JPH062227B2 - Water-resistant carrier, water treatment catalyst containing the carrier, and water treatment method using the catalyst - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a water-resistant carrier, a water treatment catalyst containing the carrier, and a water treatment method using the catalyst. More specifically, the present invention relates to a carrier having stable water resistance in acidic / alkaline water or hot water, a water treatment catalyst containing the carrier, and a water treatment method using the catalyst.

<Prior Art> Carriers and catalysts for water treatment are widely used for chemical treatment of water, biological treatment and the like, and are also used for water treatment, wastewater treatment and the like. As a material for the carrier, there is a material using plastic, activated carbon, ceramic or the like. Some water treatment conditions are used under severe conditions. Especially, the conditions of the wet oxidation method for oxidizing and decomposing wastewater containing a chemical oxygen demand substance (hereinafter referred to as COD component) under high temperature and high pressure are strict, As a method for improving the durability of the carrier used for this, a method using a titania carrier has been proposed.

<Problems to be Solved by the Invention> Conventional carriers and catalysts for water treatment have a problem that they cannot withstand long-term use under severe conditions. For example, a plastic material used in hot hot water may cause melting, and a ceramic material may cause elution of components. In addition, when used in low pH waste water containing a mineral acid or an organic acid, deterioration or elution of components may be accelerated. In particular, carriers and catalysts used in the wet oxidation method are required to have a high degree of durability in hot water and stability under a wide range of pH conditions, but none of them sufficiently satisfies these conditions. According to the study by the present inventors, for example, a wet oxidation catalyst using a titania carrier has water resistance initially, but it is found that the catalyst strength lowers over a long period of time.

Therefore, in view of the above various drawbacks, the object of the present invention is to
In the water treatment, it is to resist the carrier and the catalyst having strength stability for a long period of time as compared with these conventional products. Yet another object of the present invention is to provide a method of using the catalyst.

<Means for Solving Problems> The present invention provides (1) 20 to 90 mol of titania (TiO ₂ ) obtained by heating a mixture of a titanium compound and a zirconium compound at a temperature in the range of 660 to 900 ° C. % And 10 to 80 mol% as zirconia (ZrO ₂ ),
And a water-resistant carrier characterized by containing at least 20% by weight of a composite oxide of titanium and zirconium having a crystal structure of ZrTiO _4, based on the carrier, (2) In the above water-resistant carrier, manganese as a catalyst component,
Iron, cobalt, nickel, cerium, tungsten,
At least one selected from the group consisting of copper, silver, gold, platinum, palladium, rhodium, ruthenium and iridium.
Water treatment catalyst, characterized in that it comprises a metal or its water-insoluble or sparingly soluble compound, and (3) using the water treatment catalyst, the waste water is treated at 100 to 370 ° C.
In the temperature range of and under the pressure at which the wastewater holds the liquid phase,
Wet oxidizing the wastewater under the supply of a gas containing 1.0 to 1.5 times the stoichiometric amount of oxygen required to decompose organic and inorganic substances in the wastewater into nitrogen, carbon dioxide and water. The present invention relates to a characteristic water treatment method.

A feature of the water resistant carrier according to the present invention is that it contains at least 20% by weight based on the carrier, a composite oxide of titanium and zirconium having a crystal structure of ZrTiO ₄ .

Generally, a binary complex oxide composed of titanium and zirconium is disclosed in, for example, Kozo Tabe, Catalyst, Vol. 17, No. 3, 7
As is well known from page 2 (1975), it is known as a solid acid, and each of them constitutes a remarkable acidity which is not found in a single oxide.

That is, it can be recognized that the complex oxide is not a mixture of titanium oxide and zirconium oxide, but that titanium and zirconium form so-called binary complex oxides to exhibit their unique physical properties. Is. This composite oxide is X when fired at low temperature.
As a result of analysis by line diffraction, it has an amorphous or almost amorphous fine structure.

On the other hand, the present inventors can generate a composite oxide of titanium and zirconium having a crystal structure of ZrTiO ₄ by heating a mixture of a titanium compound and a zirconium compound in a temperature range of 660 to 900 ° C. It was found that it is excellent as a component of a sexual carrier.

