Method for one-step synthesis of formamide by photocatalytic coupling of methanol and ammonia

Abstract

The invention belongs to the field of formamide preparation, and particularly relates to a method for one-step synthesis of formamide by photocatalytic coupling of methanol and ammonia, and the method comprises the following steps: mixing methanol, ammonia water, water and a photocatalyst in a closed reaction kettle, and carrying out a photocatalytic reaction to prepare the formamide, the photocatalyst is a nanoscale semiconductor carrier loaded with a cocatalyst; the cocatalyst is selected from one or more of MoS2, Ni2P, Pt, Pd, Au, Ag and Rh; the nano-scale semiconductor carrier is selected from one or more of CdS, ZnIn2S4, TiO2, C3N4, SrTiO3 and CeO2, and the nano-scale semiconductor carrier is selected from one or more of CdS, ZnIn2S4, TiO2, C3N4, SrTiO3 According to the method, the cheap ammonia water and methanol are directly used as reactants to catalyze the reaction under mild illumination to obtain the formamide, the reaction cost is low, the requirement on reaction equipment is low, the operation is simple and convenient, the reaction environment is green and clean, a toxic catalyst is not needed, and the catalyst can be recycled.

Description

Technical Field

[0001] This invention belongs to the field of formamide preparation, and particularly relates to a method for one-step synthesis of formamide by photocatalytic coupling of methanol and ammonia. Background Technology

[0002] Developing green and sustainable solar energy utilization is of great significance to addressing the increasingly serious energy and environmental problems. Among numerous solar energy conversion technologies, direct solar-chemical energy conversion technology is considered one of the important development directions for future sustainable energy and plays a vital role in the development of future green chemical technologies.

[0003] As an important class of industrial chemicals, formamide is widely used in many important fields such as the fiber industry, agriculture, and medicine. The demand for formamide is growing rapidly year by year, and its market prospects are very broad. Currently, the industrial synthesis of formamide mainly employs thermochemical methods, while some methods utilize electrocatalysis. However, methods for synthesizing formamide through photocatalysis have not yet been reported. The main reported methods for formamide synthesis are as follows:

[0004] The first method involves using sodium methoxide as a catalyst and carbon monoxide and ammonia to synthesize formamide in one step under conditions of 80-100℃ and 10-30MPa (German Patent Ger.Pat.1, 142, 163).

[0005] The second method involves synthesizing sodium formate using sodium hydroxide and carbon monoxide at a temperature of 150℃ and a pressure of 18-20 MPa, followed by the reaction of sodium formate with sulfuric acid to synthesize formic acid. Formic acid is then further reacted with methanol under the catalysis of sulfuric acid to obtain methyl formate, which is finally subjected to ammonolysis with ammonia to yield formamide.

[0006] The third method involves synthesizing sodium formate using sodium hydroxide and carbon monoxide at a temperature of 150℃ and a pressure of 18-20MPa, and then reacting sodium formate with ammonium salt at 0.003-0.1MPa and 100-210℃ to obtain formamide (Chinese Patent CN1074900A).

[0007] The fourth method is to use sodium diformamide as a catalyst to catalyze the synthesis of formamide from carbon monoxide and ammonia in one step under a pressure of 1-4 MPa and a temperature of 40-150℃ (Chinese Patent CN103539689).

[0008] The fifth method is to synthesize formamide by electrocatalytic oxidation of methanol and ammonia under normal pressure conditions at a temperature of 20-30℃ and using sodium bicarbonate aqueous solution or sulfuric acid aqueous solution as electrolyte (Chinese Patent CN115142078A).

[0009] The sixth method is to synthesize formamide by electrocatalytic reduction of formic acid and nitrate or nitrite under the conditions of a temperature of 20-30℃ and using sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, potassium bicarbonate aqueous solution or sodium bicarbonate aqueous solution as electrolyte (Chinese Patent CN116219451A).

