JPH0366018B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for regenerating catalysts used in wet oxidation of wastewater. Chemical oxygen demand substances (hereinafter referred to as COD components),
Various methods have been proposed for treating wastewater containing suspended solids and, in some cases, ammonia and the like. As a result of many years of research into such wastewater treatment methods, the inventors have determined that the type of catalyst, the concentration and supply amount of oxygen used in wet oxidation,
We have discovered that preliminary PH adjustment of wastewater, supply of alkaline substances during wet oxidation reactions, etc. greatly affect treatment efficiency, corrosion of equipment used, and catalyst life, and have already filed a patent application based on this knowledge. Natsuteru (Patent Application No. 51-95507, Patent Application No. 110257-1972,
(Patent Application No. 165168, etc.). In these first-to-file methods,
Metals such as iron, cobalt, nickel, ruthenium, palladium, rhodium, iridium, platinum, gold, copper, and tungsten, as well as at least one kind of water-insoluble or sparingly soluble compounds of these metals, as they are, or alumina, silica, and silica. It can be used as a catalyst in a state where it is supported on a carrier such as alumina, titania, zirconia, or activated carbon. Since such catalysts (hereinafter simply referred to as wastewater oxidation catalysts) are used in large quantities in wastewater treatment, it is absolutely necessary to regenerate and repeatedly use catalysts whose activity has decreased. The present inventor thought that known catalyst regeneration methods in other fields could be applied to the regeneration of waste water oxidation catalysts, and conducted various experiments, but it was found that diversion of known methods was not necessarily effective. did. For example, when regenerating a waste water oxidation catalyst using only known regenerants such as hydrogen, steam, or oxygen, the substances adhering to the catalyst surface appear to be removed relatively well, but the catalyst becomes inactive. Its own recovery is not sufficient. As a result of conducting research from a new perspective on the method for regenerating the waste water oxidation catalyst, the present inventor discovered that the method for regenerating the waste water oxidation catalyst is based on an aqueous solution containing at least one acid selected from hydrochloric acid, nitric acid, phosphoric acid, acetic acid, and propionic acid. treatment (hereinafter referred to as pickling treatment) and treatment with an aqueous solution containing at least one of hydrazine hydrate, formaldehyde, sodium borohydride, lithium aluminum hydride, sodium tartrate, glucose, potassium formate, and sodium formate (hereinafter referred to as pickling treatment). (hereinafter referred to as liquid-phase reduction treatment) or treatment with a gas containing at least one of hydrogen and carbon monoxide (hereinafter referred to as gas-phase reduction treatment), the activity of the catalyst can be significantly recovered. I found out. The present invention was completed based on such knowledge. In general, when wastewater oxidation catalysts are used for wet oxidation of wastewater at high temperatures (approximately 100 to 370℃),
In addition to precipitation, deposition or adhesion of CD components and suspended solids, precipitation of soluble inorganic substances, chemical attack of catalyst metal by chemically active substances contained in wastewater or generated by decomposition, etc. The activity of the catalyst gradually decreases due to factors such as changes in the chemical and physical properties of the surface. In particular, changes in the microscopic chemical and physical properties of the latter cannot be clearly grasped using current analytical techniques, and therefore have not yet been fully elucidated, but changes in the microscopic chemical and physical properties of the former can be recognized from the outside. It is presumed that this is a factor equivalent to or more important than the cause of the decrease in catalyst activity. However, according to the method of the present invention, these factors that reduce catalyst activity are generally eliminated, so that the waste water oxidation catalyst can recover its activity to the extent that it can be reused, and depending on the treatment conditions, it can be almost as active as a new catalyst. recover to some extent. The waste water oxidation catalyst regenerated by the method of the present invention is
Catalytic active components include iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium,
Platinum, copper, gold, tungsten, and one or two of water-insoluble or sparingly soluble compounds of these metals
Contains more than one species. Compounds that are insoluble or sparingly soluble in water include (i) iron sesquioxide, triiron tetroxide, cobalt monoxide, nickel monoxide, ruthenium dioxide, rhodium sesquioxide, palladium monoxide, iridium dioxide, diferric oxide; Examples include oxides such as copper and tungsten dioxide, (ii) chlorides such as ruthenium chloride and platinum oxide, and (iii) sulfides such as ruthenium sulfide and rhodium sulfide. The present invention includes four inventions by combining a pickling treatment and a liquid phase reduction treatment or a gas phase reduction treatment, so each of them will be explained. () The invention set forth in claim 1 (hereinafter referred to as the first invention of the present application. Also, the invention set forth in claim 2)
