A method for electrolysis by-product conversion based on online oxidative aromatization

Abstract

This invention belongs to the field of electrocatalysis and electrochemical engineering technology, specifically relating to a method for converting electrolytic byproducts based on online oxidative aromatization. The method described in this invention, based on the electrolytic synthesis of anisaldehyde from p-methyl anisole, utilizes a ruthenium-supported catalyst to convert the byproduct 1,4-trimethoxy-4-methyl-2,5-cyclohexadiene generated during electrolysis into pure p-methyl anisole through online oxidative aromatization. This increases the selectivity of the electrochemical production of anisaldehyde by 20%. Furthermore, the generated pure p-methyl anisole is directly returned to the electrolysis system without purification, which not only simplifies the process but also reduces costs and increases economic value.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalysis and electrochemical engineering technology, specifically relating to a method for converting electrolytic byproducts based on online oxidative aromatization. Background Technology

[0002] Electrolysis is a commonly used technique in chemical engineering, particularly in electrochemical engineering and catalytic reactions. Especially in organic synthesis, electrolysis can be used to prepare various organic compounds. Electrolysis is a common reaction for methyl anisole and can be used to synthesize compounds such as anisaldehyde. However, due to the electron-rich nature of the benzene ring in methyl anisole, byproducts such as 1,4-trimethoxy-4-methyl-2,5-cyclohexadiene are easily generated during electrolysis, reducing the selectivity of the raw materials. This not only increases process costs but also limits the industrialization prospects of this technology.

[0003] Currently, there are no literature reports in this field on a process for reusing the aforementioned byproducts generated during electrochemical oxidation. Typically, the byproducts can only be treated by incineration, which not only increases the cost of waste treatment but also reduces the selectivity of raw materials and the competitiveness of the products. Therefore, how to reuse or convert the byproduct 1,4-trimethoxy-4-methyl-2,5-cyclohexadiene into high-value-added products, and how to simplify the electrolysis process while reducing costs and improving selectivity, are urgent problems to be solved in this field. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to provide a method for converting electrolytic byproducts based on online oxidative aromatization, which greatly improves the selectivity of electrolytic products and helps to significantly reduce process costs.

[0005] To solve the above-mentioned technical problems, the present invention provides a method for converting electrolytic byproducts based on online oxidative aromatization. The method includes the steps of oxidative aromatization of the electrolytic byproduct 1,4-trimethoxy-4-methyl-2,5-cyclohexadiene in the presence of a noble metal supported catalyst, and the step of directly returning the obtained p-methyl anisole to the electrolytic system.

[0006] Specifically, in the method for converting electrolytic byproducts based on online oxidative aromatization, the precious metal includes ruthenium and / or rhodium.

[0007] Specifically, in the method for converting electrolytic byproducts based on online oxidative aromatization, the catalyst has a noble metal loading of 0.1-1 wt%, preferably 0.2-0.5 wt%.

[0008] Preferably, the catalyst has an average particle size of 5-10 micrometers;

[0009] Preferably, the catalyst has a specific surface area of ​​100-200 m². 2 / g.

[0010] Specifically, in the method for converting electrolytic byproducts based on online oxidative aromatization, the support for the noble metal supported catalyst includes a weakly basic support.

[0011] Preferably, the carrier comprises nanospheres or nanoparticles of a weakly alkaline carrier;

[0012] Preferably, the carrier comprises at least one of alumina, silica gel, or activated carbon nanospheres or nanoparticles;

[0013] Preferably, the diameter of the carrier is 5-100 nm, more preferably 10-40 nm.

[0014] Specifically, the method for converting electrolytic byproducts based on online oxidative aromatization has the following characteristics in the oxidative aromatization reaction:

[0015] The oxidative aromatization reaction is performed at a temperature of 100-150°C; and / or,

[0016] The reaction pressure for the oxidative aromatization reaction is 1-5 MPa; and / or,

[0017] The reaction time for the oxidative aromatization reaction is 1-5 hours.

[0018] Specifically, the method for converting electrolytic byproducts based on online oxidative aromatization includes the step of passing the 1,4-trimethoxy-4-methyl-2,5-cyclohexadiene into a fixed-bed reactor containing the ruthenium-supported catalyst.

[0019] Specifically, in the method for converting electrolytic byproducts based on online oxidative aromatization, the fixed-bed reactor is located between the light-weight removal tower and the electrolytic concentration tank in the electrolysis process.

