Patent US4622212A successfully refreshed from Google Patents.
US4622212A
Expired / Lapsed
US
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Hydrogen sulfide removal
Assignee: GAS TECHNOLOGY PRODUCTS LLC
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Filing: 1985-06-25
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Granted: 1986-11-11
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Expires: 2005-06-25
Abstract
Abstract In a cyclic hydrogen sulfide oxidation-catalyst regeneration process using an aqueous chelated polyvalent metal catalyst solution, excessive degradation of the aminopolycarboxylic acid chelating agent is prevented by incorporating in the solution an effective amount of a stabilizing agent capable of retarding or preventing rupture of nitrogen-carbon bonds in the chelating agent during oxidative regeneration of the catalyst solution. Alkaline thiosulfates are the preferred stabilizing agents. Particularly good results are obtained using an alkaline thiosulfate stabilizer in a catalyst solution comprising the dimer form of the NTA-iron complex.
Inventors
- 👤 Derek McManus
- 👤 Frederick R. Kin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 21:02
CPC Classifications
B; B01; B01D; B01D53/00; B01D53/34; B01D53/46; B01D53/48; B01D53/52; B01D53/14; B01D53/1493; C; C01; C01B; C01B17/00; C01B17/02; C01B17/04; C01B17/05; Y; Y02; Y02P; Y02P20/00; Y02P20/50; Y02P20/584
Claims Analysis
Total Claims: 45
Claim 1
Independent Claim
241 words
A method of preventing excessive degradation of chelating agent during prolonged continuous operation of a hydrogen sulfide removal process using a chelated polyvalent metal catalyst solution wherein an aqueous solution of a polyvlent metal chelated with at least one chelating agent comprising an aminopolycarboxylic acid is contacted with a hydrogen sulfide-containing fluid stream to effect oxidation of the hydrogen sulfide to elemental sulfur and concomitant reduction of said polyvalent metal from its higher valence state to its lower valence state, and wherein the catalyst solution is regenerated by contacting said solution with an oxygen-containing gas to oxidize said polyvalent metal from its lower valence state to its higher valence state, and wherein said chelating agent is susceptible to rapid progressive degradation by rupture of nitrogen-carbon bonds during the process, thereby necessitating addition of replacement chelating agent, said method comprising the steps of: incorporating in said catalyst solution an effective concentration of a stabilizing agent sufficient to retard the rate of degradation or to prevent degradation of said aminopolycarboxylic acid chelating agent during operation of the process, said stabilizing agent being selected from the group consisting of alkaline thiosulfates and dihydroxy alcohols having 2 to 3 carbon atoms; and maintaining said effective concentration of said stabilizing agent in said catalyst solution substantially throughout the operation of the process for at least about 170 hours by incorporating additional amounts of stabilizing agent in said solution or withdrawing used solution if and when required.
Claim 2
Independent Claim
241 words
A method of preventing excessive degradation of chelating agent during prolonged continuous operation of a hydrogen sulfide removal process using a chelated polyvalent metal catalyst solution wherein an aqueous solution of a polyvlent metal chelated with at least one chelating agent comprising an aminopolycarboxylic acid is contacted with a hydrogen sulfide-containing fluid stream to effect oxidation of the hydrogen sulfide to elemental sulfur and concomitant reduction of said polyvalent metal from its higher valence state to its lower valence state, and wherein the catalyst solution is regenerated by contacting said solution with an oxygen-containing gas to oxidize said polyvalent metal from its lower valence state to its higher valence state, and wherein said chelating agent is susceptible to rapid progressive degradation by rupture of nitrogen-carbon bonds during the process, thereby necessitating addition of replacement chelating agent, said method comprising the steps of: incorporating in said catalyst solution an effective concentration of a stabilizing agent sufficient to retard the rate of degradation or to prevent degradation of said aminopolycarboxylic acid chelating agent during operation of the process, said stabilizing agent being selected from the group consisting of alkaline thiosulfates and dihydroxy alcohols having 2 to 3 carbon atoms; and maintaining said effective concentration of said stabilizing agent in said catalyst solution substantially throughout the operation of the process for at least about 170 hours by incorporating additional amounts of stabilizing agent in said solution or withdrawing used solution if and when required.
