Method for green, mild and efficient synthesis of methylamine hydrochloride based on photocatalysis
The synthesis of methylamine hydrochloride under anaerobic conditions via Pd/TiO2 photocatalyst in a single step solves the problems of high temperature, high pressure, and the use of toxic substances in existing technologies, achieving a green and efficient synthesis process that reduces energy consumption and environmental pollution.
Patent Information
- Application Number
- CN202511078377.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-01
- Publication Date
- 2025-11-21
AI Technical Summary
The synthesis of methylamine hydrochlorides in existing technologies requires high temperature, high pressure and toxic reactants, resulting in an environmentally unfriendly and complex synthesis process, and a lack of green and efficient synthesis methods.
Methylamine hydrochloride was synthesized in one step via photocatalytic reaction using a Pd/TiO2 photocatalyst under anaerobic conditions. Methanol and ammonium chloride were used as raw materials, and CN coupling reaction was carried out using a TiO2 photocatalyst synergistically modified with Pd nanoparticles and oxygen vacancies.
This method enables the synthesis of methylamine hydrochlorides under mild reaction conditions, with simple operation and an environmentally friendly approach. It avoids the use of high temperature, high pressure and toxic substances, reduces energy consumption and environmental pollution risks, and improves synthesis efficiency.
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Figure CN120987777A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of photocatalytic synthesis, in particular to a method for green, mild and efficient synthesis of methylamine hydrochloride based on photocatalysis. BACKGROUND
[0002] Methylamine hydrochloride is an important chemical substance, which is widely used as a raw material or key intermediate in the synthesis of drugs, pesticides and fungicides. The current industrial synthesis route is as follows: (1) synthesis of methylamine from CH3OH and NH3 on a catalyst at high temperature (> 300℃); (2) HCl acidification. However, the typical method requires complex conditions and toxic reactants, which is not conducive to sustainable production. Therefore, it is of great significance to develop a green, efficient and mild method for synthesizing methylamine hydrochloride to promote sustainable chemical production and reduce the impact on the environment.
[0003] Photocatalytic synthesis technology has the advantages of mild reaction conditions, simple operation and environmental friendliness, and is an ideal green synthesis method. Reductive amination of alcohols is one of the typical C-N coupling reactions, which uses economically viable alcohols as substrates, produces water as the only byproduct through alcohol dehydrogenation and subsequent reductive amination, avoiding the use and production of toxic substances, thus meeting the principles of green chemistry. In the process of reductive amination, methanol not only serves as a C source for methylation, but also provides hydrogen as a protonating agent for subsequent reductive amination. This process can fully utilize the electrons and holes generated by the semiconductor in the photocatalytic process, achieving solar fuel conversion while selectively converting organic compounds into valuable chemicals. However, there are still few studies on combining reductive amination strategies with photocatalytic systems, especially for the synthesis of methylamine hydrochloride by photocatalysis. Therefore, it is of great significance to construct a suitable photocatalytic C-N coupling reaction system for efficient production of methylamine hydrochloride. SUMMARY
[0004] The technical problem to be solved by the present application is to provide a method for green, mild and efficient synthesis of methylamine hydrochloride based on photocatalysis, to realize a synthesis process with mild reaction conditions, simple operation and environmental friendliness, and to open up a new and sustainable technical path for the synthesis of methylamine hydrochloride.
[0005] To achieve the above purpose, the present application adopts the following technical solutions:
[0006] The application finds, through literature research, that TiO2-based photocatalysts have good application prospects in photocatalytic reactions due to their unique structure and excellent photocatalytic performance, and are a suitable choice. In addition, research shows that the loading of noble metals and vacancies can promote the progress of photocatalytic reactions. Therefore, the application uses Pd nanoparticles and oxygen vacancies to modify titanium dioxide (Pd / TiO2) as a high-efficiency photocatalyst, and verifies its key role in the synthesis of methylamine hydrochloride through experiments. The photocatalyst can effectively improve the reaction efficiency and realize the efficient synthesis of methylamine hydrochloride.