The inventions described in items 4 to 4 are also referred to as the second invention. ), the waste water oxidation catalyst is first subjected to pickling treatment. As the pickling agent, an aqueous solution containing at least one acid selected from hydrochloric acid, nitric acid, phosphoric acid, acetic acid, and propionic acid is used. The concentration of the pickling treatment agent in the aqueous solution may vary depending on the amount of supported catalyst metal, the degree of reduction in catalyst activity, the temperature during pickling treatment, etc., but it is usually within a specified range of 0.1 to 5.0, and is preferably It should be around 0.25 to 2.0 regulation. If the concentration is too low, the regeneration effect by pickling will not be sufficient; on the other hand, as the concentration increases, the regeneration effect will gradually improve; This is not acceptable. The pickling treatment is carried out by leaving the waste water oxidation catalyst to be regenerated immersed in an aqueous solution of a pickling treatment agent, or by stirring it in the aqueous solution. The pickling treatment may be carried out by taking out the catalyst from the reaction tower that performs the wet oxidation treatment of wastewater and placing it in a separate treatment tank, or by adding acid to the reaction tower while the catalyst is housed in the wet oxidation reaction tower. The cleaning treatment may be carried out by continuously circulating the cleaning agent aqueous solution. The treatment conditions are usually 40°C or higher, preferably 60°C or higher, and at a temperature that does not substantially cause acid decomposition, usually at 15°C.
The treatment time is preferably at least 30 minutes, more preferably at least 30 minutes, but the treatment temperature and treatment time are determined based on the degree of catalyst activity reduction, the type of catalyst, the required degree of catalyst activity recovery, and the type of pickling agent. and concentration, etc., and is not necessarily limited. The pressure in carrying out the pickling treatment may be atmospheric pressure, and there is no particular need to pressurize it, but there will be no disadvantages even if it is carried out under pressure. The waste water oxidation catalyst that has been subjected to the pickling treatment has already recovered its activity to a large extent, but it is subsequently subjected to the liquid phase reduction treatment as it is or, if necessary, after washing with water or washing with water and drying. In addition, if the catalyst activity has significantly decreased or the catalyst activity is not recovered sufficiently by one pickling treatment, it is recommended to perform the pickling treatment multiple times and then subject it to the liquid phase reduction treatment. is good. Liquid phase reduction treatment agents include hydrazine hydrate, formaldehyde, sodium borohydride, lithium aluminum hydride, sodium tartrate,
These are glucose, potassium formate, and sodium formate, and are used in the form of an aqueous solution containing at least one of these. The concentration as an aqueous solution may vary depending on the amount of supported catalyst metal, the degree of catalyst activity reduction, the temperature during reduction treatment, etc.
Usually, it is sufficient if it is 0.1% by weight or more. If the concentration is too low, the final regeneration effect will not be sufficiently pronounced; on the other hand, as the concentration increases, the regeneration effect will gradually increase, but even beyond 10% by weight, the regeneration effect will become even more pronounced. Almost no improvement is observed. The concentration of the reducing agent is more preferably 0.2 to 5% by weight. This reduction treatment is carried out by leaving the pickled waste water oxidation catalyst immersed in an aqueous solution of a liquid-phase reduction treatment agent, or by stirring it in the aqueous solution. When the pickling treatment is carried out with the catalyst housed in the wet oxidation reaction tower, it is advantageous to continue the reduction treatment by passing an aqueous solution of the reducing agent through the reaction tower. The reduction treatment conditions are usually preferably 30 minutes or more at a temperature of 20°C or higher, but the conditions also depend on the degree of catalytic activity reduction, the type of catalyst, and the required degree of catalytic activity recovery, as in the case of pickling treatment. , is determined by taking into account the type and concentration of the reducing agent. However, if the temperature is too high, there is a risk that hydrazine and the like will decompose, so this point must be kept in mind. The pressure during this reduction treatment may be atmospheric pressure, and there is no particular need to pressurize it, but no disadvantage will occur even if it is carried out under pressure. If necessary, the liquid phase reduction treatment may be performed multiple times. Furthermore, the cycle of pickling treatment and liquid phase reduction treatment may be performed multiple times. The waste water oxidation catalyst that has undergone the liquid phase reduction treatment subsequent to the pickling treatment is reused as it is or, if necessary, after washing with water or after washing with water and drying. () In the second invention of the present application, the waste water oxidation catalyst is first subjected to a liquid phase reduction treatment, and then a pickling treatment is performed. The liquid phase reduction treatment and the pickling treatment can be performed under the same conditions as in the first invention of the present application. () In the third invention of the present application, the waste water oxidation catalyst is first subjected to pickling treatment, and then gas phase reduction treatment is performed. The pickling treatment is performed under the same conditions as in the first invention. The gas phase reduction treatment is performed by bringing the pickled waste water oxidation catalyst into contact with a gas containing at least one of hydrogen and carbon monoxide.
