Thin SAPO-34 membranes synthesized in stainless steel autoclaves for N2/CH4 separation

Abstract

SAPO-34 membranes were synthesized in stainless steel autoclaves and Teflon autoclaves with water bath, ice/water bath and flowing water cooling towards N 2 /CH 4 separation. The best membrane displaying unprecedented N 2 permeance of ~2,600 GPUs and N 2 /CH 4 separation selectivity of 7.4 was prepared in the stainless steel autoclave with a water bath cooling. A more selective membrane with a N 2 /CH 4 selectivity of 8.6 and N 2 permeance of ~2,150 GPUs was also prepared in the stainless steel autoclave but with an ice/water bath cooling. The heat flux rate of the stainless steel autoclaves during membrane preparation was ~two orders of magnitude higher than that of the membranes prepared in conventional Teflon autoclaves. The higher heat flux rate decreased the gel temperature faster, and slowed the kinetics of crystal growth. The slow crystal growth rate during the cooling translated into thinner and more permeable membranes. These SAPO-34 membranes may have great potential for economic N 2 rejection from natural gas.

Synthesis and Gas Separation of Chabazite Zeolite Membranes

“…Carreon、Yu 和 Funke 等 [35][36][37][38][39][40] 有着多年的研究经验, 成功制备出对轻质气体具有良好分离效果的 SAPO-34 膜, 国内的顾学红、张延风等 [41][42][43][44] [46] 。基于微波 加热法, Hu 等 [47] 制备出薄(厚度为 4 μm)且致密的 图 2 CHA 分子筛膜制备方法流程示意图 Fig. 2 Schematic diagrams of CHA zeolite membrane preparation methods [50][51] , 且其作为陶瓷材料与分子筛性质相似, 更易于膜层生长 [52] 。 针对 SSZ-13 膜, 周荣飞等 [27,31] 基于莫来石管合成了致密的 SSZ-13 膜, Kosinov 和 Lee 等 [14,[24][25] 基于管状、片状 α-氧化铝合成了性能 良好的 SSZ-13 膜。针对 SAPO-34 膜, 载体主要集 中在 α-氧化铝上, 如 Chen 和 Liu 等 [41,[53][54][55] [37,58] , 已有诸多文章报道了纳米 CHA 晶种的合 成方法 [59][60][61][62][63] , 亦有通过球磨方式将常见微米级 CHA 晶体研磨至纳米尺寸作为晶种, 虽所得晶种形状不 定, 但因仍保有 CHA 晶型而能够起到诱导合成的 作用。 Kosinov 等 [14] 将~10 μm SSZ-13 晶粒球磨得到 120 nm 的 晶 种 , 制 备 出 分 离 性 能 良 好 的 致 密 SSZ-13 膜; Huang 等 [40] 还发现使用大长径比的片状 [67] (图 3)。Bohström 等 [68] [14,24,[26][27] [41,53,66] , 后者基本在 170~190 ℃, 160 ℃下晶 化则会生成 AEI 沸石杂相 [69] 。 2)晶化时间。 晶化时间与 CHA 分子筛膜层的结 晶度与厚度密切相关, 通常要与晶化温度配合选取, 晶化时间过短会导致膜层不完整, 晶化时间过长会 使厚度过大(图 3)。 针对 SSZ-13 膜合成, 150~ 170 ℃ 下晶...…”

Porous aluminophosphates as adsorbents for the separation of CO2/CH4and CH4/N2mixtures – a Monte Carlo simulation study

“…22 In addition to studies aiming at the use of AlPOs/SAPOs in adsorption-based separations, some groups have also prepared AlPO or SAPO membranes for potential applications in separations of methane-containing mixtures. [24][25][26][27][28][29][30][31][32][33][34][35] These efforts have mainly addressed frameworks with eight-membered ring pore apertures, especially AEI-type AlPO-18 and CHA-type SAPO-34, because the diffusion of CO 2 or N 2 (kinetic diameters d kin of 3.30 Å and 3.64 Å, respectively 3 ) through these windows is faster than the diffusion of CH 4 (d kin = 3.80 Å). Since CO 2 is more strongly adsorbed than CH 4 , the combination of stronger adsorption and faster diffusion of carbon dioxide affords high CO 2 /CH 4 membrane selectivities: For example, Wang et al…”

“…were obtained for AlPO-18 and SAPO-34 membranes, respectively. 32,34,35 A preliminary economic assessment indicated that a membrane-based separation using SAPO-34 could be competitive to cryogenic distillation for small nitrogen-contaminated gas wells. 32 Computational studies using force-field based simulation methods have delivered valuable insights into the adsorption and diffusion of guest molecules in zeolites and related porous materials.…”

Porous Aluminophosphates as Adsorbents for the Separation of CO2/CH4 and CH4/N2 Mixtures – a Monte Carlo Simulation Study

“…22 In addition to studies aiming at the use of AlPOs/SAPOs in adsorption-based separations, some groups have also prepared AlPO or SAPO membranes for potential applications in separations of methane-containing mixtures. [24][25][26][27][28][29][30][31][32][33][34][35] These efforts have mainly addressed frameworks with eight-membered ring pore apertures, especially AEI-type AlPO-18 and CHA-type SAPO-34, because the diffusion of CO 2 or N 2 (kinetic diameters d kin of 3.30 Å and 3.64 Å, respectively 3 ) through these windows is faster than the diffusion of CH 4 (d kin = 3.80 Å). Since CO 2 is more strongly adsorbed than CH 4 , the combination of stronger adsorption and faster diffusion of carbon dioxide affords high CO 2 /CH 4 membrane selectivities: For example, Wang et al…”