Purification of N-substituted lactams

Details Purification of N-substituted lactams Purification of N-substituted lactams

2000-03-07

2001-03-27

McKane, Joseph K. (Department: 1626)

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

Organic compounds

Unsubstituted hydrocarbyl chain between the ring and the -c-...

C540S540000, C546S290000, C548S555000

Reexamination Certificate

active

06207824

ABSTRACT:

The present invention relates to a process for reducing the amine content of amine-contaminated N-substituted lactams.
N-Substituted lactams, for example N-methyl-2-pyrrolidone (NMP), are important as polar aprotic solvents, as synthetic building blocks and as selective extractants, e.g. for the extraction of aromatics from paraffinic hydrocarbons. Particularly for applications in the electronics industry (e.g. lithium ion batteries and photoresist strippers) and in the pharmaceutical industry, there is a need for highly pure N-substituted lactams.
GB-A-2 088 850 discloses a process for treating N-methyl-2-pyrrolidone (NMP) with basic anion exchangers in order to remove acidic or corrosive impurities in the NMP.
U.S. Pat. No. 4,831,160 relates to a process for reducing the concentration of acidic components in NMP in a plurality of steps, where the last step comprises treatment of the NMPs with basic anion exchangers.
DE-A-37 36 603 describes a process for purifying N-vinyl-2-pyrrolidone containing basic impurities of an unknown type by treating the crude N-vinyl-2-pyrrolidone with an acid cation exchanger. Since polymerization of N-vinyl-2-pyrrolidone can occur in the presence of strong acid cation exchangers, weak acid cation exchangers are preferred (—COOH groups as anchor groups).
U.S. Pat. No. 5,777,131 describes a process for improving the properties of N-substituted lactams by treating the lactams after their preparation with ion exchangers, preferably with strong acid cation exchangers of the brands Dowex® G23, Dowex® G26, Dowex® HCR-S and Dowex® HGR.
The Dowex® cation exchangers mentioned are exclusively gel-type styrene-divinylbenzene copolymers functionalized with sulfonic acid groups (—SO
3
H) as anchor groups (cf. Ullmann's Encyclopedia of Industrial Chemistry, Vol. A14, 5
th
ed., page 451). The term “gel-type” means that these cation exchangers have a natural porosity with a pore diameter of from about 1 to 3 nm (cf.: Ullmann's Encyclopedia of Industrial Chemistry, Vol. A14, 5
th
ed., page 395 and pages 399ff, Chapter 3.1 (1989)).
The improvement in the properties of the lactams in accordance with U.S. Pat. No. 5,777,131 constitutes, in the case of NMP, a reduction in the sodium content of about 100 ppb to less than 10 ppb, a reduction in the pH from about 11.5 to 7 and a reduction in the amine content from about 12 ppm to less than 1 ppm.
EP-A-878 454 discloses a process for reducing the content of metallic cations, e.g. alkali metal and alkaline earth metal cations, in organic, virtually water-free liquids such as NMP, isopropyl alcohol, monoethanolamine, dimethylacetamide, ethyl acetate, acetone and sulfolane by bringing the organic liquid into contact with a sulfonated resin based on a styrene-divinylbenzene copolymer in which the proportion of divinylbenzene is from 50 to 60% by weight of the total weight of the copolymer, if the sulfonic acid groups are disregarded.
It is an object of the present invention to find an economical, selective and efficient process for reducing the concentration of amines present as impurities in N-substituted lactams.
We have found that this object is achieved by a process for reducing the amine content of amine-contaminated N-substituted lactams, which comprises treating the contaminated N-substituted lactams with an acid macroporous cation exchanger.
The advantages of the process of the present invention are that these N-substituted lactams which, for example as a result of the method of preparing them, contain amines, e.g. primary amines of the formula RNH
2
, particularly primary C
1
-C
12
-alkylamines and C
1
-C
4
