Nitride synthesis method assisted by arc discharge plasma and nitride

Abstract

The invention relates to the technical field of plasma and electro-catalysis coupling, in particular to an arc discharge plasma assisted nitride synthesis method and nitride. The nitride is synthesized by the method. The method comprises the following steps: building an arc discharge plasma-assisted nitrogen oxidation and electroreduction integrated system; parallel plate electrode arc discharge is adopted in the integrated system; introducing mixed gas of nitrogen and oxygen into the integrated system; carrying out arc discharge on the mixed gas to obtain nitrogen oxide; and introducing the nitrogen oxide into an electro-catalysis device added with an electrolyte and a composite catalyst, and synthesizing the nitride through electro-catalysis. The combined use of arc discharge and the composite catalyst not only can generate nitrogen oxide with higher concentration, but also can synthesize nitride meeting the level required by economic feasibility.

Description

Technical Field

[0001] The invention relates to the technical field of plasma and electrocatalysis coupling, and in particular to an arc discharge plasma assisted nitride synthesis method and nitride. Background Art

[0002] High-value nitrogen-containing compounds (such as ammonia, oximes, and amino acids) are of great significance in meeting today's agricultural, industrial, and medical needs. Despite this, the industrial production of nitrogen-containing compounds is still inseparable from energy-intensive processes. Electrocatalytic nitrogen reduction technology for synthesizing nitrogen-containing compounds has the advantages of being able to directly use water as a hydrogen source, renewable energy as a driving force, and being able to operate at room temperature and pressure. It is regarded as the most promising new process for synthesizing nitrogen-containing compounds. Unfortunately, due to the inertness of nitrogen molecules, the level of production of nitrogen-containing compounds by direct electrocatalytic nitrogen reduction is still lower than the level required for economic feasibility.

[0003] At present, many studies have used nitrogen oxides in industrial "three wastes" to synthesize nitrogen-containing compounds instead of electrocatalytic nitrogen reduction to produce nitrogen-containing compounds, which solves the environmental pollution problem and realizes the process of synthesizing nitrogen-containing compounds. However, the complexity of the environmental system and the low concentration of nitrogen oxides make it not a feasible solution to use industrial "three wastes" to synthesize ammonia in industry.

[0004] The use of plasma technology to convert nitrogen into nitrogen oxides has made some progress, but there is still a problem of low conversion efficiency. For example, the Chinese invention patent with application number 202310001540.0 discloses a plasma-assisted nitrogen oxidation and electroreduction integrated ammonia synthesis method, which reports that the concentration of nitrogen oxides is low and it is difficult to meet industrial needs. The document Highly Efficient Electrosynthesis of Glycine over an Atomically Dispersed Iron Catalyst (J.Am.Chem.Soc.2024,146,10084-10092) reports a spark discharge mode plasma-assisted amino acid synthesis method, which has a low concentration of nitrogen oxides (220mM) produced by nitrogen activation, which is seriously mismatched with the concentration of nitrogen oxides (500mM) required for the electrocatalytic CN coupling process, resulting in a significant reduction in amino acid synthesis performance.

[0005] In summary, it is necessary to develop an arc discharge plasma-assisted nitride synthesis method and nitride to solve the problem of low nitrogen oxide concentration generated by the existing plasma nitrogen activation process. Summary of the invention

[0006] The present invention aims to provide an arc discharge plasma assisted nitride synthesis method and nitride, and the specific technical scheme is as follows:

[0007] In a first aspect, the present invention provides an arc discharge plasma assisted nitride synthesis method, comprising:

[0008] Step S1, constructing an arc discharge plasma-assisted nitrogen oxidation and electroreduction integrated system; parallel plate electrode arc discharge is used in the integrated system;

[0009] Step S2, introducing a mixed gas of nitrogen and oxygen into the integrated system; the mixed gas is subjected to arc discharge to obtain nitrogen oxides;

[0010] Step S3, introducing the nitrogen oxides into an electrocatalytic device containing an electrolyte and a composite catalyst to synthesize nitrides through electrocatalysis.

[0011] Optionally, the volume proportion of nitrogen in the mixed gas is 20% to 80%, and the volume proportion of oxygen is 80% to 20%.

[0012] Optionally, the flow rate of the mixed gas into the integrated system is 25 to 200 mL / min.

[0013] Optionally, the distance between two electrodes in the parallel plate electrodes is 0.5-2 mm.

[0014] Optionally, the diameter of each electrode in the parallel plate electrodes is 9-16 mm.

[0015] Optionally, when performing arc discharge, the voltage adopted by the integrated system is 20 to 250 V; and the activation discharge time of the mixed gas by the integrated system is 1 to 8 hours.

