DD295094A5 - PROCESS FOR PREPARING A CATALYST FOR FATTY ACID HYDROGENATION - Google Patents

Abstract

The invention relates to a process for the preparation of nickel-carrier catalysts for the hydrogenation of ungesaettigten to gesaettigten fatty acids in the suspension phase. According to the invention, nickel is precipitated from nickel nitrate solutions in a soda-silica solution having a silicon / carbonate ratio of 0.60 to 0.75 and further nickel precipitated, depending on the amount of nickel extractable from the ethylenediamine precipitate. A calculation rule for the additional amount of nickel to be felled is given. The invention makes it possible to obtain cost-effective, uniform, stable, and highly effective catalysts against fatty acid attacks. {Process; manufacture; Catalyst; Fettsaeurehydrierung; Nickeltraegerkatalysator; Hydrogenation, unsaturated, saturated; fatty acids; Suspension phase; Nickel; Nickel nitrate solution; Soda silicate solution; Silicon / carbonate ratio}

Description

Ni _lu . = (X x S - E x S) / (E + 189 - X) - Ni _verb

the amount of nickel is calculated which, concluding the precipitation process, is added to the precipitation suspension in the form of nickel nitrate solution simultaneously with the sodium carbonate solution required to maintain the pH, wherein in equation "E" the nickel content extractable from the solid of the precipitation suspension by ethylenediamine solution is calculated in% of the total nickel contained in the solid after the precipitation, "S" the amount of SiO ₂ used in the precipitation, "Ni _ver b" the amount of nickel consumed until neutralization, "Ni _zus " the amount of nickel additionally to be finally precipitated and "X. "represent a size with values between 160 and 175.

2. The method according to claim 1, characterized in that the molar ratio silicon / carbonate ions in the soda-silicate solution is 0.65 to 0.70.

3. The method according to claim 2, characterized in that the silicate concentration, calculated as SiO ₂ , in the soda-silicate solution 15 to 18 g SiO ₂ /! is.

4. The method according to claim 3, characterized in that the pH in the soda-silicate solution to 10.8 to 11.3, measured at 293 K, is adjusted.

5. The method according to claim 4, characterized in that in addition sodium hydroxide solution is used to adjust the pH of the soda-silicate solution.

Field of application of the invention The invention relates to a process for the preparation of a catalyst for the hydrogenation of unsaturated fatty acids. Characteristic of the known state of the art

For the hydrogenation of unsaturated fatty acids to saturated fatty acids, nickel catalysts are predominantly used in the art. All experiments with noble metal catalysts (DE-OS 2151482) or with fixed nickel catalysts (DE-OS 2207909) did not lead to the desired results due to the high catalyst costs and the rapid deactivation of the fixed bed catalysts. For example, hydrogenation processes are frequently used today in industry in which work is carried out with suspended nickel-supported catalysts. In the literature, the preferred carriers are SiO ₂ (eg kieselguhr, silica sol) and Al ₂ O ₃ . Various methods are known for applying the hydrogenation-active nickel to the support. Thus, the support can be soaked in a solution of a nickel salt (eg Ni (NO ₃ I ₂ × 6 H ₂ O) (DC _: OS 1442 530).) However, these catalysts have a relatively low catalytic activity, since there is no uniform distribution During drying, the nickel salt migrates with the solvent to the outer surface of the moldings and crystallizes to relatively large particles.

In other processes, nickel is therefore precipitated in the form of an insoluble precipitate on the surface of the support. For this purpose, the support is suspended in the nickel salt solution and precipitated with a precipitating agent (eg NaOH, Na ₂ CO ₃ , NaHCO ₃ ), then the nickel is precipitated thereon (DE-OS 2016602, DE-OS 1943362, DE-OS 1667194). The carriers used in these precipitation methods are natural porous solids (Al ₂ O ₃ or silica gel [DE-OS 2 016 603]). The production of nickel catalysts by co-precipitation of active component and carrier has proven particularly favorable. Precipitation takes place with a basic precipitant at temperatures of 323 to 363K (DE-OS 2726710). Furthermore, it is known to replace part of the solid support by water-soluble silicates (DE-OS 2150975). By observing special precipitation conditions (DD-PS 156168) and by precipitation of a nickel silicate with a Ni / SiO ₂ ratio of 1.5 (DD-PS 206160) as Zwischonprodukt

seeks to improve the uniformity of the precipitates and the catalytic activity of the catalysts prepared therefrom. However, all these methods have in common that catalysts are obtained which are relatively uneinl, vlichlich. In addition, the catalytic activity of the catalysts prepared by the known processes can not yet be satisfied, since the costs of catalyst still account for a decisive proportion of the residues of the hydrogenation processes. For the high catalyst consumption in the fatty acid hydrogenation, the rapid deactivation of the catalysts used is responsible for the attack of the fatty acids. Although the formed nickel soaps are under hydrogenation conditions again reduced to metallic nickel, but the nickel particles grow on the surface of the catalysts, and the activity decreases rapidly.

