JP2016067977A - Catalyst for waste water treatment, and method for treating waste water by using the catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst for waste water treatment, which has more excellent durability and allows treatment efficiency of waste water to be improved much more.SOLUTION: The catalyst for waste water treatment, which is used for treating waste water, contains: a catalytic base material containing a titanium-containing compound (A); and a catalytically active component (B) containing a single unit or a compound of each of one or more elements selected from the group consisting of gold, platinum, palladium, iridium and ruthenium and has an X/Y ratio within a range of 0.50-1.70 when the height of the maximum peak existing between 2θ=24°-33° of the catalyst, when a powder X-ray diffraction method is applied to the catalyst, is defined as X and that of the peak, which: exists between 2θ=24°-27° of a reference sample prepared by crushing/mixing 20 mass% of pure anatase type titanium oxide with 80 mass% of pure rutile type titanium oxide; and shows an anatase crystal, is defined as Y.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a wastewater treatment catalyst and a wastewater treatment method using the same.

  Conventionally, biological treatment, combustion treatment, Timmermann method and the like are known as wastewater treatment methods.

  As biological treatment, anaerobic treatment such as activated sludge method and biofilm method, anaerobic treatment such as methane fermentation method, and combined treatment of aerobic treatment and anaerobic treatment are conventionally used. In particular, aerobic treatment using microorganisms is widely adopted as a method for treating wastewater, but aerobic microorganism treatment is complicated by bacteria, algae, protozoa, etc., and high concentrations of organic matter and nitrogen compounds When wastewater containing such substances is subjected to aerobic microorganism treatment, it is necessary to dilute wastewater and adjust pH in order to make the environment suitable for the growth of microorganisms. Since sludge is generated, surplus sludge must be further processed, which has a problem that the processing cost becomes high as a whole.

  Combustion treatment is costly, such as fuel costs, and thus has a problem that treatment costs become extremely high when a large amount of wastewater is treated. In addition, there is a risk of secondary pollution caused by exhaust gas from combustion.

  The Chimmermann method treats wastewater in the presence of an oxygen-containing gas under high temperature and pressure, but generally has low treatment efficiency and requires a secondary treatment facility.

  Particularly in recent years, the pollutants contained in the wastewater to be treated are diverse, and a high level of treated water quality is required. Therefore, the conventional technology as described above cannot sufficiently cope with it.

  Accordingly, various wastewater treatment methods have been proposed for the purpose of obtaining a high level of wastewater treatment efficiency and a high level of treated water. For example, a wet oxidation method using a solid catalyst (hereinafter abbreviated as “catalyst wet oxidation method”) is attracting attention because it can obtain a high level of treated water and has excellent economic efficiency. . Various catalysts have been proposed in order to improve the processing efficiency and processing capacity of such a catalytic wet oxidation method. For example, Patent Document 1 proposes a catalyst in which a noble metal such as palladium or platinum is supported on a carrier such as alumina, silica alumina, silica gel, activated carbon or the like.

  However, in general, the components contained in wastewater are not single, and in many cases contain nitrogen compounds, sulfur compounds, organic halogen compounds, etc. in addition to organic substances, and treatment of wastewater containing such various pollutants. Even if the above catalyst was used, these components could not be sufficiently treated.

  As a catalyst that can solve such problems, Patent Document 2 proposes a catalyst having high durability and excellent catalytic activity.

Conventionally, it is known that the BET specific surface area of the carrier for the wastewater treatment catalyst (or the catalyst itself) is preferably in the range of 20 to 70 m ² / g as described in Patent Document 3 and the like.

JP 49-44556 A Japanese Patent Laid-Open No. 5-138027 International Publication No. 2008/120588 Pamphlet

  As a result of investigations by the present inventors, it was found that the wastewater treatment catalysts disclosed in Patent Documents 1 to 3 still have insufficient catalyst durability and wastewater treatment efficiency.

  Therefore, an object of the present invention is to provide a wastewater treatment catalyst having superior durability and further improved wastewater treatment efficiency.

  The present inventors have intensively studied to solve the above problems. As a result, the inventors have found that the above problem can be solved by controlling the crystal structure of a wastewater treatment catalyst containing a catalyst base material containing a predetermined material and a catalytically active component, and has completed the present invention.

  That is, according to one aspect of the present invention, a wastewater treatment catalyst used for wastewater treatment, a catalyst base material containing a titanium-containing compound (A), and a group consisting of gold, platinum, palladium, iridium, and ruthenium. There is provided a catalyst containing a catalytically active component (B) containing a single element or a compound of one or more elements selected from In the catalyst, the maximum peak height existing between 2θ = 24 ° to 33 ° in the powder X-ray diffraction method is X, and 20% by mass of pure anatase-type titanium dioxide and pure rutile-type titanium dioxide 80 are used. The value of the ratio of X / Y is 0.50, where Y is the height of a peak showing anatase crystals existing between 2θ = 24 ° and 27 ° of a reference sample obtained by pulverization and mixing with mass%. It is characterized by being in the range of ˜1.70.

  The wastewater treatment catalyst according to the present invention has high mechanical strength (particularly excellent wear resistance), and can maintain excellent activity and durability for a long period of time, particularly in wet oxidation treatment of wastewater. For this reason, when the wastewater is treated (preferably, wet oxidation treatment) using the catalyst of the present invention, treated water purified to a high level can be obtained.

It is the schematic which shows one embodiment of the processing apparatus of the waste_water | drain at the time of employ | adopting wet oxidation treatment as one of the oxidation treatment processes.

  Hereinafter, specific embodiments for carrying out the present invention will be described in detail with reference to the drawings. The technical scope of the present invention should be determined based on the description of the claims, and It is not limited only to the form.

  According to one aspect of the present invention, a wastewater treatment catalyst used for wastewater treatment, which is selected from the group consisting of a catalyst base material containing a titanium-containing compound (A) and gold, platinum, palladium, iridium, and ruthenium. And a catalytically active component (B) containing a single element or a compound of two or more elements, and exists between 2θ = 24 ° and 33 ° of the powder X-ray diffraction method for the catalyst. X is the maximum peak height, and exists between 2θ = 24 ° and 27 ° of a reference sample obtained by grinding and mixing 20% by mass of pure anatase titanium dioxide and 80% by mass of pure rutile titanium dioxide. Provided is a wastewater treatment catalyst characterized in that the value of the ratio of X / Y is in the range of 0.50 to 1.70, where Y is the height of the peak showing the anatase crystal. .

[Catalyst substrate]
The wastewater treatment catalyst according to the present invention contains a catalyst base and a catalytically active component. Among these, the catalyst base is also called a carrier and has a function of supporting a catalytically active component. In the present invention, the catalyst base contains the titanium-containing compound (A).

The titanium-containing compound (A) contained in the catalyst base is not particularly limited as long as it has a function as the above-described catalyst base and contains titanium. In a preferred embodiment, the titanium-containing compound (A) is a mixed oxide or composite oxide containing titanium oxide (titania; TiO ₂ ) or titanium oxide. Here, as a composite oxide containing a titanium oxide (TiO ₂ ), from the viewpoint of mechanical strength and durability of the catalyst, for example, TiO ₂ —ZrO ₂ , TiO ₂ —Fe ₂ O ₃ , TiO ₂ —SiO ₂ , TiO ₂ —Al ₂ O _{3 and the} like. Among them, the catalyst base includes a combination of titanium oxide and a composite oxide of titanium and zirconium, a combination of titanium oxide, iron oxide, and a composite oxide of titanium and iron, and titanium. It is particularly preferable that any of these oxides be used. Moreover, it is preferable that a catalyst base material further contains the simple substance or compound (C) of 1 type, or 2 or more types of elements selected from the group consisting of iron, silicon, aluminum, zirconium and cerium. Examples of compounds of these elements include oxides of these elements and composite oxides containing these elements. When the catalyst substrate contains a metal element other than titanium, the content ratio of titanium in the metal element constituting the catalyst substrate is preferably 50% or more, more preferably 60% as a molar ratio. More preferably, it is 70% or more.

