无定形晶种引导三次生长制备完备性TAPO-5膜

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刘旭光, 马欣, 刘勇, 张宝泉. 无定形晶种引导三次生长制备完备性TAPO-5膜. 无机材料学报, 2015, 30(5): 555-560
LIU Xu-Guang, MA Xin, LIU Yong, ZHANG Bao-Quan. Preparation of Perfective TAPO-5 Membrane through Tertiary Growth with Amorphous Seed. Journal of lnorganic Materials,2015, 30(5): 555-560 复制到剪切板

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无定形晶种引导三次生长制备完备性TAPO-5膜

刘旭光¹, 马欣¹, 刘勇¹, 张宝泉^1,²

1. 青岛科技大学材料科学与工程学院, 青岛266042

2. 天津大学化工学院, 化学工程国家重点实验室, 天津 300072

摘要

TAPO-5膜可以通过三次生长法制备。它的完备性与所用晶种以及膜的多晶结构密切相关。393 K下晶化所得无定形晶种有利于引导制备完备性TAPO-5膜。然而, 晶态TAPO-5晶种引导制备的TAPO-5膜存在大量的裂纹(即晶界缺陷), 这破坏了膜的完备性。这些不同结果可以通过SEM、XRD 和单组分气体渗透(He)测试进行说明。它与铺展润湿法所形成的晶种层的不同形式有关。无定形晶种层的典型特征是晶种分散于载体的大孔缺陷中。然而, 晶态TAPO-5将以连续晶种层的形式存在。因此, 无定形晶种更适合引导制备完备性TAPO-5膜。

关键词: 三次生长; 无定形晶种; TAPO-5膜; 铺展润湿法

中图分类号:TQ174 文献标志码:A 文章编号:1000-324X(2015)05-0555-06

Preparation of Perfective TAPO-5 Membrane through Tertiary Growth with Amorphous Seed

LIU Xu-Guang¹, MA Xin¹, LIU Yong¹, ZHANG Bao-Quan^1,²

1. College of Materials Science and Engineering, Qingdao University of Science and Technology, Qingdao 266042, China

2. State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China

Biography: LIU Xu-Guang(1983-), male, associate professor. E-mail: liuxuguang@qust.edu.cn

Fund:Foundation item: National Natural Science Foundation of China (21136008); National Ocean Public Project of China (201405008)

Abstract

TAPO-5 membranes were synthesized through a tertiary growth method. Its perfection significantly depends on the adopted seed and itself poly-crystalline structure. Amorphous seed synthesized at a low crystallization temperature (393 K), obviously favors producing the perfective TAPO-5 membrane. TAPO-5 crystal seed, however, induces the growth of its membrane with a larger extent of cracks ( i.e., grain boundary defect), destructing itself perfection. Those diverse results are associated with the disparate seeds layers deposited by a spreading-wetting method, and consistently demonstrated by SEM, XRD, and single gas (He) permeation test. A typical feature of the amorphous TAPO-5 seed layer is its dispersive distribution pattern in the macro holes of support. A continuous layer, however, is observed for the TAPO-5 crystal seed layer. The amorphous seed is explained as a prior seed for the perfective TAPO-5 membrane.

Keyword: tertiary growth; amorphous seed; TAPO-5 membrane; spreading-wetting method

Show Figures

Aluminophosphate molecular sieves (AlPO-n), where n denotes a particular structure type, have been recognized as a novel ordered microporous materials^[1]. Their AlPO₄ frameworks are rich of structural chemistry and special physiochemical properties of isomorphous substitution by heteroatoms^[2], like metal-aluminophosphate MAPO-n (M = Ti, Fe, etc)^[3]. This enables them with excellent catalytic and separation properties. Typically, Ti incorporated AFI type aluminophosphate molecular sieve (TAPO-5, T = Ti) exhibits catalytic activities of selective oxidation, owning to its framework Ti as redox active centers^[4]. TAPO-5, as well as TS-1 membrane^[5], is of particular interests for possible applications as a catalytic or separation membrane. Its catalytic/separation membrane requires free of defects, i.e., no pinhole and cracks^[6]. Those defects will lead to short flow of reactants/feeds and fault catalytic/separation activities. Obtaining a high quality TAPO-5 membrane is critical to adopting it as the catalytic/separation membrane.

Available methods for preparing zeolite membranes include in-situ growth^[7], seeded growth^[8], and dry gel synthesis^[9]. Among those methods, the seeded growth is widely used to prepare zeolite membranes, e.g., AFI^[10], CHA^[11], and LTA^[12], because of its preferable reproducibility^[13]. The quality of the membranes prepared by the seeded growth method is considerably affected by the seeding methods, including dip-coating^[14], rubbing^[15], vacuum seeding^[16], and filtration seeding^[17]. Among these methods, the dip-coating method is easy to perform and generally adopted. The adopted seeds is paid few attentions. It depends on the crystalline nature of the seeds. Nano-sized crystals are popularly employed in the seeded growth. Amorphous seeds with a semi-crystal nature exhibits diverse induction behavior during the seed growth. This work will demonstrate that the amorphous seed is superior to the crystal seed in inducing the growth of the perfective TAPO-5 membrane. The as-synthesized TAPO- 5 membrane is activated by a mild method of catalytic hydrocracking^[18]. Its template is hydrocracked to small molecules, its perfect structure being maintained.

1 Experiments

1.1 Materials

Phosphoric acid (H₃PO₄, 85wt%), pseudoboehmite (Al₂O₃, 67wt%, Aluminum Corporation of China, Ltd, Shandong Branch), and TiOSO₄ were used as sources for phosphorus, aluminum, and titanium, respectively. Triethylamine (abbreviated as TEA) was chosen as the template for TAPO-5. These agents, except for pseudoboehmite, were all purchased from Sinopharm Chemical Reagent Co. Ltd. Homemade SiO₂/α -Al₂O₃ disc (SiO₂, 32wt%, O.D.= 20 mm^[19]) was employed as supports for the TAPO-5 membrane.

1.2 Synthesis of TAPO-5 seeds

TAPO-5 seeds were synthesized via a solid-phase transformation method with a bath composition of 0.05TiO₂:0.10H₂O₂:1.00Al₂O₃:1.10P₂O₅:1.50TEA:25.00H₂O.