[0007] A method for mildly, greenly and efficiently synthesizing methylamine hydrochloride based on photocatalysis is provided, which uses methanol and ammonium chloride as raw materials, and performs a photocatalytic reaction under anaerobic conditions by using a Pd / TiO2 photocatalyst to synically synthesize a target methylamine hydrochloride product. The method specifically includes the following steps: dispersing the Pd / TiO2 photocatalyst and ammonium chloride in a methanol solution to obtain a suspension, purging the reactor with argon to remove residual oxygen, and filling the reactor with argon. The suspension is irradiated under a xenon lamp to obtain the methylamine hydrochloride.
[0008] In the above technical solution, further, the mass ratio of Pd to TiO2 in the Pd / TiO2 photocatalyst is not more than 1.5wt%.
[0009] Further, the Pd / TiO2 photocatalyst is prepared by a hydrogen reduction method, that is, TiO2 is mixed with a Pd precursor solution, dried, and then calcined under a hydrogen-containing protective atmosphere to obtain the Pd / TiO2 photocatalyst. The Pd precursor solution is a [PdCl4(NH3)2]2 complex solution formed by dissolving palladium chloride in dilute hydrochloric acid and ammonia solution. - More preferably, the TiO2 is P25 type, and the calcination is calcination at 400℃ for 2h under a mixed gas of H2 and Ar.
[0010] Further, the amount ratio of ammonium chloride to methanol solution is not more than 15mmol:30mL.
[0011] Further, the temperature of the reactor is controlled to be 60-100℃.
[0012] Further, the irradiation time is 1-24h.
[0013] Further, the methylamine hydrochloride is monomethylamine hydrochloride, dimethylamine hydrochloride, or trimethylamine hydrochloride.
[0014] The application has the following beneficial effects:
[0015] 1. The photocatalytic reaction system involved in the application has mild reaction conditions and a simple operation process, and does not require harsh high temperature and high pressure conditions, thereby greatly reducing energy consumption and equipment requirements and improving operation safety.
[0016] 2. The present application uses methanol and ammonium chloride as carbon and nitrogen sources, avoiding the use of highly toxic, flammable and explosive or strongly corrosive raw materials, reducing environmental and safety risks from the source.
[0017] 3. The present application will not produce a large amount of harmful by-products during the reaction process, is environmentally friendly, can effectively reduce the environmental pollution risk in the production process, is a green and efficient photocatalytic reaction system, and has a broad application prospect. BRIEF DESCRIPTION OF DRAWINGS
[0018] Figure 1 HRTEM image and corresponding EDS image of 1wt% Pd / TiO2 photocatalyst prepared for Example 1 of the present application;
[0019] Figure 2 Effect of different catalyst preparation methods on the reactivity in Example 2 of the present application;
[0020] Figure 3 NMR hydrogen spectrum of the liquid product after 10 mmol of ammonium chloride reacted for 4h in Example 3 of the present application;
[0021] Figure 4 Effect of different amounts of ammonium chloride on the reactivity in Example 3 of the present application;
[0022] Figure 5 Effect of different system temperatures on the reactivity in Example 4 of the present application;
[0023] Figure 6 Effect of light or no light on the reactivity in Example 5 of the present application;
[0024] Figure 7 Product change over time in the reaction of Example 6 of the present application. DETAILED DESCRIPTION
[0025] The technical solutions of the present application will be further described in detail below through the drawings and examples. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure.
[0026] Example 1:
[0027] Pd / TiO2 photocatalyst was prepared by hydrogen reduction method, and the specific steps were as follows:
[0028] S1, 500mg of P25 type TiO2 was dispersed in 30mL of deionized water, and ultrasonic dispersion was formed into a uniform suspension.
[0029] S2, [PdCl4(NH3)2]2 was added to the above suspension -Solution, impregnation stirring 2h.
[0030] S3, the obtained solution was placed in an oven at 80℃ to dry to complete dehydration, obtaining a precursor powder.
[0031] S4, the precursor powder was placed in a tube furnace, calcined at 400℃ for 2h under 10% H2 / Ar mixed gas, obtaining a photocatalyst "Pd / TiO2".
[0032] In S2, the mass ratio of Pd to TiO2 is 0, 0.5wt%, 1wt%, 1.5wt%.
