Insights into 1,2-dihydroxybenzene addition on twin suppression during the secondary hydrothermal synthesis of b-oriented MFI zeolite films

Abstract

Elimination of parasitic twin crystals on the surface of highly b-oriented MFI zeolite films remains an interesting but challenging issue. 1,2-Dihydroxybenzene (C6H6O2), as complex agent to restrict the activity of siliceous species, was introduced into the secondary hydrothermal synthesis solution. The effect of the synthesis parameters such as crystallization temperature and reaction duration on the morphology of the resulting oriented MFI zeolite films was systematically investigated. The addition of C6H6O2 suppressed the growth rate of MFI crystals in the films along both the c-axis and a-axis directions. The suppression was even more severe for the a-axis directions because of only very limited siliceous species available for the seed crystal growth as well as the relatively fast depletion of them for c-axis growth. The twin elimination effect of the C6H6O2 addition was further validated by the successful achievement of highly b-oriented MFI films on various film supports under the optimum synthesis condition.