Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2001-12-14
2004-01-20
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
C568S861000, C568S878000, C568S429000, C568S444000, C568S451000, C568S772000, C568S798000, C568S814000
Reexamination Certificate
active
06680414
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for the hydrogenation of hydroformylation mixtures, i.e. for preparing alcohols by hydrogenation of aldehydes in the liquid phase in the presence of water.
2. Discussion of the Background
Alcohols can be obtained by catalytic hydrogenation of aldehydes which have been obtained, for example, by hydroformylation of olefins. Large quantities of alcohols are used as solvents and as intermediates for preparing many organic compounds. Important downstream products of alcohols are plasticizers and detergents.
It is known that aldehydes can be catalytically reduced with hydrogen to form alcohols. Catalysts which include at least one metal of groups 1b, 2b, 6b, 7b and/or 8 of the Periodic Table of the Elements are frequently used. The hydrogenation of aldehydes can be carried out continuously or batchwise using pulverulent or palletized/shaped catalysts in the gas or liquid phase.
For the industrial production of alcohols by hydrogenation of aldehydes from the oxo process (hydroformylation of olefins), preference is given, especially in the case of large-volume products, to continuous gas- or liquid-phase processes using catalysts located in a fixed bed.
Compared to gas-phase hydrogenation, liquid-phase hydrogenation has a more favorable energy balance and gives a higher space-time yield. As the molar mass of the aldehyde to be hydrogenated increases, i.e. as the boiling point increases, the advantage of the more favorable energy balance increases. Higher aldehydes having more than 7 carbon atoms are therefore preferably hydrogenated in the liquid phase.
However, hydrogenation in the liquid phase has the disadvantage that, owing to the high concentrations of both aldehydes and alcohols, the formation of high boilers via subsequent and secondary reactions is promoted. Thus, aldehydes can more readily undergo aldol reactions (addition and/or condensation) and form hemiacetals or acetals with alcohols. The acetals or hemiacetals formed can undergo elimination of alcohol or water, respectively, to form enol ethers which are hydrogenated under the reaction conditions to form the saturated ethers. These secondary by-products thus reduce the yield. The by-products referred to as high boilers can at best sometimes be redissociated in downstream plants to give products of value, e.g. starting aldehydes and target alcohols.
Industrial aldehyde mixtures which are used for the hydrogenation frequently already contain varying concentrations of high boilers.
Hydroformylation of olefins in the presence of cobalt catalysts gives crude aldehydes which contain esters of formic acid (formates) and also aldol products, high esters and ethers as well as acetals as high boilers. If these mixtures are hydrogenated in the gas phase, the major part of the high boilers can be separated off in the vaporizer and worked up in a separate process step to give products of value.
In contrast, in the case of the liquid-phase hydrogenation, the high boilers remain in the reactor feed. They are mostly hydrogenated in the hydrogenation step, so that it is no longer possible to obtain a product of value from them.
In U.S. Pat. No. 5,059,710, the yield of alcohols in the hydrogenation of crude aldehydes is increased by redissociating part of the high boilers by means of water at elevated temperature to form aldehydes or alcohols in a process step upstream of the hydrogenation. Hydrolysis and hydrogenation are therefore separate process steps; nothing is said about the water content of the mixture to be hydrogenated.
A similar process is disclosed in U.S. Pat. No. 4,401,834. Here too, the cleavage of high boilers is carried out in the presence of water prior to the actual hydrogenation step.
GB 2 142 010 claims a process for the hydrogenation of crude aldehydes having from 6 to 20 carbon atoms which contain high boilers and small amounts of sulfur compounds to give the corresponding saturated alcohols. The hydrogenation is carried out in two reactors connected in series. The first reactor contains an MoS
2
/C catalyst and the second reactor contains an Ni/Al
2
O
3
catalyst. The hydrogenation in both reactors is carried out with addition of up to 10% of water vapor, based on the feed stream, in a temperature range of from 180 to 260° C. and a hydrogen partial pressure of from 150 to 210 bar using a large excess of hydrogen. In the examples, this is so large that the added water is present virtually only in the gas phase. The object of this process is to suppress the formation of hydrocarbons by hydrogenolysis of the alcohols. Nothing is said about an increase or decrease in high boilers and formates in the hydrogenation.
U.S. Pat. No. 2,809,220 describes a liquid-phase hydrogenation of hydroformylation mixtures in the presence of water. The catalysts used are sulfur-containing catalysts. The hydrogenation is carried out in a pressure range of from 105 to 315 bar and a temperature range from 204 to 315° C. in the presence of from 1 to 10% of water, based on starting material. To keep the added water in the gas phase, a large excess of hydrogen (from 892 to 3566 standard m
3
of hydrogen per m
3
of starting material) is used. As regards the high excess of hydrogen, reference is made to the discussion of GB 2 142 010. A further disadvantage of this process is the high specific energy consumption.
A further process for the hydrogenation of hydroformylation mixtures is disclosed in DE 198 42 370. This document describes the hydrogenation of hydroformylation mixtures in the liquid phase over copper-, nickel- and chromium-containing supported catalysts. Depending on the process used for preparing the hydroformylation mixtures (rhodium or cobalt processes), these mixtures contain water. The process disclosed is designed for the selective hydrogenation of the aldehydes to alcohols, without hydrogenation of the olefins which have remained unreacted in the hydroformylation, i.e. the high boilers (mostly acetals) are not converted into the useful product. This is economically unfavorable and is therefore capable of improvement.
Since the known processes are not economically optimal (e.g., low capital cost, high product yield and low energy consumption), it is desirable to develop a new process for the hydrogenation of aldehydes or aldehyde mixtures to the corresponding saturated alcohols, which process combines the advantages of gas-phase hydrogenation (high selectivity) with those of liquid-phase hydrogenation (low energy consumption, high space-type yield).
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a new process for the hydrogenation of aldehydes or aldehyde mixtures to the corresponding saturated alcohols, which has a low capital cost, high product yield and low energy consumption.
Another object of the invention is to provide a new process for the hydrogenation of aldehydes or aldehyde mixtures to the corresponding saturated alcohols, which process combines the advantages of gas-phase hydrogenation (high selectivity) with those of liquid-phase hydrogenation (low energy consumption, high space-type yield).
These and other objects may be accomplished with the present invention, the first embodiment of provides a process, which includes:
in a homogeneous liquid phase including water, and over a fixed-bed catalyst,
continuously hydrogenating at least one hydroformylation product obtained from a hydroformylation of one or more C
4-16
olefins to produce at least one output mixture;
wherein the fixed-bed catalyst includes at least one element of transition group eight of the Periodic Table of the Elements;
wherein the output mixture includes at least one corresponding alcohol and from 0.05 to 10% by weight of water;
and wherein in a steady-state operation of the process, from 3 to 50% more hydrogen is fed to the hydrogenation than is consumed by the hydrogenation.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Various other objects, features and attendant advantages of the present invention will be more fully appreciated
Büschken Wilfried
Gubisch Dietmar
Kaizik Alfred
Knoop Cord
Scholz Bernhard
Barts Samuel
Oxeno Olefinchemie GmbH
Witherspoon Sikarl A.
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