Object of the invention

The aim of the invention is to develop a process for the preparation of a nickel-supported catalyst for the hydrogenation of unsaturated to saturated fatty acids, which makes it possible to obtain cost-effective, uniform, stable against fatty acid attacks and highly effective catalysts.

Presentation of the essence of the invention

The invention has for its object to develop a process for the preparation of a nickel-carrier Katalysatoro for the hydrogenation of unsaturated to saturated fatty acids, which makes it possible to produce a suspension catalyst with low content of expensive components and high resistance to the fatty acids. The process of the invention should enable the production of very uniform precipitation products and thus lay the foundation for the recovery of effective catalysts.

According to the invention, this object is achieved by a process for the production of nickel-supported catalysts based on the addition of a waterglass solution to a soda solution, uniform metered addition of nickel nitrate solution, separation of the precipitated precatalyst from the precipitation suspension, washing, drying, reducing, stabilizing, and grinding the filter cake, by adding waterglass solution to a soda solution to a molar ratio of silicon to carbonate ions of 0.60 to 0.75, by adding water and basic compounds dissolved therein, a pH, measured at 293 K, of 10.5 to 11 5 and a silicate concentration, calculated as silicon dioxide, of 13 to 20 g per liter of solution are added to this solution while stirring nickel nitrate solution is uniformly added until a pH of 7.0 to 8.5 is reached, the solid of the precipitation suspension with respect to the content of by 10g Ethylenediaminhydrat per g of solid at room temperature In 20 minutes of extractable nickel, the temperature during the precipitation is set to 323 K to 343 K and stirred for 1 to 10 hours, from the measured value of extractable nickel in the precipitate suspension with the equation

Ni _n ,, = (X χ S - E x S) / (E + 189 - X) - N \ ", _b

calculating the amount of nickel which, concluding the precipitation process, is added to the precipitation suspension in the form of nickel nitrate solution simultaneously with the notrium carbonate solution required to maintain the pH, where in the formula, E "is the nickel content extractable from the solid of the precipitation suspension by ethylenediamine solution in% of the nickel contained altogether in the solid after the precipitation, in addition conclusively verfällende "S", the amount of SiO ₂ used in the precipitation, "Ni _{v" b "n} up to neutralize spent nickel amount .ni ,," Nickel quantity and "X" represent a value with values between 160 and 175. It is important for the method according to the invention that the nickel content of the catalyst is determined by the measured value of the extractable nickel It is favorable if the ratio of silicon to carbonate ions is in the range of 0.65 to 0.70, the silicate concentration in the soda-silicate solution Preferably it would be 15 to 18 g SiO ₂ / l and the pH preferably 10.8 to 11.3.

It is crucial for the process according to the invention that the catalysts required for the hydrogenation of unsaturated fatty acids can only be obtained in the quality according to the invention if the prescribed limit values (molar ratio of silicon to carbonate ions 0.6 to 0.75; If these values are not set, then these catalysts have no advantage over known catalysts or are not suitable for the hydrogenation of fatty acids.

The process according to the invention makes it possible to produce very uniform precipitation products and thus lays the foundation for obtaining effective catalysts. The use of the actually effective amounts of active components makes it possible to reduce the costs of catalyst production. The catalysts prepared according to the invention have a significantly higher resistance to fatty acid attacks.

Ausführungsbelsplele Example 1 (Comparative Example)

To a soda solution (2.6 kg of soda slurried in 6 l of water) was added within 30 minutes with vigorous stirring 6.61 of a sodium silicate solution having a SiOj content of 45 g / l. Finally, 3 l of a nickel nitrate solution with a nickel content of 150 g / l were metered in at a rate of 1.5 l / h. The temperature during the precipitation was 333K. The suspension was then stirred for 1 h. Thereafter, another 3.51 of the nickel nitrate solution was passed into the precipitation suspension within 2 hours. The resulting precipitate was washed with water to remove unwanted constituents (eg sodium and nitrate ions), dried at 423 K10 h, then reduced in a stream of hydrogen at 723 K, the hydrogen desorbed at this temperature in a stream of nitrogen and the catalyst after cooling to 353 K Stabilized in a nitrogen stream with an oxygen content of 1 Vcl .-%. After milling to a particle size of less than 32 pm, the catalyst had a nickel content of 65.8%.

Example 2 (comparative example)

To a soda solution, sodium silicate solution, water and sodium hydroxide solution were added until a concentration of silicate, calculated as SiO 2, of 5.8 g per liter, a slurry / carbonation ratio of 0.30 and a pH of 11.0, measured at 293 K, were set. Subsequently, a nickel nitrate solution of 160 g / l was uniformly added to the soda-silicate solution until a pH of 7.7, measured at 273 K, was reached. The temperature during the precipitation was 333 K. From the precipitation suspension, a sample of the precipitate was removed, washed, and about 2 g of ethylenediamine hydrate added and stirred at room temperature for 20 minutes. The precipitate was separated from this suspension and the nickel content was determined both in the solid and in the solution. From the values obtained, the proportion of nickel in the solid of the precipitation suspension was calculated, which can be extracted by ethylenediamine. The determined extractable nickel content "E" was used for the calculation of the additionally required nickel content .Ni _n ,, ". .E "was in the equation

Ni _n ,, = (S x 150 - SXE) / (E + 189 - X) - Ν \ _ηΛ

used. In this equation, .S * corresponds to that in the soda-silicate solution multiplied by the silicate content.

