Maximizing Active Fe Species in ZSM-5 Zeolite Using Organic-Template-Free Synthesis for Efficient Selective Methane Oxidation

• DOI: 10.1021/jacs.2c13351
• Publication Date: 2023-02-14T15:56:00Z
• Authors: Qingpeng Cheng; Guanna Li; Xueli Yao; Lirong Zheng; Junhu Wang; Abdul-Hamid Emwas; Pedro Castaño; Javier Ruiz-Martínez; Yu Han
• Keywords: ZSM-5; Oxygenate

The selective oxidation of CH4 in the aqueous phase to produce valuable chemicals has attracted considerable attention due its mild reaction conditions and simple process. As most widely studied catalyst for this reaction, Fe-ZSM-5 demonstrates high intrinsic activity selectivity; however, prepared using conventional methods a limited number active Fe sites, resulting low conversion per unit mass catalyst. This study reports facile organic-template-free synthesis strategy that enables incorporation more into zeolite framework with higher dispersion degree compared methods. Because incorporated way is readily transformed isolated extra-framework species under thermal treatment, overall effect method (Fe-HZ5-TF) 3 times as many catalytically sites Fe-ZSM-5. When used 0.5 M H2O2 at 75 °C, Fe-HZ5-TF produced C1 oxygenate yield 109.4 mmol gcat-1 h-1 (a HCOOH selectivity 91.1%), surpassing other catalysts reported date. Spectroscopic characterization density functional theory calculations revealed are mononuclear form [(H2O)3Fe(IV)═O]2+ bound Al pairs framework. differs from Fe-ZSM-5, where binuclear acts site. Analysis product evolution during suggests radical-driven pathway explain activation site subsequent oxygenates.