Gas phase reducing agents include hydrogen, carbon monoxide, mixtures of hydrogen and carbon monoxide, mixtures of hydrogen and water vapor, and mixtures of carbon monoxide and water vapor, as well as nitrogen, carbon dioxide, helium, argon and other non-containing agents. A specific example is a gas mixture to which an active gas is added as a diluent. Catalyst treatment conditions include the amount of supported catalytic metal;
This can vary greatly depending on the degree of catalyst activity reduction, the concentration of active ingredients (hydrogen, carbon monoxide) in the contact gas, the degree of catalyst activity recovery by pickling treatment, etc., but usually the temperature is 300 to 500℃ and the pressure is 1 to 50 atm. (absolute) degree. The treatment time is not particularly limited, but it goes without saying that it should be a time that does not cause catalyst deterioration. Also in the third invention of the present application, the pickling treatment and/or the gas phase reduction treatment may be performed multiple times if necessary. () In the fourth invention of the present application, the waste water oxidation catalyst is first subjected to a gas phase reduction treatment, and then a pickling treatment is performed. The gas phase reduction treatment may be performed in the same manner as in the third invention of the present application, and the pickling treatment may be performed in the same manner as in the first invention of the present application. In addition, in the case of wastewater oxidation catalysts used to treat wastewater that does not contain hardness components (calcium salts, magnesium salts, iron salts, etc.), such as food factory wastewater, brewing factory wastewater, etc., liquid phase reduction treatment or gas phase reduction treatment is required. It has become clear that the catalytic activity can be sufficiently restored by treatment alone. According to the method of the present invention, the following remarkable effects are achieved. (i) Since the factors that reduce catalyst activity are largely removed, the activity of the wastewater oxidation catalyst is recovered to the extent that it can be reused. (ii) Depending on the regeneration treatment conditions, the catalytic activity after regeneration can be recovered to an extent that is almost equal to that of the new catalyst. (iii) By reusing the waste water oxidation catalyst after regeneration, the activity of the waste water oxidation catalyst whose activity has decreased can be further regenerated, and its activity can be made close to that of a new catalyst, which significantly extends the overall life of the catalyst. It became possible to increase the amount. (iv) Wastewater treatment costs are also reduced because catalyst costs required for wastewater treatment are reduced. (v) When using two or more reaction towers for wastewater treatment, the wastewater oxidation catalyst in one of the reaction towers can be regenerated alternately without stopping the wastewater treatment. Labor such as taking out and refilling becomes unnecessary. Example 1 The gas liquid (COD 6000 ppm, total ammonia amount 3000 ppm, total nitrogen amount 4000 ppm) generated in a coke oven was adjusted to pH approximately 10 with a caustic soda solution, and the space velocity was set at a space velocity of 1.0 1/hr (empty column standard) at the bottom of a cylindrical reaction tower. supply to. The gas liquid treated in each of the Examples below contains iron, calcium, and magnesium in a total amount of 15 ppm from the beginning, but in order to more clearly demonstrate the effects of the present invention, the total amount was 1500 ppm These compounds are further added so that The mass velocity of the liquid is 8.0 tons/m ³ ·hr. On the other hand, air is supplied to the lower part of the reaction tower at an hourly velocity of 65 1/hr (on the empty column basis, in terms of standard conditions). The reaction tower includes
A spherical catalyst having a diameter of 5 mm and having a composition as shown in Table 1 below was filled. In Table 1, for example, 1
%Ir- _TiO2 means that 1% by weight of iridium was supported on the titania support. Wet oxidation of the gas liquid was carried out for 10,000 hours while maintaining the inside of the reaction tower at a temperature of 250°C and a pressure of 70 Kg/m ³ G, and while supplying an aqueous solution of caustic soda so that the pH of the liquid after wet oxidation was approximately 7. By doing so, the activity index of the catalyst decreases as shown in Table 1. In addition, analysis of precipitates on the catalyst surface revealed sulfur and ash (silica, iron oxide, magnesium oxide).
The presence of carbon, hydrocarbons, etc. was confirmed, but no carbon or hydrocarbons were detected. The catalyst whose activity has decreased is taken out from the reaction tower and 1
The sample is left immersed in a specified phosphoric acid aqueous solution (80°C) under atmospheric pressure for 1 hour, pickled, and then washed with water for 1 hour. Next, the catalyst was left immersed in a 1% by weight aqueous hydruzine solution (60°C) under atmospheric pressure for 1.5 hours, and then
Wash with water for 1 hour. The regenerated catalysts were used for wastewater treatment in the same manner as above, and the results are shown in Table 1. In this specification, the activity index refers to the ammonia removal rate when wet oxidizing wastewater using the new catalyst is 100, and when wet oxidizing wastewater using each catalyst under the same conditions. refers to the ammonia removal rate of each catalyst. The COD removal rate also shows the same trend as the ammonia removal rate, so it is not displayed.

