JPH07100130B2 - Gas purification method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for purifying gas, and more specifically, to efficiently remove a high concentration of harmful gas from a harmful gas cylinder or the like when such gas leaks rapidly. The present invention relates to a method for purifying gas for cleaning.

With the development of the semiconductor industry in recent years, the use amount of extremely toxic hydride gases such as arsine, phosphine, silane and diborane has been increasing. These harmful gases are indispensable as a source gas or a doping gas in the manufacturing process of silicon semiconductors and compound semiconductors, but both are extremely toxic, and the permissible concentration of each is 0.05 ppm for arsine (A _s H ₃ ). , With phosphine (PH ₃ ) 0.
3 ppm, silane (SiH ₄ ) 5 ppm, diborane (B ₂ H ₆ ) 0.1 p
pm, hydrogen selenide (SeH ₂ ) 0.05 ppm. These noxious gases are usually 0.1% as shown in the table below.
It is marketed by filling a gas cylinder of about 50.

In order to prevent the air from directly contaminating the outside air when gas leaks, these cylinders are normally stored in a cylinder storage container connected to a ventilation duct called a cylinder box, and are used for semiconductor processes. Used by connecting to gas supply pipe. Even if it is stored in such a cylinder box, due to an unexpected accident, for example,
There is absolutely no risk of sudden gas leaks that will empty the cylinder in a short time of about 10 minutes, and there is a strong demand for safety measures that can deal with such accidents.

[Conventional technology]

Known methods for removing arsine, phosphine, etc. contained in the gas are a wet method of absorbing and decomposing with a scrubber and a dry method of flowing a gas into a filling cylinder filled with an adsorbent or an oxidant to remove the gas. ing. Generally, the wet method has difficulty in corrosion by the absorbing liquid and post-treatment.
The disadvantage is that maintenance of the device is expensive.

As a dry method, in order to remove harmful gases such as arsine and phosphine in the air, a gas mask filled with activated carbon in chemical warfare is known. Attempts have also been made to attach substances and attempt to improve their removal ability. For example, using activated carbon as a carrier, a copper compound, an alkali metal compound,
Adsorbents such as arsine and phosphine containing one or more metal compounds such as Al, Ti, V, Cr, Mn and Fe (Japanese Patent Laid-Open No. 59-16
No. 0535, 60-71039) and an adsorbent such as arsine and phosphine in which activated carbon is impregnated with iodine or an iodine compound and a metal sulfate (JP-A-60-71040).

In addition to those using activated carbon as a carrier, the present inventors have blended (1) cupric oxide and (2) at least one metal oxide selected from the group consisting of silicon oxide, aluminum oxide and zinc oxide. However, there is a method of using a molded purifying agent (JP-A-61-209030).

[Problems to be solved by the invention]

However, although the adsorbent having activated carbon as a carrier as described above can remove harmful gases such as arsine and phosphine in a relatively high concentration, it does not remove harmful gases in a gas having a high concentration and a high flow rate. There is a problem that the activity is too low and the iodine reduced by these hydride-based gases is easily scattered.

On the other hand, the cleaning agent disclosed in Japanese Patent Laid-Open No. 61-209030 by the present inventors has a remarkably large removal capacity of harmful gas per unit weight and unit volume as compared with the conventional cleaning agent, and is capable of removing a large amount of harmful gas. You can

However, this purifying agent cannot be said to have a sufficient removal rate depending on the conditions, and as described above, it cannot be treated sufficiently swiftly in an emergency where harmful gas is suddenly leaked from a cylinder or the like. There is a problem.

Therefore, in the case of an emergency where a large amount of harmful gas leaks, the conventional removal method cannot be dealt with, and therefore, the advent of a purification method having further excellent removal performance has been desired.

[Means and actions for solving problems]

As a result of repeated intensive studies to solve these problems, the present inventors have found that a composition containing three components of manganese dioxide, copper oxide and cobalt oxide as a main component, and a purifying agent further containing a silver compound are used. The present invention has been found to be capable of extremely efficiently removing a high-concentration harmful gas that has leaked into the air, etc., by using it, and arrived at the present invention.

