Method for synthesizing glyoxal through gas-phase catalytic oxidation of ethylene glycol

Abstract

The invention relates to the technical field of synthesis of chemical products, and particularly discloses a method for synthesizing glyoxal through gas-phase catalytic oxidation of ethylene glycol. According to the scheme provided by the invention, the good catalytic activity of the catalyst is maintained, the favorable condition of a high-temperature environment is fully utilized, the defect of poor activity of a silver catalyst in the high-temperature environment is overcome, and the yield of glyoxal is favorably improved. On the basis, a more appropriate reaction temperature range is further optimized, a catalytic system at a lower temperature is improved, and a higher glyoxal yield is obtained under various different temperature conditions.

Description

Technical Field

[0001] The present application relates to the technical field of chemical product synthesis, and more specifically, to a method for synthesizing glyoxal by gas-phase catalytic oxidation of ethylene glycol. Background Art

[0002] Glyoxal is a fine chemical product with a molecular formula of C2H2O2, which is easily soluble in water and commonly used organic solvents. There are two main methods for producing glyoxal at present, namely ethylene glycol oxidation method and acetaldehyde nitric acid oxidation method. Although the acetaldehyde nitric acid oxidation method has a simple process and low requirements for reaction temperature and pressure, it has limited yield and is difficult to apply on a large scale. The principle of the gas phase method is that ethylene glycol is oxidized in the presence of a catalyst using air or oxygen to convert ethylene glycol into glyoxal, which is relatively more suitable for large-scale production.

[0003] In the related art, there is a glyoxal preparation process, which includes the following steps: preheating ethylene glycol to vaporize it and then mixing it with air and inert gas, and inputting the mixed gas into a catalytic reactor equipped with a silver catalyst, and carrying out the reaction at a reaction temperature of 600°C and a reaction pressure of 0.9MPa. The reaction product is chilled to 230°C with water, and then sent to an absorption tower for absorption to obtain a finished product.

[0004] With respect to the above-mentioned related technologies, the inventors believe that the gas-phase catalytic reaction in the related technologies is carried out at a relatively high temperature, and the electrolytic silver catalyst is prone to sintering and agglomeration under such temperature conditions, resulting in a limited yield of glyoxal. Summary of the invention

[0005] In the related art, the gas phase catalytic reaction is carried out at a relatively high temperature, and the electrolytic silver catalyst is prone to sintering and agglomeration under such temperature conditions, resulting in a limited yield of glyoxal. In order to improve this defect, the present application provides a method for synthesizing glyoxal by gas phase catalytic oxidation of ethylene glycol.

[0006] The present application provides a method for synthesizing glyoxal by gas-phase catalytic oxidation of ethylene glycol, which adopts the following technical scheme: A method for synthesizing glyoxal by gas-phase catalytic oxidation of ethylene glycol comprises the following steps: (1) calcining the composite catalyst and granulating it, then loading it into a reactor and preheating it for standby use; the composite catalyst comprises a lanthanum-loaded silver catalyst, and the lanthanum-loaded silver catalyst is a crystalline silver powder containing nano-lanthanum oxide; (2) vaporizing ethylene glycol to obtain ethylene glycol vapor; preheating a mixture of air, water vapor and circulating gas, and mixing the mixture with the ethylene glycol vapor to obtain a raw gas; (3) The raw gas is input into a reactor containing catalyst particles for reaction, the product is quenched, and the crude glyoxal solution is obtained after absorption in an absorption tower. The remaining tail gas is treated in an absorption tower and a washing tower, and after the waste gas that meets the emission standards is discharged, the remaining tail gas is used as circulating gas; (4) distilling, purifying and decolorizing the crude glyoxal solution to obtain glyoxal.

