Abstract
In this study, an NaA-type zeolite membrane was prepared, and the dehydration performances of the membrane were determined by the pervaporation for several organic solvents to understand the lower dehydration performances of zeolite membranes for NMP solutions than those for alcohols. For a 90 wt% ethanol solution at 348 K, the permeation flux and separation factor of the membrane were 3.82 kg m−2 h−1 and 73,800, respectively. The high dehydration performances were also obtained for alcohols and low boiling solvents (acetonitrile, acetone, methyl ethyl ketone (MEK) and tetrahydrofuran (THF)). However, the permeation flux and separation factors decreased significantly for high boiling solvents, such as N,N-dimethylacetamide (DMA), N,N-dimethyl formamide (DMF), dimethyl sulfoxide (DMSO) and N-methyl-2-pyrrolidone (NMP). The influences of the water content and temperature on the dehydration performances for the NMP solutions were determined to understand the lower dehydration performances for those solvents. Those results suggest that the lower dehydration performances for the high boiling solvents were attributed to the lower vapor pressures of water and the higher permeances of those solvents. Furthermore, this study proposes that the permeation behaviors through zeolite membranes could be understood by the determination of the effect of temperature on the permeance of individual components.
Highlights
Membrane separation is a promising energy-saving separation technology
It is well known that NaA-type zeolite membranes have been used for the dehydration and concentration of biomass-derived ethanol commercially [2,5,7,8,9,10,11]
Sommer et al [7,8] determined the dehydration performances of the NaA-type zeolite membrane for several organic solvents, such as alcohols, acetone, and tetrahydrofuran (THF), and the permeation flux were proportional to the partial vapor pressure of water for those solvents
Summary
Membrane separation is a promising energy-saving separation technology. In particular, zeolite membranes showed high dehydration performances for organic solvents [1,2,3,4,5,6,7,8,9,10,11,12]. Zeng et al [11] applied the NaA-type zeolite membrane to the dehydration of NMP Their membranes showed the permeation flux of 1.5 kg m−2 h−1 and the separation factor of more than 10,000 for a 90 wt% 2-propanol solution at 353 K [12]. The porous α-alumina tube (eSep Corp., Kyoto, Japan) was used as the support in this study, and the properties were as follows: outer diameter = 12 mm; inner diameter = 9 mm; length = 50 mm; mean pore diameter = 3 μm; porosity = 55%) Both the ends of the tube were capped with silicone rubber, and the tube was impregnated into the seed particle solution at room temperature for 1 min. The 1 cm long membrane was used for characterization, and the other was used for the pervaporation experiments
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