DE1946225A1 - Process for the production of catalytically active material - Google Patents

Description

Registration number 2111 D

STAMICARBON N.V., van der Maesenstraat 2, HEERLEN / NETHERLANDS

Process for the production of catalytically active material (addendum to patent application P 17 67 202.5)

The main patent (patent application P 17 67 202.5)

relates to a process for the preparation of a catalyst in which the catalytically active substance in a finely divided state on a carrier in such a way as to contain the catalytic substance Solution is suspended so that in the solution homogeneous hydroxyl ions are formed slowly that the migration speed of the precipitated Substance to the surface of the carrier substance is high enough to avoid the formation of precipitation nuclei in the solution, so that the catalytically active substance is precipitated exclusively on the suspended carrier in the form of a hydroxide or insoluble salt, whereupon the so loaded Carrier separated from the solution, dried, if necessary. is annealed and reduced.

It is known that the catalytic activity of a catalyst is generally proportional to the size of the specific surface area of the catalytically active material. The size of the surface per unit volume of catalyst has a direct influence on the size of the reactor in which the catalyst is used * Since large reactors are generally more difficult to operate, efforts are made to produce catalysts with a large specific active surface. For this, however, the following is necessary: 1. The catalytically active material must be distributed in the form of very fine particles on a carrier material. For industrially useful catalysts, a diameter of the catalytically active particles of 50 % or less is recommended; 009 8 3 7/1850

2. The active parts must be separated from one another and homogeneously over the carrier surface be distributed. Under homogeneous distribution is in this addition. together understood that the density of the catalyst particles on the Carrier surface is the same everywhere «This is of great importance because in the case of a locally excessive concentration of catalyst particles sinter these together when heated, whereby the .specifically effective Surface area is significantly reduced;

3. The active particles must and may be accessible to reaction participants E.g. from the temporarily released during the manufacturing process and subsequently reprecipitated carrier not included will; . . . ,

4. The carrier material must contain a high degree of catalytically active material be loaded, e.g. in a weight ratio of catalytically active Material to carrier of 1: 1 or higher;

5. The loaded carrier material must easily become wear-resistant bodies of more uniform Shape and dimensions can be deformed.

It should also be possible to use the catalyst in a simple manner to regenerate without the material sintering together.

Heat-resistant substances such as silicon dioxide, aluminum oxide, titanium oxide and the like are usually used as carriers for the catalytic particles.

The method according to the main application allows catalytically active Manufacture material that meets the conditions mentioned and with the simple Metal salt solutions, such as sulfate, nitrate or chloride solutions, can be used areΓ The procedure is based on the principle that when there are hydroxyl ions form homogeneously and gradually in the solution of the catalytically active material, ' any precipitation nuclei exclusively on the surface of a Foreign matter arise (in the present case on the carrier substance suspended in the solution), and that the precipitate with noticeable energy to the Carrier is bound. The prerequisite for this is that it be homogeneous and gradual Formation of hydroxyl ions takes place. Homogeneous is understood to mean that the hydroxyl ion concentration is exactly the same in the whole solution, even if arbitrarily small volume units are considered; gradual Formation of hydroxyl ions means that the concentration increases depending Time unit is lower than the extent to which the material to be precipitated from the Solution migrated to the surface of the carrier material. Any formation of nuclei

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BATH

in the solution outside the surface of the carrier material is avoided.

Because the free energy and consequently the solubility product of precipitation nuclei is significantly higher than that of the precipitated particles, the hydroxyl ion concentration needs a critical value at which precipitation nuclei can form outside the surface of the carrier comes not to be exceeded if only the formation of hydroxyl ions takes place homogeneously and gradually in the solution and under conditions that can be monitored. In the main application for this homogeneous and gradual formation of hydroxyl ions some methods are given according to which the hydroxyl ions are introduced into the solution by chemical reactions.

The homogeneous and gradual required to carry out the procedure However, increasing the hydroxyl ion concentration in the solution by adding an alkaline solution cannot be easily realized. The object of the invention is therefore, in a further development of the method according to the main patent, to show a possibility with the addition of an alkaline one Solution to work. The invention consists in that the slow and homogeneous increase in hydroxyl ions is generated by vigorously Stir an alkaline solution gradually into the suspension of the carrier injected in the solution of the catalytically active substance. The alkaline Solution is brought into contact with the suspension without any other phase in the immediate vicinity. This is done in a surprisingly easy way an extraordinarily rapid distribution of the alkaline solution in the suspension achieved without surface tension complicating the distribution, so that the hydroxyl ion concentration, even with a gradual increase, decreases as before is homogeneous.

