A bimetallic catalyst, its preparation method and application

Abstract

The present invention belongs to the technical field of water treatment. The present invention provides a bimetallic catalyst, a preparation method thereof, and an application thereof. The catalyst of the present invention is a supported bimetallic catalyst, and the bimetallic contains noble metal Rh and non-noble metal. In the present invention, the noble metal Rh is loaded onto the carrier by an impregnation method to obtain an Rh-based metal catalyst; the Rh-based catalyst is immersed in a salt solution of the non-noble metal, and the non-noble metal is deposited on the surface of the Rh-based catalyst through in-situ hydrogenation reduction to obtain a bimetallic catalyst. Through the bimetallic active sites, the ammonia nitrogen selectivity in the process of liquid-phase catalytic hydrogenation reduction of nitrate is effectively improved. When the bimetallic catalyst prepared by the present invention is applied to the liquid-phase hydrogenation reduction of nitrate reaction, it can not only remove the main nitrogen pollutants in the water body, but also produce ammonia with industrial value, having environmental benefits and economic value.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and particularly relates to a bimetallic catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] The extensive use of chemical fertilizers and nitrogen-containing pesticides in agricultural production and the wanton discharge of high-concentration nitrogen-containing wastewater in industrial production have caused serious nitrate pollution problems. Research shows that nitrates in the body will be converted into nitrites by nitrate-reducing bacteria, causing methemoglobinemia, or forming carcinogenic substances such as nitrosamines or their compounds, carcinogenic to the digestive organs, and threatening human health.

[0003] The selective catalytic reduction of nitrates to ammonia nitrogen is a research hotspot. This method can not only achieve pollutant treatment but also resource conversion. Current research mainly focuses on the field of electrocatalysis. For example, Patent CN114540841A discloses the application of a cuprous oxide nanocatalyst in the electrocatalytic reduction of nitrates. Using a cuprous oxide electrode as the working electrode and an aqueous solution of sodium sulfate and nitrate as the electrolyte, ammonia is synthesized by electrocatalytically reducing nitrates in an electrolytic cell, and the selectivity of ammonia in the product reaches 78.9%; Patent CN115072731A discloses the application of a cobalt boride nanomaterial in the electrocatalytic reduction of nitrates. Using a cobalt boride electrode as the working electrode and an aqueous solution of potassium hydroxide and nitrate as the electrolyte, ammonia is synthesized by electrocatalytically reducing nitrates in an electrolytic cell, with a maximum ammonia production rate of 0.787 ± 0.028 mmol·h -1 ·cm -2 , and a maximum Faraday efficiency of 94.00 ± 1.67%. It can be seen that in the process of electrocatalytic reduction of nitrates, it is inevitable to add an electrolyte solution, introducing new compounds.

[0004] The liquid-phase hydrogenation reduction technology is to directly reduce the water containing pollutants by introducing a hydrogen source such as hydrogen, which has the characteristics of being green, efficient, and free of secondary pollution, and is an environment-friendly technology. However, at present, the products of liquid-phase hydrogenation reduction of nitrates are mostly nitrogen, and the selectivity of ammonia nitrogen is relatively low. Research shows that Rh-based catalysts have a high selectivity for ammonia nitrogen. The addition of some non-precious metals may be able to change the electronic structure of Rh and promote the production of ammonia nitrogen, but there is less research in this direction at present.

[0005] Therefore, the research and development of a bimetallic catalyst to improve the selectivity of ammonia nitrogen in the process of liquid-phase hydrogenation reduction of nitrates and convert the pollutant nitrate into industrial raw material ammonia through bimetallic active sites has important environmental benefits and economic value. Summary of the Invention

[0006] The purpose of the present invention is to provide a bimetallic catalyst, a preparation method thereof, and an application thereof in view of the deficiencies of the prior art.

[0007] To achieve the above-mentioned invention object, the present invention provides the following technical solutions:

[0008] The present invention provides a preparation method of a bimetallic catalyst, comprising the following steps:

[0009] 1) After impregnating the carrier and the salt solution containing Rh 3+ , successively passing through evaporation to dryness, drying, calcination and reduction treatments to obtain a Rh-based catalyst;

[0010] 2) Immersing the Rh-based catalyst into the salt solution of a non-noble metal and performing reduction in a hydrogen atmosphere to obtain a bimetallic catalyst.

[0011] Preferably, the carrier in step 1) is one or more of Al2O3, SiO2, CeO2, TiO2, carbon nanotubes and ordered mesoporous carbon materials; the salt solution containing Rh 3+ is one or more of Rh(NO3)3, RhCl3 and (NH4)3RhCl6.

[0012] Preferably, the concentration of the salt solution containing Rh 3+ in step 1) is 0.1 - 0.5 mg / mL, and the mass-volume ratio of the carrier to the salt solution containing Rh 3+ is 50 - 200 mg: 10 - 20 mL.

