Hydrotalcite-zeolite composites as precursors for catalysis: Synthesis, transformation and structural stability

Abstract

In this study, Cu-based hydrotalcite-zeolite (CuHT-ZSM-5) composites were synthesized and characterized to explore their potential as catalyst precursors. The hydrotalcite phase was successfully formed on ZSM-5 zeolite supports with different Si/Al ratios under standard co-precipitation conditions (pH = 10, T = 65 °C). Structural analysis confirmed that the zeolite framework remained intact during synthesis, with only minor acidity modifications observed for Al-containing ZSM-5. The hydrotalcite layers were composed of copper, magnesium and aluminium cations, while the carbonate anions were used as interlayer anions. Thermal decomposition of the CuHT phase resulted in in-situ generation of highly dispersed mixed metal oxides (MMOs). Textural characterization revealed that optimal calcination temperatures (500–600 °C) allow to obtain materials with high specific surface areas, while excessive heating (≥800 °C) led to partial collapse of the porous structure and formation of new MgSiO3 phases. The study demonstrates that CuHT-ZSM-5 composites are structurally stable, thermally resistant, and exhibit tuneable acidity – key properties for catalytic applications. These findings open new possibilities for optimizing MMO-zeolite catalysts, particularly for NH3-SCO reactions.