[Table] From the results shown in Table 1, it is clear that the method of the present invention has a remarkable effect on catalyst activity recovery. Comparative Example 1 A catalyst similar to catalyst No. 1 of Example 1 (1% Ir-
TiO ₂ ) was used in the wet oxidation treatment of a gas liquid in the same manner as in Example 1. Next, Example 1 except that 1N hydrofluoric acid aqueous solution was used in place of 1N phosphoric acid aqueous solution.
The above catalyst was regenerated in the same manner as above. The activity index of the catalyst before and after the regeneration treatment was as follows. Before regeneration treatment After regeneration treatment 71 72 As is clear from the above results, when the specific non-oxidizing acid used in the present invention is used, almost no effect of regeneration treatment is observed. Example 2 A catalyst whose activity has been reduced by the same wastewater treatment operation as in Example 1 is taken out from the reaction tower, immersed in a 1N hydrochloric acid aqueous solution (80°C) for 1 hour under atmospheric pressure, and then washed with water for 1 hour. Next, the catalyst was added to a 1% by weight aqueous sodium formate solution at 60°C under atmospheric pressure.
After soaking for 1.5 hours, wash with water for 1 hour. The results are shown in Table 2.

[Table] Example 3 2% Pd- whose initial catalytic activity index of 100 decreased to 69 as a result of use in the same wastewater treatment as in Example 1
The TiO ₂ catalyst was taken out of the reaction tower, immersed in a 1N aqueous phosphoric acid solution at 80° C. under atmospheric pressure for 1 hour, and then washed with water for 1 hour. Next, the catalyst was added to the following third
Reduction treatment is carried out under the conditions shown in the table. In addition, No.11, 12,
Nos. 13 and 16 are due to liquid phase reduction treatment, and No.
Samples 14, 15 and 17 were obtained by gas phase reduction treatment.