The preferred specific surface area of the catalyst substrate is 20 m ² / g or more, more preferably 25 m ² / g or more, and most preferably 30 m ² / g or more. On the other hand, the specific surface area of the catalyst substrate is preferably 70 m ² / g or less, more preferably 60 m ² / g or less, and most preferably 55 m ² / g or less. If the specific surface area of a catalyst is 70 m < ² > / g or less, the decay | disintegration of a catalyst and the fall of activity will be suppressed. In addition, as a measuring method of the “specific surface area of the catalyst substrate”, the BET method for analyzing the adsorption of nitrogen is adopted. The crystal structure of the catalyst substrate is not particularly limited, and may have an anatase type crystal structure, or may have a crystal structure other than the anatase type crystal structure, but has an anatase type crystal structure. The catalyst substrate is preferred.

  The shape of the catalyst substrate is not particularly limited, and may be appropriately selected according to the purpose, for example, pellet shape, granular shape, spherical shape, ring shape, honeycomb shape and the like.

  Although it does not specifically limit about the pore volume of a catalyst base material, Preferably it is 0.20 ml / g or more, More preferably, it is 0.25 ml / g or more. On the other hand, the upper limit value of the pore volume is preferably 0.50 ml / g or less, more preferably 0.45 ml / g or less. When the pore volume of the catalyst base is 0.20 ml / g or more, the catalyst active component described later can be sufficiently supported on the catalyst base, and a sufficient active action can be ensured. On the other hand, if the pore volume of the catalyst substrate is 0.50 ml / g or less, it is possible to suppress a decrease in the durability of the catalyst and a catalyst collapse due to this.

[Catalytic active ingredient]
The wastewater treatment catalyst according to the present invention contains a catalytically active component (B). This catalytically active component contains a single element or a compound of one or more elements selected from the group consisting of gold, platinum, palladium, iridium and ruthenium. Here, the “catalytic active component” is a component having an action (active action) for increasing an oxidation / decomposition reaction rate with respect to an oxide such as an organic compound or a nitrogen compound contained in waste water. In the present invention, at least the above-mentioned noble metal is used as an active ingredient.

  As described above, the catalytically active component includes a carrier or compound (B) of one or more elements selected from the group consisting of gold, platinum, palladium, iridium and ruthenium. Catalysts containing these catalytically active components are preferable because they exhibit particularly excellent active action in the wet oxidation of waste water. Of these, platinum or palladium is preferably used as the catalytically active component.

  When the catalytically active component is used in the form of a compound containing the noble metal, the raw material of the catalytically active component is not particularly limited as long as it contains a noble metal selected from the above, but is preferably a water-soluble compound, more preferably It is an inorganic compound. Moreover, an emulsion type, a slurry, or a colloidal compound may be used, and a compound suitable as appropriate may be used depending on the method for preparing the catalyst and the type of the catalyst substrate.

  For example, when gold is used as a catalytically active component, chloroauric acid, potassium gold cyanide, potassium gold cyanide and the like can be used. In addition, when platinum is used as a catalyst active component, platinum black, platinum oxide, platinum chloride, platinum chloride, platinum chloride, chloroplatinic acid, sodium chloroplatinate, potassium nitrite, dinitrodiammine platinum, hexaammine platinum, hexa Hydroxyplatinic acid, cis-dichlorodiammine platinum, tetraammine platinum dichloride, tetraammine platinum hydroxide, hexaammine platinum hydrochloride, potassium tetrachloroplatinate and the like can be used. When palladium is used as a catalytically active component, palladium chloride, palladium nitrate, dinitrodiammine palladium, dichlorodiammine palladium, tetraammine palladium dichloride, cis-dichlorodiammine palladium, palladium black, palladium oxide, tetraammine palladium hydroxide, etc. are used. be able to. Further, when iridium is used as a catalytic active component, iridium chloride or the like can be used. Further, when ruthenium is used as a catalytic active component, for example, ruthenium chloride, ruthenium nitrate, hexacarbonyl-μ-chlorodichlorodiruthenium, ruthenium oxide, dodecacarbonyltriruthenium, ruthenium acetate, potassium ruthenate, potassium hexachlororuthenate, hexaammine Ruthenium trichloride, potassium tetraoxoruthenate, and the like can be used.

  The compounds to be used are not particularly limited to these, but those skilled in the art can appropriately select from the above compounds and produce the catalyst of the present invention according to, for example, the methods described in Examples.

  In the wastewater treatment catalyst according to the present invention, the catalytically active component (B) is not limited to the above examples, and may further contain other elements and their compounds in any combination. For example, the catalytically active component may further contain an alkali metal, alkaline earth metal, or other transition metal. Na, K and Cs are preferable as the alkali metal, Mg, Ca, Sr and Ba are preferable as the alkaline earth metal, and La, Ce, Pr and Y are preferable as the other transition metals. The addition of these elements is preferable because it contributes to highly dispersed support of the noble metal component.

Examples of the combination of the catalytic active component and the catalyst base include Pt—TiO ₂ , Pd—TiO ₂ , Ru—TiO ₂ , Pt—Pd—TiO ₂ , Pt—Rh—TiO ₂ , Pt—Ir—TiO ₂ , Pt—Au—TiO ₂ , Pt—Ru—TiO ₂ , Pd—Rh—TiO ₂ , Pd—Ir—TiO ₂ , Pd—Au—TiO ₂ , Pd—Ru—TiO ₂ , Pt—TiO ₂ —ZrO ₂ , Pd—TiO ₂ —ZrO ₂ , Ru—TiO ₂ —ZrO ₂ , Pt—Pd—TiO ₂ —ZrO ₂ , Pt—Rh—TiO ₂ —ZrO ₂ , Pt—Ir—TiO ₂ —ZrO ₂ , Pt—Au— _{TiO 2 -ZrO 2, Pt-Ru} -TiO 2 -ZrO 2, Pd-Rh-TiO 2 -ZrO 2, Pd-Ir-TiO 2 -ZrO 2, Pd-Au-TiO 2 -Z _{O 2, Pd-Ru-TiO} 2 -ZrO 2, Pt-Fe 2 O 3 -TiO 2, Pd-Fe 2 O 3 -TiO 2, Ru-Fe 2 O 3 -TiO 2, Pt-Pd-Fe 2 O _{3 -TiO 2, Pt-Ir-} Fe 2 O 3 -TiO 2, Pt-Au-Fe 2 O 3 -TiO 2, Pt-Ru-Fe 2 O 3 -TiO 2, Pd-Rh-Fe 2 O 3 - TiO ₂ , Pd—Ir—Fe ₂ O ₃ —TiO ₂ , Pd—Au—Fe ₂ O ₃ —TiO ₂ , Pd—Ru—Fe ₂ O ₃ —TiO ₂ , Pt—TiO ₂ —SiO ₂ , Pd—TiO _{2 2} —SiO ₂ , Ru—TiO ₂ —SiO ₂ , Pt—Pd—TiO ₂ —SiO ₂ , Pt—Rh—TiO ₂ —SiO ₂ , Pt—Ir—TiO ₂ —SiO ₂ , Pt—Au—TiO ₂ — SiO _{2 Pt-Ru-TiO 2 -SiO 2} , Pd-Rh-TiO 2 -SiO 2, Pd-Ir-TiO 2 -SiO 2, Pd-Au-TiO 2 -SiO 2, Pd-Ru-TiO 2 -SiO 2, Pt—TiO ₂ —Al ₂ O ₃ , Pd—TiO ₂ —Al ₂ O ₃ , Ru—TiO ₂ —Al ₂ O ₃ , Pt—Pd—TiO ₂ —Al ₂ O ₃ , Pt—Rh—TiO ₂ —Al ₂ O ₃ , Pt—Ir—TiO ₂ —Al ₂ O ₃ , Pt—Au—TiO ₂ —Al ₂ O ₃ , Pt—Ru—TiO ₂ —Al ₂ O ₃ , Pd—Rh—TiO ₂ —Al ₂ O ₃ , Pd—Ir—TiO ₂ —Al ₂ O ₃ , Pd—Au—TiO ₂ —Al ₂ O ₃ , Pd—Ru—TiO ₂ —Al ₂ O _{3 and the} like. Here, the notation such as Pt—TiO ₂ means that the composition of Pt and TiO ₂ is contained in the catalyst. In the above combination examples, elements other than the noble metals are generally stable oxides, and the noble metals are merely exemplified metals, and the combination of the catalytically active components of the present invention is not limited thereto. Absent.