Their preparation procedures were described as following. Phosphoric acid of 25.37 g weight was diluted with 18 g of ultrapure (UP) water and stirred for 10 min. Pseudoboehmite of 15.22 g weight was slowly introduced into the diluted phosphoric acid under vigorously stirring. A homogeneous Al-H₃PO₄ sol was obtained. This sol was dropped to an orange translucent TiOSO₄-H₂O₂ aqueous solution, gained by dissolving 1.05 g of TiOSO₄ in 1.13 g of H₂O₂ and diluted with 18 g of UP water. A yellow homogeneous Ti-Al-H₃PO₄ sol was obtained after stirring for 2 h, and dropped with 15.18 g of TEA. This mixture was stirred for 1 h and aged overnight as a solid gel at room temperature. The resultant solid gel was loaded into a 50 mL Teflon autoclave and crystallized at 373-433 K for 24 h. Solid products were centrifuged, washed, and dried at 333 K.

1.3 Preparation of TAPO-5 seed layers

The spreading-wetting method, basing on a dip-coating route^[14], was typically performed as following. A seed ethanol suspension was prepared through dispersing a certain amount of the TAPO-5 seeds (synthesized at 393, 413, or 433 K) in ethanol at 351 K. The seed content was chosen to be 1wt%. The supports were dipped into those suspensions for 10 s and taken out. The seeded supports were dried at 353 K for 4 h and calcined at 823K for 3 h.

1.4 Seeded growth of TAPO-5 membrane

The seeded growth was executed from a precursor sol with a bath composition of 0.05TiO₂:1.00Al₂O₃:1.10P₂O₅: 1.50TEA:105.00H₂O:0.10H₂O₂. This bath composition, with more water content, was prepared as the procedures of the TAPO-5 seed. The resultant precursor sol of volume about 11 mL was loaded into a 50 mL Teflon lined autoclave. The seeded support was placed levelly on a homemade Teflon hold, with its seeded side facing down, and immersed in that precursor sol. The secondary growth was carried out at 433 K for 48 h. After cooled to room temperature, the yield sample was removed out of the autoclave, washed with UP water, and dried at 333 K for overnight. They were utilized to a tertiary growth with the fresh precursor sol^[20]. The resultant membranes were separated from that mother sol, washed, and dried at 333 K for overnight. Activating those membranes was achieved by a Pd/SiO₂ catalytic hydrocracking method performed as following^[18]. The as-synthesized TAPO-5 membranes were loaded in the Pd/SiO₂ catalyst bed and heated to 593 K at 1 K/min, holding for 3 h, in a hydrogen flow at 593 K, before that test.

1.5 Characterization

X-ray diffraction (XRD) patterns were collected on a Rigaku D-MAX2500/PC X-ray diffractometer using Cu Kα radiation. Scanning electron microscope (SEM) images were gained through scanning electron microscopy on a FEI Nanosem 430. Single gas (He) permeation of the TAPO-5 membranes was tested via transient permeation apparatus as described in the reference of [21]. The permeance (f , mol/(m²· s· Pa)) is plotted as a function of varying average pressure (P_av) and fitted with a dusty-gas model (f = α +β · P_av, where permeability coefficients α and β are attributed to Knudsen and viscous flow, respectively^[22]).

2 Results and discussion

XRD (Fig. 1) and SEM (Fig. 2) characterization were utilized to reveal the crystal structure and morphology of the as-synthesized seeds crystallized at three temperatures (393, 413 and 433 K), respectively. The seed crystallized at 393 K displays four extremely broad reflections centered at 2θ = 15° , 28° , 38° , and 48° in Fig. 1(a), indicating a semi-crystal nature. This seed, hereinafter, is claimed as an amorphous seed. Its semi-crystal nature led to an irregular morphology of nano size, as shown in Fig. 2(a). Another seed, crystallized at an elevated temperature of 413 K, exhibits sharp diffraction peaks of an AFI structure, and some ambiguous peaks of aluminophospate (Fig. 1(b)). A certain amount of regular crystal thus is observed in Fig. 2(b). Employing a higher crystallization temperature of 433 K results in a well crystalized TAPO-5 with the AFI structure, verified by these sharp peaks (2θ = 7.4° , 21.0° , 22.5° , and 25.9° , etc.) in Fig. 1(c). This seed shows a plate- like morphology with a thickness less than 150 nm. Its high-aspect-ratio is estimated to be less than 0.2, as comparable to the reported value (0.3) of an available plate-like SAPO-5 seed^[23].

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	Fig. 1 XRD patterns of the as-synthesized TAPO-5 seeds crystallized at 393 K (a), 413 K (b), and 433 K (c)

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	Fig. 2 SEM images of the as-synthesized TAPO-5 seeds crystallized at 393 K (a), 413 K (b) and 433 K (c)

It is well known that amorphous or nano-sized zeolites exhibit high activity for inducing its membrane growth^[24]. Those seeds, crystallized at different temperatures (393, 413, and 433 K), were utilized to deposit on SiO₂/Al₂O₃ supports, and induced the growth of TAPO-5 membrane. The resulted seeds layers show distinguished XRD patterns (Fig. 3). There are obvious AFI peaks associated with the crystallized TAPO-5 seed layer (Fig. 3(c)), depositing the seed crystallized at 433 K. Both XRD patterns of the seed layers (Fig. 3(a), (b)), deposited the seeds crystallized at 393 K, or 413 K, does not show any diffraction peaks due to the AFI pattern. This is attributed to few of the amorphous TAPO-5 seeds deposited on the support.

Presence of those seeds and the toughness bare support, however, was confirmed by SEM characterization (Fig. 4). It is seen that these seeds layers show diverse distributions on supports. Most of the amorphous seed are well dispersed in the macro holes of toughness support. For the seeded support with the seed crystallized at 413 K, some of the nano particles were similarly distributed in the macro holes of support, while some of the large particles were located on the surface of support. The crystallized plate-like TAPO-5 seed, synthesized at 433 K, almost remained on the support’ s surface as a continuous layer with plenty of pinholes. Those distinguish seeds distributions may cause different growth behaviors and the quality of zeolite membrane^[25].

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	Fig. 3 XRD patterns of the seeded supports with TAPO-5 seeds crystallized at 393 K (a), 413 K (b) and 433 K (c)

Those seeded supports were performed a tertiary growth for TAPO-5 membranes. The resultant TAPO-5 membranes all exhibit typical XRD patterns owning to AFI type crystal (Fig. 5). These peaks, due to different crystal surfaces, indicate non-oriented growth of the TAPO-5 membrane. This phenomenon is obviously diverse to epitaxial growth of oriented AFI membrane on seeded smooth supports^{[20, 23]}. It is worth noting a more possible choose of that toughness support in practice. The TAPO-5 membrane, however, may not in-situ growth on the bare support^[9].