As a method of producing the carrier containing the crystal structure of ZrTiO _4, a method of previously forming a dense compound of titanium and zirconium and heating the compound in the temperature range of 660 to 900 ° C. is more preferable. Heating temperature is 6
If the temperature is lower than 60 ° C., the crystal structure of ZrTiO ₄ cannot be sufficiently obtained. On the other hand, at 1000 ° C. or higher, the specific surface area of the oxide is remarkably reduced, resulting in deterioration of carrier moldability and carrier strength.

The substance ZrTiO ₄ can be identified by X-ray diffraction. (McClune, WFetc., "1982 Powder Diff
raction File, inorganic Phases, Alphabetical Index ",
JCPDS International Center for Diffraction Data, Pe
See nnsylvania, 1982).

In the water resistant carrier of the present invention, ZrTiO 3
_The ratio of the composite oxide of titanium and zirconium having the crystal structure of _{4 in} the carrier is 20% by weight or more.

The composition of the carrier component is ₂ as TiO 2.
0 to 90 mol% and 10 to 80 mol% as ZrO _2.
Within the range, preferable results are obtained in order to obtain excellent durability, carrier moldability and strength. further,
30-80 mol% as TiO ₂ and ₂ as ZrO 2.
The range of 0 to 70 mol% gives more preferable results.

Further, a composite oxide of titanium and zirconium having a crystal structure of ZrTiO ₄ and an oxide of a rare earth element such as lanthanum and neodymium, titania, zirconia and the like can be used together as a carrier.

The present inventors, when using a carrier component containing the above composite oxide, pellets, spheres, when molded into a honeycomb type or the like, because of its outstanding durability and moldability, high temperature, high pressure, It was found that the carrier shape and strength are maintained for a long period of time even when used in water treatment that requires severe conditions such as low pH. Moreover, it has been found that the catalyst in which the catalyst component is supported on this carrier is excellent not only in durability but also in water treatment efficiency.

That is, according to the study by the present inventors, excellent performance cannot be obtained with titanium or zirconium oxide alone or in a simple mixture. For example, even if it can be molded into a honeycomb shape, it cannot withstand long-term use. On the other hand, it was found that these elements have excellent durability and moldability only when these elements contain the complex oxide. In particular, it has been confirmed that the carrier containing the above composite oxide has further excellent durability in carrier strength in hot water resistance.

The supported amount of the catalytically active component in the water treatment catalyst of the present invention is preferably in the range of 0.05 to 25% by weight in the form of metal or compound. Preferably, the amount of manganese, iron, cobalt, nickel, cerium, tungsten, copper and silver used is 0 to 25% by weight as a compound (for example, oxide, chloride, sulfide, etc.), platinum, gold, palladium. The amount of rhodium, ruthenium and iridium used is 0 to 10% by weight as metal (however, the total amount of both is 0.05 to
It is 25% by weight. ). More preferably, the catalytically active component is 0.1 to 15% by weight in the form of a metal or compound.
Preferably, the amount of manganese, iron, cobalt, nickel, cerium, tungsten, copper and silver used is 0 to 15% by weight as a compound, and the amount of platinum, gold, palladium, rhodium, ruthenium and iridium used is 0 as a metal. .About.5% by weight (however, the total amount of both is 0.1 to 15% by weight).

When the amount of the catalytically active component is out of the above range, the water treatment activity is insufficient, and in the case of a noble metal such as platinum, palladium and rhodium, the raw material cost becomes high and the corresponding sufficient effect cannot be exhibited.

The carrier and catalyst of the present invention preferably have the composition specified as described above, and have various shapes such as pellets, spheres, rings, saddles, powders, crushed types, and monolithic structures such as honeycombs. Can be adopted. A honeycomb structure is preferable, and a structure having a through hole having an equivalent diameter of 2 to 20 mm, a cell wall thickness of 0.5 to 3 mm, and an opening ratio of 50 to 80% is particularly preferable. Is. When the honeycomb structure has a larger pore diameter (diameter equivalent to the through hole), the flow resistance is proportionally smaller and clogging by solid matter can be prevented, but at the same time, the geometric surface area of the structure is also smaller, which is constant. In order to achieve the above treatment efficiency, it is necessary to increase the amount of the structure by the amount corresponding to the increase in the pore size. Therefore, the pore size is limited in relation to the processing efficiency and the processing performance.

