PROCESS FOR THE HYDROGENATION OF ALDEHYDES IN AT LEAST TWO HYDROGENATION STAGES

Abstract

The present invention relates to a process for producing alcohols by hydrogenation of C4 to C20 aldehydes. The process according to the invention is performed in two consecutive hydrogenation stages, wherein the first hydrogenation stage employs an activated metal catalyst based on a nickel metal foam and the second stage employs a supported catalyst containing a catalytically active component from the group consisting of nickel, copper, chromium and mixtures thereof.

Claims

1. Process for producing alcohols by continuous hydrogenation of C4 to C20 aldehydes in at least two hydrogenation stages, wherein a stream containing the C4 to C20 aldehydes to be hydrogenated is hydrogenated with a hydrogen-containing gas over an activated metal catalyst based on a nickel metal foam in the liquid phase in the first hydrogenation stage comprising at least one reactor, wherein a crude product stream containing at least alcohols and unconverted aldehydes, of which at least a portion is passed to the second hydrogenation stage, is withdrawn from the at least one reactor, at least a portion of the crude product stream is hydrogenated with a hydrogen-containing gas over a supported catalyst comprising a catalytically active component and a support material in the liquid phase in the second hydrogenation stage comprising at least one reactor operated in straight pass, wherein the catalytically active component is selected from the group consisting of nickel, copper, chromium and mixtures thereof and wherein the support material consists to an extent of more than 90% by weight of an oxidic material selected from the group consisting of aluminum oxide, aluminum silicate, silicon dioxide, titanium dioxide, zirconium oxide and mixtures of two or more thereof.

2. Process according to claim 1, wherein at least one recycle reactor is employed in the first hydroformylation stage.

3. Process according to claim 1, wherein the stream employed in the hydroformylation contains C4 to C16 aldehydes, preferably C9 to C13 aldehydes, particularly preferably isononanal, 2-propylheptanal or isotridecanal.

4. Process according to claim 1, wherein the activated metal catalyst based on a nickel metal foam is free from organic constituents, i.e. the sum of the weight fractions of carbon and carbon-containing compounds is less than 0.2% by weight of the total weight of the catalyst.

5. Process according to claim 1, wherein the activated metal catalyst based on a nickel metal foam contains 80% to 95% by weight of nickel and 5% to 15% by weight of aluminum in each case based on the total weight of the catalyst.

6. Process according to claim 5, wherein the activated metal catalyst based on a nickel metal foam additionally contains 0.01% to 3% by weight of molybdenum, particularly preferably 0.2% to 1.5% by weight of molybdenum and very particularly preferably 0.3% to 0.7% by weight of molybdenum, in each case based on the total weight of the catalyst.

7. Process according to claim 1, wherein the hydrogenation in the first hydrogenation stage is performed at a pressure of 5 to 150 bar, preferably 15 to 50 bar, particularly preferably 20 to 45 bar.

8. Process according to claim 1, wherein the hydrogenation in the first hydrogenation stage is performed at a temperature of 50° C. to 250° C., preferably 80° C. to 200° C., particularly preferably of 100° C. to 190° C.

9. Process according to claim 1, wherein the conversion of the hydrogenation in the first hydrogenation stage is at least 85%, preferably at least 90%, particularly preferably at least 95%.

10. Process according to claim 1, wherein the volume fraction of the activated metal catalyst based on a nickel metal foam in the total catalyst volume of all hydrogenation stages is from 30% to 80%, preferably 35% to 60%.

11. Process according to claim 1, wherein the support material of the supported catalyst is aluminum oxide, aluminum silicate or silicon dioxide.

12. Process according to claim 11, wherein the support material has a BET surface area of 70 to 350 m.sup.2/g, preferably 150 to 280 m.sup.2/g.

13. Process according to claim 1, wherein the hydrogenation in the second hydrogenation stage is performed at a pressure of 5 to 250 bar, preferably 10 to 150 bar, particularly preferably 15 to 30 bar.

14. Process according to claim 1, wherein the hydrogenation in the second hydrogenation stage is performed at a temperature of 100° C. to 220° C., preferably 120° C. to 210° C., particularly preferably 140° C. to 200° C.

15. Process according to claim 1, wherein the hydrogenation is carried out with a stoichiometric excess of hydrogen based on the aldehydes to be hydrogenated in both hydrogenation stages.

Description

EXAMPLE 1 (INVENTIVE)

[0039] The hydrogenation was carried out in two hydrogenation stages, wherein the first hydrogenation stage employed an activated metal catalyst based on a nickel metal foam (catalyst 1) and the second hydrogenation stage employed a supported catalyst comprising nickel and copper as the catalytically active component and aluminum oxide as the support material (catalyst 2). The supported catalyst is obtainable as Specialyst© 103 from Evonik Operations GmbH. The hydrogenation was performed with isononanal as the aldehyde.