[0007] By adopting the above technical scheme, the present application uses a lanthanum-loaded silver catalyst to catalytically oxidize ethylene glycol. Nano-lanthanum oxide can form a physical interval in the crystalline silver powder, which not only reduces the particle size of the crystalline silver powder, but also inhibits the agglomeration of the crystalline silver powder during the high-temperature catalytic process, and hinders the growth of the average particle size of the crystalline silver powder due to agglomeration, so the lanthanum-loaded silver catalyst can maintain good catalytic activity and stability under high temperature conditions. The reaction of ethylene glycol to glyoxal can be summarized as follows: (CH20H)2+02→(CH0)2+2H20; (CH20H)2→(CHO)2+2H2; 2H2+02→2H20; Among them, the dehydrogenation reaction in the second step is the main reaction for producing glyoxal, and it is also an endothermic reaction, so high temperature conditions are more favorable for the generation of glyoxal. It can be seen that the scheme of the present application not only keeps the catalyst in good catalytic activity, but also makes full use of the favorable condition of the high temperature environment, overcomes the defect of poor activity of the silver catalyst in the high temperature environment, and helps to fully improve the yield of glyoxal under higher temperature conditions.

[0008] Preferably, the lanthanum-supported silver catalyst is prepared according to the following method: The electrolytic cell containing silver nitrate solution is placed in an ultrasonic generator, platinum is used as a cathode, silver is used as an anode, and nano-lanthanum oxide is added to the cathode region of the electrolyte. Electrolysis is carried out under heat preservation conditions, and the electrolysis product is collected. After grinding with zirconium oxide balls as grinding balls and anhydrous ethanol as a grinding medium, a lanthanum-loaded silver catalyst is obtained.

[0009] By adopting the above technical solution, the present application puts nano-lanthanum oxide as the second phase into the electrolytic cell for electrolyzing the silver nitrate solution, and keeps the nano-lanthanum oxide suspended by an ultrasonic generator. When the anions in the cathode region are reduced to produce crystalline silver, the nano-lanthanum oxide will be doped in the crystalline silver. Then, after grinding treatment, a lanthanum-loaded silver catalyst with a certain surface roughness can be obtained.

[0010] Preferably, the concentration of nano-lanthanum oxide in the electrolyte is 1-10wt%.

[0011] By adopting the above technical solution, the present application optimizes the concentration of nano-lanthanum oxide in the electrolyte. Within the above concentration range, the doping of nano-lanthanum oxide in crystalline silver can be achieved, thereby obtaining a lanthanum-loaded silver catalyst.

[0012] Preferably, the concentration of nano-lanthanum oxide in the electrolyte is 5-10wt%.

[0013] By adopting the above technical solution, the present application optimizes the concentration of nano-lanthanum oxide in the electrolyte, which helps to obtain a lanthanum-loaded silver catalyst with a higher lanthanum doping amount, and helps to improve the yield of glyoxal.

[0014] Preferably, in step (3) of the method, the reaction temperature is 400-600°C.

[0015] By adopting the above technical solution, the present application optimizes the reaction temperature for catalytic synthesis of glyoxal, and the catalytic synthesis of glyoxal can be achieved within the above temperature range.

[0016] Preferably, in step (3) of the method, the reaction temperature is 470-560°C.

[0017] By adopting the above technical scheme, the present application further optimizes the reaction temperature of catalytic synthesis of glyoxal. As the temperature decreases, although the promoting effect of temperature on the reaction is weakened, the side reaction will also be suppressed. Within the range of 470-560 ° C, the agglomeration of the lanthanum-supported silver catalyst is not serious, and the catalytic activity can be fully exerted, and the side reaction is less, and a higher glyoxal yield can be obtained. When it is lower than 470 ° C, due to the limited promoting effect of temperature on the reaction, even if the side reaction is fully suppressed, it is difficult to obtain a higher glyoxal yield.

[0018] Preferably, in step (3) of the method, the oxygen-to-alcohol ratio of the reaction is 1-1.6.

[0019] By adopting the above technical scheme, the present application optimizes the oxygen-to-alcohol ratio of the catalytic synthesis of ethylene glycol. Within the above oxygen-to-alcohol ratio range, the total amount of oxygen can meet the demand for oxidizing ethylene glycol, thereby realizing the synthesis of glyoxal.

[0020] Preferably, in step (3) of the method, the oxygen-to-alcohol ratio of the reaction is 1.2-1.5.

