CA1100289A - Refining a gas containing hydrogen sulfide, nitrogen oxides and other contaminants - Google Patents
Refining a gas containing hydrogen sulfide, nitrogen oxides and other contaminantsInfo
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- CA1100289A CA1100289A CA280,735A CA280735A CA1100289A CA 1100289 A CA1100289 A CA 1100289A CA 280735 A CA280735 A CA 280735A CA 1100289 A CA1100289 A CA 1100289A
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Abstract
ABSTRACT OF THE DISCLOSURE
The disclosure describes a process for refining a gas which contains hydrogen sulfide, sulfur oxides and nitrogen oxides and may contain hydrogen cyanide as contaminants. The process comprises contacting the gas with an absorption medium to absorb the contaminants in the absorption medium. The absorp-tion medium contains as catalytic component specified naphtho-quino-chelate prepared by mixing (A) naphthoquinone or a deriva-tive thereof of the general formula or naphthodiquinone or a derivative thereof the general formula
The disclosure describes a process for refining a gas which contains hydrogen sulfide, sulfur oxides and nitrogen oxides and may contain hydrogen cyanide as contaminants. The process comprises contacting the gas with an absorption medium to absorb the contaminants in the absorption medium. The absorp-tion medium contains as catalytic component specified naphtho-quino-chelate prepared by mixing (A) naphthoquinone or a deriva-tive thereof of the general formula or naphthodiquinone or a derivative thereof the general formula
Description
` ` ` 110(~2~39 The present invention relates to a process for re-fining a gas which contains hydrogen sulfide, sulfur oxides and nitrogen oxides and may contain hydrogen cyanide. The present invention relates more particularly to a wet process for treatment of a gas by which desulfurization of the gas is achieved simultaneously with the removal of nitrogen oxide and hydrogen cyanide, if the latter is present, from the gas by absorbing such contaminant gases into the specified absorp-- tion medium.
Although a variety of processes are known for wet~
desulfurization of a gas, the known processes still suffer from some disadvantages. For example, in the Seaboard process, the absorbed hydrogen sulfide is discharged into the air during regeneration of the absorption medium. Consequently, this process results in air pollution, causing decay and damage-in - animals and plants and, furthermore, in discoloration and cor-rosion of metals. In the Thylox process handling of the materi-als and operation of the process involve dangers since a poison-ous arsenite is employed for desulfurization. Moreover, this process involves complicated operations, such as one for extrac-tion of the arsenite from the sulfur obtained. The Giammarco process is even more disadvantageous in that yreater care must be taken in handling the catalyst and removing arsenite from the sulfur than in the Thylox process since the former employs an absorption medium containing an arsenite of higher concen-tration than that in the latter.
Recently, several processes have been proposed in which an absorption medium containing a quinone type compound is employed. For example, a desulfurization process using benzoquinone has been proposed. However, in this process, the catalytic activity of benzoquinone i9 SO high that the catalytic life is insufficiently short since the oxidation-reduction ~. `
110~J2~99 potential of benzoquinone is as high as about 0.7 volt. As another example of the processes using a quinone type compound, mention can be made of the Stretford process which employs anthraquinone-2,5 or 2,6-di-sulfonate thereof as a catalyst component. However, since such component has a low oxidation-- reduction potential of about 0.228 volt, sufficient desulfuriz-ing effect cannot be obtained even when it is used in a very large quantity. In order to obviate the disadvantage of the Stretford process, there is proposed a process in which a metal, such as vanadium, arsenic or iron, an alkali salt and a tartarate are used in combination. This process is con-sidered to be one in which the desulfurization principles in each of the Thylox, Gia~marco and Vetrocoke processes are com-bined and a certain effect is attained therewith. (See Cana-dian Patent No. 672,084). However, the Stretford process or its modification is nothing more than a mere combination of the Thylox process with other known techniques, and still suffers from the need for removal of vanadium or the like and arsenic. Furthermore, the desulfurizing effect attained by the Stretford process or its modification is not sufficiently high.
It is of course noted that the above-mentioned pro-cesses are essentially directed only to desulfurization of a gas, and no process has yet been proposed which is effective in desulfurization of a gas simultaneously with the removal of nitrogen oxides.
The present inventor has already proposed an effec-tive process for desulfurization of a gas which employs, as catalytic component in the absorption medium, a specified quinone or its derivative (see U. S. Patent No. 3,459,495, Japanese Patent No. 427,094), or a quino-chelate compound (see U. S. Patent No. 3,937,795 or Japanese Patent No. 805,456), _~ -2-11002~9 ; these compounds having suitable oxidation-reduction potential ` in the range of from 0.45 to 0.7 volt.
This process employing a specified quinone or its derivative, or quino-chelate will provide an effective wet - process for desulfurization of a gas so as to overcome the disadvantages and defects of the above-mentioned conventional processes, but it is not thoroughly effective in removing nitrogen oxides simultaneously with sulfur-bearing contaminant such as hydrogen sulfide or sulfur dioxide.
` 10 Nowadays, environmental pollution due to nitrogen oxides has become as serious a problem as that caused by sul-fur-bearing gases, and several methods have been proposed for : removing nitrogen oxides and/or converting such gases into materials harmless to human beings, plants.and animals. Among . these, mention can be made of a process which meets the re-quirements to a certain degree, wherein No is converted to N2 or to N02 at a temperature exceeding 130C in the presence of ammonia or methane over alumina, silica, or alumina- or silica-supported noble metal. However, this process is applicable to à gas in which nitrogen oxides are contained in a considerable high amount, and is` disadvantageous in that it must be used in treating an extremely high volume of gas if this process is to . be employed in treating a gas containing nitrogen oxides on the order to several ppm or several hundred ppm such as coal gas or the waste gas from the Claus process.
It is the main object of the present invention to provide a process by which desulfurization of a gas can be ef-fectively accomplished simultaneously with the removal of nitrogen oxides, and, if present, hydrogen cyanide.
It is another object of the present invention to provide a novel absorption medium for wet gas refining process which comprises à specified quinone or its derivative or a 110C~289 specified quino-chelate as a catalytic component in combina-` tion with a specified solvent for the catalytic component.
These and other objects of the present invention and the advantages and merits achieved by the present inven-tion will be readily apparent from the following detailed des-cription thereof.
In accordance with the practlve of the process of the present invention, a gas, which contains nitrogen oxides as well as hydrogen sulfide and/or sulfur oxides and may fur-ther contain hydrogen cyanide, can be refined by contactingthe gas with the absorption medium so that such contaminants contained in the gas are absorbed in the medium. The absorp-tion medium contains as catalytic component a naphthoquino-chelate formed from naphthoquinone or a derivative therefrom having the general formula O(or OH) C~x O(or OH) or naphthodiquinone or a derivative therefrom having the gen-eral formula O(or OH) ~ O(or OH) .. ~ X
O(or OH) O(or OH) llOOZ~39 - in which X represents hydrogen atom, hydroxyl group, a lower alkyl group, a lower alkoxy group, sulfonic group (-S03H), carboxylic group (-COOH), an alkaline metal or alkaline earth metal salt of sulfonic or carboxylic group (such as -SO3Na, -COONa), thioglycol group (-S-CH2-COOH) or thiol group (-SR
in which R is a lower alkyl group). The naphthoquino-chelate - is prepared by mixing (A) said quinone or quinone derivative with (B) a precursor of a chelating agent which is selected from the group consisting of the reaction product of a metal selected from the group consisting of the metals of groups V, VI, VII and VIII in the fourth period of the Periodic Table, arsenic and selenium with an acid selected from the group consisting of oxalic, citric tartaric and glutaric acids, and aging the mixture of (A) and (B) to form a naphthoquino-chelate compound.
