Development of Synthetic Route for Fe-substituted MWW-type Zeolites Using Mechanochemical Method

Fe-substituted MWW-type zeolites ([Fe]-MWWMc) were successfully synthesized by a mechanochemically assisted hydrothermal synthesis, termed the mechanochemical method, for the first time and compared with samples prepared by the conventional hydrothermal method ([Fe]-MWWFrr). A mechanochemical reaction between SiO2 and a-FeOOH, which is the first step of the mechanochemical method, yielded an amorphous Si-Fe composite oxide that consisted of tetrahedrally coordinated Fe species in a Si02 network, as confirmed by X-ray diffraction, UV-vis and Fourier transform infrared spectroscopies. A hydrothermal treatment for crystallization of the zeolite using a thus-prepared amorphous Si-Fe composite as a precursor as the second step led to the formation of [Fe]-MWWMc zeolites with well-introduced and dispersed Fe species in their framework. The improved homogeneity of the Fe species in [Fe]-MWWMc resulted in less extra-framework Fe species compared with [Fe]MWWIrr. The mechanochemical method was thus confirmed as an efficient route for the synthesis of metallosilicates with well-introduced and dispersed heteroatoms in their framework.