One-pot structural conversion of magadiite into MFI zeolite nanosheets using mononitrogen surfactants as structure and shape-directing agents

Abstract

MFI-type materials with a lamellar morphology were successfully synthesized by using mononitrogen surfactants specifically designed by molecular modelling. The mononitrogen surfactants directed the recrystallization of a crystalline layered polysilicate formed in situ, the magadiite, into a zeolite ZSM-5.Moreover, the surfactants allow the preservation of the lamellar shape of the magadiite and inhibit a further growth into one dimension, leading to the formation of zeolite ZSM-5 nanosheets with a thickness comprised between 2 and 3 nm and a Si/Al ratio of 24. This simple approach paves a new way for obtaining zeolite materials of controlled size and shape for specific catalytic applications.

Hollow Zeolite Single Crystals: Synthesis Routes and Functionalization Methods

“…Nanosized crystals are generally obtained by modifying standard hydrothermal crystallization conditions for example by decreasing temperature, shortening the crystallization period, increasing supersaturation, or by adding growth inhibitors to the synthesis gel. One of the most famous examples of growth inhibition concerns the preparation of zeolite nanosheets with specific structure directing agents containing a diquaternary ammonium head group and a long hydrophobic surfactant chain . These molecules force the zeolite framework to grow perpendicularly to the alkyl chains, leading to a multilamellar stacking of sheets with a thickness corresponding to a few unit cells.…”

Hierarchical ZSM-5 beads composed of zeolite nanosheets obtained by pseudomorphic transformation

“…Several works have been carried out to introduce mesopores into zeolite [15,16] by postsynthetic demetallation of zeolite framework [17][18][19], hard-templating method (zeolite crystallization within confined space) [20][21][22][23], soft-templating method (mesopore generation via supramolecular self-assembly) [24][25][26][27][28][29] and the synthesis of nanosheets or nanosponges zeolitic materials using bifunctional surfactants or organosilanes [5,[30][31][32][33][34][35][36]. These later possesses structure directing agent functions for the formation of the zeolite framework, and an alkyl chain for inhibiting the crystalline growth of the zeolitic phase [5,[30][31][32][33][34][35].…”

Reactivity and applications of layered silicates and layered double hydroxides

“…65 In line with the above mentioned studies, we have studied the Co-silicalite-1, 78 Co-MFI and Co-BEA, 44 MOR, [79][80][81]83 ) have been synthesized using the layered silicate magadiite as the precursor and respective structure directing agents (Table 3). In recent years, zeolites such as MFI-type nanosheets 84 and omega (MAZ) 85 have been synthesized using magadiite as the precursor under hydrothermal and solvothermal conditions, respectively. Despite intensive research efforts, the application of layered silicates (kanemite, ilerite and magadiite) in the manufacture of zeolites is very limited, even though their potential is considered to be high, for example, zeolite RUB-24 (RWR), which can only be synthesized using a layered silicate RUB-18 as a precursor.…”