JP5727269B2 - Wastewater treatment catalyst containing nitrogen-containing compound and wastewater treatment method using the same - Google Patents

Description

  In the present invention, waste water containing a nitrogen-containing compound is treated by wet oxidation treatment in the presence of a solid catalyst (hereinafter, wet oxidation treatment using a solid catalyst and its method are also referred to as catalyst wet oxidation treatment and catalyst wet oxidation treatment method, respectively). ) To purify the nitrogen-containing compounds in the wastewater and make the wastewater harmless.

  It has been a long time since red tides and musty odors have been generated due to eutrophication in sea areas, lakes, rivers, etc., but this is caused by such factors as nitrogen contained in wastewater discharged into the water areas. Nutrients are the cause. For this reason, although the drainage regulation regarding nitrogen is implemented, since a nitrogen-containing compound cannot fully be removed only by performing processing by the conventional activated sludge method etc., it is often necessary to newly provide a denitrification process.

  Conventionally, biological treatment methods such as activated sludge treatment methods, combustion treatment methods, agglomeration treatment methods using anionic polymer flocculants and the like have been adopted as treatment methods for wastewater containing nitrogen-containing compounds.

  On the other hand, a method of wet oxidation using a catalyst has been proposed as a method for treating wastewater containing a nitrogen-containing compound. (Patent Document 1). This is a method of treating waste water under a pressure condition that maintains a liquid phase at a temperature of 100 to 370 ° C. and in the presence of a specific catalyst under the supply of a gas containing oxygen. According to this treatment method, the nitrogen-containing compound in the waste water can be converted into nitrogen gas, water, carbon dioxide gas, inorganic acid, ash, lower molecular weight organic matter, etc., and purified.

  Although this catalyst wet oxidation treatment method can efficiently treat nitrogen-containing compounds, depending on the treatment conditions and the properties of the wastewater, a large amount of nitrate nitrogen and / or nitrite nitrogen may be generated during the treatment. High total nitrogen treatment efficiency may be required. In particular, when treating actual wastewater containing nitrogen-containing compounds in a distribution system, the total nitrogen concentration in the wastewater always fluctuates. For example, high treatment efficiency may be required even when an oxidizing agent is supplied in a constant amount and wastewater with a low nitrogen concentration is temporarily supplied. If the treatment of waste water is performed for a long period of time, the catalyst may change in quality, and it may be difficult to maintain high purification properties.

JP 2008-93539 A

  An object of the present invention is to provide a method capable of solving the above problems. That is, the present invention can treat wastewater containing a nitrogen-containing compound with high purifying properties using a catalyst effective in suppressing the production of nitrate nitrogen and / or nitrite nitrogen, and can maintain higher purifying properties. It aims at providing the processing method of the waste_water | drain containing the novel nitrogen-containing compound which can be performed.

  As a result of diligent research to solve the above problems, the present inventor has controlled the catalytic activity of the noble metal component contained in the solid catalyst by adding a base metal component in the treatment of wastewater containing a nitrogen-containing compound. By suppressing the generation of nitrogen and / or nitrite nitrogen, the present inventors have found a catalyst that has a high total nitrogen treatment performance and maintains a high purification performance for a long period of time. That is, the present invention is a method for treating wastewater containing a novel nitrogen-containing compound using a solid catalyst having extremely high selectivity to nitrogen gas even under conditions where the amount of oxidant supply is excessive. The present invention is specified as follows.

(1) A noble metal and an active auxiliary agent are coated with a porous inorganic oxide, and the active auxiliary agent is titanium, iron, zirconium, cobalt, nickel, cerium, lanthanum, manganese, yttrium, zinc And at least two oxides selected from the group consisting of bismuth and at least two complex oxides selected from the above group, wherein the active auxiliary agent has an average particle diameter of 25 to 50 nm for treating nitrogen-containing compounds It is a catalyst.

  (2) The catalyst for treating a nitrogen-containing compound according to (1), wherein the porous inorganic oxide has a pore volume of 0.12 to 0.5 ml / g.

( 3 ) A method for producing a catalyst for treating a nitrogen-containing compound as described in (1) or (2 ) above ,
By impregnating the noble metal component and an active auxiliaries simultaneously porous inorganic oxide is characterized by coating the said noble metal component and the active aid on the porous inorganic oxide,
Further comprising adopting at least one step of heat treatment at a temperature of 300 ° C. or higher in an oxidizing atmosphere after impregnating and supporting the active assistant,
It is a manufacturing method of the catalyst for nitrogen-containing compound processing which has the process of carrying out the reduction process of the said noble metal component in a reducing atmosphere after the above-mentioned heat treatment process .

( 4 ) Using the catalyst described in (1) or (2) above, wastewater containing a nitrogen-containing compound is heated to a temperature of 100 ° C. or higher and lower than 370 ° C. in the presence of an oxidizing agent, and the wastewater retains a liquid phase. A wastewater treatment method characterized by treating a nitrogen compound in the wastewater under pressure conditions.

  In the present invention, high total nitrogen treatment performance can be obtained by treating waste water containing a nitrogen-containing compound using a catalyst effective in suppressing the production of nitrate nitrogen and / or nitrite nitrogen. Furthermore, it is possible to stably maintain a high purification property without altering the catalyst.

  In addition, the wastewater treatment method of the present invention can be used in the case where an organic and / or inorganic COD component or the like is contained in the wastewater as a contaminant other than the nitrogen-containing compound. Since it can be converted into inorganic salts, ash, organic substances having a lower molecular weight, etc. to purify the wastewater, it is a very excellent wastewater treatment method.

FIG. 1 shows an apparatus used in Examples and Comparative Examples according to the present invention.

