A three-component catalyst for removing ammonia nitrogen and its application in catalytic wet air oxidation

Abstract

A three-component catalyst for removing ammonia nitrogen and its application in catalytic wet oxidation. The catalyst includes a heterogeneous catalyst, a homogeneous catalyst and a pH buffer. The application method is as follows: first, the heterogeneous catalyst is loaded into the catalytic wet oxidation reactor. After the wastewater is fed into the catalytic wet oxidation reactor, the homogeneous catalyst is added to the wastewater in the catalytic wet oxidation reactor, then the pH buffer is added, and oxygen is introduced to carry out the catalytic wet oxidation reaction to obtain recycled alkaline water. The catalyst of the present invention has a wide range of raw material sources, low cost, high ammonia nitrogen removal rate, and realizes the rapid oxidation and degradation of ammonia nitrogen in the gaseous state under alkaline conditions. The method of the present invention has a simple process and low cost, and is suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to a catalyst and its application in catalytic wet oxidation, and particularly to a three-component catalyst for removing ammonia nitrogen and its application in catalytic wet oxidation. Background Art

[0002] Ammonia nitrogen is considered to be one of the most important pollutants in the water environment. With the rapid development and growth of industries such as petrochemical and energy regeneration in China, the amount of high-ammonia-nitrogen wastewater generated is gradually increasing. Therefore, developing new technologies to treat high-ammonia-nitrogen wastewater by economical and effective means has become an important research topic for current environmental protection workers and has received great attention from industry insiders. The general formation of ammonia-nitrogen wastewater is caused by the coexistence of ammonia water and inorganic ammonia, and there are mainly two components: one is ammonia nitrogen formed by ammonia water, and the other is ammonia nitrogen formed by inorganic ammonia, mainly ammonium sulfate, ammonium chloride, etc. When the ammonia nitrogen in the wastewater dissolves into the water body, it will consume a large amount of oxygen in the water, easily cause damage to the water body, and pose a hazard to the ecological environment.

[0003] Treatment methods for high-ammonia-nitrogen wastewater include stripping method, zeolite deammonification method, reverse osmosis membrane separation technology, MAP precipitation method, chemical oxidation method, A / O, two-stage activated sludge method, strong oxidation aerobic biological treatment, short-cut nitrification and denitrification method, etc. However, whether it is stripping, stripping + A / O or stripping + chemical precipitation, it is inseparable from a pretreatment process with high investment and high operating costs. Therefore, advanced oxidation technologies with higher treatment efficiency have emerged. Among them, catalytic wet oxidation (CWAO) technology is a representative of advanced oxidation technologies. The reaction mechanism of CWAO is that under high temperature and high pressure conditions, oxygen in the air generates strongly oxidizing ·OH free radicals on the surface of the catalyst, directly oxidizing ammonia nitrogen in the wastewater into nitrogen gas. During this process, no solid waste is generated, and no secondary pollution waste gas such as NO x is produced. At the same time, the oxidation reaction heat can be fully utilized during the reaction process to achieve self-thermal balance, and the energy saving is good. CWAO has attracted much attention due to its advantages such as high removal rate, low operating cost, strong adaptability, no secondary pollution, simple process, and small floor area.

[0004] However, at present, the removal of ammonia nitrogen by catalytic wet oxidation is affected by various factors such as pH and catalytic active components, and the removal rate is not high. Although noble metal catalysts have a certain removal effect on ammonia nitrogen, the cost of noble metal catalysts is too high, which limits the application of catalytic wet oxidation technology in ammonia nitrogen treatment. Therefore, it is very meaningful to develop a cheap catalyst to achieve efficient removal of ammonia-nitrogen wastewater.

[0005] CN114409166A discloses a catalyst for catalytic wet oxidation treatment of ammonia-nitrogen wastewater. However, this catalyst uses noble metals as active components, not only the catalyst cost is high, but also the ammonia nitrogen removal effect is limited by the pH value of the solution.

[0006] CN115487808A discloses a wet oxidation catalyst, its preparation method and application, as well as a method for treating imidazole-containing wastewater by wet oxidation. However, the preparation conditions of the catalyst are relatively harsh and the preparation method is relatively complex.

[0007] In summary, there is an urgent need to find a three-component catalyst for removing ammonia nitrogen with a wide range of raw material sources, low cost, high ammonia nitrogen removal rate, capable of rapidly oxidizing and degrading ammonia nitrogen in the gaseous state under alkaline conditions, simple process, low cost, and suitable for industrial production, as well as its application in catalytic wet oxidation. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the above-mentioned defects existing in the prior art and provide a three-component catalyst for removing ammonia nitrogen with a wide range of raw material sources, low cost, high ammonia nitrogen removal rate, and capable of rapidly oxidizing and degrading ammonia nitrogen in the gaseous state under alkaline conditions.

[0009] The further technical problem to be solved by the present invention is to overcome the above-mentioned defects existing in the prior art and provide an application of a three-component catalyst for removing ammonia nitrogen with a simple process, low cost, and suitable for industrial production in catalytic wet oxidation.