[0040] Production of the activated metal catalyst based on a nickel metal foam (catalyst 1)

[0041] A nickel foam commercially available in rolls having a thickness of 1.9 mm, a width of 300 mm and an average pore size of 580 μm was sprayed with a commercially available polyethyleneimine adhesion promoter solution and coated with an aluminum powder (oxygen content: 0.5% by weight) containing 96.5% by weight of aluminum particles having a particle size <150 μm (d.sub.90≈68 μm) and subjected to a multistage heat treatment in the absence of oxygen at a temperature of not more than 725° C. The mass ratios of the employed nickel foam and aluminum powder were chosen such that the ratio of aluminum to the total mass of the supported alloy was 28±2%. Cooling was followed by a comminution of the material with a laser into cuboidal particles having an edge length of 4×4×1.9 mm. The resulting bulk material was activated by a 60 minute treatment in a 10% by weight aqueous sodium hydroxide solution at 60° C. The catalyst was then washed with DM water until achievement of a pH<10.

Molybdenum Doping

[0042] 250 g of the freshly produced catalyst were treated with a 55.4% by weight ammonium heptamolybdate solution at room temperature over several hours until the molybdenum present in the solution had been completely deposited on the activated nickel foam catalyst. Monitoring of the molybdenum deposition was effected by detection of molybdenum in the supernatant solution with Merckoquant or Quantofix test strips. Treatment was terminated when molybdenum was no longer detectable in the supernatant solution. The catalyst was subsequently washed twice with DM water. The final catalyst contained more than 87% by weight of nickel, about 12% by weight of aluminum and less than 1% by weight of molybdenum.

Performing the Reaction

[0043] The hydrogenation of isononanal was carried out in a tubular reactor in recycle operation with a connected second tubular reactor in straight pass. The recycle tubular reactor had an internal diameter of 20.5 mm and a length of 730 mm. The second reactor had an internal diameter of 20.5 mm and a length of 1000 mm. The tubular reactors were operated with the liquid phase (isononanol and recycled hydrogenation product) and the gas phase (hydrogen) running in cocurrent in trickle bed mode. The recycle reactor employed 100 mL of catalyst 1 as hydrogenation catalyst. The second reactor employed 100 mL of catalyst 2. The feed rate of isononanol employed in the hydrogenation was 600 g/h. The recycle stream was 25 L/h. Hydrogen regulation (1.6 L/min -4 ml/min) was effected via a constant offgas mode with an offgas stream of 1 L/min. The experiments were each performed at a plant pressure of 26 bar in the recycle tubular reactor and 22.5 bar in the second tubular reactor. The reaction temperature in the recycle tubular reactor was varied between 130° C. and 170° C. A temperature of 180° C. was employed in the second tubular reactor. The output from the hydrogenation unit was analyzed by gas chromatography for the conversion of isononanal. The conversion of the isononanal after the second reactor was >99%. The experimental conditions are reported in table 2.

TABLE-US-00001 TABLE 2 Overview of hydrogenation conditions Temperature of recycle reactor/° C. 130-170 Pressure of recycle reactor/bar  26 Feed rate of isononanal/gh.sup.−1 600 Recyle rate of liquid phase/Lh.sup.−1  25 Volume of catalyst in recycle reactor/mL (catalyst 1) 100 Length of catalyst bed/mm 320 Offgas/NLmin.sup.−1  1 WHSV/g of isononal * (ml of catalyst * h).sup.−1  6

EXAMPLE 2 (NONINVENTIVE)

[0044] Example 2 was performed in very much the same way as example 1. However, example 2 differs from example 1 in that the first hydrogenation stage and the second hydrogenation stage each employed a supported catalyst with nickel and copper as the catalytically active component and aluminum oxide as the support material (catalyst 2). In addition, 200 ml of catalyst 2 had to be employed in the recycle reactor and the feed rate of the isononanal had to be reduced to 230 g/h. A higher temperature of a constant 180° C. was also employed in the recycle reactor. The conversion of the isononanal after the second reactor was likewise >99%. An overview of the hydrogenation conditions may be found in table 3 which follows.

TABLE-US-00002 TABLE 3 Overview of hydrogenation conditions Temperature of recycle reactor/° C. 180 Pressure of recycle reactor/bar 26 Feed rate of isononanal/gh.sup.−1 230 Recycle rate of liquid phase/Lh.sup.−1 25 Volume of catalyst in recycle reactor/mL (catalyst 1) 200 Length of catalyst bed/mm 640 Offgas/NLmin.sup.−1 1 WHSV/g of isononal * (ml of catalyst * h).sup.−1 1.15

[0045] It is very clear that the use of an activated metal catalyst based on a nickel metal foam in the first hydrogenation stage makes it possible to establish significantly higher feed rates and smaller catalyst volumes at unchanged conversions of >99%.

[0046] The activated metal catalyst based on a nickel metal foam also makes it possible to use lower temperatures in the recycle reactor.

[0047] The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

[0048] From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.