  The catalyst according to the first aspect of the present invention is a catalyst for treating a nitrogen-containing compound, wherein a porous inorganic oxide is coated with a noble metal and an active auxiliary agent.

  Embodiments of the present invention will be described below.

  The noble metal contains a metal and / or oxide of at least one element of silver, platinum, palladium, ruthenium, rhodium, iridium and gold, and preferably contains platinum, palladium, ruthenium and iridium It is. More preferably, silver, platinum, palladium, ruthenium, rhodium and iridium are contained. Even more preferably, it contains platinum, palladium, and ruthenium. Particularly preferred are those containing palladium and ruthenium.

The active auxiliary agent is at least one oxide selected from the group consisting of titanium, iron, zirconium, cobalt, nickel, cerium, lanthanum, manganese, yttrium, indium, zinc and bismuth, or at least two types selected from the above group A complex oxide, preferably at least one oxide selected from the group consisting of titanium, iron, zirconium, cerium, lanthanum, manganese, yttrium, indium, zinc, or at least two complex oxides selected from the above group It is. More preferably, it is at least one oxide selected from the group consisting of titanium, zirconium, cerium, and lanthanum, or at least two complex oxides selected from the above group. Particularly preferred are titanium oxide (TiO ₂ ), zirconia (ZrO ₂ ), ceria (CeO ₂ ), and lanthanum oxide (La ₂ O ₃ ). The above active auxiliaries may be used alone or in the form of a mixture of two or more. These are usually present in the catalyst as oxides. By using the active assistant and the noble metal, it is possible to suppress the production of nitrate nitrogen and / or nitrite nitrogen.

  In the present invention, the size of the active aid is not particularly limited. The average particle size of the active assistant is preferably 1 nm or more, more preferably 2 nm or more, and even more preferably 3 nm or more. The upper limit of the size of the active aid is not particularly limited, but is preferably 80 nm or less, more preferably 50 nm or less, still more preferably 47 nm or less, and particularly preferably 45 nm or less. Usually, the active auxiliary agent is present in the catalyst as an oxide, and it is possible to specifically suppress the production of nitrate nitrogen and / or nitrite nitrogen by controlling the average particle diameter to 1 to 80 nm. It becomes. In the present specification, the “average particle size” was observed with a transmission electron microscope (TEM-EDS). Specifically, 100 particles observed in an enlarged manner were arbitrarily selected, the length of each particle in the major axis direction was measured, and the average value was defined as the average particle diameter (nm).

  The porous inorganic oxide is not particularly limited, and those usually used for catalysts can be used. Specifically, at least one oxide or composite oxide or activated carbon selected from the group consisting of titanium, iron, silicon, zirconium, cobalt, nickel, aluminum, cerium, lanthanum, manganese, yttrium, indium, zinc and bismuth. It is. Preferably, the porous inorganic oxide is at least one oxide or composite oxide selected from the group consisting of titanium, iron, silicon, zirconium, aluminum, cerium, lanthanum, indium and bismuth. More preferably, the porous inorganic oxide is at least one oxide or composite oxide selected from the group consisting of titanium, iron, zirconium, cerium, and lanthanum. Particularly preferably, the porous inorganic oxide is at least one oxide or composite oxide selected from the group consisting of titanium, iron, zirconium, cerium, and lanthanum. The porous inorganic oxide and the active auxiliary agent may be oxides of the same element, but can be distinguished by different types of precursors and different stages used in preparation.

  In the present invention, the pore volume of the porous inorganic oxide is not particularly limited. The pore volume of the porous inorganic oxide is preferably 0.12 ml / g or more, more preferably 0.2 ml / g or more, and more preferably 0.25 ml / g or more. The upper limit of the pore volume of the porous inorganic oxide is not particularly limited, but is preferably 0.5 ml / g or less, more preferably 0.45 ml / g or less. In addition, when the pore volume is less than 0.12 ml / g, the contact efficiency between the catalyst and the pollutant decreases, and sufficient treatment performance is often not obtained. In addition, when the pore volume exceeds 0.50 ml / g, the durability of the catalyst may be reduced, and when used in wet oxidation treatment, the catalyst may collapse early. The pore volume can be measured by a device using a commercially available mercury intrusion method.

  The contents of the active aid, the noble metal and the porous inorganic oxide are not particularly limited. The total amount of the active auxiliary agent (in oxide equivalent), the noble metal (in metal equivalent) and the porous inorganic oxide is 100% by mass, and the content of the active auxiliary agent is 0.1 to 30% in terms of oxide. %, More preferably 0.2 to 20% by mass, and particularly preferably 0.5 to 10% by mass. Moreover, when the sum total of an active adjuvant (oxide conversion), a noble metal (metal conversion), and a porous inorganic oxide shall be 100 mass%, content of a noble metal is 0.05-10 mass% in metal conversion. It is preferable that it is 0.1-3 mass%. Further, the total amount of the active auxiliary agent (in terms of oxide), the noble metal (in terms of metal) and the porous inorganic oxide is 100% by mass, and the content of the porous inorganic oxide is 60 to 99.85% by mass. It is preferable that it is 77-99.7 mass%. When the amount of noble metal is less than 0.05% by mass, the effect of the noble metal elements is small and the activity of the catalyst is not improved. Even if it is used at a rate exceeding 10% by mass, the catalyst cost is increased. In addition, it is not economically preferable because the catalyst performance cannot be improved.

