Nitration Poisoning of Silver on Al₂O₃ for the Catalytic Oxidation of Soot in NO_x-Containing Atmospheres

Abstract

Silver-based catalysts are promising candidates for soot oxidation because of their good catalytic performances and low costs compared with platinum catalysts. NO 2 acts as a strong agent for the oxidation of soot over Pt/Al 2 O 3 . However, an abnormal inhibition effect of NO x was observed over the Ag/Al 2 O 3 catalyst during the processes of soot temperatureprogrammed oxidation and transient reaction analysis. The formation of silver nitrates was confirmed by temperature-programmed decomposition of NO x , ultraviolet−visible spectroscopy, and temperature-programmed reduction with H 2 . The intrinsic reactivity of silver nitrate was found to be much lower than that of metallic silver in ″loose″ and ″tight″ contacts between soot and catalyst. Moreover, the formed silver nitrate was relatively thermally stable, with the decomposition completed at around 450 °C. At higher temperatures, the catalyst recovered and the nitrate poisoning effect no longer worked.

Soot Erased: Catalysts and Their Mechanistic Chemistry

“…Persistent uptake of diesel output materials could lead to various chronic breathing illnesses. Also, diesel exhaust is complex mixture; research indicates it has a harmful influence on human health and damages the green atmosphere [53]. The capital city of China (Beijing) is facing enormous problems with its air quality, with smog occurring very frequently [54].…”