[0013] Preferably, the impregnation time in step 1) is 1 - 3 h; the evaporation temperature is 70 - 90 °C, and the evaporation time is 1 - 2 h;

[0014] the drying temperature in step 1) is 90 - 120 °C, and the drying time is 1 - 2 h;

[0015] the calcination temperature in step 1) is 200 - 400 °C, and the calcination time is 2 - 4 h;

[0016] the reduction treatment atmosphere in step 1) is a hydrogen atmosphere, the reduction treatment temperature is 200 - 400 °C, and the reduction treatment time is 1 - 2 h.

[0017] Preferably, the salt solution of the non-noble metal in step 2) is Cu(NO3)2; the concentration of the salt solution of the non-noble metal is 10 - 50 mg / L;

[0018] the mass-volume ratio of the Rh-based catalyst to the salt solution of the non-noble metal in step 2) is 50 - 200 mg: 100 - 200 mL.

[0019] Preferably, the reduction time in step 2) is 1 - 2 h, the reduction temperature is 200 - 400 °C, and the hydrogen flow rate is 20 - 100 mL / min.

[0020] The present invention also provides a bimetallic catalyst prepared by the preparation method of the bimetallic catalyst. In the bimetallic catalyst, the bimetal comprises a noble metal Rh and a non-noble metal, and the non-noble metal is Cu.

[0021] Preferably, in the bimetallic catalyst, the loading amount of the noble metal Rh is 1 - 5%, and the loading amount of the non-noble metal is 1 - 5%.

[0022] The present invention also provides the application of the bimetallic catalyst in the liquid-phase hydrogenation reduction of nitrate. The bimetallic catalyst, nitrate solution and hydrogen are subjected to a catalytic reduction reaction.

[0023] Preferably, in the catalytic reduction reaction, the mass concentration of the bimetallic catalyst is 0.05 - 0.15 g / L; the concentration of the nitrate solution is 1.0 - 2.5 mmol / L; the hydrogen flow rate is 100 - 200 mL / min; and the catalytic reduction reaction time is 1 - 3 h.

[0024] The beneficial effects of the present invention include the following points:

[0025] 1) The present invention uses an in-situ hydrogenation reduction method to load a non-noble metal onto a Rh-based catalyst, enabling the non-noble metal to be preferentially deposited on the noble metal Rh. The synthesized metal particles have uniform sizes, promoting the dispersion of the non-noble metal; the non-noble metal and the noble metal Rh have a stronger interaction, changing the electronic structure of Rh and improving the ammonia-nitrogen selectivity in the liquid-phase hydrogenation reduction of nitrate.

[0026] 2) The preparation method of the bimetallic catalyst of the present invention is simple and easy to operate. When the prepared bimetallic catalyst is used in the liquid-phase hydrogenation reduction of nitrate, it has a high catalytic reduction efficiency for nitrate in water, can convert the pollutant nitrate into an important industrial raw material ammonia, and has good environmental benefits and economic value. Description of the Drawings

[0027] Figure 1 TEM images of Rh5@Cu3 / Al2O3 prepared in Example 1, Rh5 / Al2O3 prepared in Comparative Example 1, Cu3 / Al2O3 prepared in Comparative Example 2, and Rh5Cu3 / Al2O3 prepared in Comparative Example 3, where a is Example 1, b is Comparative Example 1, c is Comparative Example 2, and d is Comparative Example 3;

[0028] Figure 2XRD patterns of Rh5@Cu3 / Al2O3 prepared in Example 1, Rh5 / Al2O3 prepared in Comparative Example 1, Cu3 / Al2O3 prepared in Comparative Example 2, and Rh5Cu3 / Al2O3 prepared in Comparative Example 3;

[0029] Figure 3 XPS spectra of Rh5@Cu3 / Al2O3 prepared in Example 1, Rh5 / Al2O3 prepared in Comparative Example 1, Cu3 / Al2O3 prepared in Comparative Example 2, and Rh5Cu3 / Al2O3 prepared in Comparative Example 3, where a is the peak of Rh 3d and b is the peak of Cu 2p;

[0030] Figure 4 Curves of the liquid-phase hydrogenation reduction of nitrate reaction for Rh5@Cu3 / Al2O3 prepared in Example 1, Rh5 / Al2O3 prepared in Comparative Example 1, Cu3 / Al2O3 prepared in Comparative Example 2, and Rh5Cu3 / Al2O3 prepared in Comparative Example 3;

[0031] Figure 5 Nitrogen balance diagram of the liquid-phase hydrogenation reduction of nitrate reaction for Rh5@Cu3 / Al2O3 prepared in Example 1;

[0032] Figure 6 Cycle diagram of the liquid-phase hydrogenation reduction of nitrate reaction for Rh5@Cu3 / Al2O3 prepared in Example 1;