[0033] Example 2:
[0034] The Pd / TiO2 photocatalyst was prepared by NaBH4 reduction method, the specific steps are as follows:
[0035] S1, 100mg P25 type TiO2 was dispersed in 100mL deionized water, ultrasonic dispersion to form a uniform suspension.
[0036] S2, [PdCl4(NH3)2]2 solution (mass ratio of Pd to TiO2 is 1wt%) was added to the above suspension. - Solution, impregnation stirring 0.5h.
[0037] S3, 10mg NaBH4 was dissolved in 10mL deionized water, and the NaBH4 solution was added dropwise to the above S2 solution, stirring for 2h.
[0038] S4, the obtained solution was centrifuged and washed with deionized water, and placed in an oven at 80℃ to dry to complete dehydration, obtaining a photocatalyst "Pd / TiO2".
[0039] Example 3:
[0040] The method for efficiently photocatalytic synthesis of methylamine hydrochloride according to the present application, the steps and performance evaluation method are as follows:
[0041] S1, 20mg of 1wt% Pd / TiO2 photocatalyst and a certain mass of ammonium chloride were dispersed in 30mL methanol solution,
[0042] S2, the reactor was purged with argon for 10 minutes to remove residual oxygen, and 1MPa argon was filled in the reactor, and the reaction system temperature was maintained at 100℃, and irradiated under a 300W xenon lamp for 4h.
[0043] S3, after the reaction, GC-2014C gas chromatograph was used to analyze the gaseous products, and Bruker Ascend 400MHz nuclear magnetic resonance spectrometer was used to analyze the liquid products with dimethyl sulfoxide-d6 as deuterated reagent.
[0044] The amount of the ammonium chloride is 0mmol, 2.5mmol, 5mmol, 10mmol or 15mmol.
[0045] Example 4:
[0046] The method for efficiently photocatalyzing synthesis of methylamine hydrochloride, the steps and the performance evaluation method are as follows:
[0047] S1, 20mg of 1wt% Pd / TiO2 and 10mmol of ammonium chloride are dispersed in 30mL of methanol solution.
[0048] S2, the reactor is purged with argon for 10 minutes to remove residual oxygen, and 1MPa of argon is filled in the reactor, and irradiation is carried out under 300W xenon lamp for 4h.
[0049] S3, after the reaction is completed, GC-2014C gas chromatograph is used to analyze gaseous products, and Bruker Ascend 400MHz nuclear magnetic resonance spectrometer is used to analyze liquid products with dimethyl sulfoxide-d6 as deuterated reagent.
[0050] The temperature of the reaction system is 20℃, 50℃, 80℃ or 100℃.
[0051] Example 5:
[0052] The method for efficiently photocatalyzing synthesis of methylamine hydrochloride, the process and the performance evaluation method are as follows:
[0053] S1, 20mg of 1wt% Pd / TiO2 and 10mmol of ammonium chloride are dispersed in 30mL of methanol solution.
[0054] S2, the reactor is purged with argon for 10 minutes to remove residual oxygen, and 1MPa of argon is filled in the reactor, and the reaction system is maintained at 100℃.
[0055] S3, after the reaction is completed, GC-2014C gas chromatograph is used to analyze gaseous products, and Bruker Ascend 400MHz nuclear magnetic resonance spectrometer is used to analyze liquid products with dimethyl sulfoxide-d6 as deuterated reagent.
[0056] The reaction is carried out in a system with light or without light.
[0057] Example 6:
[0058] The method for efficiently photocatalyzing synthesis of methylamine hydrochloride, the steps and the performance evaluation method are as follows:
[0059] S1, 20 mg of 1wt% Pd / TiO2 and 10 mmol of ammonium chloride were dispersed in 30 mL of methanol solution.
[0060] S2, the reactor was purged with argon for 10 minutes to remove residual oxygen, and the reactor was filled with 1 MPa of argon, and the reaction system was maintained at 100 DEG C, and irradiated under a 300 W xenon lamp.
[0061] S3, after the reaction, the gaseous product was analyzed by GC-2014C gas chromatograph, and the liquid product was analyzed by Bruker Ascend 400MHz nuclear magnetic resonance spectrometer with dimethyl sulfoxide-d6 as deuterated reagent.
