Hydrothermal synthesis of Ga-substituted MFI zeolites via a mechanochemical process and their catalytic activity for methane transformation

Mechanochemical Route for Preparation of MFI-Type Zeolites Containing Highly Dispersed and Small Ce Species and Catalytic Application to Low-Temperature Oxidative Coupling of Methane

“…The baseline for all XRD patterns was elevated in the 2θ range of 5−15°, presumably owing to scattered X-rays originating from the apparatus used, as observed in our previous studies analyzing a variety of materials with the same diffractom-eter. [32][33][34]36 Milling triggered the amorphization of fluoritetype CeO 2 (see XRD pattern for ball-milled mixture of SiO 2 and CeO 2 •nH 2 O in Figure 2A), as evidenced by the disappearance of the diffraction peaks observed prior to milling. Instead, in agreement with our previous reports, small diffraction peaks, attributable to a slight β-Si 3 N 4 contamination from the pot and balls used for pulverization, were observed at 2θ values of 13.4, 23.4, 27.0, 33.7, 36.0, 41.4, and 52.1°.…”

“…Instead, in agreement with our previous reports, small diffraction peaks, attributable to a slight β-Si 3 N 4 contamination from the pot and balls used for pulverization, were observed at 2θ values of 13.4, 23.4, 27.0, 33.7, 36.0, 41.4, and 52.1°. 32,34 In addition, owing to the composition of the pot and balls, 37 a small amount of Al contamination (Si/Al = 194) was detected.…”

“…The spectrum in Figure 3B also showed the emergence of a new absorption band at 951 cm −1 , similar to our previous ball-milled mixture consisting of SiO 2 and β-Ga 2 O 3 . 32 Both changes were attributed to the formation of Si−O−Ce bonds in the composite as a result of the mechanochemical reaction between SiO 2 and CeO 2 . The STEM-EDS images in Figure 2B suggest that this reaction occurred at the interface of the oxide particles, leading to the formation of core−shell-structured particles, in which the core and the shell consist of SiO 2 and CeO 2 , respectively.…”

“…Substituting-heteroatom-free MFI-type zeolite (hereafter, silicalite-1), which was reported in our previous paper, 32 was also synthesized in almost the same manner as Ce-MFI MC . In this case, pulverization was performed in the absence of CeO 2 • nH 2 O to obtain a ball-milled SiO 2 sample free of Ce atoms.…”

New avenues for mechanochemistry in zeolite science

“…68,69 Recently, the successful synthesis of a titanosilicate zeolite with MWW framework combined the described milling pretreatment with a dry-gel conversion method to produce highly efficient catalysts for the epoxidation of 1-hexene. 70 In a similar manner to the fabrication of the Ti/Si-oxide composite precursor, researchers have prepared Sn/Si-, Mn/Si-, Ga/Si-, and Zn/Si-oxide precursors for the synthesis of zeolites Sn-beta (*BEA), 71 Sn-silicalite-1 (MFI), 72 Mn-MCM-41, 73 Mnsilicalite-1, 74 Ga-silicalite-1 75 and Zn-silicalite-1, 76 respectively. PDF analysis, SEM images and PXRD patterns of the study investigating zinc-containing MFI-type zeolite are shown in Fig.…”