Disclosed is a method of
catalytic oxidation of lignite using
oxygen as an oxidant at
atmospheric pressure, belonging to a method of mild oxidation of lignite. The method is used to mildly oxidize the lignite using the
oxygen as the oxidant under the action of a
nitroxide radical catalyst and a
metal salt or
metal oxide cocatalyst; the process comprises the following steps: pulverizing the lignite to 200 meshes or less,
drying a pulverized
coal sample at a temperature of 80° C. in vacuum for 10 h, weighing 0.5 g of the treated
coal sample, sequentially adding 10 ml of
acetic acid, 0.5 mmol of a catalyst and 0.15 to 0.25 mmol of a cocatalyst into a round-bottom flask, connecting a tee joint to an upper orifice of a condenser
pipe, replacing
oxygen in vacuum for three times so that the round-bottom flask is filled with the oxygen, keeping
oxygen pressure at 0.1 MPa, reacting at a temperature of 80° C. to 120° C. for 4 to 12 h; filtering after the reaction is finished; decompressing a filtrate to remove the
acetic acid, adding a small amount of
ethyl acetate to dissolve, then using an excess CH2N2 /
ether solution to esterify for 10 h at
room temperature, using 0.45 μm
filter paper to filter, and analyzing an esterified product through a
gas chromatography-
mass spectrometer. The method has the advantages of using the oxygen as the oxidant, having low price, having no
toxicity, and achieving
environmental protection and mild conditions.