The Development Of High-capacity,Low-viscosity And Water-lean CO₂ Absorbents

The ever-growing CO2 emission from industrial point source has been gaining popular attention,due to the continuous increase of fossil fuel demand by human society.Current industrial CO2 capture processes largely rely on the mature amine scrubbing technology,which needs vast amount of water?50⁷0 wt%?as diluter to reduce its operating viscosity.The utilization of water as solvent renders some intrinsic disadvantages that are hard to overcome,such as large energy input for CO2 desorption as a result of the high specific heat capacity of water and equipment corrosion due to the strong basicity of aqueous amine solution.In addition,the low absorption capacity of aqueous alkanolamine should also be attributed to the large amounts of water within the absorber.Hence,much effort has been devoted to the development of highly efficient and nonaqueous CO2 absorbents from both academic and industrial fields.The present thesis aims to develop versatile molecular design strategy for the constructuon of novel water-lean CO2 absorbents,which have high capacity,low energy consumption as well as industrial viable operating viscosity.The main contents are as follows:?1?A series of ether-functionalized MEAs?monoethanolamines?has been constructed by simple structural modification of this cheap industrial absorbent for CO2 capture under water-lean conditions.The resulting ether-functionalized MEAs have been employed as solvent-free absorbents with enhanced gravimetric capacities?11-19 wt%at 25 ^oC and 12-20wt%at 40 ^oC?and relatively low operating viscosities?as low as 311 cP at 25 ^oC and 105 cP at 40 ^oC?at the CO2-saturated state.The captured CO2 could be easily stripped out by heating at relatively low temperature?75 ^oC?,and the absorbents could be cycled smoothly without loss of capacity.Such novel absorbents also exhibit excess absorption capacity under high operating pressures?20 and 30 bar?,owing to the CO2-philic nature of the ether group for additional physisorption.Furthermore,a systematic structure–property relationship among these functionalized MEAs has been established through investigation of their kinetic and thermodynamic properties by means of DFT calculations,¹³C NMR spectroscopy,DSC and in situ FTIR analysis.?2?Various ether-functionalized ethylenediamines has been devised as single-component absorbents for post-combustion CO2 capture.These nonaqueous absorbents have outstanding viscosities?50-200 cP at 25 ^oC and 20-110 cP at 40 ^oC?at their maximal CO2 capacities?up to22 wt%at 25 ^oC and 21 wt%at 40 ^oC?,and are readily regenerated at low temperatures?50-80 ^oC?under ambient pressure.Additional capture of CO2 through physisorption could also be achieved by operating at high pressures?up to 136 mol%at 20 bar and 160 mol%at30 bar?.The absorption mechanisum is systematically investigated by means of ¹³C NMR spectroscopy,in situ FTIR analysis,vapor-liquid equilibrium,DSC and DFT calculations,which could provide sufficient spectroscopic details to reveal both kinetic and thermodynamic properties within the CO2 capture and release cycle as well as establish a detailed structure-property relationship for these functionalized ethylenediamines.