The process of the present invention is character-ized by the fact that the absorption medium contains as the solvent for the above-mentioned catalytic component (1) a - specified diamine selected from among cyclohexadiamine and diamines having the chemical formula NH2(C H2n)NH2 in which n is 2, 3 or 4 and (2) mono-, di-, tri- or tetra-acetate, mono-, di-, tri- or tetra-propionate, or mono-, di, tri- or tetra-buthylate of the diamine.
In carrying out the process of the present invention, the absorption medium which has absorbed the contaminants is then treated in a suitable manner for obtaining sulfur from hydrogen sulfide and sulfur oxides and thiocyanate from hydro-gen cyanide, if such were present in the gas, while producing gas having high nitrogen oxides concentration.
The present invention is based on the discovery that the absorption medium, which comprises the specified quino-chelate in combination with the specified diamine and acetate, llOCl Z~39 propionate or buthylate thereof, highly absorbs not only sulfur-bearing compound such as hydrogen sulfide and sulfur dioxide but also nitrogen oxides such as nitric oxide.
Acetate, propionate or buthylate of the diamine of the formula NH2(CnH2n)NH2 or cyclohexadiamine forms in the absorption system a chelate compound such as (acetate, pro-pionate or buthylate of NH2-CnH2n.NH2)Fe++ or (acetate, pro-pionate or buthylate of NH2 CnH2n NH2)Fe++* (hereinafter re-fered to as "the diamine-chelate"). Such chelate will absorb nitrogen oxides such as nitric oxide to produce a relatively stable compounds which may be expressed, for example, by the formula (acetate, propionate or buthylate of NH2-CnH2n-NH2)Fe++ NO.
This compound then liberates, when treated in a suitable man-ner such as heating, in the manner as expressed by the follow-ing equation, so that the nitrogen oxides concentrated gas is obtained.
(acetate, propionate or buthylate of NH2CnH2nNH2)Fe++-NO--~(acetate, propionate or buthylate of NH2 CnH2n NH2~Fe++ + NO~
In addition, the presence of the diamine-chelate is advantageous in that the precipitation of a metal sulfide such as FeS is prevented. On the other hand, the presence of hydro-gen sulfide and sulfur dioxide per se is advantageous in ren-dering such chelate more suitable form for absorbing nitrogen oxides. For example, it is found that the ferrous chelate is more effective than the ferric chelate in absorbing nitrogen oxides, and hydrogen sulfide and sulfur dioxide serve, because of their capacity for reduction, to convert Fe+++ to Fe+*.
The diamine selected from NH2(CnH2n)NH2 and cyclo-hexadiamine and acetate, propionate, or buthylate thereof will of course work as a good solvent for dissolving hydrogen sul-fide and sulfur dioxide. Because of their high dissolving capacities, hydrogen sulfide and sulfur dioxide in the gas to llO~Z~9 be refined are transferred in the solvent to cause a reaction therebetween in the following manner:
S 2 H2 H20 + 2S~
Excess hydrogen sulfide is oxidized by the quino-chelate to precipitate sulfur.
The metal in forming the diamine chelate may be fed from the excess metal in preparing the quino-chelate, the preparation of which will be described in details later. Thus, ~ the diamine-chelate may be formed together with the preparation 10 of the quino-chelate, in which a metal salt is added in excess of the amount that is necessary to prepare the quino-chelate and the diamine and the acetate (or propionate or buthylate~
-- thereof is added. Alternatively, the diamine and the acetate -~ (or propionate or buthylate) thereof may be added into the - aqueous or non-aqueous solution containing the quino-chelate, where the metal for forming the diamine-chelate is fed from the excess metal left in the preparation of the quino-chelate.
The amount of the diamine and the acetate ~or pro-pionate or buthylate) is optional mainly depending on the amount of nitrogen oxides present in the gas to be refined. In - most cases, as the amount of nitrogen oxides is rather small, the amount of the acetate (or propionate or buthylate) of the diamine may be small.
The naphthoquinone or naphthodiquinone or the deriva-tive thereof for forming the naphthoquino-chelate suitable for use in the absorption medium in the present invention are set forth in the above-mentioned patents issued to the present inventor, which is herein repeated in the following. These quinones and quino-chelates should have high solubility in water or an organic solvent. As suitably useful compounds meeting such conditions, there can be mentioned those having a group such as those set forth below and having an oxidation-reduction .- ,1 ~ 7-`\ llOo~g potential ranging from about 0.3 to about 0.8 volt, measured at 25C.
Goups to be introduced:
(a) hydrogen atom (-H) (b) hydroxyl group (-OH) (c) lower alkyl group (-CH , -C2H5, -C H , etc.) (d) lower alkoxy group (-OCH3, -OC2H5, -OC3H7, etc.) (e) sulfonic group (-SO3H) (f) carboxylic group (-COOH) (g) alkali metal or alkaline earth metal salts of acid groups (e) and (f) (-SO3Na, -COONa, etc.) (h) thioglycol group (-S-CH2-COOH) (i) thiol group (-SR in which R is an alkyl group) These groups (a) to (i3 are hereinafter referred to merely as "radicals". The naphthoquinone and naphthodiquinone and deri-vatives thereof which can be used in forming the naphthoquino-chelate are represented by the following general formulae:
O(or OH) O(or OH) I O(or OH) ~ - X or~ ~ X
O(or OH) O(or OH) O(or OH) wherein O (or OH) stands for a quinone (or hydroquinone) struc-ture and X designates a radical such as those mentioned above.
In the above formulae, the position of O (or OH) is merely a typical illustrative instance and it can be attached to any optional position. For example, theo~-type is shown above with respect to the naphthoquinone, but the ~-type is included in the naphthoquinones which can be used in this inven-tion. Further, the radical X can be attached to any optional . .
llOOZ89 position other than the position to which O(or OH) is attached.
Moreover, the number of the radical X present is also optional.
Specific examples of the radical-introduced quinones and hydro-quinones or derivatives thereof that can be used in this inven-tion are as follows:
Compound Structural Formula 1,4-naphthoquinone o O
1,2-naphthoquinone o ~\ O
1,4-naphthoquinone-2-sulfonic acid and its salt - o ~ r 1,2-naphthoquinone-4-sulfonic acid and its salt o S03M' 1,4-naphthoquinone-2-carboxylic acid and its salt ~COOM' O
_g _ . 1:10~289 Compound Structural Formula 1,2-naphthoquinone-4-carboxylic acid and its salt ro COOM'
Although a variety of processes are known for wet~
desulfurization of a gas, the known processes still suffer from some disadvantages. For example, in the Seaboard process, the absorbed hydrogen sulfide is discharged into the air during regeneration of the absorption medium. Consequently, this process results in air pollution, causing decay and damage-in - animals and plants and, furthermore, in discoloration and cor-rosion of metals. In the Thylox process handling of the materi-als and operation of the process involve dangers since a poison-ous arsenite is employed for desulfurization. Moreover, this process involves complicated operations, such as one for extrac-tion of the arsenite from the sulfur obtained. The Giammarco process is even more disadvantageous in that yreater care must be taken in handling the catalyst and removing arsenite from the sulfur than in the Thylox process since the former employs an absorption medium containing an arsenite of higher concen-tration than that in the latter.