That is, the present invention is a method for purifying a gas in which a gas containing one or more of arsine, phosphine, silane, diborane and hydrogen selenide as a harmful gas is brought into contact with a purifying agent to remove the harmful gas from the gas. The method for purifying exhaust gas is characterized in that a molded body obtained by incorporating (2) a silver compound into a composition containing (1) manganese dioxide, copper oxide and cobalt oxide as main components is used as an agent.

The purification method of the present invention can efficiently remove harmful gases such as arsine and phosphine contained mainly in the air such as air, nitrogen and hydrogen.

In particular, the purification method of the present invention can remove a large amount of harmful gas having a relatively high concentration quickly and at room temperature. For example, as described above, it is possible to obtain an excellent effect such as rapid purification of a gas contaminated by a harmful gas such as a sudden leak from the cylinder.

In the present invention, a molded body obtained by containing a silver compound in a composition mainly containing three components of manganese dioxide, copper oxide and cobalt oxide (hereinafter referred to as Mn-Cu-Co composition) is used as a purifying agent. It

The content of manganese dioxide and copper oxide in the Mn-Cu-Co-based composition is usually 60 wt% or more in total, preferably
70 wt% or more, of which the ratio of copper oxide to manganese dioxide is usually 1: 0.2 to 1.2 by weight, preferably 1 :.
It is set to about 0.3 to 0.8.

The content of cobalt oxide in the Mn-Cu-Co composition depends on the contents of manganese dioxide and copper oxide, but is usually 5 to 40 wt%, preferably 10 to 30 wt%.

Further, if desired, the Mn-Cu-Co-based composition may contain, for example, oxides of aluminum, silicon, iron, nickel and potassium.

There are various methods for obtaining these Mn-Cu-Co-based compositions, for example, a method of simultaneously mixing oxides as respective components, a mixture of manganese dioxide and copper oxide, or a commercially available mixture ( Hopcalite) is also available, so a method of further mixing cobalt oxide with these two-component compositions, mixing at the stage of intermediates such as salts of these metals, hydroxides, etc., and oxidizing them by firing etc. And the like.

Such Mn-Cu-Co-based composition may be used as a molded body and may be used as it is for removal of hydride-based gas such as arsine and phosphine, but in that case, these harmful components are contained to some extent in the dry gas. Even if it can be removed, the purification capacity of the gas containing water such as the air in the relative humidity range of 30 to 100%, which is the same as in the normal atmosphere, is significantly lowered.

In order to eliminate these drawbacks and further improve the purifying ability, in the present invention, a Mn-Cu-Co based composition to which a silver compound is further added is used as a purifying agent.

Examples of the silver compound include silver (I) oxide, silver (II) oxide, and silver salts (I) such as inorganic acid silver, organic acid silver and silver halide. Examples of the inorganic acid silver include silver carbonate,
Silver nitrate, silver nitrite, silver sulfate, silver sulfite, silver chlorate, silver perchlorate, silver bromate, silver iodate, silver periodate, dihydrogen phosphate, silver phosphate, silver pyrophosphate, silver metaphosphate, tetra Examples of silver halides such as silver fluoroborate and silver hexalfluorophosphate include silver fluoride, silver chloride, silver bromide and silver iodide, and examples of organic silver salts include silver acetate and silver oxalate. Of these, silver oxide (I) and silver oxide (II) are preferable, and among various silver salts (I), salts that are sparingly soluble or insoluble in water are generally preferable, and examples thereof include silver carbonate and silver sulfate. Examples thereof include silver phosphate, silver sulfite, silver chloride, silver bromide, silver iodide, silver iodate, silver pyrrolide acid, silver metaphosphate and silver oxalate. Of these, silver oxide (I
I) is particularly preferred, followed by silver (I) carbonate, silver (I) oxide and mixtures thereof.

The amount of silver compound contained in the purifying agent is usually 0.01.
〜10.0wt% and preferably 0.2〜5wt%. If the content is 0.01 wt% or less, the gas purification efficiency decreases, while 10
If it is more than wt%, the economic burden will increase.

The form of the purifying agent may be a molded product of a mixture of an Mn-Cu-Co-based composition and a silver compound, or a molded product of the Mn-Cu-Co-based composition to which a silver compound is attached. However, for the purpose of effectively acting a relatively expensive silver compound in a small amount, it is preferable to attach the silver compound to the molded body of the Mn-Cu-Co composition like the latter. .

