Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Utility Patent
1999-03-12
2001-01-02
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C564S477000
Utility Patent
active
06169207
ABSTRACT:
This invention relates to a process for selectively producing dialkanolamines, through amination of alkylene oxides with ammonia.
As a method of producing alkanolamines through amination of alkylene oxides with ammonia, industrial production of ethanolamines through the reaction of ethylene oxide with aqueous ammonia (ammonia concentration=20-40 percent by weight) is being practiced. In this method three kinds of ethanolamines, i.e., monoethanolamine, diethanolamine and triethanolamine are formed. Whereas, demand for triethanolamine is decreasing, and it is desirable to inhibit formation of triethanolamine. For this purpose, the reaction is conducted using a large excess of ammonia, such as at the molar ratio of ammonia to ethylene oxide of 3-5, but still the selectivity for triethanolamine ranges 10-20 percent by weight or even higher, and that for diethanolamine is not more than 40 percent by weight.
Whereas, alkylene oxide hardly react with ammonia in a water-free system and hence presence of a catalyst is essential for this type of reaction. As the catalyst, for example, those of a homogeneous system such as of organic acids, inorganic acids or ammonium salts have been proposed (cf. Swedish Patent No. 158167). Those homogeneous system catalysts, however, have the problem that their separation from the reaction system is difficult, and their performance is insufficient.
As an attempt to immobilize these homogeneous system acid catalysts, an ion-exchange resin formed by immobilizing sulfonic acid groups on the resin has been proposed (cf. JP KOKOKU Sho 49(1974)-47728). This catalyst exhibits relatively high activity and selectivity, and is being put to industrial practice. The ion-exchange resin, however, is subject to a problem that its usable maximum temperature is low. The highest allowable temperature of use of ordinary commercial ion-exchange resins is in the order of around 120° C., i.e., considerably low [(see
ION KOKAN—RIRON TO {overscore (O)}Y{overscore (O)} ENO TEBIKI
(ion-exchange—handbook of theory and application—)], co-translated by Rokuro Kuroda and Masami Shibukawa, 1981, Maruzen Kabushiki Kaisha, p. 34). Hence when the reaction is conducted at a low molar ratio of ammonia to ethylene oxide, the reaction heat causes the temperature rise in the catalyst bed beyond the allowable maximum level, and a prolonged use of the catalyst under such temperature condition invites its deterioration. For this reason, it is difficult to lower the ammonia/ethylene oxide molar ratio to about 20-25 or less.
With the view to overcome the defect in ion-exchange resins that their heat resistance is low, inorganic catalyst excelling in heat stability has been investigated. U.S. Pat. No. 4,438,281 disclosed that generally frequently used silica-alumina exhibited the activity.
Industrial
&
Engineering Chemistry, Product Research
&
Development,
1986, Vol. 25, pp. 424-430 gave a comparative study of ion-exchange resins, various zeolite catalysts and the like, according to which the studied inorganic catalysts did not show better selectivity for monoalkanolamines than that of the ion-exchange resins. Japan KOKAI Hei 2(1990)-225446 disclosed acid-activated clay catalysts, some of which gave monoethanolamine yield as high as 60 percent by weight or even higher. Their selectivity for monoalkanolamines, however, is insufficient and hence the reactions using those catalysts are conducted at ammonia/ethylene oxide molar ratio of 20-30 or still higher, which necessitates high equipment costs for recovery and recirculating use of ammonia and gives rise to many practical difficulties.
As a solution to these problems, Japan KOKAI Hei 7(1995)-173114 proposes as high activity catalysts capable of producing monoalkanolamine with high selectivity, rare earth elements supported on heat-resistant carriers. The object of these catalysts, however, lies in monoalkanolamine production with high selectivity and their performance for producing dialkanolamine while inhibiting side-production of trialkanolamine is still unsatisfactory. Moreover, when such a catalyst exhibiting high selectivity for monoalkanolamine is used, dialkanolamine yield can be increased by recycling a part of the formed and separated monoalkanolamine into the reaction system. In actual practice, however, problems still remain such as high utility costs for the recycling.
East German Patent 298,636 has disclosed a method of selectively synthesizing dialkanolamine through a vapor-phase reaction using a sodium salt of crystalline alminosilicate as the catalyst. Whereas, diethanolamine selectivity in said method was at the most only 23 percent by weight and in that occasion as much as 22 percent by weight of triethanolamine was formed. Thus, the method cannot be regarded suitable for industrial production of diethanolamine.
This invention is made for solving the above problems. The object of the invention is to provide a method for producing dialkanolamine with high selectivity and at high efficiency while inhibiting formation of undesirable side products such as trialkanolamine, in the occasion of preparing dialkanolamine by amination of alkylene oxide with ammonia.
We have engaged in concentrative studies aiming at finding a solution to the above problems, to find that a catalyst having a specific rate constant of reaction is advantageous for the dialkanolamine production. The present invention is thus completed.
Namely, the production method according to the present invention is characterized by,
in an occasion of producing a dialkanolamine which is expressed by the general formula (II) below:
(wherein R
1
, R
2
, R
3
, R
4
, R
5
, R
6
, R
7
and R
8
each independently stands for a hydrogen atom, methyl group or ethyl group)
through a reaction of an alkylene oxide represented by the general formula (I) below:
(wherein R
1
, R
2
, R
3
and R
4
each independently stands for a hydrogen atom, methyl group or ethyl group)
with ammonia at liquid phase, in the presence of a catalyst, carrying out said reaction under the conditions such that
(i) the rate constant &agr; of the reaction between ammonia and alkylene oxide of at least 0.10, when the rate constant between monoalkanolamine and alkylene oxide is 1, and
(ii) the rate constant &bgr; of the reaction between dialkanolamine and alkylene oxide of not more than 0.7, when the rate constant between monoalkanolamine and alkylene oxide is 1.
Mole number of said ammonia is preferably in the range of not less than 2&bgr;/&agr;
0.3
and not more than 1/(1.5&agr;&bgr;
0.5
), per mole of the alkylene oxide.
Preferred catalyst has an a between 0.10 to 1, in particular, between 0.10 and 0.5; and a &bgr; not more than 0.7, in particular, not more than 0.5, inter alia, not more than 0.25.
The catalyst preferably is a microporous material having an effective pore size ranging from 0.45 nm to 0.8 nm.
The catalyst preferably is a metallosilicate which has been ion-exchanged with a rare earth element.
The catalyst preferably has the outer surfaces of its primary particles which have been given an deactivating treatment.
The invention shall be explained in further details hereinafter.
The reaction of ammonia with an alkylene oxide is a sequential reaction, and for selectively producing dialkanolamine, which is an intermediate product, use of a catalyst excelling in selectivity is required. Namely, in said reaction, for example, the following three reactions sequentially take place:
Presuming that the reactions (1), (2) and (3) are primary in regard to the respective concentration of the starting materials, alkylene oxide and ammonia and the amines and when the rate constants of the reaction formulae are k
1
, k
2
and k
3
, respectively, the respective reaction rate can be expressed as follows:
Here the &agr; and &bgr; are defined as follows:
&agr;=
k
1
/k
2
&bgr;=
k
3
/k
2
.
When mole fractions of NH
3
, MAA, DAA and TAA in the reaction liquid where the A0 conversion is 100% are expressed as x, y, z and u, respectively, &agr; and &bgr; are the solutions of the f
Baba Hideyuki
Moriya Atusi
Tsuneki Hideaki
Barts Samuel
Nippon Shokubai Co Ltd
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