Low-Temperature Activation of Methane with Nitric Oxide and Formation of Hydrogen Cyanide over an Alumina-Supported Platinum Catalyst

This study demonstrated methane activation with subsequent conversion to hydrogen cyanide (HCN) at low temperatures using nitric oxide (NO) as the sole oxidant together with an alumina-supported platinum catalyst (Pt/Al2O3). This process afforded HCN even at 300 degrees C, indicating that C-H bond cleavage, NO dissociation, and simultaneous C-N coupling all occurred at this reduced reaction temperature. The HCN yield increased with increasing temperature, resulting in a 3.2% yield with a selectivity of 49% at 425 degrees C. This yield was much greater than that obtained from the reaction of CH4 with NH3 and O-2, which suggests a reaction mechanism different from the Andrussow process. The HCN production rate was 11.4 mmol g(-1) h(-)(1) and the corresponding turnover frequency was 253 h(-)(1), both of which were far superior to those obtained in previous studies at similar reaction temperatures. The Pt catalyst was found to be stable and could continuously produce HCN for at least 100 h. In situ X-ray absorption fine structure analyses suggested that the high resistance of this material to deep oxidation facilitated HCN formation. The difference between X-ray absorption near-edge structure spectra before and during the reaction indicated that the specific adsorbates on the catalyst were dependent on the reaction temperature and that the extent of adsorbed Pt-CN species was correlated with the reactivity of the material.

Automated summary

This study demonstrated the conversion of methane to hydrogen cyanide at low temperatures using NO and a Pt/Al2O3 catalyst, yielding higher HCN production rates and stability compared to traditional methods. In situ X-ray absorption fine structure analyses indicated that specific adsorbates on the catalyst were temperature-dependent and the presence of Pt-CN species correlated with the material's reactivity.