[0062] Among them, the light irradiation time is 1h, 2h, 4h, 8h, 12h, 16h, 24h.
[0063] The HRTEM image and the corresponding EDS image of the 1wt% Pd / TiO2 photocatalyst prepared in example 1 of the present application are shown in Figure 1 It can be seen that Pd is successfully introduced, which indicates that Pd is loaded on the surface of TiO2 in the form of nanoparticles.
[0064] The activity comparison of the 1wt% Pd / TiO2 photocatalyst prepared in example 1 and example 2 of the present application is shown in Figure 2 As shown in the figure (all using the method of example 3, ammonium chloride is 10 mmol), it can be seen that the catalyst prepared by hydrogen reduction method in example 1 has the best activity.
[0065] The nuclear magnetic resonance spectrum of the product of 10 mmol of ammonium chloride reacted for 4h in example 3 of the present application is shown in Figure 3 It can be seen that the product is mainly monomethylamine hydrochloride, dimethylamine hydrochloride and trimethylamine hydrochloride, which indicates that the C-N coupling reaction occurs successfully.
[0066] The influence of different amounts of ammonium chloride on the reaction activity based on the photocatalyst obtained in example 1 of the present application is shown in Figure 4 It can be seen that the reaction activity is the best when 10 mmol of ammonium chloride is added.
[0067] The influence of different system temperatures on the reaction activity based on the photocatalyst obtained in example 1 of the present application is shown in Figure 5 It can be seen that the reaction activity is the best at 100 DEG C.
[0068] The influence of light or no light on the reaction activity based on the photocatalyst obtained in example 1 of the present application is shown in Figure 6 It can be seen that the reaction can only occur under the condition of adding light, which indicates the importance of light irradiation.
[0069] The change of the product of the reaction of Example 6 based on the photocatalyst obtained in Example 1 with time is shown in Table 2. Figure 7 As shown in Table 2, it can be seen that the thermodynamically stable product trimethylamine hydrochloride is gradually produced as the reaction time is prolonged.
[0070] The above-described examples are only some of the preferred embodiments of the present application, and are not intended to limit the present application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application. Therefore, all technical solutions obtained by equivalent replacement or equivalent transformation fall within the scope of the present application.
Claims
1. A method for the mild, green, and efficient synthesis of methylamine hydrochlorides based on photocatalysis, characterized in that, The process includes the following steps: dispersing Pd / TiO2 photocatalyst and ammonium chloride in a methanol solution to obtain a suspension; purging the reactor with argon gas to remove residual oxygen; introducing argon gas into the reactor; and irradiating the suspension under a xenon lamp to obtain methylamine hydrochloride.
2. The method for the mild, green, and efficient synthesis of methylamine hydrochlorides based on photocatalysis according to claim 1, characterized in that, The mass ratio of Pd to TiO2 in the Pd / TiO2 photocatalyst is no more than 1.5 wt%.
3. The method for the mild, green, and efficient synthesis of methylamine hydrochlorides based on photocatalysis according to claim 1, characterized in that, The Pd / TiO2 photocatalyst was prepared by hydrogen reduction, which involves mixing TiO2 with a Pd precursor solution, drying the mixture, and then calcining it under a hydrogen-containing protective atmosphere. The Pd precursor solution was [PdCl4(NH3)2]2 formed by dissolving palladium chloride in dilute hydrochloric acid and ammonia solution. - Complex solution.
4. The method for the mild, green, and efficient synthesis of methylamine hydrochlorides based on photocatalysis according to claim 1, characterized in that, The ratio of ammonium chloride to methanol solution should not exceed 15 mmol: 30 mL.
5. The method for the mild, green, and efficient synthesis of methylamine hydrochlorides based on photocatalysis according to claim 1, characterized in that, The temperature of the reactor is controlled at 60-100℃.
6. The method for the mild, green, and efficient synthesis of methylamine hydrochlorides based on photocatalysis according to claim 1, characterized in that, The irradiation time is 1-24 hours.
7. The method for the mild, green, and efficient synthesis of methylamine hydrochlorides based on photocatalysis according to claim 1, characterized in that, The methylamine hydrochloride is monomethylamine hydrochloride, dimethylamine hydrochloride, or trimethylamine hydrochloride.