Treatment of Carbonyl sulfur in Propylene

[PetroDDP]

We are facing difficulty to reduce carbonyl sulfur (COS) in propylene product ex Propylene Recovery Unit from LPG ex FCC and Coker Unit.We are using Merox process for LPG Sweetning.
The Total sulfur in Merox product outlet is in the range of 7 to 9 ppm.

Request you to suggest remedial measures.

Thanks.

 

[25362]

From IP's Modern Petroleum Technology (Wiley) it appears that COS removal is conventionally done by caustic washing in two steps:

[•] a slow mass transfer from the LPG to the water phase,favoured by a low caustic stremgth of the order of 3% w/w, followed by
[•] a hydrolysis to CO[sub]2[/sub] and H[sub]2[/sub]S, favoured by a high caustic strength.

I hope the above is of some help.