[0016] Optionally, the composite catalyst includes a carrier and metal active sites attached to the carrier; the metal active sites include transition metal active sites; the transition metal active sites include at least one of copper, cobalt, manganese, bismuth, palladium, indium, lead, tin, nickel and silver.

[0017] Optionally, the carrier comprises titanium dioxide.

[0018] Optionally, the voltage of the electrocatalytic device is controlled to be -0.2V to -1.0V relative to the reversible hydrogen electrode, or the current of the electrocatalytic device is controlled to be -10 to -300mA.

[0019] In a second aspect, the present invention provides a nitride synthesized by the arc discharge plasma assisted nitride synthesis method;

[0020] When the synthesized nitride is ammonia, the electrolyte is an alkaline solution;

[0021] When the synthesized nitride is cyclohexanone oxime, the electrolyte is an alkaline solution; cyclohexanone is also added to the electrocatalytic device; the concentration of the cyclohexanone in the alkaline solution is 50-500 mmol / L;

[0022] When the synthesized nitride is cyclopentanone oxime, the electrolyte is an alkaline solution; cyclopentanone is also added to the electrocatalytic device; the concentration of the cyclopentanone in the alkaline solution is 50-500 mmol / L;

[0023] When the synthesized nitride is benzaldehyde oxime, the electrolyte is an alkaline solution; benzaldehyde is also required to be added to the electrocatalytic device; the concentration of the benzaldehyde in the alkaline solution is 10-50 mmol / L;

[0024] The concentration of the alkali solution is 1.1-1.5 mol / L; the alkali solution includes sodium hydroxide solution or potassium hydroxide solution;

[0025] When the synthesized nitride is glycine, the electrolyte is an acid solution; glyoxylic acid is also added to the electrocatalytic device; the concentration of the glyoxylic acid in the acid solution is 50-500 mmol / L;

[0026] When the synthesized nitride is alanine, the electrolyte is an acid solution; pyruvic acid is also added to the electrocatalytic device; the concentration of the pyruvic acid in the acid solution is 50-500 mmol / L;

[0027] The concentration of the acid solution is 0.1-0.5 mol / L; the acid solution includes a sulfuric acid solution.

[0028] The application of the technical solution of the present invention has at least the following beneficial effects:

[0029] The present invention provides an arc discharge plasma-assisted nitride synthesis method, which can solve the problem of low nitrogen oxide concentration generated by the existing plasma nitrogen activation process. Specifically, in the stage of generating nitrogen oxides, the present invention uses parallel plate electrodes for arc discharge, which can effectively increase the overlapping area of ​​the discharge area and the mixed gas, increase the activation rate of nitrogen and oxygen, and increase the collision probability between nitrogen free radicals and oxygen free radicals, thereby improving the yield of nitrogen oxides; in the stage of synthesizing nitrides, the present invention uses alkaline solution to absorb nitrogen oxides to generate nitrate ions and nitrite ions, and gradually converts nitrate ions and nitrite ions into nitrides with the help of composite catalysts, so that the nitride synthesis level reaches the level required for economic feasibility; therefore, the present invention uses arc discharge and composite catalysts in combination to produce nitrogen oxides at a higher concentration and synthesize nitrides that meet the level required for economic feasibility.

[0030] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0032] Figure 1 The relationship between the activation discharge time and the concentration of nitrogen oxides in Comparative Example 1 and Example 2;

[0033] Figure 2 is the relationship between the arc discharge time and the selectivity of synthesizing cyclohexanone oxime in Example 2;

[0034] Figure 3 This is the case where the concentration of nitrogen oxides generated in Comparative Example 2 and Example 1 is measured within 1 hour of activation discharge time;

[0035] Figure 4 This is the case where the rate of synthetic ammonia is measured within 1 h of activation discharge time in Comparative Example 2 and Example 1;

[0036] Figure 5 This is the relationship between the arc discharge time and the selectivity of synthesizing glycine in Example 3. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0038] Example 1 (arc discharge, ammonia synthesis):

[0039] An arc discharge plasma assisted nitride synthesis method comprising:

[0040] Step S1, reference Efficient Nitrogen Fixation to Ammonia through Integration of Plasma Oxidation with Electrocatalytic Reduction (Angew. Chem. Int. Ed. 2021, 60, 14131–14137) Supporting Information, page 6, Fig. S1, building an arc discharge plasma-assisted nitrogen oxidation and electro-reduction integrated system; parallel plate electrode arc discharge is used in the integrated system;

[0041] Step S2, introducing a mixed gas of nitrogen and oxygen into the integrated system; the mixed gas is subjected to arc discharge to obtain nitrogen oxides;

[0042] Step S3, introducing the nitrogen oxides into an electrocatalytic device added with alkaline solution (such as sodium hydroxide solution with a concentration of 0.5 mol / L) and 2 mg of composite catalyst to synthesize nitride (specifically ammonia) through electrocatalysis.

