Key steps influencing the formation of ZSM-5 films on aluminum substrates

Synthesis of mono- and bi-layer MFI zeolite films on macroporous alumina tubular supports: Application to nanofiltration

“…Pre-treatment of the substrate was fully described in a previous paper [7] and consists of cleaning the tube in an aqueous solution of detergent (Alconox, 3 g in 400 mL of distilled water) heated to 60 °C for 1 h. They were then rinsed with distilled water, dried at 70 °C and cooled down to ambient temperature. The influence of the cleaning step on the film formation was also evaluated.…”

“…The four peaks observed for the alumina tubes are characteristics of the α- layer is indexed in the monoclinic symmetry, which reveals that the silicon to aluminum molar ratio of the ZSM-5 zeolite is above 70 [60]. More precisely, the silicon to aluminum ratio was assessed to be 185 according to the relationship existing between the volume and the aluminum atom number of the unit cell [7,56]. In comparison to the Si/Al ratio of 600 in the starting solution, it can be concluded that few of aluminum from the alumina substrate are incorporated into the zeolite coating.…”

“…5-c). The silicon to aluminum ratio of the bilayer film was increased from 185 to 305 according to the relationship existing between the volume and the aluminum atom number of the unit cell [7,56].…”

“…Zeolites have an important role in addressing some of the major problems facing society in the twenty-first century, such as energy storage, water and air decontamination, therapeutics (drug delivery,...) and catalysis [1][2][3][4][5][6][7][8][9][10][11]. Due to these manifold applications of crystalline zeolites, increasing attention worldwide has been paid to the preparation of zeolites in forms suitable for practical utilization and to the development of methods for producing zeolite objects (films, membranes, pellets, microspheres,...) with controllable thickness.…”

“…For example, high-silica zeolites (HSZ) are used for their sorption properties or good corrosion resistance while complementary sorption or antimicrobial properties of low-silica zeolite (LSZ) such as Y zeolite (FAU) [47] or modified zeolite A (LTA) [48] are exploited. Indeed, the combination of several zeolite layers in the same film raises more and more interest for the volatile organic compound (VOC) removal and the pollutants adsorption, including on-orbit decontamination [7][8][9]49]. Different aims are followed when synthesizing multi-layer zeolite membranes: 1) improved separation selectivity by repeated crystallizations of the same zeolite, 2) novel properties by combination of layers of different zeolite types [8,9,42,43,49].…”