Piperazine induced enhancement of absorption performance and degradation resistance in biphasic CO2 capture system

Abstract

The biphasic solvent has great potential for low-energy CO₂ capture. Currently, most studies focus on promoting CO₂ absorption performance while ignoring the degradation issue of amines. Here, a novel biphasic solvent was developed, wherein, the ring-structure organic amine with multiple amine groups (piperazine, PZ) was used to simultaneously enhance CO₂ absorption performance and degradation resistance of MEA. Results indicated that CO₂ absorption capacity increased by 23 % with PZ addition compared to M₃₇B₃₃H₃₀ (M: MEA, B: n-butanol, H: water), while the viscosity and phase separation time were not remarkably affected. Meanwhile, the developed biphasic solvent showed a better degradation resistance than both single MEA and PZ. Specifically, the formation of acid anions was reduced by 66.4 % and 17.4 % compared to single MEA and PZ. It was found that the degradation products of PZ mainly include EPZ, AEP, MPZ. The degradation products of MEA mainly include HEGly, HEPO, HEI, HEA, AEHEIA, Adipamide, BHEOX, and HEEDA, which were significantly inhibited by PZ. The KI can furtherly enhance degradation resistance by removing the dissolved oxygen in the solvent, and the optimal addition amount is 3 %. However, excess KI causes the reduction of Fe³⁺ to Fe²⁺, which triggers Fenton reaction to generate hydroxyl radicals (•OH). Finally, a detailed degradation mechanism was proposed by comprehensively analyzing the results of current work and previous studies.