[Table] Example 4 2% Ru-TiO ₂ whose activity index decreased from 100 to 71 when used in the same wastewater treatment as in Example 1.
The catalyst is taken out from the reaction tower and regenerated by acid washing and reduction under the conditions shown in Table 4 below. Incidentally, Nos. 23 to 25 were obtained by gas phase reduction treatment, and the others were obtained by liquid phase reduction treatment.

[Table] Example 5 A 2% Ru-TiO ₂ catalyst whose activity index decreased from 100 to 71 as a result of being used in the same wastewater treatment as in Example 1 was taken out from the reaction tower, and it was treated with each concentration shown in Table 5 below. After being immersed in an aqueous hydrochloric acid solution at 70°C under atmospheric pressure for 1 hour, washed with water for 1 hour, and further immersed in a 1% by weight aqueous sodium formate solution at 60°C under atmospheric pressure for 1.5 hours,
Then wash with water for 1 hour. The results are shown in Table 5.

[Table] Example 6 2% Pd whose activity index decreased from the initial 100 to 69 when used in the same wastewater treatment as in Example 1.
The TiO ₂ catalyst was taken out from the reaction tower, left immersed in a 1N aqueous phosphoric acid solution under atmospheric pressure under the conditions (temperature and time) shown in Table 6 below, and then washed with water for 1 hour.
Next, (a) 1% by weight hydrazine aqueous solution was added under atmospheric pressure.
After soaking at 60℃ for 1.5 hours, wash with water for 1 hour, or
or (b) in a 1% by weight aqueous sodium formate solution under atmospheric pressure.
After soaking at 60℃ for 1.5 hours, wash with water for 1 hour. Table 6 shows the relationship between the temperature and time during pickling treatment, the type of reducing agent, and the degree of catalyst activity recovery.

[Table] Example 7 2% Ru-TiO ₂ whose activity index decreased from 100 to 71 when used in the same wastewater treatment as in Example 1.
The catalyst is taken out from the reaction tower, immersed in a 1N aqueous hydrochloric acid solution at atmospheric pressure at 70°C for 1 hour, and then washed with water for 1 hour. Next, liquid phase reduction treatment (Nos. 35 to 39) or gas phase reduction treatment (Nos. 40 to 39) was performed under the conditions shown in Table 7 below.
42) Do. Table 7 shows the results of catalyst activity recovery.

[Table] Example 8 When a 2% Pd-TiO ₂ catalyst is used in the same wastewater treatment as in Example 1, the activity index decreases from the initial 100 to 69. Therefore, the waste hydroxidation catalyst whose activity has decreased is taken out from the reaction tower, immersed in a 1N aqueous phosphoric acid solution at 80° C. under atmospheric pressure for 1 hour, and then washed with water for 1 hour. Next, the sample was immersed in an aqueous hydrazine solution of each concentration shown in Table 8 below for 1.5 hours at 60° C. under atmospheric pressure, and then washed with water for 1 hour. The relationship between the concentration of the hydrazine aqueous solution and the degree of catalyst activity recovery is shown in Table 8.

[Table] Example 9 (i) Results of using the same wastewater treatment as in Example 1,
2% Pd- whose activity index decreased from 100 to 69
A phosphoric acid aqueous solution is passed through a wastewater wet oxidation reaction tower filled with a TiO ₂ catalyst under the conditions shown in Table 9 below, followed by washing with water and further reduction treatment. The results are shown as No. 46 in Table 9. (ii) As a result of using the same wastewater treatment as in Example 1,
2% Ru− whose activity index decreased from 100 to 71
The TiO ₂ catalyst is pickled and reduced in the reaction tower in the same manner as in (i) above. The results are shown as No. 47 in Table 9.

[Table] Example 10 (i) As a result of using the same wastewater treatment as in Example 1,
2% activity index decreased from initial 100 to 70
A hydrochloric acid aqueous solution is passed through a wastewater wet oxidation reaction tower filled with a Ru-TiO ₂ catalyst under the conditions shown in Table 10 below, followed by washing with water and further reduction treatment with a hydrazine aqueous solution. The results are shown as No. 48 in Table 10. (ii) 2% whose catalytic activity has been restored as described in (i) above.
When the Ru-TiO ₂ catalyst is used again in the same wastewater treatment as in Example 1, the activity index decreases to 69, so it is pickled and reduced in the same manner as in (i) above. The results are shown as No. 49 in Table 10. (iii) When Catalyst No. 49 obtained in (ii) above is used again for the same wastewater treatment as in Example 1, the activity index decreases to 68. This is pickled and reduced in the same manner as in (i) above. The results are shown as No. 50 in Table 10.

