JPS58219942A - Regeneration of catalyst - Google Patents

Abstract

PURPOSE:To carry out the regeneration of a catalyst simply and easily, by a method wherein the used catalyst used according to a catalytic deodorizing method using ozone is washed by an aqueous ammonia solution and, after washing, the washed catalyst is dried to be baked at a high temp. in an inert gas atmosphere. CONSTITUTION:As the catalyst used in strongly oxidizing a malodorous gas by using ozone to deodorize the same, a catalyst obtained by supporting oxide of ametal such as Mn, Co, V, Cr, Fe, Ni, Cu, Ag or Zn by the surface of granular activated carbon or carbon fiber is used. When the catalytic activity thereof is lowered during long-term use, this used catalyst is washed by an aqueous ammonia solution with pH of 10-11 to wash off and remove sulfuric acid or sulfate of catalytic metal adhered to the surface of the catalyst. In the next step, after the washed catalyst is washed by water and dried, catalytic capacity is restored by baking the dried catalyst at 200-300 deg.C in an inert atmosphere to enable the regeneration and the reuse thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for easily regenerating a spent catalyst used in a so-called ozone catalyst deodorization method in which malodorous gas is deodorized using ozone in the presence of a catalyst.

One method for removing bad odors is the ozone catalytic deodorization method, which utilizes the strong oxidizing effect of ozone to oxidize malodorous gas components to odorless components.

Already filed by the inventors (Japanese Patent Application No. 53-26628)
In the ozone catalyst deodorization method, in order to promote the oxidation reaction between ozone and malodorous gas components, a catalyst is used, for example, which uses activated carbon as a carrier and supports an active metal such as manganese or cobalt on the surface of the carrier. ing.

The main conditions that this catalyst must meet are: ■High catalytic action; ■Long catalyst life; in particular, ■
Factors that control the catalyst life include: ■Mist and dust contained in the gas to be treated (e.g., Pb, Zn,
Sn, As, Na.

(consisting of elements such as K, P, S, at),
■ Accumulation of reaction products, ■ Thermal changes due to overheating, etc.

The ozone deodorization method is mainly aimed at treating malodorous gases generated from sewage treatment facilities, human waste treatment facilities, and similar facilities, so the target malodorous gas components are sulfur such as hydrogen sulfide and methyl mercaptan. The main compounds are

For example, the reaction between ozone and hydrogen sulfide mainly proceeds as shown in the equation below, and the final products are sulfur (S) and sulfur dioxide gas (
SO2) and sulfuric acid (H2SO4).

H2S + 03 H2O+ 8 +02 (1
) H2S -1-o3- H2O+so2 (
2128-) o3 ←2SO2+ O(3)BOz
+03-. 80s +02 (4180
3+H20→H2So4 (51
This final product accumulates on the surface of the catalyst, impairs the catalyst function, and becomes a factor that reduces the catalyst life.

For example, in the case of sulfuric acid, it combines with the above-mentioned catalytically active metal to form a metal sulfate, causing the active metal to lose its function.

The present invention regenerates this used catalyst that has lost its catalytic function,
This was done to reduce catalyst costs and increase economic benefits.

That is, in the present invention, after washing a used catalyst used in a catalytic deodorization method using ozone with an ammonia aqueous solution,
The present invention relates to a catalyst regeneration method characterized by washing with water, drying, and then firing in an inert gas atmosphere at 200 to 300°C.

The method of the present invention will be explained in detail below.

First, the used catalyst used in the ozone catalyst deodorization method is washed with an ammonia aqueous solution.

The ammonia aqueous solution acts on sulfuric acid and active metal sulfates in the catalyst, removes them from the catalyst surface, and transfers them to the aqueous solution side.

In this case, if the active metal is manganese oxide, the expected reaction is as follows.

H2SO4+2NH40H→(NH4)2804 +2
H20fi1MnSO4+ 2NH40H-4Mn(O
H) 2 + (NH4) 1304 (21 Note that the ammonia aqueous solution has a pH of 1 to enhance the above-mentioned cleaning effect.
The pH is 0 to 11, preferably -10 to 11.