[0021] By adopting the above technical scheme, the present application preferably has the oxygen-to-alcohol ratio of catalytic synthesis of ethylene glycol reaction. The rise of the oxygen-to-alcohol ratio can promote the conversion of ethylene glycol on the one hand, and also promote the carrying out of side reactions on the other hand, so it cannot be too low or too high. Within the above oxygen-to-alcohol ratio range, side reaction products are relatively few, and glyoxal can obtain higher yield.

[0022] Preferably, in step (3) of the method, the reaction temperature is 400° C., the composite catalyst further comprises a zirconium-supported silver catalyst, and the zirconium-supported silver catalyst is prepared according to the following method: (1) dropping ammonia water into a zirconium oxychloride solution for reaction, collecting the precipitate, washing it with water, filtering it, drying it, and then calcining it to obtain a zirconium carrier; (2) The zirconium carrier is immersed in a silver nitrate solution, and then the zirconium carrier is taken out and dried, and then calcined to obtain a zirconium-supported silver catalyst.

[0023] By adopting the above technical solution, the present application loaded silver on the basis of preparing a zirconium carrier to obtain a zirconium-supported silver catalyst. The zirconium in the zirconium-supported silver catalyst exists in the form of zirconium dioxide, which can not only reduce the agglomeration of silver, but also enable silver to have a higher catalytic activity at 400°C, which helps to improve the yield of glyoxal at this temperature.

[0024] Preferably, the silver content in the zirconium-supported silver catalyst is 6-9 wt %.

[0025] By adopting the above technical solution, the present application optimizes the silver content of the zirconium-supported silver catalyst. Within the above silver content range, the addition of the zirconium-supported silver catalyst can fully increase the glyoxal yield at 400°C.

[0026] In summary, this application has the following beneficial effects: 1. The solution of the present application not only maintains good catalytic activity of the catalyst, but also makes full use of the favorable condition of high temperature environment, overcomes the defect of poor activity of silver catalyst in high temperature environment, and helps to fully improve the yield of glyoxal.

[0027] 2. The reaction temperature for catalytic synthesis of glyoxal is preferably selected in the present application. In the range of 470-560° C., the agglomeration of the lanthanum-supported silver catalyst is not serious, the catalytic activity can be fully exerted, and there are fewer side reactions, so a higher glyoxal yield can be obtained.

[0028] 3. The present application expands the types of catalysts at 400°C and adds a zirconium-supported silver catalyst. The zirconium in the zirconium-supported silver catalyst exists in the form of zirconium dioxide. Zirconium dioxide can not only reduce the agglomeration of silver, but also enable silver to have a higher catalytic activity at 400°C, which helps to increase the yield of glyoxal at this temperature. DETAILED DESCRIPTION

[0029] The present application is further described in detail below in conjunction with embodiments, preparation examples and comparative examples. The raw materials involved in the present application can all be obtained commercially.

[0030] Preparation Examples of Lanthanum-supported Silver Catalysts Preparation Example 1 is used as an example below.

[0031] Preparation Example 1 In this preparation example, the lanthanum-supported silver catalyst was prepared according to the following method: An electrolytic cell containing 5 wt% silver nitrate solution was placed in an ultrasonic generator, with a platinum sheet as the cathode and a silver block as the anode. Nano-lanthanum oxide with an average particle size of 12 nm was added to the cathode region of the electrolyte to make the lanthanum oxide concentration in the electrolyte 1%. The ultrasonic generator was maintained at 16 A / dm at 55 °C. 2 The electrolysis was carried out at a current density of , and the electrolysis products were collected and dried at 120°C for 2h. Zirconia balls were used as grinding balls, anhydrous ethanol was used as grinding medium, according to a ball-to-material ratio of 12:1, a medium-to-material ratio of 2:1, and a filling factor of 0.5. Oleic acid, which was 1% of the dry weight of the electrolysis product, was used as a ball milling aid. The milling was carried out at a ball milling speed of 200r / min. After grinding, the catalyst was washed with water and dried again to obtain a lanthanum-supported silver catalyst with an average particle size of 85nm.

