OXIDATION OF METHANE TO FORMALDEHYDE OVER FE SIO2 AND SN-W MIXED OXIDES/

In an attempt to develop new catalysts for the formation of formaldehy de from methane, the promotion effect of Fe on SiO2 and that of Sn on WO3 have been studied. The formation of formaldehyde on silica can be appreciably enhanced by the impregnation of Fe, as far as iron loading s are kept below 0.1 atom.% (Fe/Si x 100). In the case of Sn-W-Ox cata lysts, both the addition of Sn to WO3 and that of W on SnO2 were effec tive to the selective formaldehyde formation. Absorption spectra (UV-V is) and ESR measurements revealed that tetrahedrally coordinated Fe3in the silica network plays an important role in the formation of form aldehyde. A thin surface layer consisting of W and Sn oxides can accou nt for the selective formaldehyde formation on the Sn-W-Ox catalysts.