The present invention relates to a new 2-methyl-3-
nitrobenzoic acid preparation method, which is characterized by comprising: adding 3-nitro-o-
xylene, an
organic solvent and a catalyst to a reactor, and introducing
oxygen gas to carry out oxidation, wherein the oxidation temperature is 90-100 DEG C, and the reaction ending point is achieved when the
mass concentration of the 3-nitro-o-
xylene in the reactor is less than 1%; carrying out cooling
filtration to obtain a crude product, wherein the
mother liquor is recovered and recycled; and sequentially performing conventional alkalization method,
active carbon decoloration and acidification to obtain the 2-methyl-3-
nitrobenzoic acid finished product. According to the present invention, the
oxygen in the air is used to replace
nitric acid to oxidize the 3-nitro-o-
xylene into the 2-methyl-3-
nitrobenzoic acid, the
oxygen is used to oxidize the 3-nitro-o-xylene, the reaction is the normal pressure reaction, the
mother liquor is applied, the yield is up to 80%, and the method is the clean production method with characteristics of low risk, low
pollution and low
raw material cost.