[0010] The technical solution adopted by the present invention to solve its technical problems is as follows: A three-component catalyst for removing ammonia nitrogen includes a heterogeneous catalyst, a homogeneous catalyst, and a pH buffer. The catalytic oxidation and removal of ammonia nitrogen by the catalyst of the present invention are carried out in two forms: First, the homogeneous catalyst directly oxidizes ammonia nitrogen and organic nitrogen in the wastewater under alkaline conditions; second, the hydrophobic pores of the heterogeneous catalyst can selectively adsorb ammonia gas and oxygen in the wastewater and oxidize and remove the ammonia gas in the gaseous state.

[0011] Preferably, the heterogeneous catalyst is zeolite supported with transition metal oxide. Zeolite can not only be used as the carrier of the transition metal oxide, but also adsorb free ammonia gas and oxygen in the wastewater, and realize the oxidation of gaseous ammonia gas under the catalysis of the metal oxide.

[0012] Preferably, the loading amount of the transition metal oxide in the zeolite supported with transition metal oxide is 10-30% (more preferably 22-28%).

[0013] Preferably, the transition metal oxide is one or more of cerium oxide, lanthanum oxide, cobalt oxide, nickel oxide, copper oxide, manganese oxide, etc. Since noble metal catalysts have a high cost and are less used in industry. During the catalytic oxidation reaction process, transition metals can provide empty orbitals or lone pair electrons to form intermediate products, reduce the reaction activation energy, and promote the reaction to proceed.

[0014] Preferably, the zeolite is TiO2 Modified zeolite. After TiO 2 The modified zeolite has good hydrophobicity, so that the surface of the zeolite will not occupy the active sites due to the adsorption of liquid, avoiding the generation of liquid-phase mass transfer resistance. By maintaining the number of active sites and reducing the mass transfer resistance, the ammonia nitrogen removal efficiency is improved.

[0015] Preferably, the homogeneous catalyst is a complex of metal ions and EDTA. After the metal ions are made into a complex of EDTA, it can be ensured that the metal ions are not precipitated within the pH range of 8.5 to 10.5, and the catalytic oxidation effect can be effectively exerted. At the same time, the bromide ions in bromate will be oxidized to hypobromite during the CWAO process. Hypobromite can quickly oxidize ammonia nitrogen and is itself reduced to the initial bromide ion state, realizing the recycling of bromide ions and thus improving the oxidation efficiency.

[0016] Preferably, the metal ions are one or more of copper, cobalt or nickel ions, etc.

[0017] Preferably, the pH buffer is an aqueous solution mixture of sodium carbonate and sodium bicarbonate.

[0018] Preferably, the preparation method of the transition metal oxide supported zeolite is: adding zeolite into the transition metal salt solution, stirring, impregnating, filtering, drying to constant weight, and calcining to obtain the transition metal oxide supported zeolite.

[0019] Preferably, the mass-volume ratio kg / L of the zeolite to the transition metal salt solution is 1:5 to 20.

[0020] Preferably, the concentration of the transition metal salt solution is 0.1 to 0.5 mol / L.

[0021] Preferably, the transition metal salt is nitrate and / or sulfate, etc.

[0022] Preferably, the stirring temperature is room temperature and the time is 0.5 to 5.0 h. Stirring first is to ensure that there is enough salt concentration around the zeolite so that its surface can be fully loaded with metal salt substances. Impregnating later is to make the substances loaded on its surface stable and facilitate subsequent calcination.

[0023] Preferably, the impregnation temperature is room temperature and the time is 5 to 15 h.

[0024] Preferably, the drying temperature is 40 to 70 °C and the time is 6 to 12 h.

[0025] Preferably, the temperature of the calcination is 400 to 1000 °C (more preferably 500 to 800 °C), and the time is 2 to 5 h. The metal oxide can well form a specific crystal form with catalytic function within the range of the calcination temperature, and decompose and volatilize some impurities of the material itself.

[0026] Preferably, the TiO 2 The preparation method of the modified zeolite is as follows: Add zeolite into the ethanol solution of tetrabutyl titanate, then add water, stir and impregnate, filter, dry to constant weight, and calcine to obtain TiO 2 Modified zeolite.

[0027] Preferably, the mass-volume ratio kg / L of the zeolite to the ethanol solution of tetrabutyl titanate is 1:10 to 20.

[0028] Preferably, the concentration of the ethanol solution of tetrabutyl titanate is 0.3 to 2.0 mol / L.

[0029] Preferably, the volume ratio of water to the ethanol solution of tetrabutyl titanate is 0.5 to 2.0:1.

[0030] Preferably, the temperature of the stirring impregnation is room temperature, and the time is 0.5 to 3.0 h.

[0031] Preferably, the temperature of the drying is 40 to 70 °C, and the time is 6 to 12 h.

