DE1023015B - Process for the manufacture of catalysts - Google Patents

Description

Process for Making Catalysts The invention relates to a process for the preparation of hard shaped catalysts from difficult to reducible ones inorganic oxides by grinding the corresponding, in non-gelatinous form present oxide hydrates in a colloid mill or an equivalent device, which allows the required degree of crushing, compression molding and calcining.

This process is characterized in that the grinding of the optionally partially calcined hydrated oxides of aluminum, beryllium, thorium, Magnesium, silicon or mixtures of these hydrated oxides takes place until practically complete comminution to a particle diameter of less than 40, u with a specific surface area of at least 60,000 cm2 / cm3, preferably less than 25 u with a specific surface area of at least 65,000 cm2 / cm3 is reached.

The use of compression molded beads made from certain inorganic Oxides in their so-called catalytically active or adsorptive form, e.g. B. off catalytically active aluminum oxide, beryllium oxide or from compounds such as z. B. silica-alumina, is well known in catalysis. These Beads can themselves be used as catalysts, e.g. B. silica-alumina for cracking hydrocarbons, or they can act as a carrier for others catalytically effective materials are used. So are z. B. Catalytically active beads Beryllium oxide or aluminum oxide, which is associated with various metals, such as platinum, ruthenium, Palladium, nickel, copper, cobalt, chromium or mixtures of these metals, impregnated useful for carrying out many reactions such as oxidation, hydrogenation, Desulfurization, hydrocarbon conversions and many others.

In making these spherical catalysts, one is the Main problems in the art of producing globules that are sufficiently hard and resistant are against abrasion to withstand severe handling conditions. With some Types of use is z. B. a catalyst bed of finely divided beads more permanent Exposed to movement and vibration, resulting in constant hard knocks and rubbing of the Cause globules among each other and on the walls of the container. This is true z. B. for known moving bed and fluidized bed processes in which the catalyst is constantly moved through different zones for reaction and regeneration. In this type of use, the beads must also be subjected to a fairly high level of pressure Can withstand the essential from the use of catalytic layers Thickness stems from. Another example where the resistance of the beads to mechanical wear is of great importance, the use is spherical Oxidation catalysts to detoxify the exhaust gases of internal combustion engines during their operation, especially when a catalytic muffler is installed on a vehicle is.

According to a known production method, shaped catalysts are used made from inorganic oxides by using a gelatinous gel, e.g. B. aluminum hydroxide gel, precipitated from an aqueous solution, some of the free water without destruction the gelatinous character is removed and then the gelatinous mass is extruded or otherwise formed into beads to the desired dimensions cut, then dried and activated.

Another method of making beads from catalytic active alumina and similar active oxides, the oxide is a fine powder with a suitable lubricant and binder, usually a waxy one organic material, mixed, and then made by tableting on one of the well-known tablet machines formed beads from this mixture. Because the poor cohesive properties of such a powder has generally been not considered feasible to extrude the oxide in powder form.

There were already hard, porous, adsorptive and catalytically active ones granular masses produced by adding jelly or granular precipitates or their Dry products in the presence of so much liquid of a strong mechanical Were subjected to treatment so that a homogeneous, thin paste was formed. This was then optionally dried after previous molding.

In this process, hydrates, oxides and carbonates can be used in general be used. The grinding is carried out in a ball mill; Because of this Processes cannot, however, be those claimed according to the invention critical Particle sizes less than 40 sb with a specific surface area of at least 60,000 cm2 / cm3 can be obtained, because the mere grinding of the material into a thin, homogeneous paste does not give this degree of division, even if in one Ball mill is ground infinitely long. With catalysts that only come from this thin, homogeneous paste is produced, the increase in hardness is not achieved, which occurs according to the invention.

In the methods described above and other previously used methods The difficulty was usually in finding globules with good hardness and good Establish resistance to wear and tear. It is the purpose of the present invention to create a solution to this old problem by having an economic one and reliable method for producing such shaped catalyst pieces with the desired physical properties is created.

According to the invention, a mass is compression molded which has the oxide in at least potentially active, but not gelatinous, and in a critical form Contains degree of fine distribution. The degree of fine distribution of the oxide in the mass, from which the cylindrical bits are molded is of critical importance for the physical properties of the bits, especially their hardness and theirs Resistance to abrasion.

