Manufacture of glyphosate salts

Details Manufacture of glyphosate salts Manufacture of glyphosate salts

1998-05-08

1999-09-14

Geist, Gary

Organic compounds -- part of the class 532-570 series

Organic compounds

Sulfonic acids or salts thereof

568 17, C07F 928, C07F 938

Patent

active

059525258

DESCRIPTION:

BRIEF SUMMARY
This invention relates to the manufacture of glyphosate salts, and in particular to the manufacture of the trimethylsulfonium salt of glyphosate, to the manufacture of trimethylsulfonium intermediates and to novel trimethylsulfonium intermediates.
U.S. Pat. No. 4,431,594 describes a process for the preparation of organic salts of N-phosphonomethylglycine which comprises reacting N-phosphonomethylglycine with a compound of formula R1R2R3S+=ZX-(a) wherein R1, R2 and R3 are the same or different and are alkyl groups having from 1 to 4 carbon atoms or aromatic alkyl groups, X is chloride, bromide or iodide and Z is an electron pair or oxygen, in the presence of a trialkylarmine and isolating the product by phase separation between water and a polar functional solvent which is immiscible with water. Preferred compounds of formula (a) include trimethylsulfonium chloride and preferred trialkylamines include ALAMINE 336 (ALAMINE is a trade mark of Henkel Co.). Whilst this process is very effective for use on a major manufacturing site having plant capable of handling the relatively complex stages required for the recycle and regeneration of the amine, there is a need for a process in which the trimethylsulfonium salt of N-phosphonomethylglycine is manufactured from the parent acid N-phosphonomethylglycine using relatively unsophisticated plant.
In European Patent Application No 0639198 there is described a process for the preparation of a salt such as a trimethylsulfonium salt of N-phosphonomethylglycine in which the parent acid N-phosphonomethylglycine is reacted with trimethylsulfonium hydrogen sulfate in the presence of a base. In a preferred embodiment, ammonium hydroxide is used as base to form a product which contains both the trimethylsulfonium salt of N-phosphonomethylglycine and ammonium sulfate. Whilst this process is highly efficient for the manufacture of formulations in which ammonium sulfate is a required additive, ammonium sulfate is not necessarily a desired component of all formulations of the the trimethylsulfonium salt of N-phosphonomethylglycine.
We have now found that the use of trimethylsulfonium carbonate or trimethylsulfonium bicarbonate as starting material for the manufacture of the trimethylsulfonium salt of N-phosphonomethylglycine provides a process which produces the desired product in excellent yield and at high concentration and which is capable of being operated under ambient conditions in relatively unsophisticated plant and with minimal effluent control requirements.
According to the present invention there is provided a process for the manufacture of the trimethylsulfonium salt of N-phosphonomethylglycine which comprises reacting N-phosphonomethylglycine with an aqueous solution of trimethylsulfonium carbonate or trimethylsulfonium bicarbonate or a mixture thereof.
The reaction of N-phosphonomethylglycine with trimethylsulfonium carbonate requires two moles of N-phosphonomethylglycine per mole of trimethylsulfonium carbonate and produces two moles of the trimethylsulfonium salt of N-phosphonomethylglycine. Substantially stoichiometric proportions are conveniently used. A slight excess of either component, for example up to 5% excess of trimethylsulfonium carbonate per mole of N-phosphonomethylglycine may be used if desired.
The reaction of N-phosphonomethylglycine with trimethylsulfonium bicarbonate requires one mole of N-phosphonomethylglycine per mole of trimethylsulfonium bicarbonate and produces one mole of the trimethylsulfonium salt of N-phosphonomethylglycine. Substantially stoichiometric proportions are conveniently used. A slight excess of either component, for example up to 5% excess may be used if desired.
Whether trimethylsulfonium carbonate or bicarbonate or a mixture thereof is used as starting material, the only product other than the trimethylsulfonium salt of N-phosphonomethylglycine is carbon dioxide which is readily vented to atmosphere and requires no sophisticated effluent control procedures.
An aqueous solution of N-phosphonomethylglycine may be used if des

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CA:114:247527 abs of BR8806046, Jun. 1990.

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