| 摘要 |
1. A process for the preparation of N-phosphonomethylglycine, wherein N-phosphonomethyliminodiacetic acid N-oxide is brought into contact with a catalytically active quantity of at least one catalyst, selected from amongst a thionyl halide, ammonium dithionite or an alkali metal dithionite, a dialkyl sulfite, sulfur dichloride, sulfur dioxide and sulfurous acid, in a reaction chamber by metering the N-phosphonomethyliminodiacetic acid N-oxide into the reaction chamber in such a way that always at least 50% of the N-oxide metered into the reaction chamber are converted. 2. A process as claimed in claim 1, wherein the catalyst used is sulfur dioxide, sulfurous acid, thionyl chloride, a dialkyl sulfite or an alkali metal dithionite. 3. A process as claimed in claim 1 or 2, wherein a cocatalyst is additionally employed. 4. A process as claimed in claim 3, wherein the cocatalyst employed is a water-soluble molybdenum compound, in particular ammonium molybdate or an alkali metal molybdate. 5. A process as claimed in any of the preceding claims, wherein the N-oxide is metered into an aqueous solution of the catalyst. 6. A process as claimed in any of claims 1 to 4, wherein the N-oxide and the catalyst are metered into the reaction chamber simultaneously and separately. 7. A process as claimed in any of the preceding claims, wherein the N-phosphonomethyliminodiacetic acid N-oxide is metered in such a way that always at least 70% of the N-oxide metered into the reaction chamber are converted. 8. A process as claimed in any of the preceding claims, wherein the N-phosphonomethyliminodiacetic acid N-oxide is prepared by oxidizing N-phosphonomethyliminodiacetic acid. 9. A process as claimed in claim 8, wherein the oxidation is performed with a peroxide compound. 10. A process as claimed in claim 9, wherein the oxidation is performed in the presence of an oxidation catalyst, in particular a water-soluble molybdenum compound. 11. A process as claimed in claim 10, wherein the same catalyst is used as catalyst for oxidizing the N-phosphonomethyl-iminodiacetic acid and as cocatalyst for converting the N-oxide. 12. A process as claimed in any of the preceding claims, wherein N-phosphonomethyliminodiacetic acid is oxidized with a peroxide compound in the presence of a catalytically effective quantity of a water-soluble molybdenum compound to give N-phosphonomethyliminodiacetic acid N-oxide and the reaction mixture is subsequently brought into contact with the catalyst by metering it into the reaction chamber.
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