JP2003103170A - Desulfurization agent for removing sulfur oxides in waste gas and method for oxidizing and removing hydrocarbon in waste gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sulfur oxides removing agent having high removing performance to the sulfur oxides in the waste gas. SOLUTION: The desulfurization agent containing alkaline earth metal oxide and iridium is used for removing the sulfur oxides in the waste gas.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a desulfurizing agent for removing sulfur oxides in exhaust gas, and a method for oxidizing and removing hydrocarbons in exhaust gas containing sulfur oxides using the desulfurizing agent.

[0002]

2. Description of the Related Art Sulfur oxides are produced by burning organic sulfur compounds in fuel. For example, combustion exhaust gas generated from petroleum-based fuels such as gasoline, kerosene, and light oil usually contains 1 to several 10 ppm of sulfur oxides. Also,
The natural gas supplied in Japan contains a small amount of organic sulfur compounds in order to make it possible to detect odors in the event of a leak. A slight amount of sulfur oxide is contained. The sulfur oxides contained in the combustion exhaust gas are usually mostly sulfur dioxide and partly sulfur trioxide.

Sulfur oxides are harmful to health in their own right. Further, it is known that sulfur oxides significantly inhibit the activity of the exhaust gas treatment catalyst. For example, Lampert et al. Applied Catalysis B: Environmental
Vol. 14, pp. 211-223 (1997) reports the results of methane oxidation using a palladium catalyst. This document
It has been reported that even in the presence of only 0.1 ppm of sulfur dioxide, the catalytic activity is almost lost within a few hours, and that sulfur oxide has a great influence on the catalytic activity.

Japanese Unexamined Patent Publication No. 2000-117057 discloses the effect of sulfur oxides on the catalytic activity of unburned hydrocarbon oxidation catalysts in exhaust gas, and only 0.05 ppm of sulfur oxides exhibits catalytic activity. It is revealed that it will be greatly reduced. To solve this problem, Japanese Patent Laid-Open No. 2000-117057 discloses a method of previously removing a sulfur component before burning fuel.
Also, two measures have been proposed: a method in which sulfur oxides are removed from the exhaust gas and then the gas to be treated is passed through the hydrocarbon oxidation catalyst.

However, the method (1) cannot remove the sulfur oxide contained in the air added for burning the fuel. At locations along the road, where combustion equipment is nearby, sulfur oxide is an environmental standard value in the air.
It may be contained at a value close to 04 ppm. As described above, considering that even the presence of only 0.05 ppm of sulfur oxides adversely affects the catalytic activity, the method of can not be a sufficient countermeasure.

On the other hand, Japanese Patent Laid-Open No. 2000-117057 exemplifies magnesia and calcia as a desulfurizing agent suitable for the above method, but the effect thereof is not clarified.

In a large-scale facility such as a coal-fired power plant, as a method for removing sulfur oxides in exhaust gas, a wet method of reacting lime water and sulfur oxides to precipitate gypsum and separating and recovering it is a wet method. Normally used. However, since this method is a method in which the exhaust gas is cooled to almost room temperature and then desulfurized, there is a problem that the oxidation reaction cannot be performed when the oxidation reaction is performed after the desulfurization.

In addition, as a flue gas desulfurization method, a method of adsorbing a sulfur compound on activated carbon or the like is known (for example, Japanese Patent Laid-Open No. 7-100329). However, since activated carbon is oxidatively consumed in an oxidizing atmosphere, the upper limit of the treatment temperature is usually about 200 ° C., and the use conditions are largely restricted.

Japanese Unexamined Patent Publication (Kokai) No. 11-319481 discloses a magnesium aluminate-spinel type sulfur oxide storage material, and a storage material to which a platinum group metal, particularly platinum, palladium or rhodium is added is preferable. I am trying. However, its desulfurization performance cannot be said to be high.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the prior art, and mainly involves a sulfur oxide removing agent having a high removal performance for sulfur oxides in exhaust gas. The purpose is to provide.

[0011]

As a result of earnest research, the present inventors have found that a desulfurizing agent containing an inorganic oxide and iridium removes sulfur oxides from exhaust gas containing sulfur oxides such as combustion exhaust gas. Is effective for removing the sulfur oxides from the exhaust gas by contacting the desulfurization agent with the exhaust gas, and then contacting the oxidation catalyst with the exhaust gas, the performance of the catalyst for removing hydrocarbons from the combustion exhaust gas is long. They have found that they can be kept high over time, and have completed the present invention.

