2303a.     MONCEAUX, P.  [Controlled Oxidation of the Gas of Saint-Marcet in Air at Atmospheric Pressure.]  Mém. services chim. état. (Paris), vol. 32, 1945, pp. 253-298; Chem. Abs., vol. 42, 1948, p. 4327.

          Oxidation of CH₄, C₂H₆, and natural gas was studied under various conditions of temperature, ratio of air to CH₄, and rate of flow.  The natural gas was 92% CH₄, with <1% C₂H₆ and 5-6% N₂.  The noncatalytic oxidation of CH₄ was studied over a temperature range of 500°-900° by using gas mixtures containing 10-50 parts of CH₄ in air with flow rates from 50-300 l. per hr.  In all experiments the conversion of CH₄ to HCHO did not exceed 1%.  With increasing time of contact the yield passed through a maximum.  The yield increased with increase of temperature, the maximum shifting to shorter contact times.  <700° the most favorable composition of the gas was 20% CH₄ and 80% air, while at higher temperature it was 10% CH₄.  There was, however, a rapid decrease in the quantity of O₂ present which was shown to be due to the direct oxidation of CH₄ to CO and H₂.  A study of the decomposition and oxidation of HCHO was made which showed that >600° the decomposition in N₂ was extremely rapid at first and then approached complete decomposition more slowly.  >600° the decomposition was much slower but still appreciable.  In the presence of air the HCHO was oxidized as well as decomposed.  The order of the reaction for the formation of HCHO in respect to O₂ was found to lie at 1-2.  The oxidation of CH₂ yielded only slightly more HCHO than did CH₄ and slightly < the natural gas.  An increase in the surface of the reaction tube, with quartz, caused a decrease in the yield of HCHO and also an increased rate of decomposition of HCHO.  A surface of C increased the yield of HCHO.  At temperatures < 750° the % of O₂ entering into the reaction was markedly reduced by a C surface.  The catalytic action of oxides of N was caused by NO₂ and not by NO.