Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
2000-04-03
2002-07-02
Vollano, Jean F. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C562S523000
Reexamination Certificate
active
06414188
ABSTRACT:
SUMMARY OF THE INVENTION
A method is described for preparing amino-, imino-, and nitrilocarboxylic acids, and their alkali metal salts, starting from alkanolamines. The method employs oxidative dehydrogenation of the alkanolamine(s) in an alkali metal hydroxide medium, using a copper catalyst containing silver.
The subject amino-, imino-, and nitrilocarboxylic acids have the following formula:
R1R2R3N (I)
where R3 is an alkyl group having 1-10 C atoms substituted with a carboxyl group (—COOH),
R1 and R2, which may be the same or different, represent:
hydrogen,
an alkyl group having 1-10 C atoms,
an alkyl group having 1-10 C atoms substituted with a carboxyl group,
a cycloalkyl group having 3-6 C atoms substituted with a carboxyl group,
a cycloalkyl-alkyl group having 3-6 C atoms in the cycloalkyl moiety and 1-10 atoms in the alkyl moiety and substituted with a carboxyl group,
or an alkyl-cycloalkyl group having 1-10 atoms in the alkyl moiety and 3-6 atoms in the cycloalkyl moiety and substituted with a carboxyl group;
wherewith said alkyl groups may be linear or branched,
The described method comprises the following:
(a) Subjecting alkanolamines of formula
R1′R2′R3′N (II)
wherein the R′ groups have the same substituents as set forth above for the R groups, except that the aforesaid carboxyl groups (—COOH) are —CH2OH groups, to an oxidative dehydrogenation reaction in aqueous
alkali metal hydroxide medium in the presence of a copper catalyst containing 50-5000 ppm of silver as a promoter;
(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.
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). In our invention, the copper catalyst containing silver as a promoter (e.g. via silver salts), has the advantage that reactivation with each re-use of the catalyst is not required. If a copper catalyst without silver is used, or if a copper catalyst containing a metal or metals other than silver e.g., chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, manganese, zirconium, cobalt, or mixtures of these is used, the catalyst activity fades rapidly with successive reactions.
For the better part of 200 years, it has been known to convert alcohols to alkali metal salts of the corresponding carboxylic acids by heating the alcohols with alkali metal hydroxides (Dumas, 1840, 35 Ann. 129-73).
The reaction has been extended to aminoalcohols; when these are heated in the presence of an alkali metal compound they undergo oxidative dehydrogenation to yield the alkali metal salt of the corresponding amino- or iminoacid; this occurs even without a catalyst (U.S. Pat. No. 2,384,816, preparation of glycine in low yield from diethanolamine and KOH). Known catalysts for use with this reaction include, e.g., cadmium oxide, zinc oxide, palladium, platinum, and activated copper. Hydrogen is liberated. Oxygen or a gas containing oxygen may be introduced to form water from the hydrogen and thereby avoid hazardous accumulations of hydrogen.
DESCRIPTION OF THE RELATED ART
Examples from the Patent Literature:
U.S. Pat. No. 2,384,817 (1945), preparation of glycine from monoethanolamine (MEA) and potassium hydroxide at elevated temperature, in an anhydrous medium, with an activated copper catalyst (low yield);
U.S. Pat. No. 3,842,081 (1974), preparation of iminodiacetic acid (IDA) from diethanolamine (DEA) and potassium hydroxide, with a cadmium oxide catalyst (good yield, but cadmium is deemed a toxic substance);
U.S. Pat. No. 3,578,709 (1971), preparation of nitrilotriacetic acid (NTA) from triethanolamine (TEA) and an alkali metal hydroxide, with a zinc oxide catalyst (low yield);
Jap. Pat. 53/7709, preparation of IDA and NTA from DEA and TEA, respectively, in a sodium oxide medium, with a catalyst comprised of Pd or Pt supported on carbon, with injection of oxygen or a gas containing oxygen (low yields, on the order of 70%, and costly precious metal catalysts used to produce a product of relatively low net value);
U.S. Pat. No. 4,782,183, preparation of glycine, IDA, and NTA, from MEA, DEA, and TEA, respectively, and a hydroxide of an [alkaline] alkali metal in aqueous medium, with an activated copper catalyst, at pressures up to 980 kPa (conversion very good), as in the preceding examples, hydrogen liberated in the amount of 2 hydrogen atoms per acetic group, and the further disadvantage pertains that the copper cannot be re-used but must be replaced by fresh copper for each synthesis run, because it becomes depleted (poisoned) in a single use;
U.S. Pat. No. 5,367,112 (1994), preparation of glycine, IDA, and NTA, from MEA, DEA, and TEA, respectively, under the same conditions as in the above-cited patent, but wherewith the activated copper catalyst is promoted with 50-10,000 ppm of an element selected from the group comprising chromium, titanium, niobium, tantalum, tungsten, zirconium, vanadium, molybdenum, manganese, cobalt, nickel, or a mixture of these, the concentration of the catalyst being very high, viz. double that used according to U.S. Pat. No. 4,782,183;
U.S. Pat. No. 5,225,592 (1993), preparation of glycine, IDA, and NTA, from the corresponding alkanolamines and sodium hydroxide, with a copper catalyst, all in aqueous medium and with injection of oxygen or an oxygen-containing gas to avoid emission of hydrogen, the avoidance being achieved viz. by formation of water with the oxygen. Pressure of the system maintained at values up to 11,765 kPa. Drawback again that a new catalyst must be used for each synthesis run;
(PTO Pat. App.) WO 92/06069, regeneration of activated copper used as a catalyst in synthesis of acetic acid derivatives, e.g. preparation of glycine, IDA, and NTA via oxidative dehydrogenation of MEA, DEA, and TEA, respectively. The regeneration is needed because the catalyst loses substantial activity, wherewith in practice absent regeneration it cannot be used more than once and therefore is not economical for industrial applications. In the regeneration, after each synthesis run the copper is treated in an aqueous solution of formaldehyde. A drawback is that effluents resulting from formaldehyde solutions are bactericidal, which creates a disposal problem, not necessary with our invention.
DETAILED DESCRIPTION OF THE INVENTION
As mentioned above, the above-described copper catalysts, possibly promoted with chromium, molybdenum, titanium, niobium, tantalum, vanadium, zirconium, manganese, tungsten, cobalt, nickel, or with mixtures of these, all experience an appreciable loss of activity with successive uses after the first synthesis run, necessitating re-activation. The loss of activity is attributable to formation of cuprous and cupric oxides on the surface of the copper particles.
It was discovered, in connection with the present invention, that the herein described incorporation of silver in the copper catalyst will greatly increase the catalyst yield as well as substantially increasing the number of synthesis runs for which the catalyst can be used and re-used. Moreover, savings in catalyst used of up to 50 % can be achieved in comparison to the amounts needed according to the above-described prior art patents. The effect is believed to be due to electrochemical protection of the copper by the silver, which reduces or prevents oxidation of the copper. This protective effect, which can be observed by the naked eye as a simple color change if the catalyst is used without a promoter, in comparison to no color change in the promoted catalyst, was clearly established by examina
Ruiz Marta Del Carmen
Vigil Jorge Gustavo
Atanor S.A.
Jacobson & Holman PLLC
Vollano Jean F.
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