JPH03224693A - Treatment of waste water - Google Patents

Abstract

PURPOSE:To efficiently treat waste water by carrying out treatment with gas contg. molecular oxygen in the presence of a solid catalyst composed of a catalytic component made of titanium oxide, a catalytic component made of the oxide of lanthanoid and a catalytic component contg. a metal such as Mn or Fe. CONSTITUTION:A solid catalyst for treatment of waste water is composed of a first catalytic component made of titanium oxide, a second catalytic component made of the oxide of lanthanoid and a third catalytic component contg. a metal selected among Mn, Fe, Co, Ni, Cu, W, Ag, Au, Pt, Pd, Rh, Ru and Ir or a water insoluble or slightly soluble compd. of the metal. Waste water is subjected to wet oxidation treatment with gas contg. molecular oxygen in the presence of the solid catalyst at <=370 deg.C under the pressure required to maintain the liq. phase of the waste water. The gas is fed by an amt. 1.0-1.5 times the theoretical amt. required to decompose org. and inorg. substances in the waste water into N2, CO2 and water.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for wet oxidizing wastewater containing chemical oxygen demand substances (hereinafter referred to as COD components) in the presence of a catalyst. Specifically, the present invention performs catalytic wet oxidation of wastewater containing harmful oxidizable organic or inorganic substances, which are COD components, in the coexistence of molecular oxygen, thereby converting these organic substances into harmless carbon dioxide gas and water. This invention relates to an effective method for making wastewater pollution-free by converting it into nitrogen and the like.

(Prior Art) Known wastewater treatment methods include a biochemical method called an activated sludge method and a wet oxidation method called a Zimmerman method.

As is well known, the activated sludge method requires a long time to decompose organic matter, and the wastewater must be diluted to a concentration suitable for the growth of algae and bacteria, so the installed area of the activated sludge treatment facility is large. There are drawbacks to it. Furthermore, in recent years, particularly in urban areas, handling of grown surplus sludge has required significant processing costs. On the other hand, the Zimmerman method is a method in which air is introduced into an aqueous solution containing a high concentration of organic matter at a pressure of 20 to 200 atm and a temperature of 200 to 370°C to oxidize and decompose the organic matter, but this method has a slow reaction rate; Since decomposition takes a long time, a large reactor is required, and the material required has a high degree of durability, which causes economical problems in equipment costs and operating costs. Also,
In this method, methods using various oxidation catalysts have been proposed for the purpose of accelerating the reaction rate.

Conventionally, noble metal compounds such as palladium and platinum have been used as catalysts in catalytic wet oxidation methods (Japanese Patent Laid-Open No. 49-44-55).
No. 6) and compounds of noble metals such as cobalt and iron (Japanese Patent Application Laid-open No. 1984-94,157) are known. These catalysts are catalysts in which the above compound is supported on a spherical or cylindrical carrier such as alumina, silica alumina, silica gel, or activated carbon. In the case of catalytic wet oxidation of wastewater, the reaction is often carried out at a pH of 9 or higher, and according to the studies of the present inventors, the above-mentioned catalysts deteriorate in strength and become crushed into powder when used for a long period of time, and furthermore, the carrier deteriorates. Dissolution may also occur. For example, alumina-based catalysts tend to suffer from a decrease in strength due to elution of alumina.

Recently, in an attempt to solve these problems, a method using titania or zirconia as a carrier has been proposed (Japanese Unexamined Patent Publication No. 58-64,188). according to this,
A catalyst is disclosed in which a noble metal compound such as palladium or platinum, or a transition metal compound such as iron or cobalt is supported on a spherical or cylindrical titania or zirconia carrier. This invention certainly has superior strength compared to conventional carriers. However, all of these catalysts have a granular shape. Moreover, the catalyst activity and durability are not fully satisfactory. For example, titania-based catalysts tend to suffer from a decrease in strength due to titania crystal changes.

There are also examples in which oxides of lanthanide elements are used as catalysts, but these are not fully satisfactory in terms of physical durability and moldability.

As a method to improve these, TiO2-ZrO2, Ti
A method of combining complex oxides such as O2-8i02-Zr02 and Ti02ZnO with cerium compounds (JP-A-63-158.189 and JP-A-1-218.
Nos. 684 to 218,686) have been proposed, and both durability and activity are greatly improved. However, in some cases, the initial activity was inferior to a catalyst in which a catalytically active substance was supported on ceria alone.

