Park, Sanha Lee, Minseong Hong, Sungwon Jeong, Yanghwan Kim, Dongjae Choi, Nakwon Nam, Jaewook Baik, Hionsuck Choi, Jungkyu 2024-01-19T10:03:26Z 2024-01-19T10:03:26Z 2023-05-11 2023-02 0376-7388 https://pubs.kist.re.kr/handle/201004/113996 We report that low-temperature ozone calcination allowed MFI type polycrystalline zeolite membranes to maximize theirp-/o-xylene separation factor (as high as ca. 2000) by suppressing defect formation. Conventional high-temperature calcination and rapid thermal processing, which provide poor and marked p-/o-xylene sepa-ration abilities, respectively, were used for comparison. The corresponding defect structures were quantitatively analyzed by image processing of fluorescence confocal optical microscopy images combined with membrane permeation modeling, revealing the main defects (grain boundary defects and cracks) and their tortuosity, porosity, and size. To the best of our knowledge, we, for the first time, demonstrated that in contrast to common belief, the minor portion of wider cracks instead of the major portion of narrower grain boundary defects determined the final permeation rates. Specifically, the MFI membrane prepared by high-temperature calcination contained many grain boundary defects (narrow; ca. 1 nm) and few cracks (wide; ca. 20 nm) that accounted for ca. 0.1% and 99.8%, respectively, of the slowly permeating o-xylene molar flux. In contrast, the ozone-treated MFI membranes, which only possessed grain boundary defects, achieved the high p-/o-xylene separation per-formance, underlining the need for the selective reduction in the number of wider cracks rather than ubiquitous, narrow grain boundary defects. English Elsevier BV Low-temperature ozone treatment for p-xylene perm-selective MFI type zeolite membranes: Unprecedented revelation of performance-negating cracks larger than 10 nm in polycrystalline membrane structures Article 10.1016/j.memsci.2022.121212 1 Journal of Membrane Science, v.668 Journal of Membrane Science 668 N scie scopus 000975717500001 2-s2.0-85146247967 Engineering, Chemical Polymer Science Engineering Polymer Science Article MICROSTRUCTURAL OPTIMIZATION TEMPLATE-REMOVAL GAS PERMEATION SEPARATION DIFFUSION CO2 HYDROCARBONS TRANSPORT DEFECTS ISOMERS Zeolite membranes Grain boundary defect Crack Fluorescence confocal optical microscopy (FCOM) Xylene isomer separation