[Table] Example 11 A catalyst whose activity had decreased as a result of being used in the same wastewater treatment operation as in Example 1 was removed from the reaction tower.
1% by weight hydrazine aqueous solution (60℃) under atmospheric pressure.
After soaking for 1.5 hours, wash with water for 1 hour. Next, the catalyst was left immersed in a 1N phosphoric acid aqueous solution (80° C.) under atmospheric pressure for 1 hour, and then washed with water for 1 hour. The degree of catalyst activity recovery by regeneration treatment is as shown in Table 11.

[Table] Example 12 A catalyst whose activity had decreased as a result of being used in the same wastewater treatment operation as in Example 1 was removed from the reaction tower.
1% by weight sodium formate aqueous solution at 60°C under atmospheric pressure.
After soaking for 1.5 hours, wash with water for 1 hour. Next, the catalyst was added to a 1N aqueous solution of hydrochloric acid under atmospheric pressure for 80 minutes.
After soaking for 1 hour at ℃, wash with water for 1 hour. The results are shown in Table 12.

[Table] Example 13 As a result of using in the same wastewater treatment operation as in Example 1, the initial catalyst activity index of 100 decreased to 692.
%Pd- _TiO2 catalyst was taken out from the reaction tower and
After reduction treatment under the conditions shown in Table 13, it was immersed in a 1N phosphoric acid aqueous solution at 80°C under atmospheric pressure for 1 hour.
Then wash with water for 1 hour. The degree of catalyst activity recovery by regeneration treatment is as shown in Table 13.

[Table] Example 14 2% Ru- whose activity index decreased from 100 to 71 when used in the same wastewater treatment as in Example 1.
The TiO ₂ catalyst was taken out from the reaction tower and subjected to reduction treatment and pickling treatment under the conditions shown in Table 14 below.
Reproduce. Note that No. 72 and No. 73 were obtained by gas phase reduction treatment, and the others were obtained by liquid phase reduction treatment.

[Table] Example 15 A 2% Ru-TiO ₂ catalyst whose activity index decreased from 100 to 71 as a result of being used in the same wastewater treatment as in Example 1 was taken out of the reaction tower and the concentrations shown in Table 15 below were determined. Sodium formate solution at 70℃ under atmospheric pressure
After being immersed for 1.5 hours, washed with water for 1 hour, further immersed in a 1N hydrochloric acid aqueous solution at 60° C. under atmospheric pressure for 1 hour, and then washed with water for 1 hour. The results are shown in Table 15.

[Table] Example 16 2% Pd- whose activity index decreased from the initial 100 to 69 as a result of use in the same wastewater treatment as in Example 1.
The TiO ₂ catalyst was taken out of the reaction tower, left immersed in a 1% by weight aqueous hydrazine solution under atmospheric pressure under the conditions (temperature and time) shown in Table 16 below, and then washed with water for 1 hour. Next, (a) immerse in a 1N phosphoric acid aqueous solution at 60°C under atmospheric pressure for 1 hour, and then wash with water for 1 hour, or
or (b) 1N propionic acid aqueous solution under atmospheric pressure for 60 minutes.
After soaking at ℃ for 1.5 hours, wash with water for 1 hour. Table 16 shows the relationship between the temperature and time during the reduction treatment, the type of pickling treatment agent, and the degree of catalyst activity recovery.

[Table] Example 17 2% Ru- whose activity index decreased from 100 to 71 when used in the same wastewater treatment as in Example 1.
The TiO ₂ catalyst was taken out from the reaction tower and subjected to reduction treatment under the conditions shown in Table 17 below, then immersed in a 1N hydrochloric acid aqueous solution at 70° C. under atmospheric pressure for 1 hour, and then washed with water for an hour. Table 17 shows the results of catalyst activity recovery.

[Table] Example 18 When a 2% Pd-TiO ₂ catalyst is used in the same wastewater treatment as in Example 1, the activity index decreases from the initial 100 to 69. Therefore, the waste water oxidation catalyst whose activity has decreased is taken out from the reaction tower, immersed in an aqueous hydrazine solution of each concentration shown in Table 18 below at 60° C. for 1.5 hours under atmospheric pressure, and then washed with water for 1 hour. Next, it is immersed in a 1N aqueous phosphoric acid solution at 80° C. under atmospheric pressure for 1 hour, and then washed with water. The relationship between the concentration of the hydrazine aqueous solution and the degree of catalyst activity recovery is shown in Table 18.