By the way, when wet oxidizing wastewater, it is necessary to treat a large amount of water. Therefore, as a reaction mode, a fixed bed system with a flow system is often adopted, and solid matter is often contained in the wastewater. In these cases, if the catalyst is granular, the pressure loss due to the flow of wastewater is large and the wastewater cannot be treated at a high linear velocity.Therefore, it is necessary to have a large cross-sectional area for the wastewater flow, which increases the area occupied by the reactor. Furthermore, in the case of wastewater treatment in which solid matter coexists, there are disadvantages such as increased flow resistance due to clogging, leading to increased running costs, and furthermore, making long-term operation of the treatment equipment impossible. That is, in wastewater treatment using the catalytic wet oxidation method, since the reaction is carried out at high temperature and high pressure, an increase in the area occupied by the reactor leads to an increase in equipment cost, which is a fatal problem.

In addition, a fluidized bed method has been proposed in which a powdered catalyst is fluidized in order to reduce the pressure loss caused by the catalyst layer, but this method requires a large reactor because the concentration of the catalyst is thin.
Furthermore, it has the disadvantage that it is difficult to separate the catalyst from the treated wastewater, and it has not been put into practical use.

On the other hand, using ozone or hydrogen peroxide as the oxidizing agent,
Another method is to oxidize and decompose organic matter in wastewater at room temperature and pressure. For example, in JP-A No. 58-55゜088, wastewater containing organic substances such as humic acid is treated with ozone and hydrogen peroxide in the absence of a catalyst at 20°C and under normal pressure. A method for oxidative decomposition of Furthermore, in Japanese Patent Publication No. 58-37,039, a surfactant is added to wastewater containing an organic compound having an aromatic ring, and at least one selected from a transition metal compound and an alkaline earth compound is further added. A method is described in which, after mixing, the mixture is brought into contact with ozone at normal temperature and pressure to oxidatively decompose the organic compound.

Since the former process is carried out in the absence of a catalyst, it is not possible to treat substances that are difficult to oxidize, such as suspended matter in wastewater. The latter uses metal ions such as transition metals or alkaline earth metals as catalysts, so it has the disadvantage of requiring a post-treatment process, as it is necessary to recover the metal ions after treatment of the wastewater rather than releasing them as is. There is. In addition, since both wastewater treatments are carried out at room temperature and pressure, they require a large amount of expensive ozone, the reaction rate is slow, the decomposition rate of organic matter is low, and unreacted ozone is generated. It has drawbacks such as requiring detoxification treatment.

(Problems to be Solved by the Invention) Therefore, an object of the present invention is to provide a method for efficiently treating wastewater over a long period of time.

Another object of the present invention is to provide a method for efficiently treating wastewater with high linear velocity dust.

A further object of the present invention is to provide a method for stably treating wastewater containing solids with high linear velocity dust over a long period of time.

(Means for solving the problem) These various components include a first catalyst component made of titanium oxide, a second catalyst component made of an oxide of a lanthanide element, and manganese, iron, cobalt, nickel, tungsten, and copper. , the presence of a solid catalyst comprising a third catalyst component comprising at least one metal selected from the group consisting of silver, gold, platinum, palladium, rhodium, ruthenium and iridium, or a water-insoluble or sparingly soluble compound thereof; At least one substance selected from the group consisting of organic substances and inorganic substances in the wastewater is heated to a temperature of 370° C. or lower and under a pressure such that the wastewater maintains a liquid phase.
1 of the theoretical amount required to decompose into carbon dioxide gas and water
．． This is achieved by a method for treating wastewater which comprises wet oxidizing the wastewater with a gas containing 0 to 1.5 times the amount of molecular oxygen.

The present invention also provides a method for treating wastewater in which the catalyst has an integral structure. Furthermore, the present invention provides wastewater treatment in which the catalyst is a honeycomb type catalyst having a shape in which the equivalent diameter of the through holes is 2 to 20 mm, the cell wall thickness is 0.5 to 3 mm, and the aperture ratio is in the range of 50 to 80%. It's a method. Furthermore, the present invention provides that upon passing wastewater through the catalyst together with an oxygen-containing gas,
This is a wastewater treatment method that allows ozone and/or hydrogen peroxide to coexist.

(Function) The catalyst used in the present invention contains titanium oxide as the first catalyst component, an oxide of a rank-made element as the second catalyst component, and manganese, iron, cobalt, nickel, and tungsten as the third catalyst component. , copper, silver, gold, platinum, palladium, rhodium, ruthenium, and iridium, or a water-insoluble or sparingly soluble compound thereof.