It is equally decisive for the shape of the mass, especially their ability to be extrudable well. If the for the invention If the process has achieved a substantial degree of fine distribution, one occurs unexpectedly sudden improvement in the compressibility of the oxide and physical properties the cylindrical bricks, in particular their hardness.

The oxide is marked in its required degree of fine distribution due to a relatively high specific surface, which is largely due to particles with a diameter less than 1, and by the absence of more than insignificant percent by weight of particles larger than 40 c. The finely divided material must have a specific surface area of at least 60 000 cm2 / cm3 and should preferably have a size of at least 65,000 cm2 / cm3. It must consist essentially of 100 percent by weight of particles less than 40 in diameter and should preferably contain particles less than 25µ in size.

Any device or technique can be used for particle size reduction which causes the required degree of comminution and the catalytic Properties of the starting material are not deteriorated.

Preferably, at least the last stage of particle size reduction is used carried out with a wet milling process, which is best used if the material is already as a relatively fine powder (e.g. through a 100 mesh sieve passes through or is even finer) and in a liquid agent, preferably is suspended in an aqueous medium. A method that is found to be particularly effective was found, is the so-called colloid milling process, in which a liquid sludge, preferably an aqueous slurry of the starting material between closely spaced located surfaces is guided, with at least one of the surfaces rotating rapidly and thereby subjects the material to shear stress. When using a Such a comminution technique is the degree of comminution required according to the invention achieved with at least 50 weight percent of particles from about 0.01 to 2 size exist. With a particle size distribution of this type, the specific Surface of the material approximately 60,000 or 65,000 cm2 / cm3.

The above-mentioned colloid milling method, which will be detailed below is described, has the advantage that it allows a very intensive treatment, without the starting material being significantly contaminated with foreign bodies during the comminution becomes contaminated.

It is most desirable to use a milling process in which the intensity of the crushing forces can be increased while the Comminution progresses. A less intensive shredding technique, such as B. the usual ball mill process, does not give the required degree of comminution. Such a less intensive process can, however, be preceded by a more vigorous crushing be applied.

The digit values used in the description for particle size and specific Surface areas indicated were determined by a combination of sediment analysis and electron microscopic examination as described in the examples below will.

According to the process according to the invention, molded articles are made from catalytically effective, difficult to reducible inorganic oxides produced, d. H. from oxides, which are not reduced in the hydrogen stream at temperatures of 260 °. materials of this type are aluminum oxide, beryllium oxide, zirconium oxide, thorium oxide, magnesium oxide and silica, including their combinations and compositions, such as alumina-beryllium oxide, Aluminum Oxide-Zirconia, Alumina-Silica. The invention is special advantageous for the production of moldings made from catalytically active aluminum oxide consist, or from compositions of catalytically active aluminum oxide with catalytically active forms of other oxides of the group.

The hydrous form of these oxides (hydrated oxides) is not essential catalytic activity, although it is considered to be potentially active, because of it the anhydrous or partially anhydrous catalytically active by calcination Shape can be made.

As mentioned above, must be the mass that makes up the cylindrical bits be compression molded, the finely divided oxide in at least potentially more active, but does not contain gelatinous form. The oxide must already be present in this form, if the comminution by a mechanical comminution process, e.g. B. a Wet milling process. Suitable starting materials for such a Comminution processes involve a fully hydrated form of the oxide, such as. B. aluminum oxide trihydrate, as well as partially or almost completely activated forms of the oxide, such as a partially or almost completely anhydrous aluminum oxide hydrate, which is produced by the controlled calcination of the water-containing form. That However, the starting oxide must not have a gelatinous character; H. in such Cases where the hydrated oxide, e.g. B. aluminum hydroxide gel, produced by precipitation the original gel must have evaporated dry in order to do this essentially remove all loosely bound water that was present in the original gel and such a hydrated but not gelatinous form, such as. B. aluminum oxide trihydrate, to manufacture.

In some cases it has been found desirable that the mass from which the pieces are molded, the finely divided oxide in an intermediate degree contains the calcination, d. H. in a shape that, by removing a part, but not all chemically bound water is preserved. This is especially true in the formation of pieces consisting mainly of aluminum oxide, whereby the alumina particles are preferably 5 to 20 percent by weight of that in the original Trihydrate contain chemically bound water. If alumina trihydrate is used, are the malleability of the mass and the quality of the finished moldings in general preferably. For the comminution itself it has in most cases been found to be desirable but not found essential, the use of highly calcined oxides, from which the entire chemically bound water down to a fraction of a percent removed, as such oxides are quite hard; this is particularly true for alumina or silica-alumina too; the crushing process becomes this makes it more difficult and expensive.