In the above-mentioned honeycomb structure, the equivalent diameter of the through hole is 2
It is in the range of -20 mm, preferably 4-12 mm. When the equivalent diameter is less than 2 mm, the pressure loss is large, and particularly when the solid content is contained in the water to be treated, clogging easily occurs and it becomes difficult to use for a long period of time. When the equivalent diameter exceeds 20 mm, the pressure loss decreases and the possibility of clogging decreases, but the treatment activity is not sufficient.

The cell wall thickness is in the range of 0.5 to 3 mm, preferably 0.5 to 2 mm. When the cell wall thickness is less than 0.5 mm, there is an advantage that the pressure loss becomes small and the structure can be lightened, but it is not preferable because the mechanical strength decreases. Cell thickness is 3 mm
If it exceeds, the mechanical strength is sufficient, but there is a drawback that the pressure loss becomes large.

The aperture ratio is 50 to 80% for the same reason as above.

In consideration of the above circumstances, a particularly preferable honeycomb type structure used in the present invention has a through hole having an equivalent diameter of 2 to 20 mm, a cell wall thickness of 0.5 to 3 mm and an opening ratio of 50.
The range is -80%. The honeycomb structure satisfying these conditions has a reaction temperature of 100 to 370 ° C., and is sufficient even under severe reaction conditions of high temperature and high pressure where the reaction pressure is equal to or higher than the pressure for holding the liquid phase of the water to be treated. Since it has excellent mechanical strength and has a sufficient geometric surface area of the structure, it has excellent durability and can be treated with water at a high linear velocity with a low pressure loss. Further, even when the water to be treated contains a solid content, clogging does not occur and high activity can be maintained for a long period of time.

As the shape of the through hole, any shape such as a quadrangle, a hexagon, and a wave shape can be adopted as long as the equivalent diameter is within the above range.

The composite oxide of titanium and zirconium having the crystal structure of ZrTiO _{4 of the} present invention is at least 2 on the basis of the carrier.
To prepare a water-resistant carrier containing 0% by weight, first select from titanium sources such as titanium chloride, titanium sulfate, titanates and other inorganic titanium compounds, and titanium oxalate, tetraisopropyl titanate and other organic titanium compounds. The zirconium source can be selected from inorganic zirconium compounds such as zirconium oxychloride, zirconium nitrate and zirconium sulfate, and organic zirconium compounds such as zirconium oxalate.

And the following method is mentioned as a preferable preparation method.

A method in which titanium tetrachloride is mixed with zirconium oxychloride, ammonia is added to form a precipitate, and the precipitate is washed, dried and heated at 660 to 900 ° C.

Zirconyl nitrate was added to titanium tetrachloride, and a thermal hydrolysis reaction was carried out to form a precipitate, which was washed, dried and dried.
A method of heating at 60 to 900 ° C.

A method in which zirconyl nitrate is added to titanic acid, and the mixture is heated to cause thermal decomposition and then heated at 660 to 900 ° C.

Among the above preferable methods, the most preferable method is preferable, and this method is specifically carried out as follows. That is, the compounds of the titanium source and the zirconium source are taken so that the molar ratio of TiO ₂ and ZrO ₂ becomes a predetermined amount,
Titanium and zirconium are converted into oxides in an acidic aqueous solution state to have a concentration of 1 to 100 g / 10 to 100 ° C.
Keep on. Ammonia water as a neutralizing agent was added dropwise thereto with stirring to form a coprecipitated compound consisting of titanium and zirconium at pH 2 to 10 for 10 minutes to 3 hours, separated and washed well, and then 80 to 140 ° C. So 1 to 1
It is a method of drying for 0 hours and heating at 660 to 900 ° C. for 0.5 to 10 hours.

