Process for the removal of hydrogen sulfide from gaseous streams by catalytic oxidation of hydrogen sulfide to sulfur while inhibiting the formation of sulfur oxides

A cyclic process for the removal of hydrogen sulfide and alkyl mercaptans contained in gaseous streams, and the substantially quantitative catalytic conversion thereof to elemental sulfur and dialkyl disulfides, respectively, while inhibiting the formation of acidic sulfur oxides, which comprises contacting the gaseous stream with an aqueous solution consisting essentially of a water-soluble polyvalent metal chelate catalyst retaining the metal in soluble form in the aqueous solution and having a pH within the range from about 3 to about 11, the chelate catalyst comprising a chelating amino acid selected from the group consisting of:

• (A).sub.3.sub.-n -- N -- (X).sub.n, I
• wherein
• n is a number from 1 to 3;
• X is selected from the class consisting of acetic and propionic acid groups;
• A is 2-hydroxy ethyl, 2-hydroxy propyl, or an alkyl group having from one to about four carbon atoms. ##STR3## wherein from two to four of the groups X are selected from the class consisting of acetic and propionic acid groups;
• from zero to two of the groups X are selected from the class consisting of 2-hydroxy ethyl, 2-hydroxy propyl, and ##STR4## R is ethylene, propylene or isopropylene or alternatively cyclohexane or benzene where the two hydrogen atoms replaced by nitrogen are in the 1,2-position;
• and an alkali metal, alkaline earth metal, ammonium or amine salt of an acid other than the chelating amino acid having a pK within the range from about 1.2 to about 6 in an amount within the range from 1 to 14 equivalents calculated as Fe equivalents;
• contacting aqueous polyvalent metal chelate catalyst solution with free oxygen gas to regenerate the catalyst for contact with another portion of the gaseous stream;
• and separating the sulfur and any dialkyl disulfides from the aqueous metal chelate solution.