The BET surface area of titanium oxide, which is the first catalyst component constituting the catalyst used in the present invention, is preferably 10 m2/g or more, particularly preferably 30 to 120 m2/g.

As the second catalyst component, one or more oxides of rank-made elements such as lanthanum, cerium, praseodymium, neodymium, samarium, etc. can be used to increase the catalyst stability, but in particular lanthanum, cerium and samarium. At least one oxide selected from the group consisting of neodymium is preferred because it is more effective in increasing catalyst stability and catalyst activity.

The ratio of each catalyst component in the catalyst used in the present invention is
5 to 98% by weight of the second catalyst component in the form of an oxide, 2 to 95% by weight of the second catalyst component in the form of an oxide, and 0.05 to 25% by weight of the third catalyst component in the form of a metal or compound. A range of % is appropriate. Preferably, among the elements constituting the third catalyst component, the amount of manganese, iron, cobalt, nickel, tungsten, copper, and silver used is 0 to 25% by weight as a compound (e.g., oxide, sulfide, etc.). The amount of platinum, gold, palladium, rhodium, ruthenium and iridium used is 0 to 10% by weight as metals (however,
The total amount of both is 0.05 to 25%. ). More preferably, the first catalyst component is in the form of an oxide of 10 to 96
% by weight, 4-90% by weight of the second catalyst component in oxide form
, the third catalyst component is in the form of a metal or a compound of 0.1 to 9
Weight%. Even more preferably, the first catalyst component is in the form of an oxide from 10 to 84% by weight, the second catalyst component is in the form of an oxide and the third catalyst component is in the form of a metal or a compound. It is 0.1 to 9% by weight. Preferably, among the metals constituting the third catalyst component, the amount of manganese, iron, cobalt, nickel, tungsten, copper, and silver used as a compound is 0 to 9% by weight, and platinum,
The amount of gold, palladium, rhodium, ruthenium, and iridium used is 0 to 5% by weight as metals (however, the total amount of both is 0.1 to 9% by weight). Note that the total amount of the first catalyst component, second catalyst component, and third catalyst component is 1
00% by weight.

If the third catalyst component is outside the above range, the oxidation activity will be insufficient, and in the case of noble metals such as platinum, palladium, and rhodium, the raw material cost will be high and a correspondingly sufficient effect cannot be exhibited. Furthermore, if the first catalyst component and the second catalyst component are outside the above range, the hot water resistance will be poor, which is not preferable in terms of catalyst life.

The catalyst used in the present invention preferably has the composition specified above, and the catalyst shape is pellets,
Various shapes such as a spherical shape, a ring shape, a saddle shape, a powder shape, a crushed type, and an integral structure such as a honeycomb can be adopted. Preferably, it is a honeycomb type tank body, and particularly preferably, in the structure, the equivalent diameter of the through hole is 2 to 20+n+n,
Preferably it is in the range of 4 to 12 mm. Equivalent diameter is 2m
If the diameter is less than 20 mm, the pressure loss will be large, and clogging is likely to occur, especially if solid content is contained in the wastewater (which makes long-term use difficult. If the equivalent diameter exceeds 20 mm, Although the pressure loss is smaller and the possibility of clogging is lower, in order to achieve a certain level of processing efficiency,
It is necessary to increase the amount of catalyst by increasing the pore diameter, and the pore diameter is limited by the relationship between treatment efficiency and the performance of the catalyst itself.

Cell wall thickness is 0.5 to 3 mm, preferably 0.5 to 2 mm
is within the range of When the cell wall thickness is less than 0.5 mm, the pressure loss is small (which has the advantage of reducing the weight of the catalyst, but it is not preferable because the mechanical strength decreases. When the cell wall thickness exceeds 3 mm) Although it has sufficient mechanical strength, it has the disadvantage of large pressure loss.

For the same reason as above, the aperture ratio is also 50 to 80%, preferably 62 to 76%.

Taking into consideration the above circumstances, a particularly preferable honeycomb type catalyst used in the present invention has an equivalent diameter of through holes of 2.
~20 mm, cell thickness is in the range of 0.5 to 3 mm, and aperture ratio is in the range of 50 to 80%. A honeycomb type catalyst that meets these conditions has a reaction temperature of 100 to 370°C,
It has sufficient mechanical strength even under severe reaction conditions of high temperature and pressure, where the reaction pressure is higher than the pressure that maintains the liquid phase of wastewater, and the catalyst has sufficient geometric surface area. In addition, it has excellent durability and can process wastewater at high linear speeds with low pressure loss. Moreover, even when solid content is contained in wastewater, high activity can be maintained for a long period of time without clogging.