A water resistant carrier (hereinafter referred to as Ti) containing at least 20% by weight based on the carrier, a composite oxide of titanium and zirconium having a crystal structure of ZrTiO ₄ prepared by the above method.
And O ₂ -ZrO _2. ) Is used to obtain a finished catalyst by the method shown below. For example, TiO ₂ —ZrO ₂
The powder is added together with a molding aid, mixed and kneaded while adding an appropriate amount of water, and molded into a spherical shape, a pellet shape, a plate shape, a honeycomb shape or the like by an extrusion molding machine.

The molded product can be dried at 50 to 120 ° C. and then calcined at 300 to 800 ° C., preferably 350 to 600 ° C. for 1 to 10 hours, preferably 2 to 6 hours under air flow to obtain a catalyst.

Starting materials for the catalytically active components include oxides, hydroxides,
Examples thereof include inorganic oxide salts and organic acid salts. For example, an ammonium salt, an oxalate salt, a nitrate salt, a sulfate salt or a halide is appropriately selected.

When manganese, iron, nickel, cobalt, tungsten, cerium, copper, silver, gold, platinum, palladium, rhodium, ruthenium and / or iridium is added to TiO ₂ —ZrO ₂ for catalysis, an aqueous solution of the above metal salt is added. T
iO ₂ -ZrO ₂ molded body was impregnated and supported, then dried,
It can be catalyzed by firing.

Alternatively, a method in which an aqueous solution of the above metal salt is added to a TiO ₂ —ZrO ₂ powder together with a molding aid and kneading and molding can be adopted.

The water treatment carrier and catalyst of the present invention can treat the target component contained in the water by contacting it with tap water, sewage, waste water, or the like. Specific examples of treatment include adsorption of heavy metals in hot water, removal of ozone from water column, excess of strongly alkaline / acidic water, oxidation treatment in hot water, sterilization treatment of bacteria and microorganisms in water. .

In particular, the water treatment method provided by the present invention includes activated sludge-treated supernatant water or precipitated activated sludge, fermentation wastewater, wastewater from the organic compound polymerization step, cyanide-containing wastewater, phenol-containing wastewater, oil-containing wastewater, and other chemicals. It is excellent for wet oxidation treatment of industrial wastewater, general industrial wastewater from food factories, and further wastewater containing oxidizable organic or inorganic substances such as human waste, sewage, and sewage sludge. The contact method with the waste water may be either a column packing method, a batch method or the like, but when a honeycomb type catalyst is used, waste water containing 0.1 g / solid or more of solid matter can be stably treated for a long period of time. You can

The reaction conditions in the present invention are that the reaction temperature is 370 ° C. or lower,
Usually 100 to 370 ° C, more preferably 200 to 300
℃. The pressure of the reaction system may be a pressure sufficient to maintain the liquid phase of the waste water in the reaction tower, that is, a pressure of 1 to about 200 kg / cm ² . The molecular oxygen-containing gas to be fed is used in an amount 1 to 1.5 times the theoretical amount of oxygen required for oxidative decomposition. The amount of the catalyst used is about 5 to 99% of the space volume of the reaction tower. Waste water stays in the catalyst bed at a specified temperature for a residence time of 6 to 1
It is oxidized in 20 minutes, preferably 12 to 60 minutes by flowing it together with the molecular oxygen-containing gas.

As the molecular oxygen-containing gas, air, a mixed gas of oxygen and air, or a gas usually called oxygen-enriched air can be used. The pH of the reaction system can be either acidic or alkaline.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1 An aqueous sulfuric acid solution of titanyl sulfate having the following composition was used as a titanium source.

TiOSO ₄ (converted to TiO ₂ ) 250 g / total H ₂ SO ₄ 1100 g / water 100 to zirconium oxychloride [ZrOCl ₂ ·
8H ₂ O] 1.99 kg was dissolved, and an aqueous sulfuric acid solution 2.96 of titanyl sulfate having the above composition was added and mixed well. While maintaining the temperature at about 30 ° C. and stirring well, ammonia water was gradually added dropwise, and the pH was adjusted to 7 and then allowed to stand for 15 hours.