  The method for preparing the catalyst of the present invention is not particularly limited, but it is preferable to coat the porous inorganic oxide with a noble metal component and an active auxiliary agent by an impregnation method. That is, according to the second aspect of the present invention, there is provided a method for producing a catalyst for treating a nitrogen-containing compound according to the present invention, wherein a porous inorganic oxide is coated on the porous inorganic oxide by an impregnation method. . More specifically, as a method for preparing the catalyst of the present invention, a porous inorganic oxide is prepared in a solution (for example, an aqueous solution) obtained by dissolving each precursor of a noble metal and an active auxiliary agent in an appropriate solvent (for example, water). And evaporating the solvent (for example, water) by heating, the porous inorganic oxide can be impregnated with the noble metal and the active auxiliary agent. In addition, a porous inorganic oxide is added to a solution (for example, an aqueous solution) in which the precursors of the noble metal and the active auxiliary agent are dissolved in an appropriate solvent (for example, water), and an alkaline substance is added to the precipitate. It can also be carried on an object.

  Here, the method for impregnating the porous inorganic oxide with the noble metal component and the active auxiliary agent is not particularly limited. For example, a method of simultaneously impregnating a porous inorganic oxide with a noble metal component and an active aid, a method of sequentially impregnating a porous inorganic oxide with a noble metal component and an active aid, and the like can be selected as appropriate. By drying, calcining and / or reducing the impregnated catalyst, a catalyst in which a porous inorganic oxide is coated with a noble metal and an active aid can be obtained. Preferably, it is a method of evaporating an aqueous solution containing a noble metal component and an active aid or adding an alkaline substance to precipitate (coprecipitate). In addition, the calcination temperature of the said catalyst is 300-800 degreeC, More preferably, 350-600 degreeC is preferable. Further, it is also preferable to perform a reduction treatment in a hydrogen or nitrogen atmosphere.

  In this catalyst preparation step, after impregnating and supporting the active assistant, it is 200 ° C. or higher in the oxidizing atmosphere, more preferably 300 ° C. to 800 ° C., more preferably 400 to 600 ° C., for 1 to 5 hours. More preferably, a heat treatment (firing) step for 2 to 4 hours can be employed at least once. By this operation, a high purification property can be maintained. Here, examples of the oxidizing atmosphere include air, a mixed gas of oxygen and an inert gas, and the like.

  In the above method, the raw material (precursor) of the noble metal is not particularly limited, and any of organic salts, inorganic acid salts, and the like of the above metals can be used, but a water-soluble salt is preferable. For example, the noble metal can be appropriately selected from halides such as nitrates, oxalates, acetates, ammonium salts and chlorides. Preferred are nitrates, acetates and chlorides.

  Although the raw material of an active adjuvant is not specifically limited, A water-soluble compound, gel, etc. can be used. Specific examples include inorganic compounds such as halides such as nitrates, sulfates, and chlorides, and organic acid salts such as acetates, oxalates, and citrates. Nitrate, sulfate, acetate and chloride are preferred.

  Further, suitable solvents are not particularly limited, and water, methanol, ethanol and the like can be mentioned. In this case, the solvent may be used alone or in the form of a mixture of two or more. Preferably water is used. In addition, the concentration of the noble metal raw material (precursor) and the active auxiliary material in the solvent is not particularly limited, and the concentration of the predetermined noble metal and the active auxiliary is not limited as long as the noble metal and the active auxiliary raw material are dissolved. It can set suitably so that it may become quantity.

  Moreover, it does not restrict | limit especially as an alkaline substance in the case of using an alkaline substance, The alkaline substance used by the general coprecipitation method can be used similarly. Examples thereof include aqueous ammonia, sodium hydroxide or an aqueous solution thereof, potassium hydroxide or an aqueous solution thereof, sodium carbonate or an aqueous solution thereof. At this time, the amount of the alkaline substance added is not particularly limited as long as it is an amount capable of forming a precipitate to a desired degree. The alkaline substance is preferably added in such an amount that the pH of the solution containing the precious metal raw material (precursor) or the active auxiliary raw material is preferably 7 to 10, more preferably 7.5 to 9.5. .

After the firing step, if necessary, a noble metal component is reduced. Thereby, the catalyst of this invention can be manufactured. Here, the reduction treatment conditions for the noble metal component are not particularly limited, but for example, the reduction treatment temperature is preferably 150 to 600 ° C, more preferably 200 to 400 ° C. The reduction treatment time is preferably 1 to 5 hours, and more preferably 2 to 4 hours. Under such conditions, noble metal component particle size growth (sintering) does not occur, and a noble metal component having a desired size can be supported on the porous inorganic oxide or the active auxiliary agent. Further, the reduction process is performed in a reducing atmosphere. In this case, the reducing atmosphere is not particularly limited as long as the noble metal component raw material compound is reduced, but it is preferably performed in a mixed gas atmosphere of a reducing gas and an inert gas. The reducing gas is not particularly limited, but hydrogen (H ₂ ) gas is preferable. The inert gas is not particularly limited, and helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), nitrogen (N ₂ ), and the like can be used. The said inert gas may be used independently or may be used with the form of 2 or more types of mixed gas. The concentration of the reducing gas contained in the inert gas is not particularly limited, but considering safety and the like, the concentration of the reducing gas is preferably 1 to 20% by volume with respect to the total amount of the mixed gas. Under such conditions, the noble metal component can be efficiently reduced to the porous inorganic oxide or the active auxiliary agent.

  The shape of the catalyst is not particularly limited, and may be any of granular, spherical, pellet, crushed, saddle, honeycomb, and ring shapes, for example. In the case of a pellet shape, an arbitrary shape such as an elliptical shape, a polygonal shape, a trilobal shape, and a quadrilateral shape can be used in addition to a circular cross section.

  Next, a method for treating waste water using the catalyst of the present invention will be described. In the method of the present invention, the catalyst of the present invention may be used alone or in the form of a mixture of two or more.

