Oxidative removal of hydrogen sulfide from gaseous streams

Claim 2

A process for the removal of hydrogen sulfide from gaseous streams which comprises: contacting a gaseous stream containing hydrogen sulfide with an aqueous solution of ferric ion chelated with an aminopolycarboxylic acid chelating agent at a pH of about 3.5 to 5, whereby hydrogen sulfide is oxidized to elemental sulfur and chelated ferric ion is reduced to chelated ferrous ion, the total concentration of ferrous and ferric iron in the aqueous solution being more than about 0.1 mole per liter of solution and the aqueous solution containing a salt selected from the group consisting of an ammonium salt of a strong mineral acid and an aliphatic, alicyclic, or heterocyclic primary or secondary amine salt of a strong mineral acid, said salt present in a sufficient proportion to maintain the thus formed chelated ferrous ion in solution.

Claim 3

A process as recited in claim 1 in which the aminopolycarboxcylic acid chelating agent is represented by the formula ##STR2## wherein from 2 to 4 of the groups X are lower alkyl carboxylic acid groups, from 0 to 2 of the groups X are selected from the group consisting of lower alkyl or hydroxyalkyl groups and ##STR3## and R is a divalent organic group.

Claim 4

The process as recited in claim 1 in which the aminopolycarboxylic acid chelating agent is represented by the formula (A).sub.3-n --N--X.sub.n wherein n is 2 or 3; X is a lower alkyl caroboxylic acid group; and A is a lower alkyl or hydroxyalkyl group.

Claim 5

A process as recited in claim 1 in which the total ferrous and ferric ion concentration of the solution is between about 0.5 and about 1.0 mole per liter.

Claim 6

A process as recited in claim 1 wherein the amine is a mono- or di- lower alkyl or nyaroxyalkyl amine.

Claim 7

A process as recited in claim 1 wherein the amine is a cycloalkyl amine.

Claim 8

A process as recited in claim 1 wherein the amine is a lower alkylene polyamine.

Claim 9

A process as recited in claim 7 wherein the amine is triethylenetetramine.

Claim 10

A process as recited in claim 1 wherein the gaseous stream also contains alkyl mercaptans and the mercaptans are removed from the gaseous stream and are converted to alkyl disulfides in the aqueous solution.

Claim 11

A process as recited in claim 1 wherein chelated ferrous ion is oxidized to chelated ferric ion by contacting the aqueous solution with a gas containing elemental oxygen.

Claim 12

A process as recited in claim 10 wherein the aqueous solution is contacted with a gas stream containing both hydrogen sulfide and oxygen.

Claim 13

A process as recited in claim 1 wherein the amino polycarboxylic acid is selected from the group consisting of ethylenediamine tetraacetic acid, 1,2-diaminocyclohexane-N,N-tetracetic acid, diethylenetriamine pentaacetic acid, N-hydroxyethyl ethylenediamine triacetic acid, diglycine, hydroxyethyldiglycine, hydroxypropyldiglycine, 1,2-propylenediamine tetraacetic acid, 1,3-propylenediamine tetraacetic acid, and 1,2-diaminocyclohexane-N,N-tetraacetic acid.

Claim 14

A process as recited in claim 1 wherein the orgainc amine is selected from the group consisting of methylamine, ethylamine, propylamine, butylamine, isobutylamine, tertiary-butylamine, secondary-butylamine, dimethylamine, diethylamine, ethanolamine, diethanolamine, propanolamine, cyclopentylamine, cyclohexylamine, morpholine, piperidine, ethylenediamine, diethylenetriamine, triethylenetetramine, 1,2-propylenediamine, and 1,3-propylenediamine.

Claim 15

A process for the removal of hydrogen sulfide form gaseous streams which comprises: contacting a gaseous stream containing hydrogen sulfide with an aqueous solution of ferric ion chelated with nitrilotriacetic acid at a pH of about 3.5 to 5, whereby hydrogen sulfide is oxidized to elemental sulfur and chelated ferric ion is reduced to chelated ferrous ion, the total concentration of ferrous ion and ferric ion in the solution being in the range of about 0.5 to 1.0 mole per liter, the solution containing a salt selected from the group consisting of an ammonium salt of a strong mineral acid present in a concentration of at least about one mole per mole of the thus formed chelated ferrous ion, an aliphatic, alicyclic or heterocyclic primary or secondary organic monoamine salt of a strong mineral acid and present in a concentration of at least about 0.6 mole per mole of the thus formed ferrous ion and an aliphatic, alicyclic or heterocyclic primary or secondary organic polyamine salt of a strong mineral acid present in a concentration of at least about 0.3 mole per mole of the bus formed chelated ferrous ion.