  From the viewpoint of efficiently bringing wet pollutants into contact with pollutants in the wastewater and oxygen in the air to promote the wet oxidation reaction, it is recommended that the catalytically active components be highly dispersed in the form of fine particles on the catalyst. Is done. From this viewpoint, the average particle diameter of the catalytically active component contained in the catalyst is preferably 0.5 nm or more, more preferably 0.7 nm or more, and further preferably 1 nm or more. Moreover, the average particle diameter of the catalytically active component contained in the catalyst is preferably 20 nm or less, more preferably 18 nm or less, and further preferably 17 nm or less. When the particle diameter of the catalytically active component is 0.5 nm or more, aggregation of the catalytically active component is suppressed and durability is prevented from being lowered. Moreover, if the particle diameter of a catalytically active component is 20 nm or less, sufficient processing performance can be ensured. As a method for measuring the average particle size of the catalytically active components contained in the catalyst, TPD analysis (temperature programmed desorption method) is employed, and the amount of chemical adsorption is measured and calculated by the CO pulse method. And Further, the individual particle diameter of the catalytically active component can be confirmed by scraping the catalyst surface layer portion and observing it at a magnification of 10 to 1,000,000 times using a transmission electron microscope.

  Although there is no restriction | limiting in particular about content of each component contained in the catalyst for wastewater treatment which concerns on this invention, Content of (A) component is 5-99.9 mass% as an example of preferable content, (B ) Component content is 0.01 to 5% by mass, and component (C) content is 0 to 90% by mass. Under the present circumstances, the sum total of (A) component and (C) component is 95-99.9 mass%. Here, the content of the component (A) and the component (C) is a value converted into the mass of the oxide, and the content of the component (B) is a value converted into a single metal.

  In the wastewater treatment catalyst according to the present invention, the height of the maximum peak existing between 2θ = 24 ° and 33 ° in the powder X-ray diffraction method for the catalyst is X, and 20% by mass of pure anatase titanium dioxide And X / Y, where Y is the height of a peak showing anatase crystals existing between 2θ = 24 ° and 27 ° of a reference sample obtained by grinding and mixing 80% by mass of pure rutile titanium dioxide The ratio is in the range of 0.50 to 1.70.

  Here, the “reference sample” used for measurement by the powder X-ray diffraction method of the wastewater treatment catalyst according to the present invention is 20% by mass of pure anatase-type titanium dioxide (manufactured by Kanto Chemical Co., Ltd., reagent deer grade 1). And pure rutile-type titanium dioxide (manufactured by Kanto Chemical Co., Ltd., reagent special grade) 80% by mass. Specifically, for example, anatase-type titanium dioxide (reagent deer grade 1) manufactured by Kanto Chemical Co., Ltd. 0 .80 g and 3.20 g of rutile titanium dioxide (reagent special grade) manufactured by Kanto Chemical Co., Ltd. are ground and mixed in an agate mortar. And the height (X) of the maximum peak existing between 2θ = 24 ° to 33 ° of the wastewater treatment catalyst according to the present invention, and the anatase existing between 2θ = 24 ° to 27 ° of the reference sample Both the height (Y) of the peak indicating the crystal can be measured, for example, by a powder X-ray diffraction method under the following conditions. Measurement of X and Y in Examples described later was also performed using a powder X-ray diffraction method under the following conditions.

Model PHILIPS X'Pert Pro
X-ray source CuKα / 45kV / 40mA
Detector High-speed semiconductor detector Light-receiving side filter Ni filter Monochromator Curved crystal monochromator Divergence slit 1 °
Scattering slit 1 °
Light receiving slit 0.5mm
Step 0.017 °
Measurement time 5 seconds / step.

  As described above, in the wastewater treatment catalyst according to the present invention, it is essential that the value of the ratio of X / Y is in the range of 0.50 to 1.70, and the value of X / Y is preferably It is 0.60 to 1.50, more preferably 0.70 to 1.20, and particularly preferably 0.70 to 0.80.

Conventionally, for a wastewater treatment catalyst using a catalyst agent such as a TiO ₂ —ZrO ₂ system (TZ system), the value of the BET specific surface area of the catalyst and the catalyst base material evaluates the mechanical strength and durability of the catalyst. Was known as one of the indicators for. For example, when the catalyst (catalyst base material) has a BET specific surface area of about 40 m ² / g, a wastewater treatment catalyst having excellent mechanical strength and durability has been obtained. However, according to the study by the present inventors, it has been found that even if the catalyst (catalyst substrate) has such a BET specific surface area, sufficient mechanical strength and durability may not be achieved. . Then, it was studied in detail the causes, and the site catalysts (in particular, catalyst base) showing the inside there is a bias in the specific surface area, for example 100 m 2 / ^g or more BET specific surface area of, 30 m ² It has been found that sufficient mechanical strength and durability cannot be achieved in the case where a portion having a BET specific surface area of not more than / g is mixed. On the other hand, even in such a case, if the catalyst (catalyst base material) as a whole is evaluated, the value of the BET specific surface area becomes a value in a range that has been considered to be preferable in the past (eg, about 40 m ² / g). Thus, the performance of the catalyst could not be accurately predicted using the BET specific surface area as an index.

  As a result of further investigation by the present inventors, when a portion having a large specific surface area and a portion having a small specific surface area coexist, sufficient mechanical strength and durability of the catalyst cannot be achieved. It was found that this was caused by insufficient conversion. Based on this finding, a catalyst having a certain maximum peak height between 2θ = 24 ° and 33 ° with respect to the peak height (Y) showing the anatase crystal in the reference sample as described above. It is found that a catalyst in which mixing of a portion having a large specific surface area (a portion where crystallization is insufficient) that causes a decrease in mechanical strength and durability can be obtained can be obtained. After confirming that the strength and durability were sufficiently excellent, the present invention was completed.

