Abstract
Because of the preferential butanol selectivity of some ionic liquids (ILs), an increasing amount of research has appeared regarding their application in butanol separation. In this research, two ionic liquids, namely, 1-ethyl-3-vinylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([EVIM][Tf2N], IL1) and N-octyl-pyridinium bis[(trifluoromethyl)sulfonyl]imide ([OMPY][Tf2N], IL2), were applied to modify a mesoporous molecular sieve MCM-41. The IL-modified MCM-41 samples were characterized by XPS, BET, XRD, SEM and TEM. The ionic liquid-modified MCM-41 was incorporated into the polymer PEBA to prepare mixed matrix membranes to study the influences of the filling of IL-modified MCM-41 and operating conditions on the performance of the mixed matrix membrane for butanol pervaporation. The results indicated that the pervaporation performance of the PEBA membrane was enhanced by the incorporation of IL-modified MCM-41. When the temperature of the feeding liquid was 35°C and the mass fraction of butanol was 2.5 wt%, the 5% MCM-41-IL2-PEBA membrane showed a permeation flux of 421.7 g m−2 h−1 and a separation factor of 25.4. The permeation flux and the separation factor of the membrane increased as the temperature of the feeding liquid increased. The results of the long-period experiment suggested that the 5% MCM-41-IL2-PEBA membrane exhibited high stability within 100 h of operation.
Highlights
As a novel biomass fuel, bio-butanol has a better energy density and performance than bioethanol [1]
The thermogravimetric (TG) analyses of PEBA, 5% MCM-41-PEBA, 5% MCM-41-ionic liquids 1-ethyl-3-vinylimidazolium bis[(trifluoromethyl)sulfonyl]imide (IL1)-PEBA, and 5% MCM-41-IL2-PEBA are shown in figure 8, which indicate that the PEBA membrane was highly thermostable because it started decomposing at approximately 210°C
XPS characterization results indicated that ionic liquids (ILs)-specific elements S and F were observed in IL-modified molecular sieves
Summary
As a novel biomass fuel, bio-butanol has a better energy density and performance than bioethanol [1]. The added inorganic porous materials for the separation of organic compounds are usually hydrophobic materials including Silicalite-1 [11,12,13], ZSM-5 [14,15,16], carbon molecular sieve (CMS) [17], carbon nano tubes (CNTs) [18,19], carbon black [5,20] and MOFs [21] These compounds can preferentially adsorb organic molecules or provide diffusion channels to improve the selectivity or permeation flux because of the good hydrophobic effect, the high specific surface area and pore volume. To improve the permeation flux and separation factor of the pervaporation membrane for butanol aqueous solutions simultaneously, in this study, two ionic liquids with the hydrophobic anion [Tf2N]− were selected to couple with a MCM-41 mesoporous sieve to prepare IL-modified MCM-41. Afterwards, pervaporation experiments were conducted to evaluate the membrane performance and stability of the mixed matrix membranes
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