As the Mn-Cu-Co-based composition to which the silver compound is attached, various shapes such as a crushed product, an extrusion molded product, and a tablet molded product can be used. The size is about 4 to 20 mesh for crushed products, and 1.5 to 4 mmφ for extruded products.
× 3 to 20 mm, usually 3 mm in the case of tablet molding
A size of about 6 mmφ × 3 to 6 mm is preferable. However, there is no problem with other dimensions depending on the design conditions of the device.

Various methods can be used to attach the silver compound to the Mn-Cu-Co-based composition, and a wet method or a dry method may be used. As a simple method
There are a method of sprinkling a powdered silver compound on a molded body of the Mn-Cu-Co composition, a method of impregnating the silver compound as an aqueous slurry, a method of impregnating a water-soluble silver compound as an aqueous solution, and the like.

In the present invention, the particle density of the purifying agent is usually 0.62 to 1.88.
g / ml, preferably 0.78 to 1.56 g / ml, and the packing density when the cleaning agent is packed in a cleaning column is usually 0.4
The amount is about 1.2 g / ml, preferably about 0.5 to 1.0 g / ml.

In the present invention, the density of particles is the weight of the molded body (particles) divided by the geometric volume, and the packing density is the weight of the cleaning agent filled in the cylinder. Each is defined as divided by volume.

The concentration of hydride-based gas such as arsine and phosphine that can be removed by the purifying agent is usually 1% or less. If the concentration is higher than this, the reaction heat becomes large and a cooling device or the like may be required.

The temperature of the gas to be brought into contact with the purifying agent is usually 0 to 90 ° C., preferably 10 to 50 ° C. at room temperature, and heating or cooling is not particularly required. Of course, after the contact is started, the temperature rises in accordance with the concentration of the hydride-based gas due to the heat of reaction.

The pressure at the time of contact is usually atmospheric pressure, but reduced pressure or 1 Kg /
It is also possible to operate under pressure such as cm ² G.

The contact time is usually 0.01 seconds or longer, preferably 0.025 seconds or longer. If the contact time is shorter than 0.01 seconds, sufficient cleaning performance may not be obtained.

The humidity of gas such as air, nitrogen and hydrogen to which the present invention is applied is not particularly limited and may be not only a dry state but also a wet state. Generally, 30-100% equivalent to normal atmosphere
Often used at a relative humidity of less than 5%, in which case the water content of the purifier will vary depending on the relative humidity of the gas.
It is kept at about 30wt%. In addition, the purifying agent is not adversely affected by carbon dioxide gas in the air or the like, and the presence of these may rather slightly increase the purifying ability depending on the situation.

In purifying the gas containing water in the present invention,
It is preferable that the purifying agent is kept in a water-containing state corresponding to the humidity by being brought into contact with an atmospheric gas having a similar humidity in advance.

The purifying agent is usually packed in a purifying column for harmful gas and used as a fixed bed, but it can also be used as a moving bed or a fluidized bed.

For example, the purifying agent is filled in a purifying cylinder 1 as shown in the flow sheet of FIG. 1, and the purifying cylinder 1 is for continuously sucking and ventilating the air in the cylinder box 3 in which the gas cylinder 2 is housed. It is used by interposing it in a ventilation duct 5 connected to the blower 4.

When the purifying agent is used in such a state, the heat generation becomes large at a high concentration of the harmful gas exceeding 1%, and a heat removing means is required. However, in such equipment, it is usual to provide a blower having a sufficient capacity so that the concentration of the harmful gas is diluted to 1% or less by mixing with air even if the harmful gas is suddenly leaked. Specifically, many blowers with a ventilation capacity of about 5 to 200 m ³ / min are installed, and for example, a large amount of leakage occurs such that a commercial gas cylinder shown in the above table becomes empty in 5 to 10 minutes. In such a case, the content of harmful gas such as in the air is assumed to be about 50 to 1000 ppm.