[0032] As shown in Table 1, the difference between Preparation Examples 1-5 is that the concentration of lanthanum oxide in the electrolyte is different.

[0033] Table 1 Lanthanum oxide concentration in electrolyte sample Lanthanum oxide concentration in electrolyte / % Preparation Example 1 1 Preparation Example 2 3 Preparation Example 3 5 Preparation Example 4 7 Preparation Example 5 10 Preparation Examples of Zirconium-supported Silver Catalysts The following is an explanation of Preparation Example 6.

[0034] Preparation Example 6 In this preparation example, the zirconium-supported silver catalyst was prepared according to the following method: (1) dropping 14.0M ammonia water into 0.4M zirconium oxychloride solution, adjusting the pH value to 9.5 for reaction, collecting the precipitate after the reaction is complete, washing and filtering, drying at 110°C for 10h, and calcining at 550°C for 3h to obtain a zirconium carrier; (2) The zirconium carrier is immersed in a silver nitrate solution, and then the zirconium carrier is taken out and dried, and after calcination, a zirconium-supported silver catalyst with a silver content of 4 wt% is obtained.

[0035] As shown in Table 2, the difference between Preparation Examples 6-10 is that the silver content of the zirconium-supported silver catalyst is different.

[0036] Table 2 Silver content of zirconium-supported silver catalyst sample Silver content / wt% Preparation Example 6 4 Preparation Example 7 6 Preparation Example 8 7 Preparation Example 9 8 Preparation Example 10 9 Example

[0037] Examples 1-5 The following description is given by taking Example 1 as an example.

[0038] Example 1 This embodiment provides a method for synthesizing glyoxal by gas-phase catalytic oxidation of ethylene glycol, comprising the following steps: (1) The composite catalyst was calcined at 600° C. for 4 h and then granulated, and then 20-mesh particles were selected and loaded into a reactor, and preheated at 150° C. for standby use; the composite catalyst was the lanthanum-supported silver catalyst of Preparation Example 1; (2) Ethylene glycol is vaporized to obtain ethylene glycol vapor; a mixture of air, water vapor and circulating gas is preheated at 300° C., and the mixture is mixed with ethylene glycol vapor to obtain a raw gas; in this step, the oxygen-to-alcohol ratio of the raw gas is 1.

[0039] (3) The raw gas is input into a reactor containing catalyst particles, reacted at 600° C., the product is quenched, and absorbed in an absorption tower to obtain a crude glyoxal solution. The remaining tail gas is treated in an absorption tower and a washing tower, and after exhaust gas that meets emission standards is discharged, the remaining tail gas is used as circulating gas; (4) distilling, purifying and decolorizing the crude glyoxal solution to obtain glyoxal.

[0040] As shown in Table 3, the difference between Examples 1-5 mainly lies in the different preparation examples of the lanthanum-supported silver catalyst.

[0041] Table 3 Preparation example of lanthanum-supported silver catalyst Embodiment 5-9 As shown in Table 4, the difference between Examples 5-9 is that the reaction temperature in step (3) is different.

[0042] Table 4 Reaction temperature in step (3) sample Reaction temperature Example 5 600 Example 6 560 Example 7 510 Example 8 470 Example 9 400 As shown in Table 5, the difference between Examples 10-13 and Example 7 is that in step (3), the oxygen-to-alcohol ratio of the reaction is different.

[0043] Table 5 Oxygen alcohol ratio in step (3) sample Oxygen alcohol ratio Example 7 1 Example 10 1.2 Embodiment 11 1.4 Example 12 1.5 Embodiment 13 1.6 Embodiment 14 The difference between this embodiment and embodiment 9 is that the composite catalyst is formed by mixing a lanthanum-supported silver catalyst and a zirconium-supported silver catalyst in a weight ratio of 4:1, and the zirconium-supported silver catalyst is prepared according to the method of preparation example 6.

[0044] As shown in Table 6, the difference between Examples 14-18 is that the preparation examples of the zirconium-supported silver catalyst are different.