[0033] Figure 7 Curves of the liquid-phase hydrogenation reduction of nitrate reaction for different dosages of Rh5@Cu3 / Al2O3 prepared in Example 1;

[0034] Figure 8 Curves of the liquid-phase hydrogenation reduction of nitrate reaction for Rh5@Cu3 / Al2O3 prepared in Example 1 at different sodium nitrate concentrations. Detailed implementation mode

[0035] The present invention provides a preparation method of a bimetallic catalyst, comprising the following steps:

[0036] 1) After impregnating the carrier and the salt solution containing Rh 3+ , successively through evaporation to dryness, drying, calcination and reduction treatments, an Rh-based catalyst is obtained;

[0037] 2) Immerse the Rh-based catalyst into the salt solution of a non-noble metal and carry out reduction in a hydrogen atmosphere to obtain a bimetallic catalyst.

[0038] In step 1) of the present invention, the carrier is preferably one or more of Al2O3, SiO2, CeO2, TiO2, carbon nanotubes and ordered mesoporous carbon materials; the Rh-containing3+ The salt solution is preferably one or more of Rh(NO3)3, RhCl3, and (NH4)3RhCl6.

[0039] The Rh-containing 3+ salt solution in step 1) of the present invention preferably has a concentration of 0.1 - 0.5 mg / mL, more preferably 0.2 - 0.4 mg / mL, and even more preferably 0.3 - 0.35 mg / mL; the mass-volume ratio of the carrier to the Rh-containing 3+ salt solution is preferably 50 - 200 mg : 10 - 20 mL, more preferably 80 - 180 mg : 12 - 18 mL, and even more preferably 100 - 150 mg : 14 - 15 mL.

[0040] The impregnation time in step 1) of the present invention is preferably 1 - 3 h, more preferably 1.5 - 2.5 h, and even more preferably 1.8 - 2 h; the evaporation temperature is preferably 70 - 90 °C, more preferably 75 - 85 °C, and even more preferably 78 - 82 °C; the evaporation time is preferably 1 - 2 h, more preferably 1.2 - 1.8 h, and even more preferably 1.4 - 1.6 h;

[0041] The drying temperature in step 1) is preferably 90 - 120 °C, more preferably 95 - 115 °C, and even more preferably 100 - 105 °C; the drying time is preferably 1 - 2 h, more preferably 1.2 - 1.8 h, and even more preferably 1.4 - 1.6 h.

[0042] The calcination temperature in step 1) of the present invention is preferably 200 - 400 °C, more preferably 250 - 350 °C, and even more preferably 280 - 320 °C; the calcination time is preferably 2 - 4 h, more preferably 2.5 - 3.5 h, and even more preferably 3 h.

[0043] The atmosphere for the reduction treatment in step 1) of the present invention is preferably a hydrogen atmosphere, the reduction temperature is preferably 200 - 400 °C, more preferably 250 - 350 °C, and even more preferably 280 - 320 °C; the reduction time is preferably 1 - 2 h, more preferably 1.2 - 1.8 h, and even more preferably 1.4 - 1.6 h.

[0044] The non-noble metal salt solution in step 2) of the present invention is preferably Cu(NO3)2; the concentration of the non-noble metal salt solution is preferably 10 - 50 mg / L, more preferably 20 - 40 mg / L, and even more preferably 25 - 30 mg / L.

[0045] In step 2) of the present invention, the mass-volume ratio of the Rh-based catalyst to the non-precious metal salt solution is preferably 50-200 mg: 100-200 mL, more preferably 100-180 mg: 120-180 mL, and even more preferably 130-160 mg: 140-160 mL.

[0046] In step 2) of the present invention, the reduction time is preferably 1-2 h, more preferably 1.2-1.8 h, and even more preferably 1.4-1.6 h; the reduction temperature is preferably 200-400 °C, more preferably 250-350 °C, and even more preferably 280-320 °C; the hydrogen flow rate is preferably 20-100 mL / min, more preferably 30-80 mL / min, and even more preferably 50-60 mL / min.

[0047] After reduction in step 2) of the present invention, drying is preferably carried out. The drying temperature is preferably 30-60 °C, more preferably 40-55 °C, and even more preferably 45-50 °C; the drying time is preferably 1-2 h, more preferably 1.3-1.8 h, and even more preferably 1.5 h.

[0048] The present invention also provides a bimetallic catalyst prepared by the preparation method of the bimetallic catalyst.

[0049] In the bimetallic catalyst of the present invention, the bimetal preferably comprises a noble metal Rh and a non-precious metal, and the non-precious metal is preferably Cu.

[0050] In the bimetallic catalyst of the present invention, the loading amount of the noble metal Rh is preferably 1-5%, more preferably 2-4%, and even more preferably 3%; the loading amount of the non-precious metal is preferably 1-5%, more preferably 2-4%, and even more preferably 3%.

