Supported catalyst, method for its preparation and use thereof

Abstract

The application provides a supported catalyst precursor, which comprises a carrier and a Bi film supported on the carrier, and the supported catalyst precursor is subjected to electrochemical reduction to obtain a supported catalyst loaded with Bi nanoparticles. The catalyst has the advantages of simple preparation method, easy mass synthesis and low cost. The supported catalyst can be used for electrocatalytic reduction of nitrate to synthesize hydroxylamine. When the total potential is-0.6 to-1.2 volts relative to a reversible hydrogen electrode, the Faraday efficiency is more than 60%, and when the total potential is-1.2 volts relative to a reversible hydrogen electrode, the yield reaches 700 micromoles / square centimeter / hour. The supported catalyst provided by the application can be recycled for 12 cycles, and the yield of hydroxylamine is stable.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of catalysts, and particularly relates to a supported catalyst, a preparation method thereof and application thereof. BACKGROUND

[0002] Hydroxylamine, as one of the important nitrogen-containing raw materials, has been widely used in the synthesis of organic amines, especially in the fields of agricultural chemistry and pharmaceuticals. Currently, Raschig method, HNO3 reduction method and NO reduction method are used in industry to synthesize hydroxylamine. However, the Raschig method uses highly corrosive and seriously polluting SO2 as a reducing agent, and a large amount of by-product ammonium sulfate is produced. The HNO3 reduction method and the NO reduction method use hydrogen obtained in the petroleum chemical process as a hydrogen source, and use noble metal (Pt, Pd and Rh) materials as catalysts, which greatly increases the production cost of hydroxylamine. Although potential alternative routes for synthesizing hydroxylamine have been reported, they also have some drawbacks that cannot be ignored, such as excessive NH3 feed and high-cost product separation. In addition, it is worth noting that all the nitrogen sources for these traditional hydroxylamine synthesis come from the Haber-Bosch process under harsh conditions, which leads to serious carbon emission and energy consumption problems. Therefore, it is extremely important to develop a more feasible alternative route for synthesizing hydroxylamine to avoid the above-mentioned drawbacks.

[0003] Compared with the traditional synthesis route, green, cheap and abundant H2O and nitrate are used as hydrogen source and nitrogen source respectively, which is an ideal raw material for producing hydroxylamine. At the same time, the use of electric synthesis driven by renewable electricity at room temperature and pressure lays a promising way for a more sustainable synthesis process. Therefore, the new route of nitrate electro-synthesis of hydroxylamine not only can upgrade the green synthesis process of hydroxylamine, but also can promote the fixation of nitrogen, but the development of catalysts for the process is still a great challenge. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a supported catalyst which is green, easy to synthesize in large quantities and low in cost, and can be used for electro-catalytic synthesis of hydroxylamine from nitrate.

[0005] To achieve the above-mentioned purpose, the technical solutions of the present application are as follows:

[0006] The present application provides a supported catalyst precursor, comprising a carrier and a Bi film supported on the carrier.

[0007] Preferably, the thickness of the Bi film is 600-900 nm.

[0008] The present application provides a supported catalyst, comprising a carrier and Bi nanoparticles supported on the carrier.

[0009] Preferably, the loading of the Bi nanoparticles is 0.3-0.7 mg / cm2.

[0010] Preferably, in the supported catalyst precursor or the supported catalyst, the support is a porous support.

[0011] Preferably, the porous support is selected from carbon fiber paper, carbon black, carbon nanotube or graphene.

[0012] Preferably, the pore size of the porous support is 200-500 nm.

[0013] The present application also provides a preparation method of the supported catalyst, comprising the following steps:

[0014] (a) depositing Bi on the support by magnetron sputtering to obtain a support with a Bi film;

[0015] (b) electrochemically reducing the support with the Bi film to obtain the supported catalyst.

[0016] The present application provides a preparation method of hydroxylamine, comprising the following steps:

[0017] Under the action of the supported catalyst, electrocatalytic reduction of nitrate is carried out to obtain hydroxylamine.