The TiO ₂ —ZrO ₂ gel thus obtained was washed with water and dried at 200 ° C. for 10 hours. Then under air atmosphere 7
The mixture was heated at 00 ° C for 3 hours. The composition of the obtained powder is TiO
₂ : ZrO ₂ = 6: 4 (molar ratio), the BET surface area was 60 m ₂ / g, and as a result of X-ray diffraction analysis, it had a crystal structure of ZrTiO ₄ . The ratio of this crystal structure in all oxides was 40% by weight. The powder obtained here is hereinafter referred to as P-1, and a catalyst was prepared using this powder by the method described below.

900 ml of water, 1500 g of the powder and 75 g of starch were added, mixed and kneaded well with a kneader. After further kneading while adding an appropriate amount of water, extrusion molding was performed into a honeycomb type having a hole diameter (equivalent diameter of the through hole) of 4 mm and an opening ratio of 64%.
After drying at 20 ° C for 6 hours, baking at 450 ° C for 6 hours The molded body thus obtained was impregnated with an aqueous chloroplatinic acid solution, then dried at 120 ° C for 6 hours, and then at 400 ° C for 3 hours.
Burned for hours.

The composition of the obtained finished catalyst was P-1: Pt = 99 by weight ratio.
It was 2: 0.8.

Example 2 Zirconyl nitrate [ZrO (NO ₃ ) ₂ .2H ₂ 0] 1.29k in water 4
g was dissolved, 0.9 kg of titanic acid (converted to TiO ₂ ) was added thereto, and the mixture was well mixed and dried at 80 ° C. Then, it was baked in an air atmosphere at 750 ° C. for 3 hours. The composition of the obtained powder was such that the molar ratio of TiO ₂ and ZrO ₂ was 7: 3. The BET surface area of this powder is 30 m ² / g, and X
As a result of line diffraction analysis, it had a crystal structure of ZrTiO ₄ . The ratio of this crystal structure in all oxides was 60% by weight. The powder obtained here is hereinafter referred to as P-2.

450 ml of water, 1000 g of the above powder and 30 g of starch were added, mixed and kneaded well in a kneader. This is extruded into a cylindrical pellet with a diameter of 5 mm and dried, then at 450 ° C.
It was baked for 6 hours.

Then, in accordance with the method described in Example 1 except that the aqueous solution of palladium nitrate was used in place of the aqueous solution of chloroplatinic acid, P was added in a weight ratio.
A catalyst of -2: Pd = 98.5: 1.5 was obtained.

Example 3 Using the catalysts obtained in Examples 1 and 2, wastewater treatment by a wet oxidation method was performed by the following method. A stainless-steel reaction tube was filled with a catalyst, and waste water preheated and mixed with air having an oxygen concentration of 21% was supplied from the lower part of the reaction tube to 500
It was continuously introduced for 0 hours, and C was introduced at the inlet and outlet of the reaction tube.
OD (Cr) was measured and the removal rate after 5000 hours of reaction was determined. Further, the strength of the catalyst was also measured at the initial stage and after the reaction for 5000 hours to obtain the catalyst strength ratio. The property of the wastewater used for the treatment was 40 g of COD (Cr) / pH3. The reaction conditions are a reaction temperature of 230 ° C and a reaction pressure of 60 kg /
It was cm ² , and was introduced into the reaction tube at a spatial velocity of waste water of 1.5 Hr ^-1 (empty column standard) and an air spatial velocity of 240 Hr ^-1 (blank column standard, standard state). The results obtained are shown in Table 1.

Examples 4 to 12 In the same manner as in Example 1, catalysts shown in Table 2 were obtained.

Using this catalyst, wastewater treatment by wet oxidation was performed by the following method.

A stainless steel reaction tube was filled with a catalyst, and waste water preheated and mixed with air having an oxygen concentration of 21% was supplied from the lower part of the reaction tube to 10 times.
It was continuously introduced for 00 hours, COD (Cr) was measured at the inlet and outlet of the reaction tube, and the removal rate after 1000 hours of reaction was determined. Also, regarding the strength of the catalyst,
After the reaction with time, measurement was performed to obtain the multiple strength ratio. In addition, the property of the wastewater used for the treatment is 30 g of COD (Cr) / pH5.
Met. The reaction conditions are a reaction temperature of 230 ° C. and a reaction pressure of 60.
It was kg / cm ² , and was introduced into the reaction tube at a wastewater space velocity of 1.5 Hr ^-1 (empty column standard) and an air space velocity of 180 Hr ^-1 (blank column standard, standard state). The results obtained are shown in Table 3.

