Combining Soft- and Hard-Templating Approaches in MWW-Type Zeolites

Abstract

A combination of hard-templating (HT) and soft-templating (ST) approaches was studied to obtain MWW-type materials with intermediate physicochemical properties. The HT methodology involved the introduction of carbon particles as hard templates during gel synthesis to obtain a layered zeolitic precursor (LZP) with particles possessing a microspherical morphology. The LZP obtained was treated with surfactants as soft templates to expand the layers of the LZP, followed by a pillaring procedure. The materials were characterized by X-ray diffraction, transmission and scanning electron microscopy, elemental analysis and N2 adsorption. The results demonstrate that the obtained material possesses intermediate properties from both approaches, with interparticle mesopores/macropores and pore sizes between 18 and 46 Å. However, the ST procedure causes a partial disruption of some microspheres, forming small crystallite aggregates, and results in a decrease in the number of interparticle mesopores/macropores previously formed by the HT method.

Recent Advances on Porous Siliceous Materials Derived from Waste

“…On the contrary, the hard templating, also known also as "nanocasting", involves solid materials, such as polymers, metal oxides, and carbon NPs, as templating agents. Herein, the morphology of the final material was directly determined by rigid templates, removed by carbonization or acid treatments, assuring uniformity in the porous structure [185][186][187][188]. Porous materials find applications in a plethora of different key fields, such as the sorption and storage of chemicals, ion exchange, catalysis, filters, biomedicine and drugdelivery systems, and thermal and acoustic insulation [174][175][176][177][178][179][180].…”

“…On the contrary, the hard templating, also known also as "nanocasting", involves solid materials, such as polymers, metal oxides, and carbon NPs, as templating agents. Herein, the morphology of the final material was directly determined by rigid templates, removed by carbonization or acid treatments, assuring uniformity in the porous structure [185][186][187][188]. To the best of the authors' knowledge, highly porous siliceous materials are mostly obtained by means of soft-templating routes.…”

Zeolitic Microporous Materials and Their Applications

“…Several interesting studies about synthesis of zeolites with different topologies, structures and properties are also reported in this Special Issue [ 5 , 6 , 7 , 8 ]. The synthesis of MWW-type materials with intermediate physicochemical properties is investigated by Schwanke et al [ 5 ] via the combination of hard- and soft-templating approaches in order to control the porosity of the materials. In this manner, it is possible to obtain MWW zeolites with pore systems comprising different porosities either in the interparticle and interlamellar ranges, which may potentially be useful as catalysts in reactions involving bulky reactants, and in the encapsulation of nanoparticles or biomolecules.…”

“…Several interesting studies about synthesis of zeolites with different topologies, structures and properties are also reported in this Special Issue [5][6][7][8]. The synthesis of MWW-type materials with intermediate physicochemical properties is investigated by Schwanke et al [5] via the combination of hard-and soft-templating approaches in order to control the porosity of the materials.…”