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Study of the reduction and reoxidation of a CaO surface

Filip Acke ; Itai Panas (Institutionen för oorganisk miljökemi) ; Dan Strömberg
J Phys Chem B (1520-5207). Vol. 101 (1997), 33, p. 6484-.
[Artikel, refereegranskad vetenskaplig]

The reduction of NO with CO and H2 is shown to comprise two basic reactions: a surface oxygen abstraction by the reducing agent and a reoxidation of the surface by NO. The former reaction step has been demonstrated by transient CO2 formation during CO exposure of oxidized CaO surfaces, while the latter was demonstrated by N2 and/or N2O transient formation during NO exposure of a prereduced CaO surface. It was shown that at low temperatures (between room temperature and 500 °C) both N2 and N2O were formed, but at temperatures above 500 °C only N2 was observed. The activation energies of the respective steps have been determined using temperature-programmed reaction experiments. The activation energy of the surface oxygen abstraction was determined to be 25 kcal/mol and is similar to the apparent activation energy of the overall reaction. The activation energy of the NO bond breakage was determined to be maximum 10 kcal/mol as measured by N2O formation. The importance of an N2O2- or N2O22- intermediate in the formation of N2O will be discussed, and the importance of N2O decomposition in forming N2 at temperatures above 500 °C will be compared with a N surface diffusion mechanism.

Nyckelord: reduction, nitric oxide, carbon monoxide, hydrogen, surface, calcium oxide, mechanism, nitrous oxide

Denna post skapades 2009-03-20. Senast ändrad 2010-04-30.
CPL Pubid: 91706


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