Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2002-02-28
2003-02-18
Dentz, Bernard (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
active
06521763
ABSTRACT:
The present invention relates to a process for preparing gamma-butyrolactone (GBL) by reaction of a 1,4-butanediol-containing reaction mixture over a copper catalyst.
Processes for preparing GBL from 1,4-butanediol have been known for a long time. K. Weissermel, H.-J. Arpe, Industrielle organische Chemie, VCH Verlagsgesellschaft, D 69451 Weinheim, 1994, page 112, describes the dehydrocyclization of 1,4-butanediol over copper catalysts at from 200 to 250° C.
A disadvantage of this process for preparing GBL is that the 1,4-butanediol used has to be purified before use. The purification is usually carried out by means of a complicated multistage distillation in which undesired low- and/or high-boiling constituents, including water, are removed. This water-free pure butanediol is subsequently cyclized to form GBL, with undesirable by-products being formed. For this reason, the cooled GBL again has to be purified by distillation after the reaction. It is thus necessary to carry out two comparable, complicated purification and separation steps.
It is an object of the present invention to provide a process for preparing GBL from 1,4-butanediol in which the butanediol used does not have to be prepurified and the formation of undesirable by-products is avoided.
We have found that this object is achieved by a process for preparing GBL by reaction of 1,4-butanediol over a copper catalyst in which a 1,4-butanediol-containing reaction mixture which comprises further alcohols other than 1,4-butanediol and water is used.
The process of the present invention has the advantage that the 1,4-butanediol-containing reaction mixtures used do not have to be prepurified prior to the reaction to form GBL. 1,4 butanediol can be cyclized to GBL in the presence of further alcohols without appreciable amounts of by-products being formed. This dispenses with the complicated prepurification, so that costs can be saved.
The 1,4-butanediol-containing reaction mixtures used as feed for the reaction can be obtained by known methods.
Thus, for example it is possible to use a 1,4-butanediol-containing reaction mixture which is obtained from acetylene and formaldehyde by the Reppe process and subsequent hydrogenation of the 1,4-butynediol formed, or by acetoxylation or chlorination of butadiene by hydrogenation of 4-hydroxybutyraldehyde and 2,3- or 2,5-dihydrofuran.
The feed used is preferably the hydrogenation product from the hydrogenation of a compound selected from the group consisting of 1,4-butynediol, 4-hydroxybutyraldehyde, 2,3- or 2,5-dihydrofuran, maleic acid, maleic monoesters, maleic diesters and maleic anhydride and/or an intermediate formed in their hydrogenation. Such intermediates are, for example, succinic anhydride, succinic acid or succinic diesters. Particular preference is given to using the hydrogenation product from the hydrogenation of 1,4-butynediol, 4-hydroxybutyraldehyde, maleic acid or maleic diesters as feed in the reaction to form GBL.
The hydrogenation can be carried out in a known manner in the gas phase or the liquid phase. For example, dimethyl maleate can be hydrogenated in the gas phase over a catalyst, e.g. copper chromite, under superatmospheric pressure and at elevated temperature. The hydrogenation product obtained, which is used as feed in the reaction according to the present invention, generally comprises 5-95% by weight of butanediol and 15-95% by weight of alcohol, preferably from 10 to 70% by weight of butanediol and from 5 to 70% by weight of alcohol, particularly preferably from 15 to 60% by weight of butanediol and from 15 to 50% by weight of alcohol. In addition, products such as succinic diesters, water, 4-hydroxybutyric acid and its esters as well as 4 hydroxybutyraldehyde may be present in an amount of up to 30% by weight. The succinic diester content is generally not critical for the process. Furthermore, water may be present in an amount of generally less than 5% by weight, preferably less than 2% by weight, particularly preferably less than 1% by weight, together with small amounts of further compounds. It is also possible for GBL to be present in the hydrogenation product; the GBL content is not critical for the process and may be, for example, from 10 to 30% by weight. If the hydrogenation product from the hydrogenation of 1,4-butynediol, 4-hydroxybutyraldehyde or maleic acid as butanediol source is used, not only water but also generally n-butanol as alcohol component are present. The molar ratio of n-butanol to 1,4-butanediol in these hydrogenation products can be, for example, from 0.5:100 to 5:100.
In place of the total hydrogenation product, it is also possible for only a substream of the hydrogenation product to be fed to the reaction to form GBL. The reaction product of the reaction to form GBL can be fed to the same work-up columns as the substream of the hydrogenation product which has not been reacted further, since both contain similar impurities and by-products. Thus, different apparatuses do not have to be operated for comparable separation tasks.
The reaction mixture in the process of the present invention for preparing GBL generally contains aliphatic alcohols which are preferably monohydric. Aliphatic alcohols having from 1 to 4 carbon atoms, e.g. methanol, ethanol, iso- and n-propanol and n-butanol, are particularly preferably present.
According to the present invention, the 1,4-butanediol-containing reaction mixture is reacted at from 200 to 350° C., preferably from 230 to 330° C., particularly preferably from 230 to 240° C. The reaction is carried out in a pressure range from 0.5 to 10 bar, preferably from 0.8 to 5 bar, particularly preferably from 1 to 3 bar.
Depending on the temperature and pressure conditions selected, the GBL formed and the alcohol and water can go over from the liquid phase to the gaseous phase or remain in the liquid phase. At low reaction pressures, the product stream will leave the reactor in gaseous form. The hydrogen liberated in the reaction can be used as carrier gas for the starting material stream/product stream.
The process of the present invention is carried out using a catalyst which comprises copper either alone or together with at least one metal of transition group VIII of the Period Table, preferably applied to a support.
In principle, all metals of transition group VIII of the Periodic Table can be used in addition to the copper. However, preference is given to using nickel, palladium, cobalt or ruthenium or a mixture of two or more thereof.
The copper content of the catalyst is generally from 1 to 80% by weight, preferably from 3 to 50% by weight and particularly preferably from 5 to 40% by weight, in each case based on the total weight of the catalyst and calculated as metal.
The supported copper catalysts which are preferably used according to the present invention can be produced industrially by applying the copper and, if desired, at least one metal of transition group VIII of the Periodic Table to a support.
The application can be achieved by impregnation of the support in aqueous metal salt solutions, for example aqueous copper solutions, by spraying appropriate metal salt solutions onto the support, by precipitation of the metals and support materials or by other suitable methods.
Suitable copper salts or metal salts of transition group VIII of the Periodic Table are the nitrates, nitrosyl nitrates, halides, carbonates, carboxylates, acetylacetonates, nitrito complexes or ammonia complexes of the corresponding metals, with preference being given to the nitrates, carboxylates and ammonia complexes. When copper salts and metal salts of transition group VIII of the Periodic Table are applied by impregnation, they can be applied to the support either simultaneously or in succession.
The supports which have been coated or impregnated with the metal salt solution are subsequently dried, preferably at from 100 to 150° C., and, if desired, calcined at from 200° C. to 600° C., preferably from 350 to 450° C. In the case of separate impregnation, the catalyst is dried and, if appropriate, calcined afte
Fischer Rolf
Pinkos Rolf
BASF - Aktiengesellschaft
Dentz Bernard
Keil & Weinkauf
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