[0010] While the methods mentioned above can all synthesize formamide, thermochemical methods generally require high temperature and pressure, strong acids and strong bases, harsh reaction environments using highly toxic homogeneous catalysts, or multiple reaction processes. Electrocatalytic processes, on the other hand, require the use of electrolyte solutions to control the pH value of the solution, which increases the corresponding reaction cost and subsequent separation cost. Summary of the Invention

[0011] To address the problems existing in the prior art, this invention provides a method for one-step synthesis of formamide by heterogeneous photocatalytic coupling of methanol and ammonia. Formamide is obtained directly from methanol and ammonia water using a green and clean solar-driven photocatalytic method. The reaction can be carried out directly under the alkaline conditions provided by ammonia water, without the need for additional additives or electrolytes to adjust the pH of the reaction solution. At the same time, the catalyst and product can be separated simply by centrifugation. It has the advantages of low reaction cost, simple operation, mild reaction conditions and non-toxicity.

[0012] Specifically, the present invention provides the following technical solutions:

[0013] A method for one-step synthesis of formamide via photocatalytic coupling of methanol and ammonia includes the following steps:

[0014] The formamide was prepared by photocatalytic reaction of methanol, ammonia, water, and a photocatalyst under an inert atmosphere.

[0015] The photocatalyst is a nanoscale semiconductor carrier supported with a catalyst.

[0016] The co-catalyst is selected from one or more of MoS2, Ni2P, Pt, Pd, Au, Ag, and Rh.

[0017] The nanoscale semiconductor carrier is selected from one or more of CdS, ZnIn2S4, TiO2, C3N4, SrTiO3, and CeO2.

[0018] Preferably, the co-catalyst is Pt, and the nanoscale semiconductor support is CdS.

[0019] Preferably, the loading of the co-catalyst in the photocatalyst is 0.05 wt% to 5 wt%.

[0020] Preferably, the particle size of the nanoscale semiconductor carrier is 200-800 nm.

[0021] Preferably, the photocatalyst is prepared by a method comprising the following steps:

[0022] A metal salt solution containing Pt, Pd, Au, Ag, and Rh was mixed with a nanoscale semiconductor support and dispersed in water. The mixture was then ultrasonically dispersed to obtain an intermediate product. The intermediate product was then reduced in situ by adding NaBH4 aqueous solution to obtain the photocatalyst.

[0023] Preferably, the volume ratio of methanol to ammonia is (1:2) to (5:1);

[0024] And / or, the volume ratio of the ammonia water to water is 0.5 to 1:20;

[0025] And / or, the solution concentration of the photocatalyst is 0.01–10 mg / mL;

[0026] And / or, the concentration of the ammonia solution is 25% to 30%;

[0027] And / or, the water is ultrapure water with a resistivity greater than or equal to 18.2 MΩ·cm.

[0028] Preferably, the photocatalytic reaction is carried out in an aqueous system, without the need for additional additives or additional pH adjustment.

[0029] Preferably, the photocatalytic reaction is carried out under illumination, without the need for additional heating. In a preferred embodiment, the light source has a light intensity in the range of 1–5 W / cm². 2 The xenon lamp light source.

[0030] Preferably, the photocatalytic reaction takes 0.5 hours or more, more preferably 2 hours or more, for example, 2 to 20 hours.

[0031] Preferably, the pressure of the photocatalytic reaction is 0.05 to 0.15 MPa.

[0032] Preferably, the method specifically includes the following steps:

[0033] 1) The methanol, ammonia, water and photocatalyst are ultrasonically dispersed in the reaction vessel, and the reaction vessel is sealed after purging with argon gas to remove oxygen from the system.

[0034] 2) Irradiate the sealed reactor to induce a photocatalytic reaction. After the reaction, centrifuge the reaction solution to separate the catalyst and the liquid containing the target product formamide.