Claim 3
Dependent Claim
81 words
The process of claim 1 further characterized in that a nitrogen bond in the chelate complex is freed during reduction of the polyvalent metal to its lower valence state, thereby providing a nitrogen atom with an unpaired electron, and wherein said stabilizing agent is capable of complexing with the chelating agent and sharing said unpaired electron so as to retard or prevent rupture of the bond between said nitrogen atom and a carbon atom during subsequent regeneration of the catalyst solution.
Claim 4
Independent Claim
225 words
A method of preventing excessive degradation of chelating agent during prolonged continuous operation of a hydrogen sulfide removal process using a chelated polyvalent metal catalyst solution wherein an aqueous solution of a polyvalent metal chelated with at least one chelating agent comprising an aminopolycarboxylic acid is contacted with a hydrogen sulfide-containing fluid stream to effect oxidation of the hydrogen sulfide to elemental sulfur and concomitant reduction of said polyvalent metal from its higher valence state to its lower valence state, and wherein the catalyst solution is regenerated by contacting said solution with an oxygen-containing gas to oxidize said polyvalent metal from its lower valence state to its higher valence state, and wherein said chelating agent is susceptible to rapid progressive degradation by rupture of carbon-nitrogen bonds during the process, thereby necessitating addition of replacement chelating agent, said method comprising the steps of: incorporating in said catalyst solution an effective concentration of an alkaline thiosulfate stabilizing agent sufficient to retard the rate of degradation or to prevent degradation of said aminopolycarboxylic acid chelating agent during operation of the process; and maintaining said effective concentration of said alkaline thiosulfate stabilizing agent in said catalyst solution substantially throughout the operation of the process for at least about 170 hours by incorporating additional amounts of said alkaline thiosulfate in said solution or withdrawing used solution if and when required.
Claim 5
Independent Claim
225 words
A method of preventing excessive degradation of chelating agent during prolonged continuous operation of a hydrogen sulfide removal process using a chelated polyvalent metal catalyst solution wherein an aqueous solution of a polyvalent metal chelated with at least one chelating agent comprising an aminopolycarboxylic acid is contacted with a hydrogen sulfide-containing fluid stream to effect oxidation of the hydrogen sulfide to elemental sulfur and concomitant reduction of said polyvalent metal from its higher valence state to its lower valence state, and wherein the catalyst solution is regenerated by contacting said solution with an oxygen-containing gas to oxidize said polyvalent metal from its lower valence state to its higher valence state, and wherein said chelating agent is susceptible to rapid progressive degradation by rupture of carbon-nitrogen bonds during the process, thereby necessitating addition of replacement chelating agent, said method comprising the steps of: incorporating in said catalyst solution an effective concentration of an alkaline thiosulfate stabilizing agent sufficient to retard the rate of degradation or to prevent degradation of said aminopolycarboxylic acid chelating agent during operation of the process; and maintaining said effective concentration of said alkaline thiosulfate stabilizing agent in said catalyst solution substantially throughout the operation of the process for at least about 170 hours by incorporating additional amounts of said alkaline thiosulfate in said solution or withdrawing used solution if and when required.
Claim 6
Dependent Claim
29 words
The process of claim 3, wherein said alkaline thiosulfate is incorporated in the initial operating solution and is present at said effective concentration throughout the operation of the process.
Claim 7
Dependent Claim
29 words
The process of claim 3, wherein said alkaline thiosulfate is selected from the group consisting of alkali metal thiosulfates, alkaline earth metal thiosulfates, ammonium thiosulfate, and thiosulfate ion precursors.
Claim 8
Dependent Claim
26 words
The process of claim 3, wherein said polyvalent metal is iron and the iron content of said solution is from about 5 to about 5000 ppm.
Claim 9
Dependent Claim
31 words
The process of claim 3, wherein said chelating agent is selected from the group consisting of monoaminopolycarboxylic acids, polyaminopolycarboxylic acids, polyaminoalkyl polycarboxylic acids, polyaminohydroxyalkyl polycarboxylic acids, and their alkali metal salts.
Claim 10
Dependent Claim
14 words
The process of claim 3, wherein said solution also contains a polyhydroxy chelating agent.