[0018] The present application provides a supported catalyst precursor comprising a support and a Bi film supported on the support. The supported catalyst precursor is electrochemically reduced to obtain a supported catalyst with Bi nanoparticles. The catalyst is simple to prepare, easy to synthesize in large quantities and low in cost. The supported catalyst can be used for electrocatalytic reduction of nitrate to synthesize hydroxylamine. When the total potential is-0.6 to-1.2 V relative to the reversible hydrogen electrode, the Faraday efficiency is above 60%. When the total potential is-1.2 V relative to the reversible hydrogen electrode, the yield reaches 700 μmol / cm2 / h. The supported catalyst provided by the present application can be recycled for 12 cycles, and the yield of hydroxylamine remains stable. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The scanning electron microscope picture of the carbon fiber paper with the Bi film is shown in Figure 1 (the magnification ratio is 4 μm);

[0020] Figure 2 The scanning electron microscope picture of the carbon fiber paper with the Bi film is shown in Figure 2 (the magnification ratio is 500 nm);

[0021] Figure 3 The scanning electron microscope picture of the carbon fiber paper with the Bi film is shown in Figure 3 (the magnification ratio is 500 nm);

[0022] Figure 4Faradaic efficiency of Bi nanoparticle-carbon fiber paper for electrocatalytic reduction of nitrate to hydroxylamine at different total potentials;

[0023] Figure 5 Yield of Bi nanoparticle-carbon fiber paper for electrocatalytic reduction of nitrate to hydroxylamine at different total potentials;

[0024] Figure 6 Yield of Bi nanoparticle-carbon fiber paper for electrocatalytic reduction of nitrate to hydroxylamine at different total potentials; DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be apparently and completely described in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without any creative work belong to the protection scope of the present application.

[0026] The present application provides a supported catalyst precursor, comprising a carrier and a Bi film supported on the carrier.

[0027] In some possible implementations, the carrier is a porous carrier, and a pore size of the carrier is 200-500 nm, preferably 300 nm; in some embodiments, the carrier is selected from a porous carrier selected from carbon fiber paper, carbon black, carbon nanotube or graphene, preferably carbon fiber paper, and more preferably carbon fiber paper of model 39BB produced by SGL Carbon Company in Germany. In some embodiments, a thickness of the Bi film is 600-900 nm, preferably 700-800 nm, and more preferably 760 nm.

[0028] The supported catalyst precursor can be obtained by magnetron sputtering.

[0029] Specifically, a porous carrier is used as a substrate, and a Bi disc is used as a target material, and a Bi film is magnetron sputtered under the action of a sputtering source. In some embodiments, the sputtering source is argon ion, preferably argon gas, and a pressure of the argon gas is preferably 2x10 -3 -3x10 -3 millibar, and more preferably 2.2x10 -3 -2.8x10 -3 millibar, for example, 2.4x10 -3 -2.6x10 -3The flow rate of the argon is preferably 20-100 mL / min, more preferably 50-70 mL / min, for example, it can be 60 mL / min. The current of the magnetron sputtering is preferably 40-80 mA, more preferably 50-70 mA, for example, it can be 60 mA. The time of the magnetron sputtering is preferably 20-60 min, more preferably 30-50 min, for example, it can be 40 min. After the magnetron sputtering, the supported catalyst precursor is obtained.

[0030] The application provides a supported catalyst, comprising a carrier and Bi nanoparticles supported on the carrier.

[0031] Specifically, the carrier is preferably a porous carrier, and the pore size of the carrier is preferably 200-500 nm, more preferably 300 nm. In some embodiments, the carrier is selected from a porous carrier, preferably carbon fiber paper, carbon black, carbon nanotube or graphene, more preferably carbon fiber paper, for example, the carbon fiber paper produced by SGL Carbon Company in Germany, model 39BB. The loading amount of the Bi nanoparticles on the carrier is 0.3-0.7 mg / cm2, preferably 0.5 mg / cm2.

[0032] The application also provides a preparation method of the supported catalyst, comprising the following steps:

[0033] The Bi is compounded on the carrier by the method of magnetron sputtering to obtain a supported catalyst precursor, and the preparation method of the supported catalyst precursor is as described above. The supported catalyst precursor is subjected to an electrochemical reduction reaction to obtain a supported catalyst.

[0034] In some embodiments, the supported catalyst precursor is subjected to an electrochemical reduction reaction in an electrolytic cell system, and the electrolytic cell system is preferably an H-type electrolytic cell system. The electrolytic cell system comprises a working electrode, a counter electrode, a reference electrode, an ion exchange membrane and an electrolyte solution. The working electrode is the supported catalyst precursor, the counter electrode is preferably a titanium mesh loaded with IrO2, the reference electrode is preferably a silver / silver chloride electrode, the ion exchange membrane is preferably a Nafion 115 membrane, and the electrolyte solution is preferably a sulfuric acid aqueous solution, and the concentration of the sulfuric acid aqueous solution is preferably 0.1-1 mol / L, more preferably 0.5 mol / L. In some possible implementations, the applied potential of the electrochemical reduction reaction is -0.4 to -0.8 V vs. reversible hydrogen electrode, preferably -0.5 to -0.7 V vs. reversible hydrogen electrode, more preferably -0.6 V vs. reversible hydrogen electrode, and the time of the electrochemical reduction reaction is preferably 1-3 h, preferably 2 h. After the electrochemical reaction is completed, the supported catalyst is obtained.