Those non-oriented TAPO-5 membranes are shown through SEM images in Fig. 6. They exhibit a continuous ploy-crystalline structure with some cracks (i.e., grain boundary defects), whatever the seeds are adopted. These cracks, destructing the perfection of the membranes, were formed in response to thermal tensile stresses^[6]. Their extent, however, associates with the adopted seeds, as seen from those SEM images. A little extent of that crack is observed for the TAPO-5 membrane seeded by the amorphous seed. A much larger extent of the crack presences in the TAPO-5 membrane seeded by the TAPO-5 crystal. That crack is noted in the cross sectional images (Fig. 6(i)), also illustrating the non-oriented ploy-crystalline structure with a thickness of 18-20 μ m. It is not observed in Fig. 6(c) of the TAPO-5 membrane seeded by the amorphous seed. Another focus is incorporating Ti into the framework of TAPO-5 membranes, as revealed by UV-vis spectra in Fig.7. Similar strong absorbtion bands between 200- 300 nm, ascribed to charger transfer of the framework Ti^{[3, 9]}, suggest negligible diverse in micro structure associated with Ti.

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	Fig. 4 SEM images of the seeded supports with TAPO-5 seeds crystallized at 393 (a), 413 (b), 433 K (c), and bare support (d)

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	Fig. 5 XRD patterns of the TAPO-5 membranes, which seeds are synthesized at 393 K (a), 413 K (b) and 433 K (c)

These seeds, with different crystallinity, obviously brings about distinguish hetero epitaxial growth behaviors of the TAPO-5 membrane on the support, and thus the diverse perfection proved by single gas permeation associated^[22].

He permeance of the as-synthesized TAPO-5 membrane, seeded with the amorphous seed, was measured o be less than 1× 10^-10 mol/(m²· s· Pa), verifying its perfection. He permeance of the as-synthesized TAPO-5 membranes, synthesized with the crystal seeds, were more than 1× 10^-7mol/(m²· s· Pa) before activation, suggesting those defective membranes. Aftertactivated by the Pd/SiO₂ catalytic hydrocracking method performed at 593 K, these membrane are tested for the He permeance and fitted with a dusty-gas model (Fig. 8). The permeance of the activated TAPO-5 membrane, seeded with the amorphous seed, is noticeably lower than those of the TAPO-5 membrane seeded with the crystals. A much smaller viscous flow coefficient (0.004) of the former TAPO-5 membrane indicates negligible defects. Both larger viscous flow coefficients (1.340 and 3.120) for the later membranes prove the grain boundary defects as revealed by the SEM images.

Those results illustrate priority of the amorphous seed on synthesizing the perfective TAPO-5 membrane. This may be associated with its high activity for inducing the inter-grown of TAPO-5 crystal and forming the polycrystalline structure^[24]. Another possible promotional effect is the dispersive distribution of the amorphous seeds in the holes of supports^[25].

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	Fig. 6 Surface and cross sectional SEM images of the TAPO-5 membranes, whose seeds are synthesized at 393 K (a, b, c), 413 K (d, e, f) and 433 K (g, h, i)

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	Fig. 7 UV-Vis diffuse reflection spectra of TAPO-5 membranes, which seeds are synthesized at 393 K (a), 413 K (b) and 433 K (c)

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	Fig. 8 He permeance of the bare support (▼) and TAPO-5 membranes, whose seeds are synthesized at 393 K (■), 413 K (●) and 433 K (▲)

3 Conclusions

TAPO-5 seeds were synthesized at different crystallization temperature. Amorphous seed was obtained at the crystallization temperature of 393 K, while a crystallized TAPO-5 seed was synthesized at 433 K. Whatever kind of those seeds are feasible to induce the growth of the TAPO-5 membrane, as proved by the XRD characterization. The former amorphous seed, but the later crystal seed, was beneficial to obtain crack-free TAPO-5 membrane. This behavior is associated with the disparate seeds layers deposited by the spreading-wetting method, and consistently illustrated by the SEM images and single gas permeation. The amorphous seed thus is a prior choice to prepare the perfective TAPO-5 membrane via the tertiary growth.