  The catalyst of the present invention can effectively suppress the formation of nitrate nitrogen and / or nitrite nitrogen. For this reason, when the catalyst of this invention is used, the waste_water | drain containing a nitrogen-containing compound can be processed with high purification property, and high purification property can be maintained.

  Therefore, according to the third aspect of the present invention, using the catalyst of the present invention, wastewater containing a nitrogen-containing compound is heated to a temperature of 100 ° C. or higher and lower than 370 ° C. in the presence of an oxidizing agent, and the pressure at which the wastewater maintains a liquid phase. There is provided a method for treating waste water, characterized by treating nitrogen compounds in the waste water under conditions.

  Hereinafter, a wastewater treatment method using the catalyst according to the present invention, particularly a wet oxidation treatment method will be described in detail.

  The wastewater to be treated in the present invention may be any wastewater as long as it contains a nitrogen-containing compound. For example, chemical plants, electronic component manufacturing equipment, food processing equipment, printing plate making equipment, thermal power generation and nuclear power Wastewater discharged from various industrial plants such as power generation facilities such as power generation, photo processing equipment, metal processing equipment, metal plating equipment, metal refining equipment, and pulp and paper manufacturing equipment, domestic wastewater such as manure and sewage, wet smoke washing wastewater Examples of such wastewater include various wastewater treatment facilities and wastewater containing various nitrogen-containing compounds such as landfill leachate. Moreover, in order to process the soil containing a toxic substance, the extract which extracted the toxic substance in this soil in the liquid can also be handled as the wastewater to be treated of the present invention.

  The nitrogen-containing compound according to the present invention is not particularly limited as long as it contains a nitrogen atom. For example, inorganic nitrogen compounds, amine compounds, amide compounds, amino acid compounds, nitrogen-containing five-membered ring compounds , Nitrates, nitrites, nitro compounds, nitroso compounds, nitrosyl compounds and nitrogen-containing polymers.

  Examples of the inorganic nitrogen compound according to the present invention include ammonia, ammonium salt, hydrazine, and hydrazinium salt.

  The amine compound according to the present invention is a compound having an amino group in the molecule, and examples thereof include methylamine, ethylenediamine, triethanolamine, monoethanolamine, methyldiethanolamine, aniline, and pyridine.

  The amide compound according to the present invention is a compound having an amide group in the molecule, and examples include formamide, dimethylformamide, and urea.

  Examples of the amino acid compound according to the present invention include glycine, aspartic acid, phenylalanine, and tryptophan.

  Examples of the nitrogen-containing five-membered ring compound according to the present invention include N-methylpyrrolidone, pyrrole, imidazole, pyrazole, thiazole, oxazole, furazane and the like and derivatives thereof. Among these, in particular, imidazolidinone nitrogen-containing compounds such as DMI (1,3-dimethyl-2-imidazolidinone) are widely used as aprotic polar solvents, but in the treatment of such nitrogen compounds. The present invention is also suitable.

  The nitrogen-containing compound may be insoluble or hardly soluble in water, but is preferably soluble in water. In the case of treating a nitrogen-containing compound that is insoluble or sparingly soluble in water, it is preferable in terms of handling in processing that the nitrogen-containing compound is suspended in water. The nitrogen-containing compound in the waste water may exist as a single compound or may be mixed in a plurality.

  The “drainage” in the present invention is not limited to the so-called industrial drainage discharged from the industrial plant as described above, but includes all liquids containing nitrogen-containing compounds. Is not particularly limited.

  The total nitrogen concentration in the wastewater to be treated in the present invention is not particularly limited, but is effective from 30 mg / liter to 6000 mg / liter, preferably from 50 mg / liter to 5000 mg / liter. . When the total nitrogen is less than 30 mg / liter, the cost advantage of catalytic wet oxidation cannot be sufficiently obtained. On the other hand, when it exceeds 6000 mg / liter, since the total nitrogen concentration is too high, sufficient processing performance may not be obtained.

  Moreover, even if components other than the nitrogen-containing compound, for example, components such as the COD component, are contained in the waste water, there is no particular problem as long as it does not interfere with the wet oxidation reaction according to the present invention.

  The oxidizing agent according to the present invention may be any oxidizing agent that can oxidize oxidizable substances in waste water, and examples thereof include oxygen and / or ozone-containing gas and hydrogen peroxide. In the case of using gas, air is generally preferable. In addition, oxygen-containing exhaust gas generated from other plants can also be used conveniently. The oxidizable substance is a nitrogen-containing compound or a COD component.

  In the present invention, the oxidizing agent does not need to be supplied to the wastewater when the required amount is included in the wastewater, but is preferably supplied to the wastewater when the required amount is not included. The amount of the oxidizing agent contained in the wastewater is appropriately selected in the amount of the oxidizable substance in the wastewater, but preferably 0.7 mol times to the theoretical oxygen demand of the oxidizable substance. The ratio is 5.0 mol times, more preferably 1.0 mol times to 4.0 mol times. This is because when the amount is less than 0.7 mol times, harmful substances in the wastewater are not sufficiently decomposed, and when the amount exceeds 5.0 mol times, the equipment is only enlarged. The "theoretical oxygen demand" here means the amount of oxygen required to oxidize and / or decompose oxidants (nitrogen-containing compounds) in wastewater to ash such as nitrogen, carbon dioxide, water, and sulfate. When the wastewater contains oxidizable substances in addition to the nitrogen-containing compound, the theoretical oxygen demand is calculated including these.

