Method for preparation of N-phosphonomethylglycine.

摘要

An improved method of preparing N-phosphonomethylglycine in yields over 80 percent comprising: (a) hydrolyzing a phosphonate of the formula <CHEM> wherein in R, R<1> and R<2> are C1-C4 alkyl at a temperature between about 55 DEG C to reflux temperature water in an amount sufficient to provide a mole ratio of water to phosphonate within a range of abut 10:1 to about 60:1 and HCl in an amount sufficient to provide a mole ratio of HCl to phosphonate within a range of about 2:1 to about 4:1 or higher to yield an acidic aqueous solution of N-phosphonomethylglycine; (b) removing volatile phosphonate from the acidic aqueous solution of N-phosphonomethylglycine either during or after the hydrolyzing step; (c) precipitating N-phosphonomethylglycine from the acidic solution of N-phosphonomethylglycine by: (1) cooling said solution to below about 80 DEG C; (2) raising the pH of the said solution to within a range of about 1.0 to about 1:8; (3) seeding the solution with 2-4 ppm solid N-phosphonomethylglycine with agitation; and (4) further cooling said solution to about 25 DEG C and continuing agitation and cooled for about 1.5 hours; (d) recovering the precipitated N-phosphonomethylglycine from its mother liquor; and (e) washing the recovered N-phosphonomethylglycine with water to remove impurities and ammonium chloride.