[0035] In this invention, the sealed reaction vessel is a quartz reaction tube or quartz reactor known in the art. In a preferred embodiment, the quartz reactor includes a chamber with an inner cavity and a liquid sampling port, a window disposed above the chamber, and a top cover disposed above the window; the top of the chamber includes inlet and outlet quartz pipes inserted into the inner cavity on the left and right sides.

[0036] The present invention has the following beneficial effects:

[0037] The present invention provides a one-step photocatalytic coupling method for the synthesis of formamide from methanol and ammonia. This method directly utilizes inexpensive ammonia and methanol as reactants to catalyze the reaction under mild light irradiation to obtain formamide. The reaction cost is low, the requirements for reaction equipment are low, the operation is simple, the reaction environment is green and clean, no toxic catalysts are required, and the catalysts can be recycled.

[0038] This approach fundamentally avoids the dependence on and consumption of highly toxic homogeneous catalysts in industry, further avoiding the problems of high pollution and high energy consumption in the formamide synthesis process. In addition, the one-step synthesis system without additional additives and the use of heterogeneous photocatalysts facilitate the simplification of the subsequent complex formamide purification and separation process, providing a new approach for the green and sustainable synthesis of formamide. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 The 1H NMR spectrum of formamide in this invention is shown.

[0041] Figure 2 The carbon nuclear magnetic resonance (C-NMR) spectrum of formamide in this invention is shown.

[0042] Figure 3 The photocatalytic synthesis performance of formamide with different photocatalysts is shown in the figure.

[0043] Figure 4 The synthesis performance of formamide under different comparative conditions is shown in the graph.

[0044] Figure 5 The photocatalytic performance of Pt-CdS for the synthesis of formamide under different trapping agent conditions is shown in the figure. Detailed Implementation

[0045] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0046] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0047] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention and not for limiting the claims of the present invention.

[0048] There are no particular restrictions on the purity of any raw materials used in this invention, but analytical grade is preferred.

[0049] All raw materials used in this invention are of conventional origin and abbreviation in the field, and their relevant uses are clear and well-defined. Those skilled in the art can purchase them from commercial products or prepare them by conventional methods based on their abbreviations and corresponding uses.

[0050] The photocatalyst provided by the present invention includes various nanoscale semiconductor supports, and one or more cocatalysts supported on the supports.

[0051] The photocatalyst of this invention uses a nanoscale semiconductor as a support, light-absorbing centers and CN-coupled catalytic sites, and a co-catalyst as the hydrogen evolution active site. First, the loading of the co-catalyst significantly catalyzes the hydrogen evolution reaction. Second, the close contact between the co-catalyst and the nanoscale semiconductor effectively improves the separation and transport of photogenerated electrons and holes on the semiconductor support, promoting the use of photogenerated electrons for surface hydrogen evolution and photogenerated holes for surface formamide synthesis.

[0052] Furthermore, comparative experiments with different reaction raw materials, with and without light, and with and without a catalyst all confirmed that the formamide synthesis method of the present invention is a reaction induced by a light-induced catalyst using methanol and ammonia as raw materials.

[0053] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0054] Unless otherwise defined, the content of the cocatalyst in the following examples refers to the mass percentage, such as 0.1% Pt-CdS is 0.1wt% Pt-CdS, that is, the Pt content in the photocatalyst is 0.1wt%.

[0055] The resistivity of the ultrapure water in the following examples is greater than or equal to 18.2 MΩ·cm.

[0056] Example 1

[0057] The preparation of semiconductor photocatalysts containing metal co-catalysts, taking Pt-CdS as an example, includes the following steps:

[0058] 0.5 mL of 1 mg / mL chloroplatinic acid aqueous solution was mixed with 100 mg CdS and 100 mL of water. The mixture was sonicated for 30 min and stirred for 2 h to ensure that the metal ions were fully adsorbed and combined with the semiconductor surface. 5 mL of freshly prepared 10 mg / mL NaBH4 aqueous solution was added, and the mixture was reacted for 1 h. After washing with water and centrifuging several times, the Pt-CdS photocatalyst was obtained by vacuum freeze-drying (the theoretical mass fraction of Pt is 0.5 wt%).