  The size of the catalyst is not particularly limited. For example, when the catalyst is granular (hereinafter, also referred to as “granular catalyst”), the average particle diameter is preferably 1 mm or more, and more preferably 2 mm or more. When the average particle diameter is 1 mm or more, an increase in pressure loss when the granular catalyst is packed in the reaction tower is prevented, and the possibility that the catalyst layer is clogged by the suspension contained in the waste water is reduced. Moreover, it is preferable that the average particle diameter of a granular catalyst is 10 mm or less, More preferably, it is 7 mm or less. If the average particle diameter is 10 mm or less, a sufficient geometric surface area can be secured for the granular catalyst, and the possibility of a decrease in contact efficiency with the water to be treated and a reduction in treatment capacity associated therewith is reduced.

  Further, for example, when the catalyst is in a pellet form (hereinafter also referred to as “pellet catalyst”), the average diameter is preferably 1 mm or more, more preferably 2 mm or more, and preferably 10 mm or less, more preferably. Is 6 mm or less. The length of the pellet-like catalyst in the longitudinal direction is preferably 2 mm or more, more preferably 3 mm or more, preferably 15 mm or less, more preferably 10 mm or less. If the average diameter of the pellet-shaped catalyst is 1 mm or more, or the length in the longitudinal direction is 2 mm or more, an increase in pressure loss when the pellet-shaped catalyst is packed in the reaction tower is prevented, and the catalyst layer is contained in the waste water. The risk of being clogged with turbidity is reduced. Further, if the average diameter of the pellet-shaped catalyst is 10 mm or less or the length in the longitudinal direction is 15 mm or less, a sufficient geometric surface area can be secured for the pellet-shaped catalyst, and the contact efficiency with the water to be treated can be improved. The possibility of a decrease and a decrease in processing capacity accompanying this is reduced.

  Further, when the catalyst is in a honeycomb shape (hereinafter also referred to as “honeycomb catalyst”), the equivalent diameter of the through hole is preferably 1.5 mm or more, more preferably 2.5 mm or more, preferably 10 mm. Or less, more preferably 6 mm or less. Moreover, it is preferable that the wall thickness between adjacent through-holes is 0.1 mm or more, More preferably, it is 0.5 mm or more, Preferably it is 3 mm or less, More preferably, it is 2.5 mm or less. Furthermore, the porosity of the catalyst surface is preferably 50% or more with respect to the total surface area, more preferably 55% or more, preferably 90% or less, and more preferably 85% or less. If the equivalent diameter of the honeycomb catalyst is 1.5 mm or more, the risk of an increase in pressure loss when the reaction tower is packed is reduced. In addition, when the equivalent diameter of the honeycomb catalyst is 10 mm or less, the contact ratio with the liquid to be treated can be sufficiently ensured, and the catalyst activity can be sufficiently maintained. Further, if the thickness between the through holes of the honeycomb-shaped catalyst is 0.1 mm or more, the mechanical strength of the catalyst can be ensured. On the other hand, if the thickness between the through holes of the honeycomb-shaped catalyst is 3 mm or less, an increase in cost associated with an increase in the amount of catalyst raw material used can be prevented.

  In the case of a honeycomb-shaped catalyst, it is the same as a so-called monolithic carrier, and is manufactured by an extrusion molding method or a method of winding a sheet-like element. The shape of the gas passage port (cell shape) may be hexagonal, quadrangular, triangular or corrugated. The cell density (number of cells / unit cross-sectional area) can be appropriately selected by those skilled in the art.

  In addition, when the above-mentioned catalyst is filled in the reaction tower and the waste water containing the suspension is subjected to wet oxidation treatment, the catalyst layer may be clogged due to precipitation of solid matter or suspension in the waste water. Among these catalysts, it is recommended to use a honeycomb catalyst.

  The method for producing the wastewater treatment catalyst according to the present invention is not particularly limited, and can be produced by a conventionally known method. Examples of the method for supporting the catalytically active component on the catalyst base include a kneading method, an impregnation method, an adsorption method, a spray method, and an ion exchange method.

  Here, as an example of a method for controlling the wastewater treatment catalyst so as to have the above-described X / Y value, the firing process for obtaining the catalyst base is performed in two or more stages, and the firing temperature in the subsequent firing process is further increased. The method of making it high is mentioned.

  That is, the method for producing a wastewater treatment catalyst provided by the present invention includes, for example, a step of preparing a catalyst precursor (usually in the form of a gel or powder) and a step of firing the precursor. And the firing includes a first firing step and a second firing step performed at a firing temperature higher than that of the first firing step. A catalyst base material is obtained by the step of firing the precursor. In this way, the catalyst precursor is obtained by performing heat treatment at a lower temperature in the first-stage firing step and proceeding with the final firing in the second-stage firing step after the precursor has been crystallized to some extent. The body is crystallized uniformly, and a desired catalyst substrate can be obtained.

  At this time, the specific value of the firing temperature in the firing step is not particularly limited, and the firing temperature in the second firing step (second firing temperature) is more than the firing temperature in the first firing step (first firing temperature). As an example, when the firing process is performed in two stages, the first firing temperature is preferably 300 to 700 ° C, more preferably 400 to 600 ° C. The second baking temperature is preferably 500 to 800 ° C, more preferably 550 to 750 ° C. In this case, the firing time in the first firing step (the total of the temperature raising time from room temperature to the first firing temperature and the firing time at the first firing temperature) is preferably 3 to 20 hours, more preferably Is 5 to 15 hours. The firing time in the second firing step (the total of the temperature raising time from the first firing temperature to the second firing temperature and the firing time at the second firing temperature) is preferably 3 to 20 hours, more preferably Is 5 to 15 hours.

  In the conventional technique, when a catalyst precursor is calcined to obtain a catalyst base material, one-step calcining is performed in which the temperature is raised at a constant rate to the target calcining temperature and held at the target temperature for a certain time. . According to the study by the present inventors, in this method, as long as firing is performed in one stage, the above-described wastewater treatment catalyst having the value of X / Y can be obtained no matter how the rate of temperature rise is controlled. It turns out not. More specifically, when the heating rate is increased, crystallization of the catalyst base can be advanced, but a specific surface area cannot be sufficiently ensured. On the other hand, when the rate of temperature increase was slowed, it was found that even though the desired specific surface area could be secured, a site with insufficient crystallization would occur due to the influence of temperature distribution in the firing furnace. .

  On the other hand, a catalyst for wastewater treatment is obtained by adopting the above-described two or more steps of firing, firing the catalyst precursor, and using the obtained fired product as a catalyst base to carry a catalytically active component thereon. Thus, it was found that the crystallization of the catalyst substrate can be progressed uniformly while ensuring a desired specific surface area.

  In addition, about the concrete method for making a catalyst base material carry | support a catalyst active component and obtaining a catalyst for wastewater treatment, it is possible to manufacture a wastewater treatment catalyst by adopting various conventionally known conditions as appropriate. It is.

  Hereinafter, an embodiment in which wastewater is treated using the wastewater treatment catalyst according to the present invention will be described by way of an example in which wastewater is treated by wet oxidation treatment.