Claim 16

A process for the removal of hydrogen sulfide form gaseous streams which comprises: contacting a gaseous stream containing hydrogen sulfide with an aqueous solution of ferric ion chelated with nitrilotriacetic acid at a pH of about 3.5 to 5, whereby hydrogen sulfide is oxidized to elemental sulfur and chelated ferric ion is reduced to chelated ferrous ion, the total concentration of ferrous ion and ferric ion in the solution being in the range of about 0.5 to 1.0 mole per liter, the solution containing a salt selected from the group consisting of an ammonium salt of a strong mineral acid present in a concentration of at least about one mole per mole of the thus formed chelated ferrous ion, an aliphatic, alicyclic or heterocyclic primary or secondary organic monoamine salt of a strong mineral acid and present in a concentration of at least about 0.6 mole per mole of the thus formed ferrous ion and an aliphatic, alicyclic or heterocyclic primary or secondary organic polyamine salt of a strong mineral acid present in a concentration of at least about 0.3 mole per mole of the bus formed chelated ferrous ion.

Claim 17

A process as recited in claim 14 wherein the aqueous solution containing chelated ferrous ion is contacted with a gas containing elemental oxygen, whereby chelated ferrous ion is oxidized to chelated ferric ion.

Claim 18

A process as recited in claim 15 wherein the polyamine is triethylenetetramine.

Claim 19

A process as recited in claim 14 wherein the gaseous stream also contains alkyl mercaptans and the mercaptans are removed from the gaseous stream and converted to alkyl disulfides in the aqueous solution.

Claim 20

A process as recited in claim 15 wherein the aqueous solution is contacted with a gas stream containing both hydrogen sulfide and oxygen.

Claim 21

A process as recited in claim 14 wherein the organic amine is selected from the group consisting of methylamine, ethylamine, propylamine, butylamine, isobutylamine, tertiary-butylamine, secondary-butylamine, dimethylamine, diethylamine, ethanolamine, diethanolamine, propanolamine, cyclopentylamine, cyclohexylamine, morpholine, piperidine, ethylenediamine, diethylenetriamine, triethylenetetramine, 1,2-propylenediamine, and 1,3-propylenediamine.

Claim 22

A process for the removal of hydrogen sulfide from gaseous streams which comprises: contacting a gaseous stream containing hydrogen sulfide with an aqueous solution of ferric ion chelated with nitrilotriacetic acid at a pH of about 3.5 to 5, whereby hydrogen sulfide is oxidized to elemental sulfur and chelated ferric ion is reduced to chelated ferrous ion, the total concentration of ferrous and ferric iron in the aqueous solution being more than about 0.1 mole per liter of solution, the aqueous solution containing a salt selected from the group consisting of an ammonium salt of a strong mineral acid and an aliphtic, alicyclic, or heterocyclic primary or secondary amine salt of a strong mineral acid, said salt being present in a sufficient proportion to maintain the thus formed chelated ferrous ion in solution.

Claim 23

A process for the removal of hydrogen sulfide from gaseous streams which comprises: contacting a gaseous stream containing hydrogen sulfide with an aqueous solution of ferric ion chelated with nitrilotriacetic acid at a pH of about 3.5 to 5, whereby hydrogen sulfide is oxidized to elemental sulfur and chelated ferric ion is reduced to chelated ferrous ion, the total concentration of ferrous and ferric iron in the aqueous solution being more than about 0.1 mole per liter of solution, the aqueous solution containing a salt selected from the group consisting of an ammonium salt of a strong mineral acid and an aliphtic, alicyclic, or heterocyclic primary or secondary amine salt of a strong mineral acid, said salt being present in a sufficient proportion to maintain the thus formed chelated ferrous ion in solution.

Claim 24

A process as recited in claim 20 wherein the aqueous solution containing chelated ferrous ion is contacted with a gas containing elemental oxygen, whereby chelated ferrous ion is oxidized to chelated ferric ion.

Claim 25

A process as recited in claim 21 wherein the aqueous solution is contacted with a gas stream containing both hydrogen sulfide and oxygen.