The filling length of the purifying agent in the purification column depends on the flow rate of the gas and the concentration of harmful gas, etc. and cannot be specified unconditionally, but in practice it is usually about 50 to 500 mm, and the inner diameter of the purification column is the inner diameter of the gas flowing in the column. The empty cylinder linear velocity (LV) is about 0.3 to 1.5 m / sec. Generally, these are determined by the pressure loss of the packed bed, the contact efficiency with air and the amount of harmful gas.

〔The invention's effect〕

According to the gas purification method of the present invention, a harmful gas contained in the gas is arsine, phosphine, diborane, silane and hydrogen selenide, particularly a large amount of a relatively high-concentration harmful gas, efficiently and extremely quickly. Since it can be removed, an excellent effect can be obtained for the detoxification process in an emergency, for example, when a harmful gas is suddenly leaked from the gas cylinder.

Hereinafter, the present invention will be described more specifically by way of examples.

〔Example〕

Examples 1 to 5 (Preparation of Mn-Cu-Co-based composition) 100 g of active manganese dioxide and copper (II) hydroxide were mixed with copper oxide (I
40 g in terms of I) and 40 g in terms of cobalt (III) hydroxide in terms of cobalt oxide (Co ₂ O ₃ ) were weighed and mixed in powder form, and 15 g of alumina sol (Al ₂ O ₃ ) and a small amount of water were added. Was added and kneaded to obtain a composition, which was extruded and baked at 300 ° C. for 3 hours to obtain 1.5 φ × 5 to 20 mm Mn-Cu.
A molding of the Co-based composition was prepared.

(Preparation of silver (II) oxide) 102 g of silver nitrate was dissolved in 200 ml of water. Separately, 90 g of caustic soda and 150 g of potassium persulfate were dissolved in 200 ml of ion-exchanged water heated to 85 ° C while stirring. The above silver nitrate aqueous solution was added dropwise to a place where stirring was continued while heating the latter as it was to deposit a precipitate. This was washed by repeating decantation and washing with water, and then vacuum dried at 100 ° C. for 3 hours to obtain 74 g of silver (II) oxide powder.

(Preparation of Purifying Agent) Silver (II) oxide (7.2 g) was suspended in water (100 ml) with vigorous stirring, and the mixture was sprayed on the Mn-Cu-Co-based composition in the vat to remove silver (II) oxide. Impregnate the powder, then
Drying at 80 ℃ x 2 hours, silver (II) oxide 3.85wt
% Purifying agent (particle density 1.08 g / ml) was obtained. Then, it was left indoors to absorb moisture in the atmosphere to a water content of about 10 wt%.

(Activity test) Filling length is 100mm (filling amount 2
8.3ml, 25.0g) filled with a purifying agent and containing 200 to 2000ppm of arsine or phosphine in air at 60% relative humidity and 25 ° C for 11.4 to 20.4 / min (vacuum linear velocity LV67-120 cm / sec). A portion of the outlet gas of the purifying agent was sampled, and the concentration of arsine or phosphine in the outlet gas was measured by cold atomic absorption spectrometry.
The time to rise to ppb (effective treatment time) was measured.

The results are shown in Table 1.

Examples 6 to 8 Instead of arsine and phosphine, diborane, silane,
Effective treatment time was measured in the same manner as in Examples 1 to 5 for air containing hydrogen selenide.

However, the gas concentration at the outlet of the purifying column was measured for diborane and hydrogen selenide using a detector tube, and the time until effective detection of these gases (effective treatment time) was determined. The detection tube was manufactured by Dräger for diborane, and the lower limit of detection was 0.05 ppm. For hydrogen selenide, the lower limit of detection was 1 ppm.

For silane, a color-changing reagent in which basic copper carbonate was supported on alumina was used, but the lower limit of detection for this was 10 pp.
m.

The results are shown in Table 2.

Examples 9 and 10 The effective treatment time was measured in the same manner as in Example 1 except that nitrogen and hydrogen containing 1000 ppm of arsine or phosphine were used instead of air.

The results are shown in Table 3.

Examples 11 and 12 Effective treatment time was measured for each of the same Mn-Cu-Co-based compositions used in Example 1 except that the amount of silver (II) oxide was changed to 0.5 and 2.0 wt%. did.

The results are shown in Table 4.

