Abstract
Separation of carbon dioxide (CO2) from methane (CH4) using polymeric membranes is limited by trade-off between permeability and selectivity as depicted in Robeson curve. To overcome this challenge, this study develops membranes by incorporating silica particles (Si) modified with [EMIM][Tf2N] ionic liquid (IL) at different IL:Si ratio to achieve desirable membrane properties and gas separation performance. Results show that the IL:Si particle has been successfully prepared, indicated by the presence of fluorine and nitrogen elements, as observed via Fourier-Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectrometer (XPS). Incorporation of the modified particles into membrane has given prominent effects on morphology and polymer chain flexibility. The mixed matrix membrane (MMM) cross-section morphology turns rougher in the presence of IL:Si during fracture due to higher loadings of silica particles and IL. Furthermore, the MMM becomes more flexible with IL presence due to IL-induced plasticization, independent of IL:Si ratio. The MMM with low IL content possesses CO2 permeance of 34.60 ± 0.26 GPU with CO2/CH4 selectivity of 85.10, which is far superior to a pure polycarbonate (PC) and PC-Sil membranes at 2 bar, which surpasses the Robeson Upper Bound. This higher CO2 selectivity is due to the presences of CO2-philic IL within the MMM system.
Highlights
Natural gas is among the favorable energy sources due to its low greenhouse gases emissions than other fossil fuels
The effect of Ionic liquids (ILs):Si ratio on the modified silica particles incorporated in PC polymer matrix was thoroughly investigated and discussed
The IL-modified silica has been successfully prepared as indicated from fluorine functional group from XPS and FTIR spectra
Summary
Natural gas is among the favorable energy sources due to its low greenhouse gases emissions than other fossil fuels. Due to limitations of chemical absorption and cryogenic separation (i.e., high operating cost, process complexity and energy intensive), membrane technology for CO2 removal is a promising technique. It offers low operating and capital costs, ease of installation and operation, minimal energy consumption, and low footprint [5]. Hudiono et al [29] impregnated zeolite SAPO-34 using [EMIM][Tf2N] and incorporated it into a poly(RTIL) membrane They reported an increase of CO2 and CH4 permeability by 63% and 50% respectively, with an increase of CO2/CH4 selectivity by 11%. In this research, the IL-modified nonporous silica is utilized as inorganic fillers and the performances of the resulting MMM are evaluated. Different [EMIM][TF2N]:Silica (IL:Si) ratio were prepared to comprehend the role of IL in the resulting membrane
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