After the oxide has been crushed to the required particle size it may be compression molded into bits of any desired shape by any known method will. According to the most common and preferred method, the bits from a moist mass of finely divided oxide with an appropriate consistency compression molded. If the comminution is by wet milling in an aqueous suspending medium is carried out, the desired moldable consistency can be easily obtained, by exposing the resulting aqueous sludge to evaporation is, with the evaporation conveniently in some sort of milling device, preferably with heating. It is important that the material during the Evaporation is kept in a homogeneous state in order to avoid local drying, which would result in a final molding compound with a non-homogeneous moisture content.

Preferably, the bits are formed by extrusion, there this compression molding method generally provides moldings with excellent hardness and is usually considerably more economical than other processes.

For extrusion purposes, the bulk of the finely divided oxide is preferred brought into the consistency of a dough. The best moisture content for making a mass with the best extrusion properties and for the production of cylindrical Moldings with the best physical properties will vary somewhat depending on the relevant oxide. In general, the mass suitably has a moisture content from about 15 to 35 weight percent (humidity determined by heating to constant weight at 121 "). In order to obtain hard, dense briquettes, the mass can be extruded under considerable pressure, pressures of at least about 10.50 kg / cm2 and preferably higher, e.g. B. 35 kg / cm2 to 210 kg / cm2 is desirable are. One of the most convenient ways to determine the correct moisture content of the dough in each particular case is to vary the amount of liquid until the desired extrusion pressure is obtained. The lower the moisture content is, in general, the higher the extrusion pressure required.

According to a particularly preferred embodiment of the invention becomes a compound dissolved in water, such as aluminum nitrate, which is absorbed by heat their corresponding oxide can be decomposed into the finely divided oxide before the Compression molding incorporated homogeneously. This can be done if the oxide is wet-milled in a aqueous suspending agent was comminuted by dissolving the decomposable compound in the aqueous sludge obtained at the end of the grinding process, take place. The desired shape consistency is produced by subsequent evaporation. So z. B. an aqueous slurry of alumina particles, which on the required Fineness are ground, aluminum nitrate crystals are added; the mix will stir until the aluminum nitrate is dissolved; then the mixture is under constant Stir and shake by adjusting their liquid content to the required Brought shape consistency. The moist aluminum oxide dough containing the aluminum nitrate can be heated to 204 to 260 ° after drying to convert the aluminum nitrate into To decompose aluminum oxide. The broken compound has, when decomposed, evident the effect of binding the oxide particles since it was found that the hardness and the Wear resistance according to this particular embodiment of the invention Process produced cylindrical moldings are influenced very favorably.

The compound to be incorporated into the finely divided oxide should be im generally converts easily into a catalytically active oxide of the type that the invention affects, decompose and dissolve relatively well in water. Water soluble aluminum salts strong acids such as aluminum chloride, aluminum sulfate and especially aluminum nitrate are preferred for this purpose. Water-soluble salts, especially those stronger Acids that are easily decomposable into beryllium oxide, thorium oxide or magnesium oxide, can be used in some cases. Bring the nitrates of the metals mentioned usually the best results due to their relatively low decomposition temperature.

Care should be taken to ensure that the amount of aluminum nitrate used or other similar compounds is not too large for the salt to be in solution remains when water is evaporated to achieve the required shape consistency. The formation of crystals in the molding dough interferes with the compression molding process. For example it was found that the addition of one part by weight of Al (NO3) 9 H2O to 10 parts an aqueous sludge containing equal parts by weight of aluminum oxide and water, gives excellent results, while an addition of 1.8 parts by weight A1 (N 3 9H2O to the same sludge a crystallization of the aluminum nitrate during the Evaporation resulted in an unsatisfactory result.

After compression molding, the wet bits can be mixed with any suitable Process to be dried. In general, the best results will be obtained if dried so that the free moisture is relatively slow and at a relatively low temperature is removed. After drying, the cylindrical Briquettes are generally heated to about 260 to 816 "for several hours, thereby improving their quality.

