The Catalytic Chemistry of HCN + NO₂ over Na− and Ba−Y,FAU:  An in Situ FTIR and TPD/TPR Study

The adsorption of HCN and the reaction of HCN with NO(2) over Na-, and Ba-Y,FAU zeolite catalysts were investigated using in situ FTIR and TPD/TPR spectroscopies. Both catalysts adsorb HCN molecularly at room temperature, and the strength of adsorption is higher over Ba-Y than Na-Y. Over Na-Y, the reaction between HCN and NO(2) is slow at 473 K. On Ba-Y, HCN reacts readily with NO(2) at 473K, forming N(2), CO, CO(2), HNCO, NO, N(2)O, and C(2)N(2). The results of this investigation suggest that initial step in the HCN + NO(2) reaction over these catalysts is the hydrogen abstraction from HCN, and the formation of ionic CN- and NC- species. The formation of N(2) can proceed directly from these ionic species upon their interaction with NO+. Alternatively, these cyanide species can be oxidized to isocyanates which then can be further transformed to N(2), N(2)O and CO(x) in their subsequent reaction with NO(x).