Methane activation and oxidation in sulfuric acid
2002 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 8, no 14, 3277-3283 p.Article in journal (Refereed) Published
The H/D exchange observed when methane is contacted with D(2)SO(4) at 270-330 degrees C shows that the alkane behaves as a sigma base and undergoes rapid and reversible protonation at this temperature. DFT studies of the hydrogen exchange between a monomer and a dimer of sulfuric acid and methane show that the transition states involved in the exchange are bifunctional, that is one hydrogen atom is transferred from a hydroxy group in sulfuric acid to methane, while one hydrogen atom is abstracted from methane by a non-hydroxy oxygen atom in sulfuric acid. All the transition states include a CH(5) moiety, which shows similarities to the methanium ion CH(5) (+). The calculated potential activation energy of the hydrogen exchange for the monomer is 174 kJ mol(-1), which is close to the experimental value (176 kJ mol(-1)). Solvation of the monomer and the transition state of the monomer with an extra sulfuric acid molecule, decrease the potential activation energy by 6 kJ mol(-1). The acid-base process is in competition, however, with an oxidative process involving methane and sulfuric acid which leads to CO(2), SO(2), and water, and thus to a decrease of acidity and loss of reactivity of the medium.
Place, publisher, year, edition, pages
2002. Vol. 8, no 14, 3277-3283 p.
density functional calculations, H/D exchange, methane, oxidation, sulfuric acid
IdentifiersURN: urn:nbn:se:uu:diva-121908DOI: 10.1002/1521-3765(20020715)8:14<3277::AID-CHEM3277>3.0.CO;2-5ISI: 000176996000023PubMedID: 12203359OAI: oai:DiVA.org:uu-121908DiVA: diva2:306908