Ionothermal Synthesis of Oriented Zeolite AEL Films and Their Application as Corrosion‐Resistant Coatings

Cai, Rui; Sun, Minwei; Chen, Zhongwei; Munoz, Ronnie; O’Neill, Cory; Beving, Derek E.; Yan, Yushan

doi:10.1002/anie.200704003

Cited by 140 publications

(89 citation statements)

References 53 publications

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“…Our previous attempts to prepare molecular sieve membranes by in situ ionothermal synthesis [21] with Al[OCH-(CH 3 ) 2 ] 3 as added Al source were not successful (Supporting Information, Table S1). Crystallization occurred only in the solution phase, and a continuous membrane could not be formed on porous substrates.…”

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confidence: 99%

“…In ionothermal synthesis, the dual action of fluoride ions as SDA and mineralizer increases the efficiency of crystallization. [13a] According to the two-stage model of Yan et al for the ionothermal synthesis of oriented SAPO-11 film, [21] the space between growth centers may be limited by the abundant seeds formed in the first stage, which suppress in-plane growth of the crystal in the second stage. In our case, increasing addition of HF promotes nucleation of molecular sieve crystals at the interface.…”

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Ionothermal Synthesis of Aluminophosphate Molecular Sieve Membranes through Substrate Surface Conversion

Tian

et al. 2012

Angew Chem Int Ed

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Applications of zeolite membranes in separation, chemical sensors, and catalytic membrane reactors have led to extensive studies on their fabrication. [1,2] To date, mainly silicatebased zeolite membranes of the structure types MFI, [3] DDR, [4] LTA, [5] and FAU [6] have been synthesized on different substrates and evaluated for single-or multiple-gas permeation. Routes for the synthesis of zeolite membranes can be broadly classified into two categories: [7] in situ and secondary growth synthesis, both of which are derived from the strategy of hydrothermal zeolite synthesis. However, the high autogenous pressure [8] associated with hydrothermal procedures is inconvenient for preparation of zeolite membranes, especially for large-scale production, due to safety concerns and the risk of molecular sieve collapse. On the other hand, although aluminophosphate [9,10] and silicoaluminophosphate [11,12] membranes for gas separation have been prepared, there are few reports on the preparation of aluminophosphate molecular sieve membranes, [9][10][11][12] which suggests that hydrothermal preparation of such membranes may be difficult.Ionothermal synthesis, [13] which uses ionic liquids as reaction media instead of water or organic solvents, allowed highly efficient preparation of aluminophosphate molecular sieves under ambient pressure. [13][14][15] Ionic liquids (ILs) are commonly defined as salts that consist of organic cations and inorganic anions with melting temperatures below 100 8C. [16] ILs are well known as environmentally benign and designable solvents, [17] which endow ionothermal synthesis with interesting features and many potential advantages over the hydrothermal method. As a result of the negligible vapor pressure of ILs, ionothermal synthesis can take place at ambient pressure, which eliminates safety concerns. The organic cation of the IL can act as a structure-directing agent (SDA), [13c] or play a cooperative structure-directing role together with introduced amines and quaternary ammonium compounds. [18][19][20] AEL, AFI, CHA, LTA, and ÀCLO types of aluminophosphate molecular sieves have been successfully synthesized by ionothermal methods.Ionothermal synthesis is a promising method for the preparation of aluminophosphate molecular sieve membranes under ambient pressure. Yan and co-workers prepared AlPO-11 and SAPO-11 films on aluminum alloys as anticorrosion coatings by in situ ionothermal synthesis. [21] To the best of our knowledge, no permeable membrane has been previously prepared on a porous substrate by the ionothermal method. Here we report an ionothermal method for the synthesis of permeable aluminophosphate molecular sieve membranes on porous alumina disks by substrate-surface conversion.Molecular sieve membranes of types AEL, AFI, CHA, and LTA were prepared by placing homemade d-alumina substrates (2.0 mm thickness, 20 mm diameter, and 10 nm average pore size; see Supporting Information for details) in a solution of IL, phosphoric acid, hydrofluoric acid, and, if required, organic amines w...

