JPS58114732A - Regenerating method of catalyst - Google Patents

Abstract

PURPOSE:To recover the catalytic activity of catalysts used for wet oxidation treatments of waste water contg. COD components, suspended solids, ammonia, etc. and to regenerated said catalysts by pickling the catalysts with aq. solns. contg. specific inorg. acids or org. acids. CONSTITUTION:Catalysts contg. metals such as Fe, Co, Ni, Ru, Rh, Ir or the like or 1 or >=2 kinds compds. consisting of oxides, chlorides or sulfides insoluble or hard to dissolve in water of these metals are used as catalysts for wet oxidation treatments of waste water contg. COD components, suspended solids, ammonia, etc. In order to recover and regenerate the activity of such catalysts, the catalysts are dipped for >=15min in aq. solns. at >=40 deg.C contg. at least 1 kind among hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid and other inorg. acids as well as acetic acid, tartaric acid, citric acid and other org. acids (except formic acid and oxalic acid) at 0.1-5.0 normal noncn., whereby the catalytic acitivity is recovered and the catalysts are regenerated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for regenerating catalysts used in the wet oxidation of wastewater.

As for the treatment of wastewater containing chemical oxygen demand substances (hereinafter referred to as COD components), suspended solids, and even ammonia in some cases, as a result of many years of research into various treatment methods, we have found that the types of catalysts, It is important to note that the concentration and supply amount of oxygen used in wet oxidation, preliminary pill preparation of wastewater, supply of alkaline substances during wet oxidation reaction, etc. greatly affect treatment efficiency, corrosion of equipment used, life of catalyst, etc. A patent application has already been filed based on the headline and mosquito findings (
Patent Application No. 1id51-95507, Patent Application No. 1102-1982
No. 57, Japanese Patent Application No. 165168/1984, etc.). In the first method, at least one of metals such as iron, cobalt, nickel, ruthenium, rhodium, iridium, platinum, gold, and tungsten, as well as water-insoluble or sparingly soluble compounds of these metals, may be used as is or alumina. It can be used as a catalyst when supported on a carrier such as silica, silica-alumina, titania, zirconia, or activated carbon.Such catalysts (hereinafter simply referred to as wastewater oxidation catalysts) are used in large quantities in wastewater treatment. The present inventor thought that known catalyst regeneration methods in other fields could be applied to the regeneration of wastewater oxidation catalysts, and conducted various experiments. It has been found that the conversion of known methods is not necessarily effective. For example, when regenerating a waste water oxidation catalyst using a known regenerating agent such as hydrogen, steam, or oxygen, the substances attached to the catalyst surface are Although the catalyst is successfully removed, the recovery of the catalyst activity itself 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 found that treatment of the oxidation catalyst with an aqueous solution containing at least one of an inorganic acid and an organic acid is extremely effective. .

That is, the present invention uses iron, cobalt, nickel, ruthenium, rhodium, iridium, platinum, steel, gold, tungsten, and one or more water-insoluble or sparingly soluble compounds of these metals as a catalytically active component. A method for regenerating a supported catalyst for wet oxidation of wastewater, the method comprising bringing the catalyst into contact with an aqueous solution containing at least one of an inorganic acid and an organic acid (excluding formic acid and Sierra iron). .

Generally, waste water oxidation catalyst is used at high temperature (100~870℃)
When used in wet oxidation of wastewater, precipitation, sedimentation or layering of COD components and suspended substances in wastewater, precipitation of soluble inorganic substances, and chemically active substances contained in wastewater or generated by decomposition. The activity of the catalyst gradually decreases due to factors such as changes in the chemical and physical properties of the surface of the catalyst metal, in addition to chemical attack of the catalyst metal by oxidation. 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 the causes of the former that can be recognized from the outside are It is assumed that this is a factor that reduces the activity of a catalyst that is equivalent to or more important than that of the catalyst. However, according to the method of the present invention, these factors that reduce the catalyst activity are generally eliminated, so that the wastewater oxidation catalyst is The activity is recovered to the extent that it can be reused, and depending on the processing conditions, the K can be recovered to a level that is almost the same as that of a new catalyst.

The catalyst regenerated by the method of the present invention contains iron, cobalt, nickel, ruthenium, rhodium, iridium, platinum, steel, gold, and tungsten as catalytic active components, and one type of water-insoluble or sparingly soluble compounds thereof. It also includes two or more types. Examples of water-insoluble or dissolvable compounds include (I) iron sesquioxide, triiron tetroxide, -cobalt oxide, -
Nickel oxide, ruthenium dioxide, rhodium sesquioxide,
Examples include oxides such as iridium dioxide, second steel oxide, and tungsten dioxide; (11) chlorides such as ruthenium chloride and platinum chloride; and (lIi) sulfides such as ruthenium sulfide and rhodium sulfide.