[Table] Example 19 (i) As a result of using the same wastewater treatment as in Example 1,
2% Pd- whose activity index decreased from 100 to 69
The reduction treatment liquid is passed through a wastewater wet oxidation reaction tower filled with a TiO ₂ catalyst under the conditions shown in Table 19 below, and then washed with water and further subjected to pickling treatment. The results are shown as No. 94 in Table 19. (ii) As a result of using the same wastewater treatment as in Example 1,
2% Ru− whose activity index decreased from 100 to 71
The TiO ₂ catalyst is reduced and oxidized in the reaction tower in the same manner as in (i) above. The results are shown as No. 95 in Table 19.

[Table] Example 20 (i) As a result of using the same wastewater treatment as in Example 1,
2% activity index decreased from initial 100 to 70
A hydrolazine aqueous solution is passed through a wastewater wet oxidation reaction tower filled with a Ru-TiO ₂ catalyst under the conditions shown in Table 20 below, followed by washing with water and further pickling treatment with an aqueous hydrochloric acid solution. The result is the 20th
This is shown as No. 96 in the table. (ii) 2% whose catalytic activity has been restored as described in (i) above.
When the Ru-TiO ₂ catalyst is used again in the same wastewater treatment as in Example 1, the activity index drops to 69, so it is reduced and pickled in the same manner as in (i) above. The results are shown as No. 97 in Table 20. (iii) When Catalyst No. 97 obtained in (ii) above is used again for the same wastewater treatment as in Example 1, the activity index decreases to 68. This is reduced and pickled in the same manner as in (i) above. The results are shown as No. 98 in Table 20.

【table】

Claims (1)

[Claims] 1. Iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium, platinum, copper, gold, tungsten, and one or more compounds of these metals that are inert or poorly soluble in water. In a method for regenerating a supported catalyst for wet oxidation of wastewater containing as a catalyst active component, (i) the catalyst is dissolved in an aqueous solution containing at least one acid selected from hydrochloric acid, nitric acid, phosphoric acid, acetic acid and propionic acid; (ii) contacting the catalyst with hydrazine hydrate, formaldehyde, sodium borohydride, lithium aluminum hydride, sodium tartrate, glucose,
A method for regenerating a catalyst, comprising a step of bringing the catalyst into contact with an aqueous solution containing at least one of potassium formate and sodium formate at a temperature of 20°C or higher. 2 Contains one or more of iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium, platinum, copper, gold, tungsten, and water-inactive or sparingly soluble compounds of these metals as catalytic active components. In a method for regenerating a supported catalyst for wet oxidation of wastewater, (i) the catalyst is mixed with hydrazine hydrate, formaldehyde, sodium borohydride, lithium aluminum hydride, sodium tartrate, glucose,
(ii) contacting the catalyst with an aqueous solution containing at least one of potassium formate and sodium formate at a temperature of 20°C or higher; A method for regenerating a catalyst, comprising the step of bringing it into contact with an aqueous solution containing at least one catalyst at a temperature of 40°C or higher. 3 Contains one or more of iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium, platinum, copper, gold, tungsten, and water-inactive or sparingly soluble compounds of these metals as catalytic active components. In a method for regenerating a supported catalyst for wet oxidation of wastewater, (i) the catalyst is added to an aqueous solution containing at least one acid selected from hydrochloric acid, nitric acid, phosphoric acid, acetic acid, and propionic acid at a temperature of 40°C or higher; (ii) contacting the catalyst with at least one of hydrogen and carbon monoxide;
A method for regenerating a catalyst, comprising a step of bringing it into contact with a gas containing seeds at 300 to 500°C. 4 Contains one or more of iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium, platinum, copper, gold, tungsten, and water-inactive or sparingly soluble compounds of these metals as a catalytic active component. A method for regenerating a supported catalyst for wet oxidation of wastewater includes (i) contacting the catalyst with a gas containing at least one of hydrogen and carbon monoxide at 300 to 500°C, and (ii) contacting the catalyst with hydrochloric acid, nitric acid, A method for regenerating a catalyst, comprising the step of bringing the method into contact with an aqueous solution containing at least one acid selected from phosphoric acid, acetic acid, and propionic acid at a temperature of 40°C or higher.