[0032] Preferably, the temperature of the calcination is 300 to 600 °C, and the time is 1 to 5 h.

[0033] Preferably, the preparation method of the homogeneous catalyst is as follows: Dissolve the metal bromide salt in water, then add EDTA and stir to form a complex of metal ions and EDTA. The metal bromide salt is one or more of copper, cobalt or nickel bromide salts, etc. The EDTA is the abbreviation of ethylenediaminetetraacetic acid.

[0034] Preferably, the concentration of the metal bromide salt dissolved in water is 0.5 to 1.5 mol / L.

[0035] Preferably, the molar ratio of the metal ions to EDTA is 0.5 to 2.0:1.

[0036] Preferably, the temperature of the stirring is room temperature, and the time is 0.5 to 3.0 h.

[0037] Preferably, the preparation method of the pH buffer is as follows: First dissolve sodium carbonate in water, and then add sodium bicarbonate to dissolve it.

[0038] Preferably, the mass concentration of the sodium carbonate solution obtained after dissolving sodium carbonate in water is 1 to 10% (more preferably 2 to 8%).

[0039] Preferably, the dosage of the sodium bicarbonate is such that the pH value of the prepared buffer is 11.5 - 12.5.

[0040] The technical solution adopted by the present invention to further solve its technical problems is as follows: An application of a three-component catalyst for removing ammonia nitrogen in catalytic wet oxidation. First, the heterogeneous catalyst in the three-component catalyst for removing ammonia nitrogen is loaded into a catalytic wet oxidation reactor. After the wastewater is fed into the catalytic wet oxidation reactor, the homogeneous catalyst in the three-component catalyst for removing ammonia nitrogen is added to the wastewater in the catalytic wet oxidation reactor, and then the pH buffer in the three-component catalyst for removing ammonia nitrogen is added, and oxygen is introduced to carry out a catalytic wet oxidation reaction to obtain recycled alkaline water.

[0041] Preferably, the loading amount of the heterogeneous catalyst has a volume space velocity of 0.1 - 5.0 / h (more preferably 0.5 - 3.0 / h) relative to the volume of the wastewater. The setting of the volume space velocity is to achieve the best removal effect at a suitable energy consumption.

[0042] Preferably, the initial ammonia nitrogen content in the wastewater is 8000 - 30000 mg / L, and the initial pH value is 4 - 8. The wastewater used in the present invention is from the production wastewater of a catalyst company.

[0043] Preferably, the dosage of the homogeneous catalyst is such that the mass concentration of metal ions in the homogeneous catalyst in the wastewater is 50 - 500 mg / L (more preferably 80 - 200 mg / L). The setting of the concentration is to achieve the best removal effect at a suitable energy consumption.

[0044] Preferably, according to the acid-base property of the wastewater, the dosage of the pH buffer is adjusted so that the pH value of the produced water is 8.5 - 10.5. Ammonia can be effectively removed under alkaline conditions. By adding the pH buffer, the problem that the produced water is acidic during the CWAO reaction process is solved, so that ammonia nitrogen exists in the form of free ammonia molecules. The oxidation reaction rate of gaseous ammonia molecules is much higher than that of ammonium ions or dissolved ammonia in the liquid, and it is also easier to adsorb onto the catalyst surface, greatly improving the oxidation effect of ammonia nitrogen, thereby improving the removal efficiency of ammonia nitrogen in the wastewater. However, considering the problem of drug addition cost, it is not advisable to adjust to too high a pH value.

[0045] Preferably, the mass ratio of the oxygen to the initial ammonia nitrogen is 1.5 - 2.5:1.

[0046] Preferably, the temperature of the catalytic wet oxidation reaction is 230 - 275 °C, the pressure is 4.0 - 7.5 MPa, and the residence time is 0.5 - 2.0 h. The setting of the reaction conditions is to achieve the best removal effect at a suitable energy consumption.

[0047] The beneficial effects of the present invention are as follows:

[0048] (1) Compared with general catalysts in the CWAO system, the catalyst of the present invention innovatively combines homogeneous catalysts, heterogeneous catalysts, and pH buffers, which can solve the problems that the acidic conditions in the current CWAO reaction process are not conducive to ammonia nitrogen removal and the ammonia nitrogen removal efficiency is poor in the liquid state. It can not only make the reaction proceed fully, but also recycle some catalysts, and the raw materials are widely sourced, without using precious metal active components, with low costs, achieving the goals of high efficiency and economy, having good industrial application value, and having a high catalytic wet air oxidation efficiency for ammonia nitrogen in wastewater, with an ammonia nitrogen removal rate as high as 92.20%;

[0049] (2) The method of the present invention has a simple process and low costs, and is suitable for industrial production. Detailed implementation manners

[0050] The present invention will be further described below in conjunction with embodiments.