[0045] Table 6 Preparation example of zirconium-silver catalyst Comparative Example Comparative Example 1 A process for preparing glyoxal comprises the following steps: After preheating and gasifying ethylene glycol, it is mixed with air and inert gas, and the mixed gas is input into a catalytic reactor equipped with 20-mesh catalyst particles, and the reaction is carried out under the conditions of a reaction temperature of 600°C and a reaction pressure of 0.9MPa. The reaction product is chilled to 230°C with water, and then sent to an absorption tower for absorption to obtain a finished product. In this comparative example, the element composition of the catalyst is silver, phosphorus and silicon, and the weight proportions of the three elements are 99.2%, 0.3% and 0.5% respectively, and the remainder is unavoidable impurities.

[0046] Comparative Example 2 The difference between this comparative example and Example 1 is that the lanthanum-loaded silver catalyst is replaced with electrolytic silver. The preparation method of the electrolytic silver is as follows: on the basis of Preparation Example 1, lanthanum oxide is not added, and the electrolytic silver is obtained by following the same process.

[0047] Comparative Example 3 The difference between this comparative example and comparative example 1 is that the reaction temperature is 500°C.

[0048] Performance testing methods The glyoxal yield and ethylene glycol conversion rate of each embodiment and comparative example were detected and calculated. The results are shown in Table 7.

[0049] Table 7 Combining Example 1 and Comparative Example 1 and Table 7, it can be seen that the glyoxal yield measured in Example 1 is higher than that in Comparative Example 1 and Comparative Example 2, indicating that the method of the present application can more fully overcome the defect of agglomeration of the silver catalyst under high temperature conditions of 600° C., so that the catalyst can more fully exert its catalytic activity, thereby achieving full utilization of high temperature conditions and improving the yield of glyoxal.

[0050] Combining Example 1 and Comparative Example 2 with Table 7, it can be seen that after the lanthanum-loaded silver catalyst of the present application is replaced with a silver catalyst not containing lanthanum oxide, the yield of glyoxal is relatively low, indicating that the main reason why the lanthanum-loaded silver catalyst increases the yield of glyoxal is the doping of lanthanum oxide.

[0051] Combining Example 1 and Comparative Example 3 with Table 7, it can be seen that even if the reaction temperature of Comparative Example 1 is lowered to 500° C., the yield of glyoxal is still not sufficiently improved.

[0052] It can be seen from Examples 1-5 and Table 7 that when the concentration of nano-lanthanum oxide in the electrolyte is 5-10wt%, the lanthanum-supported silver catalyst prepared within this range has a significant effect on improving the yield of glyoxal.

[0053] It can be seen from Examples 5-9 and Table 7 that, in Examples 5-9, as the temperature changes, the yield of glyoxal first increases and then decreases. This is because as the temperature decreases, although the promoting effect of temperature on the reaction is weakened, the side reaction is also suppressed, so a higher glyoxal yield can be obtained in the temperature range of 470-560° C., which is slightly lower than 600° C. When the reaction temperature is 400° C., although the side reaction can be more fully suppressed, the promoting effect of temperature on the reaction is also relatively limited, so the yield of glyoxal is lower.

[0054] In conjunction with Example 7, Example 10-13 and in conjunction with Table 7, it can be seen that with the increase of oxygen alcohol ratio, the production of glyoxal first increases and then decreases, and wherein when the oxygen alcohol ratio is between 1.2-1.5, the yield of glyoxal is relatively high. The reason why the above results occur is that the rise of the oxygen alcohol ratio can promote the conversion of ethylene glycol on the one hand, and also promote the carrying out of side reactions on the other hand, so it cannot be too low or too high. Within the scope of the above-mentioned oxygen alcohol ratio, the side reaction product is relatively less, so glyoxal can obtain a higher yield. In conjunction with Example 9, Example 14-18 and in conjunction with Table 7, it can be seen that the glyoxal yield measured by Example 14-18 is all higher than Example 9, and this is because the zirconium in the zirconium-supported silver catalyst exists in the form of zirconium dioxide, and zirconium dioxide can not only reduce the agglomeration of silver, but also can make silver have a higher catalytic activity at 400 ℃, therefore improve the glyoxal yield under this temperature condition.

