Nucleation, Growth, and Robust Synthesis of SPP Zeolite: Effect of Ethanol, Sodium, and Potassium

Self-pillared pentasil (SPP) zeolite is a hierarchically-structured zeolite comprised of single-unit cell thick MFI nanosheets arranged in a "house of cards" structure. The nucleation and growth of SPP proceeds through three phases involving the evolution of precursor amorphous nanoparticles to MFI nanosheets and then rotational intergrowth of sheets to produce the SPP morphology. This paper expands upon an earlier report to extend understanding of nucleation and growth events throughout the entire preparation process, from hydrolysis of the silica source to high conversion to crystals. Common aspects with the extensively investigated clear-sol silicalite-1 system are identified. Evaporation of co-solvent ethanol was found to accelerate the crystallization significantly. Furthermore, robust synthesis of SPP with high density of well-developed single-unit cell domains has been achieved with addition of potassium and sodium to the synthesis sols.