DD156187B1 - METHOD FOR HYDROGENATION OF FATS - Google Patents

Description

_2- 274 44

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 μm 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 iodine value 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 of known methods. This results in a relatively low catalyst consumption. When separating the catalyst from the hydrogenation no filtration problems occur.

embodiment

Example 1 (comparative example)

A nickel-diatomaceous earth catalyst was usually prepared according to the following recipe:

200 g of diatomaceous earth was suspended in 151 ml 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 151 water within 1 hour added. The precipitate formed was filtered off, washed with water and dried at 395K 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 hydrogen stream at 725 K, the catalyst was stabilized in a nitrogen stream with 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 μm and 31% by weight of the catalyst had a particle size greater than 32 μm.

This catalyst was used in a stirred autoclave for the hydrogenation of tallow fatty acid having an iodine value of 52. Table 1 summarizes the reaction conditions and iodine numbers achieved.

Table 1

test number

Reaction temperature (K) hydrogen pressure (MPa)

 Amount of catalyst, bez

 on the fatty acid (%) hydrogenation time (h) reached residual iodine number

498

453 3

0.2

0.5

28.9

433 3

36.7

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 L of water and heated to 335K. Over a period of 30 minutes, 4.451 of a solution of sodium silicate containing 45 g of silicon dioxide / l were added with vigorous stirring. Subsequently, a solution of 5 kg of crystallized nickel nitrate in enough water to give 71 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 a stream of hydrogen at 725 K, stabilized in a nitrogen stream with 0.5% oxygen content and then comminuted at a mill speed of 5000 rev / min.

The catalyst had the following particle size distribution: 9% of the catalyst had a particle size below 1 μηη and 0% by weight of the catalyst had a particle size greater than 32 μηη.

This catalyst was used in a stirred autoclave for the hydrogenation of tallow fatty acid having an iodine value of 52. Table 2 summarizes the reaction conditions and iodine numbers achieved.

Table 2

test number

Reaction temperature (K) 488 Hydrogen pressure (MPa) 3 Amount of catalyst, bez. on Fatty acid (%) 0.4 Hydrogenation time (h) 2.5 reached iodine number 1.6

453 3

0.2

0.5

18.3

433 3

23.8

Example 3 (comparative example)

A catalyst prepared according to Example 1 was used in a stirred autoclave for the hydrogenation of tallow fatty acid having an iodine value of 52. Table 3 summarizes the reaction conditions and the iodine numbers achieved.

Reaction temperature (K) 463 Hydrogen pressure (MPa) 1.5 Amount of catalyst, based on fatty acid (%) 0.4 Hydrogenation time (h) 1 reached Restiodzahl 16.1

_3_ 274 44

Table 3

Test number 7 8

463 2

0.4 1 10.9

Example 4 (Inventive Example)

A catalyst prepared according to Example 2 was used in a stirred autoclave for the hydrogenation of tallow fatty acid having an iodine number

used by 52. Table 4 summarizes the reaction conditions and the iodine numbers achieved.

Table 4

Experiment number 9 10

463 2

0.4

3.3

Reaction temperature (K) 463 Hydrogen pressure (MPa) 1.5 Amount of catalyst, based on fatty acid (%) 0.4 Hydrogenation time (h) 1 reached iodine number 6.4

Claims (2)

-1- 274 44 Invention claim: A process for the hydrogenation of unsaturated fatty acids having 10 to 24 carbon atoms to saturated fatty acids in the slurry phase with suspended nickel-silica catalyst precipitated by adding nickel solution to a mixed solution of sodium carbonate and sodium silicate and after drying, reducing, stabilizing and milling a Komgrößensspektrum of over 90% less than 32μιη and at most 10Gew .-% less than 1 ^ m, at hydrogen pressures of 1.5 to 3 MPa and temperatures of 383 K to 488 K, characterized in that the catalyst used in a period of at least 2h at a carbonate concentration of at least 55 g / l was precipitated. 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. · Characteristic of the known technical solutions It has long been known that unsaturated fatty acids can be hydrogenated at elevated temperatures under elevated hydrogen pressure in the presence of hydrogenation catalysts to the saturated products. Previously, processes with relatively active palladium catalysts were developed (Brit. Pat. 18642). More recent methods work with catalysts in which the palladium supported, such as alumina (DE-OS 2310985), ion exchange resins (DE-OS 2303170) or oxides of magnesium, titanium or zirconium (DE-OS 2151482) is applied. While these processes allow for continuous hydrogenation with a fixed catalyst, they are cost prohibitive due to expensive precious metal catalysts. 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 kieselguhr (DD-PS 82906). Even continuous hydrogenation with fixed catalyst work with such Ni-supported catalysts (DE-OS 2207909). 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 are hydrogenated with suspended nickel-diatomaceous earth catalyst in an autoclave and after reaching the required iodine number of 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. Vintage, Issue 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 an unfavorable broad grain spectrum. The relatively high proportion of very finely divided catalyst grains leads to filtration difficulties in the separation of the catalyst after the hydrogenation. On the other hand, the high proportion of coarse catalyst particles causes insufficient use of the inner surface due to diffusion inhibition in the pore system of the catalyst grains. Because of the low use of the relatively low catalytic activity of the catalysts used in the known processes for the hydrogenation of fatty acids high reaction temperatures and pressures such as up to 533 K, up to 7 MPa and catalyst concentrations in the reaction mixture to 0.5%, based on the fatty acid used to achieve a sufficient degree of hydrogenation. Under these reaction conditions, an accelerated deactivation of the catalysts by the fatty acids, so that in the known hydrogenation process for the production of saturated fatty acids, the catalyst consumption represents a significant cost factor. 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. Explanation of the essence of the invention The invention has for its object to carry out the hydrogenation of unsaturated fatty acids having 10 to 24 carbon atoms under such conditions that an extensive use is achieved by a low deactivation of the catalyst used. This object is achieved by the present invention, the hydrogenation of the fatty acids at temperatures of 383 K to 488 K and hydrogen pressures of 1 MPa to 3MPa, preferably from 1.5 to 2.5 MPa, using a nickel-silica precipitation catalyst is carried out 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 concentration of carbonate ions in the precipitation suspension of at least 55 g / l and at a temperature of 330 K to 340 K, filtration, washing and drying of the precipitate, followed by reduction, stabilization with oxygenate