Review of Ag/Al2O3-Reductant System in the Selective Catalytic Reduction of NO x
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Ag/Al2O3 is a promising catalyst for the selective catalytic reduction (SCR) by hydrocarbons (HC) of NO x in both laboratory and diesel engine bench tests. New developments of the HC-SCR of NO x over a Ag/Al2O3 catalyst are reviewed, including the efficiencies and sulfur tolerances of different Ag/Al2O3-reductant systems for the SCR of NO x ; the low-temperature activity improvement of H2-assisted HC-SCR of NO x over Ag/Al2O3; and the application of a Ag/Al2O3-ethanol SCR system with a heavy-duty diesel engine. The discussions are focused on the reaction mechanisms of different Ag/Al2O3-reductant systems and H2-assisted HC-SCR of NO x over Ag/Al2O3. A SO2-resistant surface structure in situ synthesized on Ag/Al2O3 by using ethanol as a reductant is proposed based on the study of the sulfate formation. These results provide new insight into the design of a high-efficiency NO x reduction system. The diesel engine bench test results showed that a Ag/Al2O3-ethanol system is promising for catalytic cleaning of NO x in diesel exhaust.
KeywordsAg/Al2O3 Hydrocarbon HC-SCR NO SO2 Hydrogen Mechanism Diesel engine
This work was financially supported by the National Science Fund for Distinguished Young Scholars of China (20425722), Key Program of NNSFC (20437010) and Ministry of Science and Technology of China (2006AA060304).
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