That is, the present invention relates to the following desulfurizing agent and a method for oxidizing and removing hydrocarbons in exhaust gas. 1. Desulfurization agent for removing sulfur oxides in exhaust gas containing alkaline earth metal oxides and iridium (hereinafter,
Sometimes referred to as "first desulfurizing agent"). 2. Desulfurizing agent for removing sulfur oxides in exhaust gas containing oxides of at least one metal selected from alkali metals and alkaline earth metals, refractory inorganic oxides, and iridium (hereinafter referred to as "second desulfurizing agent"). Sometimes). 3. Furthermore, the desulfurizing agent according to 1 or 2 above, which contains a platinum group metal. 4. A method for oxidizing and removing hydrocarbons in an exhaust gas containing sulfur oxides and hydrocarbons, wherein the exhaust gas is first contacted with the desulfurizing agent according to any one of the above 1 to 3, and then platinum is applied to the refractory inorganic carrier. A method comprising contacting exhaust gas with a catalyst carrying at least one group metal.

Hereinafter, the "first desulfurizing agent" and the "second desulfurizing agent" may be collectively referred to as the "desulfurizing agent of the present invention".

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The first desulfurizing agent contains an oxide of an alkaline earth metal and iridium.

Examples of the alkaline earth metal oxide contained in the first desulfurizing agent include magnesia, calcia, barium oxide and the like. The alkaline earth metal oxide has a function of storing sulfur oxide as a sulfate.

Iridium contained in the first desulfurizing agent has an effect of oxidizing sulfur dioxide into sulfur trioxide. The amount of iridium supported on the first desulfurizing agent is about 0.05 to 5%, preferably about 0.1 to 1%, based on the total weight of the desulfurizing agent. If the amount is too small, the effect of adding iridium may not be obtained. If the amount is too large, the particle size of iridium may become too large and the supported iridium may not be effectively used, or the effect corresponding to the amount of iridium supported may not be obtained, which may be economically disadvantageous.

The first desulfurizing agent may further contain a platinum group metal such as platinum or rhodium in addition to the above components. The platinum group metal exhibits an effect of enhancing the effect of iridium which oxidizes sulfur dioxide into sulfur trioxide. The content of the platinum group metal in the first desulfurizing agent is usually about 10 to 100% by weight ratio to iridium, more preferably 20 to 50%.
It is about%.

The first desulfurizing agent can be produced by, for example, a method of supporting iridium on an oxide of an alkaline earth metal. As a method of supporting iridium on an oxide of an alkaline earth metal, for example, a method of impregnating an iridium ion-containing solution with an oxide of an alkaline earth metal and firing the oxide in an oxidizing atmosphere can be exemplified. Examples of the iridium ion-containing solution include an iridium chloride aqueous solution and an iridium acetylacetonate organic solvent solution. Examples of the organic solvent include acetone and chloroform. The iridium ion-containing solution is preferably an iridium chloride aqueous solution.

The firing temperature for supporting iridium is
It is usually about 450 to 650 ° C, preferably about 500 to 600 ° C. The firing time is usually about 1 to 20 hours, preferably 3
~ 10 hours. As a gas to be distributed during firing,
Examples thereof include air, air, a gas in which oxygen and an inert gas such as nitrogen are appropriately mixed, and oxygen.

When a platinum group metal is contained if necessary,
For example, an oxide of an alkaline earth metal may carry a platinum group metal simultaneously with or separately from iridium. When iridium and the platinum group metal are loaded separately, either one may be loaded first.

As a method of supporting the platinum group metal, for example, a method of impregnating a platinum group metal ion-containing solution with an oxide of an alkaline earth metal and firing it in an oxidizing atmosphere can be exemplified. Examples of the solute of the platinum group metal ion-containing solution include water-soluble compounds such as nitro complexes of platinum group metals and ammine complexes. The solvent is preferably water.