Comparative Examples 1 and 2 A molded body of the same Mn-Cu-Co-based composition used in Example 1 was dried without silver (II) oxide being attached, and then left indoors to have a water content of about 10%. Using this as a purifying agent, the effective treatment time was measured for arsine and phosphine in the same manner as in Example 1.

The results are shown in Table 5.

Comparative Example 3-5 In place of the Mn-Cu-Co composition, activated carbon having a particle size of 6-10 mesh, α-alumina, and molecular sieve 5A were used as a carrier, and 4.25 wt% of silver (II) oxide was impregnated on the carrier. The effective treatment time was measured for each of the products in the same manner as in Example 1.

The results are shown in Table 6.

Examples 13 to 15 The amount of cobalt (III) hydroxide mixed was changed to cobalt oxide (Co
Molded bodies of three types of Mn-Cu-Co based compositions were prepared in the same manner as in Example 1 except that the amounts were changed to 20 g, 30 g, and 50 g in terms of ₂ O ₃ ).

A suspension of silver (II) oxide was sprayed on each of the molded bodies to obtain a purifying agent in which 3.85 wt% of silver (II) oxide was impregnated. After leaving this in a room to absorb moisture in the atmosphere to a water content of about 10%, the same is filled in a purifying cylinder as in Example 1 and air containing arsine is flowed to measure the effective treatment time. did.

The results are shown in Table 7.

Reference Example 1-2 A composition obtained by mixing 100 g of manganese dioxide, 40 g of copper oxide and 15 g of aluminum oxide in place of the Mn-Cu-Co composition, and using a molded body of a composition containing no cobalt oxide. Silver oxide (II) is 3.85 as in 1.
A cleaning agent impregnated with wt% was prepared. The purifying agent was allowed to absorb moisture in the air until the water content became about 10%, and then the effective treatment time was measured for the gas containing arsine and phosphine in the same manner as in Examples 1 and 5.

The results are shown in Table 8.

Examples 16 to 20 (Preparation of silver (I) oxide) 102 g of silver nitrate was dissolved in 200 ml of water. Separately, 90 g of caustic soda was dissolved in 200 ml of ion-exchanged water warmed to 85 ° C while stirring. The above silver nitrate aqueous solution was added dropwise to a place where stirring was continued while heating the latter as it was to deposit a precipitate. This product was washed by repeating decantation and washing with water, and then vacuum dried at 100 ° C. for 3 hours to obtain 69 g of silver (I) oxide powder.

(Mn-Cu-Co composition) The same composition as used in Example 1 was used.

(Preparation of Purifying Agent) Silver (I) oxide (7.2 g) was suspended in water (100 ml) with vigorous stirring, and the mixture was sprayed on the Mn-Cu-Co-based composition in the vat to remove silver (I) oxide. Impregnate the powder, then
Dry under the condition of 80 ℃ x 2 hours, and add silver oxide (I) 3.85wt
% Purifying agent was obtained. Then leave it indoors and 10wt%
Moisture in the atmosphere was absorbed up to a water content of a certain degree.

(Activity test) It carried out like Example 1.

The results are shown in Table 9.

Examples 21 to 23 Using the same type of purifying agent as in Examples 16 to 20, effective treatment time was measured in the same manner as in Examples 1 to 5 for air containing diborane, silane, hydrogen selenide instead of arsine and phosphine. did.

The results are shown in Table 10.

Examples 24 to 28 (Mn-Cu-Co-based composition) The same composition as that used in Example 1 was used.

(Preparation of Purifying Agent) Silver (I) carbonate (7.2 g) was suspended in water (100 ml) with vigorous stirring, and the mixture was sprayed on the Mn-Cu-Co-based composition in the vat to prepare silver (I) carbonate. Impregnate the powder, then
Silver (I) carbonate 3.85wt% after drying at 80 ℃ x 2 hours
% Of the impregnated purifying agent was obtained. Then leave it indoors 10
Absorbed moisture in the atmosphere to a water content of about wt%.

(Activity test) The effective treatment time was measured in the same manner as in Example 1.

The results are shown in Table 11.

Examples 29 to 31 Using the same type of purifying agent as in Examples 24 to 28, and using diborane, silane, hydrogen selenide instead of arsine and phosphine in the same manner as in Examples 1 to 5, effective treatment time Was measured.

