Kinetics of nitric oxide reduction with pure and potassium-doped carbon

Abstract

The kinetics of the reduction of nitric oxide with pure and potassium-doped carbon, NO+C=1/2 N2+CO, were investigated. For the reaction of NO with pure carbon, measurements were made in the temperature range from 1750 K to 2130 K and at initial NO pressures between 5×10−3 Pa and 7×10−2 Pa. The reaction was first order with respect to nitric oxide at NO pressures below 3×10−2 Pa. The activation energy was 54 kJ/mol for temperatures below 2000 K, while at higher temperatures a second (parallel) reaction became noticeable with a definitely higher activation energy. Potassium-doped carbon was prepared by a molecular beam technique. AES studies verified that potassium was intercalated into the graphite surface and that the potassium-to-carbon ratio changed continuously with sample temperature. The reduction of NO with K-doped carbon was investigated in the temperature range from 710 K to 1080 K and at initial NO pressures between 7×10−5 Pa and 6×10−4 Pa while monitoring, in-situ using AES the K/C-ratio of the surface. The NO reduction rate rose linearly with K/C. Compared to pure carbon, the reaction rate for the NO reduction with K-doped carbon increased by a factor in the range of 104. The activation energy for the NO reduction with K-doped carbon was found to be 82 kJ/mol.