Unique Functions of Heteroatom-incorporated Zeolites Prepared from Amorphous Mixed Metal-oxide Precursors

Zeolites have been considered as key materials in the fields such as catalysis and adsorption due to their ease of tunability via isomorphous substitution with heteroatoms and surface decoration with metal/metal-oxide nanoparticles. The resulting function and performance of zeolites are well-known to be significantly dependent on their preparation methods. This review paper gathers some unique zeolites that were prepared hydrothermally from amorphous Si-based mixed metal oxides. The initial two examples, Ga-introduced MFI-type zeolites and MFI-type zeolites dually substituted by Al and Fe, exhibited the high selectivity to CO in the oxidative conversion of methane and the long lifetime in the reaction of dimethyl ether to olefins, respectively, as catalysts. The combination of Ce-decorated MFI-type zeolites and Pd nanoparticles enabled the oxidative conversion of methane at quite low reaction temperatures to produce ethane. The last examples overviewed in this paper were based on the intentional construction of paired heteroatom (Al or Ga) sites in CHA- and MFI-type zeolites, which behaved as ion-exchange sites for capturing divalent cations.