DD156187A1 - METHOD FOR HYDROGENATION OF FATS - Google Patents

Abstract

The invention relates to an improved process for the hydrogenation of unsatured to saturated fatty acids having 10 to 24 carbon atoms, in which a comparatively low catalyst consumption is required. The task of carrying out fatty acid dehydrogenation under conditions such that there is extensive use and a slight decrease in the activity of the catalyst used is achieved by hydrogenating at 383 K to 523 K and hydrogen pressures from 1.5 MPa to 2.5 MPa is carried out using a nickel-silica catalyst, which is used in amounts of 0.05 to 0.4 wt.%, Based on the fatty acid to be hydrogenated. The catalyst has a particle size distribution of more than 90% by weight with particle sizes of less than 32 μm and at most 10% by weight with particle sizes of less than 1 μm and is prepared by co-milling of carrier and nickel at a carbonate ion concentration in the paste suspension of at least 55 g / liter ,

Description

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a) Title of the invention

Process for the hydrogenation of fatty acids

b) Field of application of the invention

The present invention relates to an improved process for the hydrogenation of unsaturated fatty acids having 10 to 24 carbon atoms to saturated fatty acids

c) Characteristic of the known technical solutions

It has long been known that unsaturated fatty acids can be hydrogenated at elevated temperatures under elevated hydrogen peroxide pressure in the presence of hydrogenation catalysts to the saturated products. Previously, processes with relatively active palladium catalysts were developed (Brit.P. 18 642). More recent methods work with catalysts in which the palladium on supports, such as aluminum oxide (DE-OS 2210 985) ion exchange resins (DE-OS 2303 170) or oxides of magnesium, titanium or zirconium (DE-OS 2151 482) is applied. While these processes allow for continuous hydrogenation with a fixed catalyst, they are costly due to expensive precious metal catalysts.

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For this reason, in the known processes for the hydrogenation of unsaturated fatty acids to saturated fatty acids usually nickel-supported catalysts are used, which are prepared by precipitation of nickel on diatomaceous earth (DD-PS 82 906). Also continuous hydrogenation with fixed catalyst work with such Ni-supported catalysts (DE-OS 2,207,909). However, because of the mass transport inhibitions occurring within the catalyst moldings and the rapid deactivation of the catalysts by the fatty acids, only a small use of the catalysts with comparatively low product throughputs is possible with these processes.

Comparatively inexpensive operate processes in which the fatty acids with suspended nickel diatomaceous earth catalyst is hydrogenated in autoclaves and after reaching the required Dodzahl the catalyst is separated from the hot hydrogenation product by filtration.

However, the consumption of catalyst is comparatively high even in these processes, because the nickel-diatomaceous earth catalysts used, already conditioned by their production process, strongly fluctuating catalytic activity (see, surfactants, journal of physics, chemistry and application of surfactants, 3.3ahrgang , No. 8, p. 286). The use of the catalysts in the form of powders to form the catalyst suspension in the fatty acids achieves an increase in the external surface area of the catalyst and thus an improvement in the accessibility of the catalytically active nickel surface for the fatty acid molecules to be hydrogenated in comparison with the fixed bed hydrogenation processes in the known bottom phase dehydrogenation processes but the nickel-kieselguhr catalysts used in the known slurry phase suspension dehydrogenation processes have unfavorable broadness

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Kornopoktrum du f. The relatively high proportion of very fine particles he catalyst grains leads rationsschvvierigkeiten in the separation of the catalyst after the hydrogenation to FIIT. On the other hand, it causes a high proportion of coarse quay: inadequate use of the inner surface due to diffusion inhibitions in the pore system of the catalyst granules Because of the low utilization and the comparatively low catalytic activity of the catalysts used known processes for the hydrogenation of fatty acids high reaction temperatures and pressures, such as up to 533 K, to 7 MPa and catalyst concentrations in the reaction mixture to 0.5 %, based on the fatty acid used, are maintained in order to achieve a sufficient degree of hydrogenation takes place an accelerated deactivation of the catalysts by the fatty acids, so that in the known hydrogenation for -> recovery of saturated fatty acids, the catalyst consumption represents a significant cost factor

d) Object of the invention

The aim of the invention is to develop a process for the hydrogenation of fatty acids, which allows the required degree of hydrogenation with low catalyst use.

DESCRIPTION OF THE INVENTION The invention is based on the object of carrying out the hydrogenation of unsaturated fatty acids having 10 to 24 carbon atoms under conditions such that a substantial use is achieved by achieving deactivation of the catalyst used.

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This object is achieved by the present invention, the hydrogenation of the fatty acids at temperatures of 383 K to 488 K, preferably 423 K to 488 K and hydrogen pressures of 1 MPa to 3 MPa, preferably from 1.5 MPa to 2.5 MPa, using a nickel-silica precipitate catalyst, which is prepared by simultaneous precipitation of support and nickel or by adding nickel solution to a mixed solution of sodium carbonate and sodium silicate solution in a period of at least 2 hours at a Karbonationenkonzentrat ion in the precipitation suspension of at least 55 g / l and at a temperature of 330 K to 340 K, filtering off, washing and drying the precipitate, then reducing, stabilizing with oxygen-containing inert gas and grinding is produced, and in the hydrogenation, a catalyst amount of 0.05 to 0.4 wt. %, based on the amount of fatty acid added. It is essential for the process according to the invention that the catalyst used has a particle size distribution of more than 90% by weight with particle sizes of less than 32% by weight and not more than 10% by weight with particle sizes of less than 1 μm. Furthermore, it is important that the hydrogenation times are in the range of 2 to 3 hours, the reaction product is hydrogenated to an oxygen number of less than 2. During the hydrogenation, the catalyst-fatty acid suspension must be thoroughly mixed. This thorough mixing is achieved by intensive stirring or stirring while simultaneously passing a stream of hydrogen through the suspension. The hydrogen is pumped through the autoclave in the circulation.