[0051] The wastewater used in the embodiments and comparative examples of the present invention is from the production wastewater of a catalyst company, with an initial ammonia nitrogen content of 9095 mg / L and an initial pH value of 4.62. The raw materials or chemical reagents used in the embodiments and comparative examples of the present invention are all obtained through conventional commercial channels unless otherwise specified. The ammonia nitrogen concentration in the embodiments and comparative examples of the present invention is detected by the Nessler's reagent spectrophotometry method.

[0052] Example 1 of a three-component catalyst for removing ammonia nitrogen

[0053] The three-component catalyst for removing ammonia nitrogen includes a heterogeneous catalyst, a homogeneous catalyst, and a pH buffer;

[0054] The heterogeneous catalyst is TiO-modified zeolite loaded with CeO at a 25% loading; the homogeneous catalyst is a complex of copper ions and EDTA; the pH buffer is an aqueous solution mixture of sodium carbonate and sodium bicarbonate; 2 The preparation method of the TiO-modified zeolite loaded with CeO at a 25% loading is as follows: Add TiO-modified zeolite to a cerium nitrate salt solution (0.3 mol / L) at a mass-to-volume ratio of 1 kg:10 L, stir at room temperature for 3 h, soak at room temperature for 10 h, filter, dry at 60 °C for 10 h until constant weight, and calcine at 550 °C for 3 h to obtain TiO-modified zeolite loaded with CeO at a 25% loading; 2

[0055] The CeO 2 loaded TiO 2 The preparation method of the modified zeolite is: Add TiO 2 modified zeolite to a cerium nitrate salt solution (0.3 mol / L) at a mass-to-volume ratio of 1 kg:10 L, stir at room temperature for 3 h, soak at room temperature for 10 h, filter, dry at 60 °C for 10 h until constant weight, and calcine at 550 °C for 3 h to obtain CeO 2 loaded TiO 2 modified zeolite at a 25% loading;

[0056] The TiO 2 ​The preparation method of the modified zeolite is as follows: Add zeolite to the ethanol solution of tetrabutyl titanate (1 mol / L) at a mass-to-volume ratio of 1 kg:10 L, then add water at a volume ratio of water to the ethanol solution of tetrabutyl titanate of 1:1. Stir and impregnate at room temperature for 3 h, filter, dry at 60 °C for 10 h until constant weight, and calcine at 500 °C for 3 h to obtain TiO 2 modified zeolite;

[0057] The preparation method of the homogeneous catalyst is as follows: Dissolve copper bromide in water to make the concentration 1 mol / L, then add EDTA at a molar ratio of copper ions to EDTA of 1:1. Stir at room temperature for 2 h to form a complex of copper ions and EDTA;

[0058] The preparation method of the pH buffer is as follows: First dissolve sodium carbonate in water to obtain a sodium carbonate solution with a mass concentration of 5%, then add sodium bicarbonate and dissolve until the pH value of the buffer is 12.0. That's it.

[0059] Application Example 1 of a three-component catalyst for ammonia nitrogen removal in catalytic wet air oxidation

[0060] First, load the heterogeneous catalyst in the three-component catalyst for ammonia nitrogen removal described in Application Example 1 into the catalytic wet air oxidation reactor, and the loading amount is 1 / h based on the volume space velocity of the wastewater. After the wastewater is fed into the catalytic wet air oxidation reactor, add the homogeneous catalyst in the three-component catalyst for ammonia nitrogen removal described in Application Example 1 into the wastewater in the catalytic wet air oxidation reactor, so that the mass concentration of copper ions in the homogeneous catalyst in the wastewater is 100 mg / L. Then add the pH buffer in the three-component catalyst for ammonia nitrogen removal described in Application Example 1, and adjust the dosage of the pH buffer so that the pH value of the produced water is 10.5. Feed oxygen at a mass ratio of oxygen to initial ammonia nitrogen of 2:1, and carry out the catalytic wet air oxidation reaction at 270 °C and a pressure of 7 MPa for a residence time of 2 h to obtain recycled alkaline water.

[0061] Application Comparative Example 1-1

[0062] The difference between this application comparative example and Application Example 1 is only that: no pH buffer is used, and the pH value of the produced water is 3.74. The rest is the same as Application Example 1.

[0063] Application Comparative Example 1-2

[0064] The difference between this application comparative example and Application Example 1 is only that: no heterogeneous catalyst is used. The rest is the same as Application Example 1.

[0065] Application Comparative Example 1-3

[0066] The difference between this application comparative example and Application Example 1 is only that: no homogeneous catalyst is used. The rest is the same as Application Example 1.

[0067] For the ammonia nitrogen concentration and removal rate in the wastewater treated by Application Example 1 and Application Comparative Examples 1-1 to 1-3 of the present invention, the results are shown in Table 1.

