Patent ID: 7294733

Claim:
A method for producing N-(phosphonomethyl) glycine, a salt or ester thereof, the method comprising contacting formaldehyde, phosphorous acid and an amine, or a salt thereof, having the formula (III): wherein R 4 and R 5 are independently selected from the group consisting of H, —CH 2 PO(OR 6 )(OR 7 ), hydrocarbyl, substituted hydrocarbyl, and heterocycle; and R 6 and R 7 are independently selected from the group consisting of H, hydrocarbyl, substituted hydrocarbyl, heterocycle, and a salt-forming cation; to produce a phosphonomethylation reaction product mixture containing an aminomethylphosphonic acid substrate, or a salt thereof, having the formula (II): wherein R 1 and R 2 are independently selected from the group consisting of H, hydrocarbyl, substituted hydrocarbyl, heterocycle, and a salt forming cation; and R 4 and R 5 are as defined above; contacting said aminomethylphosphonic acid substrate, or a salt thereof, having the formula (II), water and an oxidizing gas in the presence of a catalyst to form a formylphosphonic acid reaction product mixture containing formylphosphonic acid or a salt thereof and formic acid, and controlling the conditions under which said contacting is conducted so that (a) at least about 75% of the aminomethylphosphonic acid substrate is converted to formylphosphonic acid, or a salt thereof, (b) the molar ratio of formylphosphonic acid, or salt thereof, to formic acid is at least about 2:1 in said formylphosphonic acid reaction product mixture, and (c) no more than 50% of the formylphosphonic acid, or salt thereof formed in the formylphosphonic acid reaction product mixture is consumed therein; and contacting said formylphosphonic acid with glycine in the presence of a reducing agent to produce a reductive alkylation reaction product mixture containing N-(phosphonomethyl) glycine, or a salt thereof.