Recently, several processes have been proposed in which an absorption medium containing a quinone type compound is employed. For example, a desulfurization process using benzoquinone has been proposed. However, in this process, the catalytic activity of benzoquinone i9 SO high that the catalytic life is insufficiently short since the oxidation-reduction ~. `
110~J2~99 potential of benzoquinone is as high as about 0.7 volt. As another example of the processes using a quinone type compound, mention can be made of the Stretford process which employs anthraquinone-2,5 or 2,6-di-sulfonate thereof as a catalyst component. However, since such component has a low oxidation-- reduction potential of about 0.228 volt, sufficient desulfuriz-ing effect cannot be obtained even when it is used in a very large quantity. In order to obviate the disadvantage of the Stretford process, there is proposed a process in which a metal, such as vanadium, arsenic or iron, an alkali salt and a tartarate are used in combination. This process is con-sidered to be one in which the desulfurization principles in each of the Thylox, Gia~marco and Vetrocoke processes are com-bined and a certain effect is attained therewith. (See Cana-dian Patent No. 672,084). However, the Stretford process or its modification is nothing more than a mere combination of the Thylox process with other known techniques, and still suffers from the need for removal of vanadium or the like and arsenic. Furthermore, the desulfurizing effect attained by the Stretford process or its modification is not sufficiently high.
It is of course noted that the above-mentioned pro-cesses are essentially directed only to desulfurization of a gas, and no process has yet been proposed which is effective in desulfurization of a gas simultaneously with the removal of nitrogen oxides.
The present inventor has already proposed an effec-tive process for desulfurization of a gas which employs, as catalytic component in the absorption medium, a specified quinone or its derivative (see U. S. Patent No. 3,459,495, Japanese Patent No. 427,094), or a quino-chelate compound (see U. S. Patent No. 3,937,795 or Japanese Patent No. 805,456), _~ -2-11002~9 ; these compounds having suitable oxidation-reduction potential ` in the range of from 0.45 to 0.7 volt.
This process employing a specified quinone or its derivative, or quino-chelate will provide an effective wet - process for desulfurization of a gas so as to overcome the disadvantages and defects of the above-mentioned conventional processes, but it is not thoroughly effective in removing nitrogen oxides simultaneously with sulfur-bearing contaminant such as hydrogen sulfide or sulfur dioxide.
` 10 Nowadays, environmental pollution due to nitrogen oxides has become as serious a problem as that caused by sul-fur-bearing gases, and several methods have been proposed for : removing nitrogen oxides and/or converting such gases into materials harmless to human beings, plants.and animals. Among . these, mention can be made of a process which meets the re-quirements to a certain degree, wherein No is converted to N2 or to N02 at a temperature exceeding 130C in the presence of ammonia or methane over alumina, silica, or alumina- or silica-supported noble metal. However, this process is applicable to à gas in which nitrogen oxides are contained in a considerable high amount, and is` disadvantageous in that it must be used in treating an extremely high volume of gas if this process is to . be employed in treating a gas containing nitrogen oxides on the order to several ppm or several hundred ppm such as coal gas or the waste gas from the Claus process.
It is the main object of the present invention to provide a process by which desulfurization of a gas can be ef-fectively accomplished simultaneously with the removal of nitrogen oxides, and, if present, hydrogen cyanide.
It is another object of the present invention to provide a novel absorption medium for wet gas refining process which comprises à specified quinone or its derivative or a 110C~289 specified quino-chelate as a catalytic component in combina-` tion with a specified solvent for the catalytic component.
These and other objects of the present invention and the advantages and merits achieved by the present inven-tion will be readily apparent from the following detailed des-cription thereof.
In accordance with the practlve of the process of the present invention, a gas, which contains nitrogen oxides as well as hydrogen sulfide and/or sulfur oxides and may fur-ther contain hydrogen cyanide, can be refined by contactingthe gas with the absorption medium so that such contaminants contained in the gas are absorbed in the medium. The absorp-tion medium contains as catalytic component a naphthoquino-chelate formed from naphthoquinone or a derivative therefrom having the general formula O(or OH) C~x O(or OH) or naphthodiquinone or a derivative therefrom having the gen-eral formula O(or OH) ~ O(or OH) .. ~ X
O(or OH) O(or OH) llOOZ~39 - in which X represents hydrogen atom, hydroxyl group, a lower alkyl group, a lower alkoxy group, sulfonic group (-S03H), carboxylic group (-COOH), an alkaline metal or alkaline earth metal salt of sulfonic or carboxylic group (such as -SO3Na, -COONa), thioglycol group (-S-CH2-COOH) or thiol group (-SR
in which R is a lower alkyl group). The naphthoquino-chelate - is prepared by mixing (A) said quinone or quinone derivative with (B) a precursor of a chelating agent which is selected from the group consisting of the reaction product of a metal selected from the group consisting of the metals of groups V, VI, VII and VIII in the fourth period of the Periodic Table, arsenic and selenium with an acid selected from the group consisting of oxalic, citric tartaric and glutaric acids, and aging the mixture of (A) and (B) to form a naphthoquino-chelate compound.
The process of the present invention is character-ized by the fact that the absorption medium contains as the solvent for the above-mentioned catalytic component (1) a - specified diamine selected from among cyclohexadiamine and diamines having the chemical formula NH2(C H2n)NH2 in which n is 2, 3 or 4 and (2) mono-, di-, tri- or tetra-acetate, mono-, di-, tri- or tetra-propionate, or mono-, di, tri- or tetra-buthylate of the diamine.
In carrying out the process of the present invention, the absorption medium which has absorbed the contaminants is then treated in a suitable manner for obtaining sulfur from hydrogen sulfide and sulfur oxides and thiocyanate from hydro-gen cyanide, if such were present in the gas, while producing gas having high nitrogen oxides concentration.
The present invention is based on the discovery that the absorption medium, which comprises the specified quino-chelate in combination with the specified diamine and acetate, llOCl Z~39 propionate or buthylate thereof, highly absorbs not only sulfur-bearing compound such as hydrogen sulfide and sulfur dioxide but also nitrogen oxides such as nitric oxide.
Acetate, propionate or buthylate of the diamine of the formula NH2(CnH2n)NH2 or cyclohexadiamine forms in the absorption system a chelate compound such as (acetate, pro-pionate or buthylate of NH2-CnH2n.NH2)Fe++ or (acetate, pro-pionate or buthylate of NH2 CnH2n NH2)Fe++* (hereinafter re-fered to as "the diamine-chelate"). Such chelate will absorb nitrogen oxides such as nitric oxide to produce a relatively stable compounds which may be expressed, for example, by the formula (acetate, propionate or buthylate of NH2-CnH2n-NH2)Fe++ NO.
This compound then liberates, when treated in a suitable man-ner such as heating, in the manner as expressed by the follow-ing equation, so that the nitrogen oxides concentrated gas is obtained.
(acetate, propionate or buthylate of NH2CnH2nNH2)Fe++-NO--~(acetate, propionate or buthylate of NH2 CnH2n NH2~Fe++ + NO~
In addition, the presence of the diamine-chelate is advantageous in that the precipitation of a metal sulfide such as FeS is prevented. On the other hand, the presence of hydro-gen sulfide and sulfur dioxide per se is advantageous in ren-dering such chelate more suitable form for absorbing nitrogen oxides. For example, it is found that the ferrous chelate is more effective than the ferric chelate in absorbing nitrogen oxides, and hydrogen sulfide and sulfur dioxide serve, because of their capacity for reduction, to convert Fe+++ to Fe+*.
