Method for synthesizing light-heat composite catalyst of 3-cyanopyridine

Abstract

The invention discloses a method for synthesizing a light-heat composite catalyst for 3-cyanopyridine, and the steps are as follows: V2O5 is uniformly dispersed in a mixed solution of ethanol and deionized water to obtain a uniformly dispersed mixed solution; Zn(CH3COO)2 is added to the mixed solution, a NaOH solution is added dropwise under continuous stirring, and the light yellow colloidal mixture is transferred to a hydrothermal reactor, the obtained solid is centrifuged, washed, and dried to obtain a corresponding powder, and the obtained powder is calcined to obtain the desired catalyst ZnO@V2O5; the prepared catalyst ZnO@V2O5 is subjected to illumination and heating conditions, and 3-methylpyridine is ammoxidized to prepare 3-cyanopyridine. Under the conditions of simultaneous illumination and heating, thermal catalysis is carried out while photocatalysis, and the synergistic effect between the catalytic effects of the two can reduce the reaction temperature of ammoxidation to synthesize 3-cyanopyridine and improve the reaction efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of 3-cyanopyridine synthesis, in particular to a method for synthesizing a light-heat composite catalyst of 3-cyanopyridine. Background Art

[0002] Cyanopyridine is also known as nicotinonitrile, 3-pyridinecarbonitrile, nicotinonitrile, nicotinic acid nitrile, nicotinic acid nitrile, 3-cyanopyrimidine, pyridine acid-3-nitrile, nicotinic acid cyanide, 3-cyanopyridine, nicotinic acid nitrile, nicotinic acid carbonitrile, etc. It is an important fine chemical intermediate, a raw material for medicine, pesticides and feed industries, and can be used to prepare vitamin B, nicotinamine, cardiotonic agents, insecticides, waterproofing agents, etc. At the same time, 3-cyanopyridine is the most important intermediate for the preparation of nicotinic acid and nicotinamide. Nicotinic acid, chemical name pyridine-3-carboxylic acid, is an organic compound with a chemical formula of C6H5NO2. It is a white crystalline powder, mainly found in animal viscera and muscle tissue, and also exists in trace amounts in fruits and egg yolks. It is one of the 13 essential vitamins for the human body.

[0003] At present, the most common method for synthesizing 3-cyanopyridine in the world is ammoxidation, that is, synthesizing 3-cyanopyridine by ammoxidation of 3-methylpyridine, and the active component is usually an oxide of V. For example, the method for preparing 3-cyanopyridine disclosed in Announcement No. CN1225460C can achieve a yield of more than 90% for 3-cyanopyridine at 405°C using an oxide of V and its supported material as a catalyst. The catalyst for preparing 3-cyanopyridine, its preparation method and use disclosed in Announcement No. CN 1151135C can achieve a yield of nearly 95% for synthesizing 3-cyanopyridine by ammoxidation of 3-methylpyridine at 633K using V2O5 and other oxides as the main active substances.

[0004] Although the above prior arts have relatively high yields of 3-cyanopyridine, there are problems of too high reaction temperature and high energy consumption. High temperature easily produces tar, causing the catalyst surface to be covered with tar, thereby reducing the catalyst activity. In addition, high-temperature reactions are dangerous and difficult to operate. Summary of the invention

[0005] The object of the present invention is to provide a method for synthesizing 3-cyanopyridine using a light-heat composite catalyst. Under conditions of simultaneous illumination and heating, thermal catalysis is performed simultaneously with photocatalysis. The synergistic effect between the catalytic effects of the two can reduce the reaction temperature of ammoxidation to synthesize 3-cyanopyridine and improve the reaction efficiency, thereby solving the problems in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The method for synthesizing a light-heat composite catalyst for 3-cyanopyridine comprises the following steps:

[0008] Step 1: Evenly disperse V2O5 in a mixed solution of ethanol and deionized water, and continue to stir and ultrasonicate for 30 minutes to obtain a uniformly dispersed mixed solution;

[0009] Step 2: Add Zn(CH3COO)2 to the mixed solution, stir slowly, add NaOH solution drop by drop under continuous stirring, stir at high speed and continue ultrasonication, transfer the light yellow colloidal mixture to a hydrothermal reactor, centrifuge, wash and dry the obtained solid to obtain the corresponding powder, then heat the obtained powder to 500℃ at 5℃ / min, calcine for 6h, and obtain the desired catalyst ZnO@V2O5;

[0010] Step 3: Prepare 3-cyanopyridine by ammoxidation of 3-methylpyridine using the prepared catalyst ZnO@V2O5 under light conditions and heating.

