A Method for HCN Synthesis from Methane and Nitrogen Assisted by Magnetron Sputtering

As an important chemical, hydrogen cyanide (HCN) is conventionally prepared in industry through the conversion of methane (CH4) and ammonia (NH3) at a high temperature above 1000 ℃, and in most cases, this process requires the use of the noble metal Pt as the catalyst. In this work, we designed and constructed a magnetron sputtering reaction device and, for the first time, utilized it to explore the direct synthesis of HCN at room temperature via the reaction of CH4 and nitrogen (N2), which was facilitated by the generated plasma. The experimental result shows that CH4 and N2 can produce HCN and NH3 in this plasma reaction, and it is found that the reaction conditions such as the reaction time, the reaction current, the ratio of initial reactants and the type of metal target material have significant influences on the conversion rate of CH4 and the yield of HCN. Through optimization experiments, the optimal reaction conditions of the developed reaction device have been obtained: Pt target is selected for the magnetron sputtering source, the ratio of the reactant gases is set as CH4:N2 = 1:4 (total 450Pa), the reaction current is 90 mA and the reaction time is 6 min. Under these conditions, the conversion rate of CH4 reaches 37.9%, and the yield of HCN is 97.7 μmol. The developed method of synthesizing HCN assisted by the CH4 and N2 plasma generated through magnetron sputtering has the advantages of being green and direct, requiring no heating and no additional catalyst loading, and possessing high selectivity. This study not only provides a new method for HCN synthesis, but also demonstrates that the sputtering device has the potential to be employed for synthesizing other important compounds or investigating reaction mechanisms when it is combined with particular characterization instrument.