[0068] Table 1 Ammonia nitrogen concentration and removal rate in the wastewater treated by Application Example 1 and Application Comparative Examples 1-1 to 1-3 of the present invention

[0069]

[0070] As can be seen from Table 1, in Application Example 1 of the present invention, the ammonia nitrogen in the wastewater can achieve a good removal effect, and the present invention is expected to be applied to the treatment of wastewater with a high ammonia nitrogen content. In Application Comparative Example 1-1, due to the lack of a pH buffer, the pH value of the actual produced water further decreases, and the ammonia nitrogen removal amount significantly decreases, indicating that ammonia nitrogen can exist in the form of free ammonia under alkaline conditions, which is more conducive to the subsequent catalytic reaction and can effectively remove ammonia nitrogen. In Application Comparative Examples 1-2 and 1-3, the heterogeneous catalyst and the homogeneous catalyst components are respectively missing, and the ammonia nitrogen removal effect decreases. Among them, the homogeneous catalyst has a greater impact, indicating that the homogeneous catalyst can better contact the substance to be degraded and has a better removal effect than the heterogeneous catalyst. However, the effective active substances loaded in the heterogeneous phase also play a promoting role in the removal of ammonia nitrogen. Therefore, the ammonia nitrogen removal effect is better under the synergistic action of the two components. From Application Comparative Examples 1-1 to 1-3, it can be seen that removing or reducing any one of the catalyst components will have a great impact on the removal of ammonia nitrogen, and during the ammonia nitrogen removal process, the influence of the pH value is particularly large.

[0071] Example 2 of a three-component catalyst for removing ammonia nitrogen

[0072] The difference between this example and Example 1 is only that: the CeO 2 loaded TiO 2 The preparation method of the modified zeolite is: adding the modified zeolite to the cerium nitrate salt solution (0.3 mol / L) according to the mass-volume ratio of 1 kg:10 L, stirring at room temperature for 3 h, impregnating at room temperature for 10 h, filtering, drying at 60 °C for 10 h until constant weight, and calcining at 550 °C for 3 h to obtain CeO 2 modified zeolite loaded with TiO at a loading amount of 28%; 2 loaded with TiO at a 28% loading amount 2 modified zeolite;

[0073] The TiO 2The preparation method of the modified zeolite is as follows: Add zeolite to the ethanol solution of tetrabutyl titanate (1 mol / L) according to the mass-volume ratio of 1 kg:15 L, then add water according to the volume ratio of water to the ethanol solution of tetrabutyl titanate of 1:1, stir and impregnate at room temperature for 2 h, filter, dry at 60 °C for 10 h until constant weight, and calcine at 500 °C for 3 h to obtain TiO 2 modified zeolite.

[0074] The rest is the same as in Example 1.

[0075] Application Example 2 of a three-component catalyst for removing ammonia nitrogen in catalytic wet oxidation

[0076] The difference between this application example of the present invention and Application Example 1 is only that: the heterogeneous catalyst used in Application Example 1 is replaced with the CeO obtained in Example 2 2 TiO supported at a loading of 28% 2 modified zeolite. The rest is the same as in Application Example 1.

[0077] A three-component catalyst for removing ammonia nitrogen Comparative Example 2-1

[0078] The difference between this comparative example and Example 2 is only that: the CeO 2 supported TiO 2 In the preparation method of the modified zeolite, TiO 2 modified zeolite was added to the cerium nitrate salt solution (0.3 mol / L) according to the mass-volume ratio of 1 kg:3 L, and finally CeO 2 TiO supported at a loading of 9% 2 modified zeolite. The rest is the same as in Example 2.

[0079] A three-component catalyst for removing ammonia nitrogen Comparative Example 2-2

[0080] The difference between this comparative example and Example 2 is only that: the CeO 2 supported TiO 2 In the preparation method of the modified zeolite, the calcination temperature is 300 °C, and finally CeO 2 TiO supported at a loading of 17% 2 modified zeolite. The rest is the same as in Example 2.

[0081] A three-component catalyst for removing ammonia nitrogen Comparative Example 2-3

[0082] The difference between this comparative example and Example 2 is that: the CeO 2 supported TiO 2 In the preparation method of the modified zeolite, do not stir, impregnate at room temperature for 13 h, and finally obtain CeO 2 TiO supported at a loading of 20%2 Modified zeolite. The rest is the same as in Example 2.

[0083] Application Comparative Examples 2-1 to 2-3

[0084] The differences between Application Comparative Examples 2-1 to 2-3 of the present invention and Application Example 2 are only that: the heterogeneous catalysts used in Application Example 2 are respectively replaced with CeO obtained from Comparative Examples 2-1 to 2-3 2 TiO loaded at a loading of 9%, 17%, and 20% 2 Modified zeolite. The rest is the same as in Application Example 2.

[0085] The ammonia nitrogen concentration and removal rate in the wastewater after being treated by Application Example 2 and Application Comparative Examples 2-1 to 2-3 of the present invention are shown in Table 2.