[0051] The present invention also provides the application of the bimetallic catalyst in the liquid-phase hydrogenation reduction of nitrate. The bimetallic catalyst, nitrate solution and hydrogen are subjected to a catalytic reduction reaction.

[0052] In the catalytic reduction reaction of the present invention, the mass concentration of the bimetallic catalyst is preferably 0.05-0.15 g / L, more preferably 0.08-0.13 g / L, and even more preferably 0.10-0.12 g / L; the nitrate solution is preferably a sodium nitrate solution, and the concentration of the nitrate solution is preferably 1.0-2.5 mmol / L, more preferably 1.2-2.2 mmol / L, and even more preferably 1.5-2.0 mmol / L.

[0053] Before the catalytic reduction reaction of the present invention, it is preferably to introduce nitrogen to remove oxygen in the nitrate solution. The flow rate of the nitrogen is preferably 30-80 mL / min, more preferably 40-70 mL / min, and still more preferably 50-60 mL / min. The time for introducing nitrogen is preferably 10-60 min, more preferably 20-50 min, and still more preferably 30-40 min.

[0054] The flow rate of the hydrogen in the present invention is preferably 100-200 mL / min, more preferably 120-180 mL / min, and still more preferably 140-160 mL / min. The time for the catalytic reduction reaction is preferably 1-3 h, more preferably 1.5-2.5 h, and still more preferably 2 h.

[0055] The technical solutions provided by the present invention will be described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention. Example 1

[0056] 92 mg of the carrier Al2O3 was added to 10 mL of a RhCl3 solution with a concentration of 0.5 mg / mL. After impregnation for 2 h, it was evaporated to dryness for 1 h under a 90 °C water bath condition, dried in an oven at 100 °C for 2 h in sequence, calcined at 300 °C for 4 h, and reduced at 300 °C in a hydrogen atmosphere for 2 h to obtain the Rh / Al2O3 catalyst. 97 mg of the Rh / Al2O3 catalyst was immersed in 100 mL of a Cu(NO3)2 solution with a concentration of 30 mg / L, hydrogen was introduced at a flow rate of 60 mL / min, reduced at 300 °C for 2 h, and dried at 60 °C for 1 h to obtain the bimetallic catalyst Rh5@Cu3 / Al2O3.

[0057] In the bimetallic catalyst Rh5@Cu3 / Al2O3 of this example, the carrier is Al2O3, the loading amount of the noble metal Rh (the loading amount is the mass fraction of the noble metal Rh relative to the total mass of the bimetallic catalyst Rh5@Cu3 / Al2O3) is 5%, and the loading amount of the non-noble metal Cu is 3%.

[0058] 20 mg of the bimetallic catalyst Rh5@Cu3 / Al2O3 was added to 200 mL of a sodium nitrate solution with a concentration of 1.5 mmol / L. Nitrogen was introduced at a flow rate of 50 mL / min for 30 min to remove oxygen in the sodium nitrate solution, and then hydrogen was introduced at a flow rate of 100 mL / min for catalytic reduction reaction for 2 h. After the reaction was completed, a sample was taken, filtered through a 0.22 μm filter membrane, and the ammonia nitrogen concentration after the reaction was measured by the Nessler reagent colorimetric method. Comparative Example 1

[0059] 95 mg of the carrier Al2O3 was added to 10 mL of an RhCl3 solution with a concentration of 0.5 mg / mL. After impregnation for 2 h, it was evaporated to dryness in a water bath at 90 °C for 1 h, successively dried in an oven at 100 °C for 2 h, calcined at 300 °C for 4 h, and reduced in a hydrogen atmosphere at 300 °C for 2 h to obtain the single-metal catalyst Rh5 / Al2O3.

[0060] 20 mg of the single-metal catalyst Rh5 / Al2O3 was added to 200 mL of a 1.5 mmol / L sodium nitrate solution. Nitrogen was passed through at a flow rate of 50 mL / min for 30 min to remove the oxygen in the sodium nitrate solution, and then hydrogen was passed through at a flow rate of 100 mL / min for a catalytic reduction reaction for 2 h. After the reaction was completed, a sample was taken, filtered through a 0.22 μm filter membrane, and the ammonia nitrogen concentration after the reaction was measured by the Nessler reagent colorimetric method. Comparative Example 2

[0061] 97 mg of the carrier Al2O3 was added to 10 mL of a Cu(NO3)2 solution with a concentration of 0.3 mg / mL. After impregnation for 2 h, it was evaporated to dryness in a water bath at 90 °C for 1 h, successively dried in an oven at 100 °C for 2 h, calcined at 300 °C for 4 h, and reduced in a hydrogen atmosphere at 500 °C for 2 h to obtain the single-metal catalyst Cu3 / Al2O3.

