Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2000-12-12
2002-04-02
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S857000, C568S885000, C585S250000, C585S273000
Reexamination Certificate
active
06365790
ABSTRACT:
The present invention relates to a very advantageous process for the industrial production of relatively high molecular weight alkenes, in particular of monosubstituted alkenes, by partial hydrogenation of the corresponding alkynes in the liquid phase over fixed-bed supported palladium catalysts with the addition of carbon monoxide (CO) to the hydrogenation hydrogen.
The hydrogenation of alkynes to alkenes is of major industrial importance and is therefore the subject of extensive prior art.
Thus, GB A 871 804 describes an improved partial hydrogenation of acetylene compounds by the suspension procedure using a palladium catalyst (Pd catalyst) which was doped with salt solutions of the metals Zn, Cd, Hg, Ga, In or Tl.
Furthermore, DE A 24 31 929 describes a process for the preparation of 2-butene-1,4-diol by hydrogenation of butynediol in aqueous solution over a catalyst which contains Pd and one of the elements Zn or Cd and at least one of the elements Bi or Te. The catalyst support used is pumice or alumina.
For the partial hydrogenation of the triple bond in intermediates for vitamins and fragrances, lead-doped Pd catalysts, i.e. Lindlar catalysts, are usually used (cf. for example U.S. Pat. No. 2,681,938).
Frequently, these Lindlar catalysts are also deactivated by means of sulfur compounds in order to increase the selectivity (cf. JP A 120 657/81).
U.S. Pat. No. 2,809,215 describes the batchwise hydrogenation of 3,7,11-trimethyl-6-dodecen-1-yn-3-ol over these Lindlar catalysts.
Finally, DE A 26 19 660 discloses a process for the preparation of butenediol, in which butynediol in an inert solvent is hydrogenated in the presence of a catalyst which contains metallic Pd treated with carbon monoxide. This process can additionally be carried out in the presence of from about 200 to 2000 ppm of CO in the hydrogenation hydrogen.
Furthermore, the use of a Pd/BaSO
4
catalyst for the preparation of butenediol is disclosed from DE A 26 05 241.
An overview of the industrially used catalyst systems for the partial hydrogenation of triple bonds to give olefinic double bonds is known from M. Freifelder, “Practical Catalytic Hydrogenation”, Wiley Interscience, New York, 1971, pages 84 to 126.
All stated processes have the disadvantage that a suspended catalyst having a high Pd content is used. After the hydrogenation is complete, the catalyst must be separated off from the reaction product by settling and filtration.
It has been found that, on the industrial scale, complete removal of the catalyst powder is possible only at very great expense. However, traces of catalyst residues in the end product give rise to difficulties during the further processing or during the other use of the alkenes. There has therefore been no lack of attempts to develop a fixed-bed catalyst having high abrasion resistance to the partial hydrogenation of the triple bond in alkynes in the liquid phase.
EP 0 841 314 describes a process for the hydrogenation of 3,7,11,15-tetramethyl-1-hexadecyn-3-ol (dehydroisophytol), which is carried out over amorphous metal alloys, such as Pd
81
Si
19
, in supercritical carbon dioxide, which have been doped with Pb in order to increase the selectivity in the hydrogenation to isophytol. In addition, a sulfur compound, such as 1,2-bis(2-hydroxyethylthio)ethane, had to be added to the hydrogenation mixture in this process, in order to achieve a good yield. The expensive catalyst preparation, the removal and recycling of the carbon dioxide and the additional use of a sulfur-containing compound made the process appear very expensive.
EP 0 412 415 discloses a fixed-bed catalyst for the hydrogenation of 3,7-dimethyloct-1-yn-3-ol (hydrodehydrolinalool) to 3,7-dimethyloct-1-en-3-ol (hydrolinalool), which catalyst contains palladium as an active component and metals such as Sn, Pb, Zn, Cd, Sb or Bi as an inhibitor. The monolithic fixed-bed palladium catalysts described in this patent and doped with inhibitor make it possible to replace the disadvantageous suspension procedure by the technically substantially more advantageous trickle-bed or liquid-phase procedure over the fixed-bed catalyst. The very high abrasion resistance of these catalyst monoliths permits a very high gas and liquid loading.