参考文献

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[1]	YU J H, XU R R. Rich structure chemistry in the aluminophosphate family. Accounts of Chemical Research, 2003, 36(7): 481-490. [本文引用:1] [JCR: 20.833]
[2]	ZHAO X H, LI X B, CHEN J, et al. Ambient pressure synthesis of hierarchical structured SAPO-5 molecular sieve with special morphology. Journal of Inorganic Materials, 2014, 29(8): 821-826. [本文引用:1] [JCR: 0.537] [CJCR: 1.106]
[3]	SARA M, MUTHUSAMY V, MARIO C, et al. Elucidating the nature and reactivity of Ti ions incorporated in the framework of AlPO₄-5 molecular sieves. New evidence from ³¹P HYSCORE spectroscopy. Journal of the American Chemical Society, 2011, 133(19): 7340-7343. [本文引用:2] [JCR: 10.677]
[4]	LEE S O, RAJA R, HARRIS K D M, et al. Mechanistic insights into the conversion of cyclohexene to adipic acid by H₂O₂ in the presence of a TAPO-5 catalyst. Angewand te Chemie International Edition, 2013, 42(13): 1520-1523. [本文引用:1] [JCR: 13.734]
[5]	WANG X B, GUO Y, ZHANG X F, et al. Catalytic properties of benzene hydroxylation by TS-1 film reactor and Pd-TS-1 composite membrane reactor. Catalysis Today, 2010, 156(3/4): 288-294. [本文引用:1] [JCR: 2.98]
[6]	CHOI J, JEONG H-K, SNYDER M A, et al. Grain boundary defect elimination in a zeolite membrane by rapid thermal processing. Science, 2009, 325(5940): 590-593. [本文引用:2]
[7]	YANG W S, ZHANG B Q, LIU X F. Synthesis and characterization of SAPO-5 membranes on porous α-Al₂O₃ substrates. Microporous and Mesoporous Materials, 2009, 117(1/2): 391-394. [本文引用:1] [JCR: 3.365]
[8]	WANG X D, YAN J, HUANG W. Preparation and characterization of ultrafine crystal TS-1 films. Journal of Inorganic Materials, 2011, 26(1): 85-90. [本文引用:1] [JCR: 0.537] [CJCR: 1.106]
[9]	WANG J F, LIU X G, ZHANG P P, et al. Synthesis of continuous and dense TAPO-5 molecular sieve membranes by steam-assisted gel conversion method. Journal of Inorganic Materials. 2013, 28(6): 589-593. [本文引用:3]
[10]	STOEGER J A, PALOMINO M, AGRAWAL K V, et al. Oriented CoSAPO-5 membranes by microwave-enhanced growth on TiO₂- coated porous alumina. Angewand te Chemie International Edition, 2012, 51(10): 2470-2473. [本文引用:1] [JCR: 13.734]
[11]	CARREON M A, LI S, FALCONER J L, et al. Alumina-supported SAPO-34 membranes for CO₂/CH₄ separation. Journal of the American Chemical Society, 2008, 130(16): 5412-5413. [本文引用:1] [JCR: 10.677]
[12]	HUANG A, CARO J. Highly oriented, neutral and cation-free AlPO₄ LTA: from a seed crystal monolayer to a molecular sieve membrane. Chemical Communications, 2011, 47(14): 4201-4203. [本文引用:1] [JCR: 6.378]
[13]	SATO K, NAKANE T. A high reproducible fabrication method for industrial production of high flux NaA zeolite membrane. Journal of Membrane Science, 2007, 301(1/2): 151-161. [本文引用:1]
[14]	DAS J K, DAS N, BANDYOPADHYAY S. Highly oriented improved SAPO-34 membrane on low cost support for hydrogen gas separation. Journal of Materials Chemistry A, 2013, 1(16): 4966-4973. [本文引用:2]
[15]	ZHOU M, HEDLUND J. Assembly of oriented iron oxide and zeolite crystals via biopolymer films. Journal of Materials Chemistry, 2012, 22(47): 24877-24881. [本文引用:1] [JCR: 5.968]
[16]	HUANG A, LIN Y S, YANG W. Synthesis and properties of A-type zeolite membranes by secondary growth method with vacuum seeding. Journal of Membrane Science, 2004, 245(1/2): 41-51. [本文引用:1]
[17]	ALGIERI C, BERNARDO P, BARBIERI G, et al. A novel seeding procedure for preparing tubular NaY zeolite membranes. Microporous and Mesoporous Materials, 2009, 119(1/2/3): 129-136. [本文引用:1] [JCR: 3.365]
[18]	LIU X G, XU L, ZHANG B Q, et al. Template removal from AFI aluminophosphate molecular sieve by Pd/SiO₂ catalytic hydrocracking at mild temperature. Microporous and Mesoporous Materials, 2014, 193: 127-133. [本文引用:2] [JCR: 3.365]
[19]	CHEN S B, LIU X G, ZHANG B Q. Preparation and properties of porous α-Al₂O₃ based ceramic disk substrates. Journal of Inorganic Materials, 2013, 28(6): 599-604. [本文引用:1] [JCR: 0.537] [CJCR: 1.106]
[20]	KARANIKOLOS G N, WYDRA J W, STOEGER J A, et al. Continuous c-oriented AlPO₄-5 films by tertiary growth. Chemistry of Materials, 2007, 19(4): 792-797. [本文引用:2] [JCR: 8.238]
[21]	LANG L, LIU X F, ZHANG B Q. Synthesis and characterization of (h0h)-oriented silicalite-1 films on α-Al₂O₃ substrates. Appllied Surface Science, 2008, 254(8): 2353-2358. [本文引用:1]
[22]	KANEZASHI M, O'BRIEN J, LIN Y S. Template-free synthesis of MFI-type zeolite membranes: permeation characteristics and thermal stability improvement of membrane structure. Journal of Membrane Science, 2006, 286(1/2): 213-222. [本文引用:2]
[23]	HU E P, HUANG Y L W, YAN Q, et al. Synthesis of highly c-oriented AFI membranes by epitaxial growth. Microporous and Mesoporous Materials, 2009, 126(1/2): 81-86. [本文引用:2] [JCR: 3.365]
[24]	KARANIKOLOS G N, GARCIA H, CORMA A, et al. Growth of AlPO₄-5 and CoAPO-5 films from amorphous seeds. Microporous and Mesoporous Materials, 2008, 115(1/2): 11-22. [本文引用:2] [JCR: 3.365]
[25]	PENG Y, ZHAN Z Y, SHAN L J, et al. Preparation of zeolite MFI membranes on defective macroporous alumina supports by a novel wetting-rubbing seeding method: role of wetting agent. Journal of Membrane Science, 2013, 444: 60-69. [本文引用:2]

2003

20.833

0.0

Accounts of Chemical Research. 2003, 36(7):481-490

Rich structure chemistry in the aluminophosphate family.

YU J H , XU R R.

This Account describes a family of aluminophosphates ranging from neutral open-frameworks to anionic frameworks with fascinating structural architectures. In contrast to aluminosilicate zeolites, these aluminophosphates exhibit wealthy structural features, including extra-large micropores, mixed bonding, different structural dimensionalities, rich compositional diversities, and various stacking sequences of their 2-D sheets. The low-dimensional networks, acting as building units, can be assembled to 3-D open-frameworks via transition metal cations through a building-up process. New stoichiometries and hypothetical structural topologies can be predicted and enumerated. Computational and combinatorial approaches will greatly help to access the range of the diverse structures.

... Aluminophosphate molecular sieves (AlPO-n), where n denotes a particular structure type, have been recognized as a novel ordered microporous materials^[1] ...

2014

0.537

1.106

Journal of Inorganic Materials. 2014, 29(8):821-826

Ambient pressure synthesis of hierarchical structured SAPO-5 molecular sieve with special morphology.

ZHAO X H , LI X B , CHEN J

Hierarchical structured SAPO-5 molecular sieve was ionothermally synthesized by microwave irradiation using a mixture solution of succinic acid, choline chloride and tetraethyl ammonium bromide as solvent and template under ambient pressure. The effects of the molar ratios of P 2 O 5 /Al 2 O 3 and HF/Al 2 O 3 , silicon source, and crystallization time on the structure of SAPO-5 molecular sieve were systematically investigated. The resulting SAPO-5 molecular sieve was characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), Transmission electron microscope (TEM), N 2 physical adsorption-desorption and 29 Si magic-angle spinning nuclear magnetic resonance ( 29 Si MAS-NMR) techniques, respectively. The results indicate that intra-crystalline and inter-crystalline mesopores coexist within the SAPO-5 molecular crystals, while 29 Si MAS-NMR test shows that the incorporation of Si in the sample follows the SM3 mechanism. In addition, SEM images exhibit that hierarchical structured SAPO-5 molecular sieve with hexagonal nanometer-disc morphology can be synthesized under specific synthetic conditions.