[0086] Table 2 Ammonia nitrogen concentration and removal rate in the wastewater after being treated by Application Example 2 and Application Comparative Examples 2-1 to 2-3 of the present invention

[0087]

[0088] As can be seen from Table 2, compared with Application Example 1, the dosage of tetrabutyl titanate solution in Application Example 2 is larger, and TiO 2 Hydrophobic modification of the zeolite and increasing the dosage of tetrabutyl titanate within an appropriate range will increase the active sites on the zeolite surface, providing more contact area for the loading of cerium oxide. By increasing the dosage of tetrabutyl titanate, the adsorption of liquid on the zeolite surface can be reduced, thus occupying fewer active sites, making the liquid-phase mass transfer resistance significantly smaller than the gas-phase. Therefore, under the conditions of more active sites and smaller mass transfer resistance, the ammonia nitrogen removal efficiency is improved. In Application Comparative Example 2-1, the reduction of the cerium oxide loading reduces the ammonia nitrogen removal rate, and the increase in the dosage of tetrabutyl titanate is difficult to completely offset the reduction in the removal rate caused by the reduction of the cerium oxide loading, indicating that the loading of cerium oxide has a greater impact on the ammonia nitrogen removal rate. In Application Comparative Example 2-2, since it is not calcined at high temperature, the cerium nitrate loaded on the zeolite surface cannot be converted into cerium oxide with higher catalytic activity, so the ammonia nitrogen removal rate decreases. In Application Comparative Example 2-3, due to the lack of a stirring step, although the soaking time is extended, the cerium nitrate near the zeolite cannot be replenished in time, resulting in a reduction in loading and a decrease in the ammonia nitrogen removal effect.

[0089] Example 3 of a three-component catalyst for removing ammonia nitrogen

[0090] The difference between this example and Example 1 is only that: the preparation method of the homogeneous catalyst is: dissolving copper bromide in water to make the concentration 0.7 mol / L, and then adding EDTA with a molar ratio of copper ions to EDTA of 0.7:1. At room temperature, after stirring for 1.5 h, a complex of copper ions and EDTA is formed;

[0091] The preparation method of the pH buffer is as follows: First, dissolve sodium carbonate in water to obtain a sodium carbonate solution with a mass concentration of 5%. Then, add sodium bicarbonate and dissolve it until the pH value of the buffer is 12.5, and it is ready.

[0092] The rest is the same as in Example 1.

[0093] Application Example 3 of a three-component catalyst for ammonia nitrogen removal in catalytic wet oxidation

[0094] The difference between this application example of the present invention and Application Example 1 is only that: the homogeneous catalyst and the pH buffer used in Application Example 1 are respectively replaced with the homogeneous catalyst and the pH buffer obtained in Example 3. The rest is the same as in Application Example 1.

[0095] Comparative Example 3-1 of a three-component catalyst for ammonia nitrogen removal

[0096] The difference between this comparative example and Example 3 is only that: in the preparation method of the homogeneous catalyst, dissolve copper bromide in water to make the concentration 0.3 mol / L, and then add EDTA with a molar ratio of copper ions to EDTA of 0.3:1. At room temperature, after stirring for 1.5 h, a complex of copper ions and EDTA is formed. The rest is the same as in Example 3.

[0097] Comparative Example 3-2 of a three-component catalyst for ammonia nitrogen removal

[0098] The difference between this comparative example and Example 3 is only that: the preparation method of the pH buffer is as follows: dissolve sodium bicarbonate in water to make a sodium bicarbonate solution with a pH value of 8.5. The rest is the same as in Example 3.

[0099] Application Comparative Example 3-1

[0100] The difference between Application Comparative Example 3-1 of the present invention and Application Example 3 is only that: the homogeneous catalyst used in Application Example 3 is replaced with the homogeneous catalyst obtained in Comparative Example 3-1, and the mass concentration of copper ions in the homogeneous catalyst in the wastewater is 8 mg / L. The rest is the same as in Application Example 3.

[0101] Application Comparative Example 3-2

[0102] The difference between Application Comparative Example 3-2 of the present invention and Application Example 3 is only that: the pH buffer used in Application Example 3 is replaced with the pH buffer obtained in Comparative Example 3-2, and the dosage of the pH buffer is adjusted so that the pH value of the produced water is 6.21. The rest is the same as in Application Example 3.

[0103] The ammonia nitrogen concentration and removal rate in the wastewater after being treated by Application Example 3, Application Comparative Examples 3-1 and 3-2 of the present invention are shown in Table 3.

[0104] Table 3 Ammonia nitrogen concentration and removal rate in the wastewater after treatment by Application Example 3, Application Comparative Examples 3-1 and 3-2 of the present invention

[0105]

[0106] As can be seen from Table 3, since the dosage of the homogeneous catalyst in Application Comparative Example 3-1 was reduced, the removal effect of ammonia nitrogen was affected. And since the pH value of the pH buffer in Application Comparative Example 3-2 was decreased, even if the dosage was sufficient, it would still cause the pH value of the produced water to decrease, which would also affect the removal effect of ammonia nitrogen.

