Study On Absorption Of CO₂ From Flue Gas By Hydrophobic Functionalized Deep Eutectic Solvent

Carbon dioxide(CO2)is one of the main greenhouse gases,which is a direct threat to the environment and human health.In another hand,CO2 is an important chemical raw material in industry,so it is very important to develop kinds of recyclable absorbents to capture CO2 from flue gas with high capacity and low volatility.DES is a kind of deep eutectic mixture formed by hydrogen bonding of two or more compounds.Its freezing point is significantly lower than the melting point of pure substances.DES shows great potential in the field of CO2 capture.Hydrophobic absorbent can avoid dissolving much water while treating CO2 in flue gas,which results in a large increase of desorption energy consumption.Depending on the reported literature,hydrophobic DES can not effectively absorb low concentration CO2.In this thesis,we designed and synthesized polyamine hydrochloride,polyamine and super alkali hydrophobic functionalized DES,and investigated the absorption effect of different concentrations of CO2 under different conditions,and studied the absorption mechanism.The main conclusions are as follows:1.The hydrophobic functional DES of polyamine hydrochloride with high thermal stability was designed and synthesized by polyamine hydrochloride as hydrogen bond acceptor(HBAs)and thymol as hydrogen bond donor(HBD).This kind of DESs have multiple absorption sites,and also have higher absorption capacity when the content of CO2 is low.The saturated absorption capacity of thymol-[TEPA]Cl DES(nthymol/n[TEPA]Cl=3:1),can reach 0.6485mol CO2/mol DES at 50℃ and CO2 partial pressure of 10.1 kPa,and the saturation capacity increases with the decrease of temperature and the increase of CO2 partial pressure.However,with the increase of thymol ratio,CO2 absorption increased first and then decreased.The absorption mechanism of this kind of DES for CO2 is obtained by combining the absorption data,thermodynamic calculation results and infrared results:1 mol CO2 can react reversibly with 2 mol-NH-to form carboxylate.2.The hydrophobic functionalized DES of polyamines was prepared by polyamines and thymol.The polyamine DES has one more amino group than the similar polyamine hydrochloride DES,so it has higher saturated molar absorption.The saturation increased with the decrease of temperature and the increase of CO2 partial pressure,and increased first and then decreased with the increase of thymol proportion.Combined with the experimental data and infrared results,the absorption mechanism of CO2 by this kind of DES was proposed.The absorption mechanism of this kind of DES for CO2:1 mol CO2 can react reversibly with 2 mol-NH-to form carboxylate.3.The hydrophobic functionalized DES of super base was synthesized by the organic compounds containing alcohol hydroxyl as hydrogen bond donor and super base as hydrogen bond acceptor.At 50℃ and 101 kPa of CO2 partial pressure,the mass saturated absorption of Dec-DBN DES(nDec/nDBN=1:1)can reach 10.1%,and the absorption rate is fast.The absorption increases with the decrease of temperature and the increase of CO2 partial pressure.The physical property data show that the viscosity is very low before and after absorption.