  About the kind of the wastewater treated by the wet oxidation treatment using the wastewater treatment catalyst according to the present invention, the wastewater containing any one or more of an organic compound, a nitrogen compound, and a sulfur compound can be effectively treated. Although it can, it is not limited to these. Such wastewater includes wastewater discharged from various industrial plants such as chemical plants, electronic component manufacturing equipment, food processing equipment, metal processing equipment, metal plating equipment, printing plate making equipment, photographic equipment, thermal power generation and nuclear power generation. Wastewater discharged from power generation facilities such as EOG, specifically wastewater discharged from EOG manufacturing facilities, alcohol manufacturing facilities such as methanol, ethanol, and higher alcohols, especially acrylic acid, acrylic ester, methacrylic acid, methacrylic ester Examples include aliphatic carboxylic acids such as aliphatic carboxylic acids and their esters, or aromatic carboxylic acids such as terephthalic acid and terephthalic acid esters, or organic matter-containing wastewater discharged from the production process of aromatic carboxylic acid esters. Also, waste water containing nitrogen compounds such as amine, imine, ammonia, hydrazine may be used. It may also be wastewater containing sulfur compounds discharged from factories in various industrial fields such as paper / pulp, fiber, steel, ethylene / BTX, coal gasification, meat and chemicals. Examples of the sulfur compound herein include inorganic sulfur compounds such as hydrogen sulfide, sodium sulfide, potassium sulfide, sodium hydrosulfide, thiosulfate and sulfite, and organic sulfur compounds such as mercaptans and sulfonic acids. Further, for example, domestic wastewater such as sewage and human waste may be used. Alternatively, it may be wastewater containing organic halogen compounds such as dioxane, dioxins and chlorofluorocarbons, diethylhexyl phthalate, and nonylphenol, and harmful substances such as environmental hormone compounds.

  The “waste water” in the present invention is not limited to so-called industrial waste water discharged from the industrial plant as described above, and in short, includes any one or more of organic compounds, nitrogen compounds, and sulfur compounds. Any liquid is included, and the source (source) of such liquid is not particularly limited.

  Further, the wastewater treatment catalyst according to the present invention is suitably used for wet oxidation treatment of wastewater, and in particular, used for catalytic wet oxidation treatment under pressure that heats wastewater and maintains the liquid phase of the wastewater. It is recommended.

  Hereinafter, a method for treating waste water using the treatment apparatus shown in FIG. 1 will be described. FIG. 1 is a schematic view showing an embodiment of a wastewater treatment apparatus when wet oxidation is employed as one of the oxidation treatment steps, but the apparatus used in the present invention is not limited to this.

  The wastewater supplied from the wastewater supply source is supplied to the wastewater supply pump 5 through the wastewater supply line 6 and further sent to the heater 3. The space velocity at this time is not particularly limited, and may be appropriately determined depending on the treatment capacity of the catalyst.

  When the wastewater treatment catalyst according to the present invention is used, the wet oxidation treatment can be performed in the presence or absence of an oxygen-containing gas, but is included in the wastewater when the oxygen concentration in the wastewater is increased. Therefore, it is preferable to mix an oxygen-containing gas into the waste water because the oxidation / decomposition efficiency of the oxide to be oxidized can be improved.

  When the wet oxidation treatment is performed in the presence of the oxygen-containing gas, for example, the oxygen-containing gas is introduced from the oxygen-containing gas supply line 8, the pressure is increased by the compressor 7, and the wastewater is discharged before being supplied to the heater 3. It is preferable to mix in. In the present invention, the “oxygen-containing gas” is a gas containing molecular oxygen and / or ozone, and if it is such a gas, pure oxygen, oxygen-enriched gas, air, hydrogen peroxide water, other plants The oxygen-containing gas produced in step 1 may be used, and the type of the oxygen-containing gas is not particularly limited, but it is recommended to use air among these from an economic viewpoint.

  The supply amount in the case of supplying the oxygen-containing gas to the wastewater is not particularly limited, and an amount effective for enhancing the ability to oxidize and decompose the oxide in the wastewater may be supplied. The supply amount of the oxygen-containing gas can be appropriately adjusted, for example, by providing the oxygen-containing gas flow rate adjusting valve 9 on the oxygen-containing gas supply line 8. A preferable supply amount of the oxygen-containing gas is 0.5 times or more, more preferably 0.7 times or more, preferably 5.0 times or less, more preferably 3 times or more the theoretical oxygen demand of the oxide in the waste water. It is recommended to make it 0 times or less.

  In the present invention, “theoretical oxygen demand” means the amount of oxygen necessary for oxidizing and / or decomposing oxides such as organic compounds and nitrogen compounds in waste water to nitrogen, carbon dioxide, water, and ash. In the present invention, the theoretical oxygen demand is indicated by the chemical oxygen demand (COD (Cr))).

  The waste water sent to the heater 3 is preheated and then supplied to the reaction tower 1 equipped with the electric heater 2. If the temperature of the wastewater is too high, the wastewater will be in a gas state in the reaction tower, so that organic substances may adhere to the catalyst surface and the activity of the catalyst may deteriorate. Therefore, it is recommended to apply pressure in the reaction tower so that the wastewater can maintain a liquid phase even at high temperatures. Although it is influenced by other conditions, when the temperature of the waste water exceeds 370 ° C. in the reaction tower, a high pressure must be applied to maintain the liquid phase state of the waste water. Since the equipment may increase in size and the running cost may increase, the temperature of the waste water in the reaction tower is more preferably 270 ° C. or less, further preferably 230 ° C. or less, and still more preferably 170 ° C. or less. It is. On the other hand, if the temperature of the wastewater is less than 80 ° C, it may be difficult to efficiently oxidize and decompose the oxide in the wastewater, so the temperature of the wastewater in the reaction tower is preferably 80 ° C or higher. More preferably, it is 100 degreeC or more, More preferably, it is 110 degreeC or more.

  In addition, the timing which heats waste_water | drain is not specifically limited, As above-mentioned, wastewater heated previously may be supplied in a reaction tower, or you may heat, after supplying waste_water | drain in a reaction tower. Also, the heating method of the waste water is not particularly limited, and a heater or a heat exchanger may be used, or the waste water may be heated by installing a heater in the reaction tower. Further, a heat source such as steam may be supplied to the waste water.

  Moreover, it is preferable to provide a pressure regulating valve on the exhaust gas outlet side of the wet oxidation treatment apparatus, and adjust the pressure appropriately according to the treatment temperature so that the wastewater can maintain the liquid phase in the reaction tower. For example, when the treatment temperature is 80 ° C. or more and less than 95 ° C., the waste water is in a liquid phase even under atmospheric pressure, and may be under atmospheric pressure from the viewpoint of economy, but in order to improve the treatment efficiency It is preferable to apply pressure. Further, when the treatment temperature is 95 ° C. or higher, the waste water is often vaporized under atmospheric pressure. When the treatment temperature is 95 ° C. or higher and lower than 170 ° C., the pressure and the processing temperature are about 0.2 to 1 MPa (Gauge). When the pressure is 170 ° C. or higher and lower than 230 ° C., a pressure of about 1 to 5 MPa (Gauge) is applied, and when the processing temperature is 230 ° C. or higher, a pressure of 5 MPa (Gauge) or higher is applied so that the drainage can maintain the liquid phase. It is preferable to control the pressure.

  In the wet oxidation treatment used in the present invention, the number, type, shape, etc. of the reaction tower are not particularly limited, and a single reaction tower or a combination of a plurality of reaction towers used in a normal wet oxidation treatment can be used. For example, a single-tube reaction tower or a multi-tube reaction tower can be used. Moreover, when installing several reaction towers, it can be set as arbitrary arrangements, such as making a reaction tower in series or parallel according to the objective.

  Various methods such as gas-liquid upward co-current, gas-liquid downward co-current, and gas-liquid counter-current can be used as a method for supplying wastewater to the reaction tower. Two or more supply methods may be combined.

