Hydrogenation of carbonyl compounds

Details Hydrogenation of carbonyl compounds Hydrogenation of carbonyl compounds

2003-09-29

2004-09-07

Price, Elvis O. (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Oxygen containing

C568S852000, C568S853000, C568S861000, C568S863000, C568S462000, C568S449000, C568S458000, C502S345000, C502S350000, C502S346000, C502S351000, C502S103000, C502S113000

Reexamination Certificate

active

06787677

ABSTRACT:

The invention relates to a process for the catalytic hydrogenation of carbonyl compounds in the presence of copper-containing catalyst tablets and to the copper-containing catalyst tablets themselves.
The catalytic hydrogenation of carbonyl compounds such as aldehydes for producing simple and functionalized alcohols is acquiring an important position in production streams of the basic chemicals industry. This applies particularly to the hydrogenation of aldehydes which are obtainable via the oxo process or the aldol reaction.
The catalytic hydrogenation of carbonyl compounds is carried out virtually exclusively in fixed-bed reactors in industrial processes. Catalysts used include not only catalysts of the Raney type but also, in particular, supported catalysts, for example copper, nickel or nobel metal catalysts.
U.S. Pat. No. 3,923,694 describes, for example, a catalyst of the copper oxide/zinc oxide/aluminum oxide type. The disadvantage of this catalyst is that it is not sufficiently mechanically stable during the reaction and therefore disintegrates relatively quickly. This results in a loss in activity and a buildup of a differential pressure over the reactor due to the disintegrating catalyst bodies. As a consequence, the plant has to be shut down prematurely.
DE-A 195 05 347 describes in quite general terms a process for producing catalyst tablets having a high mechanical strength, in which a metal powder or a powder of a metal alloy is added to the material to be tabletted. For example, aluminum powder or copper powder is added as metal powder. However, the addition of aluminum powder in the case of a copper oxide/zinc oxide/aluminum oxide catalyst results in a shaped body which has a worse lateral compressive strength than a shaped body which has been produced without addition of aluminum powder, and the shaped body of the invention when used as catalyst displayed a worse conversion activity than catalysts which had been produced without addition of aluminum powder. The document likewise discloses a hydrogenation catalyst comprising NiO, ZrO
2
, MoO
3
and CuO to which Cu powder, inter alia, was added during production. However, this document says nothing about the selectivity or the activity.
DE 198 09 418 describes a process for the catalytic hydrogenation of a carbonyl compound in the presence of a catalyst comprising a support consisting predominantly of titanium dioxide and, as active component, copper or a mixture of copper with at least one metal selected from the group consisting of zinc, aluminum, cerium, nobel metals and metals of transition group VIII, where the copper surface area is not more than 10 m
2
/g. Preferred support materials are mixtures of titanium dioxide with aluminum oxide or zirconium oxide or aluminum oxide and zirconium oxide. In a preferred embodiment, the catalyst material is shaped with addition of metallic copper powder.
It is an object of the present invention to provide a process for the catalytic hydrogenation of carbonyl compounds using a catalyst which can be produced industrially in a simple manner, has a sufficiently high mechanical stability under the reaction conditions occurring in such a process and, in particular makes it possible to achieve long catalyst operating lives and high conversions and selectivities.
It has been found that tabletting a dried powder comprising the support material, the active component and a customary tabletting aid, e.g. graphite, together with metallic Cu powder to form catalyst tablets having a diameter d and/or a height h of less than 3 mm leads to high activities and selectivities and to good stability of the catalyst.
Accordingly, the abovementioned object is achieved by a process for the catalytic hydrogenation of a carbonyl compound or a mixture of two or more carbonyl compounds in the presence of catalyst tablets which comprise an inorganic, TiO
2
-containing support and, as active component, copper or a mixture of copper with at least one metal selected from the group consisting of zinc, aluminum, cerium, nobel metals and metals of transition group VIII and whose copper surface area is not more than 10 m
2
/g, wherein the diameter d and/or the height h of the tablets is less than 3 mm.
As support, preference is given to using 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 catalyst used in the process of the present invention is produced by applying the active component copper to the support material used, with there being no restrictions in respect of the application method.
In particular, the following application methods are possible:
a) application of a copper salt solution in one or more impregnation steps to a previously produced inorganic support. The support is dried after the impregnation and calcined if appropriate.
a1) The impregnation can be carried out by the “incipient wetness” method in which the support is treated with an amount of the impregnation solution corresponding to its water absorption capacity so that it is just saturated. However, the impregnation can also be carried out with the support covered by the solution.
a2) In multistage impregnation processes it is advantageous to dry and if appropriate calcine the support between individual impregnation steps. Multistage impregnation is particularly advantageous when the support is to be treated with a relatively large amount of copper.
a3) The inorganic support material is preferably used as a preshaped composition in the impregnation, for example as powder, spheres, extrudates or tablets. Particular preference is given to using powder.
a4) As solvent for the copper salts, preference is given to using concentrated aqueous ammonia.
b) Precipitation of a copper salt solution onto a previously produced, inert inorganic support. In a particularly preferred embodiment, the latter is present as a powder in an aqueous suspension.
b1) In one embodiment (i), a copper salt solution is precipitated, preferably by means of sodium carbonate solution. As initial charge, use is made of an aqueous suspension of the support material.
b2) In a further embodiment (ii), the precipitated catalyst can be produced in a two-stage process. Here, the first step comprises producing and drying a powder as described in a). This powder is converted into an aqueous suspension and used as substrate in a second step equivalent to embodiment (i).
The precipitated solids resulting from a) or b) are filtered off in a customary manner and preferably washed free of alkali.
Both the final products from a) and those from b) are dried at from 50 to 150° C., preferably at 120° C., and subsequently calcined if appropriate, preferably for 2 hours at generally from 200 to 400° C., in particular from 200 to 220° C.
As starting materials for a) and/or b), it is in principle possible to use all Cu(I) and/or Cu(II) salts soluble in the solvents used for the application to the support, for example sulfates, nitrates, chlorides, carbontes, acetates, oxalates or ammonium complexes. For method a), particular preference is given to using copper carbonate, while method b) is particularly preferably carried out using copper nitrate.
To produce the catalyst tablets of the present invention, the above-described dried powder is shaped by means of a suitable tabletting press to form tablets having a diameter d of less than 3 mm and/or a height h of less than 3 mm, preferably d and/or h of less than 2 mm, particularly preferably d and/or h of 1.5 mm. As tabletting aid, graphite is added in the shaping process, preferably in an amount of 3% by weight, based on the weight of the dried powder.
As further additive in addition to the above-described powder and to graphite, metallic Cu powder is added in the production of the catalyst. Preference is given to adding, based on the weight of the above-described dried powder, from 5 to 40% by weight of metallic Cu powder, in particular from 15 to 20% by weight.
The catalyst tablets can be symmetrical, i.e. the height h and th

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