Under the conditions of the process according to the invention, a surprisingly good use of the catalyst used can be achieved. The deactivation of the catalyst is much slower than under the conditions known

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Method. This results in a relatively low consumption of catalyst. When separating the catalyst from the Hydrierprociukt no filtration problems occur.

A u s e ssure o u rp e rs 1 e

Example 1 (V iews is ρ i e1)

Efin nickel diatomaceous earth catalyst was prepared in the usual way according to the following recipe:

200 g of diatomaceous earth was suspended in 15 l of water in a solution of 5 kg of crystallized nickel nitrate. The suspension was heated to 335 ° K and a solution of 2.7 kg of sodium carbonate in 15 1 of water added within 1 hour. Dor precipitate was filtered off, washed with water and dried at 395 K for 10 hours. Subsequently, the filter cake was deformed and heated in the air stream for 2 hours at 675 K. After activation in the off stream of water at 725 K, the catalyst was stabilized in a nitrogen solution having a 0.5 vol. % Oxygen content. In the subsequent comminution with a mill speed of 5000 rpm, the following particle size distribution was obtained: 24% by weight of the. Catalyst had a particle size below 1 / um and 31 Gcw.% Of the catalyst has a particle size above 32 / jm at ·

This catalyst was used in a stirred autoclave for the hydrogenation of Tcilgfettsäure with a number of iodine 52. Table 1 summarizes the reaction conditions and iodine numbers achieved.

Table 1 trial number

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Reaction Temp. (K) hydrogen pressure (MPa)

Amount of catalyst, bez. on the fatty acid (%) hydrogenation time (h) reached residual iodine number

493 453 433 4 3 3 D. 45 0.2 0.2 3.25 0.5 0.5 1.2 28.9 36

Example 2 (Inventive Example)

A nickel-silica precipitation catalyst was prepared according to the following recipe:

2.7 kg of sodium carbonate were slurried in 8 liters of water and heated to 335 K. 4.45 1 of a solution of sodium silicate containing 45 g of silica / l were added over a period of 30 minutes with vigorous stirring. Subsequently, a solution of 5 kg of crystallized nickel nitrate in enough water to give 7 1 of solution was added at a rate of 3.5 l / h evenly with vigorous stirring to the sodium silicate / sodium carbonate solution kept at 335K. The resulting precipitate was filtered off and washed with water, reduced in Hydrogen rom at 725 K, stabilized in a nitrogen stream with 0.5 % oxygen content and then crushed at a mill speed of 5000 rev / min. The catalyst had the following grain distribution: 9% of the catalyst had a particle size below 1 w / w and to O% of the catalyst has a particle size greater than 32 ^ m..

This catalyst was used in a stirred autoclave for the hydrogenation of tallow fatty acid with an O number of 52. Table 2 summarizes the reaction conditions and the number of ounces achieved.

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Table 2

Test number 4 5 6

Reaction Temp. (K) 483 453 433

Hydrogen pressure (MPa) · 3 3 3

Catalytic converter, bez. on

Fatty acid (%) ° < ⁴ ° ' ² °' ²

Hydrogenation time (h) 2.5 0.5 0.5

reached 3oc ^! number 1.6 18.3 23.8

Comparing Examples 1 and 2 shows that the process according to the invention enables a much better utilization of the catalyst.

Claims (3)

-227U4 invention claim 1. A process for the hydrogenation of unsaturated fatty acids having 10 to 24 carbon atoms to saturated fatty acids in the bottom phase with suspended catalyst, characterized in that the hydrogenation of the fatty acids at temperatures of 283 K to 488 K, preferably at 423 K to 488 K, and hydrogen pressures of 1.5 MPa to 2.5 MPa, using a silica-nickel precipitated catalyst obtained by simultaneously precipitating carrier and nickel, or by adding nickel salt solution to a mixed solution of sodium carbonate and sodium silicate solution in a period of at least 2 hours at a carbonate concentration in the precipitation suspension of at least 55 g / l and at a temperature of 330 K to 340 K, filtering off, washing and drying the precipitate, then reducing, stabilizing with oxygen-containing inert gas and grinding is produced, and that in the Hydrogenation a catalyst amount of 0.05 to 0.4 gevi.%, Based on the used Fatty acid, is used, wherein the catalyst has a particle size distribution of about 90 wt.% With particle sizes of less than 32 yum and at most 10 wt.% With particle sizes less than 1 yum. 2. The method according to item 1, characterized in that a catalyst having a nickel-silicon dioxide ratio of 3 to 5: 1 is used. 3. Method according to item 1 to 5, characterized that the intensively stirred reaction mixture material is circulated at a rate of 35 to 45 Nm / t reaction mixture .. will.