[0020] Specifically, the method for converting electrolytic byproducts based on online oxidative aromatization further includes the steps of collecting the products of the oxidative aromatization reaction and separating p-methyl anisole.

[0021] Preferably, the separation apparatus for the separation step includes a distillation column and a condenser;

[0022] Preferably, the temperature of the distillation column is 100-150℃;

[0023] Preferably, the temperature of the condenser is 0-20°C.

[0024] Specifically, the method for converting electrolytic byproducts based on online oxidative aromatization includes an electrolytic system that is the same as the electrolytic system used in the process of synthesizing anisaldehyde from p-methyl anisole.

[0025] The present invention also discloses a process for the electrolytic synthesis of anisaldehyde based on p-methyl anisole, including a step of converting electrolytic byproducts according to the method.

[0026] Specifically, the process for synthesizing anisaldehyde by electrolysis of p-methyl anisole includes an anode, a cathode, and an electrolyte in its electrolysis system; wherein,

[0027] The electrolyte includes p-methyl anisole, potassium-containing inorganic salts, water, and alcohol solvents.

[0028] The process for synthesizing anisaldehyde based on the electrolytic reaction of p-methyl anisole involves passing direct current through the anode and cathode, and obtaining the target product after reaching the desired reaction conversion rate.

[0029] The present invention describes a method for converting electrolytic byproducts based on online oxidative aromatization. Building upon the process of electrolytically synthesizing anisaldehyde from p-methyl anisole, this method utilizes a catalyst supported by noble metals such as ruthenium or rhodium. Through online oxidative aromatization, the byproduct 1,4-trimethoxy-4-methyl-2,5-cyclohexadiene generated during electrolysis is converted into pure p-methyl anisole, thereby increasing the selectivity of the electrochemical production of anisaldehyde by 20%. Furthermore, the generated pure p-methyl anisole is directly returned to the electrolysis system without purification, which not only simplifies the process but also reduces costs and increases economic value.

[0030] The present invention describes a method for converting electrolytic byproducts based on online oxidative aromatization. This method converts 1,4-trimethoxy-4-methyl-2,5-cyclohexadiene, a byproduct generated during electrolysis, into pure p-methyl anisole through online ruthenium / alumina nanosphere fixed-bed catalysis. This essentially achieves complete utilization of the original external discharge stream, greatly improves the selectivity of anisaldehyde generation during electrolysis, and significantly reduces costs. This method does not require significant changes to the process flow; it only requires adding a fixed-bed reactor between the light-weight removal tower and the electrolytic concentration tank. The modification is simple and generates high economic value. Attached Figure Description

[0031] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...

[0032] Figure 1 This is a flow chart of the electrolytic process for p-methyl anisole.

[0033] Figure 2 This is a flowchart of the online oxidative aromatization reaction;

[0034] Figure 3 This is a schematic diagram illustrating the principle of the online oxidative aromatization reaction described in this invention. Detailed Implementation

[0035] To address the problem of numerous byproducts affecting product selectivity in electrolysis processes, this application provides a method for converting electrolysis byproducts based on online oxidative aromatization. The method includes the steps of oxidative aromatization of the electrolysis byproduct 1,4-trimethoxy-4-methyl-2,5-cyclohexadiene in the presence of a noble metal-supported catalyst, and the step of directly returning the resulting p-methyl anisole to the electrolysis system.

[0036] In some feasible embodiments, the precious metal includes ruthenium and / or rhodium.

[0037] In some feasible embodiments, the loading of the noble metal supported catalyst is 0.1-1 wt%, preferably 0.2-0.5 wt%. For example, the loading of noble metals such as ruthenium and / or rhodium in the catalyst can be adjusted to 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 wt%, or any range between the above values.

[0038] In some feasible embodiments, the ruthenium and / or rhodium-supported catalyst has a particle size of 5-10 micrometers and a specific surface area of ​​100-200 m². 2 / g. For example, the particle size of the supported catalyst is controlled to be 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10 micrometers, or any range between the above values. For example, the specific surface area of ​​the supported catalyst is controlled to be 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200 m². 2 / g, or any range between the above values.

[0039] In some feasible embodiments, the support for the ruthenium and / or rhodium supported catalyst comprises a weakly basic support, such as nanospheres or nanoparticles of a weakly basic support. As an exemplary embodiment, the support includes nanospheres or nanoparticles of alumina, silica gel, or activated carbon, etc.

[0040] In some feasible embodiments, the diameter of the carrier (nanospheres or nanoparticles) is 5-100 nm, preferably 10-40 nm. For example, the diameter of the carrier can be selected as 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100 nm, or any range between the above values.

