Synthesis and proton conductivity of sulfonic acid functionalized zeolite BEA nanocrystals

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Abstract
The objective of this study is to prepare sulfonic acid functionalized zeolite BEA nanocrystals, and determine the bulk proton conductivity of this new material. Phenethyl functionalized zeolite BEA nanocrystals are synthesized using a mixture of fumed silica and phenethyltrimethoxysilane as silica sources. Contact of the phenethyl zeolite BEA nanocrystals with concentrated sulfuric acid removes the organic structure-directing agent (SDA) and simultaneously sulfonates the phenethyl moieties. Detailed characterizations of the zeolite BEA nanocrystals are performed using dynamic light scattering (DLS), Fourier transform Raman spectroscopy (FT-Raman), 29Si cross-polarization magic angle spinning nuclear magnetic resonance spectroscopy (29Si CPMAS NMR), 13C CPMAS NMR, 1H MAS NMR, thermogravimetric (TGA) analyses, transmission electron microscopy (TEM) and powder X-ray diffraction (XRD). Sulfonic acid functionalized zeolite BEA nanocrystals have proton conductivities in the range of 1.2 × 10−3–1.2 × 10−2 S/cm compared to 1.5 × 10−4 S/cm for unfunctionalizated zeolite BEA.