Reactor-based approach for achieving high-silica zeolites: a fed-batch strategy

Abstract

High-silica zeolites are challenging to synthesize in hydroxide media using conventional batch reactors. This study advances beyond traditional batch crystallization methods by exploring a reactor-based strategy for tailoring zeolite properties through mid-way synthesis intervention. By employing the Fed-batch (FB) reactor strategy, we demonstrate that controlled addition of silica precursors at critical synthesis stages, without interrupting temperature or pressure conditions, grants an alternative pathway to high-silica zeolites. Two model systems were investigated: the transformation of FAU-to-CHA and FAU-to-LEV via interzeolite conversion (IZC). These controlled manipulations resulted in an elevated Si/Al ratio and distinct structural properties (e.g., internal silanols) in the final zeolites. The resulting materials were exhaustively characterized and tested in CO₂ conversion, highlighting the potential of reactor-based approaches for designing tailored high-performance zeolite catalysts.