-monoalkanolamines, such as monomethylamine (MMA), ethylamine, n-propylamine, iso-propylamine, n-butylamine, cyclopentylamine, cyclohexylamine, n-decylamine, n-dodecylamine, monoethanolamine, in particular MMA, as impurities are purified with high selectivity and efficiency.
At the same time, the process of the present invention reduces the concentration of metal cations present in the N-substituted lactams as impurities, e.g. heavy metal ions such as Fe
3+
, Fe
2+
, cd
2+
, Co
2+
, Co
3+
, Cr
2+
, Cr
3+
, Cu
+
, Cu
2+
, Mn
2+
, Mn
3+
, Ni
2+
, Pb
2+
, Pb
4+
, Sn
2+
, Sn
4+
, Zn
2+
and Ti
4+
and alkali metal ions such as K
+
and, in particular, Na
+
and alkaline earth metal cations, such as Ca
2+
and Mg
2+
.
The process of the present invention makes possible a high total throughput through the macroporous cation exchanger (unit: [BV]; BV=bed volume=volume of the ion exchanger) and a high hourly throughput through the macroporous cation exchanger (unit: [BV/h]) together with a high capacity of the macroporous cation exchanger (unit: [mol of amine impurity to be removed/liters of ion exchanger]).
Preference is given to using strong acid macroporous cation exchangers, i.e. ones which have −SO
3
— groups (sulfonic acid groups) as anchor groups.
The acid macroporous cation exchangers are preferably organic macroporous cation exchangers, in particular ones which have a styrene-divinylbenzene copolymer matrix.
In the process of the present invention, the macroporous cation exchangers are used in their acid form (in the H form).
The pore diameter of the macropores in the cation exchangers used in the process of the present invention is generally from 10 to 150 nm and is thus significantly greater than the pore diameter of cation exchangers of the gel type, which have pore diameters of only about 1-3 nm.
The macropores of the cation exchangers used in the process of the present invention preferably have pore diameters of from 20 to 120 nm, particularly preferably from 20 to 100 nm, very particular preferably from 20 to 40 nm.
The significantly larger pores of the cation exchangers used in the process of the present invention result, for example, from the preparation of the styrene-divinylbenzene copolymers being carried out in the presence of nonpolymerizable compounds such as heptane, saturated fatty acids, C
4
-C
10
-alcohols or polyalcohols or linear polystyrene having a low molecular weight. (Cf.: Ullmann's Encyclopedia of Industrial Chemistry, Vol. A14, 5
th
Ed., page 395 and pages 399ff, Chapter 3.1 (1989)).
The macroporous cation exchangers used in the process of the present invention generally have a utilizable capacity of at least 0.5 mol, in particular at least 0.8 mol, very particularly preferably at least 1 mol, of amines present as impurities per liter of cation exchanger.
The macroporous cation exchangers used in the process of the present invention can be produced by known methods (cf. Ullmann's Encyclopedia of Industrial Chemistry, Vol. A14, 5
th
Ed., page 399, last paragraph, and page 400) and are commercially available.
Examples of macroporous cation exchangers in the H form which can be used in the process of the present invention are:
Duolite® C264; Amberlite® 252, UP252 and 200; Imac® C16P; Lewatit® SP112 and K2621; Dowex® 88 and MSC1; Kastel® C300P; Ionac® CFP110; Relite® CFS and CFZ; Diaion® PK 220 and PK 228; Purolite C150, CT165 and CT175; Wofatit® KS10.
Preference is given to using Duolite® C264, Amberlite® 252 and Amberlite® UP252.
The process of the present invention is, in particular, employed for the purification of N-substituted lactams of the formula I
where R is
a linear or branched saturated aliphatic radical, preferably C
1
-C
12
-alkyl, such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, n-pentyl, iso-pentyl, sec-pentyl, neo-pentyl, 1,2-dimethylpropyl, n-hexyl, iso-hexyl, sec-hexyl, cyclopentylmethyl, n-heptyl, iso-heptyl, cyclohexylmethyl, n-octyl, 2-ethylhexyl, n-nonyl, iso-nonyl, n-decyl, iso-decyl, n-undecyl, n-dodecyl, iso-dodecyl,
particularly preferably C
1
-C
8
-alkyl such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, n-pentyl and 2-ethylhexyl,
very particularly preferably C
1
-C
4
-alkyl such as methyl, ethyl, n-propy

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