The Study On The Mixed Ionic Liquid Solutions For Carbon Dioxide Absorption

In recent years, the emission of CO2in China has kept increasing with the each passing year. Environmental problems caused by the major greenhouse gas have received more and more attention. Nowadays, technologies of capturing carbon dioxide using aqueous organic amines and inorganic base solutions have extensively carried out in the industry. However, there exists many disadvantages using these chemicals, including high energy consumption of desorption, equipment corrosion, and environmental secondary pollution caused by the volatile organics. Ionic liquids have been paid much attention. They have many outstanding characteristics such as low vapor pressure, high thermal stability, designable structure and so on.At present, aqueous alkanolamines used as chemical absorbents for removal carbon dioxide have been widely researched. In order to reduce the cost, the N1111AC and [emim][Ac] are prepared. Meanwhile to reduce the viscosity, the ionic liquids considered as an additive are added to the propylene carbonate (PC) and sulfolane. Several important results have been obtained and summarized as follows:(1) N1111Ac and [emim][Ac] are prepared. With the content of N1111Ac decreased, the CO2absorption capacity is obviously reduced. It is clearly that the absorption reaction is dominated by chemical absorption when the pressure is lower than about25Kpa and the physical absorption plays a leading role with the pressure exceeding25Kpa. (2) The viscosities and densities of the mixed solutions ([emim][Ac]+PC) were measured over the whole concentration range with the temperature ranging from298.15K to333.15K. The results show that with the rising of temperature and the increase of the content of ionic liquid, the densities of all binary systems decrease linearly with the increasing temperature. It’s obviously that the viscosities decrease with the raising temperature. In addition, the solubility of carbon dioxide in binary system containing a fixed mole ratio of0.5002、0.4028、0.2957、0.1943at283.15K,298.15K,313.15K,333.15K were measured under pressures up to9bar. The results show that the increase of the content of ionic liquids and lower temperature are conducive to CO2capture.(3) As temperatures rise gradually, the densities of the mixture ([emim][Ac]+sulfolane) are reduced and all the densities decreased with the same slope. It’s obviously that the viscosities decrease with the raising temperature. In this work, the solubility of carbon dioxide in binary system containing a fixed mole ratio of0.1485、0.2344、0.3229、0.4107at283.15K,298.15K,313.15K,333.15K were measured. The results show that the attraction for CO2weakens when the content of CH3COO-decreases and the temperature increases.At the same time, higher temperatures result in lower viscosity and this phenomenon is helpful to shorten the time. Therefore, the two factors should be considered to select the right temperature. the thermodynamic parameters such as Henry’s constant HIL, the equilibrium constant K1, K2were obtained. The Henry’s constant HIL increases noticeably as the temperature elevates. All the K1in this work are0which are consistent with our previous study. K2decreases apparently with the increasing temperature, which indicates that the higher temperature is bad for absorption capacity. This work about the synthesis of ionic liquids, density measurements, viscosity measurements, and the blended absorbents for CO2capture give the guidance for the applications of ionic liquids.