Background technology
Benzyl alcohol can be used as an important pharmaceutical intermediate. Nowadays, benzyl alcohol is commonly produced by catalytic hydrogenation, zinc powder reduction or NaBH4 reduction. However, the above three methods all have shortcomings, which are as follows:
(1) Using the catalytic hydrogenation method will reduce a large amount of by-products at the same time, and the subsequent processing of the by-products is complicated;
(2) When using the zinc powder reduction method, a crude product needs to be made first, and then the crude product is reacted with petroleum ether, water, concentrated sulfuric acid and activated carbon to produce benzyl alcohol; not only is the process complicated, Moreover, concentrated sulfuric acid causes great pollution and damage to the environment and reaction equipment;
(3), NaBH4 reduction method requires the use of a large amount of NaBH4, the yield is low, and the by-product boric acid ester is also accompanied during the reaction process.
Content of the invention
In view of this, it is necessary to provide a preparation method of benzoyl alcohol to solve the technical problems of low yield, complex process, large pollution and high energy consumption in the existing preparation of benzoyl alcohol.
In order to achieve the above purpose, the present invention provides a preparation method of benzyl alcohol, which includes the following steps: the first step is to add the raw materials into the reaction kettle for reaction; the second step is to take a sample to determine the reaction end point; The third step is to hot filter and obtain benzyl alcohol crystals, and the fourth step is to dry it to obtain the finished product of benzyl alcohol. In the first step, the raw materials added are methanol, water, caustic soda, benzophenone and aluminum powder. , and the molar ratio of benzophenone, aluminum powder and caustic soda is 1:0.9-1:1.1, and the concentration of methanol is 60~70%.
Further, the molar ratio of benzophenone, aluminum powder and caustic soda is 1:0.9:1.1.
Further, the first step includes the following stages in sequence: in the first stage, add methanol and water to the reaction kettle, and maintain the temperature at 15°C to test the concentration of methanol; in the second stage, when the After the methanol concentration in the first stage meets the requirements, put caustic soda into the reaction kettle and measure the alkali concentration; in the third stage, when the alkali concentration in the second stage meets the requirements, put benzophenone into the reaction kettle and fully After stirring, keep it warm at 47 to 4°C for a predetermined time; in the fourth stage, keep the temperature at 47 to 4°C unchanged, and add aluminum powder into the reaction kettle at a constant speed in batches and at intervals.
Further, in the first stage, the concentration of methanol is tested with an alcohol hydrometer.
Further, at a temperature of 15°C, when the concentration of methanol in the first stage is 67.0±0.5%, the second stage is carried out and caustic soda is added into the reaction kettle.
Further, when the concentration of methanol in the first stage is 67%, the second stage is carried out and caustic soda is added into the reaction kettle.
Further, in the second stage, the alkali concentration is determined using acid-base titration.
Further, when the temperature is 60°C and the alkali concentration is 5.4~5.5%, the third stage is performed and benzophenone is put into the reaction kettle.
Further, in the third stage, the benzophenone is stirred thoroughly and then kept at a temperature of 47 to 4°C for 5 minutes.
Further, in the fourth stage, the weight of aluminum powder dropped each time decreases, and the time interval between two adjacent aluminum powder drops also decreases.
The beneficial effects brought by the technical solutions provided by the embodiments of the present invention are: the remaining slag and alkaline water from the preparation method of benzyl alcohol of the present invention are neutralized, causing less pollution to the environment. Moreover, the preparation method of benzyl alcohol of the present invention has simple procedures, high yield, and low energy consumption.
In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be described in further detail below with reference to the drawings.
Explanation of pictures
The drawings forming a part of this application are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the attached picture:
Fig. 1 is a schematic flow diagram of a preparation method of benzyl alcohol according to a preferred embodiment of the present invention.
Detailed implementation
In order to better understand the present invention, the embodiments of the invention will be described in detail below with reference to the accompanying drawings.
Please refer to Figure 1. The preparation method of benzyl alcohol provided by the preferred embodiment of the present invention includes the following steps:
Step 1 S1: Add methanol, water, caustic soda, benzophenone and aluminum powder to the reaction kettle in order to allow full reaction. Preferably, the concentration of methanol is 60-70%, most preferably, the concentration of methanol is 67.0±0.5%, and the best is 67%. Preferably, the molar ratio of benzophenone, aluminum powder and caustic soda in the reaction kettle is 1:0.9 to 1:1.1; most preferably, the molar ratio of benzophenone, aluminum powder and caustic soda in the reaction kettle is The proportional relationship is 1:0.9:1.1.
Specifically, the above-mentioned first step SI proceeds through the following stages in sequence: First, in the first stage S11, add methanol and water to the reaction kettle, keep the temperature at 15°C, and test the concentration of methanol with an alcohol hydrometer. .
Next, in the second stage S13, when the concentration of methanol is 67%, caustic soda is put into the reaction kettle and the temperature is raised to 60°C. After thorough stirring, determine the alkali concentration using acid-base titration.
In the third stage S I 5, when the alkali concentration is 5.4~5.5%, put benzophenone into the reaction kettle.After adding the benzophenone, mix thoroughly, cool down to 47~54°C, and then keep it warm for a period of time. Preferably, the temperature is maintained for 5 minutes after dropping to 47°C.
In the fourth stage SI 7, while the above temperature remains unchanged at 47~54°C, aluminum powder is added to the reaction kettle in batches and at intervals. The weight of aluminum powder dropped each time decreases, and the time interval between two adjacent aluminum powder drops also decreases. Each time aluminum powder is added, it must be added spoon by spoon at a uniform speed. Preferably, the time for each injection of aluminum powder is one minute. After the aluminum powder is added, raise the temperature to 50°C to 55°C and maintain it for 30 minutes. The following is an example of adding 40kg aluminum powder to illustrate the specific process. First, add 4kg aluminum powder into the reaction kettle and wait for 30 minutes. Then, repeat the above-mentioned weight and interval of aluminum powder added three times, and then add 12kg of aluminum powder into the reactor; then, add 3kg of aluminum powder into the reactor with an interval of 15 minutes, then repeat the above-mentioned weight of aluminum powder. Add 6kg of aluminum powder into the reaction kettle twice with an interval of 2 times; then, add 2kg of aluminum powder into the reaction kettle with an interval of 8 minutes, then repeat the weight of aluminum powder and the interval of 2 times before adding the aluminum powder to the reaction kettle. Add 4kg of aluminum powder to the kettle; finally, add 1kg of aluminum powder to the reactor and wait for 5 minutes, then repeat the weight and interval of the aluminum powder for 8 times and then add 8kg of aluminum powder to the reactor. Done.
The formula of the present invention will be further described below in conjunction with the examples, and the preparation method is as described above. Among them, the corporate standard for the purity of benzyl alcohol is purity ≥99.5%.
