Process for removal of poisonous gases

Abstract

Hydrides of As, B, P, Sb or Se in a gas can easily be removed from the gas by contacting the gas with an adsorbent comprising activated carbon having (1) iodine and/or one or more kinds of iodine compounds and/or (2) one or more kinds of sulfates and nitrates of NH.sub.4, Ag, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb and Sn supported thereon.

Description

This invention relates to a process of treating poisonous gases containing hydrides of B, P, As, Sb and Se.

Hydrides, such as B.sub.2 H.sub.6, PH.sub.3, AsH.sub.3, SbH.sub.3 and H.sub.2 Se, are utilized in large quantities for raw material gases for production of semiconductors, fumigation gases, etc., but even in trace amounts, are extremely poisonous to the human body. Therefore, the development of a method capable of efficiently removing these hydrides in gas is strongly demanded.

As a method of removing hydrides of B, P, As, Sb and Se, there have been proposed, for example, a procedure of washing with chemical solutions such as oxidizing solutions, or an adsorption process with use of adsorbents composed mainly of ferric chloride. However, these methods show inferior removal effect and pose problems.

The present inventors, in view of these circumstances, conducted intensive investigation, and as a result, found that by using activated carbon with iodine, iodine compounds and sulfates and nitrates of NH.sub.4, Ag, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb and Sn, supported thereon hydrides of B, P, As, Sb and Se in gases can be removed highly efficiently, which has culminated in the present invention.

Thus, the present invention is concerned with:

A process of removing one or more kinds of hydrides of As, B, P, Sb or Se from a gas containing one or more kinds of hydrides of As, B, P, Sb or Se, which comprises contacting said gas with an adsorbent comprising activated carbon having (1) iodine and/or one or more kinds of iodine compounds (hereinafter referred to in some instances as "First Component") and/or (2) one or more kinds of sulfates and nitrates of NH.sub.4, Ag, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb and Sn (hereinafter referred to in some instances as "Second Component") supported thereon.

The activated carbon which is useful in the present invention may be any type of activated carbon produced by the known processes from coal, coke, wood charcoal, coconut shells, resins, etc., while its specific surface area is preferably within the range from 200 to 2000 m.sup.2 /g. With reference to its shape and form, use is suitably made for example of spherical- and cylindrical-formed, crushed, powdered and fibrous-formed activated carbon according to the type of gas treatment methods.

Specific examples of the First Component useful in the present invention, include iodides, such as LiI, NaI, KI, RbI, CsI, BeI.sub.2, MgI.sub.2, CaI.sub.2, SrI.sub.2, BaI.sub.2, NH.sub.4 I and HI, iodic acid and its salts, such as HIO.sub.3, NH.sub.4 IO.sub.3, NaIO.sub.3 and KIO.sub.3, periodic acid and its salts, such as HIO.sub.4, NH.sub.4 IO.sub.4, NaIO.sub.4 and KIO.sub.4, and iodine oxides, such as I.sub.2 O.sub.5 and IO.sub.2.

Specific examples of the Second Component, which is utilizable, include (NH.sub.4).sub.2 SO.sub.4, Ag.sub.2 SO.sub.4, Al.sub.2 (SO.sub.4).sub.3, Ti.sub.2 (SO.sub.4).sub.3, VOSO.sub.4, Cr.sub.2 (SO.sub.4).sub.3, MnSO.sub.4, FeSO.sub.4, Fe.sub.2 (SO.sub.4).sub.3, CoSO.sub.4, NiSO.sub.4, CuSO.sub.4, ZnSO.sub.4, CdSO.sub.4, PbSO.sub.4, SnSO.sub.4, NH.sub.4 NO.sub.3, AgNO.sub.3, Al(NO.sub.3).sub.3, Cr(NO.sub.3).sub.3, Mn(NO.sub.3).sub.2, Fe(NO.sub.3).sub.2, Fe(NO.sub.3).sub.3, Co(NO.sub.3).sub.2, Ni(NO.sub.3).sub.2, Cu(NO.sub.3).sub.2, Zn(NO.sub.3).sub.2, Cd(NO.sub.3).sub.2, Pb(NO.sub.3).sub.2, etc.

The adsorbent used in the present invention, which comprises activated carbon having each of the components being supported thereon, can be produced by impregnating or spraying activated carbon with a solution or suspension of the individual components in water (inclusive of aqueous acid or alkali solutions) or various solvents (e.g., alcohols, such as methanol and ethanol, ketones, such as acetone and methyl ethyl ketone, etc.), and if necessary, by drying the impregnated or sprayed activated carbon at a temperature of not higher than about 130.degree. C. or calcining at a temperature of not lower than 130.degree. C.