As for the shape of the through-hole, any shape such as square, hexagonal, wave-like, etc. can be adopted as long as its equivalent diameter is within the above-mentioned range.

In the present invention, when molecular oxygen, ozone, and/or hydrogen peroxide are used as oxidizing agents, organic substances that are relatively resistant to oxidation, such as acetic acid, can be decomposed with high efficiency, and also at relatively low temperatures. , is preferred because the reaction can be carried out at low pressure.

Furthermore, since the catalyst used in the present invention has the ability to decompose ozone into oxygen, it also has the advantage of substantially decomposing waste ozone and preventing it from being discharged outside the system. That's true.

The amount of ozone used is 0.001 to 1.2 times the theoretical amount of oxygen required to decompose organic and inorganic substances in wastewater into nitrogen, carbon dioxide, and water, preferably 0.0
03 to 0.6 times the mole amount is sufficient. The amount of hydrogen peroxide used is 0.001 to 1.8 of the theoretical oxygen amount.
It is sufficient to use twice the mole, preferably 0.003 to 0.2 times the mole. By using ozone and/or hydrogen peroxide together with molecular oxygen, the reaction temperature varies depending on the properties of the wastewater, the amount of the oxidizing agent used, etc.
This is lower than when only molecular oxygen is used. for example,
The reaction temperature when using molecular oxygen is 200℃~300℃
℃, if the oxidizing agent is used in combination, the temperature will be 100°0~25
The temperature will be around 0℃.

Inorganic titanium compounds such as titanium chlorides, titanium sulfate, titanium hydroxide, titanium oxide, and titania sol, and organic titanium compounds such as titanium oxalate and tetraisopropyl titanate are used as starting materials for titanium used as the first catalyst component in the present invention. You can choose from.

In the present invention, starting materials for the lanthanide elements used as the second catalyst component include oxides, hydroxides, inorganic chlorides, etc. For example, taking cerium as an example, raw materials include cerium acetate and cerium nitrate. You can choose from , cerium sulfate, cerium oxide, ceria sol, etc. Moreover, as a preferable method of adding these titanium oxides, the following method can be mentioned.

(2) A method in which salts of lanthanide elements are dissolved in a titanium salt solution, ammonia is added thereto to form a precipitate, the precipitate is washed, dried, and then calcined at 300 to 9° OoC. (2) A method in which a fine powder of an oxide of a lanthanide element is suspended in a titanium salt solution, ammonia is added thereto to form a precipitate, the precipitate is washed, dried, and then calcined at 300 to 900°C.

(2) A method in which unfired TiO2 is impregnated with a salt solution of a lanthanide element, then dried and fired at 300 to 900°C.

(2) A method in which fine powder of an oxide of a lanthanide element is added to unfired TiO2, wet or dry pulverized and mixed in a ball mill, and after drying, fired at 300 to 900°C.

(2) A method in which pre-fired Ti 02 is impregnated with a salt solution of a lanthanide element, then dried and fired at 300 to 9000C. Further, during this impregnation, a mixed solution of the third catalyst component with a salt solution may be used. Among the above preferred methods, methods (1) to (4) are preferred. Among these, ■ is particularly preferred.

In addition, in the starting material of the third catalyst component and 12, an oxide,
Examples include hydroxides, inorganic acid salts, organic acid salts, etc., and are appropriately selected from, for example, ammonium salts, oxalates, nitrates, sulfates, and halides.

Further, when catalyzing the first catalyst component and the second catalyst component by adding manganese, iron, nickel, cobalt, tungsten, copper, silver, gold, platinum, palladium, rhodium, ruthenium and/or iridium, A catalyst can be obtained by impregnating and supporting a molded body consisting of a first catalyst component and a second catalyst component with an aqueous solution of the metal salt, followed by drying and firing.

On the other hand, a method is also used in which a carrier made of the first catalyst component is impregnated with a mixed aqueous solution of metal salts of the second catalyst component and the third catalyst component, supported, and then dried and calcined.

Alternatively, an aqueous solution of the metal salt may be added to the powder consisting of the first catalyst component and the second catalyst component together with a molding aid, and the mixture may be kneaded and molded.