The stirring intensity and the injection speed must be very precise with the total amount of alkaline solution required for the final result. So it is desirable that the middle pH of the suspension during the precipitation does not increase more than 0.1 unit per minute and the deviation from the mean course does not exceed 0.05 pH unit.

An advantage of the present method over the method according to of the main application using urea or nitrite in that the pH can be better monitored. If necessary, it can Γλ »! Splash of alkaline solution can be adjusted 'if the pH value is a

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δ ■

reached a certain size. The invention is particularly suitable for the large-scale application of the method according to the main application. Of the Gradient of the increase in hydroxyl ion concentration with time, as well as the The relevant absolute values can be programmed by comparing the observed pH values of the suspension with the amounts of alkaline to be injected Easily monitor the solution effectively. In addition, they can Formation of - in the absolute sense - large amounts of hydroxyl ions slow chemical reactions at increased temperature can be avoided. The present procedure can, if necessary. at lower temperatures be carried out, the time duration for the precipitation process and the Gradient of the pH value are optimally adjustable.

The possibility of the exact adjustment of the pH value is, among other things, from Significance in the precipitation of amphoteric hydroxides, which only exist in one limited range of pH values are insoluble. This applies e.g. to aluminum and zinc hydroxide, which when the pH rises too high in the form of Dissolve aluminate or zincate. In the procedure according to the main application, the The rate of formation of the hydroxyl ions is regulated by the Temperature of the suspension of the carrier in the solution of the catalytic sets the effective component to a certain value. A sudden one Quenching this suspension can only be achieved with great effort, therefore, after a certain pH value is reached, the reaction continues for some time, whereby the pH value continues to rise, which is disadvantageous can be.

The present method is used to advantage when Nitrite ions or ammonia together with the elements to be precipitated Form complexes; when using urea and sodium nitrite result Trouble. It can then take advantage of a solution of soda or sodium hydroxide be injected. With ammonia and ammonium carbonate are likewise get excellent results for several elements. In some Cases must be increased in order to avoid insoluble ammonia complexes Temperature of e.g. 80 C.

The alkaline solution is preferably injected at already known way so that the solution through a thin pipe \ inter dem Suspension level is initiated. So that the supply of alkaline Solution runs with the desired evenness, the task

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a gas-filled buffer vessel is installed in front of the spray pipe.

The conditions under which some catalysts according to the present Processes were produced, are explained in more detail by means of examples. ·

The precipitation process is illustrated in FIGS. 1 to 4, wherein the pH curve is shown during the addition of the precipitant. The increase in pH, which in some cases after exceeding the Equivalence point occurred is indicated by dashed lines. For this purpose, the relevant, completely reproducible curves determined in separate experiments been.

Example I.

Manufacture of nickel catalysts

In the case of a low level of loading of the carrier, precipitation can be carried out with

Ammonia take place at room temperature; if a high degree of loading is required, so the precipitation must take place at a higher temperature.

a. 14.7 g of Ni (NO2) are combined. 6 HO; 10 g SiO "Aerosil" and 600 cm distilled water. The ratio between Ni and SiQ was 1: 3.4. With continuous vigorous stirring, a 1-η ammonia solution in an amount of 6 cm was in the hour in the mixture injected subsequently at room temperature with the liquid level. The process was terminated when the pH reached 8.9. The carrier material loaded in this way, after it had settled, was filtered through a normal filter paper, washed with 1 liter of distilled water and dried at 120 ° C. for 20 hours. The filtrate was clear and colorless. The analysis showed the following composition of the material: Ni 18.1 % by weight; SiO ₀ 61.7 wt%; NH ₀ 0.2 wt%; NO ₀ 2.9 wt%.

Δ O d

The course of the pH of the suspension as a function of time is shown in FIG. The ordinate is the pH value and the abscissa is the time in minutes. At the same time there is the molar ratio on the abscissa

++ indicated between supplied NH ₃ and Ni present. The addition of the AauBonia solution begins at point A, precipitation begins at point and ends at point C. The mean increase in pH due to precipitation was 0.008 units per minute with a maximum of 0.013 units per minute.

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The X-ray diffraction test revealed two unidentifiable bands. The broadening of the X-ray reflections resulted in an average particle size of 44 A. After reducing the material in-hydrogen during For 72 hours at a temperature of 390 ° C., the preparation showed the X-ray diffraction diagram of nickel with broadened reflections. This broadened reflection resulted in an average particle size of 18 up to 19 SL

b. 492.8 g Ni (NO) ₂ · 6 H> 80.3 g SiO ₃ "Aerosil" and 4 liters of distilled water were combined. The ratio of Ni to SiO was 1.5: 1.

