Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
1999-04-01
2001-01-23
Dentz, Bernard (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C549S315000
Reexamination Certificate
active
06177598
ABSTRACT:
The present invention relates to a process for preparing sugar alcohols by hydrogenation of sugars using catalysts comprising one or more metals of transition group VIII of the Periodic Table as active component(s).
Sugar alcohols such as sorbitol, mannitol, maltitol and xylitol are widely used in the food industry, in cosmetics, in pharmacy and in the industrial sector.
Processes for preparing sugar alcohols from the corresponding sugars by hydrogenation, in particular batchwise processes in which pulverulent metal catalysts, e.g. nickel catalysts, are used in a suspension process, are known from the prior art (cf. Ullmanns Encykl. der Technischen Chemie, Vol. 24, p. 772 (1983)).
EP-A 0 773 063 describes a continuous process for the hydrogenation of sugars over a Raney Ni—Al catalyst at 130° C. and 150 bar.
Hydrogenations of sugars over supported Ru catalysts have likewise been described. U.S. Pat. No. 4,471,144 describes the hydrogenation of carbohydrates in aqueous solution in the presence of a ruthenium-on-&thgr;-Al
2
O
3
catalyst. U.S. Pat. No.4,487,980 describes a similar process in which a catalyst comprising a metal of transition group VII and TiO
2
as support is used. U.S. Pat. No. 4,380,680 describes the use of a supported catalyst comprising &agr;-Al
2
O
3
as support and a metal selected from among Os, Ru, Pd and Pt as active component in the hydrogenation of sugars to give sugar alcohols.
A study of the deactivation of the catalysts used which occurs in such hydrogenations is described, using the hydrogenation of glucose using Ru on Al
2
O
3
as catalyst as an example, in a scientific article in Applied Catalysis A: General 87 (1992), pp. 219-229.
Although, as can be seen from the above summary of the prior art, a number of processes for the hydrogenation of sugars are already known, the catalysts used hitherto not infrequently have short operating lives as a result of deactivation or “bleeding” of the catalyst. Furthermore, noticeable epimerization, decomposition or polymerization of the sugar alcohols frequently occurs during the hydrogenation under the conditions selected.
It is an object of the present invention to provide new processes for the hydrogenation of sugars in which specific catalysts comprising one or more metals of transition group VIII of the Periodic Table as active metal are used. These new processes should make it possible, in particular, to obtain virtually epimer-free sugar alcohols in very high yields at a virtually complete conversion. Furthermore, only a minimal proportion of by-products or decomposition products compared to the conventional processes should be formed during the hydrogenation so as to enable a subsequent work-up of the sugar alcohols to be carried out in a simple and economical manner.
We have found that this object is achieved by, in one embodiment of the present invention, a process for the hydrogenation of a sugar or a mixture of two or more thereof, which comprises the following step:
Bringing the sugar or the mixture of two or more thereof into contact with hydrogen in the presence of a catalyst to give a sugar alcohol or a mixture of two or more thereof, wherein the catalyst comprises at least one homogeneous compound of at least one metal of transition group VIII of the Periodic Table, either alone or together with at least one metal of transition group I or VII of the Periodic Table, deposited in situ on a support (catalyst 1).
In a further embodiment, the present invention provides a process for the hydrogenation of a sugar or a mixture of two or more thereof, which comprises the following step:
Bringing the sugar or the mixture of two or more thereof into contact with hydrogen in the presence of a catalyst to give a sugar alcohol or a mixture of two or more thereof, wherein the catalyst comprises as active metal at least one metal of transition group VIII of the Periodic Table, either alone or together with at least one metal of transition group I or VII of the Periodic Table, in an amount of from 0.01 to 30% by weight, based on the total weight of the catalyst, applied to a support, where from 5 to 50% of the pore volume of the support is made up by macropores having a pore diameter in the range from 50 nm to 10,000 nm and from 50 to 95% of the pore volume of the support is made up by mesopores having a pore diameter in the range from 2 to 50 nm, where the sum of the pore volumes is 100% (catalyst 2).
The present invention also provides a process for the hydrogenation of a sugar or a mixture of two or more thereof, which comprises the following step:
Bringing the sugar or the mixture of two or more thereof into contact with hydrogen in the presence of a catalyst to give a sugar alcohol or a mixture of two or more thereof, wherein the catalyst is a monolithic supported catalyst which can be produced by successive heating and cooling in air of a support material in the form of a metal mesh or a metal foil, subsequent coating under reduced pressure with an active component and subsequent cutting and shaping of the coated support material and final processing to give a monolithic supported catalyst, where the active metal used is at least one metal of transition group VIII of the Periodic Table, either alone or together with at least one metal of transition group I or VII of the Periodic Table (catalyst 3).
As active metal, it is in principle possible to use any metal of transition group VIII of the Periodic Table. Preference is given to using platinum, rhodium, palladium, cobalt, nickel or ruthenium or a mixture of two or more thereof as active metal, with particular preference being given to using ruthenium as active metal. As the metals of transition group I or VII or else I and VII of the Periodic Table which can also be used, preference is given to using copper and/or rhenium, although any of them can be used in principle.
For the purposes of the present invention, the terms “macropores” and “mesopores” are used as they are defined in Pure Appl. Chem., 45, p. 79 (1976), namely as pores whose diameter is above 50 nm (macropores) or whose diameter is from 2 nm to 50 nm (mesopores).
The active metal content is generally from about 0.01 to about 30% by weight, preferably from about 0.01 to about 5% by weight and in particular from about 0.1 to about 5% by weight, in each case based on the total weight of the catalyst used. In the case of the catalysts 1 to 3, preferred contents are again indicated individually in the discussion of these catalysts.
If customary catalyst support systems, e.g. activated carbon, silicon carbide, aluminum oxide, silicon dioxide, titanium dioxide, zirconium dioxide, magnesium oxide, zinc oxide or mixtures thereof, are used for producing the catalysts used according to the present invention, they are in each case used in spherical, extrudate or ring form if they are to be used as fixed-bed catalysts and as grit or fine granules for use in suspension. Further details regarding these support systems may be found in the discussion of the individual catalysts 1 to 3.
For the purposes of the present invention, it is in principle possible to use any sugar. The term “sugar” used in the context of the present invention encompasses monosaccharides such as glucose, mannose, galactose, talose, fructose, allose, altrose, idose, gulose, xylose, ribose, arabinose, lyxsose, threose and erythrose, disaccharides and trisaccharides such as maltose, lactose, cellobiose, sucrose, melibiose and raffinose, and polysaccharides such as starch, starch decomposition products, cellulose and cellulose decomposition products, e.g. dextrin, glucose syrup, cellulose hydrolysates and starch hydrolysates such as maize starch hydrolysates.
In the processes of the present invention, preference is given to converting glucose into sorbitol, mannose into mannitol, fructose into a mixture of sorbitol and mannitol, xylose into xylitol, lactose into lactitol and maltose into maltitol.
Catalyst 1
The process of the present invention can be carried out in the presence of a catalyst 1 which comprises at least one homogeneous co
Bottcher Arnd
Breitscheidel Boris
Brunner Melanie
Henkelmann Jochem
BASF - Aktiengesellschaft
Dentz Bernard
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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