The diamine selected from NH2(CnH2n)NH2 and cyclo-hexadiamine and acetate, propionate, or buthylate thereof will of course work as a good solvent for dissolving hydrogen sul-fide and sulfur dioxide. Because of their high dissolving capacities, hydrogen sulfide and sulfur dioxide in the gas to llO~Z~9 be refined are transferred in the solvent to cause a reaction therebetween in the following manner:
S 2 H2 H20 + 2S~
Excess hydrogen sulfide is oxidized by the quino-chelate to precipitate sulfur.
The metal in forming the diamine chelate may be fed from the excess metal in preparing the quino-chelate, the preparation of which will be described in details later. Thus, ~ the diamine-chelate may be formed together with the preparation 10 of the quino-chelate, in which a metal salt is added in excess of the amount that is necessary to prepare the quino-chelate and the diamine and the acetate (or propionate or buthylate~
-- thereof is added. Alternatively, the diamine and the acetate -~ (or propionate or buthylate) thereof may be added into the - aqueous or non-aqueous solution containing the quino-chelate, where the metal for forming the diamine-chelate is fed from the excess metal left in the preparation of the quino-chelate.
The amount of the diamine and the acetate ~or pro-pionate or buthylate) is optional mainly depending on the amount of nitrogen oxides present in the gas to be refined. In - most cases, as the amount of nitrogen oxides is rather small, the amount of the acetate (or propionate or buthylate) of the diamine may be small.
The naphthoquinone or naphthodiquinone or the deriva-tive thereof for forming the naphthoquino-chelate suitable for use in the absorption medium in the present invention are set forth in the above-mentioned patents issued to the present inventor, which is herein repeated in the following. These quinones and quino-chelates should have high solubility in water or an organic solvent. As suitably useful compounds meeting such conditions, there can be mentioned those having a group such as those set forth below and having an oxidation-reduction .- ,1 ~ 7-`\ llOo~g potential ranging from about 0.3 to about 0.8 volt, measured at 25C.
Goups to be introduced:
(a) hydrogen atom (-H) (b) hydroxyl group (-OH) (c) lower alkyl group (-CH , -C2H5, -C H , etc.) (d) lower alkoxy group (-OCH3, -OC2H5, -OC3H7, etc.) (e) sulfonic group (-SO3H) (f) carboxylic group (-COOH) (g) alkali metal or alkaline earth metal salts of acid groups (e) and (f) (-SO3Na, -COONa, etc.) (h) thioglycol group (-S-CH2-COOH) (i) thiol group (-SR in which R is an alkyl group) These groups (a) to (i3 are hereinafter referred to merely as "radicals". The naphthoquinone and naphthodiquinone and deri-vatives thereof which can be used in forming the naphthoquino-chelate are represented by the following general formulae:
O(or OH) O(or OH) I O(or OH) ~ - X or~ ~ X
O(or OH) O(or OH) O(or OH) wherein O (or OH) stands for a quinone (or hydroquinone) struc-ture and X designates a radical such as those mentioned above.
In the above formulae, the position of O (or OH) is merely a typical illustrative instance and it can be attached to any optional position. For example, theo~-type is shown above with respect to the naphthoquinone, but the ~-type is included in the naphthoquinones which can be used in this inven-tion. Further, the radical X can be attached to any optional . .
llOOZ89 position other than the position to which O(or OH) is attached.
Moreover, the number of the radical X present is also optional.
Specific examples of the radical-introduced quinones and hydro-quinones or derivatives thereof that can be used in this inven-tion are as follows:
Compound Structural Formula 1,4-naphthoquinone o O
1,2-naphthoquinone o ~\ O
1,4-naphthoquinone-2-sulfonic acid and its salt - o ~ r 1,2-naphthoquinone-4-sulfonic acid and its salt o S03M' 1,4-naphthoquinone-2-carboxylic acid and its salt ~COOM' O
_g _ . 1:10~289 Compound Structural Formula 1,2-naphthoquinone-4-carboxylic acid and its salt ro COOM'
2-methyl-1,4-naphthoquinone O
1~
O
2,3-dimethyl-1,4-naphthoquinone - ~ ~ CH3 ~' , o 2,5-dimethyl-1,4-naphthoquinone 2,6-dimethyl-1,4-naphthoquinone CH
` . 1100289 Structural Formula Compound 2-methyl-1,4-naphthoquinone-3-sulfonic acid and its salt O
503M' O
' 2-alkylthio-1,4-naphthoquinone ~ \ SR
2-carboxymethylmercapto-1,4-naphthoquinone ~ ~ ~ S-CH2-COOM' o 1,4,5,8-naphthodiquinone O O
O O
1,2,3,4-naphthodiquinone O
IJ
~CF
110~2~39 Compound Structural Formula 2-hydroxy-1,4-naphthoquinone o 0~1 5-hydroxy-1,4-naphthoquinone ~"' `3 OH O
6-hydroxy-1,4-naphthoquinone OH \~ ' \
; 2,5-dihydroxy-1,4-naphthoquinone OH
OH O
2,6-dihydroxy-1,4-naphthoquinone HO ~ ~ OH
` .` 110~289 . .
- Compound Structural Formula 2,7-dihydroxy-1,4-naphthoquinone O
2,8-dihydroxy-1,4-naphthoquinone - OH O
~J,~I~,~,r OH
5,6-dihydroxy-1,4-naphthoquinone .. , ~,JI,. .
HO ~ ~ ~ ~ J
OH O
5,8-dihydroxy-1,4-naphthoquinone OH O
OH O
2,5,8-trihydroxy-1,4-naphthoquinone OH o ro~
llOl~lZ~39 Compound Structural Formula
1~
O
2,3-dimethyl-1,4-naphthoquinone - ~ ~ CH3 ~' , o 2,5-dimethyl-1,4-naphthoquinone 2,6-dimethyl-1,4-naphthoquinone CH
` . 1100289 Structural Formula Compound 2-methyl-1,4-naphthoquinone-3-sulfonic acid and its salt O
503M' O
' 2-alkylthio-1,4-naphthoquinone ~ \ SR
2-carboxymethylmercapto-1,4-naphthoquinone ~ ~ ~ S-CH2-COOM' o 1,4,5,8-naphthodiquinone O O
O O
1,2,3,4-naphthodiquinone O
IJ
~CF
110~2~39 Compound Structural Formula 2-hydroxy-1,4-naphthoquinone o 0~1 5-hydroxy-1,4-naphthoquinone ~"' `3 OH O
6-hydroxy-1,4-naphthoquinone OH \~ ' \
; 2,5-dihydroxy-1,4-naphthoquinone OH
OH O
2,6-dihydroxy-1,4-naphthoquinone HO ~ ~ OH
` .` 110~289 . .
- Compound Structural Formula 2,7-dihydroxy-1,4-naphthoquinone O
2,8-dihydroxy-1,4-naphthoquinone - OH O
~J,~I~,~,r OH
5,6-dihydroxy-1,4-naphthoquinone .. , ~,JI,. .
HO ~ ~ ~ ~ J
OH O
5,8-dihydroxy-1,4-naphthoquinone OH O
OH O
2,5,8-trihydroxy-1,4-naphthoquinone OH o ro~
llOl~lZ~39 Compound Structural Formula
3,5,7-trihydroxy-1,4-naphthoquinone O
Ho ~ OH
OH o 2,3-dihydroxy~1,4-naphtho-quinone - O
6,7-dihydroxy-1,4-naphtho-quinone o HO
o 2,3,6-trihydroxy-1,4- O
naphthoquinone ll / ~ , ~ OH
HO
2,3,5,8-tetrahydroxy-1,4-naphthoquinone OH
OH
OH o ` 110C12139 Com~ound Structural Formula .:
5,6,8-trihydroxy-1,4-naphtho-quinone OH o OH o 2-methoxy-1,4-naphthoquinone (~
o 2-methoxy-3-hydroxy-1,4-naphthoquinone ~ OH
': ' O
. _ : 2-methyl-1,4,5,8-naphthodi-quinone ~ , CH3 : O o .