Further, the catalyst used in the present invention includes a powder or a molded body in which the first catalyst component and the second catalyst component are combined.
By firing in the range of 00 to 900'C, physical durability under reaction conditions can be further improved.

According to the present invention, supernatant water treated with activated sludge or precipitated activated sludge, fermentation wastewater, wastewater from organic compound polymerization processes, cyanide-containing wastewater, phenol-containing wastewater, oil-containing wastewater, and other chemical factory wastewater as well as food factories Wet oxidation treatment can be applied to general industrial wastewater from sources such as the like, as well as wastewater containing oxidizable organic or inorganic substances such as human waste, sewage, and sewage sludge. Further, when a honeycomb type catalyst is used in the present invention, even wastewater containing solid matter of 0.1 g/Ω or more can be treated stably over a long period of time.

The reaction conditions in the present invention are that the reaction temperature is 370°C or less;
Usually 100-370℃, more preferably 160-300℃
It is ℃. The pressure of the reaction system is sufficient to maintain the liquid phase of the waste water in the reaction tower, that is, 1 to about 230 kg/co? The pressure is fine. The amount of molecular oxygen-containing gas to be fed is 1 to 1.5 times the theoretical amount of oxygen required for oxidative decomposition. The amount of catalyst used is about 5 to 99% of the space volume of the reaction column. The wastewater is oxidized by flowing it with molecular oxygen-containing gas through a catalyst bed at a predetermined temperature for a residence time of 2 to 120 minutes, preferably 4 to 60 minutes.

The molecular oxygen-containing gas may be air, a mixture of oxygen and air, or a gas commonly referred to as oxygen-enriched air. The pH of the reaction system can be either acidic or alkaline, but PTL is preferably in the range of 9 or less, more preferably 7 or less.

The reaction conditions when ozone and/or hydrogen peroxide are used together as oxidizing agents with molecular oxygen are usually 10
In the temperature range of 0°C to 250°C, the reaction pressure is sufficient to maintain the liquid phase of the wastewater in the reaction tower, i.e. 1 to 200 kg.
/ctB pressure and residence time are 3 to 120 minutes, preferably 5 to 60 minutes. The amount of ozone used is 0.001 to 1.2 times the mole based on the theoretical oxygen amount, preferably 0.
．． The range is 0.003 to 0.6 times the mole. The amount of hydrogen peroxide used is 0.001 to 1.8 times the mole based on the theoretical amount of oxygen.
Preferably it is in the range of 0.003 to 0.2 times the mole.

(Examples) The present invention will be described in more detail below using Examples and Comparative Examples, but the present invention is not limited only to these Examples.

Example 1 An oxide consisting of titanium and cerium was prepared by the method described below. A sulfuric acid aqueous solution of titanyl sulfate having the following composition was used as a titanium source.

TiO3O4 (TiO2 conversion) 250g/! Q Total 11□So41100g/U Add cerous nitrate (Ce (NO3)3 to 100p of water
・61120)9. 6 kg was dissolved and mixed well while adding 4.79 g of the above sulfuric acid aqueous solution of titanyl sulfate. While maintaining the temperature at 30°C and stirring well, ammonia water was gradually added dropwise to the mixture until the pH reached 8, and the mixture was left as it was for 15 hours.

The gel thus obtained was filtered, washed with water, and heated at 2009C for 10
The mixture was dried for an hour, then calcined at 650° C. for 3 hours in an air atmosphere, and further pulverized to obtain a powder. The composition of the obtained powder was TiO2:Ce02=4:6 (molar ratio) [23
, 6:76.4 (weight ratio), and the specific surface area is BE
According to the T method, it was 50rT11/g.

4 kg of the above powder, 1.4 kg of water, and 120 g of starch were added, mixed, and kneaded well with a kneader. After kneading while adding an appropriate amount of water, the hole diameter (equivalent diameter of the through hole) is 4 m.
m, extrusion molded into a honeycomb mold with a cell wall thickness of 0.7 mm and an aperture ratio of 72%, dried at 120°C for 6 hours, and then fired at 500°C for 6 hours.

The molded body thus obtained is impregnated with an aqueous solution of chloroplatinic acid,
Then, after drying at 120°C for 6 hours, it was fired at 400°C for 6 hours. The PT loading rate of the obtained completed catalyst was 0.4% by weight. In addition, the composition is Ti(h:CeO2:Pt
=23. 5:76, 1:0.4 (weight ratio).

