Preparation and gas permeation properties on pure silica CHA-type zeolite membranes

Abstract

Pure silica CHA-type zeolite (Si-CHA) membranes were synthesized by a hydrothermal secondary growth method on porous α-alumina supports. Using Si-CHA seed crystals as a crystalline nuclei allowed the formation of a dense Si-CHA layer. The Si-CHA membranes prepared in this study showed excellent gas permeance derived from their large pore volume and effective molecular sieve performance for gas separation. The Si-CHA membranes exhibited excellent H 2 and CO 2 permeance of 1.1 × 10 −6 and 1.7 × 10 −6 mol/m 2 sPa, respectively. The ideal selectivity of H 2 /CH 4 and CO 2 /CH 4 were 34 and 54, respectively. The stability test in the presence of water vapor on the Si-CHA membranes was performed and the Si-CHA membranes demonstrated good water vapor resistance, more so than the topologically analogous aluminosilicate zeolite membrane (SSZ-13). The Si-CHA membranes were unlikely to present pore blockages by water adsorption because of their hydrophobic pore systems.

Single Gas Permeance Performance of High Silica SSZ-13 Zeolite Membranes

“…Generally, high silica zeolite membrane had few defects, pinholes and a good gas separation performance [20,29], and Si-CHA zeolite membrane had better vapor resistance than the topologically analogous SSZ-13 zeolite membrane [21]. In order to investigate effects of SiO 2 /Al 2 O 3 ratio on the growth and gas separation performance of SSZ-13 zeolite membrane, which were prepared from different SiO 2 /Al 2 O 3 ratio precursor synthesis gels (SiO 2 /Al 2 O 3 = 40~∞).…”

“…Generally, the Si-CHA or high silica SSZ-13 zeolite membrane were prepared from the concentrated synthesis gel, for example, H 2 O/SiO 2 ratio of initial synthesis gel was only 5.7 [21]. In addition, H 2 O/SiO 2 ratio had great effects on the concentration of each component in precursor synthesis gel, including the alkalinity of synthetic mixture.…”

“…Inorganic membranes have good hydrothermal stability, mechanical strength, and chemical resistance, which are promising candidates for gas separation [8]. Recently, zeolite membranes, such as zeolite T, DDR, MFI, CHA, and metal-organic framework (MOF) membranes have gained much attention for natural gas purification [8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23]. …”

“…SSZ-13 zeolite membranes had good selectivity and permeance for CO 2 /CH 4 separation [3,21,22]. In particular, the high-silica zeolite membrane had low polarity and few non-zeolitic molecular trafficking pathways [25,26,27].…”

“…In order to prepare a high silica SSZ-13 zeolite membrane, the SiO 2 /Al 2 O 3 ratio of the initial synthesis gel was up to 40 in our previous study [3]. Kida et al had successfully prepared the pure silica CHA-type zeolite membrane, and the synthesis procedure was complicated; for example, the H 2 O/SiO 2 ratio of initial synthesis gel was only 5.7 [21]. A low H 2 O/SiO 2 ratio means high costs of membrane preparation, which would affect the industrial application of an SSZ-13 zeolite membrane.…”