  The processing method of the nitrogen-containing compound concerning this invention can be processed in the temperature range of 100 degreeC or more and less than 370 degreeC. If the treatment temperature is less than 100 ° C., the nitrogen-containing compound cannot be efficiently oxidized / decomposed, which is not preferable. This treatment temperature is preferably a temperature exceeding 120 ° C., more preferably a temperature exceeding 130 ° C., and further preferably a temperature exceeding 140 ° C. Moreover, since it becomes impossible for wastewater to maintain a liquid phase as process temperature is 370 degreeC or more, it is unpreferable. If the treatment temperature is raised, the operating cost required for heating rises, so the temperature is preferably 280 ° C. or lower, more preferably 260 ° C. or lower.

  On the other hand, the treatment pressure is not particularly limited as long as the wastewater maintains a liquid phase at the treatment temperature. Further, the adjustment of the treatment pressure is not particularly limited, and can be performed by a known method. For example, a pressure adjustment valve is provided on the exhaust gas outlet side of the wet oxidation treatment apparatus, and the wastewater keeps the liquid phase in the reaction tower. It is desirable to adjust the pressure appropriately according to the processing temperature so that it can be performed. Here, the processing pressure is not particularly limited, and can be appropriately adjusted depending on the processing temperature. For example, when the processing temperature is 100 ° C. or higher, the waste water is often vaporized under atmospheric pressure. Therefore, when the processing temperature is 100 ° C. or higher and lower than 170 ° C., about 0.2 to 1 MPa (Gauge). It is desirable to apply pressure and control the pressure so that the drainage can maintain the liquid phase. In addition, when the processing temperature is 170 ° C. or higher and lower than 230 ° C., a pressure of about 1 to 5 MPa (Gauge), and when the processing temperature is 230 ° C. or higher, a pressure higher than 5 MPa (Gauge) is used. In addition, it is desirable to control the pressure so that the drainage can maintain the liquid phase. Furthermore, in order to improve the treatment performance and the durability of the catalyst, the fluctuation of the treatment pressure is controlled within ± 20%, more preferably within ± 10%, and even more preferably within ± 5%.

In the case of a flow system for treating wastewater containing nitrogen-containing compounds, the space velocity of the wastewater is not particularly limited, but usually the space velocity per each catalyst layer is 0.1 liter · hr ⁻¹ to 10 liters. · Hr ^-1 , more preferably 0.2 liters · hr ^{-1 to} 5 liters · hr ^-1 , still more preferably 0.3 liters · hr ^{-1 to} 3 liters · hr ^-1 . When the space velocity is less than 0.1 hr ⁻¹ , the amount of wastewater treated is reduced, and excessive facilities are required. On the other hand, when it exceeds 10 hr ⁻¹ , the oxidation and decomposition treatment of nitrogen-containing compounds is not efficient. Absent.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, if there exists an effect of this invention, it will not be limited to a present Example.

Example 1
Commercially available titanium oxide (TiO ₂ ) was impregnated and supported with 1.3% by mass of ruthenium (Ru) and 3.5% by mass of zirconium oxide (ZrO ₂ ). Ruthenium nitrate (Ru) and zirconium nitrate were used as precursors for the noble metal (Ru) and the active assistant (ZrO ₂ ). The impregnated and supported catalyst was calcined in air at 300 ° C. for 3 hours, and subjected to hydrogen reduction in a mixed gas of hydrogen and nitrogen (hydrogen: 5% by volume) at the same temperature for 3 hours to obtain a catalyst. The composition of the obtained catalyst is shown in Table 1.

(Example 2)
Composite oxide of iron oxide (Fe ₂ O ₃ ), bismuth oxide (Bi ₂ O ₃ ) and indium oxide (In ₂ O ₃ ) prepared by coprecipitation method [mass ratio of iron oxide: bismuth oxide: indium oxide = 87: 8: 5] was impregnated with 0.8% by mass of palladium (Pd) and 5.5% by mass of cerium oxide (CeO ₂ ). Palladium nitrate and cerium nitrate were used as precursors for the noble metal (Pd) and the active auxiliary agent (CeO ₂ ). The impregnated and supported catalyst was calcined in air at 400 ° C. for 4 hours, and subjected to hydrogen reduction in a mixed gas of hydrogen and nitrogen (hydrogen: 5% by volume) at 300 ° C. for 3 hours to obtain a catalyst. The composition of the obtained catalyst is shown in Table 1. Further, the pore volume of the porous inorganic oxide (Fe ₂ O ₃ —Bi ₂ O ₃ —In ₂ O ₃ ) and the average particle diameter of the active auxiliary agent (CeO ₂ ) are shown in Table 2.

( Reference Example 3)
A catalyst having the same composition as in Example 1 was prepared in the same manner as in Example 1 except that the calcination temperature after supporting the noble metal and the active auxiliary agent was 200 ° C. The composition of the obtained catalyst is shown in Table 1. Further, the pore volume of the porous inorganic oxide (TiO ₂ ) and the average particle diameter of the active auxiliary agent (ZrO ₂ ) are shown in Table 2.

(Comparative Example 1)
Aluminum oxide (Al ₂ O ₃ ) was impregnated with iridium (Ir). An iridium nitrate solution was used as a noble metal (Ir) precursor. The impregnated catalyst was calcined in air at 400 ° C. for 3 hours, and then subjected to hydrogen reduction in a mixed gas of hydrogen and nitrogen (hydrogen: 5% by volume) at 300 ° C. for 2 hours to obtain a catalyst. The composition of the obtained catalyst is shown in Table 1. The pore volume of the porous inorganic oxide (Al ₂ O ₃ ) is shown in Table 2.

