2232.     MEDVEDEV, S. S.  [Catalytic Oxidation of Methane to Formaldehyde.  I.]  Trans. Karpov Chem. Inst., No. 3, 1924, pp. 54-65; Chem. Abs., vol. 21, 1927, p. 2457.

        Medvedev experimented with Au, Pt, Mn₂O₃, NiO, Al₂O₃, CuO, Ag₂O, PbO, and CeO₂ catalysts on an asbestos base.  At low rates of flow (1 l. in 20 min.) and at low temperatures (250°-350°) only CO₂ is obtained.  Mn₂O₃ proved to be the most, CuO the least active catalyst.  At temperatures above 500° and a rate of 1 l. per min., traces of HCHO and a little CO appear besides CO₂ with CuO as a catalyst, but not with the others.  The Medvedev interprets as evidence of the acceleration of all reactions by the catalysts or their nonspecificity.  Glass at 600° gives a large yield of HCHO, which is attributed to the lesser chemical activity of such a surface in not being able to form peroxides as in the case of metals and their oxides.  With CH₄ (containing 3-7% H₂) Pb catalysts (borates, phosphates, and their mixtures) gave the highest yields of HCHO at 500°-700°.  The activity of these catalysts, however, was referred to the presence of volatile impurities, as lead chloride, since a long series of experiments showed that small concentrations of HCl (0.13%) in the gases was very beneficial in raising the relative yield of HCHO.  Medvedev’s best results are exceptionally high.  Thus at 600° from a mixture containing 13.8% CH₄ and 17.98% O₂ with a velocity of 0.23 l. per min., the yield of HCHO was 5.02% of the CH₄ taken, 8.65% CH₄ being decomposed, that is, 58.04% of the decomposed CH₄ decomposed to HCHO.

        MEHL, R. F.  See abs. 3648, 3649.