2-methoxy-1,4,5,8-naphtho-diquinone O
O O
- llO~Z89 Compound Structural Formula 2-ethyl-1,4,5,8-naphthodi-quinone 3~ C 2H5 O O
2-ethoxy-1,4,5,8-naphthodi-quinone O - O
~r Oc2 5 O O
2-propyl-1,4,5,8-naphthodi-quinone ~ 3 7 - O O
2-propoxy-1,4,5,8-naphthodi-quinone O O
/~ roc~H7 O O
```~ ` l~O~Z~99 In the present invention, the above-mentioned quinone or the quinone derivative may be used as the catalytic com-ponent in the absorption medium. However, the refining effect for a gas is improved when as the catalytic component the quino-chelate is employed which is prepared by mixing the above-mentioned quinone or quinone derivative with the chel-` ating agent precursor described below, and aging the mixture.
The aging is conducted over a wide time range generally from as short as about 10 minutes to about 12 hours and preferably about 30 minutes to about 3 hours. The resulting naphtho-quino chelate compound:is used as an absorption medium in the form of an aqueous solution of a concentration of 0.01 to 500 mole/kl.
In preparing the naphthoquino-chelate suitable for use in this invention, there may be employed as metals of Groups V, VI, VII or VIII in the fourth period of the Periodic Table and arsenic and selenium, for example, vanadium, arsenic, chromium, selenium, manganese, iron, cobalt and nickel, Vana-dium and iron are especially preferred.
As the aliphatic carboxylic acid or hydroxycarboxylic acid that can be employed in carrying out the process of this invention, there can be mentioned, for example, oxalic acid, citric acid, tartaric acid, glutaric acid and the like.
The reaction of a compound of the above-mentioned metals, such as a hydroxide or chloride, with the aliphatic carboxylic acid or hydroxycarboxylic acid is conducted in water or in any other suitable solvent at an appropriate pH, general-ly ranging from 4 to 10 according to customary methods. The so formed chelating agent precursors are represented by the following general formula:
(Alk-Y)nM
wherein Alk stands for an alkali metal or ammonium group, M
' ` 11(11~2~39 designates a metal belonging to Groups V, VI, VII or VIII in the fourth period of the Periodic Table, arsenic or selenium, n represents a number from 1 to 3 and Y is an acid or hydroxyl residue of the aliphatic carboxylic acid or hydroxycarboxylic acid.
Examples of the chelating agent precursor obtained by employing tartaric acid or its alkali salt as the starting material are as follows:
COOM' M'OOC COOM' MII
- ,CHO~ MII OHC (I) CHO (II) CHO ~ M'OHC CHOM' COOM' M'OOC COOM' 3 10, MII__--- M'OOC ,CO - MII - OOC
CHO ~ ~ --OHC (III) CHO ~ M'OHC (IV) CHOM' M'OHC CHOM' M'OHC
.COOM' M'OOC COOM' M'OHC
COOM OOC COO M'OOC
. CHO MII ~ OHC (V) CHOM' MII , (VI) . CHOM' M'OHC CHOM' M'OHC
COOM' 2 M'OOC ~CHOM'M'OOC
.
COO OOC 'COO~
CHOM ~ ~ OHC CHOM' ' MII , (VII) l MII (VIII) CHOM ~ M'OHC CHOM' COO M'OOC COOM' wherein M' is hydrogen, ammonium or an alkali metal such as sodium and potassium and M is as defined above and prefer-ably vanadium or iron.
The amount of the chelating agent precursor employed in accomplishing the process of this invention can vary widely llO(~Z~9 being optionally chosen, and sufficient and satisfactory re-sults can be obtained when it is added in an amount of from about 0.01 to about 5~/O by weight, based on the quinone or hydroquinone compound employed.
The utilization of a chelating agent precursor, such as mentioned above provides a further advantage in that even when the metal has come into contact with hydrogen sulfide in the absorption liquid, precipitation of a metal sulfide is - prevented by its protective activity.
One of the features of this invention is that the absorption medium can have a pH value of a broad range of gen-erally from about 3 to about 10. In view of the fact that in the conventional methods known desulfurization is possible only in an alkaline solution, it will readily be understood that the process of this invention can be applied broadly in various fields.
According to the present-invention, with the use of the diamine as solvent which has high dissolving capacity both ~- for sulfur-bearing compounds such as hydrogen sulfide or sul-fur dioxide and nitrogen oxides such as nitric oxide, particles of p~ecipitated sulfur is formed from hydrogen sulfide or sul-fur dioxide while the relatively stable adduct such as ~acetate, propionate or buthylate of NH2 CnH2n-NH2)Fe~+-NO is formed.
Thus, by treating the absorption medium, after having been con-tacted with the gas to be refined, in a suitable manner such as by heating the medium or by blowing a gas stream into the medium, and subjecting the medium to~a settling treatment in a suitable device, the gas in which the nitrogen oxides such as nitric oxide is highly concentrated is discharged from the top of the device while the precipitated sulfur is extracted from the bottom. Such nitrogen oxides concentrated gas may be subjected to the above-mentioned process by which NO can be -` 110~289 converted into N2. Such treatment of the absorption medium may be conducted after or before the oxidizing step of the medium for a reuse of the medium.
It should be mentioned that according to the present invention since the high-boiling organic solvent is employed, it is possible to use the temperature of the absorption liquid, say, over the melting point of sulfur (120C), and hence, the fine particles of sulfur can be melted to form coarse particles which then settle down so as to be recovered as pure melted sulfur. Thus, the process of this invention is advantageous in that sulfur is recovered in the most desirable form while the loss of the liquor and the catalyst is prevented. In a conventional wet process for desulfurization of sulfur-con-taining gas, the precipitated sulfur is recovered by using a filter-press. However, with such filter-press, the water can-not be removed as much as over 60~/o. This fact can be easily ; understood from a simple calculation of the volume of gap among the particles of the sulfur. Thus, such process is dis-advantageous in that it results in degradation of sulfur re-covered as well as loss of alkaline, acid, organic solvent or even catalyst to be used in an absorption medium.
In addition, when hydrogen cyanide is contacted with sulfur of ordinary form, it hardly reacts with the sulfur, and hence, there is practically no conversion to thiocyanate.
In contrast, if sulfur is in the atomic state, hydrogen cyanide reacts with it very readily and it is easily converted to a thiocyanate. When the quinone or its derivative or quino-chelate compound of this invention is present, atomic sulfur is readily formed and in a particle size distribution in which the maximum particles size is within a range of from about 0.01 to about 2,u. As may be readily understood from this fact, sulfur is in a highly active state, and it reacts with hydrogen cyanide ` . 11~2~39 to form a thiocyanate as follows:
NCN + atomic S NCNS
An instance of the sulfur particle size distribution in the absorption liquid observed when the operation is con-tinued for 15 hours is as follows particle size (jU) amount of particles (%) - below 0.1 80 0.1 to 1 15 1 to 2 5 The oxidation-reduction state and the deposition of sulfur are provided in the following table with respect to typical quinone compounds for showing the effects of the pre-sent invention.