(Comparative Example 2)
Commercially available titanium oxide (TiO ₂ ) was impregnated with ruthenium (Ru). A ruthenium nitrate solution was used as a noble metal (Ru) precursor. The impregnated and supported catalyst was calcined in air at 300 ° C. for 3 hours, and subjected to hydrogen reduction in a mixed gas of hydrogen and nitrogen (hydrogen: 5% by volume) at the same temperature for 3 hours to obtain a catalyst. The composition of the obtained catalyst is shown in Table 1. The pore volume of the porous inorganic oxide (TiO ₂ ) is shown in Table 2.

(Wastewater treatment method 1)
Using the processing apparatus shown in FIG. 1, this reaction tower 5 is filled with 1 liter of the catalyst 5.1 obtained in Examples 1 to 3 and Comparative Examples 1 and 2 and processed under the following processing conditions. Performed continuously for 1200 hours. Detailed experimental methods and results are described below. The waste water used for the treatment was ammonia water, and was pressure-fed at a flow rate of 1 liter / hr from the waste water supply line 1 by the waste water supply pump 2. On the other hand, air pressurized by a compressor was supplied from the oxidant supply line 3. After this gas-liquid mixture was heated by the heat exchanger 4, it was introduced into the reaction tower 5 packed with the catalyst 5.1 and wet-oxidized at a treatment temperature of 250 ° C. The liquid to be treated was cooled by the heat exchanger 4 and the heat exchanger (cooler) 6 and then introduced into the gas-liquid separator 7. In the gas-liquid separator 7, the liquid level controller (LC) detects the liquid level and operates the liquid level control valve 8 to maintain a constant liquid level, and the pressure controller (PC) detects the pressure to detect the pressure. The control valve 9 was operated to operate so as to maintain a pressure of 7.0 MPa (Gauge). The ammonia concentration and the air supply amount were changed with the lapse of treatment time. Table 3 shows the processing conditions.

  The treatment results were as shown in Tables 4 and 5. In Table 2 below, the total nitrogen treatment efficiency, ammonia nitrogen residual amount, nitrate nitrogen production amount, and nitrite nitrogen production amount after 300, 600, 900, and 1200 hours have been measured by the following methods, respectively. did.

<Measurement of total nitrogen concentration>
The total nitrogen concentration was quantified using a total nitrogen measuring device. Moreover, the calculation method of the total nitrogen treatment efficiency is as follows.

<Measurement of residual amount of ammonia nitrogen>
The amount of residual ammonia nitrogen was determined by ion chromatography analysis.

<Measurement of nitrate nitrogen production>
Nitrate nitrogen production was quantified by ion chromatography analysis.

<Measurement of nitrite nitrogen production>
The amount of nitrite nitrogen produced was determined by ion chromatography analysis.

Example 4
To a composite oxide of titanium oxide (TiO ₂ ) and iron oxide (Fe ₂ O ₃ ) prepared by a coprecipitation method (mass ratio of titanium oxide: iron oxide = 20: 80), 1.5 mass of palladium (Pd). % And 2.4% by mass of cerium oxide (CeO ₂ ) were impregnated and supported. A palladium nitrate solution and cerium nitrate were used as precursors for the noble metal (Pd) and the active auxiliary agent (CeO ₂ ). The impregnated catalyst was calcined in air at 400 ° C. for 3 hours, and then subjected to hydrogen reduction in a mixed gas of hydrogen and nitrogen (hydrogen: 5% by volume) at 300 ° C. for 2 hours to obtain a catalyst. The composition of the obtained catalyst is shown in Table 6. Further, the pore volume of the porous inorganic oxide (TiO ₂ —Fe ₂ O ₃ ) and the average particle diameter of the active auxiliary agent (CeO ₂ ) are shown in Table 7.

(Example 5)
To the composite oxide of cerium oxide (CeO ₂ ) and zirconium oxide (ZrO ₂ ) prepared by the coprecipitation method (mass ratio of cerium oxide: zirconium oxide = 35: 65), ruthenium (Ru) 1.0 mass% and Titanium oxide (TiO ₂ ) 3.0% by mass was impregnated and supported. A ruthenium nitrate solution and titanium tetrachloride were used as precursors for the noble metal (Ru) and the active auxiliary agent (TiO ₂ ). The impregnated and supported catalyst was calcined in air at 500 ° C. for 3 hours, and subjected to hydrogen reduction in a mixed gas of hydrogen and nitrogen (hydrogen: 5% by volume) at 300 ° C. for 2 hours to obtain a catalyst. The composition of the obtained catalyst is shown in Table 6. Table 7 shows the pore volume of the porous inorganic oxide (CeO ₂ —ZrO ₂ ) and the average particle diameter of the active auxiliary agent (TiO ₂ ).

(Example 6)
Commercially available lanthanum oxide (La ₂ O ₃ ) was impregnated with 1.8% by mass of silver (Ag) and 4.0% by mass of manganese oxide (MnO ₂ ). Silver acetate and manganese nitrate were used as precursors for the noble metal (Ag) and the active auxiliary agent (MnO ₂ ). The impregnated and supported catalyst was calcined in air at 400 ° C. for 2 hours, and subjected to hydrogen reduction in a mixed gas of hydrogen and nitrogen (hydrogen: 5% by volume) at 300 ° C. for 3 hours to obtain a catalyst. The composition of the obtained catalyst is shown in Table 6. Further, the pore volume of the porous inorganic oxide (La ₂ O ₃ ) and the average particle diameter of the active auxiliary agent (MnO ₂ ) are shown in Table 7.