[0035] The application provides a preparation method of a hydroxylamine, comprising the following steps:

[0036] The nitrate is subjected to electrocatalytic reduction under the action of the above-mentioned supported catalyst to obtain hydroxylamine.

[0037] In some embodiments, the electrocatalytic reduction is carried out in an electrolytic cell system, which is preferably an H-type electrolytic cell system; the electrolytic cell system comprises a working electrode, a counter electrode, a reference electrode, an ion exchange membrane and an electrolyte solution; wherein the working electrode is the above-mentioned supported catalyst precursor, the counter electrode is preferably a titanium mesh loaded with IrO2, the reference electrode is preferably a silver / silver chloride electrode, the ion exchange membrane is preferably a Nafion 115 membrane, and the electrolyte solution is preferably a mixture containing nitrate and sulfuric acid aqueous solution, the nitrate is preferably from sodium nitrate or potassium nitrate, for example, it can be potassium nitrate, the molar ratio of nitrate to sulfuric acid is 1:4-6, preferably 1:5, for example, the molar concentration of nitrate is 0.1 mol / L, and the molar concentration of sulfuric acid is 0.5 mol / L. In some possible implementations, the electrocatalytic reduction process is carried out in a constant potential mode, and the total potential is preferably -0.5 to -1.5 volts relative to the reversible hydrogen electrode, preferably -0.6, -0.7, -0.8, -0.9, -1.0, -1.1 or -1.2 volts relative to the reversible hydrogen electrode. The reaction time of electrocatalytic reduction is 0.5-3 h, preferably 1 h, and after the reaction is completed, hydroxylamine is obtained.

[0038] During the reaction, argon is preferably introduced into the cathode electrolyte, and the gas generated by the cathode reaction is carried into the gas chromatograph by argon for online monitoring of the gas content in the catalytic product. After the reaction is completed, 0.4 ml of the cathode electrolyte is taken and mixed with 0.1 ml of d6-DMSO, 12.5 μl of 50 wt% C2H2O3 and 0.1 ml of 6.0 mmol / L DSS, and the content of liquid product hydroxylamine can be detected by nuclear magnetic resonance hydrogen spectrum.

[0039] The present application provides a supported catalyst precursor comprising a carrier and a Bi film loaded on the carrier, and the supported catalyst precursor is subjected to electrochemical reduction to obtain a supported catalyst loaded with Bi nanoparticles. The catalyst has a simple preparation method, is easy to synthesize in large quantities, and has low cost. The supported catalyst can be used for electrocatalytic reduction of nitrate to synthesize hydroxylamine. When the total potential is -0.6 to -1.2 volts relative to the reversible hydrogen electrode, the Faraday efficiency is above 60%, and when the total potential is -1.2 volts relative to the reversible hydrogen electrode, the yield reaches 700 μmol / cm2 / h. The present application also provides a recycling use of the same supported catalyst, and the yield of hydroxylamine is maintained stable after 12 cycles of recycling use.

[0040] Example 1

[0041] Fix the Bi disk to the target position, cut porous carbon fiber paper to fit the disk size (9cm in diameter), and attach the back of the carbon fiber paper to the disk using double-sided tape. Turn on the magnetron sputtering power supply, then turn on the mechanical pump and molecular pump in sequence, setting the molecular pump to the highest power, until the system reaches a suitable vacuum value (5×10). -6 After adding millibars, the power of the molecular pump was reduced to 30% of its maximum power. The argon gas switch was turned on, and the argon gas flow rate was adjusted to 100 mL / min. The DC power supply was turned on and set to constant current mode, with the current set to 100 mA. After observing the ignition of the Bi disk at the target site through the glass window, the current was successively reduced to 60 mA and the argon gas flow rate was decreased to 20 mL / min. Timing was started, and after 40 minutes, the current was set to 0 mA, and the magnetron sputtering device was turned off, yielding carbon fiber paper with a composite Bi film.

[0042] The carbon fiber paper with the above-mentioned composite Bi film was analyzed, and the results are as follows: Figure 1 and Figure 2 As shown, Figure 1 and Figure 2 These are scanning electron microscope (SEM) images at different magnifications. The carbon fiber paper sections containing the aforementioned composite Bi film were subjected to scanning electron microscopy imaging, and the results are as follows. Figure 3 As shown, Figure 3 These are scanning electron microscope images of the slices.

