Method of removing H.sub.2 S from a gas stream utilizing boron-vanadium and iron complexes

In a method of removing H.sub.2 S from a sour gas by oxidation of the H.sub.2 S to free sulfur, the improved steps of:

• bringing the sour gas into H.sub.2 S absorbing relationship with a liquid alkaline absorption medium whereby H.sub.2 S is absorbed and at least part thereof forms [HS.sup.- ] ions,
• said liquid absorption medium being essentially devoid of anthraquinone disulfonic acid compounds and containing a vanadium-boron complex capable of oxidizing the [HS.sup.- ] ions to produce elemental sulfur as the vanadium undergoes reduction and the boron constituent functions to inhibit formation of insoluble vanadium sulfide compounds and consequent thiosulfate formation upon re-oxidation of the vanadium,
• the ratio of boron to vanadium in said absorption medium being at least about 1:1;
• regenerating the absorption medium by adding an oxygen source thereto to oxidize the reduced vanadium;
• and
• providing a sufficient quantity of an iron complex catalytic agent during regeneration of the absorption medium which is capable of catalyzing re-oxidation of the reduced vanadium to enhance oxidation of the latter without deleteriously affecting recoverability of free sulfur from the absorption medium.