The calcination temperature for supporting the platinum group metal is
It is usually about 450 to 650 ° C, preferably about 500 to 600 ° C. The firing time is usually about 1 to 20 hours, preferably 3
~ 10 hours. As a gas to be distributed during firing,
Examples thereof include air, air, a gas in which oxygen and an inert gas such as nitrogen are appropriately mixed, and oxygen.

The shape of the first desulfurizing agent is not particularly limited, and may be any shape such as pellet shape and honeycomb shape. In the case of forming a honeycomb shape, for example, a method of forming the first desulfurizing agent into a honeycomb shape; a method of supporting iridium and, if necessary, a platinum group metal on an oxide of a preformed alkaline earth metal; preforming A method in which the honeycomb-shaped refractory carrier is wash-coated with the first desulfurizing agent can be exemplified. Among these, a method of molding a desulfurizing agent into a honeycomb shape; a method of supporting iridium and, if necessary, a platinum group metal on a preformed alkaline earth metal oxide is preferable.

The second desulfurizing agent contains an oxide of at least one metal selected from alkali metals and alkaline earth metals, a refractory inorganic oxide and iridium. Less than,
"Oxide of at least one metal selected from alkali metals and alkaline earth metals" is defined as "alkali metal and /
Or it may be referred to as an oxide of an alkaline earth metal.

The refractory inorganic oxide contained in the second desulfurizing agent can be appropriately selected depending on the temperature of the exhaust gas as the gas to be treated. For example, alumina, silica, titania, zirconia, magnesia, calcia, barium oxide and the like can be exemplified, and alumina, silica, titania, zirconia and the like, which are stable oxides at operating temperatures, are preferably used.

The second desulfurizing agent contains an oxide of at least one metal selected from the group consisting of alkali metals and alkaline earth metals. Oxides of these metals have the function of storing sulfur oxides as sulfates. Examples of the alkali metal include lithium, sodium and potassium. Examples of the alkaline earth metal include magnesium, calcium, barium and the like. Of these, barium is particularly preferable.

The content of the oxide of at least one metal selected from the group consisting of alkali metals and alkaline earth metals in the second desulfurizing agent is a weight ratio with respect to the refractory inorganic oxide, and the alkali metal alone and / or It is usually about 2 to 50%, preferably about 5 to 20% when converted to the alkaline earth metal simple substance. If the content is too high,
Durable inorganic oxides The original strength and moldability may be lost. On the other hand, if it is too small, the desulfurization ability may be insufficient.

Iridium contained in the second desulfurizing agent has an effect of oxidizing sulfur dioxide into sulfur trioxide. The amount of iridium supported on the second desulfurizing agent is about 0.05 to 5%, preferably about 0.1 to 1%, based on the total weight of the desulfurizing agent.
If the amount is too small, the effect of adding iridium may not be obtained. If the amount is too large, the particle size of iridium may become too large and the supported iridium may not be effectively used, or the effect corresponding to the amount of iridium supported may not be obtained, which may be economically disadvantageous.

The second desulfurizing agent may further contain a platinum group metal such as platinum or rhodium in addition to the above components. The platinum group metal exhibits an effect of enhancing the effect of iridium which oxidizes sulfur dioxide into sulfur trioxide. The content of platinum group metal is usually 10 to 100% by weight ratio to iridium.
It is about 40%, more preferably about 20 to 50%.

The second desulfurizing agent is, for example, a method of supporting an oxide of at least one metal selected from the group consisting of alkali metals and alkaline earth metals and iridium on a refractory inorganic oxide; alkali metal and alkali Method for mixing iridium after mixing oxide of at least one metal selected from the group consisting of earth metals and refractory inorganic oxide; refractory inorganic oxide powder supporting iridium and alkali metal and alkali It can be produced by a method of mixing with an oxide of at least one metal selected from the group consisting of earth metals. Among these, a method of supporting an oxide of at least one metal selected from the group consisting of alkali metals and alkaline earth metals and iridium on a refractory inorganic oxide is preferable.

The method of supporting iridium and the oxide of at least one metal selected from the group consisting of alkali metals and alkaline earth metals in the second desulfurizing agent will be described in detail below. The alkali metal and / or alkaline earth metal oxide and iridium may be supported separately or simultaneously. When the alkali metal and / or alkaline earth metal oxide and iridium are separately supported, either one may be supported first.