[0043] Example 2

[0044] In an H-type electrolytic cell system, a Nafion 115 membrane was used as an ion exchange membrane. The carbon fiber paper of the composite Bi membrane prepared in Example 1 was used as the working electrode. A titanium mesh loaded with IrO2 and a silver / silver chloride electrode were used as the counter electrode and reference electrode, respectively. A sulfuric acid solution of 0.5 mol / L was used as the electrolyte. The Bi nanoparticles-carbon fiber paper (Bi NPs-CFP) was obtained by electroreduction at a potential of -0.6 V relative to the reversible hydrogen electrode for 2 h.

[0045] Example 3

[0046] In the H-type electrolytic cell system, Nafion 115 membrane was used as the ion exchange membrane, Bi NPs-CFP prepared in Example 2 was used as the working electrode, and titanium mesh loaded with IrO2 and silver / silver chloride electrode were used as the counter electrode and reference electrode, respectively. Hydroxylamine was prepared by electrocatalytic reaction using 0.1 mol / L nitrate and 0.5 mol / L sulfuric acid as electrolyte.

[0047] A constant potential test was conducted, with the total potential set at -0.6 V relative to the reversible hydrogen electrode, and the test was performed for 1 hour. During the reaction, argon gas was introduced into the cathode electrolyte, and the gas generated by the cathode reaction was carried by the argon gas into a gas chromatograph for online monitoring of the gas content in the catalytic product. After the reaction, 0.4 mL of the cathode electrolyte was mixed with 0.1 mL of d6-DMSO, 12.5 μL of 50 wt% C2H2O3, and 0.1 mL of 6.0 mmol / L DSS, and the content of the liquid product hydroxylamine was detected by proton NMR spectroscopy. After the test, the total potential was changed sequentially to -0.7 V relative to the reversible hydrogen electrode, -0.8 V relative to the reversible hydrogen electrode, -0.9 V relative to the reversible hydrogen electrode, -1.0 V relative to the reversible hydrogen electrode, -1.1 V relative to the reversible hydrogen electrode, and -1.2 V relative to the reversible hydrogen electrode, while keeping other conditions unchanged. The results are shown in [Figure number missing]. Figure 4 and Figure 5 , Figure 4 The Faradaic efficiency of Bi NPs-CFP in Example 2 for the electrocatalytic production of hydroxylamine from nitrate at different total potentials is shown. Figure 5 The yield of Bi NPs-CFP electrocatalyzing the production of hydroxylamine from nitrate at different total potentials in Example 2 is shown.

[0048] Depend on Figure 4 and Figure 5 It is known that when Bi NPs-CFP from Example 2 is used as a catalyst and as a working electrode to electrocatalytically reduce nitrate to synthesize hydroxylamine, the Faraday efficiency is above 60% at a total potential of -0.6 to -1.2 V relative to the reversible hydrogen electrode, and the yield reaches 700 μmol / cm² / h at a total potential of -1.2 V relative to the reversible hydrogen electrode.

[0049] Example 4

[0050] The long-term cyclic catalytic stability of the Bi NPs-CFP obtained in Example 2 in the electrocatalytic reduction of nitrate to prepare hydroxylamine was tested. Under the reaction conditions of Example 3, constant current testing was conducted, with the total current set at -100 mA and constant current electrolysis lasting 5 hours. The same Bi NPs-CFP was cycled 12 times, and the working electrode potential was monitored in real time during electrolysis. After the test, the content of the liquid product hydroxylamine was detected by proton nuclear magnetic resonance spectroscopy. The results are as follows. Figure 6 As shown, by Figure 6 It can be seen that the yield of hydroxylamine remained stable after 12 cycles of testing, indicating that the supported catalyst provided by the present invention has good cycle stability.

[0051] The above description of the embodiments is only used to help understand the method of the present application and its core idea. It should be noted that, for those skilled in the art, some improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A process for the preparation of a hydroxylamine, characterized in that, The method comprises the following steps: carrying out an electrocatalytic reduction reaction of nitrate under the action of a supported catalyst to obtain hydroxylamine; the supported catalyst comprises a porous carrier and Bi nanoparticles loaded on the porous carrier by magnetron sputtering; the loading amount of the Bi nanoparticles is 0.3-0.7 mg per square centimeter; the electrocatalytic reduction reaction is carried out in an electrolytic cell system comprising a working electrode, a counter electrode, a reference electrode, an ion exchange membrane and an electrolyte; wherein the working electrode is the supported catalyst; the electrolyte is a mixed solution containing nitrate and aqueous sulfuric acid; in the electrocatalytic reduction reaction, a constant potential mode is adopted, and the total potential is-0.5 to-1.5 volts relative to the reversible hydrogen electrode.

2. The production method according to claim 1, characterized by, the porous carrier is selected from carbon fiber paper, carbon black, carbon nanotubes or graphene.

3. The preparation method according to claim 1, characterized in that, the pore size of the porous carrier is 200-500 nm.

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