The waste water oxidation catalyst regeneration treatment agent used in the present invention is:
They are inorganic acids and organic acids, and are used in the form of an aqueous solution containing at least one of these acids.

Inorganic acids include hydrochloric acid, nitric acid, nitrous acid, sulfuric acid, sulfurous acid,
Examples include phosphoric acid, carbonic acid, boric acid, hypochlorous acid, chloric acid, bromic acid, etc.; (2) aliphatic carboxylic acids such as succinic acid, malonic acid, fumaric acid, and maleic acid; <++) phenols; and (2) aromatic carboxylic acids such as benzoic acid, phthalate, and salicylic acid. The concentration of the regeneration treatment agent in the aqueous solution may vary depending on the amount of supported catalyst metal, the degree of catalyst activity reduction, the temperature during regeneration treatment, etc., but is usually in the range of 0.1 to 6.0 normal, and is preferably shall be 0.25 to 2.0 normal strength. If the concentration is too low, the regeneration effect will not be sufficient; on the other hand, as the concentration increases, the regeneration effect will gradually improve; however, further improvement in the stuttering regeneration effect beyond the 5 provisions is morally acceptable. There is no.

The regeneration treatment is carried out by leaving the waste water oxidation catalyst to be regenerated immersed in an aqueous solution of a regeneration treatment agent, or by stirring it in the aqueous solution. Regeneration treatment can be carried out by removing the catalyst from the reaction tower that performs wet oxidation treatment of wastewater and placing it in a separate treatment tank, or by storing the catalyst in the wet oxidation reaction tower and returning it to the reaction tower in good condition for regeneration treatment. The aqueous solution of the agent may be continuously distributed. The treatment conditions are usually at a temperature of 40°C or higher, more preferably at 60°C or higher, and for a time of usually 16 minutes or more, more preferably 80 minutes or more.

The treatment temperature and treatment time are determined by the degree of catalyst activity reduction, the type of catalyst, the required degree of catalyst activity recovery, the type and concentration of the regenerating agent, and are not necessarily limited. The pressure in carrying out the method of the present invention is atmospheric pressure, and there is no particular need for pressurization, but there is no disadvantage in carrying out the process under pressure.

The waste water oxidation catalyst that has undergone the regeneration treatment according to the present invention has its t
Alternatively, if necessary, it can be reused after washing with water or after washing and drying.

In addition, if the catalytic activity is likely to decrease and the catalytic activity is not sufficiently restored by one regeneration treatment, it is preferable to repeat the regeneration treatment of the present invention under equal pressure.

According to the method of the present invention, the following remarkable effects are achieved.

(1) Since the factors that reduce catalyst activity are largely eliminated, the activity of the wastewater oxidation catalyst is recovered to the extent that it can be reused.

(11) Depending on the regeneration treatment conditions, the catalyst activity after regeneration can be recovered to a degree that is almost equal to that of the new catalyst.

By reusing the QiD after regeneration, the waste water oxidation catalyst whose activity has decreased can be further regenerated repeatedly, and its activity can be made close to that of the new catalyst, thereby significantly increasing the overall life of the catalyst. It became possible.

Since the cost of the catalyst required for 1-silicon wastewater treatment is reduced, the wastewater treatment cost is also reduced.

(V) When using two or more reaction towers for wastewater treatment, the wastewater oxidation catalyst in either of the anti-hazardous towers can be regenerated alternately without stopping the wastewater treatment.
Labor such as removing and refilling the catalyst becomes unnecessary.

Example 1 Gas liquid (COD6000p) generated in a coke oven
pm, total nitrogen amount 7% 3 amount soooppm = total nitrogen amount + 00
0 ppm) with a caustic soda solution to a pH of about 10 and fed to the bottom of the cylindrical reaction tower at a space velocity of 1.0/hr (based on the empty column). Note that the gas liquids treated in Examples 1 to 8 originally contained iron, calcium, and magnesium in a total amount of 16 ppm (in order to more clearly demonstrate the effects of the present invention, the total amount was further increased to 1500 ppm). When these compounds are added, the mass velocity of the liquid is 8.0 tons/-.hr. On the other hand, air has a space velocity of 6
5 hours (based on the empty column, converted to standard conditions) is supplied to the lower part of the reaction tower. The cylindrical reaction tower was filled with spherical catalysts having a diameter of 5 ms and having the composition shown in Table 1 below. still,
In Table 41, for example, Ir-Ti01 means that 1% by weight of iridium was supported on the titania support.

