Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2000-08-29
2002-09-10
Padmanabhan, Sreeni (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S903000, C502S345000, C502S346000, C502S350000
Reexamination Certificate
active
06448457
ABSTRACT:
The invention relates to a process for the catalytic hydrogenation of carbonyl compounds in the presence of a copper catalyst, to the copper catalyst as such and to a process for its preparation.
Catalytic hydrogenation of carbonyl compounds, such as aldehydes, to prepare simple and functionalized alcohols occupies an important place in the production sequences in the basic chemicals industry. This is particularly true of the hydrogenation of aldehydes which can be obtained by the oxo synthesis or the aldol reaction.
Catalytic hydrogenation of aldehydes in a suspension or fixed bed procedure has been known for a long time. Industrial systems operate almost exclusively with fixed bed reactors.
The fixed bed catalysts used, beside catalysts of the Raney type (DE-A 197 30 939), are in particular supported catalysts, for example copper, nickel or noble metal catalysts.
DE-A 16 43 856 describes the hydrogenation of aldehydes to alcohols on combined Cu/Ni supported catalysts in the gas phase. The supports used in this case must be neutralized with alkalis before use.
DE-A 40 37 729 describes a Cu/Cr system which is employed as catalyst for hyrdogenating fatty acids or fatty acid esters but which is problematic in terms of environmental pollution owing to the chromium component. In addition, these catalysts require relatively drastic reaction conditions in the hydrogenation, which may lead to increased formation of unwanted by-products.
Supported catalysts which do not contain the objectionable chromium are described in EP-A 0 044 444. Although the Cu hydrogenation catalysts supported on Al
2
O
3
and employed in the process described therein for preparing propanediol show a high initial activity, their properties are unsatisfactory in terms of their useful lives.
EP-A 0 484 800 discloses the use of Cu/Zn catalysts supported on ZrO
2
for hydrogenating hydroxypivalaldehyde to neopentyl glycol.
U.S. Pat. No. 4 918,248 discloses the use of Cu/Zn catalysts supported on TiO
2
, but the use thereof is restricted exclusively to the hydrogenation of carboxylic esters.
It is an object of the present invention to provide a process for the catalytic hydrogenation of carbonyl compounds employing a catalyst which is easy to prepare industrially, has high mechanical stability under the reaction conditions occurring in said process, and makes high conversions and selectivities possible.
We have found that this object is achieved by an embodiment of tableting in which a dried powder which comprises the support material and the active component is mixed with metallic Cu powder in addition to a conventional tableting aid such as graphite, leading both to particularly easy tableting and to high activities and selectivities, and to high catalyst stability.
An outstanding property of the catalyst tablets obtained in this way is the exceptional mechanical strength. It is only on addition of metallic Cu powder used according to the invention that the tablets acquire the mechanical stability necessary to produce with the chosen support material a catalyst which can be employed usefully under the reaction conditions of catalytic hydrogenation.
Accordingly, the object has been achieved by a process for the catalytic hydrogenation of a carbonyl compound or of a mixture of two or more carbonyl compounds in the presence of a catalyst which comprises an inorganic support containing TiO
2
, and as active component copper or a mixture of copper and at least one of the metals selected from the group of zinc, aluminum, cerium, a noble metal and a group VIII metal, wherein the specific copper surface area does not exceed 10 m
2
/g.
The support preferably used is TiO
2
or a mixture of TiO
2
and Al
2
O
3
or a mixture of TiO
2
and ZrO
2
or a mixture of TiO
2
, Al
2
O
3
and ZrO
2
, particularly preferably TiO
2
.
The catalysts used in the process according to the invention is distinguished in that the copper active component is applied to the support material used, there being no restrictions whatever on the method of application.
The following methods of application are suitable in particular:
a) Application of a copper salt solution in one or more impregnation stages to a prefabricated inorganic support. Following the impregnation, the support is dried and, where appropriate, calcined.
a1) The impregnation can take place by the “incipient wetness” method, in which the support is moistened with the impregnation solution to no further than saturation according to its water-uptake capacity. The impregnation can, however, also take place in a supernatant solution.
a2) In multistage impregnation processes, it is expedient to dry and, where appropriate, to calcine between individual impregnation steps. Multistage impregnation is advantageously to be used particularly when the support is to be loaded with a relatively large amount of copper.
a3) The inorganic support material is preferably employed as preshaped mass for the impregnation, for example as powder, beads, extrudates or tablets. The use of a powder is particularly preferred.
a4) Concentrated aqueous ammonia is preferably employed as solvent for copper salts.
b) Precipitation of a copper salt solution onto a prefabricated inert inorganic support. The latter is, in a particularly preferred embodiment, in the form of a powder in an aqueous suspension.
b1) In one embodiment (i) a copper salt solution is precipitated, preferably with sodium carbonate solution. An aqueous suspension of the support material is present in the recipient vessel.
b2) In another embodiment (ii), the precipitated catalyst can be prepared in a two-stage process. This entails, in a first stage, a powder being prepared and dried as stated in a). This powder is transferred into an aqueous suspension and employed in the recipient vessel equivalent to the description in embodiment (i).
Precipitates resulting from a) or b) are filtered in a conventional way and preferably washed free of alkali.
Both the final products from a) and those from b) are dried at temperatures of from 50 to 150° C., preferably at 120° C., and then, where appropriate, calcined, preferably for 2 hours, in general at 200 to 400° C., in particular at 200 to 220° C.
The starting substances which can be used for a) and/or b) are in principle all Cu(I) and/or Cu(II) salts soluble in the solvents used for the application, for example sulfates, nitrates, chlorides, carbonates, acetate, oxalates or ammonium complexes. Copper carbonate is particularly preferably employed for a) processes and copper nitrate is particularly preferably employed for b) processes.
In the process according to the invention, the dried powder described above is preferably shaped to tablets or similar shaped articles. A tableting aid for the shaping process is added in the form of graphite, preferably in an amount of 3% by weight based on the weight of the dried powder.
A further additive for preparing the catalyst, in addition to the powder described above and to graphite, is added in the form of metallic Cu powder. 5 to 40% by weight of metallic Cu powder, in particular 15 to 20% by weight, are preferably added, based on the weight of the dried powder described above.
Accordingly, the present invention also relates to a catalyst which comprises an inorganic support which contains TiO
2
, and as active component copper or a mixture of copper with at least one of the metals selected from the group of zinc, aluminum, cerium, a noble metal and a group VIII metal, obtainable by a process which comprises a tableting step, wherein metallic copper powder is added in the tableting.
The tableted articles according to the invention are heat-treated at 300 to 600° C., in particular at 330 to 350° C., preferably for 2 hours. This novel type of tableting process makes it particularly easy to shape the powder to tablets, compared with the exclusive use of graphite as tableting aid in conventional processes, and provides very chemically and mechanically stable catalysts.
The parameters of “hardness” and “attrition” can be determined as follows. To determine the cutting
Hesse Michael
Kratz Detlef
Sauerwald Manfred
Schulz Gerhard
Walter Marc
BASF - Aktiengesellschaft
Keil & Weinkauf
Padmanabhan Sreeni
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