NaP1 zeolite membranes with high selectivity for water-alcohol pervaporation
JC Guo and CL Zou and CY Chiang and TA Chang and JJ Chen and LC Lin and DY Kang, JOURNAL OF MEMBRANE SCIENCE, 639, 119762 (2021).
Membrane pervaporation is an emerging technique for the separation of water from alcohols, and zeolites with ordered ultramicropores (pore size <0.7 nm) have shown particular promise for use as membrane materials. This is the first paper to propose the use of NaP1 zeolite in membrane pervaporation. NaP1 zeolite has a GIS type topology with an 8-member ring that forms a pore limiting diameter of 3.0 angstrom, which is ideal for the separation of water from alcohols. NaP1 zeolite membranes with various Si/Al ratios (1.9, 3.3, and 3.9) were made via the seeded growth. Pervaporation tests were performed using an aqueous feed solution of 90 wt% ethanol or IPA at 348 K. The sample with a Si/Al ratio of 3.3 achieved separation factors surpassing most existing zeolite membranes: water/ethanol (200,000) and water/isopropanol (36,000). Nano-beam X-ray diffraction was used to map grain sizes in membrane samples, due to its role in surface hydrophilicity. State-of- the-art molecular simulations provided valuable insights into the diffusion and adsorption of water/alcohol molecules in NaP1 zeolite. From simulations, NaP1 zeolite presented a high water diffusivity and a high adsorption selectivity of water over ethanol or isopropanol. Experiment and computation results demonstrate the potential of NaP1 zeolite as a membrane material for alcohol dehydration.
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