[0041] In the following embodiments of the present invention, the preparation method of the noble metal supported catalyst, such as ruthenium supported catalyst or rhodium supported catalyst, can be carried out by conventional methods in the art. Those skilled in the art can prepare catalyst products with the corresponding loading amount by using conventional technical means.

[0042] As an exemplary embodiment, a method for preparing supported catalysts in this art can be an impregnation method: impregnating an alumina support with a ruthenium chloride solution, followed by high-temperature sintering to obtain the catalyst. A suitable solvent ratio is selected for impregnation based on the loading amount, and the high-temperature sintering temperature within the conventional range does not affect the catalyst's performance.

[0043] As an exemplary embodiment, a method for preparing the supported catalyst in this field can be a co-precipitation method: mixing ruthenium / rhodium salt and alumina salt solutions, adjusting the pH value, and co-precipitating ruthenium and alumina to obtain the catalyst.

[0044] As an exemplary embodiment, a method for preparing supported catalysts in this field can be the sol-gel method: ruthenium / rhodium and alumina precursors are formed into a sol in a solvent, the solvent is then heated to obtain a gel, and the catalyst is obtained after high-temperature calcination.

[0045] In some feasible embodiments, the oxidative aromatization reaction is carried out at a temperature of 100-150°C, a reaction pressure of 1-5 MPa, and a reaction time of 1-5 hours.

[0046] As an exemplary embodiment, the temperature of the aromatization reaction is adjusted to 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150°C, or any range between the above values.

[0047] As an exemplary embodiment, the reaction pressure of the aromatization reaction is adjusted to 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 MPa, or any range between the above values.

[0048] As an exemplary embodiment, the reaction time of the aromatization reaction is adjusted to 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 hours, or any range between the above values.

[0049] In some feasible embodiments, the oxidative aromatization reaction step includes passing the 1,4-trimethoxy-4-methyl-2,5-cyclohexadiene into a fixed-bed reactor containing the noble metal supported catalyst.

[0050] In some feasible embodiments, the fixed-bed reactor is located between the light-weight removal tower and the electrolytic concentration tank of the electrolysis process.

[0051] In some feasible embodiments, the fixed-bed reactor has a length-to-diameter ratio of (5-8):1, which can be adapted to the model of the fixed-bed reactor.

[0052] In some feasible embodiments, the fixed-bed reaction uses a sandwich structure for the loaded catalyst. For example, from top to bottom, it consists of 2-4 mm hard alumina microspheres (5-15% of bed height), 0.3-0.8 mm hard quartz sand (5-15% of bed height), a noble metal supported catalyst (50-70% of bed height), 0.3-0.8 mm hard quartz sand (5-15% of bed height), and 2-4 mm hard alumina microspheres (5-15% of bed height).

[0053] In some feasible embodiments, the electrolysis system includes a process for the electrolytic synthesis of anisaldehyde from p-methyl anisole.

[0054] Secondly, the present invention also discloses a process for the electrolytic synthesis of anisaldehyde based on p-methyl anisole, including a step of converting electrolytic byproducts according to the method.

[0055] like Figure 1 The flowchart described is a schematic diagram of the process for the electrolytic synthesis of anisaldehyde from p-methyl anisole. The process involves electrolyzing p-methyl anisole and methanol in the presence of an anode, a cathode, and an electrolyte. The electrolysis products are collected, and the light components / electrolytes are removed by a light component removal tower. After hydrolysis, anisaldehyde can be prepared.

[0056] like Figure 2-3 The flowchart and schematic diagram shown indicate that the present invention is... Figure 1 Based on the process of synthesizing anisaldehyde by electrolysis of p-methyl anisole, a fixed-bed reactor 2 is set up between the light-weight removal tower 1 and the electrolysis concentration tank 3 of the electrolysis unit to convert the by-products generated in the electrolysis step into raw materials through online oxidative aromatization. In this process, in the presence of a ruthenium and / or rhodium supported catalyst, the electrolysis by-product 1,4-trimethoxy-4-methyl-2,5-cyclohexadiene undergoes an oxidative aromatization reaction, and the pure p-methyl anisole obtained from the reaction is directly returned to the electrolysis system without purification.

[0057] The preparation method provided by the present invention will be further described in detail below through examples, but the present invention is not limited thereto.

