Conditions for HCN synthesis and catalyst activation over Pt–Rh gauzes

We have examined different processing conditions for the synthesis of HCN by the ammoxidation of methane over woven Pt–Rh gauzes in an autothermal bench scale reactor. Compared to the conventional air processes, the HCN yield can be improved 10–15% by preheating the reactant gases, and HCN throughput can be increased 140% by removing N₂ from the feed stream. We were able to attain operation in a high pressure bench scale reactor, and HCN yields were maintained above 0.60 up to 3.5 atm at 300% of the throughput achievable at 1 atm.

We also investigated activation of the Pt–Rh gauze catalyst which occurs through facet and pit formation on the metal surface. A high temperature treatment reduced activation times from 30 to 3 h. Pits on the catalyst surface resulted from increased temperatures and NH₃ in the reactant gas, but HCN processing conditions were necessary for the catalyst to achieve best performance.