[0062] 20 mg of the single-metal catalyst Cu3 / Al2O3 was added to 200 mL of a 1.5 mmol / L sodium nitrate solution. Nitrogen was passed through at a flow rate of 50 mL / min for 30 min to remove the oxygen in the sodium nitrate solution, and then hydrogen was passed through at a flow rate of 100 mL / min for a catalytic reduction reaction for 2 h. After the reaction was completed, a sample was taken, filtered through a 0.22 μm filter membrane, and the ammonia nitrogen concentration after the reaction was measured by the Nessler reagent colorimetric method. Comparative Example 3

[0063] 92 mg of the carrier Al2O3 was added to a mixed solution containing 10 mL of a 0.5 mg / mL RhCl3 solution and 10 mL of a 0.3 mg / mL Cu(NO3)2 solution. After impregnation for 2 h, it was evaporated to dryness in a water bath at 90 °C for 1 h, successively dried in an oven at 100 °C for 2 h, calcined at 300 °C for 4 h, and reduced in a hydrogen atmosphere at 500 °C for 2 h to obtain the catalyst Rh5Cu3 / Al2O3.

[0064] 20 mg of the catalyst Rh5Cu3 / Al2O3 was added to 200 mL of a 1.5 mmol / L sodium nitrate solution. Nitrogen was introduced at a flow rate of 50 mL / min for 30 min to remove the oxygen in the sodium nitrate solution. Then, hydrogen was introduced at a flow rate of 100 mL / min for a catalytic reduction reaction for 2 h. After the reaction was completed, a sample was taken, filtered through a 0.22 μm filter membrane, and the ammonia nitrogen concentration after the reaction was measured by the Nessler reagent colorimetric method.

[0065] The TEM images of Rh5@Cu3 / Al2O3 prepared in Example 1, Rh5 / Al2O3 prepared in Comparative Example 1, Cu3 / Al2O3 prepared in Comparative Example 2, and Rh5Cu3 / Al2O3 prepared in Comparative Example 3 are as Figure 1 shown. From Figure 1 it can be seen that the average particle sizes of the catalysts Rh5@Cu3 / Al2O3, Rh5 / Al2O3, Cu3 / Al2O3, and Rh5Cu3 / Al2O3 are 2.43 nm, 2.77 nm, 5.92 nm, and 5.68 nm, respectively. By comparing Figure 1 a - 1d, it can be seen that by using the in-situ hydrogenation reduction method to load Cu onto the surface of the Rh / Al2O3 catalyst, Cu can be preferentially deposited on the Rh surface, promoting the dispersion of Cu, and the prepared catalyst has a uniform particle size. However, the catalyst synthesized by the co-impregnation method has a larger particle size and a lower metal dispersion.

[0066] The XRD patterns of Rh5@Cu3 / Al2O3 prepared in Example 1, Rh5 / Al2O3 prepared in Comparative Example 1, Cu3 / Al2O3 prepared in Comparative Example 2, and Rh5Cu3 / Al2O3 prepared in Comparative Example 3 are as Figure 2 shown. From Figure 2 it can be observed that the characteristic diffraction peaks of Rh and Cu. Compared with the catalyst Rh5Cu3 / Al2O3 prepared by the co-impregnation method, the characteristic peaks of Rh and Cu in Rh5@Cu3 / Al2O3 prepared in Example 1 are smaller, indicating that the synthesized nanoparticles have a smaller particle size and a more uniform dispersion.

[0067] The XPS patterns of Rh5@Cu3 / Al2O3 prepared in Example 1, Rh5 / Al2O3 prepared in Comparative Example 1, Cu3 / Al2O3 prepared in Comparative Example 2, and Rh5Cu3 / Al2O3 prepared in Comparative Example 3 are as Figure 3 shown, where Figure a is the peak of Rh 3d and Figure b is the peak of Cu2p. From Figure 3It can be seen that in the XPS spectra of the bimetallic catalysts Rh5@Cu3 / Al2O3 and Rh5Cu3 / Al2O3, the binding energy of Cu shifts towards the high field, and the binding energy of Rh shifts towards the low field, indicating a strong interaction between Cu and Rh and an electron transfer from Cu to Rh. Moreover, the shift of the catalyst Rh5@Cu3 / Al2O3 is greater, indicating a stronger interaction between the two metals in the catalyst prepared in Example 1.

