CO₂ Separation Membranes Consisting of Ionic Liquid/CdO Composites

CuO Modified by 7,7,8,8-Tetracyanoquinodimethane and Its Application to CO2 Separation

7,7,8,8-Tetracyanoquinomethane (TCNQ) was added to polyvinylpyrrolidone (PVP)/CuO composites to modify and prevent agglomeration of the particles, and thus the CuO particles were well dispersed to a small size, thereby increasing CO₂ solubility and separation performance. When the separation performance of the PVP/CuO/TCNQ composite membrane was measured for CO₂/N₂ gases, a CO₂ separation of about 174 was measured. This improvement in performance was attributed to the fact that TCNQ was applied to PVP and CuO to prevent agglomeration between particles with surface modification. Due to TCNQ, CuO could be dispersed to a small size in PVP; the bonds between chains in PVP weakened; the interaction between molecules weakened; and the free volume increased, as confirmed by FT-IR, TGA, and UV-Vis spectroscopy.

CO2 separation using composites consisting of 1-butyl-3-methylimidazolium tetrafluoroborate/CdO/1-aminopyridinium iodide

1-Aminopyridinium iodide (iodine salt) was used in CO₂ separation composites consisting of CdO and 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM⁺BF₄⁻). Using iodine salt, the separation performance was largely improved. The CO₂/N₂ selectivity was 64.6 and the permeance of CO₂ gas was 22.6 GPU, which was about twice that of BMIM⁺BF₄⁻/CdO composites without addition of iodine salt. These results were due to the both effect of iodine salt on the transport of the N₂ molecules by the cyclic ring compound and the promoting transport of CO₂ molecules by the amine groups. Moreover, the oxide layer on the surface of the CdO could enhance the CO₂ solubility, resulting in the enhancement of separation performance. The mechanical and chemical properties were measured using SEM, Raman, TGA and FT-IR. The cross-section of coated membranes was confirmed by SEM. The coordinative interactions of iodine salts with BMIM⁺BF₄⁻/CdO composite were observed by Raman.

Variations of thermophysical properties and heat transfer performance of nanoparticle-enhanced ionic liquids

The ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([EMIm]Ac) was investigated as a promising absorbent for absorption refrigeration. To improve the thermal conductivity of pure [EMIm]Ac, IL-based nanofluids (ionanofluids, INFs) were prepared by adding graphene nanoplatelets (GNPs). The thermal stability of the IL and INFs was analysed. The variations of the thermal conductivity, viscosity and specific heat capacity resulting from the addition of the GNPs were then measured over a wide range of temperatures and mass fractions. The measured data were fitted with appropriate equations and compared with the corresponding classical models. The results revealed that the IL and INFs were thermally stable over the measurement range. The thermal conductivity greatly increased with increasing mass fraction, while only slightly changed with increasing temperature. A maximum enhancement in thermal conductivity of 43.2% was observed at a temperature of 373.15 K for the INF with a mass fraction of 5%. The numerical results revealed that the dispersion of the GNPs in the pure IL effectively improved the local heat transfer coefficient by up to 28.6%.