| Popis: |
A multistep mechanism has been elucidated for the reduction of NO x in the presence of ethanol over silver-exchanged zeolite Y (Ag/Y). Ethanol reacts with O 2 and/or NO 2 to form acetaldehyde at temperatures as low as 200 °C. Surface acetate ions, formed from the oxidation of acetaldehyde, react with NO 2 to yield nitromethane, a critical intermediate in subsequent deNO x chemistry. CN − , NC − , and NCO − are intermediates likely bound to silver ions. Both CN − and NC − are stable toward reaction under experimental conditions. A significant difference exists between the catalytic activities of Ag/Y and Ag/ γ -Al 2 O 3 ; oxidation of ethanol to acetate at low temperature is significantly faster over Ag/Y than over Ag/ γ -Al 2 O 3 , and both NO 2 and O 2 are effective oxidants over Ag/Y. With Ag/Y, pretreatment with either O 2 or H 2 does not affect the yield of N 2 , which approaches 60% and remains constant for at least 5 h, making this catalyst promising for NO x reduction. |
Full Text from ScienceDirect