[0068] The curves of the liquid-phase hydrogenation reduction of nitrate reaction for Rh5@Cu3 / Al2O3 prepared in Example 1, Rh5 / Al2O3 prepared in Comparative Example 1, Cu3 / Al2O3 prepared in Comparative Example 2, and Rh5Cu3 / Al2O3 prepared in Comparative Example 3 are as Figure 4 shown. From Figure 4 it can be seen that the catalytic activity of the bimetallic catalyst Rh5@Cu3 / Al2O3 is high, and the effect of reducing nitrate is the best, followed by Rh5Cu3 / Al2O3. This is mainly because Rh and Cu in Rh5@Cu3 / Al2O3 have a stronger interaction and a higher electron transfer efficiency. While Rh5 / Al2O3 and Cu3 / Al2O3 have almost no catalytic activity. Sodium nitrate first undergoes an oxidation-reduction reaction with Cu on the catalyst surface, sodium nitrate is converted into sodium nitrite, Cu is converted into copper ions, sodium nitrite is transferred to the Rh surface and is further reduced, and copper ions are reduced to Cu again under the action of active hydrogen on the Rh surface, reaching a dynamic equilibrium.

[0069] The nitrogen balance diagram of the liquid-phase hydrogenation reduction of nitrate reaction for the bimetallic catalyst Rh5@Cu3 / Al2O3 in Example 1 is as Figure 5 shown. From Figure 5 it can be seen that sodium nitrate is rapidly reduced to ammonia nitrogen, and the selectivity of ammonia nitrogen is 100%, and the concentration of the intermediate product sodium nitrite is relatively low. The non-conservation in the first 20 min may be due to the existence of adsorbed sodium nitrate or sodium nitrite that is not detected. Example 2

[0070] The bimetallic catalyst Rh5@Cu3 / Al2O3 after the reaction in Example 1 was filtered and washed, and the catalytic reduction reaction was repeated for 5 cycles. Other conditions were the same as those in Example 1, and the selectivity of ammonia nitrogen after each cycle reaction was determined by the Nessler reagent colorimetric method.

[0071] The cycle diagram of the liquid-phase hydrogenation reduction of nitrate reaction for Rh5@Cu3 / Al2O3 in this example is as Figure 6 shown. From Figure 6It can be seen that after 5 cycles, the removal rate of nitrate within 2 h of the reaction is 100%, and the selectivity for ammonia nitrogen as the reduction product of nitrate is 100%. This indicates that after 5 cycles, the bimetallic catalyst Rh5@Cu3 / Al2O3 prepared in Example 1 still retains high catalytic activity and stability. Example 3

[0072] The dosages of the bimetallic catalyst Rh5@Cu3 / Al2O3 in Example 1 were adjusted to 10 mg, 15 mg, 25 mg, and 30 mg respectively, and other conditions were the same as those in Example 1.

[0073] After the catalytic reduction reaction, the ammonia nitrogen selectivity of the bimetallic catalyst Rh5@Cu3 / Al2O3 with different dosages of 10 mg (0.050 g·L -1 ), 15 mg (0.075 g·L -1 ), 20 mg (0.100 g·L -1 ), 25 mg (0.125 g·L -1 ), and 30 mg (0.150 g·L -1 ) for the liquid-phase hydrogenation reduction of nitrate reaction was measured respectively. A curve was plotted to obtain the curve graph of the liquid-phase hydrogenation reduction of nitrate reaction with different dosages of Rh5@Cu3 / Al2O3, as shown in Figure 7 shown. It can be seen from Figure 7 that within the range of 10 - 30 mg of the dosage of the bimetallic catalyst Rh5@Cu3 / Al2O3 of the present invention, nitrate can be completely removed within 2 h of the reaction. Example 4

[0074] The concentrations of the sodium nitrate solution in Example 1 were adjusted to 1.0 mmol / L, 2.0 mmol / L, and 2.5 mmol / L respectively, and other conditions were the same as those in Example 1.

[0075] After the catalytic reduction reaction, the ammonia nitrogen selectivity of the liquid-phase hydrogenation reduction of nitrate reaction at different sodium nitrate concentrations was measured respectively. A curve was plotted to obtain the curve graph of the liquid-phase hydrogenation reduction of nitrate reaction by the bimetallic catalyst Rh5@Cu3 / Al2O3 at different sodium nitrate concentrations, as shown in Figure 8 shown. It can be seen from Figure 8 that within the range of 1.0 - 2.5 mmol / L of the sodium nitrate concentration, the bimetallic catalyst Rh5@Cu3 / Al2O3 of the present invention can completely remove nitrate within 2 h of the reaction. This indicates that the bimetallic catalyst Rh5@Cu3 / Al2O3 of the present invention has high catalytic activity within a relatively wide range of nitrate concentrations. Example 5

[0076] Adjust the dosage of Al2O3 in Example 1 to 94 mg, and adjust the concentration of the Cu(NO3)2 solution to 10 mg / L. Keep other conditions the same as in Example 1 to obtain the bimetallic catalyst Rh5@Cu1 / Al2O3.

[0077] In the bimetallic catalyst Rh5@Cu1 / Al2O3 of this example, the carrier is Al2O3, the loading amount of Rh is 5%, and the loading amount of Cu is 1%.