( Reference Example 7)
Commercially available silicon oxide (SiO ₂ ) was impregnated with 1.6% by mass of ruthenium (Ru) and 4.0% by mass of lanthanum oxide (La ₂ O ₃ ). Ruthenium chloride and lanthanum nitrate were used as precursors for the noble metal (Ru) and the active auxiliary agent (La ₂ O ₃ ). The catalyst after impregnation was supported by hydrogen reduction in a mixed gas of hydrogen and nitrogen (hydrogen: 5% by volume) at 400 ° C. for 2 hours to obtain a catalyst. The composition of the obtained catalyst is shown in Table 6. Further, the pore volume of the porous inorganic oxide (SiO ₂ ) and the average particle diameter of the active auxiliary agent (La ₂ O ₃ ) are shown in Table 7.

( Reference Example 8)
Commercially available aluminum oxide (Al ₂ O ₃ ), zinc oxide (ZnO) and yttrium oxide (Y ₂ O ₃ ) were mixed intimately at a mass ratio of aluminum oxide: zinc oxide: yttrium oxide = 55: 35: 10. The mixed oxide was impregnated with 1.2% by mass of palladium (Pd) and 2.5% by mass of indium oxide (In ₂ O ₃ ). Palladium nitrate and indium nitrate were used as precursors for the noble metal (Pd) and the active assistant (In ₂ O ₃ ). The impregnated and supported catalyst was calcined in air at 500 ° C. for 3 hours, and subjected to hydrogen reduction in a mixed gas of hydrogen and nitrogen (hydrogen: 5% by volume) at 300 ° C. for 3 hours to obtain a catalyst. The composition of the obtained catalyst is shown in Table 6. Further, the pore volume of the porous inorganic oxide (Al ₂ O ₃ —ZnO—Y ₂ O ₃ ) and the average particle diameter of the active auxiliary agent (In ₂ O ₃ ) are shown in Table 7.

(Wastewater treatment method 2)
Using the processing apparatus shown in FIG. 1, 1 liter of the catalyst 5.1 obtained in the above Examples 4 to 8 is filled in the reaction tower 5 and the processing is continuously performed for 900 hours under the following processing conditions. It was. Detailed experimental methods and results are described below. The waste water used for the treatment was ammonia water and monoethanolamine (MEA), and was pressure-fed at a flow rate of 2 liter / hr from the waste water supply line 1 by the waste water supply pump 2. On the other hand, air pressurized by a compressor was supplied from the oxidant supply line 3. After this gas-liquid mixture was heated by the heat exchanger 4, it was introduced into the reaction tower 5 packed with the catalyst 5.1 and wet-oxidized at a treatment temperature of 250 ° C. The liquid to be treated was cooled by the heat exchanger 4 and the heat exchanger (cooler) 6 and then introduced into the gas-liquid separator 7. In the gas-liquid separator 7, the liquid level controller (LC) detects the liquid level and operates the liquid level control valve 8 to maintain a constant liquid level, and the pressure controller (PC) detects the pressure to detect the pressure. The control valve 9 was operated to operate so as to maintain a pressure of 7.0 MPa (Gauge). Ammonia and monoethanolamine concentrations were changed over time. Table 8 shows the processing conditions.

  The treatment results were as shown in Table 9. In Table 9 below, the total nitrogen treatment efficiency, ammonia nitrogen residual amount, nitrate nitrogen production amount, and nitrite nitrogen production amount after 300, 600, and 900 hours elapsed are as described in Example 1 above. It was measured by the method.

Example 9
The composite oxide of zirconium oxide (ZrO ₂ ) and titanium oxide (TiO ₂ ) prepared by the coprecipitation method [mass ratio of zirconium oxide: titanium oxide = 45: 55], ruthenium (Ru) 0.8 mass% and It impregnated and supported 2.5% by mass of cerium oxide (CeO ₂ ). Ruthenium nitrate solution and cerium nitrate were used as precursors for the noble metal (Ru) and the active auxiliary agent (CeO ₂ ). The impregnated and supported catalyst was calcined in air at 300 ° C. for 4 hours, and subjected to hydrogen reduction in a mixed gas of hydrogen and nitrogen (hydrogen: 5% by volume) at 300 ° C. for 2 hours to obtain a catalyst. The composition of the obtained catalyst is shown in Table 10. The pore volume of the porous inorganic oxide (ZrO ₂ —TiO ₂ ) and the average particle diameter of the active auxiliary agent (CeO ₂ ) are shown in Table 11.

(Example 10)
To a composite oxide of titanium oxide (TiO ₂ ), manganese oxide (MnO ₂ ) and nickel oxide (NiO) prepared by a coprecipitation method [mass ratio of titanium oxide: manganese oxide: nickel oxide = 75: 20: 5] Then, 1.3% by mass of palladium (Pd) and 2.5% by mass of yttrium oxide (Y ₂ O ₃ ) were impregnated and supported. Palladium chloride and yttrium chloride were used as precursors for the noble metal (Pd) and the active auxiliary agent (Y ₂ O ₃ ). The impregnated and supported catalyst was calcined in air at 500 ° C. for 4 hours, and subjected to hydrogen reduction in a mixed gas of hydrogen and nitrogen (hydrogen: 5% by volume) at 300 ° C. for 3 hours to obtain a catalyst. The composition of the obtained catalyst is shown in Table 10. Further, the pore volume of the porous inorganic oxide (TiO ₂ —MnO ₂ —NiO) and the average particle diameter of the active auxiliary agent (Y ₂ O ₃ ) are shown in Table 11.

(Example 11)
Zirconium oxide (ZrO ₂ ) prepared by the precipitation method was impregnated and supported with 0.9% by mass of iridium (Ir) and 3.0% by mass of titanium oxide (TiO ₂ ). Iridium chloride and titanium tetrachloride were used as precursors for the noble metal (Ir) and the active auxiliary agent (TiO ₂ ). The impregnated and supported catalyst was calcined in air at 350 ° C. for 3 hours, and then subjected to hydrogen reduction in a mixed gas of hydrogen and nitrogen (hydrogen: 5% by volume) at 400 ° C. for 2 hours to obtain a catalyst. The composition of the obtained catalyst is shown in Table 10. The pore volume of the porous inorganic oxide (ZrO ₂ ) and the average particle diameter of the active auxiliary agent (TiO ₂ ) are shown in Table 11.

