Metal-containing ionic liquids possessing bifunctional moieties were identified as efficient catalysts for the synthesis of propylene carbonate (PC) from CO 2 and propylene oxide under moderate and solvent free conditions. Density functional theory calculations were performed to rationalize the difference in catalytic activities of the metalcontaining ionic liquid catalysts (MeIm) 2 MCl 2 , where M was Fe, Cu, or Zn. (MeIm) 2 ZnCl 2 was the most efficient catalyst for the chemical fixation of carbon dioxide in terms of efficiency and environmental benignity. Process optimization using response surface methodology was performed, and the interactions between the operational variables were elucidated. The optimum reaction conditions for maximum PC yield were 4.6 h, 124 °C, and 9 bar which were obtained by a Box−Behnken design with the minimum number of reaction tests. Under the optimum reaction conditions, the predicted and validated yields of PC were 98.37 and 97.91 ± 0.02%, respectively.
Separation of CO2 from other gasses offers environmental benefits since CO2 gas is the main contributor to global warming. Recently, graphene oxide (GO) based gas separation membranes are of interest due to their selective barrier properties. However, maintaining selectivity without sacrificing permeance is still challenging. Herein, we described the preparation and characterization of nanoscale GO membranes for CO2 separation with both high selectivity and permeance. The internal structure and thickness of the GO membranes were controlled by layer-by-layer (LbL) self-assembly. Polyelectrolyte layers are used as the supporting matrix and for facilitating CO2 transport. Enhanced gas separation was achieved by adjusting pH of the GO solutions and by varying the number of GO layers to provide a pathway for CO2 molecules. Separation performance strongly depends on the number of GO bilayers. The surfaces of the multilayered GO and polyelectrolyte films are characterized by atomic force microscopy and scanning electron microscopy. The (poly (diallyldimethylammonium chloride) (PDAC)/polystyrene sulfonate (PSS)) (GO/GO) multilayer membranes show a maximum CO2/N2 selectivity of 15.3 and a CO2 permeance of 1175.0 GPU. LbL-assembled GO membranes are shown to be effective candidates for CO2 separation based on their excellent CO2/N2 separation performance.
The AgO nanoparticles were utilized for a CO2 separation membrane. The AgO nanoparticles were successfully generated in ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate (BMIMBF4) by favorable interaction between the surface of particles and the counteranion of BMIMBF4. The generated AgO nanoparticles were confirmed by TEM, and the average size was 20 nm. Coordinative interactions of dissociated AgO particles with BMIM+BF4− were investigated by FT-Raman spectroscopy. When the ionic liquid BMIMBF4 containing AgO nanoparticles was utilized as a CO2 separation membrane, the separation performance was largely enhanced.
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