Example 2 A powder made of dry titanium oxide was obtained according to the method described in Example 1, except that cerous nitrate was not used and calcination was not performed. The moisture content of the obtained powder was 5% by weight. 4.4 kg of cerous nitrate dissolved in 10Ω of water was added to 3.4 kg of this powder, dried at 80°C for 12 hours, then at 120°C for 6 hours, and then fired at 500°C for 5 hours in an air atmosphere. It was further crushed to obtain a powder. The composition of the obtained powder is TiO2:Ce02=8:2
(molar ratio) [64.9+35.1 (weight ratio)], and the specific surface area was 90 rrr/g according to the BET method.

4 kg of the above powder, 1.5 cg of water, and 40 g of starch were added, mixed, and kneaded well with a kneader. This has a diameter of 5
Extrusion molded into cylindrical pellets with a length of 6 mm and a length of 12 mm.
After drying at 0°C for 6 hours, it was fired at 700°C for 3 hours.

Next, a catalyst with a Ru loading rate of 1.5% by weight was obtained in accordance with the method described in Example 1, except that a ruthenium nitrate aqueous solution was used instead of a chloroplatinic acid aqueous solution. In addition, the composition is TiO
2:CeO2:Ru =64. O: 34°5:1
．． 5 (weight ratio).

Example 3 Commercially available anatase titanium oxide powder (BET specific surface area 70
ba/g)3. 2.4 kg of cerous nitrate dissolved in 5 p of water was added to 9 kg, and the mixture was heated at 80°C for 12 hours.
After drying at 0° C. for 6 hours, the mixture was ground and mixed in a ball mill for 4 hours. This was baked at 700°C for 3 hours in an air atmosphere,
It was further crushed to obtain a powder. The composition of the obtained powder is Tl
O2:Ce02=9:1 (molar ratio) [80,7
:19. 3 (weight ratio)], and the specific surface area is BET
According to the law, it was 40rrl'/g.

Next, according to the method described in Example 1, a honeycomb shape with a hole diameter (equivalent diameter of the through hole) of 6 mm, a cell thickness of 1 mm, and an aperture ratio of 73% was prepared, with a Pt loading rate of 0. A catalyst containing 6% of teeth was obtained. Also, the composition is TiO2:CeO2:Pt = 80°2:1
The weight ratio was 9.2:0.6.

Example 4 Using each of the catalysts obtained in Examples 1 to 3, wastewater was treated by a wet oxidation method in the following manner. A stainless steel reaction tube is filled with a catalyst, and preheated mixed waste water and air with an oxygen concentration of 21% are continuously introduced from the bottom of the reaction tube for 4000 hours to achieve COD at the entrance and exit portions of the reaction tube.
(Cr) was measured, and the reaction coverage at the initial stage and after 4000 hours of reaction was determined.

Further, the strength of the catalyst was also measured at the initial stage and after 4000 hours of reaction to determine the catalyst strength ratio. In addition, the properties of 14 water (7) used in the treatment are OD (Cr) 20 g/Q,
p) It was 16. The reaction conditions were a reaction temperature of 230°C, a reaction pressure of 50 kg/cJ, and a space velocity of waste water of 1.2 Hr.
' (sky tower standard), space velocity of air 1001-1r-
' (empty column standard, standard condition) was introduced into the reaction tube. The results obtained are shown in Table 1.

Table 1 Comparative Example 1 1.2 kg of water and 40 g of starch were added to 4 kg of commercially available cerium oxide powder, and the mixture was thoroughly kneaded in a mixing kneader.

After extrusion molding and baking at 120'C for 6 hours,
It was fired at 700° C. for 3 hours to obtain cylindrical pellets with a diameter of 5 mm and a length of 6 mm. Using this, a catalyst with a PT loading rate of 0.6% by weight was obtained according to the method described in Example 1.

When this catalyst was reacted under the conditions of Example 4, the COD removal rate was 99% initially, but as time passed, the catalyst strength decreased and the catalyst became powder, and the treatment efficiency also decreased. After 400 hours, the number of catalyst teeth itself decreased, making it difficult to continue the reaction.

Example 5 In Example 3, a mixed gas consisting of 18% oxygen concentration and 1% ozone concentration was used instead of air with an oxygen concentration of 21%, and using the catalyst obtained in Example 1, the reaction temperature was 200%.
The wastewater treatment was carried out for 500 hours at a temperature of 45 kg/ca and the COD removal rate was 97%.

