Continuous Method For Producing Fatty Acid Alkanol Amides
The invention relates to a continuous method for producing fatty acid alkanol amides, wherein at least one fatty acid of the formula (I) R 3 —COOH (I) where R 3 is an optionally substituted aliphatic hydrocarbon radical with 5 to 50 carbon atoms, having at least one alkanol amine of the formula (II) HNR 1 R 2 (II) where R 1 is a hydrocarbon radical carrying at least one hydroxyl group and having 1 to 50 carbon atoms and R 2 is hydrogen, R 1 or a hydrocarbon radical having 1 to 50 carbon atoms, is reacted into an ammonia salt, and said ammonia salt is subsequently reacted in a reaction tube, the longitudinal axis thereof being disposed in the propagation direction of the microwaves of a monomode microwave applicator, under the action of microwave radiation into fatty acid alkanol amide.
1 . A continuous process for preparing fatty acid alkanolamides by reacting at least one fatty acid of the formula I
R 3 —COOH (I)
in which R 3 is an optionally substituted aliphatic hydrocarbon radical having 5 to 50 carbon atoms
with at least one alkanolamine of the formula II
HNR 1 R 2 (II)
in which
R 1 is a hydrocarbon radical bearing at least one hydroxyl group and having 1 to 50 carbon atoms and
R 2 is hydrogen, R 1 or a hydrocarbon radical having 1 to 50 carbon atoms to give an ammonium salt and then converting this ammonium salt to the fatty acid alkanolamide under microwave irradiation in a reaction tube whose longitudinal axis is in the direction of propagation of the microwaves from a monomode microwave applicator.
2 . The process as claimed in claim 1 , in which the salt is irradiated with microwaves in a substantially microwave-transparent reaction tube within a hollow conductor connected via waveguides to a microwave generator.
3 . The process as claimed in one or more of claims 1 and 2 , in which the microwave applicator is configured as a cavity resonator.
4 . The process as claimed in one or more of claims 1 to 3 , in which the microwave applicator is configured as a cavity resonator of the reflection type.
5 . The process as claimed in one or more of claims 1 to 4 , in which the reaction tube is aligned axially with a central axis of symmetry of the hollow conductor.
6 . The process as claimed in one or more of claims 1 to 5 , in which the salt is irradiated in a cavity resonator with a coaxial transition of the microwaves.
7 . The process as claimed in one or more of claims 1 to 6 , in which the cavity resonator is operated in E 01n mode where n is an integer from 1 to 200.
8 . The process as claimed in one or more of claims 1 to 7 , in which R 3 is an unsubstituted alkyl radical having 5 to 50 carbon atoms.
9 . The process as claimed in one or more of claims 1 to 7 , in which R 3 is a hydrocarbon radical which has 5 to 50 carbon atoms and bears one or more substituents selected from halogen atoms, halogenated alkyl radicals, C 1 -C 5 -alkoxy, poly(C 1 -C 5 -alkoxy), poly(C 1 -C 5 -alkoxy)alkyl, carboxyl, ester, amide, cyano, nitrile, nitro, sulfo and aryl groups having 5 to 20 carbon atoms, where the C 5 -C 20 -aryl groups may bear substituents selected from halogen atoms, halogenated alkyl radicals, C 1 -C 20 -alkyl, C 2 -C 20 -alkenyl, C 1 -C 5 -alkoxy, ester, amide, cyano, nitrile and nitro groups.
10 . The process as claimed in one or more of claims 1 to 9 , in which R 3 comprises 5 to 30 carbon atoms.
11 . The process as claimed in one or more of claims 1 to 10 , in which R 3 comprises one or more double bonds.
12 . The process as claimed in one or more of claims 1 to 11 , in which R 1 bears 2 to 20 carbon atoms.
13 . The process as claimed in one or more of claims 1 to 12 , in which R 1 is a group of the formula III
—(B—O) m —H (III)
in which
B is an alkylene radical having 2 to 10 carbon atoms and
m is from 1 to 500.
14 . The process as claimed in one or more of claims 1 to 13 , in which R 2 is C 1 -C 30 -alkyl, C 2 -C 30 -alkenyl, C 5 -C 12 -cycloalkyl, C 6 -C 12 -aryl, C 7 -C 30 -aralkyl or a heteroaromatic group having 5 to 12 ring members.
15 . The process as claimed in one or more of claims 1 to 13 , in which R 2 is a group of the formula IV
—(B—O) m —R 5 (IV)
in which
B is an alkylene radical having 2 to 10 carbon atoms,
m is from 1 to 500, and
R 5 is a hydrocarbon radical having 1 to 24 carbon atoms.
16 . The process as claimed in one or more of claims 1 to 13 , in which R 2 is hydrogen.
17 . The process as claimed in one or more of claims 1 to 15 , in which R 2 represents alkyl radicals having 1 to 20 carbon atoms or alkenyl radicals having 2 to 20 carbon atoms.
18 . The process as claimed in one or more of claims 1 to 17 , in which the microwave irradiation is performed at temperatures between 150 and 500° C.
19 . The process as claimed in one or more of claims 1 to 18 , in which the microwave irradiation is performed at pressures above atmospheric pressure.
20 . A fatty acid alkanolamide with a content of amino esters and ester amides of less than 5 mol %, prepared by reaction of at least one fatty acid of the formula I
R 3 —COOH (I)
in which R 3 is an optionally substituted aliphatic hydrocarbon radical having 4 to 50 carbon atoms
with at least one alkanolamine of the formula
HNR 1 R 2 (II)
in which
R 1 is a hydrocarbon radical bearing at least one hydroxyl group and having 1 to 50 carbon atoms and
R 2 is hydrogen, R 1 or a hydrocarbon radical having 1 to 50 carbon atoms to give an ammonium salt, and then converting this ammonium salt to the fatty acid alkanolamide with microwave irradiation in a reaction tube, the longitudinal axis of which is in the direction of propagation of the microwaves from a monomode microwave applicator.