Highly Oriented Thin Membrane Fabrication with Hierarchically Porous Zeolite Seed

Abstract

Nanosized zeolite is widely used as seed for high quality zeolite membranes fabrication, while its complicated synthesis routine limits large-scale productions. In this work, a non-nanosized cubic hierarchically porous TS-1 zeolite (HTS-1), obtained by basic hydrothermal treatment of conventional ellipsoid solid TS-1, is used as seed to prepare highly oriented thin membranes. A capillary condensation phenomenon resulting from the unique hierarchically porous structure benefits gel attachment. Moreover, abundant ledges, kinks, and terraces on the HTS-1 surface promote epitaxial growth of the membrane. In contrast, the solid TS-1 seed induces intergrowth dominantly, which results in a thick TS-1 membrane. The HTS-1 membrane demonstrates superior CO2/N2 separation properties compared to the TS-1 one. It associates with thin oriented membrane morphology, leading to exposure of a high Miller index surface and less diffuse distance and tortuosity. The results suggest beneficial effects of a hierarchically porous TS-1 zeolite seed on the interfacial crystal growth for membrane fabrication. A similar conclusion is applicable to the case of a hierarchically porous zeolite β. This work develops a facile approach to obtain a highly oriented thin zeolite membrane with enhanced separation properties.

Hierarchy Control of MFI Zeolite Membrane towards Superior Butane Isomer Separation Performance

“…The above results are consistent with the conclusion drawn by Liu et al. who reported the positive effect of using hierarchical TS‐1 zeolite seeds on preferred orientation control of TS‐1 zeolite membranes [13a] . Anyway, our experimental results convincingly demonstrated the necessity of concurrent use of hollow‐structured MFI nanoseeds and single‐mode microwave heating for the preparation of ultra‐thin MFI zeolite membrane with higher degree of ( h 0 h )‐preferred orientation.…”

Effects of Seed Crystals on the Growth and Catalytic Performance of TS-1 Zeolite Membranes

“…Compact and good catalytic performance TS-1 membranes have been successfully prepared by in-situ or secondary growth hydrothermal synthesis [13][14][15]. Secondary growth hydrothermal synthesis, a layer of seeded zeolites is coated on suitable support before crystallization, which is an effective way for shortening the crystallization time and preparing high-quality zeolite membranes [16][17][18][19][20]. In addition, the secondary growth could suppress the transformation from nucleation to other phase crystals.…”

“…Zhu et al first prepared the Ti-MWW zeolite membrane by secondary hydrothermal synthesis, and the membranes showed good catalytic performance for phenol hydroxylation [17]. Liu et al synthesized the highly oriented, thin, and hierarchically porous TS-1 zeolite membrane by secondary hydrothermal treatment [18]. Wang et al synthesized the Ti-containing membrane using nanosized silicalite-1 particles as seeds by hydrothermal treatment; the membranes showed large proportions of tetrahedrally coordinated titanium and excellent hydrothermally stability [19].…”

Fabrication of the Hierarchical HZSM-5 Membrane with Tunable Mesoporosity for Catalytic Cracking of n-Dodecane

“…However, it should be noted that the diameters of the crystalline grains were above 2 µm, in their studies, thus, the intracrystal diffusion limitation was still a problem that needed to be improved. Liu et al prepared a hierarchically porous TS-1 zeolite membrane, through a secondary growth method, using desilicated TS-1 powder as seed, and the hierarchical membrane exhibited a superior CO 2 /N 2 separation properties, in comparison to the conventional one [19]. Wang et al created mesopores in the HZSM-5 membrane with NaOH-treatment and then employed the membrane for catalytic cracking of supercritical n-dodecane.…”