Hydrogenation of aldehydes

Details Hydrogenation of aldehydes Hydrogenation of aldehydes

1999-12-28

2002-02-26

O'Sullivan, Peter (Department: 1621)

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

Organic compounds

Oxygen containing

C568S862000

Reexamination Certificate

active

06350923

ABSTRACT:

The invention relates to a process for hydrogenating a dialdehyde, trialdehyde or tetraaldehyde.
The catalytic hydrogenation of dialdehydes, trialdehydes or tetraaldehydes, preferably dialdehydes, in particular glutaraldehyde, for preparing corresponding alcohols, in particular dialcohols, especially 1,5-pentanediol, is a process which is of considerable commercial importance in the basic chemicals industry.
It can be seen from Ullmann's Encyclopaedia of Industrial Chemistry, 5th Edition, 1997, pp. 305-307, that, for example, 1,5-pentanediol is produced industrially by catalytic hydrogenation of glutaric acid or its esters. However, fewer processes for preparing 1,5-pentanediol from glutaraldehyde are known.
Thus, Hodge et al. (Youji Huaxue 9 (1989) 521; CA 112: 998/8p) discloses hydrogenation over an anion-exchange resin which has previously been loaded with borohydride ions. This is a stoichiometric reduction since the borohydride ions are consumed. This process is accordingly not usable for catalytic hydrogenation and is therefore not of industrial interest.
Shim et al., (Tuaeha Hwahakhoe Chi 30 (1986) 101; CA 106; 66709) discloses a homogeneously catalysed reduction of glutaraldehyde to pentanediol using carbon monoxide as reducing agent and catalytic amounts of Rh
6
(CO)
6
or Fe(CO)
5
. This process, too, is so costly that it is not of industrial interest.
It is an object of the present invention to provide a process and a catalyst which allows the catalytic hydrogenation of dialdehydes, trialdehydes or tetraaldehydes to give the corresponding alcohols in high yield under advantageous process conditions, e.g. temperature, pressure and operating life, and is thus inexpensive and industrially useful.
We have found that this object is achieved by a process for hydrogenating a dialdehyde, trialdehyde or tetraaldehyde or at least two thereof as aldehyde by bringing into contact at least the aldehyde, a catalyst comprising at least one metal selected from the group consisting of nickel, cobalt and copper in chemically bound and/or elemental form and hydrogen at a gas pressure in the range from 5 to 350 bar and a temperature in the range from 40 to 300° C. Among the abovementioned metals, nickel and copper are preferred and nickel is particularly preferred.
According to the present invention, it is preferred that the catalyst further comprises at least one metal selected from the group consisting of zirconium, copper, molybdenum, aluminum and manganese in chemically bound and/or elemental form. Furthermore, the presence of noble metals can have an advantageous effect on the catalyst. The noble metals are preferably used in smaller amounts than the abovementioned metals, in particular smaller amounts than nickel, cobalt or copper.
Another catalyst which is preferred according to the present invention is formed from noble metals as hydrogenation-active metals, which are preferably supported. In the case of catalysts comprising noble metals as hydrogenation-active metals, it is particularly preferred that other hydrogenation-active metals in particular nickel, cobalt or copper, are not present in such a catalyst.
For the purposes of the present invention, “chemically bound” means that the metal present in the catalyst is combined with at least one further, preferably nonmetallic, element to form a chemical compound. The nonmetallic elements are preferably elements of main groups V, VI and VII, with preference being given to those of main group VI, particularly preferably oxygen.
The constituents of the catalyst are present in elemental form when the metallic constituents are present in the oxidation state zero. In general, at least part of the metals used in the catalyst are present in elemental form, in particular during the reduction reaction to be catalysed.
The catalysts can be in the form of unsupported or supported catalysts.
The unsupported catalysts contain no further constituents, particularly constituents which function as a support, in addition to the constituents required for the catalytic reaction.
The amount of hydrogenation-active metal, calculated as metal oxide regardless of the form in which it is actually present, is preferably in the range from 80 to 100% by weight, based on the metal oxide, in the case of unsupported catalysts. The remainder can be made up by promoters. The function of the promoter is, in particular, to increase activity and selectivity in the hydrogenation. Particularly preferred promoters are, for example, molybdenum or manganese, preferably in the form of their oxides.
In the case of supported catalysts, the amount of the hydrogenation-active metal(s) or oxide(s) is lower because of the use of the support. Preference is given to using from 30 to 70% by weight of metal oxide(s), regardless of the actual hydrogenation-active form, based on the supported catalyst.
Supported catalysts comprise not only those constituents which are predominantly responsible for the catalytic reaction but also further constituents which do not participate directly in the catalytic reaction and are first and foremost responsible for the mechanical stability of the catalyst. One group of support materials consists of oxidic supports. Oxidic supports which have been found to be usefull are, in particular, zirconium dioxide, titanium oxide, aluminum oxide and silicon oxides. Among these, zirconium dioxide is particularly preferred as support.
Another group of support materials consists of activated carbon and graphite. These supports have been found to be particularly useful when the starting material to be hydrogenated is used as a suspension.
A further group of supports consists of solid bodies of inert materials, for example metal, plastic or ceramic, for example SiC, Si
3
N
4
or W
2
N, preferably metal.
The supports used can have any shape, but preference is given to powders, extrudates, pellets, spheres or rings. The production of the supports can be carried out by the usual generally known methods, as can the application of the metal or noble metal components. In this context, the following information may be provided.
In general, the unsupported catalysts used according to the present invention are obtained from the aqueous solutions of the water-soluble salts of their constituents by precipitation, drying, shaping, if desired calcination and subsequent firing, generally in the presence of oxygen, in a temperature range from 200 to 1000° C.
In the case of the supported catalysts, the above-described process for producing the unsupported catalysts is supplemented by the following, methods of applying the constituents to the support:
In particular, the following application methods are useful:
a) Application of a constituent salt solution to a previously produced inorganic support in one or more impregnation steps. Subsequent to impregnation, the support is dried and, if desired, calcined.
a1) Impregnation can be carried out by the “incipient wetness” method in which the support is treated with an amount of impregnation solution which is not more than that corresponding to the water absorption capacity of the support. However, impregnation can also be carried out with excess solution.
a2) In multistage impregnation methods, it is advantageous to dry and possibly calcine the impregnated support between individual impregnation steps. Multistage impregnation is particularly advantageous when the support is to be treated with a relatively large amount of constituent or is to be impregnated with a plurality of components.
a3) In the impregnation, the inorganic support material is preferably used in preshaped form, for example as powder, spheres, extrudates or pellets. Particular preference is given to using it as powder.
a4) As solvent for the constituent salts, use is made, for example, of concentrated aqueous ammonia.
b) Precipitation of a constituent salt solution onto a previously produced, inert inorganic support. In a particularly preferred embodiment, this is present as powder in an aqueous suspension.
b1) In one embodiment (i), a constituent salt solut

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