Using Acetylene for Selective Catalytic Reduction of NO in Excess Oxygen

Acetylene as a reducing agent for selective catalytic reduction of NO (C₂H₂-SCR) was investigated over a series of metal exchanged HY catalysts, in the reaction system of 0.16% NO, 0.08% C₂H₂, and 9.95% O₂ (volume percent) in He. 75% of NO conversion to N₂ with hydrocarbon efficiency about 1.5 was achieved over a Ce-HY catalyst around 300 °C. The NO removal level was comparable with that of selective catalytic reduction of NO_x by C₃H₆ reported in literatures, although only one third of the reducing agent in carbon moles was used in the C₂H₂-SCR of NO. The protons in zeolite were crucial to the C₂H₂-SCR of NO, and the performance of HY in the reaction was significantly promoted by cerium incorporation into the zeolite. NO₂ was proposed to be the intermediate of NO reduction to N₂, and the oxidation of NO to NO₂ was rate-determining step of the C₂H₂-SCR of NO over Ce-HY. The suggestion was well supported by the results of the NO oxidation with O₂, and the C₂H₂ consumption under the conditions in the presence or absence of NO.