Examples of the method for supporting an oxide of at least one metal selected from the group consisting of alkali metals and alkaline earth metals on the refractory inorganic oxide include, for example, alkali metal ions and / or alkaline earth metal ions. A method of impregnating the containing solution with a refractory inorganic oxide and firing it in an oxidizing atmosphere such as in air can be exemplified. Examples of the solute of the alkali metal ion- and / or alkaline earth metal ion-containing solution include water-soluble salts such as alkali metal and / or alkaline earth metal nitrates and acetates. The solvent is preferably water, but may be a mixed solvent solution of water and a water-soluble organic solvent such as acetone or ethanol.

The calcining temperature for carrying an alkali metal and / or an alkaline earth metal is usually about 450 to 650 ° C, preferably about 500 to 600 ° C. The firing time is usually about 1 to 20 hours, preferably about 3 to 10 hours. Examples of the gas that is circulated during firing include air, a gas in which air or oxygen and an inert gas such as nitrogen are appropriately mixed, and oxygen.

As a method of supporting iridium on the refractory inorganic oxide, for example, a method of impregnating a iridium ion-containing solution with the refractory inorganic oxide and firing it in an oxidizing atmosphere can be exemplified. Examples of the iridium ion-containing solution include an iridium chloride aqueous solution and an iridium acetylacetonate organic solvent solution. Examples of the organic solvent include acetone and chloroform. The iridium ion-containing solution is preferably an iridium chloride aqueous solution.

The firing temperature when iridium is carried is
It is usually about 450 to 650 ° C, preferably about 500 to 600 ° C. The firing time is usually about 1 to 20 hours, preferably 3
~ 10 hours. As a gas to be distributed during firing,
Examples thereof include air, air, a gas in which oxygen and an inert gas such as nitrogen are appropriately mixed, and oxygen.

When iridium and an oxide of an alkali metal and / or an alkaline earth metal are carried simultaneously, for example, a water-soluble salt of an alkali metal and / or an alkaline earth metal and a water-soluble salt of iridium are used. Examples include a method of impregnating a melted solution with a refractory inorganic oxide and firing the solution in an oxidizing atmosphere such as air. The solvent is preferably water. The firing temperature in this case is usually about 450 to 650 ° C, preferably 500 to 600 ° C.
It is a degree. If the firing temperature is too high, grain growth and volatilization of iridium may proceed, and high desulfurization performance may not be obtained. On the other hand, if the firing temperature is too low, the effect of firing may not be obtained, and sufficient desulfurization performance may not be obtained. The firing time is usually about 1 to 20 hours, preferably 3 to
It takes about 10 hours. Examples of the gas that is circulated during firing include air, a gas in which air or oxygen and an inert gas such as nitrogen are appropriately mixed, and oxygen.

When the second desulfurizing agent contains a platinum group metal as needed, the platinum group metal may be supported on the refractory inorganic oxide, for example. The platinum group metal may be loaded simultaneously with the loading of the oxide of the alkali metal and / or the alkaline earth metal, or may be loaded separately. Also,
The platinum group metal may be loaded simultaneously with the loading of iridium or may be loaded separately. Alternatively, the platinum group metal, alkali metal and / or alkaline earth metal oxide and iridium may be loaded simultaneously. When each component is loaded separately, either component may be loaded first.

As a method of supporting the platinum group metal, for example, a method of impregnating a refractory inorganic oxide in a solution containing a platinum group metal ion and firing it in an oxidizing atmosphere can be exemplified. Examples of the solute of the platinum group metal ion-containing solution include water-soluble compounds such as nitro complexes of platinum group metals and ammine complexes. The solvent is preferably water.

The calcination temperature for supporting the platinum group metal is
It is usually about 450 to 650 ° C, preferably about 500 to 600 ° C. The firing time is usually about 1 to 20 hours, preferably 3
~ 10 hours. As a gas to be distributed during firing,
Examples thereof include air, air, a gas in which oxygen and an inert gas such as nitrogen are appropriately mixed, and oxygen.

