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 the 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.
Highlights
A newly developed method for the synthesis of new zeolites coined the assembly−disassembly−organization−reassembly (ADOR) process has become well established in producing new zeolites that would not have been feasible through traditional routes (Scheme 1).[1−7]Parent zeolites prepared for the ADOR process must have suitable chemical and physical properties in order to produce new daughter zeolites
We present a kinetic analysis of the two most prominent steps (D and O) in the ADOR process, found by sampling the reaction and using powder X-ray diffraction to follow the evolution of the lattice spacing with time
The extent of reaction vs time was plotted for the reactions run at 100, 92, 85, 81, 77, and 70 °C, and each plot was fitted with the Avrami−Erofeev model (Figure 3)
Summary
Parent zeolites prepared for the ADOR process must have suitable chemical and physical properties in order to produce new daughter zeolites. The layered intermediates that are formed on the disassembly of zeolites such as UTL seem to be relatively easy to manipulate to form new structures. These d4r-containing zeolites that disassemble into clusters (and not layers), such as polymorph C of zeolite beta, are much more difficult to organize and reassemble successfully
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