With continued vigorous stirring, was under the liquid surface

3 at room temperature a 10N ammonia solution with an amount of 276 cm initiated in the hour. The pH rose to 7.5 without any Ni connection failed. The temperature was then increased to 100.degree elevated. During the preheating, the pH dropped to 4.7. The introduction of the 10 η ammonia solution was carried out at the temperature of 100.degree continued until a pH of 6.8 was reached and the The liquid turned light blue because a nickel ammonium complex was formed would have. The experiment was stopped at this pH value. The so laden one After it had settled, the carrier material was filtered through normal filter paper, washed out with 2 liters of distilled water and then washed for 20 hours dried for a long time at 100 ° C.

The analysis showed the following composition of the material: Ni 37.4 wt. %; SiO 23.7% by weight , NH 0.3% by weight, No. 9.1 GeW ₁ %. An X-ray diffraction test did not reveal any identifiable pattern. An average particle size of 50-55 A was determined from the broadening of the X-ray reflections Reduction of the material in hydrogen for hours at a temperature of 350 G was the specific nickel surface

2 ■■ '■■ - ■ "ο

flat 63 m per g of nickel. After reduction at a temperature of 500 C- '

2 this surface increased up to 114 m per g of nickel.

Example II

As can be seen from Examples Ua and b, the dimensions of the precipitated iron oxide particles are smaller at a high treatment temperature than at room temperature.

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BATH ORIGINAL

a. 1 g of SiO “Aerosil” was suspended in 3 liters of distilled water; the The suspension was then boiled to remove undissolved oxygen. At a temperature of 85 C, 42 cm were then one Ferrochloride solution, which contained 2 g of iron, added. Under continued vigorous stirring was at the said temperature below the

Liquid level with an amount of 500 cm per hour an oxygen-free Injected ammonium carbonate solution, which contained 26 g ammonium carbonate per liter. This reagent was added over 17 minutes, until a pH of 8.5 was reached. The so loaded carrier was after it settled down, passed through a normal paper filter for filtration, washed out with 1 liter of distilled water and held for 24 hours dried at 100 ° C. The filtrate was clear and colorless.

The analysis showed the following composition: Fe 41.5% by weight; SiO 25.5% by weight NH <0.1% by weight; CO 0.6% by weight; 6 Cl " <0.1% by weight.

An X-ray diffraction test showed that the presence of δ-FeOOH was by no means excluded. On the basis of the broadening of the X-ray reflections a mean particle size of 25 Å could be determined. b; 1 g of SiO “Aerosil” was suspended in 2 l of distilled water; thereafter the suspension was boiled to remove undissolved oxygen.

3. ■ After cooling to room temperature, 42 cm of a ferrochloride solution were added added, which contained 2 g of iron. While stirring continuously vigorously at room temperature under the surface of the liquid with a lot

from 500 cm per hour an oxygen-free 0.25 N sodium carbonate solution injected. This reagent was added over 17 minutes until the pH was reached Was 9.2. The loaded carrier, after it had settled, was passed through normal filter paper for filtration, with 1 liter of distilled Washed out with water and dried at 100 ° C. for 72 hours. The filtrate was clear and colorless even after 72 hours of exposure to air, which indicates the presence of unprecipitated ferrochloride. The material had the following composition:

Fe 46.2 wt%; SiO ₀ 20.9 wt%; CO_ 2.6% by weight; Cl "< 0.1% by weight; Na 0.6% by weight. In a manner similar to that of FIG. 1, FIG. 2 shows the course of the pH value during the precipitation process. In this diagram, the pH value is shown as the ordinate and the BehandJ-ungszeit in min, and the molar ratio between beige give-Na ₀ CO and present Fe as abscissa. the addition of the

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Sodium carbonate solution starts at point Ä, precipitation starts Point B and ends at point C. The mean rise in pH ' . during the precipitation process was 0.08 units per minute with a maximum of 0.37 units per minute. The X-ray diffraction test did not result in an identifiable diagram. The broadening of the X-ray reflections indicated an average particle size of 50 Å. .

Example III . '

Manufacture of zinc catalysts

31.6 g of ZnCl ₀ , 0.8 cm of concentrated HCl,

20 g SiO ₀ "Aerosil" and 800 cm of distilled water. Under constantly vigorous

Stirring was a 1 n affl-

■ "■ '3

monia solution injected at a rate of .218 cm per hour. The injection the solution was carried out for 2 hours and 10 minutes until the suspension had a pH of 7.8. The experiment was discontinued at this value.