Claim 11
Dependent Claim
22 words
The process of claim 3, wherein oxidation of hydrogen sulfide and regeneration of the catalyst solution are effected in separate reaction zones.
Claim 12
Dependent Claim
23 words
The process of claim 3, wherein the concentration of thiosulfate in said solution is from about 3 to about 300 g·L -1 .
Claim 13
Dependent Claim
23 words
The process of claim 3, wherein the concentration of thiosulfate in said solution is from about 10 to about 50 g·L -1 .
Claim 14
Dependent Claim
15 words
The process of claim 3, wherein said catalyst solution has a neutral or alkaline pH.
Claim 15
Dependent Claim
12 words
The process of claim 8, wherein said polyhydroxy chelating agent comprises sorbitol.
Claim 16
Independent Claim
225 words
A method of preventing excessive degradation of chelating agent during prolonged operation of a hydrogen sulfide removal process using a chelated polyvalent metal catalyst solution wherein an aqueous solution of a polyvalent metal chelated with at least one chelating agent comprising nitrilotriacetic acid is contacted with a hydrogen sulfide-containing fluid stream to effect oxidation of the hydrogen sulfide to elemental sulfur and concomitant reduction of said polyvalent metal from its higher valence state to its lower valence state, and wherein the catalyst solution is regenerated by contacting said solution with an oxygen-containing gas to oxidize said polyvalent metal from its lower valence state to its higher valence state, and wherein said nitrilotriacetic acid chelating agent is susceptible to rapid progressive oxidation by rupture of nitrogen-carbon bonds during the process, thereby necessitating addition of replacement chelating agent, said method comprising the steps of: incorporating in said catalyst solution an effective concentration of an alkaline thiosulfate stabilizing agent sufficient to retard the rate of degradation or to prevent degradation of said nitrilotriacetic acid chelating agent during operation of the process; and maintaining said effective concentration of said alkaline thiosulfate stabilizing agent in said catalyst solution substantially throughout the operation of the process for at least about 170 hours by incorporating additional amounts of said alkaline thiosulfate in said solution or withdrawing used solution if and when required.
Claim 17
Independent Claim
225 words
A method of preventing excessive degradation of chelating agent during prolonged operation of a hydrogen sulfide removal process using a chelated polyvalent metal catalyst solution wherein an aqueous solution of a polyvalent metal chelated with at least one chelating agent comprising nitrilotriacetic acid is contacted with a hydrogen sulfide-containing fluid stream to effect oxidation of the hydrogen sulfide to elemental sulfur and concomitant reduction of said polyvalent metal from its higher valence state to its lower valence state, and wherein the catalyst solution is regenerated by contacting said solution with an oxygen-containing gas to oxidize said polyvalent metal from its lower valence state to its higher valence state, and wherein said nitrilotriacetic acid chelating agent is susceptible to rapid progressive oxidation by rupture of nitrogen-carbon bonds during the process, thereby necessitating addition of replacement chelating agent, said method comprising the steps of: incorporating in said catalyst solution an effective concentration of an alkaline thiosulfate stabilizing agent sufficient to retard the rate of degradation or to prevent degradation of said nitrilotriacetic acid chelating agent during operation of the process; and maintaining said effective concentration of said alkaline thiosulfate stabilizing agent in said catalyst solution substantially throughout the operation of the process for at least about 170 hours by incorporating additional amounts of said alkaline thiosulfate in said solution or withdrawing used solution if and when required.
Claim 18
Dependent Claim
23 words
The process of claim 14, wherein the mole ratio of nitrilotriacetic acid to polyvalent metal in said solution is at least about 2:1.
Claim 19
Dependent Claim
44 words
The process of claim 14, wherein said polyvalent metal is iron and the mole ratio of nitrilotriacetic acid to iron in said solution is at least about 2:1, whereby the iron is predominantly chelated with two moles of nitrilotriacetic acid per mole of iron.
Claim 20
Dependent Claim
29 words
The process of claim 16, wherein said alkaline thiosulfate is selected from the group consisting of alkali metal thiosulfates, alkaline earth metal thiosulfates, ammonium thiosulfate, and thiosulfate ion precursors.
