Hierarchical Zeolite Fe-MFI as Activity Enhanced Catalysts for Selective Liquid-Phase Dehydration of 1-Phenylethanol

Selective Incorporation of Iron Sites into MFI Zeolite Framework by One-Pot Synthesis

“…These zeolites show similar characteristic vibration bands at around 445 (T–O bond), 549 (double ring vibration), 796 (external symmetric stretch), and 1224 cm –1 (between TO 4 tetrahedral). However, the iron-free silicalite-1 zeolite shows a band at 1108 cm –1 attributed to the asymmetric stretching of T–O–T bonds within the silicalite-1 zeolite framework . As for Fe-MFI at the different crystallization periods of 24, 36, and 72 h, the asymmetric stretching of the T–O–T bonds shifts to a lower frequency (∼1100 cm –1 ).…”

“…The strong intense bands at 208 and 253 nm are assigned to the charge transfer of the pπ–dπ transition between oxygen and iron atoms into the framework of all Fe-based zeolites, suggesting the tetrahedrally coordinated Fe sites incorporated into the Fe-MFI zeolite framework. In addition, the bands at 373 and 445 nm ascribed to iron oxide nanoparticles and bulk iron oxide particles, respectively, can be observed over the FeN-MFI and FeC-MFI zeolites. ,, However, no oligomeric iron oxide clusters and nanoparticles can be detected on Fe-MFI zeolite, probably because the ferrous gluconate maintains high solubility and stability under alkaline synthesis conditions (Figure c).…”

“…Recently, Zhang et al prepared Fe-S-1 zeolite by the hydrothermal synthesis method, and the characterization results illustrated that isolated Fe atoms and iron oxide clusters or nanoparticles could be simultaneously formed over the Fe-S-1 zeolite during the crystallization process owing to the low stability of Fe ions under alkaline synthesis conditions. 48 To overcome this issue, Xiao and co-workers synthesized Fe-containing MFI siliceous zeolite (FeS-1-EDTA) using ethylenediaminetetraacetic sodium as a metal chelating agent. Owing to the strong coordination between EDTA and Fe ions, isolated Fe species can be efficiently introduced into the FeS-1-EDTA zeolite framework without iron oxide clusters or nanoparticles.…”

“…In addition, the bands at 373 and 445 nm ascribed to iron oxide nanoparticles and bulk iron oxide particles, respectively, can be observed over the FeN-MFI and FeC-MFI zeolites. 48,53,54 However, no oligomeric iron oxide clusters and nanoparticles can be detected on Fe-MFI zeolite, probably because the ferrous gluconate maintains high solubility and stability under alkaline synthesis conditions (Figure 1c).…”

Hierarchical Zeolites‐confined Metal Catalysts and Their Enhanced Catalytic Performances

“…[57] In addition, the synthesis of metals entrapped inside hierarchical zeolite could be achieved via metal species were firstly introduced into conventional microporous zeolites followed by base treatment (e. g. NaOH and tetrapropylammonium hydroxide (TPAOH) )to generate intracrystalline mesopores. [100] Metals species confined within closed intracrystalline mesopores: Despite of high stability, the aforementioned metal species confined in intracrystalline/intercrystalline mesopores in hierarchical zeolite usually form open pores connected to the surface and thus lose the shape selectivity function of micropores. A recrystallization method can solve this issue.…”