Claim 26

A process for the removal of hydrogen sulfide from gaseous streams which comprises: contacting a gaseous stream containing hydrogen sulfide with an aqueous solution of ferric ion chelated with an aminopolycarboxylic acid chelating agent at a pH of about 3.5 to 5, whereby hydrogen sulfide is oxidized to elemental suflur and chelated ferric ion is reduced to chelated ferrous ion, the total concentration of ferrous and ferric iron in the aqueous solution being more than about 0.1 mole liter of solution and the aqueous solution containing a salt selected from the group consisting of a sulfate chloride or nitrate salt of ammonia or an aliphatic, alicyclic, or heterocyclic primary or secondary amine present in a sufficient proportion to maintain the thus formed chelated ferrous ion in solution.

Claim 27

A process for the removal of hydrogen sulfide from gaseous streams which comprises: contacting a gaseous stream containing hydrogen sulfide with an aqueous solution of ferric ion chelated with an aminopolycarboxylic acid chelating agent at a pH of about 3.5 to 5, whereby hydrogen sulfide is oxidized to elemental suflur and chelated ferric ion is reduced to chelated ferrous ion, the total concentration of ferrous and ferric iron in the aqueous solution being more than about 0.1 mole liter of solution and the aqueous solution containing a salt selected from the group consisting of a sulfate chloride or nitrate salt of ammonia or an aliphatic, alicyclic, or heterocyclic primary or secondary amine present in a sufficient proportion to maintain the thus formed chelated ferrous ion in solution.

Claim 28

A process as recited in claim 23 wherein the aqueous solution containing chelated ferrous ion is contacted with a gas containing elemental oxygen, whereby chelated ferrous ion is oxidized to chelated ferric ion.

Claim 29

A process as recited in claim 24 wherein the aqueous solution is contacted with a gas stream containing both hydrogen sulfide and oxygen.

Claim 30

A process for the removal of hydrogen sulfide from gaseous streams which comprises: contacting a gaseous stream containing hydrogen sulfide with an aqueous solution of ferric ion chelated with nitrilotriacetic acid at a pH of about 3.5 to 5, whereby hydrogen sulfide is oxidized to elemental sulfur and chelated ferric ion is reduced to chelated ferrous ion, the total concentration of ferrous and ferric iron in the aqueous solution being more than about 0.1 mole per liter of solution and the aqueous solution containing a salt selected from the group consisting of a sulfate, chloride, or nitrate salt of ammonia or an aliphatic, alicyclic, or heterocyclic primary or secondary amine present in a sufficient proportion to maintain the thus formed chelated ferrous ion in solution.

Claim 31

A process for the removal of hydrogen sulfide from gaseous streams which comprises: contacting a gaseous stream containing hydrogen sulfide with an aqueous solution of ferric ion chelated with nitrilotriacetic acid at a pH of about 3.5 to 5, whereby hydrogen sulfide is oxidized to elemental sulfur and chelated ferric ion is reduced to chelated ferrous ion, the total concentration of ferrous and ferric iron in the aqueous solution being more than about 0.1 mole per liter of solution and the aqueous solution containing a salt selected from the group consisting of a sulfate, chloride, or nitrate salt of ammonia or an aliphatic, alicyclic, or heterocyclic primary or secondary amine present in a sufficient proportion to maintain the thus formed chelated ferrous ion in solution.

Claim 32

A process as recited in claim 26 wherein the aqueous solution containing chelated ferrous ion is contacted with a gas containing elemental oxygen, whereby chelated ferrous ion is oxidized to chelated ferric ion.

Claim 33

A process as recited in claim 27 wherein the aqueous solution is contacted with a gas stream containing both hydrogen sulfide and oxygen.

Claim 34

A process as recited in claim 1 wherein the salt is an ammonium salt of a strong mineral acid present in the aqueous solution in a concentration of at least one mole per mole of the thus formed chelated ferrous ion; an aliphatic, alicyclic or heterocyclic primary or secondary organic monoamine salt of a strong mineral acid present in the aqueous solution in a concentration of at least about 0.6 mole per mole of the thus formed chelated ferrous ion, or an aliphatic, alicyclic or hetercyclic organic polyamine salt of a strong mineral acid present in the aqueous solution at a concnetration of at least about 0.3 mole per mole of the thus formed chelated ferrous ion.