Claim 21
Dependent Claim
19 words
The process of claim 16, wherein the mole ratio of thiosulfate to nitrilotriacetic acid is at least about 1:1.
Claim 22
Dependent Claim
19 words
The process of claim 16, wherein said catalyst solution comprises from about 5 to about 5000 ppm of iron.
Claim 23
Dependent Claim
23 words
The process of claim 16, wherein the concentration of thiosulfate in said solution is from about 3 to about 300 g·L -1 .
Claim 24
Dependent Claim
23 words
The process of claim 16, wherein the concentration of thiosulfate in said solution is from about 10 to about 50 g·L -1 .
Claim 25
Dependent Claim
60 words
The process of claim 16, wherein said catalyst solution comprises about 1000 ppm of iron, said thiosulfate is sodium or ammonium thiosulfate in an amount sufficient to provide a mole ratio of thiosulfate to iron of about 3,5:1, and said solution also contains sorbitol in an amount sufficient to provide a mole ratio of sorbitol to iron of about 0.5:1.
Claim 26
Dependent Claim
29 words
The process of claim 14, wherein said alkaline thiosulfate is incorporated in the initial operating solution and is present at said effective concentration throughout the operation of the process.
Claim 27
Dependent Claim
22 words
The process of claim 14, wherein oxidation of hydrogen sulfide and regeneration of the catalyst solution are effected in separate reaction zones.
Claim 28
Independent Claim
243 words
A method of preventing excessive degradation of chelating agent during prolonged continuous operation of a hydrogen sulfide removal process using a chelated polyvalent metal catalyst solution wherein an aqueous solution of a polyvalent metal chelated with at least one chelating agent comprising an aminopolycarboxylic acid is contacted with a hydrogen sulfide-containing fluid stream to effect oxidation of the hydrogen sulfide to elemental sulfur and concomitant reduction of said polyvalent metal from its higher valence state to its lower valence state, and wherein the catalyst solution is regenerated by contacting said solution with an oxygen-containing gas to oxidize said polyvalent metal from its lower valence state to its higher valence state, and wherein said chelating agent is susceptible to rapid progressive degradation by rupture of carbon-nitrogen bonds during the process, thereby necessitating addition of replacement chelating agent, said method comprising the steps of: incorporating in said catalyst solution an effective concentration of an aliphatic alcohol stabilizing agent sufficient to retard the rate of degradation or to prevent degradation of said aminopolycarboxylic acid chelating agent during operation of the process, said aliphatic alcohol being selected from the group consisting of dihydroxy alcohols having 2 to 3 carbon atoms; and maintaining said effective concentration of said aliphatic alcohol stabilizing agent in said catalyst solution substantially throughout the operation of the process for at least about 170 hours by incorporating additional amounts of said aliphatic alcohol in said solution or withdrawing used solution if and when required.
Claim 29
Independent Claim
243 words
A method of preventing excessive degradation of chelating agent during prolonged continuous operation of a hydrogen sulfide removal process using a chelated polyvalent metal catalyst solution wherein an aqueous solution of a polyvalent metal chelated with at least one chelating agent comprising an aminopolycarboxylic acid is contacted with a hydrogen sulfide-containing fluid stream to effect oxidation of the hydrogen sulfide to elemental sulfur and concomitant reduction of said polyvalent metal from its higher valence state to its lower valence state, and wherein the catalyst solution is regenerated by contacting said solution with an oxygen-containing gas to oxidize said polyvalent metal from its lower valence state to its higher valence state, and wherein said chelating agent is susceptible to rapid progressive degradation by rupture of carbon-nitrogen bonds during the process, thereby necessitating addition of replacement chelating agent, said method comprising the steps of: incorporating in said catalyst solution an effective concentration of an aliphatic alcohol stabilizing agent sufficient to retard the rate of degradation or to prevent degradation of said aminopolycarboxylic acid chelating agent during operation of the process, said aliphatic alcohol being selected from the group consisting of dihydroxy alcohols having 2 to 3 carbon atoms; and maintaining said effective concentration of said aliphatic alcohol stabilizing agent in said catalyst solution substantially throughout the operation of the process for at least about 170 hours by incorporating additional amounts of said aliphatic alcohol in said solution or withdrawing used solution if and when required.
