Process for removal of carbonyl sulfide in liquified hydrocarbon gases with absorption of acid gases

A process for purifying a liquified hydrocarbon gas stream containing as impurities carbonyl sulfide and at least hydrogen sulfide which comprises:

• (a) contacting the liquified hydrocarbon gas stream with a first liquid aqueous absorption solution containing an absorbent for hydrogen sulfide which absorbent does not combine irreversibly with carbonyl sulfide, hydrogen sulfide, and carbon dioxide to absorb, at a first temperature, hydrogen sulfide from the liquified hydrocarbon gas to leave a residual stream of liquified hydrocarbon gas containing carbonyl sulfide;
• (b) intimately mixing the residual stream of liquified hydrocarbon gas containing carbonyl sulfide with a second liquid aqueous solution containing an absorbent for at least hydrogen sulfide which absorbent does not combine irreversibly with carbonyl sulfide, hydrogen sulfide, and carbon dioxide in a hydrolysis reaction zone at a temperature higher than the first temperature and sufficient to hydrolyze the contained carbonyl sulfide to hydrogen sulfide and carbon dioxide and hydrolyzing the carbonyl sulfide to form a two phase mixture of liquified hydrocarbon gas containing at least a portion of the hydrogen sulfide and carbon dioxide formed by hydrolysis of carbonyl sulfide and a second liquid aqueous absorption solution containing hydrogen sulfide;
• and
• (c) separating the liquidfied hydrocarbon gas containing the hydrogen sulfide and carbon dioxide from the second liquid aqueous absorption solution containing the hydrogen sulfide and contacting, at a temperature lower than the hydrolysis reaction zone, the liquified hydrocarbon gas containing hydrogen sulfide and carbon dioxide with a hydrogen sulfide lean liquid aqueous absorbent for at least hydrogen sulfide which does not combine irreversibly with carbonyl sulfide, hydrogen sulfide, and carbon dioxide, to absorb at least formed hydrogen sulfide from the liquified hydrocarbon gas.

A process for purifying a liquified hydrocarbon gas stream containing as impurities carbonyl sulfide and at least hydrogen sulfide which comprises:

• (a) contacting the liquified hydrocarbon gas stream with a first liquid aqueous solution of diethanolamine to absorb, at a first temperature, hydrogen sulfide from the liquified hydrocarbon gas and leave a residual stream of liquified hydrocarbon gas containing carbonyl sulfide;
• (b) intimately mixing the residual stream of liquified hydrocarbon gas containing carbonyl sulfide with a second aqueous solution of diethanolamine in a hydrolysis zone maintained at a temperature higher than the first temperature and sufficient to hydrolyze the carbonyl sulfide to hydrogen sulfide and carbon dioxide and hydrolyzing the carbonyl sulfide to form a two phase mixture of liquified hydrocarbon gas containing at least a portion of the hydrogen sulfide and carbon dioxide formed by hydrolysis of carbonyl sulfide and a second aqueous diethanolamine solution containing hydrogen sulfide and carbon dioxide;
• (c) separating the liquified hydrocarbon gas containing formed hydrogen sulfide and carbon dioxide from the aqueous solution of diethanolamine and contacting, at a temperature lower than the temperature of the hydrolysis reaction zone, the liquified hydrocarbon gas containing hydrogen sulfide and carbon dioxide with the third hydrogen sulfide lean, aqueous solution of diethanolamine to absorb formed hydrogen sulfide and carbon dioxide from liquified hydrocarbon gas.