Solid-state recrystallization of aluminum-containing kanemite varieties to ferrierite

Abstract

High-silica ferrierites (Si/Al=12–35) were prepared by solid-state recrystallization of aluminum-containing kanemite varieties intercalated with piperidine as template. A thermal pretreatment of the kanemite/template mixture at about 360 K prior to recrystallization at 413–433 K was found to be an essential step of the preparation process. Water-soluble sodium silicate(s) formed as the by-product of recrystallization could be easily removed by washing. It was found that the maximum yield of ferrierite increases with decreasing sodium content of the silica/alumina source (e.g., 90% at 1 mmol Na g −1). The recrystallization kinetics was studied varying the temperature and sodium content of the starting material. With decreasing aluminum content of the starting material and, hence, of the ferrierites obtained, both the accessibility of the zeolitic pore space to pyridine and the concentration of lattice defects increased significantly. This effect is discussed in terms of diffusion restrictions due to extra-framework aluminum species and pore enlargement associated with lattice vacancies.