TABLE
E as measured at 25C State of Sulfur ~xidized Form (volt) Deposition o-benzoquinone 0.787 no sulfur precipitate, extreme formation of thionic acid 3-hydroxy-o-benzo- small amount of sulfur quinone 0.713 precipitate p-benzoquinone 0.699 "
1,4-naphthoquinone0.484 sulfur precipitate 9,10-anthraquinone0.154 no sulfur precipitate 1,2-naphthoquinone-0.628 sulfur precipitate
Ho ~ OH
OH o 2,3-dihydroxy~1,4-naphtho-quinone - O
6,7-dihydroxy-1,4-naphtho-quinone o HO
o 2,3,6-trihydroxy-1,4- O
naphthoquinone ll / ~ , ~ OH
HO
2,3,5,8-tetrahydroxy-1,4-naphthoquinone OH
OH
OH o ` 110C12139 Com~ound Structural Formula .:
5,6,8-trihydroxy-1,4-naphtho-quinone OH o OH o 2-methoxy-1,4-naphthoquinone (~
o 2-methoxy-3-hydroxy-1,4-naphthoquinone ~ OH
': ' O
. _ : 2-methyl-1,4,5,8-naphthodi-quinone ~ , CH3 : O o .
2-methoxy-1,4,5,8-naphtho-diquinone O
O O
- llO~Z89 Compound Structural Formula 2-ethyl-1,4,5,8-naphthodi-quinone 3~ C 2H5 O O
2-ethoxy-1,4,5,8-naphthodi-quinone O - O
~r Oc2 5 O O
2-propyl-1,4,5,8-naphthodi-quinone ~ 3 7 - O O
2-propoxy-1,4,5,8-naphthodi-quinone O O
/~ roc~H7 O O
```~ ` l~O~Z~99 In the present invention, the above-mentioned quinone or the quinone derivative may be used as the catalytic com-ponent in the absorption medium. However, the refining effect for a gas is improved when as the catalytic component the quino-chelate is employed which is prepared by mixing the above-mentioned quinone or quinone derivative with the chel-` ating agent precursor described below, and aging the mixture.
The aging is conducted over a wide time range generally from as short as about 10 minutes to about 12 hours and preferably about 30 minutes to about 3 hours. The resulting naphtho-quino chelate compound:is used as an absorption medium in the form of an aqueous solution of a concentration of 0.01 to 500 mole/kl.
In preparing the naphthoquino-chelate suitable for use in this invention, there may be employed as metals of Groups V, VI, VII or VIII in the fourth period of the Periodic Table and arsenic and selenium, for example, vanadium, arsenic, chromium, selenium, manganese, iron, cobalt and nickel, Vana-dium and iron are especially preferred.
As the aliphatic carboxylic acid or hydroxycarboxylic acid that can be employed in carrying out the process of this invention, there can be mentioned, for example, oxalic acid, citric acid, tartaric acid, glutaric acid and the like.
The reaction of a compound of the above-mentioned metals, such as a hydroxide or chloride, with the aliphatic carboxylic acid or hydroxycarboxylic acid is conducted in water or in any other suitable solvent at an appropriate pH, general-ly ranging from 4 to 10 according to customary methods. The so formed chelating agent precursors are represented by the following general formula:
(Alk-Y)nM
wherein Alk stands for an alkali metal or ammonium group, M
' ` 11(11~2~39 designates a metal belonging to Groups V, VI, VII or VIII in the fourth period of the Periodic Table, arsenic or selenium, n represents a number from 1 to 3 and Y is an acid or hydroxyl residue of the aliphatic carboxylic acid or hydroxycarboxylic acid.
Examples of the chelating agent precursor obtained by employing tartaric acid or its alkali salt as the starting material are as follows:
COOM' M'OOC COOM' MII
- ,CHO~ MII OHC (I) CHO (II) CHO ~ M'OHC CHOM' COOM' M'OOC COOM' 3 10, MII__--- M'OOC ,CO - MII - OOC
CHO ~ ~ --OHC (III) CHO ~ M'OHC (IV) CHOM' M'OHC CHOM' M'OHC
.COOM' M'OOC COOM' M'OHC
COOM OOC COO M'OOC
. CHO MII ~ OHC (V) CHOM' MII , (VI) . CHOM' M'OHC CHOM' M'OHC
COOM' 2 M'OOC ~CHOM'M'OOC
.
COO OOC 'COO~
CHOM ~ ~ OHC CHOM' ' MII , (VII) l MII (VIII) CHOM ~ M'OHC CHOM' COO M'OOC COOM' wherein M' is hydrogen, ammonium or an alkali metal such as sodium and potassium and M is as defined above and prefer-ably vanadium or iron.
The amount of the chelating agent precursor employed in accomplishing the process of this invention can vary widely llO(~Z~9 being optionally chosen, and sufficient and satisfactory re-sults can be obtained when it is added in an amount of from about 0.01 to about 5~/O by weight, based on the quinone or hydroquinone compound employed.
The utilization of a chelating agent precursor, such as mentioned above provides a further advantage in that even when the metal has come into contact with hydrogen sulfide in the absorption liquid, precipitation of a metal sulfide is - prevented by its protective activity.
One of the features of this invention is that the absorption medium can have a pH value of a broad range of gen-erally from about 3 to about 10. In view of the fact that in the conventional methods known desulfurization is possible only in an alkaline solution, it will readily be understood that the process of this invention can be applied broadly in various fields.
According to the present-invention, with the use of the diamine as solvent which has high dissolving capacity both ~- for sulfur-bearing compounds such as hydrogen sulfide or sul-fur dioxide and nitrogen oxides such as nitric oxide, particles of p~ecipitated sulfur is formed from hydrogen sulfide or sul-fur dioxide while the relatively stable adduct such as ~acetate, propionate or buthylate of NH2 CnH2n-NH2)Fe~+-NO is formed.
Thus, by treating the absorption medium, after having been con-tacted with the gas to be refined, in a suitable manner such as by heating the medium or by blowing a gas stream into the medium, and subjecting the medium to~a settling treatment in a suitable device, the gas in which the nitrogen oxides such as nitric oxide is highly concentrated is discharged from the top of the device while the precipitated sulfur is extracted from the bottom. Such nitrogen oxides concentrated gas may be subjected to the above-mentioned process by which NO can be -` 110~289 converted into N2. Such treatment of the absorption medium may be conducted after or before the oxidizing step of the medium for a reuse of the medium.
It should be mentioned that according to the present invention since the high-boiling organic solvent is employed, it is possible to use the temperature of the absorption liquid, say, over the melting point of sulfur (120C), and hence, the fine particles of sulfur can be melted to form coarse particles which then settle down so as to be recovered as pure melted sulfur. Thus, the process of this invention is advantageous in that sulfur is recovered in the most desirable form while the loss of the liquor and the catalyst is prevented. In a conventional wet process for desulfurization of sulfur-con-taining gas, the precipitated sulfur is recovered by using a filter-press. However, with such filter-press, the water can-not be removed as much as over 60~/o. This fact can be easily ; understood from a simple calculation of the volume of gap among the particles of the sulfur. Thus, such process is dis-advantageous in that it results in degradation of sulfur re-covered as well as loss of alkaline, acid, organic solvent or even catalyst to be used in an absorption medium.
In addition, when hydrogen cyanide is contacted with sulfur of ordinary form, it hardly reacts with the sulfur, and hence, there is practically no conversion to thiocyanate.