... Their AlPO₄ frameworks are rich of structural chemistry and special physiochemical properties of isomorphous substitution by heteroatoms^[2], like metal-aluminophosphate MAPO-n (M = Ti, Fe, etc)^[3] ...

2011

10.677

0.0

Journal of the American Chemical Society. 2011, 133(19):7340-7343

Elucidating the nature and reactivity of Ti ions incorporated in the framework of AlPO₄-5 molecular sieves. New evidence from ³¹P HYSCORE spectroscopy.

SARA M , MUTHUSAMY V , MARIO C

The incorporation of Ti ions within the framework of aluminophosphate zeotype AlPO-5 and their chemical reactivity is studied by means of CW-EPR, HYSCORE, and UV–vis spectroscopies. Upon reduction, Ti 3+ ions are formed, which exhibit large 31 P hyperfine couplings, providing direct evidence for framework substitution of reducible Ti ions at Al sites.

... Similar strong absorbtion bands between 200- 300 nm, ascribed to charger transfer of the framework Ti^[3,9], suggest negligible diverse in micro structure associated with Ti ...

2013

13.734

0.0

... Typically, Ti incorporated AFI type aluminophosphate molecular sieve (TAPO-5, T = Ti) exhibits catalytic activities of selective oxidation, owning to its framework Ti as redox active centers^[4] ...

2010

2.98

0.0

Catalysis Today. 2010, 156(3/4):288-294

Catalytic properties of benzene hydroxylation by TS-1 film reactor and Pd-TS-1 composite membrane reactor.

WANG X B , GUO Y , ZHANG X F

Titanium silicalite-1 (TS-1) and mesoporous TS-1p were incorporated as catalyst for the direct hydroxylation of benzene to phenol in a palladium membrane reactor. The zeolite also served as intermediate support layer and diffusion barrier against contaminants. Pd–TS-1 and Pd–TS-1p were characterized and tested for hydrogen permeation before investigating their performance for the benzene direct hydroxylation reaction. The effects of reactor configuration, reaction conditions and catalysts on conversion, product yield and water production were examined. The phenol yield of Pd–TS-1p was the highest followed by Pd–Sil-1 and Pd–TS-1 with Pd–TS-1p and Pd–TS-1 having phenol selectivity higher than 95%. The optimum reactor configuration and H 2 /O 2 molar feed ratio were identified.

... TAPO-5, as well as TS-1 membrane^[5], is of particular interests for possible applications as a catalytic or separation membrane ...

2009

0.0

Science. 2009, 325(5940):590-593

Grain boundary defect elimination in a zeolite membrane by rapid thermal processing.

CHOI J , JEONG H-K , SNYDER M A

Microporous molecular sieve catalysts and adsorbents discriminate molecules on the basis of size and shape. Interest in molecular sieve films stems from their potential for energy-efficient membrane separations. However, grain boundary defects, formed in response to stresses induced by heat treatment, compromise their selectivity by creating nonselective transport pathways for permeating molecules. We show that rapid thermal processing can improve the separation performance of thick columnar films of a certain zeolite (silicalite-1) by eliminating grain boundary defects, possibly by strengthening grain bonding at the grain boundaries. This methodology enables the preparation of silicalite-1 membranes with high separation performance for aromatic and linear versus branched hydrocarbon isomers and holds promise for realizing high-throughput and scalable production of these zeolite membranes with improved energy efficiency.

... , no pinhole and cracks^[6] ...

... These cracks, destructing the perfection of the membranes, were formed in response to thermal tensile stresses^[6] ...

2009

3.365

0.0

Microporous and Mesoporous Materials. 2009, 117(1/2):391-394

Synthesis and characterization of SAPO-5 membranes on porous #cod#x003b1;-Al₂O₃ substrates.

YANG W S , ZHANG B Q , LIU X F.

The continuous and highly intergrown SAPO-5 membrane on the α-Al 2 O 3 substrate was synthesized by using in situ crystallization and microwave heating. According to the characterization using scanning electron microscopy (SEM) and X-ray diffraction (XRD), the 5 μm-thick membrane was composed of well-intergrown pure SAPO-5 crystals, which were tightly covered on the α-Al 2 O 3 substrate in random orientation. The single-component pervaporation measurements revealed the resulting membrane was of high-quality with few non-zeolitic pores.

... Available methods for preparing zeolite membranes include in-situ growth^[7], seeded growth^[8], and dry gel synthesis^[9] ...

2011

0.537

1.106

Journal of Inorganic Materials. 2011, 26(1):85-90

Preparation and characterization of ultrafine crystal TS-1 films.

WANG X D , YAN J , HUANG W.

The compact, uniform and continuous seed layers were prepared on porous α-Al 2 O 3 substrates with oval-shaped and ultrafine seed crystals by ultrasonic seeding, and then TS-1 films were formed after secondary growth. The microstructure of the films could be regulated by changing the ratios of OH-/Si and the crystallization time. SEM and XRD results reveal that when the ratio of OH-/Si is equal to 0.09, after 24h of crystallization time, the film is not interconnected. If the crystallization time is prolonged to 48h, the film have become dense and interconnected, the crystals in which are about 500nm, and when the reaction time is prolonged to 72h, the crystallinity of the film decreases, and the surface of the film is covered with a layer of amorphous materials. When the ratio of OH-/Si is increased to 0.21, after 24h of crystallization time, the crystal grains in the top layer are about 400nm and the structure of the TS-1 film is asymmetric, with a dense and uniform TS-1 layer on top, the support at the bottom, and the seed layer in between.

... Available methods for preparing zeolite membranes include in-situ growth^[7], seeded growth^[8], and dry gel synthesis^[9] ...

2013

0.0

Journal of Inorganic Materials.. 2013, 28(6):589-593

Synthesis of continuous and dense TAPO-5 molecular sieve membranes by steam-assisted gel conversion method.

WANG J F , LIU X G , ZHANG P P

TAPO-5 molecular sieve membranes were synthesized by using steam-assisted gel conversion method. The as-synthesized TAPO-5 membranes were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), as well as UV-visible diffuse reflectance spectroscope (UV-Vis). Results were compared with those by conventional hydrothermal crystallization method. The influences of the aging conditions and crystallization time on the surface morphology, coverage and denseness of the membrane together with the crystalline structure of molecular sieve crystals were investigated. By using steam-assisted gel conversion method, continuous and dense TAPO-5 molecular sieve membranes could be fabricated on porous-Al2O3 substrates after crystallization for 48 h because the pre-aged solid gel were favorable to the incorporation of Ti atoms into the tetrahedral framework and the intergrowth of TAPO-5 crystals.

