Preparation of high-permeance MFI membrane with the modified secondary growth method on the macroporous α-alumina tubular support

State Key Laboratory of Fine Chemicals, Institute of Adsorption and Inorganic Membrane, Dalian University of Technology, Dalian 116012, China
Journal of Membrane Science (Impact Factor: 5.06). 07/2008; 320(1-2):303-309. DOI: 10.1016/j.memsci.2008.04.035


MFI membrane with high permeance was successfully synthesized on the macroporous (pore size of 3–4 μm) α-Al2O3 tubular support with a novel modified secondary growth method. Before the crystallization, the seeded support was wrapped with Teflon tape in order to focalize the growth of crystals in the region of seed layer. The as-synthesized membrane was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and single-gas permeation testing. The results indicated that the as-synthesized membrane had a thickness of 6–8 μm similar to the thickness of the seed layer and exhibited high gas permeance. At room temperature, the permeance of H2 and the ideal separation factor of H2/SF6 reached 1.64 × 10−6 mol m−2 s−1 Pa−1 and 71, respectively. The permeance of single-gas increased with the increasing of temperature. The ideal separation factors of H2/i-C4H10 and H2/SF6 decreased with the increasing of temperature from 298 to 473 K. At 473 K, the ideal separation factors of H2/i-C4H10 and H2/SF6 were 12.16 and 11.08, which were still higher than their Knudsen ratios of 5.39 and 8.54, respectively.

1 Follower
9 Reads
  • [Show abstract] [Hide abstract]
    ABSTRACT: High performance silicalite-1 membranes on outer surface of macroprous α-Al2O3 supports were synthesized by counter-diffusion secondary growth (CDSG). Different from the conventional synthesis methods by which the silica source (tetraethyl orthosilicate) and the template agent (tetra-propyl ammonium bromide) were mixed together to form the synthesis solution, this method introduced silica source and template agent from the opposite direction of a support wall, resulting in good membrane structures and properties as well as reduced chemical consumption. The correlation between particle size of seeds and the pore size of supports was optimized, and its influence on the morphology and permeation property of the as-prepared membranes was also investigated. Results showed the as-prepared membranes were typical silicalite-1 membranes without any other phase. The membranes were dense, continuous without obvious defects, displaying good permeation property. The H2 permeance and H2/SF6 ideal permselectivity for the membrane prepared under optimized parameters were up to 7.5×10−7molm−2s−1Pa−1 and 103 at 298K under 0.1MPa pressure drop, respectively. Moreover, by the CDSG method the consumption of the template can be greatly reduced.
    No preview · Article · Dec 2009 · Journal of Membrane Science
  • [Show abstract] [Hide abstract]
    ABSTRACT: A tailor-made silicalite-1 membrane encapsulated catalyst with a size in millimeters has been directly synthesized over the activated-carbon supported Rh catalyst pellet to form a core–shell structure (S1/Rh/A.C.) by a hydrothermal synthesis method. For the reaction of hydroformylation of 1-hexene, the encapsulated catalysts present perfect catalytic performance for both the conversion and the normal to iso ratio of the aldehyde products. Increasing in the thickness of the silicalite-1 membrane can improve the selectivity of the normal products, but the reaction conversion decreases significantly. However, the modification of the encapsulated catalyst by tetraethyl orthosilicate (TEOS) can reduce the zeolite crystalline gaps to improve the normal aldehyde selectivity and to keep the similar 1-hexene conversion compared with that of the S1/Rh/A.C. catalyst. This encapsulated catalyst is efficient to produce and separate the aimed product from the multiple products in one-step with the spatial confined structure of the catalytic-inert silicalite-1 membrane.
    No preview · Article · Feb 2010 · Journal of Membrane Science
  • [Show abstract] [Hide abstract]
    ABSTRACT: A specific synthesis mode, based on precursor diffusion through the support channels, the restricting growth method (RGM) with ultra-dilute precursor has been designed to prepare silicalite-1 zeolite membranes on seeded macroporous α-Al2O3 tubular supports. Several parameters were systematically investigated to evaluate their influence on performance of the membranes, including the H2O/SiO2 ratio, template type and crystallization temperature. X-ray diffraction (XRD), scanning electron microscopy (SEM) and single-gas permeation tests were used to characterize the as-prepared membranes. Results showed the membrane prepared under optimum parameters (H2O/SiO2 ratio of 800, TPAOH as template and crystallization at 443 K) was continuous, dense and with a controllable section thickness almost the same as that of the seed layer. It displayed preferable hydrogen permeance (1.2 × 10−6 mol m−2 s−1 Pa−1) and permselectivity (αH2/SF6 = 134) at 298 K under 0.1 MPa pressure drop. Moreover, due to the utilization of ultra-dilute precursor, this technique has the advantage of reduced chemical consumption. On the contrary, the uncompacted membranes with poor permeation behavior were obtained by the conventional secondary growth method under the same synthesis parameters.
    No preview · Article · Apr 2010 · Microporous and Mesoporous Materials
Show more