[0011] Furthermore, the volume mixing ratio of the mixed solution of ethanol and deionized water in step 1 is 1:1.

[0012] Furthermore, the molar ratio of the NaOH solution added in step 1 to Zn(CH3COO)2 is 2:1.

[0013] Furthermore, the mass fraction of the NaOH solution in step 2 is 35%-45%.

[0014] Furthermore, in the step 2, the molar ratio of Zn(CH3COO)2 to V2O5 powder is (2-10):1.

[0015] Furthermore, in the step 2, after the NaOH solution is added dropwise, high-speed stirring is performed and ultrasound is continued for 30 minutes.

[0016] Furthermore, in the step 2, the temperature in the hydrothermal reactor is kept at 180° C. for 6 hours.

[0017] Furthermore, in step three, illumination and heating are performed simultaneously.

[0018] Furthermore, the illumination and heating conditions include 120°C without illumination or 200 mW / cm at room temperature. 2 200mW / cm2 under illumination conditions or 120℃ 2 under lighting conditions.

[0019] The working principle of the present invention is as follows: the obtained catalyst ZnO@V2O5, i.e., the catalyst ZV series, has V2O5 as an active component and ZnO as a support in thermal catalysis, and both V2O5 and ZnO as photocatalytic active components in photocatalysis, and the two constitute a Z-type heterojunction; and under the conditions of high temperature and sufficient light, photocatalytic ammoxidation and thermal catalytic ammoxidation reactions proceed simultaneously, and there is a synergistic effect between the two, so that the effect of ammoxidation to synthesize 3-cyanopyridine is better than the single thermal catalytic effect and photocatalytic effect.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention utilizes V2O5 as an active component and ZnO as a support to synthesize 3-cyanopyridine through the synergistic effect of photocatalysis and thermal catalysis, so that the reaction temperature is lower and the synthesis conditions are milder, providing a new idea for the preparation of 3-cyanopyridine and similar reactions. In addition, the catalyst preparation method of the present invention is simple, and the catalyst can be used as a thermal catalyst and a photocatalyst for forming a Z-type heterojunction. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Example 1: V2O5 was uniformly dispersed in a mixed solution of ethanol and deionized water (ethanol: deionized water = 1:1), and the mixture was continuously stirred and ultrasonicated for 30 minutes, and then Zn (CH3COO) 2 was added, which was twice the amount of V2O5. NaOH solution was added dropwise under continuous stirring (the molar ratio of NaOH solution to Zn (CH3COO) 2 was 2:1), and the mixture was stirred at high speed and ultrasonicated for 30 minutes. After that, the light yellow colloidal mixture was transferred to a hydrothermal reactor and kept warm at 180°C for 6 hours. The obtained solid was then centrifuged, washed, and dried to obtain the corresponding powder. The obtained powder was then heated to 500°C at 5°C / min and calcined for 6 hours. Catalyst 2ZnO@V2O5, namely ZV-2-1, was obtained. Catalyst ZV-2-1 was heated at 120°C without light and at room temperature at 200mW / cm 2 Under the illumination conditions and 200mW / cm at 120℃ 2 The experiment of synthesizing 3-cyanopyridine by ammoxidation of 3-methylpyridine was carried out under light conditions.

[0024] Example 2: V2O5 is uniformly dispersed in a mixed solution of ethanol and deionized water (ethanol: deionized water = 1:1), and the mixture is continuously stirred and ultrasonicated for 30 minutes, and then Zn (CH3COO) 2 is added, which is 5 times the amount of V2O5. NaOH solution is added dropwise under continuous stirring (the molar ratio of NaOH solution to Zn (CH3COO) 2 is 2:1), and the mixture is stirred at high speed and ultrasonicated for 30 minutes. After that, the light yellow colloidal mixture is transferred to a hydrothermal reactor and kept warm at 180°C for 6 hours. The obtained solid is then centrifuged, washed, and dried to obtain the corresponding powder, and then the obtained powder is heated to 500°C at 5°C / min and calcined for 6 hours. Catalyst 5ZnO@V2O5, namely ZV-5-1, is obtained. Catalyst ZV-5-1 is heated at 120°C without light and at 200mW / cm 2 Under the illumination conditions and 200mW / cm at 120℃ 2 The experiment of synthesizing 3-cyanopyridine by ammoxidation of 3-methylpyridine was carried out under light conditions.