  When the above-described catalyst is used for the wet oxidation treatment in the reaction tower, the oxidation / decomposition treatment efficiency of the oxide such as one or more of organic compounds, nitrogen compounds, and sulfur compounds contained in the wastewater is improved. At the same time, excellent catalytic activity and catalyst durability can be maintained for a long time, and wastewater can be obtained as treated water purified to a high level.

The amount of the catalyst packed in the reaction tower is not particularly limited, and can be appropriately determined according to the purpose. Typically, the catalyst to ^{0.1hr -1 ~10hr} -1 at a space velocity per catalyst layer, more preferably a ^{0.2hr -1 ~5hr} -1, more preferably ^{0.3hr -1 ~3hr} -1 It is recommended to adjust the filling amount. If the space velocity is 0.1 hr ⁻¹ or more, it is possible to ensure the amount of the catalyst to be treated and avoid an increase in the size of the equipment. Further, if the space velocity is 10 hr ⁻¹ or less, the waste water can be sufficiently oxidized and decomposed in the reaction tower.

  When using a plurality of reaction towers, different catalysts may be used for each, or a reaction tower filled with a catalyst and a reaction tower not using a catalyst may be combined. It is not limited. The shape of the catalyst to be filled is not particularly limited, but a honeycomb catalyst or a pellet catalyst is preferably used. In addition, various packings, internal crops, and the like may be incorporated in the reaction tower for the purpose of stirring gas and liquid, improving contact efficiency, and reducing gas-liquid drift.

  Oxides in wastewater are oxidized and decomposed in the reaction tower. In the present invention, “oxidation / decomposition treatment” means oxidative decomposition treatment in which acetic acid is converted into carbon dioxide and water, and acetic acid is converted into carbon dioxide and methane. Decarboxylation, sulfidation, hydrosulfide, oxidation of sulfite, thiosulfate to sulfate, oxidation and oxidative decomposition of dimethyl sulfoxide to ash such as carbon dioxide, water, sulfate ion, urea Examples include hydrolysis treatment to convert ammonia and carbon dioxide, oxidative decomposition treatment to convert ammonia or hydrazine to nitrogen gas and water, oxidation treatment to convert dimethyl sulfoxide to dimethyl sulfone or methane sulfonic acid, etc. Treatment to decompose nitrogen gas, carbon dioxide, water, ash, etc., decomposition treatment to reduce the molecular weight of refractory organic compounds and nitrogen compounds, or oxidation That oxidation treatment is meant to include various oxide and / or degradation such.

  In addition, in the treatment liquid obtained through the wet oxidation treatment, the organic compounds that are hardly decomposable among the oxides often remain after being reduced in molecular weight. Low molecular weight organic acids, especially acetic acid, often remain.

  FIG. 1 shows a specific example of the treatment. The waste water was oxidized and decomposed in the reaction tower, then taken out from the treatment liquid line 10 as a treatment liquid, and appropriately cooled by the cooler 4 as needed. Then, it is separated into gas and liquid by the gas-liquid separator 11. At that time, it is preferable to detect the liquid level using the liquid level controller LC and control the liquid level in the gas-liquid separator to be constant by the liquid level control valve 13. Further, it is preferable to detect the pressure state using the pressure controller PC and control the pressure in the gas-liquid separator to be constant by the pressure control valve 12.

  Alternatively, after the wastewater is oxidized and decomposed, the treatment liquid is cooled to some extent by the cooler without being cooled, and then discharged through the pressure control valve, and then separated into gas and liquid by the gas-liquid separator. May be.

  Here, the temperature in the gas-liquid separator is not particularly limited, but carbon dioxide is contained in the treatment liquid obtained by oxidizing and decomposing waste water in the reaction tower. Release carbon dioxide in the liquid by releasing the carbon dioxide in the waste water by raising the temperature inside, or by bubbling the liquid after separation with a gas-liquid separator with a gas such as air Is preferred.

  For controlling the temperature of the treatment liquid, the treatment liquid may be cooled by a cooling means such as a heat exchanger (not shown) or a cooler 4 before the treatment liquid is supplied to the gas-liquid separator 11, or the heat may be supplied after the gas-liquid separation. Cooling means such as an exchanger (not shown) or a cooler (not shown) may be provided to cool the processing liquid.

  The liquid (processing liquid) obtained by separation with the gas-liquid separator 11 is discharged from the processing liquid discharge line 15. The discharged liquid may be further subjected to various known steps such as biological treatment and membrane separation treatment for further purification treatment. Furthermore, a part of the treatment liquid obtained through the wet oxidation treatment is directly returned to the wastewater before being subjected to the wet oxidation treatment, or supplied to the wastewater from an arbitrary position of the wastewater supply line, and then subjected to the wet oxidation treatment. May be. For example, the processing liquid obtained through the wet oxidation treatment may be used as the waste water dilution water to reduce the TOD concentration or COD concentration of the waste water. Further, the gas obtained by separation by the gas-liquid separator 11 is discharged from the gas discharge line 14 to the outside. The discharged exhaust gas can be further subjected to another process. Moreover, when performing the wet oxidation process used by this invention, a heat exchanger can also be used for a heater and a cooler, and these can be used in combination as appropriate.

  Hereinafter, although embodiment of this invention is described in detail using an Example, the technical scope of this invention should not be limited and limited to the following Example.

[Example 1]
Dissolve 1.29 kg of zirconyl nitrate (ZrO (NO ₃ ) ₂ .2H ₂ O) in 4 L of pure water, and uniformly add 11.6 kg of 81.6 mass% (TiO ₂ equivalent) metatitanic acid (H ₂ TiO ₃ ). And dried at 80 ° C. with mixing. The obtained gel was heated to 600 ° C. over 5 hours and maintained for 5 hours, and further heated to 720 ° C. over 8 hours and maintained for 2 hours. The produced fired product was pulverized with a hammer mill to obtain a Ti—Zr composite oxide powder 1. A molding aid and an appropriate amount of pure water were added to the prepared Ti—Zr composite oxide powder 1, and the mixture was kneaded using a kneader, and then extruded into a cylindrical shape having a diameter of 5 mm and a length of 6 mm. Then, it dried at 150 degreeC and further baked at 450 degreeC for 5 hours, and obtained the pellet-shaped base material. The obtained Ti—Zr composite oxide pellet-like base material was impregnated with an aqueous palladium nitrate solution and then dried at 120 ° C. for 6 hours, and then subjected to calcination treatment at 400 ° C. for 3 hours using a hydrogen-containing gas. -1 was obtained. The main component of the obtained catalyst and its mass ratio were TiO ₂ : ZrO ₂ : Pd = 59.3: 39.2: 1.5. The BET specific surface area of this catalyst A-1 was 48 m ² / g, and the peak intensity showing the Ti—Zr composite oxide was 1210 counts. Moreover, the ratio (peak intensity ratio X / Y) to the intensity of the peak indicating the anatase crystal of the TiO ₂ reference sample was 0.80.

[Example 2]
The gel obtained in the same manner as in Example 1 was heated to 420 ° C. over 5 hours and held for 5 hours, and further heated to 720 ° C. over 8 hours and held for 2 hours. The fired product thus produced was pulverized with a hammer mill to obtain a Ti—Zr composite oxide powder 2. Pellets were prepared in the same manner as in Example 1 except that the prepared Ti—Zr composite oxide powder 2 was used. Next, catalyst A-2 was obtained by adding palladium in the same manner as in Example 1. The main component of the obtained catalyst and its mass ratio were TiO ₂ : ZrO ₂ : Pd = 59.3: 39.2: 1.5. The BET specific surface area of this catalyst A-2 was 32 m ² / g, and the peak intensity of the Ti—Zr composite oxide was 1165 counts. Moreover, the ratio (peak intensity ratio X / Y) to the intensity of the peak indicating the anatase crystal of the TiO ₂ reference sample was 0.77.