The shape of the second desulfurizing agent is not particularly limited, and may be any shape such as pellet shape and honeycomb shape. In the case of forming a honeycomb shape, for example, a method of forming a desulfurizing agent into a honeycomb shape; an alkali metal and / or an alkaline earth metal and iridium, and optionally a platinum group metal, in a preformed refractory inorganic oxide. Method of carrying;
A method in which an alkali metal and / or an alkaline earth metal is supported on a refractory inorganic oxide, and then molded into a honeycomb shape, and further iridium and, if necessary, a platinum group metal are supported thereon; a honeycomb-shaped refractory carrier preformed The method of wash-coating the desulfurizing agent can be exemplified. Among these, a method of forming a desulfurizing agent into a honeycomb shape; a method of supporting an alkali metal and / or an alkaline earth metal and iridium on a preformed refractory inorganic oxide; an alkali metal and / or an alkaline earth metal Is preferably supported on a refractory inorganic oxide, molded into a honeycomb shape, and further supported with iridium.

The desulfurizing agent of the present invention can be used in the "method for oxidizing and removing hydrocarbons in exhaust gas containing sulfur oxides and hydrocarbons" described in detail below.

The method for oxidizing and removing hydrocarbons in exhaust gas according to the present invention is characterized in that it is brought into contact with the first or second desulfurizing agent and then brought into contact with an oxidation catalyst. For example, the exhaust gas is first brought into contact with a desulfurizing agent containing an oxide of an alkaline earth metal and iridium, and then the exhaust gas is brought into contact with a catalyst having at least one platinum group metal supported on a refractory inorganic carrier. . Alternatively, first, an exhaust gas is brought into contact with a desulfurizing agent containing an oxide of at least one element selected from alkali metals and alkaline earth metals, a refractory inorganic oxide and iridium, and then a refractory inorganic carrier is coated with a platinum group metal. The exhaust gas is brought into contact with the catalyst carrying at least one of the above.

If the amount of the desulfurizing agent is too small, the performance cannot be maintained for a long period of time.
HSV) is about 200,000 h ^-1 or less, preferably 5000
It is about 60,000 h ^-1 . Gas hourly space velocity (GHS
The smaller the V), the larger the amount of the desulfurizing agent used, and thus the longer the time that the performance of the desulfurizing agent can be maintained. However, when the GHSV is too low, for example, about 1000 h ⁻¹ or less, there is a possibility that the pressure loss becomes large in addition to the problem that the obtained effect is not worth the cost.

The desulfurizing agent of the present invention has a high sulfur oxide removing performance, but the sulfur oxide removing performance deteriorates at an excessively high temperature. Further, when purifying exhaust gas having a high temperature exceeding 600 ° C., the durability of the catalyst may be deteriorated. Therefore, the exhaust gas temperature in the method of the present invention is usually about 600 ° C or lower, preferably about 550 ° C or lower, and more preferably about 350 to 500 ° C.

As the hydrocarbon oxidation catalyst used in the present invention, a catalyst in which a platinum group metal is supported on a refractory inorganic carrier is used. Examples of the refractory inorganic carrier used for the hydrocarbon oxidation catalyst include alumina and zirconia. Examples of the platinum group metal used for the hydrocarbon oxidation catalyst include palladium, platinum, rhodium and the like. The type of catalyst can be appropriately selected according to the type of hydrocarbon to be treated. Examples of the catalyst having a platinum group metal supported on a refractory inorganic carrier include, for example,
"Catalyst comprising palladium supported on zirconium oxide" and "catalyst comprising palladium and platinum supported on zirconium oxide" disclosed in JP-A-11-319559;
Examples thereof include "catalyst in which platinum and palladium are supported on alumina";"catalyst in which rhodium is supported on alumina";"catalyst in which platinum is supported on alumina" and the like disclosed in 0-117057. When the hydrocarbon to be treated is methane, the catalyst disclosed in JP-A No. 11-319559, the catalyst disclosed in JP-A 2000-117057, and the like can be preferably used.

The amount of platinum group metal supported can be appropriately set according to the type of carrier used, the type of hydrocarbon to be oxidized, and the like. For example, when methane is oxidized using "a catalyst in which platinum and palladium are supported on alumina", the supported amount of palladium is about 1 to 5% by weight ratio to alumina, and the supported amount of platinum is Is
The weight ratio to palladium is about 10 to 100%.