Comparative Example 1 A commercially available titanium oxide carrier was immersed in an aqueous ruthenium nitrate solution,
After drying at 120 ° C. for 8 hours, it was heated at 400 ° C. for 8 hours to obtain the catalysts shown in Table 4.

Using this catalyst, the same reaction as in Example 4 was performed. The results obtained are shown in Table 5.

Comparative Example 2 4 liters of water in zirconyl nitrate _{(ZrO (NO 3) 2 ·} 2
H ₂ O) 1.29 kg is dissolved, and titanic acid 0.9 kg (Ti
(O ₂ conversion) was added and mixed well and dried at 80 ° C.

Then, it heated at 500 degreeC in the air atmosphere for 3 hours. The composition of the obtained powder was such that the molar ratio of TiO ₂ and ZrO ₂ was 7:
It was 3. The BET surface area of this powder is 80 m ² /
It had a crystal structure of ZrTiO _{4 as} a result of X-ray diffraction, but its content was 5% by weight of all oxides.

Using the above powder as a carrier, a catalyst having the same composition was obtained by the same method as in Example 2. Using this catalyst, the same reaction as in Example 4 was performed. The results obtained are shown in Table 5.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI Technical display location B01J 23/48 ZAB M 8017-4G 23/72 ZAB M 8017-4G 23/74 ZAB M 8017-4G 32/00 C02F 1/74 ZAB 9045-4D 101 9045-4D (72) Inventor Akira Inoue 1 992, Nishioki, Nishihama, Kamahama-ku, Himeji-shi, Hyogo Prefecture Catalytic Research Institute Tokiko Nakata (56) References Japanese Patent Laid-Open No. 62-97643 (JP, A) JP-B-3-34997 (JP, B2)

Claims (3)

[Claims] 1. A mixture of a titanium compound and a zirconium compound, which is obtained by heating at a temperature in the range of 660 to 900 ° C., as titania (TiO ₂ ) 20 to 90 mol%, and zirconia (ZrO ₂ ) 10 to 80 mol. %, And at least 20% by weight of a composite oxide of titanium and zirconium having a crystal structure of ZrTiO ₄ based on the carrier. 2. A titania (TiO ₂ ) content of 20 to 90 mol% and a zirconia (ZrO ₂ ) content of 10 to 80 mol, obtained by heating a mixture of a titanium compound and a zirconium compound at a temperature in the range of 660 to 900 ° C. %, And at least 20% by weight of a composite oxide of titanium and zirconium having a crystal structure of ZrTiO _{4 on the} basis of the carrier, as a catalyst component,
At least one metal selected from the group consisting of manganese, iron, cobalt, nickel, cerium, tungsten, copper, silver, gold, platinum, palladium, rhodium, ruthenium and iridium or a water-insoluble or sparingly soluble compound thereof. A catalyst for water treatment, which is supported. 3. A mixture of a titanium compound and a zirconium compound is heated at a temperature in the range of 660 to 900 ° C. to obtain 20 to 90 mol% of titania (TiO ₂ ) and 10 to 80 mol of zirconia (ZrO ₂ ). %, And at least 20% by weight of a composite oxide of titanium and zirconium having a crystal structure of ZrTiO _{4 on the} basis of the carrier, as a catalyst component,
At least one metal selected from the group consisting of manganese, iron, cobalt, nickel, cerium, tungsten, copper, silver, gold, platinum, palladium, rhodium, ruthenium and iridium or a water-insoluble or sparingly soluble compound thereof. Using a supported water treatment catalyst, the wastewater is heated to a temperature range of 100 to 370 ° C., and under a pressure at which the wastewater holds a liquid phase, organic and inorganic substances in the wastewater are converted into nitrogen and carbon dioxide gas. And a method for water treatment, characterized in that the wastewater is wet-oxidized under the supply of a gas containing 1.0 to 1.5 times the stoichiometric amount of oxygen necessary to decompose it into water.