DD206160B1 - METHOD FOR HYDROGENATING UNSATURATED FATS - Google Patents

Description

-2- 366 49

Filtration, washing and drying in a stream of hydrogen, the hydrogen is desorbed and the catalyst is then stabilized with oxygen-containing inert gas and ground, after which it contains 55 to 65 wt .-% nickel. According to the process, unsaturated fatty acids having 10 to 24 carbon atoms per fatty acid molecule are used and the hydrogenation product has an iodine value of 2 after the hydrogenation time of 1.5 to 2.0 hours. During the hydrogenation the reaction mixture is stirred intensively and to lead a hydrogen atom of 35 to 45 Nm ³ / t reaction mixture is circulated through the reaction mixture. Under the conditions of the process according to the invention, a surprisingly good use of the catalyst used can be achieved. Due to the relatively short hydrogenation times, a high utilization of the hydrogenation autoclave is possible. The poisoning of the catalyst is much slower than under the conditions of known methods.

Exemplary embodiments Example 1 (comparative example)

A nickel-SiO ₂ precipitated catalyst was prepared according to the following recipe: 3.1 kg of sodium carbonate were slurried in 81 water and heated to 335 K. With vigorous stirring, 4,451 of a solution of sodium chloride containing 45g of SiO ₂ Zl and 7l of a nickel nitrate solution containing 160g of Ni / I nickel was simultaneously added to the sodium carbonate slurry over 2 hours with vigorous stirring. The resulting precipitate was filtered off and washed with water. Subsequently, the filter cake was reduced for 10 hours at 425 K, in the hydrogen stream at 725 K, the hydrogen desorbed at this temperature by means of a nitrogen stream and the catalyst after cooling to 353 K in a nitrogen stream with an oxygen content of 1 vol .-% stabilized. After milling to a particle size of less than 32μιη the catalyst, which had a nickel content of 74%, 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) 483 453 433 Hydrogen pressure (MPa) 3 3 3 amount of catalyst based on fatty acid (%) 0.35 0.2 0.2 Hydrogenation time (h) 2.5 0.5 0.5 Achieved residual iodine number 1.3 9.8 13.6

Example 2

A nickel-SiCV precipitated catalyst was prepared according to the following recipe:

2.5 kg of sodium carbonate were slurried in 61 water and heated to 335 K, within 30 minutes with vigorous stirring 6.61 of a solution of sodium silicate containing 45 g of SiO ₂ /! added. Subsequently, 31 of a nickel nitrate solution containing 150 g of Ni / I were added within 2 hours. The suspension was then stirred for 1 hour at 335K. Thereafter, another 3.51 of a nickel nitrate solution containing 150 g of Ni / I was introduced into the precipitation suspension within 2 hours. The precipitate was filtered off and washed with water. The filter cake was then dried for 10 hours at 426 K, reduced in a stream of hydrogen at 725 K, the hydrogen desorbed at this temperature by means of a nitrogen stream and the catalyst after cooling to 353K in a nitrogen stream with an oxygen content of 1 vol .-% stabilized. After milling to a particle size of less than 32 μπ \ was the catalyst, which had a nickel content of 61.2%, 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 the residual iodine numbers achieved.

Table 2

test number

Reaction temperature (K) 478 453 433 Hydrogen pressure (MPa) 3 3 3 amount of catalyst based on fatty acid (%) 0.3 0.2 0.2 Hydrogenation time (h) 2 0.5 0.5 Achieved residual iodine number 1.5 6.1 7.3

Example 2 shows that under the conditions of the process according to the invention lower hydrogenation times and lower amounts of catalyst are necessary to achieve the required degrees of hydrogenation than in the known processes (Example 1).

Claims (1)

-1- 366 49 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 having a nickel content of 55 to 65 wt .-% in amounts of 0.05 to 0.3 wt .-%, by common Precipitation of the nickel and the carrier with a basic precipitating agent is prepared, at temperatures of 413 to 478 K, hydrogen pressures of 1 MPa to 3 MPa and intensive stirring in a circulation of the hydrogen at a rate of 35 to 45 Nm ³ A reaction mixture, characterized in that the precipitation of the catalyst proceeds in two stages, wherein in the first step a nickel silicate with a nickel-silica weight ratio of 1.5: 1 is formed from a mixture of the solution of the precipitant sodium carbonate and the alkali metal silicate by addition of nickel nitrate solution and the suspension of the Nickel silicate is stirred at 325 K for at least 60 min and ansch In the second step, addition of further nickel salt solution takes place. 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 In the art, suspended catalyst processes are commonly used. In principle, continuously operating processes with a fixed catalyst are also known. In these processes, palladium catalysts with different carriers, such as aluminum oxide (DE-OS 2310170), ion exchange resins (DE-OS 2 303170) or MgO, SiO ₂ , TiO ₂ , ZrO ₂ (DE-OS 2151482) are used. Because of the expensive noble metal catalysts, the processes are uneconomical. Continuous processes with fixed nickel-supported catalysts allow due to the occurring mass transport inhibitions within the catalyst moldings and the relatively rapid poisoning of the catalysts only low throughputs and low use of the catalysts (DE-OS 2207909). Comparatively inexpensive operate processes in which the fatty acids are hydrogenated with suspended nickel-SiO ₂ catalyst in the autoclave and separated after reaching the required iodine number of the catalyst from the hot hydrogenation point by filtration. However, the consumption of catalyst is also comparatively high in these processes, because the nickel-SiO ₂ catalysts used, due to their production process, have greatly varying catalytic activity (Tenside, Journal of Physics, Chemistry and Application of Surfactants, Volume 3, Issue 8, p. 286). Through the use of the catalysts in the form of powder for the formation of the catalyst suspension in the fatty acids, an enlargement of the outer surface of the catalyst and thus an improvement of the accessibility of the catalytically active nickel surface for the fatty acid molecules to be hydrogenated compared to the fixed bed hydrogenation process is achieved in the known bottom phase but the nickel-SiO ₂ catalysts used in the known slurry phase with suspended catalysts have a comparatively low nickel surface, since of the amount of nickel in the catalyst, a high proportion is arranged inside of relatively large nickel crystallites and a further portion of parts of the support is enclosed. This results in a lower utilization of nickel and a relatively low catalytic activity. In order to achieve a sufficient degree of hydrogenation, therefore, in the known processes for the hydrogenation of fatty acids, severe reaction conditions, such as temperatures up to 533, pressures of up to 7 MPa and catalyst concentrations in the reaction mixture of more than 0.5%, based on the amount of fatty acid used. Under the harsh reaction conditions, an accelerated deepening of the catalysts by the fatty acids occurs, so that in the known hydrogenation process for the recovery of unsaturated 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 unsaturated fatty acids to saturated fatty acids, which enables the required degree of hydrogenation with high space-time yield 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 under such conditions that a high utilization and low poisoning of the catalyst used is achieved. This object is achieved by the hydrogenation of the unsaturated fatty acids at temperatures of 413 K to 478 K and hydrogen pressures of 1 MPa to 3 MPa using a nickel-SiO 2 precipitated catalyst in amounts of 0.05 to 0.3 wt .-%, based on the fatty acid used, which is prepared by coprecipitation of the nickel and the carrier with a basic precipitant, wherein according to the invention in the first step from a mixture of the solution of the precipitant sodium carbonate and the alkali metal silicate by the addition of nickel nitrate a nickel silicate with a nickel-SiO ₂ Weight ratio of about 1.5: 1 formed and the suspension of the nickel silicate at 325 K for at least 60 minutes is stirred and then added in the second step addition of further nickel solution and then in a known manner by