Kinetics and mechanism of the hydrolysis and rearrangement processes within the assembly-disassembly-organization-reassembly synthesis of zeolites

Abstract

The hydrolysis (disassembly, D) and rearrangement (organization, O) steps of the assembly-disassembly-organization-reassembly (ADOR) process for the synthesis of zeolites have been studied. Germanium–rich UTL was subjected to hydrolysis conditions in water to understand the effects of temperature (100, 92, 85, 81, 77, and 70 °C). Samples were taken periodically over an 8–37 h period and each sample was analyzed by powder X-ray diffraction. The results show that the hydrolysis step is solely dependent on the presence of liquid water, whereas the rearrangement is dependent on the temperature of the system. The kinetics have been investigated using the Avrami-Erofeev model. With increasing temperature, an increase in rate of reaction for the rearrangement step was observed and the Arrhenius equation was used to ascertain an apparent activation energy for the rearrangement from the kinetic product of the disassembly (IPC-1P) to the thermodynamic product of the rearrangement (IPC-2P). From this information a mechanism for this transformation can be postulated.