Oriented Growth of ETS-4 Films Using the Method of Secondary Growth

Abstract

Oriented growth of polycrystalline ETS-4 films on porous titania substrates was investigated using the method of secondary growth, utilizing synthesis mixtures with compositions of 3.6SiO 2 /1TiO 2 /5.5Na 2 O/ xH 2 SO 4 /230.2H 2 O, where x ) 4.4 or x ) 3.6. Dense seed layers, obtained in situ by hydrothermal synthesis (x ) 4.4), were partially (a, c)-out-of-plane oriented. Films were prepared in just one secondary growth step. Films developed by evolutionary, epitaxial growth of seed crystals and were highly (x ) 4.4) b-outof-plane oriented. Highly b-out-of-plane oriented ETS-4 films were also grown from dense, partially b-out-of-plane oriented seed layers on porous R-alumina substrates using identical synthesis mixtures. [Shattuck et al., Microporous Mesoporous Mater. 2006, 88, 56]. These findings suggest that the film orientation is dictated by the secondary growth conditions and is not determined by the seed layer orientation. This was attributed to the highly anisotropic growth rates of ETS-4 and the limited growth space provided by dense seed layers. Overall, these results indicate that by effectively decoupling nucleation from seed crystal growth, and by providing conditions for the fastest growth of crystals along the b-direction in a confined space, it is possible to fabricate highly b-out-of-plane oriented ETS-4 films for advanced applications.

Hierarchical Nanomanufacturing: From Shaped Zeolite Nanoparticles to High‐Performance Separation Membranes

“…[86] In addition, aluminophosphate membranes [79,84,87,88] as well as mixed tetrahedral-octahedral oxide membranes (ETS-4 and ETS-10) have also been synthesized. [63,[89][90][91][92] Sol-gel films templated with tetrapropylammonium (TPA) salts exist as alternatives to zeolitic membranes. Despite yielding good selectivity for the separation of oand p-xylene, and enjoying simple one-step synthesis, [93] the relatively low flux through these films-attributed to the nonuniformity of the pores in the amorphous materialsserves as a potentially significant drawback.…”

Separation of propylene/propane mixtures by titanosilicate ETS-10 membranes prepared in one-step seeded hydrothermal synthesis

“…ETS-4 membranes have been prepared [2][3][4][5] and used for dehydration of water/ethanol mixtures by pervaporation [2] and gas separation of nitrogen from its mixture with oxygen, argon, methane and carbon dioxide [3]. Microporous titanosilicates and stannosilicates both with structures similar to mineral umbite have been prepared as continuous layers and were able to separate H 2 from N 2 , CO 2 , and propane with high selectivity [6].…”

Titanosilicate AM-3 membrane: A new potential candidate for H2 separation

“…A typical precursor for AM-3 membrane synthesis was prepared as follows. 16.25 g of sodium silicate solution were diluted in 7.80 g of distilled water. Then, 3.69 g of sodium hydroxide (Merck), 1.20 g of sodium chloride (Panreac) and 1.41 g of potassium chloride (Merck) were added.…”

“…Their structures consist of interlinked octahedra (sometimes pentahedra) and tetrahedra, forming frameworks with channels of molecular dimensions [8]. The few studies available on microporous titanosilicate membranes encompass ETS-10 [9][10][11][12], ETS-4 [12][13][14][15][16] and AM-2 [17][18][19]. AM-3 [20] is a synthetic microporous titanosilicate with the structure of the mineral penkvilksite-2O and has the ideal formula Na 2 TiSi 4 O 11 Á2H 2 O.…”