The now loaded ^ carrier material, after it had settled, was

; "'■." 3 - - - '■ "- ■■■ Filtered through a normal filter paper with 800 cm of distilled water washed out and dried at 120 ° C for 19 hours.

Analysis of the material thus obtained showed a Zn Z ¹ A SiO ratio of 1: 1. The course of the pH of the suspension over time / is shown in FIG. 3. · ''. . :

The ordinate axis is the pH value and the abscissa axis is the treatment time in minutes and the molar ratio between added NH and what is present Zn applied. The addition of the ammonia solution, as well as the- "PrH-zipitation starts at point A. Precipitation ends at point B. The mean rise in pH ... was 0.03 units during precipitation per minute.-Precipitation is only complete in a pH range under 8 »The method according to the invention followed here is particularly suitable for suddenly ending the increase in the pH value after a value of 8 has been reached ..

■ - .. An X-ray diffraction test showed the presence of Zn_ (OH) ₀ Cl ₀ . From the broadening of the X-ray reflections, an average particle size of 450 Å could be determined. But electron micrographs showed that only a few large zinc-containing crystallites were present _£. while the great majority of the zinc oxide was distributed in finely dispersed form over the carrier. The dimensions of these small zinc oxide particles were about 30 A.

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Example IV

Manufacture of tin catalysts

a. 15.0 g of SnCl were combined. . 5 H ₀ O; 75 g SiO "Aerosil" and 2 liters of distilled water.

With constant vigorous stirring at room temperature below the

A 1 η ammonia solution is injected into 3 liquid levels with a throughput of 500 cm per hour. After the pH had reached 3.1, the experiment was discontinued. The carrier substance, which had sunk to the bottom and loaded in this way, was passed through a normal filter paper for filtration, washed out with 1 liter of water and dried at 120 ° C. for 20 hours. After annealing at a temperature of 450 ° C., the following composition of the material could be determined on the basis of an analysis: SnO ₀ 8.4% by weight; SiO ₀ 91.5% by weight.

Al £ t

An X-ray diffraction test showed no identifiable chart. As a Electron microscopic examination revealed the particle size was to 50 A. The course of the pH value of the suspension as a function of time is shown in FIG. On the vertical axis is the pH and on the horizontal axis the treatment time and the molar ratio between

4+ '■ added NH and present Sn applied. The addition of the ammonia solution and the precipitation start at point A; the precipitation process is ended at point B. The mean increase in pH was 0.03 Units per minute with a maximum value of 0.15 units per minute «In a separate experiment (dashed line in Fig. 4) was the pH value increased further while the ammonia solution was continued to be injected. At a value of 7, all of the tin had dissolved again in the form of stannate. The method according to the invention is also suitable here especially about an increase in pH when it reaches a certain level Worth suddenly to end.

b. If the process for the production of tin catalysts is carried out at a temperature of 100 ° C., tin oxide particles with a particle size of only 10% are deposited on the carrier surface. The effect of the increase in temperature corresponds to that which is found with the precipitation of ferrohydroxide .

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Claims (4)

PATENT CLAIMS 1. Process for the preparation of a catalyst, in which the catalytically applies an active substance in a finely divided state to an inert substance, that in a manner containing the catalytic substance Solution is suspended that homogeneous hydroxyl ions in the solution so slowly be formed that the migration speed of the to be felled Fabric to the surface of the carrier fabric is hollow enough to allow formation to avoid precipitation nuclei in the solution, so that the catalytic active substance exclusively on the suspended carrier in Form of a hydroxide or insoluble salt is precipitated, whereupon the so loaded carrier separated from the solution, dried, if necessary. glowed ' and is reduced, according to patent (patent application P 17 67 202.5) characterized in that the slow and homogeneous increase in hydroxyl ions is generated by stirring an alkaline Solution gradually into the suspension of the carrier in the solution of the injected catalytically active substance. ; 2. The method according to claim 1, characterized in that the addition of the alkaline Solution is sized so that the mean pH of the suspension during the formation of precipitation nuclei by a maximum of 0.1 unit in the Minute increases and the deviations from the mean course no more than 0.05 pH unit. 3. The method according to claim 1 or 2, characterized in that the measurement the pH of the suspension and the injection of the alkaline solution can be coupled to each other by programming. . . 4. The method according to 'claim I ₁ 2 or 3, characterized in that the alkaline solution is injected through a capillary ending below the liquid level of the suspension. 00 9837/18 50 Empty them