[0025] Example 3: V2O5 was uniformly dispersed in a mixed solution of ethanol and deionized water (ethanol: deionized water = 1:1), and the mixture was continuously stirred and ultrasonicated for 30 minutes, and then Zn (CH3COO) 2 was added, which was 10 times the amount of V2O5. NaOH solution was added dropwise under continuous stirring (the molar ratio of NaOH solution to Zn (CH3COO) 2 was 2:1), and the mixture was stirred at high speed and ultrasonicated for 30 minutes. After that, the light yellow colloidal mixture was transferred to a hydrothermal reactor and kept warm at 180°C for 6 hours. The obtained solid was then centrifuged, washed, and dried to obtain the corresponding powder. The obtained powder was then heated to 500°C at 5°C / min and calcined for 6 hours. Catalyst 10ZnO@V2O5, namely ZV-10-1, was obtained. Catalyst ZV-10-1 was heated at 120°C without light and 200mW / cm at room temperature. 2 Under the illumination conditions and 200mW / cm at 120℃ 2 The experiment of synthesizing 3-cyanopyridine by ammoxidation of 3-methylpyridine was carried out under light conditions.

[0026] Example 4: V2O5 is uniformly dispersed in a mixed solution of ethanol and deionized water (ethanol: deionized water = 1:1), and the mixture is continuously stirred and ultrasonicated for 30 minutes, and then Zn (CH3COO) 2 is added, which is 20 times the amount of V2O5. NaOH solution is added dropwise under continuous stirring (the molar ratio of NaOH solution to Zn (CH3COO) 2 is 2:1), and the mixture is stirred at high speed and ultrasonicated for 30 minutes. After that, the light yellow colloidal mixture is transferred to a hydrothermal reactor and kept warm at 180°C for 6 hours. The obtained solid is then centrifuged, washed, and dried to obtain the corresponding powder, and then the obtained powder is heated to 500°C at 5°C / min and calcined for 6 hours. Catalyst 20ZnO@V2O5, namely ZV-20-1, is obtained. Catalyst ZV-20-1 is heated at 120°C without light and at room temperature at 200mW / cm 2 Under the illumination conditions and 200mW / cm at 120℃ 2 The experiment of synthesizing 3-cyanopyridine by ammoxidation of 3-methylpyridine was carried out under light conditions.

[0027] The experimental results of Examples 1-4 are shown in Table 1 below.

[0028]

[0029] As shown in Table 1, at 120°C without light, the maximum yield of 3-cyanopyridine does not exceed 50%, and the selectivity does not exceed 80%. 2 Without heating, the maximum yield of 3-cyanopyridine was no more than 30%, and the selectivity was no more than 70%. 2 Under the conditions of heating at 120 degrees Celsius, the yield and selectivity of 3-cyanopyridine are higher than those under single conditions (heating without light or room temperature with light). 2 When heated to 120 degrees Celsius, the highest yield and selectivity of 3-cyanopyridine was achieved when the molar ratio of Zn(CH3COO)2 to V2O5 powder was 10:1, and the yield and selectivity of 3-cyanopyridine were both over 95%, indicating that when the molar ratio of Zn(CH3COO)2 to V2O5 powder was 10:1, the yield and selectivity of 3-cyanopyridine were higher than those of other molar ratios of Zn(CH3COO)2 to V2O5 powder. This is because V2O5 is a thermal catalyst loaded with ZnO as a carrier; and both ZnO and V2O5 can be used as photocatalysts, forming a direct Z-type heterojunction according to the positions of their VB and CB; under the conditions of heating and illumination, thermal catalysis and photocatalysis synergistically promote the generation of 3-cyanopyridine from 3-methylpyridine.

[0030] The present invention sets up three control examples for the experiment of catalyst ZV-10-1 obtained by the molar ratio of Zn(CH3COO)2 to V2O5 powder being 10:1, which differs from Example 3 only in illumination and heating. The three control examples are as follows:

[0031] Comparative Example 1: The illumination and heating conditions include 80°C without illumination and 200 mW / cm2 at room temperature. 2 Under the light condition of 200mW / cm2 at 80℃ 2 under lighting conditions.