The results are shown in Table 12.

Example 32 The same Mn as used in Example 1 was prepared by mixing silver carbonate (I) and silver oxide (II) as a silver compound alone and mixing them in a ratio of 1: 1 and suspending them in water. Effective treatment time was measured in the same manner as in Example 1 except that a purifying agent was sprayed on the -Cu-Co composition and a 3.85 wt% silver compound was used.

The results are shown in Table 13.

Examples 33, 34 (Preparation of Purifying Agent) To 200 g of the same Mn-Cu-Co composition as used in Example 1, water was added.
48 g of a silver nitrate aqueous solution prepared by dissolving 20 g of silver nitrate in 100 ml by spraying
Just sprayed. This Mn-Cu-Co-based composition impregnated with silver nitrate was dried at 80 ° C for 10 hours to obtain 208 g of a cleaning agent impregnated with 3.85 wt% silver nitrate.

This was left to stand in the air to give a product containing about 8 wt% of water, and the effective treatment time was measured in the same manner as in Examples 1 and 5.

The results are shown in Table 14.

Comparative Example 6-8 Activated carbon having a particle size of 6-10 mesh, α-alumina, and molecular sieve 5A were used as a carrier instead of the Mn-Cu-Co composition, and silver carbonate (I) was added at 4.25 wt%. The effective treatment time was measured in the same manner as in Example 1 for the thus adhered product.

The results are shown in Table 15.

Examples 35 and 36 Effective treatment times were measured for the same Mn-Cu-Co-based composition as used in Example 1 with different amounts of impregnated silver (I) carbonate to 0.5 and 2.0 wt%, respectively. did.

The results are shown in Table 16.

Examples 37 to 42 Instead of the silver (I) carbonate used in Example 24, silver sulfate, silver chloride, silver bromide, silver iodide, silver phosphate, and silver iodate were added at 3.85 wt%.
Then, the effective treatment time was measured in the same manner as in Example 1 after the moisture content in the atmosphere was absorbed to a water content of about 8% after drying.

The results are shown in Table 17.

Examples 43 and 44 Instead of silver nitrate in Examples 33 and 34, silver perchlorate and silver acetate were impregnated so as to be 3.85 wt% and dried, and then 8 wt% of moisture in the atmosphere was again absorbed. The effective treatment time was measured in the same manner as in Example 1.

The results are shown in Table 18.

Example 45 80 g of active manganese dioxide and copper (II) hydroxide were mixed with copper oxide (I
I) 40 g, cobalt (III) hydroxide 20 g in terms of cobalt oxide (Co ₂ O ₃ ), alumina sol (Al ₂ O ₃ ) 20 g and silver oxide (I) 10 g are mixed at the same time, and a small amount of this is added. After kneading and drying in a forming plate,
Sintered for 4 hours to obtain silver (I) oxide in the form of 4mmφ x 4mm pellets.
A cleaning agent containing 5.88 wt% was prepared. This purifying agent was further crushed to obtain 4 to 20 mesh, and the effective treatment time was measured in the same manner as in Example 1.

The results are shown in Table 19.

[Brief description of drawings]

FIG. 1 is a flow sheet showing an example in which a purifying agent for harmful gas is filled in a purifying cylinder and is interposed in a gas passage. The numbers in the drawings are as follows. 1 ... Purifying agent, 2 ... Gas cylinder 3, ... Cylinder box, 4 ... Blower and 5 ... Ventilation duct

Continuation of front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location B01J 23/89 A B01D 53/34 ZAB (72) Inventor Tadashi Hiramoto 5181 Tamura, Hiratsuka-shi, Kanagawa Japan Pionics Naoto Noda, Examiner, Hiratsuka Factory, Ltd.

Claims (1)

[Claims] 1. A method for purifying a gas, wherein a gas containing one or more of arsine, phosphine, silane, diborane and hydrogen selenide as a harmful gas is brought into contact with a purifying agent to remove the harmful gas from the gas. A method for purifying a gas, which comprises using a molded body comprising (1) a composition containing manganese dioxide, copper oxide and cobalt oxide as a main component and (2) a silver compound as an agent.