Preparation And Properties Of Amino Acid Type Temperature Sensitive Phase Separation Absorbent

The traditional liquid absorbent regeneration process often requires a large regeneration energy consumption due to solvent volatilization,so it is imperative to develop a liquid absorbent with low energy consumption.Phase separation absorbent is a new energy-saving liquid absorbent.After absorbing CO₂,the system will be separated into solid-liquid or solid-solid incompatible phases,which can greatly reduce the energy consumption for regeneration by desorbing only one phase rich in carbon dioxide.This paper first describes the research progress of liquid CO₂ capture materials,and synthesizes a series of temperature-sensitive phase separation absorbents based on quaternary ammonium salts and N-isopropyl acrylamide,and their CO₂ absorption capacity,phase separation efficiency and regeneration research was conducted using the ability to use.First,a glycine-type temperature-sensitive phase separation absorbent with controlled molecular weight was prepared.The effects of concentration and temperature on the CO₂ absorption capacity and phase separation efficiency of the absorbent were studied.Second,in order to compare the effect of molecular weight on the absorbent,the glycine-type temperature-sensitive phase separation absorbents with different molecular weights were prepared.The effects of molecular weight,concentration and temperature on the CO₂ absorption capacity and phase separation efficiency of the absorbent were studied,and the ability to regenerate was tested.Third,in order to compare the effects of amino acid types on absorbents.The temperature-sensitive phase separation absorbents of different amino acid types were prepared.The effects of amino acid types on the CO₂ absorption capacity and phase separation efficiency of the absorbent were studied,and the ability to regenerate the absorbent was tested.First,glycine type temperature sensitive phase separation absorbent PVB（5K）-Gly-b-PNIP（2K）was prepared by atom transfer radical polymerization（ATRP）,ion exchange reaction,and neutralization reaction using benzylethyltrimethylammonium chloride（VBTAC）and N-isopropylacrylamide（NIPAM）as monomers.The structure and thermal stability of the product were investigated by nuclear magnetic resonance spectroscopy（¹H-NMR）,Fourier transform infrared spectroscopy（FT-IR）,GPC,X-ray photoelectron spectroscopy（XPS）and thermogravimetry（TG）.The phase transition temperature of the product was tested by changes in transmittance at different temperatures.The effects of concentration and temperature on the CO₂ absorption capacity and phase separation efficiency of the absorbent were investigated.The concentration has a great influence on the CO₂absorption capacity of the absorbent.Under the experimental conditions,the 0.4M absorbent PVB（5K）-Gly-b-PNIP（2K）has the largest CO₂ absorption capacity,reaching 1.11 mol CO₂/mol Absorbent.The temperature also has a great influence on the phase separation efficiency of the absorbent.At room temperature,only a small concentration of the absorbent has a small amount of phase separation;at a temperature higher than the phase transition temperature,the phase separation efficiency is significantly improved by the centrifugal phase separation.Among them,the 0.7M absorbent PVB（5K）-Gly-b-PNIP（2K）phase separation efficiency is the highest,reaching 16.7%.Secondly,different glycine type absorbents PVB-Gly-b-PNIP with different molecular weights were prepared by ATRP,ion exchange reaction and neutralization reaction.The structure and thermal stability of the product were investigated by ¹H-NMR,X-ray photoelectron spectroscopy（XPS）and thermogravimetry（TG）.The phase transition temperature of the product was tested by changes in transmittance at different temperatures.The effects of molecular weight,concentration and temperature on the CO₂ absorption capacity and phase separation efficiency of the absorbent were investigated,and the ability to regenerate was tested.The concentration has a great influence on the CO₂ absorption capacity of the absorbent.Under the experimental conditions,for the absorbent PVB（2.5K）-Gly-b-PNIP（1K）,the concentration of 0.4M is the largest,which is 1.12 mol CO₂/mol Absorbent;for the absorbent PVB（1.5K）-Gly-b-PNIP（0.5K）,the maximum absorption is0.6M,which is mol 0.83 CO₂/mol Absorbent.The temperature also has a great influence on the phase separation efficiency of the absorbent.At room temperature,only a small concentration of the absorbent has a small amount of phase separation;at a temperature higher than the phase transition temperature,the phase separation efficiency is significantly improved by the centrifugal phase separation.Among them,for the absorbent PVB（2.5K）-Gly-b-PNIP（1K）,the phase separation efficiency with the highest concentration of0.8M is reached,for the absorbent PVB（1.5K）-Gly-b-PNIP（0.5K）,the phase separation efficiency of the highest concentration of 1.3M was reached.The difference in molecular weight has a certain influence on CO₂ absorption capacity and phase separation efficiency.Among them,under the condition of 0.6M,the absorbent PVB（5K）-Gly-b-PNIP（2K）has the highest CO₂ absorption,reaching 1.00 mol CO₂/mol Absorbent;absorbent PVB（2.5K）-Gly-b-PNIP（1K）has the highest phase separation efficiency of 16.7%.In the CO₂absorption/desorption experiment of the absorbent PVB（2.5K）-Gly-b-PNIP（1K）,only the solid phase was desorbed,and the regeneration rate reached 48%.Finally,different amino acid types were prepared by ATRP,ion exchange reaction and neutralization reaction with glycine（Gly）,aspartic acid（Asp）,tryptophan（Trp）and L-histidine（His）as anions.The absorbent PVB（2.5K）-AA-b-PNIP（1K）.The effect of amino acid type on the CO₂ absorption capacity and phase separation efficiency of the absorbent was investigated.Among them,0.8M absorbent PVB（2.5K）-Gly-b-PNIP（1K）has the largest CO₂absorption,0.86 mol CO₂/mol Absorbent;1.2M absorbent PVB（2.5K）-Trp-b-PNIP（1K）has the highest phase separation efficiency.In the CO₂ absorption/desorption experiment of the absorbent PVB（2.5K）-Trp-b-PNIP（1K）,only the solid phase was desorbed,and the regeneration rate reached 76%.The series of amino acid temperature-sensitive phase separation liquid absorbents prepared in this thesis have the advantages of easy synthesis of raw materials,strong carbon dioxide absorption capacity and low energy consumption,and have good industrial carbon capture prospects.