[0078] Replace the bimetallic catalyst Rh5@Cu3 / Al2O3 in Example 1 with the bimetallic catalyst Rh5@Cu1 / Al2O3, and carry out the catalytic reduction reaction. Keep other conditions the same as in Example 1.

[0079] In 2 h, the removal rate of nitrate by the bimetallic catalyst Rh5@Cu1 / Al2O3 of this example is 100%, and the selectivity for ammonia nitrogen is 100%. Example 6

[0080] Adjust the dosage of Al2O3 in Example 1 to 90 mg, and adjust the concentration of the Cu(NO3)2 solution to 50 mg / L. Keep other conditions the same as in Example 1 to obtain the bimetallic catalyst Rh5@Cu5 / Al2O3.

[0081] In the bimetallic catalyst Rh5@Cu5 / Al2O3 of this example, the carrier is Al2O3, the loading amount of Rh is 5%, and the loading amount of Cu is 5%.

[0082] Replace the bimetallic catalyst Rh5@Cu3 / Al2O3 in Example 1 with the bimetallic catalyst Rh5@Cu5 / Al2O3, and carry out the catalytic reduction reaction. Keep other conditions the same as in Example 1.

[0083] In 2 h, the removal rate of nitrate by the bimetallic catalyst Rh5@Cu5 / Al2O3 of this example is 72%, and the selectivity for ammonia nitrogen is 100%. The higher loading amount of Cu exposes less Rh, which affects the conversion of nitrite to ammonia nitrogen. Example 7

[0084] Adjust the dosage of Al2O3 in Example 1 to 96 mg, and adjust the concentration of the RhCl3 solution to 0.1 mg / mL. Keep other conditions the same as in Example 1 to obtain the bimetallic catalyst Rh1@Cu3 / Al2O3.

[0085] In the bimetallic catalyst Rh1@Cu3 / Al2O3 of this example, the carrier is Al2O3, the loading amount of Rh is 1%, and the loading amount of Cu is 3%.

[0086] Replace the bimetallic catalyst Rh5@Cu3 / Al2O3 in Example 1 with the bimetallic catalyst Rh1@Cu3 / Al2O3 and conduct the catalytic reduction reaction. Other conditions are the same as those in Example 1.

[0087] In the bimetallic catalyst Rh1@Cu3 / Al2O3 of this example, the removal rate of nitrate is 86% and the selectivity for ammonia nitrogen is 100% within 2 h. Less exposed Rh affects the conversion of nitrite to ammonia nitrogen. Example 8

[0088] Adjust the dosage of Al2O3 in Example 1 to 94 mg and the concentration of RhCl3 solution to 0.3 mg / mL. Other conditions are the same as those in Example 1 to obtain the bimetallic catalyst Rh3@Cu3 / Al2O3.

[0089] In the bimetallic catalyst Rh3@Cu3 / Al2O3 of this example, the carrier is Al2O3, the loading amount of Rh is 3%, and the loading amount of Cu is 3%.

[0090] Replace the bimetallic catalyst Rh5@Cu3 / Al2O3 in Example 1 with the bimetallic catalyst Rh3@Cu3 / Al2O3 and conduct the catalytic reduction reaction. Other conditions are the same as those in Example 1.

[0091] In the bimetallic catalyst Rh3@Cu3 / Al2O3 of this example, the removal rate of nitrate is 100% and the selectivity for ammonia nitrogen is 100% within 2 h. Example 9

[0092] Adjust the Cu(NO3)2 solution in Example 1 to an AgNO3 solution. Other conditions are the same as those in Example 1 to obtain the bimetallic catalyst Rh5@Ag3 / Al2O3.

[0093] In the bimetallic catalyst Rh5@Ag3 / Al2O3 of this example, the carrier is Al2O3, the loading amount of Rh is 5%, and the loading amount of Ag is 3%.

[0094] Replace the bimetallic catalyst Rh5@Cu3 / Al2O3 in Example 1 with the bimetallic catalyst Rh5@Ag3 / Al2O3 and conduct the catalytic reduction reaction. Other conditions are the same as those in Example 1.

[0095] In the bimetallic catalyst Rh5@Ag3 / Al2O3 of this example, the removal rate of nitrate is 100% and the selectivity for ammonia nitrogen is 100% within 2 h. Example 10

[0096] The Cu(NO3)2 solution in Example 1 was adjusted to a HAuCl4 solution, and other conditions were the same as in Example 1, obtaining the bimetallic catalyst Rh5@Au3 / Al2O3.

[0097] In the bimetallic catalyst Rh5@Au3 / Al2O3 of this example, the carrier is Al2O3, the loading amount of Rh is 5%, and the loading amount of Au is 3%.

[0098] The bimetallic catalyst Rh5@Cu3 / Al2O3 in Example 1 was replaced with the bimetallic catalyst Rh5@Au3 / Al2O3 for the catalytic reduction reaction, and other conditions were the same as in Example 1.