Claim 35

A process as recited in claim 20 wherein the salt is an ammonium salt of a strong mineral acid present in the aqueous solution in a concentration of at least one mole per mole of the thus formed chelated ferrous ion; an aliphatic, alicyclic or heterocyclic primary or secondary organic monoamine salt of a strong mineral acid present in the aqueous solution in a concentration of at least about 0.6 mole per mole of the thus formed chelated ferrous ion, or an aliphatic, alicyclic or heterocyclic organic polyamine salt of a strong mineral acid present in the aqueous solution at a concentation of at least about 0.3 mole per mole of the thus formed chelated ferrous ion.

Claim 36

A process for the removal of hydrogen sulfide from gaseous streams which comprises: contacting a gaseous stream containing hydrogen sulfide with an aqueous solution of ferric ion chelated with nitrilotriacetic acid at a pH of about 3.5 to 5, whereby hydrogen sulfide is oxidized to elemental sulfur and chelated ferric ion is reduced to chelated ferrous ion, the total concentration of ferrous ion and ferric ion in the aqueous solution being in the range of about 0.5 to 1.0 mole per liter, the solution containing a salt selected from the group consisting of a sulfate, chloride or nitrate salt of ammonia present in a concentration of at least about one mole per mole of the thus formed chelated ferrous ion; a sulfate, chloride or nitrate salt of an aliphatic, alicyclic or heterocyclic primary or secondary organic monoamine present in a concentration of at least about 0.6 mole per mole of the thus formed ferrous ion and a sulfate, chloride or nitrate salt of an aliphatic, alicyclic or heterocyclic primary or secondary organic polyamine present in a concentration of at least about 0.3 mole per mole of the thus formed chelated ferrous ion.

Claim 37

A process for the removal of hydrogen sulfide from gaseous streams which comprises: contacting a gaseous stream containing hydrogen sulfide with an aqueous solution of ferric ion chelated with nitrilotriacetic acid at a pH of about 3.5 to 5, whereby hydrogen sulfide is oxidized to elemental sulfur and chelated ferric ion is reduced to chelated ferrous ion, the total concentration of ferrous ion and ferric ion in the aqueous solution being in the range of about 0.5 to 1.0 mole per liter, the solution containing a salt selected from the group consisting of a sulfate, chloride or nitrate salt of ammonia present in a concentration of at least about one mole per mole of the thus formed chelated ferrous ion; a sulfate, chloride or nitrate salt of an aliphatic, alicyclic or heterocyclic primary or secondary organic monoamine present in a concentration of at least about 0.6 mole per mole of the thus formed ferrous ion and a sulfate, chloride or nitrate salt of an aliphatic, alicyclic or heterocyclic primary or secondary organic polyamine present in a concentration of at least about 0.3 mole per mole of the thus formed chelated ferrous ion.

Claim 38

A process as recited in claim 31 wherein the aqueous solution containing chelated ferrous ion is cntacted with a gas containing elemental oxygen, whereby chelated ferrous ion is oxidized to chelated ferric ion.

Claim 39

A process as recited in claim 32 wherein the aqueous solution is contacted with a gas stream containing both hydrogen sulfide and oxygen.

Claim 40

A process for the removal of hydrogen sulfide from gaseous streams which comprises: contacting a gaseous stream containing hydrogen sulfide with an aquoeus solution of ferric ion chelated with nitrilotriacetic acid at pH of about 3.5 to 5, wherein hydrogen sulfide is oxidixed to elemental sulfur and chelated ferric ion is reduced to chelated ferrous ion, the total concentration of ferrous ion and ferric ion in the solution being in the range of about 0.5 to 1.0 mole per liter, the solution containing a sulfate salt of triethylenetetramine present in a concentration of at least about 0.3 mole per mole of the thus formed ferrous ion.

Claim 41

A process for the removal of hydrogen sulfide from gaseous streams which comprises: contacting a gaseous stream containing hydrogen sulfide with an aquoeus solution of ferric ion chelated with nitrilotriacetic acid at pH of about 3.5 to 5, wherein hydrogen sulfide is oxidixed to elemental sulfur and chelated ferric ion is reduced to chelated ferrous ion, the total concentration of ferrous ion and ferric ion in the solution being in the range of about 0.5 to 1.0 mole per liter, the solution containing a sulfate salt of triethylenetetramine present in a concentration of at least about 0.3 mole per mole of the thus formed ferrous ion.