[0043] The volume proportion of nitrogen in the mixed gas is 50%, and the volume proportion of oxygen is 50%.

[0044] The flow rate of the mixed gas into the integrated system is 200 mL / min.

[0045] The distance between the two electrodes in the parallel plate electrode is 1 mm.

[0046] The diameter of each electrode in the parallel plate electrodes is 16 mm.

[0047] When performing arc discharge, the voltage adopted by the integrated system is 200V; the activation discharge time of the integrated system for the mixed gas is 1h.

[0048] The composite catalyst comprises a carrier and metal active sites attached to the carrier; the metal active sites comprise transition metal active sites; the transition metal active sites are copper and cobalt.

[0049] The carrier is titanium dioxide, which can promote the transition metal active sites to be evenly dispersed on the carrier.

[0050] The voltage of the electrocatalytic device is controlled to be -0.3 V relative to the reversible hydrogen electrode.

[0051] Embodiment 2 (arc discharge, synthesis of cyclohexanone oxime):

[0052] Different from Example 1, the activation discharge time of the mixed gas by the integrated system is 8 hours; cyclohexanone is also added to the electrocatalytic device; the concentration of the cyclohexanone in the alkaline solution is 100 mmol / L; the concentration of the alkaline solution is 1.0 mol / L; the current of the electrocatalytic device is controlled to be -30 mA; the transition metal active sites are copper and manganese; and the nitride is specifically cyclohexanone oxime.

[0053] Comparative Example 1 (spark discharge, synthesis of cyclohexanone oxime):

[0054] Different from Example 2, a needle tip electrode was used for spark discharge, and the device was constructed with reference to Microscopic-Level Insights into the Mechanism of Enhanced NH3 Synthesis in Plasma-Enabled Cascade N2Oxidation-lectroreduction System J.Am.Chem.Soc.2022,144,10193-10200 (Supporting Information Figure S20).

[0055] Comparative Example 2 (spark discharge, synthetic ammonia):

[0056] Different from Example 1, a needle tip electrode was used for spark discharge, and the device was constructed with reference to Microscopic-Level Insights into the Mechanism of Enhanced NH3 Synthesis in Plasma-Enabled Cascade N2Oxidation-lectroreduction System J.Am.Chem.Soc.2022,144,10193-10200, Figure S20 of the supporting information.

[0057] In Comparative Example 1 and Example 2, the concentration of nitrogen oxides generated was measured at different discharge times. Figure 1 .Depend on Figure 1 It is known that with the extension of discharge time, the concentration of nitrogen oxides generated gradually increases, and the concentration of nitrogen oxides generated by arc discharge is significantly higher than that generated by spark discharge.

[0058] In Example 2, the selectivity of synthesizing cyclohexanone oxime was determined respectively with different arc discharge times. Figure 2 .Depend on Figure 2It is known that with the extension of arc discharge time, the selectivity of the composite catalyst for synthesizing cyclohexanone oxime shows a higher level; specifically, the copper in the composite catalyst promotes the conversion of nitrate ions into nitrite ions, and the manganese in the composite catalyst adsorbs cyclohexanone on the one hand, and promotes the conversion of nitrite ions into higher concentrations of hydroxylamine on the other hand. Further, higher concentrations of hydroxylamine and cyclohexanone are coupled to form cyclohexanone oxime.

[0059] In Comparative Example 2 and Example 1, the concentration of nitrogen oxides generated was measured within 1 h of the activation discharge time. Figure 3 .Depend on Figure 3 It is known that within the activation discharge time of 1h, the concentration of nitrogen oxides generated by arc discharge is significantly higher than that generated by spark discharge.

[0060] In Comparative Example 2 and Example 1, the rate of synthesizing ammonia was measured within 1 h of the activation discharge time. Figure 4 .Depend on Figure 4 It is known that the rate of ammonia synthesis by arc discharge is significantly higher than that by spark discharge. Specifically, the copper in the composite catalyst promotes the conversion of nitrate ions into nitrite ions, and the cobalt in the composite catalyst promotes the synthesis of ammonia from nitrite ions.

[0061] Embodiment 3:

[0062] The difference from Example 2 is that the alkaline solution is replaced by acid solution; cyclohexanone is replaced by glyoxylic acid; the transition metal active site copper and manganese are replaced by tin; the activation discharge time is replaced by 4h; the concentration of glyoxylic acid in the acid solution is 200mmol / L; the concentration of the acid solution is 0.1mol / L; the voltage of the electrocatalytic device is controlled to be -0.6V relative to the reversible hydrogen electrode; and the acid solution is a sulfuric acid solution.