In cases in which not less than two components are deposited on activated carbon, the components may be supported simultaneously or may be supported individually, whereby they may be supported in arbitrary order.

The supported amounts of each of the First and Second Components in activated carbon are 1 mg to 500 mg per g of activated carbon (0.5 mg to 250 mg for silver sulfate and silver nitrate), preferably 5 to 400 mg (1 to 150 mg for silver sulfate and silver nitrate).

The present invention is usually carried out by contacting a gas containing hydrides of B, P, As, Sb and Se with the adsorbent in the presence of oxygen.

The contact temperature is not higher than 150.degree. C., preferably -10.degree. to 120.degree. C., more preferably 0.degree. to 100.degree. C., and the contact pressure is not more than 10 atm., preferably 0.01 to 5 atm., with the contact time being 1/20 to 100 seconds as converted at 25.degree. C. and 1 atm., preferably 1/10 to 50 seconds.

If oxygen is not contained in the gas to be treated, it is preferable to add oxygen to the gas. The amount of oxygen contained in the gas is usually not less than one mol per mol of hydrides of B, P, As, Sb and Se, preferably not less than 2 mol.

The contacting of the adsorbent with a gas containing hydrides of B, P, As, Sb and Se can be conducted for example by use of fixed bed, moving bed and fluidized bed.

The examples are described below to illustrate the present invention more specifically.

EXAMPLE 1

Activated carbon A.sub.0 of 16 to 24 mesh having a BET specific surface area of 1,150 m.sup.2 /g was sprayed uniformly with aqueous solutions or suspensions of the required amounts of iodine, iodine compounds and/or sulfates and nitrates of NH.sub.4, Ag, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb and Sn, and then dried at 110.degree. C.

15 ml each of the various adsorbents thus obtained were packed into columns of 1.6 cm in diameter made of glass, respectively, and the atmospheric air (with relative humidity of 60%) of 30.degree. C. containing 15 ppm of AsH.sub.3 and 15 ppm of PH.sub.3 was passed through the respective columns at a linear flow rate of 40 m/sec to conduct the individual adsorption break-through tests for AsH.sub.3 or PH.sub.3, whereby the removal ratios for AsH.sub.3 or PH.sub.3 at each of the determined times were measured. The results are as shown in Table 1.

