Absorbent composition for the selective absorption of hydrogen sulfide
An absorbent composition that is useful in the selective removal of hydrogen sulfide relative to carbon dioxide from gaseous mixtures that comprise both hydrogen sulfide and carbon dioxide and the use thereof. The absorbent composition includes an amine mixture of an amination reaction product of tert-butylamine with a polydispersed polyethylene glycol (PEG) mixture having an average molecular weight within a certain specified range of molecular weights. The amination reaction product may also comprise a first sterically hindered amine and a second sterically hindered amine. The absorbent composition, preferably, includes an organic co-solvent, such as a sulfone compound. A method is also provided for improving the operation of certain gas absorption processes by utilizing the absorbent composition.
1. An absorbent composition, comprising: (a) from 75 wt. % to 98 wt. %, based on the total weight of said absorbent composition, of an aqueous solvent; and (b) from 2 wt. % to 25 wt. %, based on the total weight of said absorbent composition, of an organic co-solvent, wherein said aqueous solvent comprises from 20 wt. % to 70 wt. %, based on the total weight of said aqueous solvent, of an amination reaction product of a polydispersed polyethylene glycol (PEG) mixture having an average molecular weight that is in the range of from 180 to 1000 and t-butylamine, and from 30 wt. % to 80 wt. % water, based on the total weight of said aqueous solvent, and wherein said organic co-solvent is selected from the group consisting of sulfones, sulfone derivatives, and sulfoxides.
2. An absorbent composition as recited in claim 1 , wherein said PEG mixture comprises polyethylene glycols of the formula HOCH 2 (CH 2 OCH 2 )CH 2 OH, wherein n is an integer selected from values in the range of from 1 to 24.
3. An absorbent composition as recited in claim 1 , wherein said aqueous solvent is present in said absorbent composition in an amount in the range of from 85 wt. % to 97.5 wt. %, wherein said average molecular weight of said PEG mixture is in the range of from 180 to 400, and wherein said organic co-solvent present in said absorbent composition is in an amount in the range of from 2.5 wt. % to 15 wt. %.
4. An absorbent composition as recited in claim 1 , wherein said amination reaction product further comprises at least a first sterically hindered amine and a second sterically hindered amine.
5. An absorbent composition as recited in claim 4 , wherein said first sterically hindered amine is selected from the group of amine compounds of the formula:
(CH 3 ) 3 CNH(CH 2 CH 2 O) x CH 2 CH 2 NHC(CH 3 ) 3 , wherein x is an integer in the range of from 2 to 16; and
wherein said second sterically hindered amine is selected from the group of amine compounds having the following formula:
(CH 3 ) 3 CNH(CH 2 CH 2 O) x CH 2 CH 2 OH, wherein x is an integer in the range of from 2 to 16.
6. An absorbent composition as recited in claim 5 , wherein said amination reaction product has a weight ratio of said first sterically hindered amine to said second sterically hindered amine that is in the range upwardly to 10:1.
7. An absorbent composition as recited in claim 6 , wherein said amination reaction product has a weight ratio of said first sterically hindered amine to said second sterically hindered amine that is in the range of from 2.5:1 to 8:1.