The amount of the catalyst used can be appropriately set according to the type of hydrocarbon to be oxidized, the amount of platinum group metal used, the treatment temperature, and the like. For example, in the case of oxidizing methane using a "catalyst in which platinum and palladium are supported on alumina", the gas hourly space velocity (GHSV) is preferably about 10,000 to 150,000 h ^-1 .

The treatment temperature can be appropriately set depending on the type of catalyst used, the type of hydrocarbon to be treated, and the like. For example, in the case of oxidizing methane using "a catalyst in which platinum and palladium are supported on alumina", the temperature is preferably about 400 to 500 ° C.

The hydrocarbon oxidation catalyst used in the present invention can be produced by a known method. As an example, a method for producing a catalyst in which palladium and / or platinum is supported on a refractory inorganic carrier will be described below. A catalyst in which palladium and / or platinum is supported on a refractory inorganic carrier can be produced by a method of impregnating a palladium and / or platinum ion-containing solution with the refractory inorganic carrier and calcining in an oxidizing atmosphere such as air. it can.
Examples of the solute of the palladium and / or platinum ion-containing solution include nitrates of palladium and platinum, ammine complexes and the like. The solvent is preferably water, but may be a mixed solvent solution of water and a water-soluble organic solvent such as acetone or ethanol. Next, the zirconium oxide support impregnated with the catalytically active component is dried and then calcined in an oxidizing atmosphere such as air to obtain the desired catalyst. Calcination is preferably 450 ° C to 700 ° C, in order to stably obtain high catalytic activity over a long period of time,
More preferably, it is performed at about 500 to 650 ° C. When the calcination temperature is too high, the specific surface area decreases with the progress of grain growth of the supported metal, whereas the catalyst activity may decrease.
If it is too low, the grain growth of palladium or palladium and platinum proceeds during the use of the catalyst, so that the catalytic properties also deteriorate and the stability is impaired.

The hydrocarbon oxidation catalyst used in the present invention can be used in any form. For example, it can be used in any form such as wash-coated on a refractory honeycomb or tablet-molded into pellets according to a conventional method. In the case of washcoating on the refractory honeycomb, the catalyst prepared by the above method may be washcoated in the form of slurry, or the carrier such as zirconium oxide may be washcoated in advance on the refractory honeycomb, A platinum group metal such as palladium, platinum, or rhodium may be supported on the carrier by the same method as described above.

The desulfurizing agent of the present invention exerts a high effect when applied to the oxidation removal of hydrocarbons in exhaust gas containing sulfur oxides and hydrocarbons. The desulfurizing agent of the present invention can be applied not only to the oxidation removal of hydrocarbons, but also to the removal of nitrogen oxides in exhaust gas. That is, first, the gas to be treated is brought into contact with the desulfurizing agent of the present invention, and then brought into contact with the nitrogen oxide removing catalyst, whereby the nitrogen oxide can be removed efficiently.
As the nitrogen oxide removing catalyst, for example, a catalyst in which silver is supported on alumina can be exemplified.

The desulfurizing agent of the present invention can be regenerated by a method such as a method of heat treatment in an oxidizing atmosphere such as air, a method of heat treatment in a reducing atmosphere and the like. When the heat treatment is performed in an oxidizing atmosphere such as air, the treatment temperature is 100 to 150 ° C higher than the usage conditions (for example, 500 to 650 ° C), and the treatment time is usually
It takes about 5 to 120 minutes. When the heat treatment is performed in a reducing atmosphere, the treatment temperature is usually about 400 to 600 ° C., and the treatment time is usually about 5 to 120 minutes. In either case, if the treatment temperature is too high or the treatment time is too long, there is a possibility that the agglomeration of iridium will proceed and the desulfurization performance will decrease. On the other hand, if the treatment temperature is too low or the treatment time is too short, the regeneration effect of desulfurization performance may be insufficient.

[0053]

EFFECTS OF THE INVENTION The desulfurizing agent of the present invention exhibits high removal performance for sulfur oxides contained in exhaust gas. Therefore, if the desulfurizing agent of the present invention is installed in the upstream of a catalyst poisoned by sulfur oxides such as a catalyst for removing hydrocarbon oxidation, the catalyst performance can be kept high for a long period of time.

[0054]

EXAMPLES Examples of the present invention will be given below together with comparative examples.
The present invention will be described more specifically. The present invention is not limited to the examples below.