[0107] Application Examples 4-1 and 4-2 of a three-component catalyst for removing ammonia nitrogen in catalytic wet air oxidation

[0108] First, the heterogeneous catalyst in the three-component catalyst for removing ammonia nitrogen described in Example 1 was loaded into the catalytic wet air oxidation reactor in sequence, and the space velocities relative to the volume of the wastewater were 1 / h and 3 / h respectively. After the wastewater was fed into the catalytic wet air oxidation reactor, the homogeneous catalyst in the three-component catalyst for removing ammonia nitrogen described in Example 1 was added to the wastewater in the catalytic wet air oxidation reactor, so that the mass concentration of copper ions in the homogeneous catalyst in the wastewater was 100 mg / L and 200 mg / L respectively. Then, the pH buffer in the three-component catalyst for removing ammonia nitrogen described in Example 1 was added, and the dosage of the pH buffer was adjusted so that the pH values of the produced water were 10.5 and 9.5 respectively. Oxygen was introduced at a mass ratio of oxygen to initial ammonia nitrogen of 2:1 and 1.5:1 respectively. The catalytic wet air oxidation reaction was carried out at 250 °C and a pressure of 5 MPa, and the residence times were 2 h and 1 h respectively to obtain the recycled alkaline water.

[0109] Application Comparative Example 4-1 of a three-component catalyst for removing ammonia nitrogen in catalytic wet air oxidation

[0110] The difference between this application comparative example and Application Example 4-1 is only that: the temperature of the catalytic wet air oxidation reaction is 220 °C and the pressure is 3.2 MPa. The rest is the same as Application Example 4-1.

[0111] Application Comparative Example 4-2 of a three-component catalyst for removing ammonia nitrogen in catalytic wet air oxidation

[0112] The difference between this application comparative example and Application Example 4-1 is only that: during the catalytic wet air oxidation reaction, air was introduced at a mass ratio of air to ammonia nitrogen of 2:1. The rest is the same as Application Example 4-1.

[0113] The ammonia nitrogen concentration and removal rate in the wastewater after treatment by Application Examples 4-1 and 4-2, Application Comparative Examples 4-1 and 4-2 of the present invention are shown in Table 4.

[0114] Table 4 Ammonia nitrogen concentration and removal rate in wastewater after treatment with Application Examples 4-1 and 4-2 of the present invention and Application Comparative Examples 4-1 and 4-2

[0115]

[0116] As can be seen from Table 4, from Application Examples 4-1 and 4-2 of the present invention, it can be known that when the heterogeneous catalyst, homogeneous catalyst and pH buffer are applied within the technical parameter ranges described in the present invention, good ammonia nitrogen removal effects can be obtained; by comparing Application Comparative Examples 4-1 and 4-2 with Application Example 4-1 of the present invention, it can be known that during the catalytic wet air oxidation reaction process, temperature, pressure and gas source have a great influence on its catalytic effect. The degradation of substances requires a critical value. When the temperature, pressure, etc. are lower than this critical value, it is not sufficient to trigger the reaction, and the ammonia nitrogen removal effect will be reduced. The oxygen content in the oxygen source is much higher than that in the air source, and more oxygen can be provided during the reaction process, which is more conducive to promoting the forward progress of the reaction.

Claims

1. A three-component catalyst for removing ammonia nitrogen, characterized in that: It includes a heterogeneous catalyst, a homogeneous catalyst and a pH buffer; the heterogeneous catalyst is zeolite supported with transition metal oxide; the loading amount of the transition metal oxide in the zeolite supported with transition metal oxide is 10-30%; the transition metal oxide is one or more of cerium oxide, lanthanum oxide, cobalt oxide, nickel oxide, copper oxide or manganese oxide; the zeolite is TiO 2 modified zeolite; the homogeneous catalyst is a complex of metal ions and EDTA; the metal ions are one or more of copper, cobalt or nickel ions; the pH buffer is an aqueous solution mixture of sodium carbonate and sodium bicarbonate.

2. The three-component catalyst for removing ammonia nitrogen according to claim 1, characterized in that: The preparation method of the zeolite supported with transition metal oxide is as follows: adding zeolite into a transition metal salt solution, stirring, impregnating, filtering, drying to constant weight, and roasting to obtain the zeolite supported with transition metal oxide; the mass-volume ratio kg / L of the zeolite to the transition metal salt solution is 1:5 to 20; the concentration of the transition metal salt solution is 0.1 to 0.5 mol / L; the transition metal salt is nitrate and / or sulfate; the temperature of the stirring is normal temperature, and the time is 0.5 to 5.0 h; the temperature of the impregnation is normal temperature, and the time is 5 to 15 h; the temperature of the drying is 40 to 70 °C, and the time is 6 to 12 h; the temperature of the roasting is 400 to 1000 °C, and the time is 2 to 5 h.