Claim 30
Dependent Claim
11 words
The process of claim 25, wherein said polyvalent metal is iron.
Claim 31
Dependent Claim
31 words
The process of claim 25, wherein said chelating agent is selected from the group consisting of monoaminopolycarboxylic acids, polyaminopolycarboxylic acids, polyaminoalkyl polycarboxylic acids, polyaminohydroxyalkyl polycarboxylic acids, and their alkali metal salts.
Claim 32
Dependent Claim
12 words
The process of claim 25, wherein said chelating agent comprises nitrilotriacetic acid.
Claim 33
Dependent Claim
14 words
The process of claim 25, wherein said solution also contains a polyhydroxy chelating agent.
Claim 34
Dependent Claim
12 words
The process of claim 25, wherein said stabilizing agent comprises ethylene glycol.
Claim 35
Dependent Claim
29 words
The process of claim 25, wherein said aliphatic alcohol is incorporated in the initial operating solution and is present at said effective concentration throughout the operation of the process.
Claim 36
Dependent Claim
22 words
The process of claim 25, wherein oxidation of hydrogen sulfide and regeneration of the catalyst solution are effected in separate reaction zones.
Claim 37
Dependent Claim
24 words
The process of claim 25, wherein the concentration of said alcohol in said solution is from about 20 to about 100 g·L -1 .
Claim 38
Dependent Claim
120 words
A redox catalyst composition for use in a process for removing hydrogen sulfide by oxidation to elemental sulfur comprising a neutral or alkaline aqueous solution of iron chelated with nitrilotriacetic acid, said nitrilotriacetic acid being susceptible to rapid progressive degradation by rupture of carbon-nitrogen bonds during the process, the mole ratio of nitrilotriacetic acid to iron being at least about 2:1 so that the iron is predominantly chelated with two moles of nitrilotriacetic acid per mole of iron, and said solution also containing an effective concentration of an alkaline thiosulfate stabilizing agent sufficient to retard the rate of degradation or to prevent degradation of the nitrilotriacetic acid chelating agent during operation of the process for at least about 170 hours.
Claim 39
Dependent Claim
120 words
A redox catalyst composition for use in a process for removing hydrogen sulfide by oxidation to elemental sulfur comprising a neutral or alkaline aqueous solution of iron chelated with nitrilotriacetic acid, said nitrilotriacetic acid being susceptible to rapid progressive degradation by rupture of carbon-nitrogen bonds during the process, the mole ratio of nitrilotriacetic acid to iron being at least about 2:1 so that the iron is predominantly chelated with two moles of nitrilotriacetic acid per mole of iron, and said solution also containing an effective concentration of an alkaline thiosulfate stabilizing agent sufficient to retard the rate of degradation or to prevent degradation of the nitrilotriacetic acid chelating agent during operation of the process for at least about 170 hours.
Claim 40
Dependent Claim
35 words
The catalyst composition of claim 34, wherein the iron content of said solution is from about 5 to about 5000 ppm and the mole ratio of thiosulfate to nitrilotriacetic acid is at least about 1:1.
Claim 41
Dependent Claim
23 words
The catalyst composition of claim 34, wherein the concnetration of said alkaline thiosulfate is from about 3 to about 300 g·L -1 .
Claim 42
Dependent Claim
23 words
The catalyst composition of claim 34, wherein the concentration of said alkaline thiosulfate is from about 10 to about 50 g·L -1 .
Claim 43
Dependent Claim
63 words
The catalyst composition of claim 34, wherein the iron content of said solution is about 1000 ppm, said alkaline thiosulfate is sodium or ammonium thiosulfate in an amount sufficient to provide a mole ratio of thiosulfate to iron of about 3.5:1, and said solution also contains sorbitol in an amount sufficient to provide a mole ratio of sorbitol to iron of about 0.5:1.
Claim 44
Dependent Claim
15 words
The catalyst composition of claim 34, wherein said solution also contains a polyhydroxy chelating agent.
Claim 45
Dependent Claim
13 words
The catalyst composition of claim 39, wherein said polyhydroxy chelating agent comprises sorbitol.
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