[0059] Experimental Example 1

[0060] A photocatalyst is used for the photocatalytic synthesis of formamide, comprising the following steps:

[0061] 1) Disperse 5 mg of the Pt-CdS photocatalyst prepared in Example 1 in a quartz reactor containing 18.5 mL of ultrapure water, and add 0.5 mL of methanol and 1 mL of ammonia water and stir further to obtain a reaction solution.

[0062] 2) Pass argon gas through the quartz reactor for 30 minutes to remove any oxygen that may be present in the reactor and reaction solution. Then seal the reaction device and sonicate it for 5 minutes to ensure that the catalyst is evenly dispersed in the solution.

[0063] 3) Irradiate the quartz reactor with a 300W xenon lamp (light intensity 1-3W / cm²). -2 The light source wavelength is the full spectrum distribution. After 2 hours, the light is stopped, the supernatant is recovered by centrifugation, and the synthesis performance of formamide is tested. It is recorded as "Pt-CdS".

[0064] Experimental Example 2

[0065] Same as in Experiment 1, except that the catalyst was replaced with CdS and the reaction time was extended to 4 hours, denoted as "CdS".

[0066] Experimental Example 3

[0067] Same as in Experiment 2, except that the catalyst was replaced with anatase TiO2, denoted as "TiO2-A".

[0068] Test Example 4

[0069] Same as Experiment 2, except that the catalyst was replaced with rutile TiO2, denoted as "TiO2-R".

[0070] Experimental Example 5

[0071] Same as in Experiment 2, except that the catalyst was replaced with P25 (TiO2 with both anatase and rutile phases), denoted as "P25".

[0072] Experimental Example 6

[0073] Same as Experiment 2, except that the catalyst was replaced with CeO2, denoted as "CeO2".

[0074] Experimental Example 7

[0075] Same as Experiment 2, except that the catalyst was replaced with SrTiO3, denoted as "SrTiO3".

[0076] Experimental Example 8

[0077] Same as in Experiment 2, except that the catalyst was replaced with C3N4, denoted as "C3N4".

[0078] Experimental Example 9

[0079] Same as Example 1, except that the catalyst was replaced with Pd-CdS, denoted as "Pd-CdS". The preparation steps of Pd-CdS are the same as in Example 1, except that the solution was replaced with a 0.5 mg / mL chloropalladium acid solution.

[0080] Experimental Example 10

[0081] Same as Example 1, except that the catalyst was replaced with Ag-CdS, denoted as "Ag-CdS". The preparation steps of Ag-CdS are the same as in Example 1, except that the solution was replaced with a 0.5 mg / mL silver nitrate solution.

[0082] Experimental Example 11

[0083] Same as Example 1, except that the catalyst was replaced with Au-CdS, denoted as "Au-CdS". The preparation steps of Au-CdS are the same as in Example 1, except that the solution was replaced with a 0.5 mg / mL chloroauric acid solution.

[0084] Experimental Example 12

[0085] Same as Example 1, except that the catalyst was replaced with Pt-C3N4, denoted as "Pt-C3N4". The preparation steps of Pt-C3N4 were the same as in Example 1, except that CdS was replaced with an equal mass of C3N4.

[0086] Experimental Example 13

[0087] Same as Example 1, except that the catalyst was replaced with Pt-SrTiO3, denoted as "Pt-SrTiO3". The preparation steps of Pt-SrTiO3 are the same as in Example 1, except that CdS was replaced with an equal mass of SrTiO3.

[0088] Test Example 14

[0089] Same as Example 1, except that the catalyst was replaced with Pt-TiO2 (anatase phase), denoted as "Pt-TiO2-A". The preparation steps of Pt-TiO2-A are the same as in Example 1, except that CdS was replaced with an equal mass of TiO2-A.

[0090] Experimental Example 15

[0091] Same as Example 1, except that the catalyst was replaced with Pt-TiO2 (rutile phase), denoted as "Pt-TiO2-R". The preparation steps of Pt-TiO2-R are the same as in Example 1, except that CdS was replaced with an equal mass of TiO2-R.

[0092] Experimental Example 16

[0093] Same as Example 1, except that the catalyst was replaced with Pt-P25, denoted as "Pt-P25". The preparation steps of Pt-P25 are the same as in Example 1, except that CdS was replaced with an equal mass of P25.

[0094] Experimental Example 17

[0095] Same as Example 1, except that the catalyst was replaced with Pt-CeO2, denoted as "Pt-CeO2". The preparation steps of Pt-CeO2 are the same as in Example 1, except that CdS was replaced with an equal mass of CeO2.

[0096] Comparative Test Example 1

[0097] Same as Experiment 1, except that no photocatalyst is added, denoted as "CH3OH+NH3-Light".

[0098] Comparative Test Example 2

[0099] Same as Experiment 1, except that no light was applied, and it is denoted as "CH3OH+NH3+Catalyst-Dark".

[0100] Comparative Test Example 3

[0101] Same as Experiment 1, except that methanol is not added, denoted as "CH3OH+Catalyst-Light".

[0102] Comparative Test Example 4

[0103] Same as Experiment 1, except that no ammonia is added, denoted as "NH3+Catalyst-Light".

[0104] Comparative Test Example 5

[0105] Same as in Experiment 1, except that an electron-terminal trapping agent, denoted as "CCl4", was added.

[0106] Comparative Test Example 6

[0107] Same as Experiment 1, except that a hole-end trapping agent, denoted as "Na2S", was added.

[0108] Comparative Test Example 7

[0109] Same as Experiment 1, except that the free radical scavenger DMPO was added, denoted as "DMPO".

[0110] For the testing of the product of this invention, the integral method of 1H NMR spectroscopy was used to qualitatively and quantitatively analyze formamide. Figure 1 The specific process is as follows: Using sodium maleate as an internal standard, different concentrations of formamide were prepared to simulate the reaction environment for testing. A standard curve was plotted with the peak area of ​​formamide versus the peak area and intensity of sodium maleate on the x-axis and the concentration values ​​of different formsamides on the y-axis to quantify the product formamide. Simultaneously, carbon NMR spectroscopy was used for qualitative detection of the product to further confirm that it is formamide. Figure 2 ).

[0111] Experimental Examples 1 and 2-17 test the synthetic performance of different photocatalysts and supported auxiliaries in the photocatalytic synthesis of formamide. The test results are as follows: Figure 3 As shown.

[0112] Experimental Example 1 and Comparative Examples 1-4 show the performance test results of Pt-CdS photocatalytic synthesis of formamide under different comparative conditions. Figure 4 As shown.

[0113] Experimental Examples 1 and Comparative Examples 5-7 are performance tests of the photocatalytic synthesis of formamide by Pt-CdS under comparative conditions with different scavenging agents. The test results are as follows: Figure 5 As shown.

[0114] Depend on Figure 1 , Figure 2 and Figure 3It can be seen that formamide was indeed synthesized in the reaction solution after the photocatalytic reaction. Furthermore, CdS-based semiconductor photocatalysts demonstrate a proven ability to directly synthesize formamide from methanol and ammonia, with Pt-CdS exhibiting the fastest photocatalytic formamide synthesis rate.

[0115] Depend on Figure 4 It can be seen that the Pt-CdS catalyst only exhibits high formamide synthesis performance when methanol and ammonia are present simultaneously under light conditions. No significant formamide synthesis performance was detected under methanol, ammonia, or dark conditions alone. These results indicate that the starting materials for this reaction are methanol and ammonia.