[Example 3]
A homogeneous solution was prepared by mixing 25 L of pure water, 8.8 L of sulfuric acid solution of 200 g / L (in terms of TiO ₂ ) titanyl sulfate and 3.4 L of 220 g / L (in terms of CeO ₂ ) cerium nitrate aqueous solution. A 25% aqueous ammonia solution was added dropwise to this solution with sufficient stirring while cooling so that the liquid temperature did not exceed 40 ° C. until pH 8.7 was reached, and a precipitate was formed. . The obtained slurry was filtered, washed with pure water, and dried at 150 ° C. for 15 hours. The temperature was raised to 420 ° C. over 5 hours and maintained for 5 hours, and further heated to 740 ° C. over 8 hours and maintained for 2 hours. The produced fired product was pulverized with a hammer mill to obtain a Ti—Ce composite oxide powder. Pellets were prepared in the same manner as in Example 1 except that the prepared Ti—Ce composite oxide powder was used. While constantly shaking the obtained Ti—Ce composite oxide pellet-like substrate, a mixed aqueous solution of ruthenium chloride and platinum chloride was sprayed and added thereto, and then dried at 120 ° C. for 6 hours. A catalyst B was obtained by performing a calcination treatment at 400 ° C. for 3 hours. The main component of the obtained catalyst and its mass ratio were TiO ₂ : CeO ₂ : Ru: Pt = 70.3: 29.5: 0.15: 0.05. The BET specific surface area of this catalyst B was 62 m ² / g, and the peak intensity of the Ti—Ce composite oxide was 1745 counts. Moreover, the ratio (peak intensity ratio X / Y) to the intensity of the peak indicating the anatase crystal of the TiO ₂ reference sample was 1.15.

[Example 4]
25 L of pure water, 5.6 L of sulfuric acid solution of 200 g / L (converted to TiO ₂ ) titanyl sulfate and 8.9 L of 155 g / L (converted to Fe ₂ O ₃ ) iron nitrate aqueous solution were mixed to prepare a uniform solution. To this solution, a 25% aqueous ammonia solution was gradually added dropwise with sufficient stirring until the pH reached 7.5 while cooling so that the liquid temperature did not exceed 40 ° C., and the mixture was allowed to stand for 15 hours. . The obtained slurry was filtered, washed with pure water, and dried at 150 ° C. for 15 hours. This was heated up to 360 ° C. over 3 hours and maintained at temperature for 5 hours, and further heated up to 650 ° C. over 8 hours and held at temperature for 2 hours. The fired product thus produced was pulverized with a hammer mill to obtain a Ti—Fe composite oxide powder. Pellets were prepared in the same manner as in Example 1 except that the prepared Ti—Fe composite oxide powder was used. While constantly shaking the obtained Ti—Fe composite oxide pellet base material, a mixed aqueous solution of ruthenium chloride and palladium chloride was sprayed and added thereto, and then dried at 120 ° C. for 6 hours. A catalyst C was obtained by performing a calcination treatment at 400 ° C. for 3 hours. The main component of the obtained catalyst and the mass ratio thereof were TiO ₂ : Fe ₂ O ₃ : Ru: Pd = 44.5: 54.9: 0.35: 0.25. The BET specific surface area of the catalyst C was 58 m ² / g, and the peak intensity of the Ti—Fe composite oxide was 1500 counts. Moreover, the ratio (peak intensity ratio X / Y) to the intensity of the peak indicating the anatase crystal of the TiO ₂ reference sample was 0.72.

[Example 5]
25 L of pure water and 200 g / L (in terms of TiO ₂ ) 12.5 L of sulfuric acid solution of titanyl sulfate were mixed to prepare a uniform solution. A 25% aqueous ammonia solution was added dropwise to this solution under sufficient stirring while cooling so that the liquid temperature did not exceed 40 ° C. until pH 7.9 was reached, and a precipitate was formed. . The obtained slurry was filtered, washed with pure water, and dried at 150 ° C. for 15 hours. This was heated up to 620 ° C. over 5 hours and maintained at temperature for 5 hours, and further heated up to 760 ° C. over 8 hours and held at temperature for 2 hours. The fired product was pulverized with a hammer mill to obtain a TiO ₂ powder. Pellets were prepared in the same manner as in Example 1 except that the prepared TiO ₂ powder was used. While constantly shaking the obtained TiO ₂ pellet-like base material, a mixed aqueous solution of platinum chloride and iridium chloride was sprayed and added thereto, followed by drying at 120 ° C. for 6 hours, and then using a hydrogen-containing gas at 400 ° C. The catalyst D was obtained by performing a calcination treatment for 3 hours. The main component of the obtained catalyst and its mass ratio were TiO ₂ : Pt: Ir = 99.65: 0.08: 0.27. The catalyst D had a BET specific surface area of 33 m ² / g and a peak intensity indicative of TiO ₂ of 1990 counts. Moreover, the ratio (peak intensity ratio X / Y) to the intensity of the peak indicating the anatase crystal of the TiO ₂ reference sample was 1.35.

[Comparative Example 1]
The gel obtained in the same manner as in Example 1 was heated to 720 ° C. over 3 hours, and the temperature was maintained for 3 hours. The fired product thus produced was pulverized with a hammer mill to obtain a Ti—Zr composite oxide powder 3. Pellets were prepared in the same manner as in Example 1 except that the prepared Ti—Zr composite oxide powder 3 was used. Then, catalyst E-1 was obtained by adding palladium in the same manner as in Example 1. The main component of the obtained catalyst and its mass ratio were TiO ₂ : ZrO ₂ : Pd = 59.3: 39.2: 1.5. The catalyst E-1 had a BET specific surface area of 30 m ² / g, and the peak intensity of the Ti—Zr composite oxide was 2853 counts. Moreover, the ratio (peak intensity ratio X / Y) to the intensity of the peak indicating the anatase crystal of the TiO ₂ reference sample was 1.89.

[Comparative Examples 2 to 5]
In Comparative Example 1, the time taken to raise the temperature to 720 ° C. was 5 hours (Catalyst E-2; Comparative Example 2), 8 hours (Catalyst E-3; Comparative Example 3), and 10 hours (Catalyst E-4; Comparative Example 4) A catalyst was obtained in the same manner as in Example 1 except that the time was changed to 15 hours (Catalyst E-5; Comparative Example 5). The main component of the obtained catalyst and the mass ratio thereof were TiO ₂ : ZrO ₂ : Pd = 59.3: 39.2: 1.5. Table 2 below shows the BET specific surface area of these catalysts and the ratio (peak intensity ratio X / Y) to the intensity of the peak indicating the anatase crystal in the TiO ₂ reference material.

[Comparative Example 6]
Catalyst F-1 was obtained by adding iridium in the same manner as in Example 5 except that a commercially available TiO ₂ pellet-shaped substrate (ST61120, manufactured by Saint-Gobain) was used. The main component of the obtained catalyst and its mass ratio were TiO ₂ : Pt: Ir = 99.65: 0.08: 0.27. The catalyst F-1 had a BET specific surface area of 150 m ² / g and a peak intensity showing TiO ₂ of 2660 counts. Moreover, the ratio (peak intensity ratio X / Y) to the intensity of the peak indicating the anatase crystal of the TiO ₂ reference sample was 1.77.

