The invention provides a synthesis method of 2-amino-3-methyl-5-chlorobenzoic acid, which comprises the following steps: respectively pumping m-
xylene and
liquid chlorine into a microchannel reactor for reaction, and purifying to obtain 2-chloro m-
xylene; s2, adding a catalyst into the 2-chloro-m-
xylene obtained in the step S1, introducing the mixture into a micro-channel reactor, introducing an oxidizing
reagent, carrying out a reaction, and purifying a product to obtain 2-chloro-3-methyl
benzoic acid; s2, dissolving the 2-chloro-3-methyl
benzoic acid obtained in the step S2 and alkali in a
solvent 1, introducing
ammonia gas, reacting under the pressure condition, and purifying a product to obtain 2-amino-3-methyl
benzoic acid; and S3, diluting the 2-amino-3-methyl benzoic acid obtained in S3 with a
solvent 2, pumping the diluted 2-amino-3-methyl benzoic acid into a tubular reactor, introducing
liquid chlorine for reaction, and purifying the product to obtain the 2-amino-3-methyl-5-chlorobenzoic acid.
Ammonia gas is adopted as a nucleophilic
reagent to avoid
nitration reaction, so that the amount of acid
wastewater can be reduced from the source, hydrogenation reduction is not needed, and the
route atom
utilization rate is greatly increased.