Hydrogen addition to the Andrussow process for HCN synthesis Original Research Article

The effect of hydrogen addition on HCN production by the ammoxidation of methane over Pt–Rh gauze catalyst has been examined. Upon adding small amounts of H2, the HCN selectivity increased from ∼74 to 82% on NH3 basis at 35% N2 dilution and (CH4+NH3)/O2=2, while selectivities on CH4 basis were nearly unchanged. Using air instead of oxygen, the HCN selectivity increased from 76 to 86%. However, the increase in HCN selectivity with H2 addition was accompanied by a decrease in the NH3 conversion. H2 addition with different (CH4+NH3)/O2 and CH4/NH3 ratios and with preheating of feed gases has also been investigated. The H2 produced was observed to be greater than that fed for all conditions, so that with recycle the process would require no additional source of H2. Experimental results obtained here can be qualitatively explained on the basis of a surface reaction model for Andrussow reactor described previously.