particles to the isopropyl alcohol in the previous step, condense and reflux the reaction in the reactor, the reflux temperature is 80-90°C, the reaction time is 3-5 hours, the ratio of metal aluminum and isopropyl alcohol The molar ratio is 1:3-4;
(4) Distill the reactant obtained in step (3) under normal pressure to recover unreacted isopropanol. The distillation temperature is 80-90°C, and the isopropyl alcohol is condensed to recover isopropyl alcohol;
(5) Distill the material after distillation to recover isopropanol under reduced pressure. The pressure is 1333Pa (absolute pressure). Collect the 135-145°C fraction to obtain the 5N aluminum isopropoxide fraction.
In the present invention, it is preferred that anhydrous aluminum trichloride is analytically pure (AR); isopropyl alcohol is analytically pure (AR), and the moisture content is ≤0.2% (mass).
The purity of the metallic aluminum used in the present invention is 99.996% (mass content);
The reflux reaction temperature in step (3) of the present invention is preferably 85°C;
In step (4) of the present invention, the atmospheric distillation temperature is preferably 85°C, and isopropanol is recovered by condensation;
High-purity 5N aluminum isopropoxide in this manual refers to aluminum isopropoxide with a purity of 99.999% (mass).
In the present invention, the yield of aluminum isopropoxide reaches more than 90% (equivalent to aluminum).
In step (1) of the present invention, the amount of aluminum isopropoxide preferably added is such that the molar ratio of water to isopropyl alcohol is 2:1.
Compared with the existing technology, the substantial features and beneficial effects of the present invention are:
In the stage of initiating the isopropyl alcohol reaction, this method uses anhydrous aluminum trichloride and aluminum isopropoxide as initiators, and the aluminum isopropoxide is added in steps to reduce the initiating time. Only add aluminum trichloride, the amount is 0.2-0.4% of isopropyl alcohol, the initiation time is 90 minutes, the reaction time is 8-10 hours; add aluminum isopropoxide at one time, and then add 0.05-0.10% of the amount of isopropyl alcohol. % aluminum trichloride, the initiation time is 85-90min, and the reaction time is 7_8 hours; aluminum isopropoxide is added in two steps, the initiation time is 50-60min, and the reaction time is 3_5 hours. The hydrolysis reaction of 5N aluminum isopropoxide consumes the water in isopropyl alcohol. During hydrolysis, the amount of aluminum isopropoxide is controlled, and the hydrolyzate of aluminum isopropoxide is controlled. This eliminates a small amount of reaction and anhydrous trichlorination of the initiator. The influence of aluminum will not affect the catalytic effect of the subsequent addition of the mixture of aluminum isopropoxide and aluminum trichloride. The use of mixed catalysts improves the efficiency of the reaction between isopropyl alcohol and aluminum, shortens the production cycle, improves production efficiency, and reduces costs.
Due to the addition of aluminum trichloride and aluminum isopropoxide as co-initiators, the amount of aluminum trichloride is reduced. At the same time, due to the addition of aluminum isopropoxide to remove water, aluminum trichloride is added at room temperature, which does not It requires low temperature operation and at the same time reduces the acidity. The use of stainless steel reactor can meet the requirements.
Specific implementation plan
The following is further described in conjunction with the examples.invention, but does not limit the scope of protection of the invention.
Inject 40kg of isopropanol (AR) into the reaction kettle, add 452g of 5N aluminum isopropoxide to the isopropanol at room temperature, stir for 5 minutes at room temperature, and then add 30g of anhydrous aluminum trichloride to the isopropanol. Add 160g of isopropyl alcohol and stir for 5 minutes; add 4.5kg of aluminum particles, set the reflux reaction at 85°C, the reaction initiation time is 50min, and the reaction ends in 4 hours; set 85°C to perform normal pressure distillation of the above reactants, and recover the foreign matter. Propanol; distill the contents of the still under atmospheric pressure distillation under reduced pressure at 1333 Pa (absolute pressure), collect the 135°C-145°C fraction, and obtain aluminum isopropoxide.
After testing, the reaction is relatively fast through the above method, the yield of aluminum isopropoxide is 91.5% (relative to aluminum), and the purity of the prepared high-purity aluminum isopropoxide is greater than 99.999%, meeting the quality requirements.