In contrast, if sulfur is in the atomic state, hydrogen cyanide reacts with it very readily and it is easily converted to a thiocyanate. When the quinone or its derivative or quino-chelate compound of this invention is present, atomic sulfur is readily formed and in a particle size distribution in which the maximum particles size is within a range of from about 0.01 to about 2,u. As may be readily understood from this fact, sulfur is in a highly active state, and it reacts with hydrogen cyanide ` . 11~2~39 to form a thiocyanate as follows:
NCN + atomic S NCNS
An instance of the sulfur particle size distribution in the absorption liquid observed when the operation is con-tinued for 15 hours is as follows particle size (jU) amount of particles (%) - below 0.1 80 0.1 to 1 15 1 to 2 5 The oxidation-reduction state and the deposition of sulfur are provided in the following table with respect to typical quinone compounds for showing the effects of the pre-sent invention.
TABLE
E as measured at 25C State of Sulfur ~xidized Form (volt) Deposition o-benzoquinone 0.787 no sulfur precipitate, extreme formation of thionic acid 3-hydroxy-o-benzo- small amount of sulfur quinone 0.713 precipitate p-benzoquinone 0.699 "
1,4-naphthoquinone0.484 sulfur precipitate 9,10-anthraquinone0.154 no sulfur precipitate 1,2-naphthoquinone-0.628 sulfur precipitate
- 4-sulfonic acid 1,4-naphthoquinone-0.533 good precipitation of 2-sulfonic acid sulfur 1,4-naphthoquinone- - sulfur precipitate 2,3-dicarboxylic acid 2-hydroxy-1,4-naphtho- 0.351 "
quinone
quinone
5-hydroxy-1,4- 0.452 naphthoquinone 4-amino-1,2-naphtho-0.352 sulfur precipitate qulnone .
~10~2~39 .
TABLE (cont'd) E as measured at 25C State of Sulfur Oxidized Form (volt) ~eF,osition _ .
- 9,10-anthraquinone- 0.187 very slow and insuffic-2-sulfonic acid ient precipitation - of sulfur 1,2-anthraquinone- - "
4-sulfonic acid anthraquinone-2,6- 0.228 "
disulfonic acid l-hydroxy-9,10- 0.132 no sulfur precipitate anthraquinone Naphthoquinone or naphthodiquinone or the derivative therefrom as above listed per se serves as a catalytic com-ponent in an absorption medium although not so effective as the naphthoquino-chelate. Thus, as a modified embodiment of the invention, a gas which contains nitrogen oxides as well as hydrogen sulfide and/or sulfur dioxides and may contain hydro-gen cyanide may be absorbed in an absorption medium containing such quinone or quinone derivative and the diamine-chelate, wherein such diamine chelate has been externally prepared.
The absorption medium for use in the present inven-tion may contain other organic solvents such as glycerin, ethylene glycol, diethylene glycol, or a compound represented by the formula RO-(CH2)2-OH in which R is alkyl group having 1 to 4 carbon atoms, depending on the types and the amounts of the contaminants contained in the gas to be refined. With the use of such a solvent, the refining effect may be occasionally higher.
The present invention will be understood more readily with reference to the following examples. However, the exam-ples are intended to illustrate the invention and are not to be construed to limit the scope of the invention.
A naphthoquino-chelate was prepared by mixing 0.5 mol -- . 110C~2~39 of ammonium 1,4-naphthoquinone-2~sulfonate in 1 kl of water with 0.6 mol of the iron salt of the compound (I) as a chelat-ing agent precursor and aging for 2 hours. The solu~ion con-taining the naphthoquino-chelate thus obtained was added with ethylene-diamine and ethylene-diamine-tetraacetate to form an absorption medium according to the invention. In the medium ethylene-diamine was contained in the amount of l~/o by weight and ethylene-diamine-tetraacetate was contained in the amount of 10 mol/kl of the medium.
- 10 A glass tube having the inner diameter of 50 mm and the length of 1000 mm was packed with synthetic resin fillers - having the diameter of 15 mm. The absorption medium was sprinkled into the tube from the top of the tube while a gas to be treated was introduced from the bottom of the tube to flow in counter-current contact with the absorption medium.
The gas to be treated was composed of 1000 ppm of H2S, 500 ppm of S02, 300 ppm of No, 5% of 2 and the remainder of N2. The gas treatment was conducted at 60C and at pH of 8 with the flow rates of the gas and the absorption medium of 150 l/hr and 2 l/hr, respectively. As results, the percentages of the removal of H2S, S02 and N0 from the gas were 99.95%, 99.8% and 98%, respectively. During the operation, the formation of amine sulfanilate expressed by NH(SO3Na) was observed with - the increase of the amount of N0 absorbed.
.--An aqueous mixture of 5% of ethylene diamine, 5% of 2-ethoxyethanol and 5 mol of propylene-diamine-tetraacetate in 1 kl of the mixture was added with 0.5 mol of sodium 1,4-naphtho-quinone-2-sulfonate. The solution thus formed was mixed with the iron salt of the above-mentioned compound (I) in an amount of 0.6 mol in 1 kl of the solution and aged for 1.5 hours to obtain an absorption medium of the present invention.
ll(~G289 The gas treatment was carried out in the same manner as in Example 1 for the gas composed of H2S 1800 ppm, SO2 800 ppm, NO 280 ppm, 2 8%, CO2 15% and the remainder of N2 under the conditions of pH 6.7 at 40C, with the result that the percentage of H2S, SO2 and NO removal were 99.3%, 98% and 97% respectively.
A quino-chelate was prepared by mixing 1 mol of naphthodiquinone in 1 kl of water with 1 mol of ferrous citrate as a chelating precursor. The quino-chelate solution thus obtained was added (ethylene-diamine-tetraacetate)Fe++ in an - amount of 5% in the solution. With the absorption medium thus obtained, the gas composed of 20,000 ppm of H2S, 9850 ppm of SO2, 283 ppm of NO, 3% of 2~ 1% of HCN and the remainder of N2, was treated using the test tube as in Example 1 at 40C and pH 8Ø The result is that the percentages of H2S, S02, NO
and HCN removals were 99.1%, 98%, 97% and 98%, respectively.
The process of the present invention is effective in refining a gas which contains sulfur- and/or nitrogen-bearing compounds and will throw impediments in an industrial pro-cess and cause environmental pollution, such as coal gas, the waste gas from the Claus process or any other industrial waste gas.
~10~2~39 .
TABLE (cont'd) E as measured at 25C State of Sulfur Oxidized Form (volt) ~eF,osition _ .
- 9,10-anthraquinone- 0.187 very slow and insuffic-2-sulfonic acid ient precipitation - of sulfur 1,2-anthraquinone- - "
4-sulfonic acid anthraquinone-2,6- 0.228 "
disulfonic acid l-hydroxy-9,10- 0.132 no sulfur precipitate anthraquinone Naphthoquinone or naphthodiquinone or the derivative therefrom as above listed per se serves as a catalytic com-ponent in an absorption medium although not so effective as the naphthoquino-chelate. Thus, as a modified embodiment of the invention, a gas which contains nitrogen oxides as well as hydrogen sulfide and/or sulfur dioxides and may contain hydro-gen cyanide may be absorbed in an absorption medium containing such quinone or quinone derivative and the diamine-chelate, wherein such diamine chelate has been externally prepared.