Example 1 (Preparation of 10% Ba-0.2% Ir / alumina) Alumina (SA6276 manufactured by Coral Pan Norton Co., USA) was crushed to have a particle size of 1-2 mm. Barium nitrate and iridium chloride were dissolved in water to prepare 10 ml of an aqueous solution containing 0.7 g of barium and 14 mg of iridium. After soaking the above-mentioned alumina 7 g in this solution for 15 hours, evaporate it to dryness, and burn in air at 600 ° C for 6 hours to obtain 10% Ba-0.2%
Ir / alumina was prepared.

Example 2 (Preparation of 10% Ba-0.2% Ir-0.1% Pt / alumina) Barium nitrate, iridium chloride and dinitrodiammine platinum were dissolved in water to give 1 g of barium and 20 mg of iridium. 12 ml of an aqueous solution containing 10 mg of platinum
Was prepared. 10 g of the same alumina used in Example 1 was immersed in this solution for 15 hours and then evaporated to dryness,
10% Ba-0.2% Ir-0.1% P after firing in air at 600 ℃ for 6 hours
A t / alumina was prepared.

Comparative Example 1 (Preparation of 10% Ba / alumina) Barium nitrate was dissolved in water to prepare 10 ml of an aqueous solution containing 0.7 g of barium, and the same alumina 7 as used in Example 1 was prepared. After soaking g for 15 hours,
It was evaporated to dryness and calcined in air at 600 ° C. for 6 hours to prepare 10% Ba / alumina.

Comparative Example 2 (Preparation of 10% Ba-0.2% Pt / alumina) Barium nitrate and tetraammine platinum nitrate were dissolved in water to prepare 10 ml of an aqueous solution containing 0.7 g of barium and 14 mg of platinum. did. 7 g of the same alumina used in Example 1 was immersed in this solution for 15 hours, then evaporated to dryness and calcined in air at 600 ° C. for 6 hours to obtain 10% B.
A-0.2% Pt / alumina was prepared.

Example 3 (Performance test) Palladium nitrate and tetraammine platinum nitrate were dissolved in water to give 0.3 g of palladium and 75 mg of platinum.
25 ml of an aqueous solution containing and was prepared. 15 g of the same alumina used in Example 1 was immersed in this solution for 15 hours, evaporated to dryness, and calcined in air at 550 ° C. for 6 hours to prepare a 2% Pd-0.5% Pt / alumina catalyst. did.

2% Pd-0.5% Pt / prepared as described above
Alumina catalyst (1.5 ml) was filled in a reaction tube, and 10% Ba-0.2% Ir / alumina 1.5 prepared in Example 1 was provided upstream of the reaction tube.
ml was charged. Methane 1000 ppm, oxygen
A gas having a composition of 10%, steam 10%, carbon dioxide 6%, sulfur dioxide 3 ppm, and the balance nitrogen was circulated under the condition of a volume of 2 liters per minute in a standard state. Reaction tube temperature 450
The temperature was kept at 0 ° C and the change with time of the methane conversion rate was measured. The gas composition before and after the reaction layer was measured by a gas chromatograph having a hydrogen flame ionization detector. Here, the methane conversion rate is a value obtained by the following formula.

[0061]

[Formula 1]

FIG. 1 shows the change over time in the methane conversion rate. It took 20 hours for the methane conversion to drop to 50%.

Comparative Example 3 A test was conducted in the same manner as in Example 3 except that the reaction tube was not filled with 10% Ba-0.2% Ir / alumina. The change over time in the methane conversion rate is shown in FIG. It took 4 hours for the methane conversion to drop to 50%.

Comparative Example 4 A test was conducted in the same manner as in Example 3 except that 10% Ba / alumina was used instead of 10% Ba-0.2% Ir / alumina. The change over time in the methane conversion rate is shown in FIG. It took 10 hours for the methane conversion to drop to 50%.

Comparative Example 5 A test was conducted in the same manner as in Example 3 except that 10% Ba-0.2% Pt / alumina was filled instead of 10% Ba-0.2% Ir / alumina. The change over time in the methane conversion rate is shown in FIG. It took 10 hours for the methane conversion to drop to 50%.