[0032] Comparative Example 2: Light and heating conditions include 100°C without light and 200mW / cm2 at room temperature 2 Under the light condition of 200mW / cm2 at 100℃ 2 under lighting conditions.

[0033] Comparative Example 3: Light and heating conditions include 140°C without light and 200mW / cm2 at room temperature 2 Under the light condition of 200mW / cm2 at 140℃ 2 under lighting conditions.

[0034] The comparison results of the control example and embodiment 3 are shown in Table 2 below:

[0035]

[0036] From Table 2, we can see that under the illumination condition of 200mW / cm 2 Under the conditions of 120 degrees Celsius and heating, the yield and selectivity of 3-cyanopyridine reached the highest, both exceeding 95%, which was higher than the control examples of other illumination conditions and heating conditions. From the changes in the yield and selectivity of 3-cyanopyridine, the yield and selectivity of 3-cyanopyridine gradually increased from control example 1, control example 2 and embodiment 3. When the illumination and heating conditions of embodiment 3 were reached, the yield and selectivity of 3-cyanopyridine reached the highest, and then began to decline, which shows that the illumination condition of embodiment 3 is 200mW / cm 2 The conditions of heating at 120 degrees Celsius are the most suitable, which can maximize the yield and selectivity of 3-cyanopyridine, both exceeding 95%.

[0037] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for synthesizing 3-cyanopyridine using a light-heat composite catalyst, characterized in that: The steps include: Step 1: Evenly disperse V2O5 in a mixed solution of ethanol and deionized water, and continue to stir and ultrasonicate for 30 minutes to obtain a uniformly dispersed mixed solution; Step 2: Add Zn(CH3COO)2 to the mixed solution, stir slowly, add NaOH solution drop by drop while stirring continuously, stir at high speed and continue ultrasonication, transfer the light yellow colloidal mixture to a hydrothermal reactor, centrifuge, wash and dry the obtained solid to obtain the corresponding powder, then heat the obtained powder to 500℃ at 5℃ / min, calcine at 500℃ for 6h to obtain the desired catalyst ZnO@V2O5; Step 3: Prepare 3-cyanopyridine by ammoxidation of 3-methylpyridine using the prepared catalyst ZnO@V2O5 under light and heating conditions; The obtained catalyst ZnO@V2O5 belongs to the catalyst ZV series. In thermal catalysis, V2O5 serves as the active component and ZnO serves as the support. In photocatalysis, both V2O5 and ZnO serve as photocatalytic active components. According to the positions of VB and CB in V2O5 and ZnO, a direct Z-type heterojunction is formed. Under the conditions of heating and illumination, the photocatalytic ammoxidation and thermal catalytic ammoxidation reactions act synergistically at the same time, promoting the generation of 3-cyanopyridine from 3-methylpyridine.

2. The method for synthesizing 3-cyanopyridine using a light-heat composite catalyst according to claim 1, characterized in that: The volume mixing ratio of the mixed solution of ethanol and deionized water in step 1 is 1:

1.

3. The method for synthesizing 3-cyanopyridine using a light-heat composite catalyst according to claim 1, characterized in that: The molar ratio of the NaOH solution added in step 1 to Zn(CH3COO)2 is 2:

1.

4. The method for synthesizing 3-cyanopyridine using a light-heat composite catalyst according to claim 1, characterized in that: The mass fraction of the NaOH solution in step 2 is 35%-45%.

5. The method for synthesizing 3-cyanopyridine using a light-heat composite catalyst according to claim 1, characterized in that: In the step 2, the molar ratio of Zn(CH3COO)2 to V2O5 powder is (2-10):

1.

6. The method for synthesizing 3-cyanopyridine using a light-heat composite catalyst according to claim 1, characterized in that: In the step 2, after the NaOH solution is added dropwise, the mixture is stirred at high speed and ultrasonicated for 30 minutes.

7. The method for synthesizing 3-cyanopyridine using a light-heat composite catalyst according to claim 1, characterized in that: In the step 2, the temperature in the hydrothermal reactor is kept at 180° C. for 6 hours.

8. The method for synthesizing 3-cyanopyridine using a light-heat composite catalyst according to claim 1, characterized in that: In the step three, illumination and heating are carried out simultaneously.

9. The method for synthesizing 3-cyanopyridine using a light-heat composite catalyst according to claim 8, characterized in that: 200mW / cm2 at 120℃ for light and heating 2 under lighting conditions.

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