Example 6 In Example 5, 3% hydrogen peroxide solution was added at a space velocity of 0 and 0.
The wastewater was treated for 500 hours using the catalyst obtained in Example 1, which was supplied together with a mixed gas at a rate of 5 Hr' (empty column basis), and as a result, the COD removal rate was 98%.

Example 7 Lanthanum nitrate (La (NO3) 3 .8L O)
TiO2: according to the method described in Example 1, except using 702 g and a 3.8 Ω sulfuric acid solution of titanyl sulfate.
La2O3=78. 3:21. A powder having a composition of 7 (weight ratio) was obtained. This powder was made into pellets having the same shape as in Example 2, and then rhodium was impregnated and supported. The composition of the obtained catalyst is TiO2:La203:Rh=77
, 3:21. 5:1. 2 (weight ratio).

Example 8 Titanium tetrachloride (TiCp4> 1.95k) in water 40Ω
g was dissolved while removing heat. Add neodymium oxide (
80 g of fine powder of Nd203) was dispersed, and aqueous ammonia was gradually added dropwise without stirring until the pH reached 9. After standing for 15 hours, the resulting gel was filtered, washed with water,
It was dried at 180°C for 5 hours and then fired at 800°C for 2 hours in an air atmosphere. The composition of the powder obtained by pulverization is T
iO2:Nd2O3=91.9 (weight ratio), and the specific surface area was 8 rrr/g according to the BET method. The composition was TiO2:Nd2O3:Mn02=82:
Pellet catalysts having the same shape and having a weight ratio of 8:10 were obtained.

Comparative Example 2 Commercially available titanium oxide powder (BET specific surface area 140rrII
/g) according to Example 8 except that the composition was TiO
2:Mn02=90:10 (weight ratio) pellet catalysts having the same shape were obtained.

Example 9 Using each of the catalysts obtained in Examples and Comparative Examples, wastewater treatment was carried out by a wet oxidation method in the following manner. A catalyst IU (catalyst layer length 2) was placed in a stainless steel reaction tube with an inner diameter of 25 mm.
m), and preheated mixed waste water and air with an oxygen concentration of 21% are continuously introduced from the bottom of the reaction tube for 4000 hours, and COD (Cr) is measured at the inlet and outlet of the reaction tube. The removal rates at the initial stage and after 4000 hours of reaction were determined. Further, the strength of the catalyst was also measured at the initial stage and after 4000 hours of reaction to determine the catalyst strength ratio. The composition of the wastewater used for treatment was 12.000 ppm of acetic acid and 1.000 ppm of ammonia.
It was pm. The reaction conditions were a reaction temperature of 230°C, a reaction pressure of 50 kg/cJ, and a space velocity of waste water of 1. 2hr'
(Based on the sky column) and the space velocity of air was 60 hr' (Based on the sky column, standard state). The results obtained are shown in Table 2.

(Effects of the Invention) The catalyst according to the present invention is characterized in that titanium oxide and lanthanide element oxide are used as catalyst components.

Oxides of lanthanoid elements alone have catalytic activity or have poor moldability, making it difficult to mold them into pellets, nicums, etc. In addition, during long-term use in treatment reactions, the physical strength decreases, which causes catalytic activity.

We have found that the above problems can be solved by a combination of titanium oxide and lanthanide element oxide. These have excellent moldability and physical stability, are less prone to deterioration in catalytic strength and catalytic activity, and can be used for long periods of time.

Furthermore, by closely mixing the titanium compound and the lanthanide compound in advance by coprecipitation, impregnation, ball milling, etc., and then using the calcined powder as the catalyst raw material, the homogeneity of the catalyst is improved, resulting in improved strength and activity. Stability is further improved, which is preferable.

Among these, by using the coprecipitation method, the B E of the powder
T (Brunauer-Emmctt-Tel 1e
r) The specific surface area increases, honeycomb molding, etc. becomes relatively easy, and the range of selection of catalyst shapes suitable for wastewater can be expanded, which is more preferable.

Furthermore, the catalyst of the present invention has high catalytic activity against acetic acid, which is difficult to decompose under wet oxidation conditions and therefore often remains at a high concentration during the treatment of various wastewaters.

Therefore, the catalyst of the present invention not only has a high efficiency in treating acetic acid, but also has an excellent effect in improving the efficiency in treating various kinds of wastewater at low temperatures.