TABLE 1__________________________________________________________________________ The first The second Percent removal of AsH.sub.3 Percent removal of PH.sub.3 component and component and at the elapsed time at the elapsed time shownAdsorbent its amount its amount shown below (%) below (%)No. (mg/g) (mg/g) 5 hrs. 10 hrs. 30 hrs. 5 hrs. 10 hrs. 30 hrs.__________________________________________________________________________A.sub.0 (Control) 0 0 35 5 0 4 0 0A.sub.1 (The present LiI-50 0 100 85 68 93 61 40invention)A.sub.2 (The present NaI-50 0 100 88 70 91 65 47invention)A.sub.3 (The present KI-50 0 100 100 100 100 100 100invention)A.sub.4 (The present MgI.sub.2 -50 0 100 80 64 98 61 35invention)A.sub.5 (The present BaI.sub.2 -50 0 100 85 73 90 65 41invention)A.sub.6 (The present NH.sub.4 I-50 0 100 100 96 95 90 80invention)A.sub.7 (The present NaIO.sub.3 -50 0 100 100 100 100 85 64invention)A.sub.8 (The present KIO.sub.3 -50 0 100 100 100 100 100 100invention)A.sub.9 (The present I.sub.2 -50 0 100 100 100 100 100 100invention)A.sub.10 (The present I.sub.2 O.sub.5 -50 0 100 100 100 100 100 100invention)A.sub.11 (The present HIO.sub.3 -50 0 100 100 100 100 100 98invention)A.sub.12 (The present KI-5 0 90 85 61 88 71 50invention)A.sub.13 (The present KI-25 0 100 100 100 100 100 90invention)A.sub.14 (The present KI-400 0 100 100 100 100 100 100invention)B.sub.1 (The present 0 (NH.sub.4).sub.2 SO.sub.4 -50 96 93 84 90 85 60invention)B.sub.2 (The present 0 AgNO.sub.3 -5 100 98 90 98 85 53invention)B.sub.3 (The present 0 Al(NO.sub.3).sub.3 -50 85 60 30 82 60 48invention)B.sub.4 (The present 0 Ti.sub.2 (SO.sub.4).sub.3 -50 81 48 23 80 55 31invention)B.sub.5 (The present 0 VOSO.sub.4 -50 98 83 53 87 65 43invention)B.sub.6 (The present 0 Cr(NO.sub.3).sub.3 -50 88 65 43 75 50 32invention)B.sub.7 (The present 0 MnSO.sub.4 -50 98 85 61 83 45 21invention)B.sub.8 (The present 0 FeSO.sub.4 -50 100 100 95 92 80 65invention)B.sub.9 (The present 0 Fe(NO.sub.3).sub.3 -50 100 100 91 100 90 75invention)B.sub.10 (The present 0 CoSO.sub.4 -50 98 85 73 85 72 60invention)B.sub.11 (The present 0 Ni(NO.sub.3).sub.2 -50 95 60 35 83 65 53invention)B.sub.12 (The present 0 CuSO.sub.4 -50 100 98 71 93 82 61invention)B.sub.13 (The present 0 Zn(NO.sub.3).sub.2 -50 95 80 63 83 60 46invention)B.sub.14 (The present 0 CdSO.sub.4 -50 97 78 68 80 64 41invention)B.sub.15 (The present 0 Pb(NO.sub.3).sub.2 -50 98 83 60 93 72 51invention)B.sub.16 (The present 0 SnSO.sub.4 -50 100 95 70 95 68 43invention)B.sub.17 (The present 0 Fe.sub.2 (SO.sub.4).sub.3 -50 100 95 90 100 75 47invention)__________________________________________________________________________ The first The second Percent removal of AsH.sub.3 Percent removal of PH.sub.3 component and component and at the elapsed time shown at the elapsed time shownAdsorbent its amount its amount below (%) below (%)No. (mg/g) (mg/g) 50 hrs. 100 hrs. 200 hrs. 50 hrs. 100 hrs. 200 hrs__________________________________________________________________________C.sub.1 (The present NaI-50 AgNO.sub.3 -50 100 100 100 100 100 100invention)C.sub.2 (The present KI-50 Ti.sub.2 (SO.sub.4).sub.3 -50 100 100 85 100 98 79invention)C.sub.3 (The present MgI-50 Cr(NO.sub.3).sub.3 -50 100 98 90 100 83 70invention)C.sub.4 (The present I.sub.2 O.sub.5 -50 Co(NO.sub.3).sub.2 -50 100 100 100 100 100 100invention)C.sub.5 (The present NH.sub.4 I-50 SnSO.sub.4 -50 100 100 85 100 100 81invention)C.sub.6 (The present KI-50 Ag.sub.2 SO.sub.4 -5 100 100 88 100 100 100invention)C.sub.7 (The present KI-50 VOSO.sub.4 -50 100 100 100 100 100 100invention)C.sub.8 (The present KI-50 Cr.sub.2 (SO.sub.4).sub.3 -50 100 100 100 100 100 100invention)C.sub.9 (The present KI-50 Mn(NO.sub.3).sub.2 -50 100 100 100 100 100 100invention)C.sub.10 (The present KI-50 Fe(NO.sub.3).sub.2 -50 100 100 100 100 100 100invention)C.sub.11 (The present KI-50 Co(NO.sub.3).sub.2 -50 100 100 100 100 100 100invention)C.sub.12 (The present KI-50 Cu(NO.sub.3).sub.2 -50 100 100 100 100 100 100invention)C.sub.13 (The present KI-50 ZnSO.sub.4 -50 100 100 100 100 100 100invention)C.sub.14 (The present NH.sub.4 I-50 FeSO.sub.4 -50 100 100 100 100 100 100invention)C.sub.15 (The present BaI-50 FeSO.sub.4 -50 100 100 80 100 100 89invention)C.sub.16 (The present I.sub.2 -5 FeSO.sub.4 -10 100 100 100 100 100 100invention) KI-10C.sub.17 (The present I.sub.2 -5 FeSO.sub.4 -10 100 100 100 100 100 100invention) NH.sub.4 I-10D.sub.1 (The present KI-5 FeSO.sub.4 -50 100 98 65 100 88 60invention)D.sub.2 (The present KI-10 FeSO.sub.4 -50 100 100 79 100 100 81invention)D.sub.3 (The present KI-50 FeSO.sub.4 -50 100 100 100 100 100 100invention)D.sub.4 (The present KI-50 FeSO.sub.4 -5 100 100 83 100 100 84invention)D.sub.5 (The present KI-50 FeSO.sub.4 -10 100 100 100 100 100 100invention)D.sub.6 (The present KI-5 FeSO.sub.4 -5 100 85 77 100 78 61invention)D.sub.7 (The present KI-5 Fe.sub.2 (SO.sub.4).sub.3 -50 100 93 81 100 96 86invention)D.sub.8 (The present KI-10 Fe.sub.2 (SO.sub.4).sub.3 -50 100 100 93 100 100 85invention)D.sub.9 (The present KI-50 Fe.sub.2 (SO.sub.4).sub.3 -5 100 100 95 100 100 83invention)D.sub.10 (The present KI-50 Fe.sub.2 (SO.sub.4).sub.3 -10 100 100 98 100 100 100invention)D.sub.11 (The present KI-5 Fe.sub.2 (SO.sub.4).sub.3 -5 100 93 75 100 90 71invention)D.sub.12 (The present KI-5 Fe.sub.2 (SO.sub.4).sub.3 -50 100 90 68 100 79 57invention)D.sub.13 (The present KI-5 FeSO.sub.4 -250 100 95 73 100 88 70invention)D.sub.14 (The present KI-250 FeSO.sub.4 -5 100 100 100 100 100 100invention)__________________________________________________________________________