3. The three-component catalyst for removing ammonia nitrogen according to claim 1 or 2, characterized in that: The TiO 2 The preparation method of the modified zeolite is as follows: Add zeolite into the ethanol solution of tetrabutyl titanate, then add water, stir and impregnate, filter, dry to constant weight, and calcine to obtain TiO 2 modified zeolite; The mass-volume ratio kg / L of the zeolite to the ethanol solution of tetrabutyl titanate is 1:10-20; The concentration of the ethanol solution of tetrabutyl titanate is 0.3-2.0 mol / L; The volume ratio of water to the ethanol solution of tetrabutyl titanate is 0.5-2.0:1; The temperature of the stirring impregnation is room temperature, and the time is 0.5-3.0 h; The drying temperature is 40-70 °C, and the time is 6-12 h; The calcination temperature is 300-600 °C, and the time is 1-5 h.

4. The three-component catalyst for removing ammonia nitrogen according to claim 1 or 2, characterized in that: The preparation method of the homogeneous catalyst is as follows: dissolving metal bromide salt in water, and then adding EDTA and stirring to form a complex of metal ions and EDTA; the concentration of the metal bromide salt dissolved in water is 0.5 to 1.5 mol / L; the molar ratio of the metal ions to EDTA is 0.5 to 2.0:1; the temperature of the stirring is room temperature, and the time is 0.5 to 3.0 h.

5. The three-component catalyst for removing ammonia nitrogen according to claim 3, characterized in that: The preparation method of the homogeneous catalyst is as follows: dissolving metal bromide salt in water, and then adding EDTA and stirring to form a complex of metal ions and EDTA; the concentration of the metal bromide salt dissolved in water is 0.5 to 1.5 mol / L; the molar ratio of the metal ions to EDTA is 0.5 to 2.0:1; the temperature of the stirring is room temperature, and the time is 0.5 to 3.0 h.

6. The three-component catalyst for removing ammonia nitrogen according to claim 1 or 2, characterized in that: The preparation method of the pH buffer is as follows: first dissolving sodium carbonate in water, and then adding sodium bicarbonate to dissolve, that is, it is completed; the mass concentration of the sodium carbonate solution obtained after dissolving sodium carbonate in water is 1 to 10%; the amount of sodium bicarbonate used makes the pH value of the prepared buffer 11.5 to 12.

5.

7. The three-component catalyst for removing ammonia nitrogen according to claim 3, characterized in that: The preparation method of the pH buffer is as follows: first dissolving sodium carbonate in water, and then adding sodium bicarbonate to dissolve, that is, it is completed; the mass concentration of the sodium carbonate solution obtained after dissolving sodium carbonate in water is 1 to 10%; the amount of sodium bicarbonate used makes the pH value of the prepared buffer 11.5 to 12.

5.

8. The three-component catalyst for removing ammonia nitrogen according to claim 4, characterized in that: The preparation method of the pH buffer is as follows: first dissolve sodium carbonate in water, and then add sodium bicarbonate and dissolve it to obtain the pH buffer; the mass concentration of the sodium carbonate solution obtained after dissolving sodium carbonate in water is 1-10%; the dosage of sodium bicarbonate is such that the pH value of the prepared buffer is 11.5-12.

5.

9. The three-component catalyst for ammonia nitrogen removal according to claim 5, characterized in that: The preparation method of the pH buffer is as follows: first dissolve sodium carbonate in water, and then add sodium bicarbonate and dissolve it to obtain the pH buffer; the mass concentration of the sodium carbonate solution obtained after dissolving sodium carbonate in water is 1-10%; the dosage of sodium bicarbonate is such that the pH value of the prepared buffer is 11.5-12.

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10. The application of a three-component catalyst for ammonia nitrogen removal according to any one of claims 1-9 in catalytic wet air oxidation, characterized in that: First, load the heterogeneous catalyst in the three-component catalyst for ammonia nitrogen removal according to any one of claims 1-9 into the catalytic wet air oxidation reactor. After the wastewater is fed into the catalytic wet air oxidation reactor, add the homogeneous catalyst in the three-component catalyst for ammonia nitrogen removal according to any one of claims 1-9 into the wastewater in the catalytic wet air oxidation reactor, then add the pH buffer in the three-component catalyst for ammonia nitrogen removal according to any one of claims 1-9, introduce oxygen, and carry out the catalytic wet air oxidation reaction to obtain recycled alkaline water.

11. The application of the three-component catalyst for ammonia nitrogen removal according to claim 10 in catalytic wet air oxidation, characterized in that: The loading amount of the heterogeneous catalyst is 0.1-5.0 / h in terms of the volume space velocity relative to the wastewater; the initial ammonia nitrogen content in the wastewater is 8000-30000 mg / L, and the initial pH value is 4-8; the dosage of the homogeneous catalyst is such that the mass concentration of metal ions in the homogeneous catalyst in the wastewater is 50-500 mg / L; according to the acid-base property of the wastewater, adjust the dosage of the pH buffer so that the pH value of the produced water is 8.5-10.5; the mass ratio of oxygen to the initial ammonia nitrogen is 1.5-2.5:1; the temperature of the catalytic wet air oxidation reaction is 230-275 °C, the pressure is 4.0-7.5 MPa, and the residence time is 0.5-2.0 h.

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