[0099] In this example, for the bimetallic catalyst Rh5@Au3 / Al2O3, within 2 h, the removal rate of nitrate was 100%, and the selectivity for ammonia nitrogen was 100%. Example 11

[0100] The carrier Al2O3 in Example 1 was adjusted to the carrier CeO2, and other conditions were the same as in Example 1, obtaining the bimetallic catalyst Rh5@Cu3 / CeO2.

[0101] In the bimetallic catalyst Rh5@Cu3 / CeO2 of this example, the carrier is CeO2, the loading amount of Rh is 5%, and the loading amount of Au is 3%.

[0102] The bimetallic catalyst Rh5@Cu3 / Al2O3 in Example 1 was replaced with the bimetallic catalyst Rh5@Cu3 / CeO2 for the catalytic reduction reaction, and other conditions were the same as in Example 1.

[0103] In this example, for the bimetallic catalyst Rh5@Cu3 / CeO2, within 2 h, the removal rate of nitrate was 100%, and the selectivity for ammonia nitrogen was 100%. It shows that the bimetallic catalyst prepared with a metal oxide as the carrier for the liquid-phase hydrogenation reduction of nitrate has good removal effect and high selectivity for ammonia nitrogen. Example 12

[0104] The carrier Al2O3 in Example 1 was adjusted to the carrier carbon nanotube CNT, and other conditions were the same as in Example 1, obtaining the bimetallic catalyst Rh5@Cu3 / CNT.

[0105] In the bimetallic catalyst Rh5@Cu3 / CNT of this example, the carrier is CNT, the loading amount of Rh is 5%, and the loading amount of Au is 3%.

[0106] The bimetallic catalyst Rh5@Cu3 / Al2O3 in Example 1 was replaced with the bimetallic catalyst Rh5@Cu3 / CNT for the catalytic reduction reaction, and other conditions were the same as in Example 1.

[0107] For the bimetallic catalyst Rh5@Cu3 / CNT of this embodiment, the nitrate removal rate is 100% and the ammonia nitrogen selectivity is 100% within 2 h. It shows that the bimetallic catalyst prepared by using a carbon-based material as the carrier for liquid-phase hydrogenation reduction of nitrate has good removal effect and high ammonia nitrogen selectivity.

[0108] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. Application of a bimetallic catalyst in liquid-phase hydrogenation reduction of nitrate, characterized in that, Perform a catalytic reduction reaction on a bimetallic catalyst, a nitrate solution, and hydrogen; The preparation method of the bimetallic catalyst comprises the following steps: 1) After impregnating the carrier with a salt solution containing Rh 3+ , it is successively subjected to evaporation to dryness, drying, calcination, and reduction treatments to obtain an Rh-based catalyst; 2) Immerse the Rh-based catalyst in a salt solution of a non-noble metal, and perform reduction in a hydrogen atmosphere to obtain a bimetallic catalyst; Step 1) The concentration of the Rh-containing 3+ salt solution is 0.1 to 0.5 mg / mL, and the mass-volume ratio of the carrier to the Rh-containing 3+ salt solution is 50 to 200 mg: 10 to 20 mL; In step 2), the salt solution of the non-noble metal is Cu(NO3)2; the concentration of the salt solution of the non-noble metal is 10-50 mg / L; the mass-volume ratio of the Rh-based catalyst to the salt solution of the non-noble metal is 50-200 mg: 100-200 mL.

2. The application according to claim 1, wherein Step 1) The carrier is one or more of Al2O3, SiO2, CeO2, TiO2, carbon nanotubes, and ordered mesoporous carbon materials; the Rh-containing 3+ salt solution is one or more of Rh(NO3)3, RhCl3, and (NH4)3RhCl6.

3. The application according to claim 2, wherein In step 1), the impregnation time is 1-3 h; the evaporation temperature is 70-90 °C, and the evaporation time is 1-2 h; The drying temperature is 90-120 °C, and the drying time is 1-2 h; The calcination temperature is 200-400 °C, and the calcination time is 2-4 h; The atmosphere of the reduction treatment is a hydrogen atmosphere, the reduction treatment temperature is 200-400 °C, and the reduction treatment time is 1-2 h.

4. The application according to claim 3, characterized in that In step 2), the reduction time is 1-2 h, the reduction temperature is 200-400 °C, and the hydrogen flow rate is 20-100 mL / min.

5. The application according to claim 4, characterized in that, In the bimetallic catalyst, the loading amount of the noble metal Rh is 1-5%, and the loading amount of the non-noble metal is 1-5%.

6. The application according to claim 5, wherein In the catalytic reduction reaction, the mass concentration of the bimetallic catalyst is 0.05-0.15 g / L; the concentration of the nitrate solution is 1.0-2.5 mmol / L; the hydrogen flow rate is 100-200 mL / min; the catalytic reduction reaction time is 1-3 h.

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