EXAMPLE 2

Packed into columns of 1.6 cm in diameter made of glass were 20 ml each of A.sub.0, A.sub.3, A.sub.6, A.sub.10, A.sub.11, B.sub.2, B.sub.7, B.sub.8, B.sub.11, C.sub.1, C.sub.7, C.sub.12, C.sub.14, C.sub.17, D.sub.3, D.sub.8 and D.sub.13 set forth in the above Table 1, and the atmospheric air (with relative humidity of 60%) of 30.degree. C. containing 10 ppm of B.sub.2 H.sub.6, 10 ppm of H.sub.2 Se or 10 ppm of SbH.sub.3 was passed through the respective columns at a linear flow rate of 30 cm/sec to conduct the individual break-through adsorption tests for B.sub.2 H.sub.6, H.sub.2 Se or SbH.sub.3, whereby the lengths of time until B.sub.2 H.sub.6, H.sub.2 Se or SbH.sub.3 leaked out of the respective columns, (i.e., the lengths of time required until the respective removal ratios reached 95 %) were determined. The results are shown in Table 2.

TABLE 2__________________________________________________________________________ The length of time for which The length of time for which The length of time for which the removal percentages the removal percentages the removal percentagesAdsorbent for B.sub.2 H.sub.6 reached 95% for H.sub.2 Se reached 95% for SbH.sub.3 reached__________________________________________________________________________ 95%A.sub.0 (Control) 1/6 1/4 1/3A.sub.3 (The present 63 41 55invention)A.sub.6 (The present 43 40 48invention)A.sub.10 (The present 75 78 80invention)A.sub.11 (The present 30 28 30invention)B.sub.2 (The present 19 30 45invention)B.sub.7 (The present 25 19 24invention)B.sub.8 (The present 21 20 20invention)B.sub.11 (The present 28 32 19invention)C.sub.1 (The present 153 198 185invention)C.sub.7 (The present 258 250 233invention)C.sub.12 (The present 218 200 223invention)C.sub.14 (The present 300 310 305invention)C.sub.17 (The present 313 300 320invention)D.sub.3 (The present 355 368 390invention)D.sub.8 (The present 370 373 398invention)D.sub.13 (The present 195 210 195invention)__________________________________________________________________________

Claims

1. A process of removing one or more hydrides selected from the group consisting of hydrides of As, B, P, Sb and Se from a gas containing oxygen and one or more of said hydrides, which comprises contacting said gas with an adsorbent comprising activated carbon having (1) iodine and/or one or more iodine compounds and/or (2) one or more members selected from the group consisting of sulfates and nitrates of NH.sub.4, Ag, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb and Sn supported thereon.

2. A process as claimed in claim 1, wherein the adsorbent is one comprising activated carbon having (1) 1 to 500 mg of iodine and/or one or more iodine compounds and/or (2) 1 to 500 mg of one or more members selected from the group consisting of sulfates and nitrates of NH.sub.4, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb, and Sn supported thereon, per g of activated carbon.

3. A process as claimed in claim 1, wherein the adsorbent is one comprising activated carbon having (1) 1 to 500 mg of iodine and/or one or more iodine compounds and/or (2) 0.5 to 250 mg of one or more members selected from the group consisting of sulfate and nitrate of Ag supported thereon, per g of activated carbon.

4. A process as claimed in claim 1, wherein the adsorbent is one comprising activated carbon having iodine and potassium iodide supported thereon.

5. A process as claimed in claim 1, wherein the adsorbent is one comprising activated carbon having potassium iodide and ferrous sulfate supported thereon.

6. A process as claimed in claim 1, wherein the gas is contacted with the activated carbon at a temperature of not higher than 150.degree. C.