... Available methods for preparing zeolite membranes include in-situ growth^[7], seeded growth^[8], and dry gel synthesis^[9] ...

... The TAPO-5 membrane, however, may not in-situ growth on the bare support^[9] ...

... Similar strong absorbtion bands between 200- 300 nm, ascribed to charger transfer of the framework Ti^[3,9], suggest negligible diverse in micro structure associated with Ti ...

2012

13.734

0.0

Angewandte Chemie International Edition. 2012, 51(10):2470-2473

Oriented CoSAPO-5 membranes by microwave-enhanced growth on TiO₂- coated porous alumina.

STOEGER J A , PALOMINO M , AGRAWAL K V

Microwaving plates : A facile method was developed for the fabrication of preferentially c -oriented cobalt-substituted silicoaluminophosphate-5 (CoSAPO-5) membranes on porous alumina supports. In situ microwave growth using a slip-coated TiO 2 layer on the support surface resulted in an oriented CoSAPO-5 crystal layer, which was evolved into a defect-free membrane by improving crystalline intergrowth through secondary hydrothermal microwave growth.

... , AFI^[10], CHA^[11], and LTA^[12],because of its preferable reproducibility^[13] ...

2008

10.677

0.0

Journal of the American Chemical Society. 2008, 130(16):5412-5413

Alumina-supported SAPO-34 membranes for CO₂/CH₄ separation.

CARREON M A , LI S , FALCONER J L

SAPO-34 membranes were prepared by in situ crystallization on α-Al 2 O 3 porous supports. The crystal size of the seeds was effectively controlled in the 0.7 to 8.5 µm range by employing different structure-directing agents. Seeds smaller than 1 µm produced membranes with CO 2 /CH 4 separation selectivities higher than 170 and unprecedented CO 2 permeances as high as ∼2.0 × 10 −6 mol/m 2 ·s·Pa at 295 K and a feed pressure of 224 kPa. The membranes effectively separated CO 2 /CH 4 mixtures up to 1.7 MPa.

... , AFI^[10], CHA^[11], and LTA^[12],because of its preferable reproducibility^[13] ...

2011

6.378

0.0

Chemical Communications. 2011, 47(14):4201-4203

Highly oriented, neutral and cation-free AlPO₄ LTA: from a seed crystal monolayer to a molecular sieve membrane.

HUANG A , CARO J.

An oriented, neutral and cation-free AlPO 4 LTA molecular sieve membrane with high hydrogen selectivity was prepared on porous α-Al 2 O 3 supports through secondary growth of a highly oriented AlPO 4 LTA monolayer.

... , AFI^[10], CHA^[11], and LTA^[12],because of its preferable reproducibility^[13] ...

2007

0.0

Journal of Membrane Science. 2007, 301(1/2):151-161

A high reproducible fabrication method for industrial production of high flux NaA zeolite membrane.

SATO K , NAKANE T.

A high reproducible fabrication method for high-flux NaA zeolite membrane has been developed for industrial mass production. The synthesized NaA membranes exhibited higher water flux (5.6 kg m −2 h −1 ) by pervaporation (PV) experiments in a mixture of water (10 wt.%)/ethanol (90 wt.%) at 348 K compared with those of previous reported for the comparable water/alcohol separation factors, α (10 3 –10 4 ). Vapor permeation (VP) experiments on saturated vapor with the above mixture up to 418 K and 930 kPa showed so high performance of flux of 31 kg m −2 h −1 with α > 10 4 that can be applied practically to such a hybrid system of distillation-vapor permeation. High reproducibility in the developed fabrication method for membranes was confirmed by permeation tests. Pore size distribution estimated by permporosimetry showed that an average pore size was 0.7 nm in Kelvin diameter and half of the gas flow permeate through nonzeolitic pores. The thickness of effective layer in the membrane was determined by a focused ion beam (FIB) preparation method to be ca. 4 μm that was thinner than those of previous studies. It could be suggested that the higher flux is attributed mainly to lower transporting resistance by the thin layer and existence of nonzeolitic pores in the membranes.

... , AFI^[10], CHA^[11], and LTA^[12],because of its preferable reproducibility^[13] ...

2013

0.0

Journal of Materials Chemistry A. 2013, 1(16):4966-4973

Highly oriented improved SAPO-34 membrane on low cost support for hydrogen gas separation.

DAS J K , DAS N , BANDYOPADHYAY S.

In this paper we investigated a path towards preparation of a highly oriented improved SAPO 34 zeolite membrane on a silica modified low cost clay-Al 2 O 3 support by selective deposition of oriented seed crystals, followed by an epitaxial secondary growth hydrothermal technique. The membrane thickness was found to be 26 μm. The silica layer that have an abundance of reactive hydroxyl groups while its interior is connected by the siloxane group Si–O–Si. These Si–OH groups on the silica-coated substrate could provide a hydrogen bonding interaction with surface hydroxyl groups of SAPO 34 seed crystals. This outcome is a possible result of the formation of a uniform seed monolayer with the same orientation. The stronger intensity of the single peak in XRD pattern confirms the formation of an oriented membrane layer. For comparison, a seed layer was deposited on an unmodified support surface. A discrete and randomly oriented membrane layer was obtained on that support. Highly oriented SAPO 34 membranes on the silica modified support are better for hydrogen gas separation and attained higher selectivity values for the gas mixture. A selectivity of 16.66 and 20.91 was achieved for H 2 –CO 2 and H 2 –N 2 , respectively, at room temperature. The obtained values were improved compared to the reported literature values. Herein, we report for the first time, that this work is an improvement towards a highly crystallographic orientation of the SAPO 34 membrane layer with reduced defects and higher gas separation efficiency. The synthesized membrane enhanced the reproducibility and long term durability for hydrogen gas separation with good results.

... The quality of the membranes prepared by the seeded growth method is considerably affected by the seeding methods, including dip-coating^[14], rubbing^[15], vacuum seeding^[16], and filtration seeding^[17] ...

... 3 Preparation of TAPO-5 seed layersThe spreading-wetting method, basing on a dip-coating route^[14], was typically performed as following ...

2012

5.968

0.0

Journal of Materials Chemistry. 2012, 22(47):24877-24881

Assembly of oriented iron oxide and zeolite crystals via biopolymer films.

