The invention relates to an improved production method of N-phosphonomethyl
glycine, in which a carbon catalyst is filled in a multi-stage
fixed bed reactor; phosphonomethyl
iminodiacetic acid slurry with the concentration in percentage by weight of 2-10% is used as a feed liquid to be mixed and heated firstly, then is sent into the
fixed bed reactor after being pumped and metered, and is fully contacted with
oxygen-containing gas which is supplied into the
fixed bed reactor via a gas
distributor so as to carry out
catalytic oxidation reaction to continuously oxidize the phosphonomethy liminodiacetic acid into
glyphosate; and the multi-stage fixed
bed reactor is an isothermal
reaction system formed by a plurality of stages of reactors connected in series, the top of each stage of reactor is provided with the feed liquid and the gas
distributor, and the temperature of each stage of reactor is provided by heating or cooling media. A reaction pressure of 0-1.5 MPa and a
reaction temperature of 30-180 DEG C are maintained in each stage of fixed
bed reactor, and gas, liquid and
solid in the reactor are fully contacted to carry out oxidizing reaction to obtain
glyphosate feed liquid. The invention has the advantages of finding a multi-stage series isothermal reactor mode which has more uniform
retention time than the existing fixed
bed reactor and avoids excessive oxidation, and provides an application process which can keep ideal yield of
glyphosate after being amplified.