A mixture of methane and oxygen when passed through the heated molybdenum oxide, the formation of methanal takes place.
$C H _{4}+ O _{2} \stackrel{\text { Mo-oxide }}{\longrightarrow } \underset{\text { Methanal }}{ H C H O }+ H _{2} O$
This method is used for the manufacture of methanal by controlled oxidation of methane in the air in presence of various metallic oxides as a catalyst.