Unfortunately, it has been found that, when a process described in this patent is carried out continuously over bismuth-doped fixed-bed palladium catalysts over relatively long periods, the selectivity of the hydrogenation of hydrodehydrolinalool to hydrolinalool slowly decreases, i.e. the reaction product contains increasing amounts of the completely hydrogenated 3,7-dimethyloctan-3-ol, which is due to the fact that the bismuth dopant is lost.
EP 754 664 A states that the process according to EP B1 412 415 can be improved by metering small amounts of CO into the hydrogenation gas. The disadvantage of this process is that the space-time yields are still not optimum and that, in the continuous procedure on an industrial scale, the catalysts are not stable and not sufficiently selective over a sufficiently long time.
In the processes according to EP 754 664, EP 0 841 314 and EP 412 415, attention is not paid to the fact that, in the hydrogenation of alkynes, high boilers which adversely affect the overall selectivity always form as a result of oligomerization. However, this formation of high boilers is known from the literature (cf. G. Ertl et al. in “Handbook of Heterogeneous Catalysis”, VCH, 1997, page 2172) and is also described in EP 0 827 944.
EP 827 944 describes a process for the hydrogenation of polyunsaturated C
2
-C
8
-hydrocarbons over the fixed-bed catalysts disclosed in EP 412 415, the dopants being selected from a relatively large group of metals and the catalyst preparation being extended to include the possibility of impregnating the support materials. However, their use is restricted to C
2
-C
8
-hydrocarbons. However, G. Ertl et al. in “Handbook of Heterogeneous Catalysis”, VCH, 1997, pages 2202-2204, discloses that the selectivity in the partial hydrogenation of alkynes depends to a great extent on the alkyne to be hydrogenated, since factors such as mass transfer and heat transfer, adsorption and surface reactions on the catalyst greatly affect the selectivity. It is precisely the factors of mass transfer and heat transfer that depend on the viscosity of the reaction medium (cf. for example M. Baerns, H. Hofmann, A. Renken in “Chemische Reaktionstechnik”, Georg Thieme Verlag Stuttgart, 2nd edition, 1992, pages 67-97), which is generally high for molecules of relatively high molecular weight.
It is an object of the present invention to provide a process for the preparation of alkenes having relatively high molecular weights, i.e. alkenes of about 10 to 30 carbon atoms, preferably monosubstituted alkenes of 10 to 30 carbon atoms, by partial hydrogenation of the corresponding alkynes, which does not have the disadvantages of the suspension procedure, is technically simple to implement and operates with catalysts which are simple to prepare, have long-term stability, have a high overall selectivity and produces very little overhydrogenated products and high boilers.
We have found, surprisingly, that this object is achieved and that monolithic fixed-bed supported palladium catalysts which were obtained by impregnating the heated support material with a palladium salt solution and have been described in EP 0 827 944 for the partial hydrogenation of low molecular weight alkynes can be used with good selectivities for C
10
- to C
30
-alkynes, too, if amounts of CO which are in the range from 10 to 2000 ppm are added to the hydrogenation hydrogen or the alkyne to be hydrogenated is mixed with the compound which decomposes to a small extent with CO elimination but otherwise does not further intervene in the hydrogenation.
The present invention accordingly relates to a process for the preparation of alkenes by partial hydrogenation of alkynes in the liquid phase at from 20 to 250° C. and hydrogen partial pressures of from 0.3 to 200 bar over fixed-bed supported palladium catalysts which a
Ansmann Andreas
Bockstiegel Bernhard
Bröcker Franz Josef
Etzrodt Heinz
Haake Mathias
Barts Samuel
BASF - Aktiengesellschaft
Keil & Weinkauf
Price Eluis O.
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