Example 4 Instead of 10% Ba-0.2% Ir / alumina, 10% Ba-0.2% Ir-0.
The test was conducted in the same manner as in Example 3 except that 1% Pt / alumina was filled. The change over time in the methane conversion rate is shown in FIG. It took 24 hours for the methane conversion to drop to 50%.

Comparative Example 6 A test was conducted in the same manner as in Comparative Example 3 except that sulfur dioxide was removed from the gas to be treated. The change over time in the methane conversion rate is shown in FIG. The methane conversion after 30 hours was 63%.

Example 5 A test was conducted in the same manner as in Example 3 except that the filling amount of 10% Ba-0.2% Ir-0.1% Pt / alumina was 3 ml. The change over time in the methane conversion rate is shown in FIG. The methane conversion rate after 30 hours was 65%. Compared with the results of Comparative Example 6, the higher methane conversion was due to 10% Ba-0.2 used as the desulfurizing agent.
% Ir-0.1% Pt / alumina itself suggests that it has some methane oxidation performance.

The results of the above Examples and Comparative Examples are summarized in Table 1. As is clear from the comparison between Comparative Example 6 and Comparative Example 3, the performance of the methane oxidation catalyst drops sharply in the presence of sulfur oxides. A desulfurizing agent containing only an alkaline earth metal such as barium has satisfactory desulfurization performance but is not satisfactory (Comparative Example 4), and the methane conversion rate is 50%.
The time to drop to% was only extended from 4 hours to 10 hours. Even if a desulfurizing agent in which platinum was added in addition to barium was used, the desulfurization effect was almost the same as in the case of only barium (Comparative Example 4) (Comparative Example 5).

On the other hand, when a desulfurizing agent containing iridium in addition to barium was used, it took 20 hours for the methane conversion rate to decrease to 50% (Example 3), and the desulfurizing agent of the present invention showed high performance. It became clear to have. The desulfurizing agent of the present invention may further contain platinum, barium,
When a desulfurizing agent containing iridium and platinum was used (Example 4), it took as long as 24 hours to reduce the methane conversion rate to 50%. Furthermore, when the amount of the desulfurizing agent was increased (Example 5), the methane conversion rate was equal to or higher than that when the treated gas containing no sulfur oxide was used (Comparative Example 6) even after 30 hours. .

From the above results, it was shown that by applying the desulfurizing agent of the present invention, the activity of the methane oxidation catalyst was not substantially inhibited by the sulfur oxide.

[0072]

[Table 1]

[Brief description of drawings]

FIG. 1 shows changes with time in methane conversion rate in performance tests (Examples 3 to 5 and Comparative Examples 3 to 6).

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // B01D 53/34 ZAB B01D 53/34 124Z 53/50 ZAB 53/81 F term (reference) 3G091 GB00W GB02W GB03W GB06W 4D002 AA02 BA03 DA01 DA04 DA11 EA01 4D048 AA02 AA18 AB01 BA01Y BA02Y BA03X BA06Y BA07Y BA08Y BA14Y BA15X BA30X BA33X BA33Y BA41X BB01 BB02 CC32 CC46 4G066 AA12C AA13B AA16B AA17B AA28D CA23 DA02 4G069 AA03 BA01A BA01B BA02A BA04A BA05A BA06A BB02A BB02B BB04A BC01A BC02A BC03A BC04A BC08A BC09A BC10A BC13B BC69A BC71A BC72B BC74A BC74B BC75A BC75B CA02 CA07 CA12 CA15 EA02Y EA18 EA19

Claims (4)

[Claims] 1. A desulfurizing agent for removing sulfur oxides in exhaust gas containing an alkaline earth metal oxide and iridium. 2. A desulfurizing agent for removing sulfur oxides in exhaust gas containing oxides of at least one metal selected from alkali metals and alkaline earth metals, refractory inorganic oxides and iridium. 3. The method according to claim 1, further comprising a platinum group metal.
The desulfurizing agent described in 1. 4. A method for oxidizing and removing hydrocarbons in exhaust gas containing sulfur oxides and hydrocarbons, which comprises first to claim
The exhaust gas is brought into contact with the desulfurizing agent according to any one of 1 to 3, and then the exhaust gas is brought into contact with a catalyst in which at least one platinum group metal is supported on a refractory inorganic carrier.