Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
2001-03-07
2001-11-27
Richter, Johann (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C564S498000
Reexamination Certificate
active
06323371
ABSTRACT:
The present invention relates to a process for the preparation of alkanolamines having improved color quality.
Important fields of use of alkanolamines, such as, for example, triethanolamine (TEA), or secondary products thereof, are, for example, soaps, cleansers and shampoos in the cosmetics industry, and also dispersants and emulsifiers.
For these and other fields of use, water-clear, colorless alkanolamines having as little discoloration as possible, e.g. measured as APHA or Gardner color number, which retain these properties even over relatively long storage periods (of, for example, 6, 12 or more months) are desired.
A known problem is that a pure alkanolamine obtained following fractional distillation of an alkanolamine crude product which has been obtained, for example, by reacting ammonia with ethylene oxide or propylene oxide has a yellowish to brownish discoloration (color number e.g. about 10 to 500 APHA in accordance with DIN ISO 6271(=Hazen)). This discoloration arises particularly in processes involving high temperatures.
During storage of the alkanolamine, including in sealed packs or with the exclusion of light, this discoloration is further intensified. (See e.g.: T. I. MacMillan, Ethylene Oxide Derivatives, Report No. 193, chapter 6, pages 6-5 and 6-9 to 6-13, 1991, SRI International, Menlo Park, Calif. 94025; G. G. Smirnova et al., J. of Applied Chemistry of the USSR 61, pp. 1508-9 (1988), and Chemical & Engineering News, Sep. 16, 1996, page 42, middle column).
A number of processes for the preparation of alkanolamines having improved color quality are described in the literature.
EP-A-36 152 and EP-A-4015 describe the effect of the materials used in processes for the preparation of alkanolamines on the color quality of the process products and recommend nickel-free or low-nickel steels.
U.S. Pat. No. 3,207,790 describes a process for improving the color quality of alkanolamines by the addition of a borohydride of an alkali metal to the alkanolamine.
However, the presence of an auxiliary (stabilizer) for improving the color quality of alkanolamines is undesirable in many important areas of application.
The earlier German Application No. 19942300.8 from 04.09.99 relates to a process for the preparation of alkanolamines having improved color quality by treating the alkanolamine with hydrogen in the presence of a hydrogenation catalyst at elevated temperature.
JP-A-04 29 0850 (Derwent Abstract No. 92-393250/48; Chem. Abstr. 118: 101513e) describes the decoloration of triethylenetetramine by heating in the presence of phosphorous acid and water.
JP-A-49 07 6804 (Derwent Abstract No. 76608V 44; Chem. Abstr. 82:3766h) relates to the purification of ethyleneamines, such as triethylenetetramine or pentaethylenehexamine by distillation in the presence of esters of phosphorous acid.
EP-A-4015 describes how mono-, di- and triethanolamine having reduced discoloration are obtained by the addition of phosphorous or hypophosphorous acid or derivatives thereof before, during or directly after the stepwise reaction of ethylene oxide with ammonia and subsequent isolation by distillation. Page 2, lines 14 to 18 teach that it is not possible to decolorize to a satisfactory degree ethanolamines which already have a greater or lesser degree of discoloration by a distillation carried out in the presence of phosphorous acid. EP-A-4015 teaches that it is instead necessary for the phosphorous or hypophosphorous acid to be present during the preparation of the ethanolamine or at least be added to the crude reaction mixture comprising the ethanolamines, water and ammonia directly after the reaction (cf. the examples and the patent claim).
The earlier German Application No. 19855383.8 from 01.12.98 relates to a process for the purification of TEA prepared by reacting aqueous ammonia with ethylene oxide in liquid phase under pressure and at elevated temperature by separating off excess ammonia, water and monoethanolamine from the reaction product, reacting the resulting crude product with ethylene oxide at temperatures of from 110 to 180° C., and then rectifying the mixture in the presence of phosphorous or hypophosphorous acid or compounds thereof.