ZHOU M , HEDLUND J.

Biopolymers are developed as functional intermediate linkers for the assembly of nano and submicron-sized crystals. Mediated by the interlayers, iron oxide and zeolite crystals with varied shapes (cubic, ellipsoidal, and discoidal) are organized into uniformly oriented monolayers on glass plates and macroporous alumina supports. The crystal monolayers can be near-perfect transferred onto the substrate upon calcination, which are suitable for further growth. The assembled crystals display a range of colors, and important mechanisms with direct evidence for explaining this optical appearance are proposed.

2004

0.0

Journal of Membrane Science. 2004, 245(1/2):41-51

Synthesis and properties of A-type zeolite membranes by secondary growth method with vacuum seeding.

HUANG A , LIN Y S , YANG W.

A-type zeolite membranes were successfully synthesized on tubular α-Al 2 O 3 supports by secondary growth method with vacuum seeding. In the seeding process, a thin, uniform and continuous seeding layer was closely attached to the support surface by the pressure difference between the two sides of the support wall. The effects of seed particle size, suspension concentration, coating pressure difference and coating time on the membrane and its pervaporation properties were investigated. The as-synthesized membranes were characterized by XRD and SEM. The quality of the membranes was evaluated by the pervaporation dehydration of 95 wt.% isopropanol/water mixture at 343 K. High quality A-type zeolite membranes can be reproducibly prepared by the secondary growth method with vacuum seeding under the conditions: seed particle size of 500–1200 nm, suspension concentration of 4–8 g/l, coating pressure difference of 0.0100–0.0250 MPa and coating time of 45–180 s.

2009

3.365

0.0

Microporous and Mesoporous Materials. 2009, 119(1/2/3):129-136

A novel seeding procedure for preparing tubular NaY zeolite membranes.

ALGIERI C , BERNARDO P , BARBIERI G

A good seeding is a mandatory step to have defect-free zeolitic membranes prepared by means of a secondary growth method. The transport properties of the zeolitic membranes depend strongly on the seeding procedure of zeolite crystals during which the whole support surface has to be covered uniformly and sufficiently. A new seeding procedure, involving cross-flow filtration of a water suspension combined with rotation and tilting of the membrane support, was developed and utilized for the first time. Porous α-alumina tubes were seeded using a water suspension of 0.2 wt.% in zeolite crystals, at a pH of ca. 9.2 and room temperature. Cumulative stage-cut of the seeding phase was used as design parameter in order to tailor the permeation properties (e.g., permeance) of the resulting NaY zeolite membranes. The secondary growth was accomplished by a hydrothermal treatment. SEM, EDX and XRD analyses show dense intergrown FAU layers with Si/Al ratios of 1.8–2.0 typical of the NaY zeolite. The measured permeance was 5–10% of that showed by the bare support. Another evidence of the membrane quality can be found considering their application in CO selective oxidation reaction [P. Bernardo, C. Algieri, G. Barbieri, E. Drioli, Catal. Today 118(1–2) (2006) 90]: a complete conversion of carbon monoxide which falls down 1000 times from 10,000 to ca. 10 ppm indicates very few defects in the zeolite layer.

2014

3.365

0.0

Microporous and Mesoporous Materials. 2014, 193:127-133

Template removal from AFI aluminophosphate molecular sieve by Pd/SiO₂ catalytic hydrocracking at mild temperature.

LIU X G , XU L , ZHANG B Q

Pd/SiO 2 catalytic hydro-cracking is applied to remove triethylamine template in an AFI type MnMgAlPO-5 molecular sieve. The triethylamine template reacts with spillover hydrogen inletting from the Pd/SiO 2 catalyst, and is hydro-cracked to small molecules at a mild temperature (613 K). This behavior is distinguish to the conventional template removal method of calcination above 823 K, and consistently proved by H 2 -TPR/MS, TG/MS, and N 2 -isotherms results. The catalytic hydro-cracking method does not damage the crystal structure of MnMgAlPO-5, indicated by XRD characterization. Its novelty is suggested as reserving the local symmetric structure of MnMgAlPO-5 ( i.e. , keeping framework Mn and Mg), consistently verified by EPR, UV–vis, and Raman spectra. This provides an alternative option for the template removal from molecular sieves.

... The as-synthesized TAPO- 5 membrane is activated by a mild method of catalytic hydrocracking^[18] ...

... Activating those membranes was achieved by a Pd/SiO₂ catalytic hydrocracking method performed as following^[18] ...

2013

0.537

1.106

Journal of Inorganic Materials. 2013, 28(6):599-604

Preparation and properties of porous #cod#x003b1;-Al₂O₃ based ceramic disk substrates.

CHEN S B , LIU X G , ZHANG B Q.

Porous α-Al2O3 based ceramics disks were prepared by dry pressure molding method. Influences of sintering temperature and SiO2 dopant on the structure, morphology and properties were investigated. It was founded that compressive strength and shrinkage ratio of α-Al2O3 ceramic disk both increased with increasing sintering temperature. The shrinkage ratio and compressive strength was less than 0.5% and stronger than 80 MPa, respectively, while the optimum sintering temperature was chosen to be 1180℃. The sintering of α-Al2O3 ceramic disk would be enhanced by doping SiO2, which crystallized into cristobalite phase from an amorphous phase during the sintering process. α-Al2O3 ceramic disk doped with 12wt% SiO2 sintered at 1180℃ exhibited a stronger compressive strength (110 MPa) and a shrinkage ratio of 1.2%. The ceramic disk possessed a smaller pore size but a wider pore size distribution than that of the pure α-Al2O3 ceramic disk. It was demonstrated that both α-Al2O3 and SiO2 doped α-Al2O3 ceramic disk substrates were favorable for the growth of ZSM-5 zeolite membranes. However, these ZSM-5 zeolite membranes showed different morphologies and crystal sizes, due to the difference in physicochemical properties of substrates.

... = 20 mm^[19]) was employed as supports for the TAPO-5 membrane ...

2007

8.238

0.0

Chemistry of Materials. 2007, 19(4):792-797

Continuous c-oriented AlPO₄-5 films by tertiary growth.