(Example 12)
Commercially available zirconium oxide (ZrO ₂ ) was impregnated and supported with 0.9% by mass of rhodium (Rh) and 2.0% by mass of iron oxide (Fe ₂ O ₃ ). Rhodium nitrate and iron nitrate were used as precursors for the noble metal (Rh) and the active auxiliary agent (Fe ₂ O ₃ ). The impregnated and supported catalyst was calcined in air at 500 ° C. for 4 hours, and subjected to hydrogen reduction in a mixed gas of hydrogen and nitrogen (hydrogen: 5% by volume) at 300 ° C. for 3 hours to obtain a catalyst. The composition of the obtained catalyst is shown in Table 10. The pore volume of the porous inorganic oxide (ZrO ₂ ) and the average particle diameter of the active auxiliary agent (Fe ₂ O ₃ ) are shown in Table 11.

(Example 13)
To a composite oxide of iron oxide (Fe ₂ O ₃ ) and cobalt oxide (Co ₃ O ₄ ) prepared by a coprecipitation method (mass ratio of iron oxide: cobalt oxide = 93: 7), silver (Ag) 5% by mass and 2.0% by mass of zinc oxide (ZnO) were supported. A liquid in which silver acetate and zinc nitrate were dissolved was absorbed in the composite oxide, and ammonia water was added dropwise to precipitate silver and cobalt hydroxides. The supported catalyst was calcined in air at 400 ° C. for 5 hours, and subjected to hydrogen reduction at 300 ° C. for 3 hours in a mixed gas of hydrogen and nitrogen (hydrogen: 5% by volume) to obtain a catalyst. The composition of the obtained catalyst is shown in Table 10. Table 11 shows the pore volume of the porous inorganic oxide (Fe ₂ O ₃ —Co ₃ O ₄ ) and the average particle diameter of the active auxiliary agent (ZnO).

(Wastewater treatment method 3)
Using the processing apparatus shown in FIG. 1, 1 liter of the catalyst 5.1 obtained in Examples 9 to 13 was charged into the reaction column 5 and the processing was continuously performed for 900 hours under the following processing conditions. It was. Detailed experimental methods and results are described below. The wastewater used for the treatment was methyldiethanolamine (MDEA), and was pressure-fed at a flow rate of 2 liter / hr from the wastewater supply line 1 by the wastewater supply pump 2. On the other hand, air pressurized by a compressor was supplied from the oxidant supply line 3. After this gas-liquid mixture was heated by the heat exchanger 4, it was introduced into the reaction tower 5 packed with the catalyst 5.1 and wet-oxidized at a treatment temperature of 250 ° C. The liquid to be treated was cooled by the heat exchanger 4 and the heat exchanger (cooler) 6 and then introduced into the gas-liquid separator 7. In the gas-liquid separator 7, the liquid level controller (LC) detects the liquid level and operates the liquid level control valve 8 to maintain a constant liquid level, and the pressure controller (PC) detects the pressure to detect the pressure. The control valve 9 was operated to operate so as to maintain a pressure of 7.0 MPa (Gauge). The methyldiethanolamine concentration was changed with the lapse of treatment time. Table 12 shows the processing conditions.

  The processing results were as shown in Table 13. In Table 13, the total nitrogen treatment efficiency, ammonia nitrogen residual amount, nitrate nitrogen production amount, and nitrite nitrogen production amount after 300, 600, and 900 hours elapsed are as described in Example 1 above. It was measured by the method.

The present invention can be used for wastewater treatment, preferably for treatment of wastewater containing a nitrogen-containing compound.

1: drainage supply line,
2: Wastewater supply pump,
3: Oxidant supply line,
4: Heat exchanger
5: Reaction tower (reactor),
5.1: catalyst,
6: heat exchanger,
7: Gas-liquid separator
8: Liquid level control valve,
9: Pressure control valve.

Claims (4)

It is characterized by coating a noble metal and an active aid on a porous inorganic oxide,
The active aid is at least one oxide selected from the group consisting of titanium, iron, zirconium, cobalt, nickel, cerium, lanthanum, manganese, yttrium, zinc and bismuth, or at least two composites selected from the above group An oxide,
A wastewater treatment catalyst containing a nitrogen-containing compound, wherein the active auxiliary agent has an average particle diameter of 25 to 50 nm. The wastewater treatment catalyst containing a nitrogen-containing compound according to claim 1, wherein the porous inorganic oxide has a pore volume of 0.12 to 0.5 ml / g. A method for producing a catalyst for treating a nitrogen-containing compound according to claim 1 or 2,
The porous inorganic oxide is coated with the noble metal component and the active auxiliary agent by simultaneously impregnating the porous inorganic oxide with the noble metal component and the active auxiliary agent,
Further comprising adopting at least one step of heat treatment at a temperature of 300 ° C. or higher in an oxidizing atmosphere after impregnating and supporting the active assistant,
A method for producing a catalyst for treating a nitrogen-containing compound, comprising a step of reducing the noble metal component in a reducing atmosphere after the heat treatment step.   Using the catalyst according to claim 1 or 2, wastewater containing a nitrogen-containing compound is contained in the wastewater in the presence of an oxidant at a temperature of 100 ° C or higher and lower than 370 ° C and pressure condition that the wastewater maintains a liquid phase. A wastewater treatment method comprising treating a nitrogen compound.