[Comparative Example 7]
A catalyst F-2 was obtained by adding iridium in the same manner as in Example 5 except that a commercially available TiO ₂ pellet-shaped substrate (ST31119, manufactured by Saint-Gobain) was used. The main component of the obtained catalyst and its mass ratio were TiO ₂ : Pt: Ir = 99.65: 0.08: 0.27. The catalyst F-2 had a BET specific surface area of 38 m ² / g and a peak intensity showing TiO ₂ of 3494 counts. Moreover, the ratio (peak intensity ratio X / Y) to the intensity of the peak indicating the anatase crystal of the TiO ₂ reference sample was 2.39.

[Evaluation of catalyst]
Using the catalyst obtained in each of the above Examples and Comparative Examples, the apparatus shown in FIG. 1 was used to treat wastewater for 5000 hours under the following conditions, and the performance of the catalyst was evaluated.

First, 1.5 L of catalyst was packed inside the reaction tower (cylindrical shape having an inner diameter of 26 mm and a length of 3000 mm). The waste water used for the treatment was waste water mainly discharged from the chemical plant and contained 1,4-dioxane, formaldehyde and acetic acid, and COD (Cr) was 42 g / L. This wastewater was supplied to the wastewater pressurizing pump 5 through the wastewater introduction line 6, boosted at a flow rate of 3.5 L / h, then heated to 280 ° C. with the heater 3 and supplied from the bottom of the reaction tower 1. In addition, air is supplied from the oxygen-containing gas supply line 8 and the pressure is increased by the compressor 7, and then O ₂ / COD (Cr) ((the amount of oxygen in the supply gas per hour) / (chemical wastewater per hour). The flow rate was controlled by the oxygen-containing gas flow rate adjustment valve 9 so that the required oxygen amount)) = 1.25, and mixed into the waste water before the heater 3. In addition, in the reaction tower 1, it processed by the gas-liquid upward cocurrent flow. In the reaction tower 1, the temperature of the waste water was kept at 280 ° C. using the electric heater 2, and the oxidation / decomposition treatment was performed. The obtained processing liquid was sent to the gas-liquid separator 11 through the processing liquid line 10 and separated into gas and liquid. At this time, the liquid level was detected inside the gas-liquid separator 11 using the liquid level controller LC, and the processing liquid was discharged from the liquid level control valve 13 so as to maintain a constant liquid level. Moreover, the pressure of the pressure control valve 12 was detected using the pressure controller PC, and it controlled so that the pressure of 8.2 MPa (Gauge) was hold | maintained.

  In this evaluation, “COD (Cr) removal rate” was calculated according to the following formula 1. The “COD (Cr) removal rate” is a percentage of the COD (Cr) 42 g / L of the waste water before treatment, which is removed by the treatment with the catalyst. In addition, “COD (Cr) removal rate” was measured both immediately after the treatment of waste water and after 5000 hours. The obtained results are shown in Table 1 below.

  In this evaluation, the “abrasion reduction rate” of the catalyst was calculated according to the following formula 2. This “wear reduction rate” is a percentage of the weight of the catalyst used in the treatment, which was reduced by wear after the wastewater treatment reaction for 5000 hours. The “weight after reaction” is a weight measured after washing the catalyst after the wastewater treatment reaction for 5000 hours with pure water and then drying at 150 ° C. for 15 hours or more.

  From the results shown in Table 1, when the catalysts of Examples 1 to 5 having a peak intensity ratio (X / Y) value of 0.50 to 1.70 were used, the peak intensity ratio (X / Y) It can be seen that the COD (Cr) removal rate after 5000 hours is maintained at a very high value as compared with the case of using the catalysts of Comparative Examples 1 to 7 whose values are out of the above range. Since the values of the wear reduction rate of the catalyst of each example are smaller than the values of the wear reduction rate of the catalyst of each comparative example, the COD (Cr) removal rate over a long period when the catalyst of each example is used. Is maintained at a high value because the wear resistance (durability) of the catalyst itself is improved.

1 ... reaction tower,
2 ... Electric heater,
3 ... heater,
4 ... Cooler,
5 ... Wastewater supply pump,
6 ... Wastewater supply line,
7 ... Compressor,
8 ... Oxygen-containing gas supply line,
9 ... Oxygen-containing gas flow control valve,
10 ... Processing liquid line,
11 ... Gas-liquid separator,
12 ... Pressure control valve,
13 ... Liquid level control valve,
14 ... gas discharge line,
15 ... Processing liquid discharge line,
LC ... Liquid level controller.

Claims (10)

A wastewater treatment catalyst used for wastewater treatment,
A catalyst substrate comprising a titanium-containing compound (A);
A catalytically active component (B) comprising a single element or a compound of one or more elements selected from the group consisting of gold, platinum, palladium, iridium and ruthenium;
Containing, and
The height of the maximum peak existing between 2θ = 24 ° and 33 ° in the powder X-ray diffraction method for the catalyst is X, and 20% by mass of pure anatase-type titanium dioxide and 80% by mass of pure rutile-type titanium dioxide. When the height of a peak showing anatase crystals existing between 2θ = 24 ° and 27 ° of a reference sample obtained by pulverizing and mixing is Y, the value of the ratio of X / Y is 0.50 to 1 A catalyst for wastewater treatment, characterized by being in the range of .70.   The wastewater treatment catalyst according to claim 1, wherein the value of the ratio of X / Y is 0.70 to 1.20.   3. The catalyst base according to claim 1, wherein the catalyst base further contains a single element or a compound (C) of one or more elements selected from the group consisting of iron, silicon, aluminum, zirconium and cerium. Wastewater treatment catalyst.   The catalyst base is a combination of a titanium oxide and a composite oxide of titanium and zirconium, a combination of a titanium oxide, an iron oxide, and a composite oxide of titanium and iron, and oxidation of titanium. The wastewater treatment catalyst according to any one of claims 1 to 3, wherein the wastewater treatment catalyst is any one of products.   The content of the component (A) is 5 to 99.9% by mass relative to the total mass of the catalyst, the content of the component (B) is 0.01 to 5% by mass, and the content of the component (C) The amount of the wastewater treatment according to any one of claims 1 to 4, wherein the amount is 0 to 90% by mass (however, the sum of the component (A) and the component (C) is 95 to 99.9% by mass). Catalyst. A method for producing a wastewater treatment catalyst according to any one of claims 1 to 5,
Preparing a catalyst precursor;
Firing the precursor;
Have
The manufacturing method, wherein the firing includes a first firing step and a second firing step performed at a firing temperature higher than the first firing step.   The manufacturing method according to claim 6, wherein a firing temperature in the first firing step is 300 to 700 ° C, and a firing temperature in the second firing step is 500 to 800 ° C.   A wastewater treatment method comprising a wastewater treatment step of treating wastewater using the catalyst according to any one of claims 1 to 5 or the catalyst produced by the production method according to claim 6 or 7.   The treatment method according to claim 8, wherein the wastewater treatment step is performed by wet oxidation. The catalyst according to any one of claims 1 to 5 or the catalyst produced by the production method according to claim 6 or 7 is reacted so as to have a space velocity of 0.1 to 10 hr ^-1 per catalyst layer. Fill the tower, heat the wastewater together with the oxygen-containing gas 0.5 to 3.0 times the theoretical oxygen demand, supply it to the reaction tower, heat the reaction tower to 80-370 ° C, and oxidize the wastewater by the catalyst -The processing method of Claim 9 including carrying out a decomposition process and carrying out gas-liquid separation of the obtained processing liquid.