The value of the amount of nickel consumed to reach the pH of 7.7, "Ni _v " _b ", is calculated from the volume of nickel nitrate solution already used multiplied by the nickel content of the solution (160 g Ni / I).

The thus calculated additional amount of nickel to be precipitated was metered in the form of nickel nitrate solution simultaneously with the soda solution required to obtain the pH in the range from 7.0 to 8.5 in precipitation suspension already stirred at 343 K for 3 hours. The resulting precipitate was washed with water to remove unwanted constituents (eg sodium and nitrate ions), dried, reduced in a stream of hydrogen at 673K and converted into the ready-for-use catalyst according to DD-PS 156188.

The finished catalyst had after grinding a particle diameter of less than 32 μπι.

Example 3 Example According to the Invention

To a soda solution, sodium silicate solution, water and sodium hydroxide solution were added until a concentration of silicate, calculated as SiO ₂ , of 16.3 g per liter, a silica / carbonate ratio of 0.69 and a pH of 11.3, was measured at 293 K, were set. Then was a uniform? Nickel nitrate solution of 160g / l dosed to the soda-silicate solution until a pH of 7.4, measured at 293K, was reached. The temperature during the precipitation was 333K. From the precipitation suspension, a sample of the precipitate was taken, washed, and about 2 grams of the solid were suspended in 150 ml of water, 20 grams of ethylenediamine hydrate added and stirred at 298K for 20 minutes. The precipitate was separated from this suspension and the nickel content was determined both in the solid and in the solution. From the values obtained, the proportion of nickel in the solid of the precipitation suspension was calculated, which can be extracted by ethylenediamine. The determined extractable nickel content, E ", was used for the calculation of the nickel content" N! ™, "which is additionally required for the catalyst according to the invention. .E "was in the equation

NU = (SX 165 - SXE) / (E + 189 - X) - Νί « _Λ

used. In this equation, S "corresponds to the silicate used in the soda-silicate solution, calculated as SiO ₂ from the volume of the solution multiplied by the silicate content.

The value of the quantity of nickel consumed to reach the pH of 7.4, "NU ^", is calculated from the volume of nickel nitrate solution already used multiplied by the nickel content of the solution (160 g Ni / i).

The amount of nickel thus precipitated, in the form of nickel nitrate solution, was metered simultaneously into the precipitate suspension stirred for 3 h at 343 K with the soda solution required to maintain the pH in the range from 7.0 to 8.5. The resulting precipitate was washed with water to remove unwanted constituents (eg sodium and nitrate ions), dried and then reduced in a stream of hydrogen at 723K and converted according to DD-PS 156188 into the ready-to-use catalyst. The finished catalyst had a grain diameter of less than 32 μm after the Mahlon. The catalysts from Examples 1 to 3 were tested catalytically. For this de were used in a stirred autoclave for the hydrogenation of tallow fatty acid having an iodine number of 56.1. The table summarizes the reaction conditions and the iodine numbers achieved.

table Temp. Kat amount hydrogenation residual iodine catalyst [K) [%) Ih] 483 0.2 0.5 7.2 example 1 453 0.28 2.5 3.8 (Comparative Example.) 483 0.2 0.5 8.5 Example 2 453 0.28 2.5 4.0 (Comparative Example.) 483 0.2 0.5 4.2 Example 3 453 0.28 2.5. 1.4 (Invention)

The table shows that Example 3 (catalyst of the invention) gives the best results. On the other hand, the catalyst according to Example 2 is not sufficiently resistant to fatty acids, and the catalyst consumption is comparatively high if it is desired to achieve iodine values below 2.

Claims (1)

A process for preparing a nickel-supported catalyst for the hydrogenation of unsaturated to saturated fatty acids on the basis of adding a water glass solution to a soda solution, uniformly metering in a nickel nitrate solution, separating the precipitated precatalyst from the precipitation suspension, washing, drying, reducing, stabilizing and grinding the filter cake, characterized in that water glass solution is added to the soda solution to a molar ratio of silicon to carbonate ions of 0.60 to 0.75, by adding water and basic compounds dissolved therein a pH, measured at 293 K, from 10.5 to 11.5 and a silicate concentration, calculated as silicon dioxide, from 13 to 20 g per liter of solution is added to this solution while stirring nickel nitrate solution is uniformly added until a pH of 7.0 to 8, 5 is reached, the solid of the precipitation suspension with regard to the content of 10 g of ethylenediamine hydrate per gram solid at room temperature in 20 minutes of extractable nickel, adjust the temperature during the precipitation to 323 to 343 K and stir for 1 to 10 hours, from the measured value of extractable nickel in the solid of the precipitation suspension having the formula