It is an object of the present invention to find an economic, selective, efficient and technically noncomplex process for the preparation of alkanolamines having improved color quality. The process should, by overcoming the disadvantages of the prior art, permit the discoloration of alkanolamines (such as, for example, triethanolamine or aminoethylethanolamine), e.g. measured as APHA color number, to be reduced and the color stability to be improved (undesired increase in color number over the storage period).
We have found that this object is achieved by a process for the preparation of alkanolamines having improved color quality, which comprises treating the alkanolamine with an effective amount of phosphorous acid or hypophosphorous acid or compounds thereof initially at elevated temperature over a period of at least 5 min (step a), and then distilling it in the presence of an effective amount of one of these phosphorus compounds (step b).
The alkanolamine used in the process according to the invention, preferably ethanolamine or propanolamine, can be obtained by known processes, e.g. by the reaction of ammonia or of a primary or secondary amine with ethylene oxide or propylene oxide (e.g. as in EP-A-673 920), by the 1,4-addition of ammonia or of a primary or secondary amine to an &agr;,&bgr;-unsaturated aldehyde (e.g. acrolein) and subsequent reduction (e.g. hydrogenation), by the 1,4-addition of ammonia or of a primary or secondary amine to an &agr;,&bgr;-unsaturated acid (e.g. acrylic acid) or an &agr;,&bgr;-unsaturated ester (e.g. acrylic ester) and subsequent reduction (e.g. hydrogenation), by the 1,4-addition of water to an &agr;,&bgr;-unsaturated nitrile (e.g. acrylonitrile) and subsequent reduction (e.g. hydrogenation), amination of corresponding primary or secondary alcohols, or aminating hydrogenation of corresponding hydroxyaldehydes or hydroxyketones.
N-(2-Aminoethyl)ethanolamine (AEEA) can be obtained by the reaction of monoethanolamine or ammonia with ethylene oxide in the presence of hydrogen and a hydrogenating, dehydrogenating or aminating catalyst.
The purity of the alkanolamines used in the process according to the invention, preferably ethanolamines or propanolamines, is generally greater than 70% by weight, in particular greater than 80% by weight. As well as distilled or undistilled crude alkanolamines, which can also be removed directly in crude form from the corresponding precursors from a plant for the preparation of the alkanolamine, it is also possible to use distilled alkanolamines having a purity of greater than 90% by weight, particularly ≧97% by weight, in particular ≧98% by weight, very particularly ≧99% by weight.
It is also possible to use mixtures of alkanolamines, in which case the purities given above are based on each alkanolamine of this mixture, or solutions of alkanolamines in an inert solvent, such as, for example, alcohols (methanol, ethanol, isopropanol, n-propanol, n-butanol, 2-ethylhexanol), ethers (tetrahydrofuran, 1,4-dioxane), hydrocarbons (benzene, pentane, petroleum ether, toluene, xylene, hexane, heptane, Mihagol) and water.
The APHA color number of the alkanolamines used (based on the non-acid-treated alkanolamine) is generally ≦100, in particular ≦50, for example ≦20.
The alkanolamines which are preferably used in the process according to the invention are ethanolamines and propanolamines such as, for example, monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), O,N,N-tris(2-hydroxyethyl)ethanolamine, N-(2-aminoethyl)ethanolamine (AEEA), N-(2-hydroxyethyl)piperazine, N-(2-hydroxyethyl)morpholine, N,N′-bis(2-hydroxyethyl)piperazine, monoisopropanolamine, diisopropanolamine, triisopropanolamine and 1,3-propanolamine, particularly preferably the ethanolamines MEA, DEA, TEA and AEEA.
The process according to the invention can be carried out as
Buskens Philip
Gutschoven Frank
Melder Johann-Peter
Ross Karl-Heinz
Ruider Gunther
BASF - Aktiengesellschaft
Davis Brian J.
Keil & Weinkauf
Richter Johann
LandOfFree
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