Abstract
The mixture of the ionic liquid 1-ethyl-3-methylimidazolium acetate (EmimAc) and dimethylsulfoxide (DMSO) was employed to dissolve microcrystalline cellulose (MCC). A 10 wt % cellulose dope solution was prepared for spinning cellulose hollow fibers (CHFs) under a mild temperature of 50 °C by a dry–wet spinning method. The defect-free CHFs were obtained with an average diameter and thickness of 270 and 38 µm, respectively. Both the XRD and FTIR characterization confirmed that a crystalline structure transition from cellulose I (MCC) to cellulose II (regenerated CHFs) occurred during the cellulose dissolution in ionic liquids and spinning processes. The thermogravimetric analysis (TGA) indicated that regenerated CHFs presented a similar pyrolysis behavior with deacetylated cellulose acetate during pyrolysis process. This study provided a suitable way to directly fabricate hollow fiber carbon membranes using cellulose hollow fiber precursors spun from cellulose/(EmimAc + DMSO)/H2O ternary system.
Highlights
Membrane systems possess many advantages, such as small footprint, low capital and operating costs, being environmentally friendly, no-moving part for the separation as such, and exhibiting process flexibility, which attracts great interest in different gas separations, such as air separation, natural gas sweetening, and biogas upgrading
The ionic liquid of ethyl-3-methylimidazolium acetate (EmimAc) was identified as a good solvent for cellulose
The ionic liquid of EmimAc was identified as a good solvent for cellulose dissolution, dissolution, and defect-free cellulose hollow fibers (CHFs) were successfully fabricated from a dope solution of 10 wt %
Summary
Membrane systems possess many advantages, such as small footprint, low capital and operating costs, being environmentally friendly, no-moving part for the separation as such, and exhibiting process flexibility, which attracts great interest in different gas separations, such as air separation, natural gas sweetening, and biogas upgrading. Polymer membranes have several limitations for the application in harsh conditions, such as natural gas sweetening, and their relatively low separation performance was found to be caused by membrane compaction and plasticization. Carbon membranes with high mechanical strength can potentially operate at high pressure without having significant loss of separation performance. Carbon membranes are ultra-microporous inorganic membranes prepared mainly by carbonization of polymeric precursors, and typically form a graphitic or turbostratic structure, which presents high mechanical strength and moderate modulus compared to the graphitized fibers. Mainly polyimides (PI) and cellulose derivatives, have been used for preparation of carbon membranes [1,2,3]. Our previous cellulosic-derived carbon membranes showed high CO2 /CH4 selectivity, but relatively low CO2 permeance (
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