[0116] Depend on Figure 5 It can be seen that the use of the electron-terminal scavenger CCl4 did not significantly affect the synthesis performance of formamide. Conversely, the use of the hole-terminal scavenger Na2S and the free radical scavenger DMPO severely hindered the synthesis of formamide, and no obvious formamide was detected in the solution after the reaction. These results indicate that the photocatalytic direct synthesis of formamide from methanol and ammonia is an oxidation reaction involving photogenerated holes, and also a free radical-mediated reaction.

[0117] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for one-step synthesis of formamide via photocatalytic coupling of methanol and ammonia, characterized in that, Includes the following steps: The formamide was prepared by mixing methanol, ammonia, water and photocatalyst in a closed reaction vessel and then carrying out a photocatalytic reaction. The photocatalyst is a nanoscale semiconductor carrier supported with a catalyst. The co-catalyst is selected from one or more of MoS2, Ni2P, Pt, Pd, Au, Ag, and Rh; The nanoscale semiconductor carrier is selected from one or more of CdS, ZnIn2S4, TiO2, C3N4, SrTiO3, and CeO2.

2. The method for one-step synthesis of formamide by photocatalytic coupling of methanol and ammonia according to claim 1, characterized in that, The co-catalyst is Pt, and the nanoscale semiconductor support is CdS.

3. The method for one-step synthesis of formamide by photocatalytic coupling of methanol and ammonia according to claim 1, characterized in that, The loading of the co-catalyst in the photocatalyst is 0.05wt% to 5wt%.

4. The method for one-step synthesis of formamide by photocatalytic coupling of methanol and ammonia according to claim 1, characterized in that, The photocatalyst is prepared by a method comprising the following steps: A metal salt solution containing Pt, Pd, Au, Ag, and Rh was mixed with a nanoscale semiconductor support and dispersed in water. The mixture was then ultrasonically dispersed to obtain an intermediate product. The intermediate product was then reduced in situ by adding NaBH4 aqueous solution to obtain the photocatalyst.

5. The method for one-step synthesis of formamide by photocatalytic coupling of methanol and ammonia according to claim 1, characterized in that, The volume ratio of methanol to ammonia is (1:2) to (5:1); And / or, the volume ratio of the ammonia water to water is 0.5 to 1:20; And / or, the solution concentration of the photocatalyst is 0.01–10 mg / mL; And / or, the concentration of the ammonia solution is 25% to 30%; And / or, the water is ultrapure water with a resistivity greater than or equal to 18.2 MΩ·cm.

6. The method for one-step synthesis of formamide by photocatalytic coupling of methanol and ammonia according to any one of claims 1-5, characterized in that, The photocatalytic reaction is carried out in an aqueous system and does not require the addition of additional additives or additional pH adjustment.

7. The method for one-step synthesis of formamide by photocatalytic coupling of methanol and ammonia according to any one of claims 1-5, characterized in that, The photocatalytic reaction is a photocatalytic reaction carried out under light conditions, without the need for additional heating.

8. The method for one-step synthesis of formamide by photocatalytic coupling of methanol and ammonia according to any one of claims 1-5, characterized in that, The photocatalytic reaction takes 0.5 hours or more, preferably 2 hours or more.

9. The method for one-step synthesis of formamide by photocatalytic coupling of methanol and ammonia according to any one of claims 1-5, characterized in that, The pressure of the photocatalytic reaction is 0.05–0.15 MPa.

10. The method for one-step synthesis of formamide by photocatalytic coupling of methanol and ammonia according to claim 1, characterized in that, The method specifically includes the following steps: 1) The methanol, ammonia, water and photocatalyst are ultrasonically dispersed in the reaction vessel, and the reaction vessel is sealed after purging with argon gas to remove oxygen from the system. 2) Irradiate the sealed reactor to induce a photocatalytic reaction. After the reaction, centrifuge the reaction solution to separate the catalyst and the liquid containing the target product formamide.

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