[0058] Example

[0059] like Figure 1-2The process flow diagram shown in this embodiment illustrates the process for the electrolytic synthesis of anisaldehyde from p-methyl anisole. The electrolytic system includes an anode, a cathode, and an electrolyte. Specifically, 1 wt% potassium fluoride is added to a methanol solution, along with p-methyl anisole raw material and water to form the electrolyte raw material solution. Direct current is passed through the anode and cathode, and the target product is obtained after the reaction conversion rate is reached.

[0060] In order to improve reaction efficiency by converting the byproduct 1,4-trimethoxy-4-methyl-2,5-cyclohexadiene generated during electrolysis into p-methyl anisole feedstock, the method for converting electrolysis byproducts into feedstocks by online oxidative aromatization described in this embodiment is to set up a fixed-bed reactor 2 between the light removal tower 1 and the electrolysis concentration tank 3 of the electrolysis unit and fill it with the noble metal supported catalyst.

[0061] As an example, the fixed-bed reactor has an aspect ratio of 6:1, and the specific filling structure is a sandwich structure, consisting of 3mm hard alumina spheres (10% of the bed height), 0.5mm hard quartz sand (10% of the bed height), precious metal supported catalyst (60% of the bed height), 0.5mm hard quartz sand (10% of the bed height), and 3mm hard alumina spheres (10% of the bed height) from top to bottom.

[0062] In various embodiments of the present invention, ruthenium or rhodium with different loadings are used as active ingredients supported on appropriate supports with different particle sizes as catalysts to form catalysts with different particle sizes and specific surface areas.

[0063] As an exemplary embodiment, in the following examples of the present invention, the supported catalyst is prepared by the following method: a selected nano-alumina support is impregnated with a ruthenium chloride solution at a selected loading amount, and the catalyst is obtained by high-temperature sintering at 450°C. The rhodium-supported catalyst is prepared using the same method.

[0064] The byproduct 1,4-trimethoxy-4-methyl-2,5-cyclohexadiene generated during electrolysis is fed into a fixed-bed reactor containing a catalyst for online oxidative aromatization. The oxidative aromatization reaction is carried out under different reaction temperatures and pressures.

[0065] After the reaction is complete, the pure p-methyl anisole product is returned directly to the electrolysis system without further purification to continue participating in the electrolysis reaction.

[0066] The process parameters involved in the following embodiments of the present invention are detailed in Table 1 below.

[0067] Table 1 Process Parameters

[0068]

[0069] Comparative Example 1

[0070] The process and apparatus for preparing anisaldehyde by electrolysis of p-methyl anisole described in this comparative example are the same as those in Example 1, except that the fixed-bed reactor is not added and the oxidative aromatization reaction is not required.

[0071] Comparative Example 2

[0072] The method for converting electrolytic byproducts into raw materials through online oxidative aromatization described in this embodiment is the same as in Embodiment 1, except that the catalyst loading active element is selected as metallic nickel, and the specific loading method is the ruthenium loading method in Embodiment 1.

[0073] Experimental Example

[0074] This experimental example is based on the quantitative testing of the electrolytic selectivity and current efficiency of the methyl anisole electrolysis system in the foregoing examples.

[0075] The purity of anisaldehyde was determined by gas chromatography (GC), and the yield of anisaldehyde was calculated as follows: yield = actual yield × purity / theoretical yield × 100%.

[0076] Gas chromatograph instrument model: Agilent 8890; Injector: Autosampler; Detector: FID detector; Column: HP-VOC (30m×0.25mm×0.25μm); Temperature program: 50℃ for 5 minutes, increase to 300℃ at 10℃ / min, and hold for 10 minutes.

[0077] Electrolysis efficiency is also current efficiency. It is determined by Faraday's second law It = nZF, which shows the percentage of theoretically consumed electricity to the actual consumed electricity, thus yielding the electrolysis efficiency.

[0078] The electrolytic performance results of the various embodiments and comparative examples tested in this experiment are shown in Table 2 below.

[0079] Table 2 Electrolysis Reaction Performance Results

[0080] serial number Product selectivity Current efficiency Example 1 97％ 95％ Example 2 94％ 93％ Example 3 95％ 91％ Example 4 92％ 90％ Example 5 94％ 92％ Example 6 95％ 90％ Comparative Example 1 65％ 70％ Comparative Example 2 73％ 75％

[0081] The present invention describes a method for converting electrolytic byproducts based on online oxidative aromatization. Building upon the process of electrolytically synthesizing anisaldehyde from p-methyl anisole, this method utilizes a catalyst supported by noble metals such as ruthenium or rhodium. Through online oxidative aromatization, the byproduct 1,4-trimethoxy-4-methyl-2,5-cyclohexadiene generated during electrolysis is converted into pure p-methyl anisole, thereby further improving the selectivity of the electrochemical production of anisaldehyde by more than 20% and significantly enhancing the current efficiency.

