| Biomass fuel gas, also known as industrial marsh gas, is generated in the anaerobic microbial degradation process of organic matter. Methane content is high in mixed gas and could reach97%after effective decarburization purification. Therefore, the biomass fuel gas is a good candidate for natural gas energy, and developing biomass fuel gas must accelerate the new transformation of national energy strategy characterized by "independent" and "green transformation". At present, it is well known that global warming is directly related to levels of carbon dioxide, and carbon dioxide emitted by fossil fuels accounts for more than80%in the total global carbon dioxide emissions. Therefore, decarbonization of biomass gas purification is the best choice to advocate low-carbon consumption and practise sustainable development strategy.Compared with traditional membrane separation method, immobilized ionic liquid membrane possesses many advantages such as large flux, perfect selectivity and high stability, and especially has wide application prospects in the process of biomass gas separation. It has become hot topic of the researchers around the world in recent years. Based on decarbonization in biomass gas application of immobilized ionic liquid membrane, a series of exploratory work was done to improve the performance of immobilized ionic liquid membrane, the target of which is improving gas permeability and pressure stability in order to attempt to break through the bottleneck of the industrialization of the supported ionic liquid membrane. The specific research work and conclusions were listed as follows:1. Firstly,1-alkyl-3-methyl imidazoles ionic liquid with different carbon chain length was selected to prepare traditional supported room temperature ionic liquid membrane. The membrane permeability was examined to find out internal cause and external cause affecting CO2permeability and CO2/CH4selectivity. The microporous membrane matrix was not accompanied by qualitative change of physical properties and chemical properties after soaking room temperature ionic liquids, it only provides for impregnation of room temperature ionic liquids and for gas separation operation, and barely affects CO2/CH4gas permeability of the traditional of room temperature ionic liquid membrane; Selection of cation and anion in the ionic liquid significantly affected permeability of ionic liquid membrane, Selection of anion directly affect the viscosity of ionic liquids and significantly improve permeability of ionic liquid membrane; Selection of cation will also affect the density and viscosity of ionic liquids, as density gradually decreases and the viscosity gradually increases with the chain length increase of imidazole cation alkyl. The both situations affect the permeation of ionic liquid membrane collaboratively; The influence on permeation of transmembrane pressure difference is small in this section, the results indicated that the mechanism involved in gas permeation in common room temperature ionic liquid membrane is single dissolve-diffusion mechanism, while facilitated transport mechanism not involved.2. Poly (ionic liquid) was synthesized by free radical polymerization method and ion exchange method, and composite immobilized ionic liquid membrane was finally prepared by doping poly (ionic liquid) into the appropriate room temperature ionic liquids with corresponding anion. By1H nuclear magnetic resonance (NMR) analysis of poly (ionic liquid), the results was in accord with the literature data, which indicated the synthetic process is successful; The permeability study on composite immobilized ionic liquid membrane shows that, skeleton cations, which can weakly interact with CO2, are introduced in gas permeation process after doping poly (ionic liquid) into immobilized ionic liquid membrane. This strategy makes the CO2gas molecules facilitated transport by skeleton cations in the immobilized ionic liquid membrane, not including those CO2gas dissolved selectively and diffused in the ionic liquid phase.3. The surface of hydrophilic PVDF membrane was modificated using3-aminopropylriethoxysilane (APTES) to prepare new immobilized ionic liquid membranes. Then, the membrane material was investigated by SEM, IR and Homemade laboratory gas permeability tester. The PVDF matrix morphology maintains very well with uniform pore size distribution neat and the characteristics of high porosity after surface modification by APTES. Through infrared spectra analysis, a new absorption peak appeared around1560cm-1after surface modification of PVDF membrane, which is caused by N-H bending vibration. The results indicated that PVDF surface modification was productive; CO2/CH4gas permeability of the immobilized ionic liquid membrane was tested after the modification, and compared with performance of traditional room temperature ionic liquid membrane:The functionalization of hole wall on microporous matrix of immobilized ionic liquid membrane introduces fixed carrier site that can reversibly react with CO2in the gas permeation process, which result in the double penetration transfer behavior of CO2gas after microporous matrix modification of immobilized ionic liquid membrane. Through surface modification of the hydrophilic membrane, this effective strategy succeeds in improving the CO2gas permeability with high CO2selectivity.4. PIM1, polymers of intrinsic microporosity, was synthesized using the polycondensation ways. Composite immobilized ionic liquid membrane was in situ prepared containing polysulfone, PIM1and ionic liquid. The results of1H nuclear magnetic resonance (NMR) spectra were in accordance with the literature data; Gas permeation performance indicated that PIM1can effectively improve gas permeability of organic polymer membrane, doping two kinds of ionic liquids of suitable amount into mixed membrane system can improve gas permeation selectivity of immobilized ionic liquid membrane. This strategy provides some experience for the subsequent development of immobilized ionic liquid membrane. |
PDF Full Text Request