Acid gas absorbent in biogas and biogas purification system using the same

An absorbent for absorption of an acid gas in a biogas, comprising:

• a tertiary amine represented by the following [Chemical Formula] 1;
• a primary or secondary amine;
• and
• a solvent;
• wherein the primary or secondary amine comprises any one amine selected from the group consisting of AMP(2-amino-2-methyl-1-propanol), APA(bis(3-aminopropyl)amine), DAB(1,4-diaminobutane), DBA(dibutylamine), AB(2-amino-1-butanol), AP(5-amino-1-pentanol), PED(N-propylethylenediamine), DEP(1-dimethylamino-2-propanol), PA(1-propanamine), DPA(N-propyl-propanamine), BA(1-butanamine), IBA(2-methyl-1-propanamine), SBA(2-butanamine), 1,2-dimethylpropylamine, 3-methyl-2-butanamine, hexylamine, allylamine, diallylamine, 3-methoxy propylamine, 3-ethoxyl propylamine, 3-propoxypropylamine, 3-isopropoxy propylamine, 3-butoxyl propylamine, 3-decyloxypropylamine, 3-lauryloxy propylamine, dimethylamino ethylamine, ethylaminoethylamine, 1,2-diaminopropane, 1,3-diamino propane, N,N-diethyl-1,3-propanediamine, dibutylamino propylamine, bis-(3-aminopropyl) ether, 1,2-diaminobutane, 1,4-diaminobutane, and combinations thereof;
• wherein the primary or secondary amine does not include piperazine;
• wherein the content of the primary or secondary amine is 8 to 15 parts by weight with respect to 100 parts by weight of the tertiary amine;
• wherein [Chemical Formula 1] is:
• wherein R1 is linear C1-C3 alkyl or linear C2-C5 alkenyl;
• and
• wherein R2 and R3 are independently linear C1-C5 alkyl having a terminal thereof substituted with a hydroxyl group, or linear C2-C5 alkenyl having a terminal thereof substituted with a hydroxyl group.