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Ionothermal Synthesis of Aluminophosphate Molecular Sieve Membranes through Substrate Surface Conversion

Tian

et al. 2012

Angew Chem Int Ed

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“…Taking Mordenite Framework Inverted (MFI) zeolite [1] (symmetry: orthorhombic; space group: P nma ; unit cell constants: a = 20.1 Ǻ , b = 19.9 Ǻ , and c = 13.4 Ǻ ) as an example, the pore system consists of straight channels (pore size: 0.53 9 0.56 nm) interconnected by zigzag channels (0.51 9 0.55 nm) [2]. In addition to their traditional uses as catalysts, adsorbents and ionic exchangers [3], zeolites can also be fabricated into thin films and used as separation membranes [4][5][6][7][8], selective sensors [9,10], low-k materials [11,12], corrosion-resistant coatings [13], and optical materials [14,15]. In the synthesis of high-quality zeolite films, the accurate manipulation and optimization of their microstructures, such as crystallographic preferred orientation (CPO), thickness, intergrowth and grain boundary structures, is critical.…”

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Effective manipulation of the microstructure of zeolite film by hydrothermal pretreatment

Liu

Yang

2011

J Mater Sci

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Zeolite films with diverse microstructures were prepared from highly regular seed monolayers by accurate manipulation of various synthetic parameters during secondary growth. The effects of the hydrothermal pretreatment procedure, hydrothermal pretreatment temperature and duration, secondary growth temperature and duration of prepared zeolite films on final microstructures were investigated in detail. Based on these results, a mechanism was proposed to elucidate the effects of hydrothermal pretreatment on the secondary growth dynamics of the zeolite films: hydrothermal pretreatment could induce the separation of secondary nucleation and the subsequent growth process. Consequently, the disordered growth of zeolite films could be effectively avoided.

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“…在本研究中, 溶液中氢氟酸浓度较低时, 分子筛晶体在氧化铝基底成核较少, AEL 分子筛的生长不受限制, 束状聚集体在表面随机形成, 因此此时得到的分子筛膜没有取向; 提高溶液中氢氟酸浓度, 氧化铝基底表面生成的晶核数量大大增加, 表面晶核密度增加因而晶核之间的距离大大减少, 产生空间位阻作用, 分子筛晶体在平行于基底表面方向的生长受到抑制, 而基底垂直方向上分子筛晶体生长则不受影响, 所以此时得到的 AEL 分子筛膜具备很好的 c 轴取向性 [13] . Table 2 Synthesis conditions for synthesis of AEL type molecular sieve membranes by ionothermal two-step method…”

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Ionothermal Synthesis of AEL-Type Aluminophosphate Molecular Sieve Membrane and Its Formation Mechanism

Li¹,

Li²,

Wang³

et al. 2013

Acta Chim. Sinica

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Highly c-oriented AEL aluminophosphate molecular sieve membranes were ionothermally synthesized on the surface of δ-alumina substrate by "Substrate Surface Conversion" method. The typical synthesis procedure can be described as follows: a δ-aluminia alumina disc was put into 1-ethyl-3-methyl imidazolium bromide ([EMIm]Br) solution containing reagent quantities of phosphoric acid (H 3 PO 4 ) (85 wt% in water, AR) and hydrofluoric acid (HF) (40 wt% in water, AR). The synthesis was performed at 210 ℃ for certain time. No additional Al source is added into the synthesis solution. After the synthesis, the as-synthesized sample was washed thoroughly with distilled water and acetone for several times by ultrasonic vibration and dried at 120 ℃ overnight. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were carried out to characterize the products. The synthesis process of AEL membrane via "Substrate Surface Conversion" can be divided into two separated steps, which is carried out in the ionic liquid solution of HF and H 3 PO 4 in turn. We termed this route as ionothermal two-step method, which making it possible for us to investigate the effect of HF and H 3 PO 4 , respectively. The formation mechanism of "Substrate Surface Conversion" was therefore demonstrated, with which the δ-alumina substrate acts as both support and Al source during the synthesis process. The surface of the substrate is first converted into a gel layer by the solution. The layer is a heterogeneous phase, which contains all nutrients required for the crystallization of molecular sieve membrane, including the aluminophosphate precursor, the mineralizer and the structure directing agent. The transformation from the gel layer into membrane is probably of solid-solid formation mechanism. The whole synthesis process needs the participation of both H 3 PO 4 and HF. H 3 PO 4 is an essential component of both aluminophosphate precursor and molecular sieve crystal. The crystallinity and the orientation of synthesized membranes can be greatly influenced by adjusting the amount of HF in the initial solution, which may act as both structure directing agent and mineralizer during the synthesis process of molecular sieve membrane.

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Ionothermal Synthesis of Oriented Zeolite AEL Films and Their Application as Corrosion‐Resistant Coatings

Cited by 140 publications

References 53 publications

Ionothermal Synthesis of Aluminophosphate Molecular Sieve Membranes through Substrate Surface Conversion

Ionothermal Synthesis of Aluminophosphate Molecular Sieve Membranes through Substrate Surface Conversion

Effective manipulation of the microstructure of zeolite film by hydrothermal pretreatment

Ionothermal Synthesis of AEL-Type Aluminophosphate Molecular Sieve Membrane and Its Formation Mechanism

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