[0082] In summary, by using ruthenium-supported alumina microspheres as a catalyst, this invention not only efficiently generates p-methyl anisole raw material, which can be directly returned to the electrolysis system without purification, thereby improving the selectivity of electrochemical production of anisaldehyde and solving the problem of low raw material selectivity; at the same time, by converting the byproduct 1,4-trimethoxy-4-methyl-2,5-cyclohexadiene generated during electrolysis into pure p-methyl anisole, the entire waste stream is reused, thereby reducing costs and increasing economic value.

[0083] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for converting electrolytic byproducts based on online oxidative aromatization, characterized in that, The method includes the steps of oxidative aromatization of the electrolysis byproduct 1,4-trimethoxy-4-methyl-2,5-cyclohexadiene in the presence of a noble metal supported catalyst, and the step of directly returning the resulting p-methyl anisole to the electrolysis system. The precious metal is ruthenium and / or rhodium.

2. The method for converting electrolytic byproducts based on online oxidative aromatization according to claim 1, characterized in that, The catalyst has a noble metal loading of 0.1-1 wt%.

3. The method for converting electrolytic byproducts based on online oxidative aromatization according to claim 2, characterized in that, The catalyst has a noble metal loading of 0.2-0.5 wt%.

4. The method for converting electrolytic byproducts based on online oxidative aromatization according to claim 2, characterized in that, The catalyst has an average particle size of 5-10 micrometers.

5. The method for converting electrolytic byproducts based on online oxidative aromatization according to claim 2, characterized in that, The catalyst has a specific surface area of ​​100-200 m². 2 / g.

6. The method for converting electrolytic byproducts based on online oxidative aromatization according to claim 1, characterized in that, The support for the noble metal supported catalyst includes a weakly basic support.

7. The method for converting electrolytic byproducts based on online oxidative aromatization according to claim 6, characterized in that, The carrier includes nanospheres or nanoparticles of a weakly alkaline carrier.

8. The method for converting electrolytic byproducts based on online oxidative aromatization according to claim 6, characterized in that, The carrier includes at least one of alumina, silica gel, or activated carbon nanospheres or nanoparticles.

9. The method for converting electrolytic byproducts based on online oxidative aromatization according to claim 6, characterized in that, The diameter of the carrier is 5-100 nm.

10. The method for converting electrolytic byproducts based on online oxidative aromatization according to claim 6, characterized in that, The diameter of the carrier is 10-40 nm.

11. The method for converting electrolytic byproducts based on online oxidative aromatization according to claim 1, characterized in that, The oxidative aromatization reaction has the following characteristics: The oxidative aromatization reaction is performed at a temperature of 100-150°C; and / or, The reaction pressure for the oxidative aromatization reaction is 1-5 MPa; and / or, The reaction time for the oxidative aromatization reaction is 1-5 hours.

12. The method for converting electrolytic byproducts based on online oxidative aromatization according to claim 1, characterized in that, The oxidative aromatization reaction step includes passing the 1,4-trimethoxy-4-methyl-2,5-cyclohexadiene into a fixed-bed reactor containing the ruthenium-supported catalyst.

13. The method for converting electrolytic byproducts based on online oxidative aromatization according to claim 12, characterized in that, The fixed-bed reactor is located between the light-weight removal tower and the electrolytic concentration tank in the electrolysis process.

14. The method for converting electrolytic byproducts based on online oxidative aromatization according to any one of claims 1-13, characterized in that, The method further includes the steps of collecting the product of the oxidative aromatization reaction and separating p-methyl anisole.

15. The method for converting electrolytic byproducts based on online oxidative aromatization according to any one of claims 1-13, characterized in that, The electrolysis system includes the electrolysis system used in the process of synthesizing anisaldehyde by electrolysis of p-methyl anisole.

16. A process for the electrolytic synthesis of anisaldehyde based on p-methyl anisole, characterized in that, Includes the step of converting electrolytic byproducts according to any one of claims 1-15.

17. The process for synthesizing anisaldehyde based on the electrolytic electrolysis of p-methyl anisole according to claim 16, characterized in that, The electrolysis system of the electrolysis process includes an anode, a cathode, and an electrolyte; wherein the electrolyte includes p-methyl anisole, potassium-containing inorganic salts, and alcohol solvents.

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