Investigation and Modeling of the Hydrothermal Stability of Technically Relevant Zeolites

The dense-structured zeolites of types ZSM-5 (MFI) and mordenite (MOR) of different SiO₂/Al₂O₃ moduli are relatively stable under treatment by liquid water for 72 hours up to 513 K. The open-structured zeolites of types Y in dealuminated modification (FAU) and beta (BEA) undergo strong decomposition in the same range. For these two sample types a mathematical model for the decomposition of the zeolite framework is established that takes into account the influence of modulus as well as temperature. Here the kinetic of the solid phase reaction is a superposition of two different mechanisms described by the Monod equation. Dedicated to the late of Wolfgang Schirmer.