Synthesis and sonication-induced assembly of Si-DDR particles for close-packed oriented layers

Abstract

Here, we report a seeded growth protocol for synthesizing monodisperse Si-DDR particles of ~1.3-10 μm by varying the seed amount. These Si-DDR particles were deposited onto porous α-Al2O3 discs via sonication-induced assembly, constituting close-packed h0h-oriented layers.

DDR-type zeolite membrane synthesis, modification and gas permeation studies

“…The width of the cracks ranged from 50 nm to 200 nm that explains the predominant Knudsen diffusion gas transport behavior. Kim et al [10] observed very similar cracks formed in α-alumina supported pure-silica DDR membranes, which likely caused the membrane's poor gas permselectivity. In the current membrane, the inclusion of the Sigma-1 seeds in the zeolite layer might also have played a role in crack development during the thermal treatment that needs to be further investigated in the future.…”

“…Kim et al used the DDR-seeded secondary growth method to synthesize DDR membrane and the membrane exhibited no permeation selectivity between CO 2 and N 2 (i.e. selectivity ~ 1) [10] which differs qualitatively from the values of >10, which were experimentally obtained by Tomita et al [1] and theoretically predicted by Krishna et al [7]. Bose et al synthesized DDR membrane by sonication mediated hydrothermal reaction [11].…”

“…The SDA removal from the small pore DDR zeolite is accomplished at very high temperature, commonly at >700 o C, that increases the risk of crack formation. Severe crack formation was observed in the puresilica DDR zeolite membranes by Kim et al that likely caused the poor permselectivity for CO 2 /N 2 [10].…”

Synthesis and characterization of all-silica DDR zeolite by microwave heating

“…Kim et al prepared Si-DDR particles of 1.3~10 mm by varying the seed amount. These Si-DDR particles were deposited onto porous a-Al 2 O 3 discs via sonicationinduced assembly, constituting close packed h0h-oriented layers [31].…”

An Hetero‐Epitaxially Grown Zeolite Membrane

“…Although alternative synthesis approaches for DDR zeolites have been proposed to reduce the reaction time and simplify the synthetic conditions, other zeolite phases such as sigma‐2 (SGT) or dodecasil 1 hexagonal (DOH) are often uncontrollably co‐synthesized, arising from the use of the same structure directing agent (1‐adamantylamine) . In addition, the particle size of DDR zeolites has a wide distribution so that it is quite difficult to produce a uniform seed layer, which is critical for the formation of a continuous membrane by epitaxial growth of seeds . Thus, the formation of continuous membranes based on the secondary growth methodology is inhibited.…”