[0055] The above embodiments are merely explanations of the present application and are not limitations of the present application. After reading this specification, those skilled in the art may make modifications to the embodiments of the present application without any creative contribution as needed. However, as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for synthesizing glyoxal by gas phase catalytic oxidation of ethylene glycol, characterized in that: The following steps are involved: (1) calcining the composite catalyst and granulating it, then loading it into a reactor and preheating it for standby use; the composite catalyst comprises a lanthanum-loaded silver catalyst, and the lanthanum-loaded silver catalyst is a crystalline silver powder containing nano-lanthanum oxide; (2) Vaporizing ethylene glycol to obtain ethylene glycol vapor; preheating a mixture of air, water vapor and circulating gas, and mixing the mixture with ethylene glycol vapor to obtain raw gas; (3) The raw gas is input into a reactor containing catalyst particles for reaction, the product is quenched, and the crude glyoxal solution is obtained after absorption in an absorption tower. The remaining tail gas is treated in an absorption tower and a washing tower, and after the waste gas that meets the emission standards is discharged, the remaining tail gas is used as circulating gas; (4) The crude glyoxal solution is purified by distillation and decolorized to obtain glyoxal.

2. The method for synthesizing glyoxal by gas phase catalytic oxidation of ethylene glycol according to claim 1, characterized in that: The lanthanum-supported silver catalyst is prepared according to the following method: The electrolytic cell containing silver nitrate solution is placed in an ultrasonic generator, platinum is used as a cathode, silver is used as an anode, and nano-lanthanum oxide is added to the cathode region of the electrolyte. Electrolysis is carried out under heat preservation conditions, and the electrolysis product is collected. After grinding with zirconium oxide balls as grinding balls and anhydrous ethanol as a grinding medium, a lanthanum-loaded silver catalyst is obtained.

3. The method for synthesizing glyoxal by gas phase catalytic oxidation of ethylene glycol according to claim 2, characterized in that: The concentration of nano lanthanum oxide in the electrolyte is 1-10wt%.

4. The method for synthesizing glyoxal by gas phase catalytic oxidation of ethylene glycol according to claim 3, characterized in that: The concentration of nano-lanthanum oxide in the electrolyte is 5-10wt%.

5. The method for synthesizing glyoxal by gas phase catalytic oxidation of ethylene glycol according to claim 1, characterized in that: In step (3) of the method, the reaction temperature is 400-600°C.

6. The method for synthesizing glyoxal by gas phase catalytic oxidation of ethylene glycol according to claim 5, characterized in that: In step (3) of the method, the reaction temperature is 470-560°C.

7. The method for synthesizing glyoxal by gas phase catalytic oxidation of ethylene glycol according to claim 5, characterized in that: In step (3) of the method, the oxygen-alcohol ratio of the reaction is 1-1.

6.

8. The method for synthesizing glyoxal by gas phase catalytic oxidation of ethylene glycol according to claim 7, characterized in that: In step (3) of the method, the oxygen-alcohol ratio of the reaction is 1.2-1.

5.

9. The method for synthesizing glyoxal by gas phase catalytic oxidation of ethylene glycol according to claim 5, characterized in that: In step (3) of the method, the reaction temperature is 400° C., and the composite catalyst further comprises a zirconium-supported silver catalyst, which is prepared according to the following method: (1) dropping ammonia water into a zirconium oxychloride solution to react, collecting the precipitate, washing it with water, filtering it, drying it, and then calcining it to obtain a zirconium carrier; (2) The zirconium carrier is immersed in a silver nitrate solution, and then the zirconium carrier is taken out and dried, and then calcined to obtain a zirconium-supported silver catalyst.

10. The method for synthesizing glyoxal by gas phase catalytic oxidation of ethylene glycol according to claim 9, characterized in that: The silver content in the zirconium-supported silver catalyst is 6-9wt%.

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