| Global warming is a serious challenge for human society, which is mainly caused by exclusive emissions of carbon dioxide. Some research results reveal that the concentration of CO2 in the atmosphere has increased to 400 ppm. The exclusive emissions of carbon dioxide arise from the combustion of carbon-containing fossil fuels that will remain the world’s main source of energy for many years, thus reducing CO2 emissions is an important and meaningful research. CO2 capture with chemical absorption has long history, mature technology and stable operation. However, the regeneration energy for absorber is too high, so the key point to reduce CO2 capture cost is to reduce desorption energy. Only CO2-rich phase needs to be heated for regeneration and CO2-lean phase does not need to be heated through phase-changing CO2 absorption providing increased energy efficiency. After desorption, absorber can be directly mixed with CO2-lean phase and returned to the absorption tower for the next cycle. In this work, some organic solvents with excellent performance were selected to respectively dissolve alkyl polyamines for achieving liquid-solid phase-change after CO2 absorption. Phase-changing mechanism and new method for CO2 desorption have been proposed in the course of the experiment. The specific research contents are as follows:Firstly, a variety of organic solvents were chosen to dissolve chain polyamine of EDA, which was used as absorption liquid. Liquid-solid phase-changing phenomenon appeared after CO2 absorption using these absorption liquid. Fourier Transform Infrared (FTIR) spectrum characterization indicated that different solvents had no influence on the products’nature. FTIR, Nuclear magnetic resonance (NMR) spectrum, organic element analyzer and X-Ray Diffraction (XRD) analysis demonstrated that the solid products were the corresponding carbamates. However, carbamates with different crystal forms were gotten from different organic solvents. Thermogravimetric analysis and differential scanning calorimetry (TG-DSC) tests indicated that decomposition temperature of carbamate and volatilization temperature of EDA were not at the same range of temperature.Secondly, to solve the problem that the low boiling point of EDA, diethylenetriamine (DETA) was chosen as absorbent Some solvents with the advantages of relatively low viscosity and Henry’s constant of CO2, as well as the high boiling point were selected to respectively dissolve DETA. The white solid appeared and liquid-solid phase-change was also realized after absorption. XRD and FTIR spectra characterization indicated that different solvents had no influence on the products’nature. Analysis implied that carbamate was formed for equimolar CO2 absorption, the result was further demonstrated by single crystal X-ray diffraction analysis. CO2 absorption capacity was measured with a vapor-liquid equilibrium apparatus and the result showed the CO2 absorption loading of 30 wt%DETA solution approached 1 mole CO2/mole amine even at low partial pressure, which was higher than MEA solution. TG-DSC analysis indicated that decomposition temperature of the carbamate was lower than volatilization temperature of DETA. The desorption process of the carbamate was implemented via microwave heating, and the absorption and desorption capacity of absorptin liquid were relatively stable, the result demonstrated that it was a kind of excellent way for amine regeneration.Thirdly, the absorption liquids of triethylenetetramine (TETA) and tetraethylenepentamine (TEPA) respectively dissolved into organic solvents absorbed CO2. Liquid-solid phase-changing phenomenon appeared after CO2 absorption using these absorption liquid. FTIR spectra characterization indicated that different solvents had no influence on the products’nature for the same amine. FTIR and NMR spectra analysis demonstrated that the solid products were the corresponding carbamates. TG-DSC experiments indicated that these absorbers could be regenerated for the next cycle.Finally, absorption liquid of piperazine (PZ)/ethanol absorbed CO2 to achieve liquid-solid phase-change and the utilization of its solid product. Ethanol was acted as solvent to dissolve PZ. This absorption liquid could absorb CO2 to get white solid and achieve liquid-solid phase-change. FTIR and NMR spectra analysis demonstrated that the solid product was PZ-carbamate. TG-DSC test showed decomposition of PZ-carbamate and volatilization of PZ proceeded simultaneously. In addition, reaction of PZ-carbamat and propylene oxide to propylene carbonate was investgated at different reaction conditions.
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