KARANIKOLOS G N , WYDRA J W , STOEGER J A

c -Oriented AlPO 4 -5 films were synthesized by seeded growth on silicon substrates. Secondary hydrothermal treatment of the seeded substrates under conditions that favor c -out-of-plane growth yielded non-intergrown, highly oriented columnar crystals with a length of 7 μm. Modifying the conditions so that in-plane growth is favored and executing yet another (“tertiary”) growth, the crystals obtained by secondary treatment were grown in-plane, along the a -, b -directions, filling the gaps between the columnar grains and yielding well-intergrown, highly oriented, continuous AlPO 4 -5 films. The oriented films obtained by the technique presented here can be potentially useful for separations and catalysis as well as electronic and electrochemical applications.

... They were utilized to a tertiary growth with the fresh precursor sol^[20] ...

... This phenomenon is obviously diverse to epitaxial growth of oriented AFI membrane on seeded smooth supports^[20,23] ...

2008

0.0

Appllied Surface Science. 2008, 254(8):2353-2358

Synthesis and characterization of (h0h)-oriented silicalite-1 films on #cod#x003b1;-Al₂O₃ substrates.

LANG L , LIU X F , ZHANG B Q.

A simple and well-designed synthesis procedure is proposed to fabricate silicalite-1 films on porous α-Al 2 O 3 substrates on purpose of preventing the aluminum leaching. The continuous and 2 μm thick seed layer of silicalite-1 crystals is fabricated by using a spin coater. The first-time seeded growth is performed to synthesize a thin layer of intergrown ZSM-5 crystals on the silicalite-1 seed layer, where the use of low alkalinity and short synthesis time is to reduce the aluminum leaching. The intergrown layer of ZSM-5 crystals serves as a barrier to block the aluminum leaching from porous α-Al 2 O 3 substrates in the second-time seeded growth, leading to the formation of ca. 11 μm thick intergrown and oriented silicalite-1 films with an extremely high Si/Al ratio. According to SEM images and XRD measurements, the as-synthesized silicalite-1 film is dense, continuous, and (1 0 1)-oriented. The electron probe microanalysis (EPMA) of the resulting film demonstrates that there is no aluminum leaching in the second-time seeded growth. The leaking tests confirm that non-zeolitic pores in the silicalite-1 film are negligible.

2006

0.0

... are attributed to Knudsen and viscous flow, respectively^[22]) ...

... These seeds, with different crystallinity, obviously brings about distinguish hetero epitaxial growth behaviors of the TAPO-5 membrane on the support, and thus the diverse perfection proved by single gas permeation associated^[22] ...

2009

3.365

0.0

Microporous and Mesoporous Materials. 2009, 126(1/2):81-86

HUANG Y L W, YAN Q, et al. Synthesis of highly c-oriented AFI membranes by epitaxial growth.

HU E P

The growth behavior between the two isomorphs of AFI type zeolite molecular sieves, AlPO-5 and SAPO-5 was studied. It was found that epitaxial growth of AlPO-5 from SAPO-5 seed layers led to preferential growth along the in-plane directions. Based on this interest finding, compact and highly c -oriented AFI membranes were successfully synthesized through a modified seeded growth procedure. The membrane quality was inspected by DC polarization test.

... 3) of an available plate-like SAPO-5 seed^[23] ...

... This phenomenon is obviously diverse to epitaxial growth of oriented AFI membrane on seeded smooth supports^[20,23] ...

2008

3.365

0.0

Microporous and Mesoporous Materials. 2008, 115(1/2):11-22

Growth of AlPO₄-5 and CoAPO-5 films from amorphous seeds.

KARANIKOLOS G N , GARCIA H , CORMA A

The growth of aluminophosphate AlPO 4 -5 (AFI structure with one-dimensional parallel and straight channels of 7.3 Å in cross section) and cobalt-substituted AlPO 4 -5 (CoAPO-5) films by hydrothermal treatment is investigated. In situ growth on bare (unmodified) silicon substrates using different growth temperatures, times, and precursor mixture compositions was carried out first and yielded films that exhibited either preferred orientation and poor coverage or good coverage but random orientation. Introducing seeded growth, which involved functionalization and seeding of the substrate with the amorphous fraction of an AlPO 4 -5-containing powder followed by hydrothermal seed growth, c -oriented, well-intergrown films were obtained with a variety of morphologies depending on the synthesis mixture composition and growth conditions. The effect of two different structure directing agents (SDAs), namely triethylamine and tripropylamine, was also examined. Controlled experiments by systematically varying secondary growth duration were performed in order to find the optimal growth time that yields complete coverage while minimizing the degree of misorientation. Seeded growth using dilute precursor mixtures favors c -out-of-plane growth yielding films with a thickness of several micrometers, while reducing the water/Al 2 O 3 molar ratio and executing secondary growth under the appropriate hydrothermal conditions favored in-plane growth yielding well-intergrown films with sub-micron thickness. SEM, XRD, and UV–vis spectroscopy were used to characterize the synthesized AlPO 4 -5 and CoAPO-5 films.

... It is well known that amorphous or nano-sized zeolites exhibit high activity for inducing its membrane growth^[24] ...

... This may be associated with its high activity for inducing the inter-grown of TAPO-5 crystal and forming the polycrystalline structure^[24] ...

2013

0.0

Journal of Membrane Science. 2013, 444:60-69

Preparation of zeolite MFI membranes on defective macroporous alumina supports by a novel wetting-rubbing seeding method: role of wetting agent.

PENG Y , ZHAN Z Y , SHAN L J

High quality zeolite MFI membranes are successfully synthesized on inexpensive defective macroporous alumina tubes by the seeded growth method. A novel seeding method of wetting assisted rubbing (wetting–rubbing, WR) technique is developed and with this new WR method alumina supports are first wetted with a liquid agent followed by rubbing dry MFI seed crystals. Effects of two typical wetting agents, i.e., alcohol solvents ( n -butanol) and water on the seed layer formation and membrane performance are investigated. Experimental data suggest that n -butanol is much more effective than water for preparation of a uniform and continuous MFI seed layer on the defective alumina support, which is attributed to the hydrophobic nature of MFI crystals and their better dispersion in alcohols. The zeolite membranes synthesized at 175 °C for 4 h on the well-seeded supports have a separation layer thickness of ∼3.5 μm, and exhibit a high pervaporation performance with the ethanol/water separation factor of 62 and permeation flux of 1.82 kg m −2 h −1 for the 5:95 (wt%) ethanol/water mixture separation at 60 °C. The WR seeding method may lead to reproducible preparation of zeolite membranes on defective low-cost supports.

... Those distinguish seeds distributions may cause different growth behaviors and the quality of zeolite membrane^[25] ...

... Another possible promotional effect is the dispersive distribution of the amorphous seeds in the holes of supports^[25] ...

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