The absorption medium for use in the present inven-tion may contain other organic solvents such as glycerin, ethylene glycol, diethylene glycol, or a compound represented by the formula RO-(CH2)2-OH in which R is alkyl group having 1 to 4 carbon atoms, depending on the types and the amounts of the contaminants contained in the gas to be refined. With the use of such a solvent, the refining effect may be occasionally higher.
The present invention will be understood more readily with reference to the following examples. However, the exam-ples are intended to illustrate the invention and are not to be construed to limit the scope of the invention.
A naphthoquino-chelate was prepared by mixing 0.5 mol -- . 110C~2~39 of ammonium 1,4-naphthoquinone-2~sulfonate in 1 kl of water with 0.6 mol of the iron salt of the compound (I) as a chelat-ing agent precursor and aging for 2 hours. The solu~ion con-taining the naphthoquino-chelate thus obtained was added with ethylene-diamine and ethylene-diamine-tetraacetate to form an absorption medium according to the invention. In the medium ethylene-diamine was contained in the amount of l~/o by weight and ethylene-diamine-tetraacetate was contained in the amount of 10 mol/kl of the medium.
- 10 A glass tube having the inner diameter of 50 mm and the length of 1000 mm was packed with synthetic resin fillers - having the diameter of 15 mm. The absorption medium was sprinkled into the tube from the top of the tube while a gas to be treated was introduced from the bottom of the tube to flow in counter-current contact with the absorption medium.
The gas to be treated was composed of 1000 ppm of H2S, 500 ppm of S02, 300 ppm of No, 5% of 2 and the remainder of N2. The gas treatment was conducted at 60C and at pH of 8 with the flow rates of the gas and the absorption medium of 150 l/hr and 2 l/hr, respectively. As results, the percentages of the removal of H2S, S02 and N0 from the gas were 99.95%, 99.8% and 98%, respectively. During the operation, the formation of amine sulfanilate expressed by NH(SO3Na) was observed with - the increase of the amount of N0 absorbed.
.--An aqueous mixture of 5% of ethylene diamine, 5% of 2-ethoxyethanol and 5 mol of propylene-diamine-tetraacetate in 1 kl of the mixture was added with 0.5 mol of sodium 1,4-naphtho-quinone-2-sulfonate. The solution thus formed was mixed with the iron salt of the above-mentioned compound (I) in an amount of 0.6 mol in 1 kl of the solution and aged for 1.5 hours to obtain an absorption medium of the present invention.
ll(~G289 The gas treatment was carried out in the same manner as in Example 1 for the gas composed of H2S 1800 ppm, SO2 800 ppm, NO 280 ppm, 2 8%, CO2 15% and the remainder of N2 under the conditions of pH 6.7 at 40C, with the result that the percentage of H2S, SO2 and NO removal were 99.3%, 98% and 97% respectively.
A quino-chelate was prepared by mixing 1 mol of naphthodiquinone in 1 kl of water with 1 mol of ferrous citrate as a chelating precursor. The quino-chelate solution thus obtained was added (ethylene-diamine-tetraacetate)Fe++ in an - amount of 5% in the solution. With the absorption medium thus obtained, the gas composed of 20,000 ppm of H2S, 9850 ppm of SO2, 283 ppm of NO, 3% of 2~ 1% of HCN and the remainder of N2, was treated using the test tube as in Example 1 at 40C and pH 8Ø The result is that the percentages of H2S, S02, NO
and HCN removals were 99.1%, 98%, 97% and 98%, respectively.
The process of the present invention is effective in refining a gas which contains sulfur- and/or nitrogen-bearing compounds and will throw impediments in an industrial pro-cess and cause environmental pollution, such as coal gas, the waste gas from the Claus process or any other industrial waste gas.
Claims
1. A process for refining a gas which contains hydrogen sulfide, sulfur oxides and nitrogen oxides and may contain hydrogen cyanide as contaminants, which process comprises con-tacting said gas with absorption medium to absorb said contami-nants in said absorption medium- said absorption medium con-taining as catalytic component 0.01 to 500 mole/kl of specified naphthoquino-chelate prepared by mixing (A) naphthoquinone or a derivative thereof of the general formula or naphthodiquinone or a derivative thereof the general formula in which X represents hydrogen atom, hydroxyl group, a lower alkyl group, a lower alkoxy group, sulfonic group (-SO3H), car-boxylic group (-COOH), an alkaline metal or alkaline earth metal salt of sulfonic or carboxylic group (such as -SO3Na, -COONa), thioglycol group (-S-CH2-COOH) or thiol group (-SR in which R
is a lower alkyl group) with (B) a precursor of a chelating agent which is selected from the group consisting of the reac-tion product of a metal selected from the group consisting of the metals of groups V, VI, VII and VIII in the fourth period of the Periodic Table, arsenic and selenium with an acid selected from the group consisting of oxalic, citric, tartaric and glu-taric acids, said chelating agent precursor being present in an amount of from about 0.01 to about 50% by weight based on the quinone compound employed and aging the mixture of (A) and (B) to form a naphthoquino-chelate compound, the quinones and quino-chelates having high solubitily in water or an organic solvent, and their oxydation reduction potential being 0.3 to 0.8 volts measured at 25°C: and further containing as solvent specified diamine selected from among cyclohexadiamine and diamine having the general formula NH2(CnH2n)NH2 in which n is 2, 3 or 4 and mono-, di-, tri- or tetra-acetate, or mono-, di- tri- or tetra-propionate, or mono-, di-, tri- or tetra-buthylate of said diamine, and treating the absorption medium which has absorbed said contaminants for obtaining sulfur from hydrogen sulfide and sulfur oxides and thiocyanate from hydrogen cyanide while producing a gas having high nitrogen oxides concentration.
is a lower alkyl group) with (B) a precursor of a chelating agent which is selected from the group consisting of the reac-tion product of a metal selected from the group consisting of the metals of groups V, VI, VII and VIII in the fourth period of the Periodic Table, arsenic and selenium with an acid selected from the group consisting of oxalic, citric, tartaric and glu-taric acids, said chelating agent precursor being present in an amount of from about 0.01 to about 50% by weight based on the quinone compound employed and aging the mixture of (A) and (B) to form a naphthoquino-chelate compound, the quinones and quino-chelates having high solubitily in water or an organic solvent, and their oxydation reduction potential being 0.3 to 0.8 volts measured at 25°C: and further containing as solvent specified diamine selected from among cyclohexadiamine and diamine having the general formula NH2(CnH2n)NH2 in which n is 2, 3 or 4 and mono-, di-, tri- or tetra-acetate, or mono-, di- tri- or tetra-propionate, or mono-, di-, tri- or tetra-buthylate of said diamine, and treating the absorption medium which has absorbed said contaminants for obtaining sulfur from hydrogen sulfide and sulfur oxides and thiocyanate from hydrogen cyanide while producing a gas having high nitrogen oxides concentration.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA280,735A CA1100289A (en) | 1977-06-16 | 1977-06-16 | Refining a gas containing hydrogen sulfide, nitrogen oxides and other contaminants |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA280,735A CA1100289A (en) | 1977-06-16 | 1977-06-16 | Refining a gas containing hydrogen sulfide, nitrogen oxides and other contaminants |
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| Publication Number | Publication Date |
|---|---|
| CA1100289A true CA1100289A (en) | 1981-05-05 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA280,735A Expired CA1100289A (en) | 1977-06-16 | 1977-06-16 | Refining a gas containing hydrogen sulfide, nitrogen oxides and other contaminants |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1100289A (en) |
-
1977
- 1977-06-16 CA CA280,735A patent/CA1100289A/en not_active Expired
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| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |