JPH07136461A - Method for selectively removing oxygen containing compound from mixed gas containing oxygen contained compound, aromatic compound, and oxygen - Google Patents

Abstract

PURPOSE:To provide a method for removing oxygen containing compounds by the selective oxidation at low temperatures by contacting mixed gas such as exhaust gas containing oxygen contained compounds and aromatic compounds with a catalyst. CONSTITUTION:Mixed gas such as exhaust gas containing oxygen contained compounds and aromatic compounds is treated with a catalyst in which one or more kinds of metal selected from a group consisting of platinum, palladium, and rhodium are mounted on a carrier having a regular porous structure so that the oxygen contained compounds are oxidized selectively to be removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for selectively oxidizing and removing an oxygen-containing compound contained in a mixed gas containing an oxygen-containing compound, an aromatic compound and oxygen at a low temperature, the exhaust gas containing the aromatic compound. It is advantageously applied as a method for removing the methanol component from the exhaust gas of an automobile fueled by a methanol / gasoline mixture.

[0002]

2. Description of the Related Art Since oxygen-containing compounds (alcohols, aldehydes, ethers, esters, etc.) are harmful to the body, development of a method for completely oxidizing and removing these oxygen-containing compounds in a mixed gas such as exhaust gas even at a low temperature. Is desired.

As a method for treating a gas containing an oxygen-containing compound, there are (a) a method of applying an ordinary noble metal catalyst and bringing it into contact with a gas, and (b) a method of heating the catalyst to enhance its oxidizing ability. Is generally known.

[0004]

[Problems to be Solved by the Invention] However, (a)
In this method, when the temperature of the oxygen-containing compound removing catalyst is low, the coexisting aromatic compound strongly suppresses the oxidation activity, so that the purification performance of the catalyst is deteriorated, and the unburned oxygen-containing compound or the partial oxidation is generated. Hazardous substances such as oxygen compounds are released.

In addition, the method (b) has the drawbacks that equipment for heating the catalyst must be installed and the entire apparatus is enlarged and energy is lost.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for efficiently removing an oxygen-containing compound component at a low temperature even in the presence of an aromatic compound.

[0007]

[Means for Solving the Problem] The present inventors have examined the oxidation of oxygen-containing compounds by platinum catalysts in the presence of various hydrocarbon catalysts, and have found that the reason why combustion of oxygen-containing compounds is prevented when the temperature of the catalyst is low It has been found that the substance that becomes is an aromatic compound (benzene, toluene, xylene, etc.) contained in the exhaust gas. Furthermore, as a result of extensive studies on the oxidation of oxygen-containing compounds in the coexistence of aromatic compounds, a catalyst in which a precious metal is supported on a carrier having regular pores such as zeolite is hardly affected by the coexisting aromatic compounds. It was found that the oxygen-containing compound was preferentially oxidized, and the present invention was completed based on this finding.

That is, in the method for selectively removing an oxygen-containing compound of the present invention, a mixed gas containing an oxygen-containing compound and an aromatic compound is contacted with a catalyst in which a precious metal is supported on a carrier having regular pores in the presence of oxygen. It is characterized by

In the method of the present invention, the noble metal supported on the catalyst may be one or more metals selected from platinum, palladium and rhodium. For the carrier, mordenite, ZSM-5, Y-type zeolite, X-type zeolite,
Various carriers having regular pores such as L-type zeolite and silicalite can be used. The average pore size of the carrier is 4 to 15 angstroms, preferably 4 to 10 angstroms. Exhaust gas to be treated must contain oxygen in excess of the amount required to oxidize the oxygen-containing compound to be converted and convert it into carbon dioxide. 1-1000 times, preferably 5-10
It may be 0 times. There are no particular restrictions on the concentrations of oxygen-containing compounds and aromatic compounds in the exhaust gas. The space velocity (GHSV) for introducing the exhaust gas into the catalyst layer is not particularly limited because it depends on the conditions such as the reaction temperature and the required removal rate of the oxygen-containing compound, but it is preferably about 1,000 to 100,000 HRr ^-1 , preferably It is in the range of 1,000 to 50,000 Hr ^-1 .
The reaction temperature is 75 to 500 ° C, preferably 100 to 30
It is in the range of 0 ° C. The catalyst used in the present invention can be produced by a conventionally known method. In this case, the noble metal on the support can be in the form of a metal as well as in the form of an oxide or the like. The supported amount of noble metal is
The amount of metal is 0.1 to 5% by weight, preferably 0.5 to
It is 3% by weight. Further, the average pore diameter of the catalyst is 4 to 15
Angstroms, preferably 4-10 Angstroms. A particularly preferred catalyst used in the present invention is a noble metal catalyst supported by an ion exchange method on a zeolite carrier,
Especially platinum catalysts.

[0010]

EXAMPLES Next, the present invention will be described in more detail by way of examples.

Example 1 (Preparation of platinum catalyst supporting H-type mordenite) 10.0 g of Na-type mordenite was dried in air at 150 ° C. for 1 day, and then suspended in 100 g of 1M ammonium nitrate (NH ₄ NO ₃ ) aqueous solution. And the mixture is stirred for 24 hours while maintaining the liquid temperature at 80 to 90 ° C. This is filtered, washed with pure water, dried at 150 ° C. for 1 day, and then calcined in air at 450 ° C. to obtain H-type mordenite.
8 g of this H-type mordenite was suspended in 160 g of pure water, and the suspension was stirred at 90 to 95 ° C. for 2 hours.
Of tetraammine platinum II nitric acid solution ([Pt (NH ₃ ) ₄ ] (NO ₃ ) ₂ ) of 41.03 g is added dropwise. This is stirred at 90 to 95 ° C. for 24 hours, allowed to stand at room temperature for 24 hours, filtered, and thoroughly washed with pure water. Furthermore, after drying this at 150 ° C. for 1 day,
An H-type mordenite-supported platinum catalyst is obtained by firing in air at 300 ° C. and reducing in a hydrogen atmosphere at 350 ° C.

0.124 g of the H-type mordenite-supported platinum catalyst thus prepared was charged into an atmospheric flow reactor, and 0.5% of methanol and 0.1 of toluene, which is one of the aromatic compounds, were added while raising the temperature. %, Propane 0.1%,
Gas containing helium gas containing 10% oxygen at 200 per minute
The rate of removal of methanol was examined 1 hour after flowing in ml. The results are shown in Table 1 as Example 1.

Example 2 (Preparation of Na-type mordenite-supported platinum catalyst) 4.0 g of the H-type mordenite-supported platinum catalyst prepared in Example 1 was mixed with 1M.
Suspended in 100 g of an aqueous sodium nitrate (NaNO ₃ ) solution and stirred for 2 hours while maintaining the liquid temperature at 80 to 90 ° C.
This is filtered, washed with pure water, dried at 150 ° C. for 1 day, and calcined in air at 300 ° C. to obtain a Na-type mordenite-supported platinum catalyst.

0.124 g of the thus prepared Na-type mordenite-supported platinum catalyst was charged into an atmospheric pressure flow reactor, and methanol was added at a temperature of 0.5% and toluene, which is one of aromatic compounds, was added in an amount of 0.1%. %, Propane 0.1%,
Gas containing helium gas containing 10% oxygen at 200 per minute
The rate of removal of methanol was examined 1 hour after flowing in ml. The results are shown in Table 1 as Example 2.

Example 3 (Preparation of Na-type ZSM-5 supported platinum catalyst) Na-type ZSM
-5 (8.0 g) was dried in air at 150 ° C for 1 day, suspended in 160 g of pure water and stirred at 90 to 95 ° C for 2 hours, and then 0.01 M tetraammine platinum II nitric acid solution 41.03 g of ([Pt (NH ₃ ) ₄ ] (NO ₃ ) ₂ ) is added dropwise. This is stirred at 90 to 95 ° C. for 24 hours, allowed to stand at room temperature for 24 hours, filtered, and thoroughly washed with pure water. In addition, 1
After drying at 50 ° C for 1 day, it is baked at 300 ° C in air and reduced at 350 ° C in a hydrogen atmosphere to produce Na-type ZSM-.
A 5 supported platinum catalyst is obtained.

0.124 g of the thus-prepared Na-type ZSM-5-supported platinum catalyst was loaded into an atmospheric pressure flow reactor, and 0.5% of methanol was added while the temperature was raised. Toluene, one of aromatic compounds, was added to 0%. 0.1%, propane 0.1%,
Gas containing helium gas containing 10% oxygen at 200 per minute
The rate of removal of methanol was examined 1 hour after flowing in ml. The results are shown in Table 1 as Example 3.

Example 4 (Preparation of H-type Y-type zeolite-supported platinum catalyst) 10.0 g of Na-type Y-type zeolite was dried in air at 150 ° C. for 1 day and then 1 M ammonium nitrate (NH ₄ NO ₃ ) Aqueous solution 10
Suspend in 0g and keep the liquid temperature at 80-90 ° C.
Stir for 4 hours. Filter this, wash with pure water, 1 at 150 ℃
After daily drying, it is calcined in air at 450 ° C. to obtain H-type Y-type zeolite. Take 8g of this H-type Y-type zeolite 160
g in pure water and stirred at 90 to 95 ° C for 2 hours, and then 0.01 M tetraammineplatinum II nitric acid solution ([Pt (N
_{H 3) 4] (NO 3} ) 2) a to 41.03g dropwise. 90 to 9
The mixture is stirred at 5 ° C. for 24 hours, allowed to stand at room temperature for 24 hours, filtered, and thoroughly washed with pure water. Furthermore, this is 1 at 150 ℃
After drying on the day, calcination in air at 300 ° C, under hydrogen atmosphere 3
An H-type Y-type zeolite-supported platinum catalyst is obtained by reduction at 50 ° C.

0.124 g of the H-type Y-type zeolite-supported platinum catalyst thus prepared was charged into a normal pressure flow reactor, and 0.5% methanol and toluene, which is one of the aromatic compounds, were added while the temperature was raised. 0.1%, propane 0.1
%, Gas containing helium gas containing 10% oxygen 2 per minute
The removal rate of methanol was examined 1 hour after flowing 00 ml. The results are shown in Table 1 as Example 4.

Comparative Example 1 0.62 g of a commercially available platinum-alumina catalyst was taken, and the removal rate of methanol after 1 hour was similarly examined using this as a catalyst. The result is shown in Table 1 as Comparative Example 1. In the platinum alumina catalyst shown in the comparative example, the removal rate of methanol is about 20% when toluene coexists at 100 ° C. or lower. In comparison with this, the catalysts shown in Examples 1, 2, 3, and 4 had a methanol removal rate of about 100% at 100 ° C., and the catalysts in which platinum was supported on these zeolites by the ion exchange method coexisted with aromatic compounds. It is clear that the compound also has a high methanol oxidizing ability. The above results show that a catalyst in which platinum is supported on a carrier having regular pores such as zeolite is very effective for removing methanol in the presence of an aromatic compound such as toluene at low temperature. There is.

[0020]

[Table 1]

[0021]

INDUSTRIAL APPLICABILITY Unlike the conventional alumina-supported noble metal catalyst, the catalyst according to the present invention in which a carrier having regular pores such as zeolite is loaded with a noble metal is preferentially used in the presence of an aromatic compound. Has a high ability to remove oxygen-containing compounds even at low temperatures.

Claims (3)

[Claims] 1. Selective removal of an oxygen-containing compound, characterized in that a mixed gas containing an oxygen-containing compound, an aromatic compound and oxygen is brought into contact with a catalyst in which a noble metal is supported on a carrier having regular pores. Method. 2. The method according to claim 1, wherein the carrier is ZSM-5, mordenite or Y-type zeolite. 3. The method according to claim 1, wherein the catalyst is platinum supported on zeolite by an ion exchange method, and the oxygen-containing compound is methanol.