Selective removal of sulfur compounds from acid gas mixtures containing significant quantities of carbonyl sulfide

Claim 1

A continuous process for selective removal of sulfur compounds from a feed gas mixture containing CO 2 , H 2 S and at least 50 parts per million of COS which comprises; a. contacting said feed gas mixture in a first stage at a temperature of from 50°C to 90°C with an aqueous polyalkanolamine solution containing at least 20% by weight of a tetramethylene sulfone, said aqueous polyalkanolamine solution being saturated with CO 2 and H 2 S at the partial pressures of said components in the acid gas feed mixture, thereby absorbing and hydrolyzing a substantial portion of the COS present in said acid gas feed mixture to form and maintain a steady state concentration of acid gas consisting substantially of CO 2 and H 2 S in the gas phase of the first stage; b. withdrawing said gas phase from the first stage and contacting it in a second stage with a regenerable H 2 S-selective, aqueous alkanolamine absorbent solution to afford a substantially H 2 S-free, CO 2 -containing treated gas mixture and an absorbent solution loaded with absorbed H 2 S; c. regenerating the H 2 S-loaded absorbent solution thereby liberating H 2 S; and, d. returning the regenerated absorbent into contact with the gas phase in the second stage of the process.