Formation of Nanostructured Zeolite Particle Surfaces via a Halide/Grignard Route

A two-step reaction sequence, dealumination via thionyl chloride followed by reaction with a Grignard reagent, has created a nanoscale morphology that appears as significantly roughened outer surfaces on zeolite 4A particles. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) measurements revealed that such surface nanostructures are composed of Mg(OH) 2 crystals. The formation mechanism of this specific surface morphology was explored. It was discovered by solid-state 29 Si and 27 Al NMR and XPS surface analysis that thionyl chloride partially removes aluminum from the zeolite 4A framework and yields NaCl and AlCl 3 . Precipitation of these extracted inorganic salts on the surfaces of zeolite particles occur. Subsequently, methylmagnesium bromide is reacted with 2-propanol in a quenching process and generates Mg(OH) 2 . The previously deposited NaCl and AlCl 3 nanoparticles on zeolite surfaces are believed to function as heterogeneous nuclei for the growth of Mg(OH) 2 crystals and thereby creates the nanostructured surface morphology. The modified particles are shown in previous work to provide enhanced interfacial adhesion in polymeric composites.