Method of preparing amino-, imino- and nitrilocarbonxylic acids and silver-promoted copper catalyst for use in said method

摘要

A method is described for preparing amino-, imino-, and nitrilocarboxylic acids of formula        R1R2R3N ,     (I)and alkaline salts of these, here R1, R2, and R3, which may be the same or different, represent: ydrogen, n alkyl group having 1-10 C atoms, carboxyalkyl group having 1-10 C atoms [in the alkyl moiety], n aminoalkyl group having 1-10 C atoms [in the alkyl moiety], carboxycycloalkyl group having 3-6 C atoms [in the cycloalkyl moiety], a cycloalkyl-alkyl group having 3-6 C atoms in the cycloalkyl moiety and 1-10 C atoms in the alkyl moiety and having a carboxy group substituent, or an alkyl-cycloalkyl group having 1-10 C atoms in the alkyl moiety and 3-6 C atoms in the cycloalkyl moiety and having a carboxy group substituent; wherewith said alkyl groups may be linear or branched; and wherewith at least one of the groups R does not represent hydrogen; the method comprising:(a) subjecting alkanolamines of formula        R1'R2'R3' N,     (II)wherein the groups R' have the same significations as set forth above for the groups R, except that the aforesaid carboxy groups are hydroxyl groups,to an oxidative dehydrogenation reaction in aqueous alkaline medium in the presence of a copper catalyst of the Raney type promoted with 50-5000 ppm silver;(b) separating the resulting carboxylate salts from the reaction medium, and (optionally) purifying said salts or converting them to the corresponding amino acids by precipitation in acid medium;(c) separating the catalyst from the reaction medium, washing said catalyst with demineralized water, and (optionally) recycling the catalyst to re-use in step (a) [(of the same or another production run)]; and(d) recovering and collecting the hydrogen liberated in the reaction.;Also described is a catalyst for use in the described method. The catalyst is comprised of a Raney-type catalyst comprised of copper promoted with 50-5000 ppm silver supplied as follows:-- incorporated in an alloy;-- deposited on [the] surface from salts of silver; or-- in a physical mixture comprising finely divided metallic silver.;The compounds of formula (I) have been found to be important synthesis intermediaries, e.g. in preparation of N-phosphonomethylglycine (the herbicidal agent known as glyphosate).