PREPARATION OF N-PHOSPHONOMETHYLGLYCIN BY OXIDATION OF N-PHOSPHONOMETHYLIMINODIACETIC ACID

PCT No. PCT/ES91/00013 Sec. 371 Date Dec. 18, 1991 Sec. 102(e) Date Dec. 18, 1991 PCT Filed Mar. 12, 1991 PCT Pub. No. WO91/13893 PCT Pub. Date Sep. 19, 1991.Improvements to a method for preparing N-phosphonomethylglycyne by oxidation of N-phosphonomethyliminodiacetic acid. N-phosphonomethylglycine may be obtained by oxidation of N-phosphonomethyliminodiacetic acid with O2 or with an oxygen-containing gas, in the presence of a noble metal catalyst on activated carbon. To avoid the catalyst losses, the improvements of the invention consist in a pressure scavaging with N2, after completion of the oxidation reaction. Owing to such treatment, the catalyst losses are reduced from 30% to 1%, making the processing economically viable on a large industrial scale. The recovered catalyst holds its catalytic activity and may be reused at least 20 consecutive times. N-phosphonomethylglycine is a herbicide of extended application.