The temperature inside the reaction tower is kept at 250°C and the pressure cuff is maintained at 0t/- OK, and the above gas liquid is wet-oxidized for too long while supplying a caustic soda aqueous solution so that the pH of the liquid after wet oxidation is approximately 7. From K, the activity index of the catalyst is
The activity decreases as shown in Table 41. The catalyst whose activity has decreased is taken out from the reaction tower and left immersed in a normal phosphoric acid aqueous solution (80°C) for 1 hour under atmospheric pressure. After being regenerated, it is washed with water for 1 hour. . The regenerated catalysts were used in the same wastewater treatment as above, and the results are shown in Table 1.

In addition, in the specification of this application, the activity index refers to the ammonia removal rate of 1 when wastewater is wet-breeded using a new catalyst.
00, it refers to the ammonia removal rate of each catalyst when wastewater is subjected to wet oxidation treatment using each catalyst under the same conditions. Since the COD removal rate also shows the same tendency as the ammonia removal rate, it is not particularly displayed.

Table 1 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.

Example 2 A catalyst whose activity had decreased due to the same wastewater treatment as in Example 1 was taken out of the reaction tower and treated with a 1N aqueous hydrochloric acid solution (80°C).
) for 1 hour under atmospheric pressure, and then washed with water for 1 hour. The reproduction results are shown in Table 2.

Table 2 Example 8 The catalyst whose activity had decreased by the same wastewater treatment operation as in Example 1 was taken out from the reaction tower and treated with a normal nitric acid aqueous solution (70°C
) for 1 hour under atmospheric pressure, and then washed with water for 1 hour.

Changes in catalyst activity before and after regeneration are shown in Table 8. Table 8 Example 4 In the same manner as in Example 1, the 2-dominant Ru-Ti catalyst whose activity index decreased from 100 to 71 as a result of being used for wastewater treatment was taken out of the reaction tower and treated under the conditions shown in Table 4 below. Perform immersion regeneration treatment. The activity of the catalyst after regeneration is as shown in Table 4.

Example 6 When used in the same wastewater treatment as in Example 1, the activity index was 1.
2% Rh-TiO decreased from 00 to 72,
The catalyst is immersed and regenerated under the conditions shown in Table 6 below.

The degree of recovery of catalyst activity by regeneration treatment is as shown in Table 1s6.

Table 5 Example 6 A 2% Ru-Ti01 catalyst whose activity index decreased from 100 to 71 as a result of use in the same wastewater treatment as in Example 1 was added to an aqueous solution of hydrochloric acid (70°C) at a similar concentration at atmospheric pressure. After soaking for 1 hour, wash with water for 1 hour. The relationship between the hydrochloric acid concentration and the degree of catalyst activity recovery is shown in Table 6 below.

Table 116 Example 7 A 0.5 N phosphoric acid aqueous solution was added to a reaction tower filled with a 2*Ru-Ti0z catalyst whose activity index decreased from 100 to 72 as a result of use in the same wastewater treatment as in Example 1. It is allowed to flow continuously for 1 hour under the conditions of a temperature of 80° C. and a space velocity of 0.99/hr. Next, the catalyst in the reaction tower that has undergone regeneration treatment is washed with running water at a space velocity of 2.0 3/hr (water/catalyst) for 1 hour. In this way, the activity index of the regenerated catalyst (425) was recovered to 86.

Example 8 (a) 2% Ru-Ti0 whose activity index decreased from 100 to 70 as a result of use in the same wastewater treatment as in Example 1.
．． A 1N aqueous hydrochloric acid solution at 80°C was continuously passed through the reaction tower filled with the catalyst at a space velocity of 0.991/hr for 1 hour, and then flowing water at a space velocity of 2.0/hr (water/catalyst) was further passed for 1 hour. Wash with water. Thus, the activity index of the regenerated catalyst (A26) was restored to 90.

(b) When the above regenerated catalyst A26 is used in the same wastewater treatment as in Example 1, the activity index decreases to 69, so the regeneration treatment and water washing are carried out in the same manner as in 0) above. Thus, the activity index of the regenerated catalyst (Ban 27) is 8.
91 and 1g was 141 shi.

e→ The above regenerated catalyst! 27 When used again for the same wastewater treatment as in Example 1, the activity index decreased to 69.
When the catalyst was regenerated and washed with water in the same manner as in step (i) above, the activity of the regenerated catalyst (A''28) was again restored to 89.

From the results of (a), (b), and (c) above, it is clear that according to the method of the present invention, it is possible to repeatedly regenerate the waste water oxidation catalyst, and the overall life of the catalyst can be significantly increased. it is obvious.

(that's all)

Claims (1)

[Claims] ■ Iron, cobalt, nickel, ruthenium, rhodium,
In a method for regenerating a supported catalyst for wet oxidation of wastewater, the catalyst is an inorganic A method for regenerating a tentacle, which comprises contacting with an aqueous solution containing at least one of an acid and an organic acid (excluding formic acid and oxalic acid).