Claims (1)

[Scope of Claims] (1) A first catalyst component made of a titanium oxide, a second catalyst component made of an oxide of a lanthanide element, and manganese, iron, cobalt, nickel, tungsten, copper, silver,
In the presence of a solid catalyst consisting of a third catalyst component containing at least one metal selected from the group consisting of gold, platinum, palladium, rhodium, ruthenium and iridium or a water-insoluble or poorly soluble compound thereof, waste water 3
At least one substance selected from the group consisting of organic substances and inorganic substances in the wastewater is converted to nitrogen, carbon dioxide, and water at a temperature of 70°C or less and under a pressure such that the wastewater maintains a liquid phase. 1.0 to 1.5 of the theoretical amount required for decomposition
A method for treating wastewater comprising wet oxidation of the wastewater with a gas containing double the amount of molecular oxygen. (2) the first catalyst component is 5 to 98% by weight as an oxide;
The second catalyst component is 2 to 95% by weight as an oxide and the third catalyst component is 2 to 95% by weight as an oxide.
The method for treating wastewater according to claim 1, wherein the catalyst component is 0.05 to 25% by weight as a metal or compound. (3) The method for treating wastewater according to claim 1, wherein the second catalyst component is an oxide of at least one element selected from the group consisting of lanthanum, cerium, praseodymium, neodymium, and samarium. (4) The method for treating wastewater according to claim 3, wherein the second catalyst component is an oxide of at least one element selected from the group consisting of lanthanum, cerium, and neodymium. (5) The third catalyst component contains manganese, iron, cobalt, nickel, tungsten, copper and silver in an amount of 0 to 25% by weight as a compound, and platinum, gold, palladium,
The amount of rhodium, ruthenium and iridium used is 0 to 10% by weight as metals (however, the total amount of both is 0.5% by weight).
3. The method for treating wastewater according to claim 2, wherein the amount is 05 to 25% by weight. (6) The first catalyst component is 10 to 96% by weight as an oxide.
3. The wastewater treatment method according to claim 2, wherein the second catalyst component is 4 to 90% by weight as an oxide and the third catalyst component is 0.1 to 9% by weight as a metal or compound. (7) The third catalyst component contains manganese, iron, cobalt, nickel, tungsten, copper, and silver in an amount of 0 to 9% by weight as a compound, and platinum, gold, palladium, rhodium, ruthenium, and iridium. The amount is 0 to 5% by weight as metal (however, the total amount of both is 0.1 to 9% by weight)
7. The method for treating wastewater according to claim 6, wherein the wastewater is % by weight. (8) The first catalyst component is 10 to 84% by weight as an oxide
6. A process according to claim 5, wherein the second catalyst component is 16 to 90% by weight in the form of an oxide and the third catalyst component is 0.1 to 9% by weight in the form of a metal or compound. (9) The catalyst according to claim 1, wherein the catalyst is obtained by intimately mixing the first catalyst component and the second catalyst component in advance, and adding the third catalyst component to the calcined mixture. Wastewater treatment methods. (10) The catalyst is obtained by mixing the first catalyst component and the second catalyst component in advance by a coprecipitation method, and adding the third catalyst component to the calcined mixture. wastewater treatment methods. (11) The method for treating wastewater according to claim 1, wherein the catalyst is a granular material. (12) The method for treating wastewater according to claim 1, wherein the catalyst is an integral structure. (13) Claim 1 wherein the catalyst is a honeycomb type catalyst having a shape in which the equivalent diameter of the through holes is 2 to 20 mm, the cell wall thickness is 0.5 to 3 mm, and the aperture ratio is within the range of 50 to 80%.
2. The wastewater treatment method described in 2. (14) The method for treating wastewater according to claim 1, wherein the reaction temperature is within the range of 100 to 370°C. (15) The waste water according to claim 1, wherein at least one selected from the group consisting of ozone and hydrogen peroxide is allowed to coexist when the waste water is passed through the catalyst layer together with a molecular oxygen-containing gas. Processing method. (16) The amount of ozone used is equal to or less than the theoretical amount of oxygen necessary to decompose at least one substance selected from the group consisting of organic substances and inorganic substances in wastewater into nitrogen, carbon dioxide gas, and water. Claim 15: .001 to 1.2 times the molar amount
The wastewater treatment method described in . (17) The amount of hydrogen peroxide used is the theoretical amount of oxygen necessary to decompose at least one substance selected from the group consisting of organic substances and inorganic substances in wastewater into nitrogen, carbon dioxide gas, and water. The wastewater treatment method according to claim 15, wherein the amount is 0.001 to 1.8 times mole.