[0063] In Example 3, the selectivity of synthesizing glycine was measured at different arc discharge times. Figure 5 .Depend on Figure 5 It is known that with the extension of arc discharge time, the selectivity of the catalyst for synthesizing glycine shows a higher level. Specifically, the tin in the catalyst promotes the conversion of nitrate ions and nitrite ions into higher concentrations of hydroxylamine on the one hand, and adsorbs glyoxylic acid on the other hand. Further, higher concentrations of hydroxylamine and glyoxylic acid couple to form glycine oxime; further, glycine oxime continues to be electrochemically reduced at the tin site and converted into glycine.

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for synthesizing nitrides assisted by arc discharge plasma, characterized in that: include: Step S1, constructing an arc discharge plasma-assisted nitrogen oxidation and electroreduction integrated system; parallel plate electrode arc discharge is used in the integrated system; Step S2, introducing a mixed gas of nitrogen and oxygen into the integrated system; the mixed gas is subjected to arc discharge to obtain nitrogen oxides; Step S3, introducing the nitrogen oxides into an electrocatalytic device containing an electrolyte and a composite catalyst to synthesize nitrides through electrocatalysis.

2. The arc discharge plasma assisted nitride synthesis method according to claim 1, characterized in that: The volume proportion of nitrogen in the mixed gas is 20% to 80%, and the volume proportion of oxygen is 80% to 20%.

3. The arc discharge plasma assisted nitride synthesis method according to claim 1, characterized in that: The flow rate of the mixed gas into the integrated system is 25-200 mL / min.

4. The arc discharge plasma assisted nitride synthesis method according to claim 1, characterized in that: The distance between the two electrodes in the parallel plate electrodes is 0.5-2 mm.

5. The arc discharge plasma assisted nitride synthesis method according to claim 1, characterized in that: The diameter of each electrode in the parallel plate electrodes is 9-16 mm.

6. The arc discharge plasma assisted nitride synthesis method according to claim 1, characterized in that: When performing arc discharge, the voltage adopted by the integrated system is 20 to 250V; the activation discharge time of the mixed gas by the integrated system is 1 to 8 hours.

7. The arc discharge plasma assisted nitride synthesis method according to claim 1, characterized in that: The composite catalyst comprises a carrier and metal active sites attached to the carrier; the metal active sites comprise transition metal active sites; the transition metal active sites comprise at least one of copper, cobalt, manganese, bismuth, palladium, indium, lead, tin, nickel and silver.

8. The arc discharge plasma assisted nitride synthesis method according to claim 7, characterized in that: The support includes titanium dioxide.

9. The arc discharge plasma assisted nitride synthesis method according to claim 1, characterized in that: The voltage of the electrocatalytic device is controlled to be -0.2V to -1.0V relative to the reversible hydrogen electrode, or the current of the electrocatalytic device is controlled to be -10 to -300mA.

10. A nitride, characterized in that: The nitride is synthesized by the arc discharge plasma assisted nitride synthesis method according to any one of claims 1 to 9; When the synthesized nitride is ammonia, the electrolyte is an alkaline solution; When the synthesized nitride is cyclohexanone oxime, the electrolyte is an alkaline solution; cyclohexanone is also added to the electrocatalytic device; the concentration of the cyclohexanone in the alkaline solution is 50-500 mmol / L; When the synthesized nitride is cyclopentanone oxime, the electrolyte is an alkaline solution; cyclopentanone is also added to the electrocatalytic device; the concentration of the cyclopentanone in the alkaline solution is 50-500 mmol / L; When the synthesized nitride is benzaldehyde oxime, the electrolyte is an alkaline solution; benzaldehyde is also required to be added to the electrocatalytic device; the concentration of the benzaldehyde in the alkaline solution is 10-50 mmol / L; The concentration of the alkali solution is 0.5-1.5 mol / L; the alkali solution includes sodium hydroxide solution or potassium hydroxide solution; When the synthesized nitride is glycine, the electrolyte is an acid solution; glyoxylic acid is also added to the electrocatalytic device; the concentration of the glyoxylic acid in the acid solution is 50-500 mmol / L; When the synthesized nitride is alanine, the electrolyte is an acid solution; pyruvic acid is also added to the electrocatalytic device; the concentration of the pyruvic acid in the acid solution is 50-500 mmol / L; The concentration of the acid solution is 0.1-0.5 mol / L; the acid solution includes a sulfuric acid solution.

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