The catalyst washed with the ammonia aqueous solution is then washed with water to wash out the ammonia aqueous solution and reaction products (eg, (NH4)2So, as described above) remaining in the catalyst.

After that, it is drained, dried, and fired.

This firing is performed under an inert gas atmosphere at 200 to 600°C.

The firing temperature of 2,00 to 600°C was determined from the experimental results of the present inventors shown in Figure 1, and as is clear from the figure, the firing temperature of 200 to 600°C was If it is played effectively.

The reason why the firing atmosphere is an inert gas atmosphere is because if the catalyst carrier is activated carbon or other carbonaceous material, there is a risk of ignition in an air atmosphere.

In addition, since water vapor is generated during firing, the
It is desirable to carry out firing while flowing an inert gas heated to 0° C. to purge this water vapor and at the same time improve the heat transfer effect.

By this calcination, for example, Mn(OH)2 generated in the ammonia aqueous solution washing step described above is thermally decomposed and becomes an oxide (MnOx, x = 1.5-2), and the catalyst is regenerated. Ru.

The method of the present invention described in detail above is a method of depositing vanadium, chromium, manganese, iron, cobalt, nickel, copper, silver, zinc, etc. on a catalyst carrier made of, for example, granular/crushed or powdered activated carbon, graphite, carbon fiber, etc. The catalyst supports one or more metal oxides, and can be applied to spent catalysts used in ozone catalytic deodorization methods.

Example Granulated activated carbon (coconut charcoal, 4 to 6 meshes, specific surface area 1
This catalyst has manganese oxide supported on it and has been used continuously for about 8,000 hours to deodorize the highly concentrated odor of 2,000 m"/hr generated from the sludge treatment tank of a sewage treatment facility. The spent catalyst 50y, which has been regenerated in the following manner, is placed under a bee force of 500 mA, stirred at room temperature while adding an ammonia aqueous solution, and when the ammonia aqueous solution is successively added, the pH of the liquid becomes 9. ~1
3, but cleaning was promoted by keeping the pH at 10-11.

After finishing washing with ammonia aqueous solution, the catalyst was taken out and washing with water was repeated.

When the pH of the washing wastewater reached 7 to 8, the catalyst was taken out, drained, and then dried in a dryer at 110°C for 2 to 5 hours.

Next, put 40 to 50 y of catalyst into an electrically heated firing furnace,
Heat the inside of the furnace to 200 to 300°C and inject heated nitrogen gas (
The catalyst was calcined while flowing a temperature of 1 to 104/lIn1n (200 to 600°C).

The deodorizing effect of the catalyst after the above regeneration operation was examined by a reaction tube test as follows.

Fill the reaction tube with 20p of catalyst, and add 11)9m% of hydrogen sulfide.
Simulated gas containing 5 ppm of ozone was supplied at 5 t/min.
(20°C), and the hydrogen sulfide and ozone concentrations before and after the catalyst layer were measured.

The results are shown in Table 1 in comparison with the results using the spent catalyst before regeneration.

Table 1 Hydrogen sulfide (ppm) Ozone (ppm) Before catalyst After catalyst Before catalyst After catalyst Spent catalyst 1.0 0.2 3.0
06 Regenerated catalyst 1.0 0.01 or less 3.0
0.05 or less As is clear from Table 1, the catalyst regenerated by the method of the present invention exhibits a good deodorizing function and can be used again in the ozone catalyst deodorizing method.

[Brief explanation of the drawing]

FIG. 1 is a chart showing the relationship between the firing temperature during firing and the catalyst regeneration rate in the method of the present invention. Sub-agents 1) Meifuku agent Ryo Hagiwara -

Claims (1)

[Claims] The spent catalyst used in the catalytic deodorization method using ozone is
A method for regenerating a catalyst, which comprises washing with an ammonia aqueous solution, washing with water, drying, and then firing in an inert gas atmosphere at 200 to 300°C.