If a compound that decomposes in the heat, such as aluminum nitrate, is worked into the oxide before compression molding, a heat treatment is necessary, to decompose the compound into its corresponding oxide. A heat treatment is of course also necessary to achieve an active catalyst if that Oxide molded in a non-activated or only partially activated form will. In the production of briquettes, for example, one that is precipitated at the same time Silica-alumina gel which has been completely dried to remove the water of gelation to remove, but which has not been calcined to remove the chemically bound water to remove the shaped pieces at a temperature of e.g. B. 704 "heat treated.

Example 1 5 kg of a partially calcined alumina hydrate in powder form are mixed with enough water to make sludge. That The well flowing aluminum oxide powder used shows the following sieve analysis: 1000 /, go through a 150 mesh sieve; 50 to 60 0 /, stay in one 300 mesh sieve back. The powder has the following composition: Al2O3 ..................... 90.2% Na2O3 ..................... 0.43% Fe2O3 ................... .. less than 0.36% Sio2 ..................... less than 0.18% Bound water ........ 9.1% This mixture is passed several times through a colloid mill, with the sludge is kept homogeneous by stirring.- The colloid mill used contains a rotating one Disc rotating at a speed of 20,000 revolutions per minute, while the mud is pumped between them and the stator.

The original mixture is made a total of 8 times through this mill directed. During the first pass, the clearance between the stator and rotor is increased set to about 0.013 cm. During the subsequent rounds this will be Game set to zero, d. i.e., the disks are opened with considerable force pressed against each other so that in the absence of the film of sludge pumped between them, acting as a lubricant would be in direct contact. The crushing in this mill is done through a combination of hydraulic shear stress and friction.

A sample of the sludge was taken after each run and Set aside for investigation.

These samples have been numbered from 0 to 8, accordingly the starting sludge and the sludge after the first, second, third, etc. pass through the mill.

The will change during the first five passes through the mill Viscosity of the sludge not significant; the sixth round was a considerable one Increase in viscosity noted; the mud had the flow properties of a thick syrups. In the seventh and eighth pass, the viscosity increased even more further, and the mass assumed a soft consistency, similar to that of a mortar.

As the particle size reduction progressed, the tendency towards phase separation increased steadily from until in the samples from the last two or three passes through the Mill containing about 50 weight percent water (the solids content was made by Drying of the sludge at 93 to 121 °), even after a long period of time There was only a very slight phase separation.

The distribution of particle sizes in the samples from the third to eighth pass through the mill (samples 3 through 8) was made using Stoke's Law for the settling rate of the particles suspended in a liquid. A typical procedure using this method is in the ASTM Standard (1952), Part 3, published by the American Society for Testing Materials, pp. 1420 bis 1430 (ASTM designation: D 422-51). This method is also in kaolin Clays and Their Industrial Usese, published by J. M. Huber Corporation, New York, N.Y., p. 99.

The results of the sediment analyzes carried out with this method for samples 2, 4, 5, 6, 7 and 8 are shown in Figure 2 of the drawing where each Curve with the sample number it represents.

These curves are plotted on a semi-logarithmic scale, where weight percent is plotted against the log of particle size in microns.

Since it is assumed in measurements according to Stoke's law that the Particles having a spherical shape can be relatively large if they deviate from the spherical shape Errors occur when the particles examined by the sediment method are smaller than 2 µ. Since the described in the Way crushed particles considerably deviate from the spherical shape and in some cases the shape of rather thin platelets appear to have the particle size of this material as determined by the sediment method was determined not entirely reliable, and therefore that is part of every curve shown in Fig. 2 under 2 lt as a broken line.

For precise determination of the distribution of particle sizes in the area below 2 l an electron microscope examination of samples 3 up to and including 8 performed with a 10470 and 32500 times magnification. The object for the Electron microscopes were made as follows: a drop of 0.2% polyvinyl formaldehyde resin in ethylene dichloride was mixed with two drops of a sample and the mixture Rubbed between a pair of glass strips for about 15 seconds by pulling the Strips moved towards one another with a rotating movement with light finger pressure became. Electron microscopic photographs were taken of the samples thus prepared made. All particles in the field that were observed at 10,470x magnification, were counted with the particles having a diameter of 0.037 liters or larger measured and in groups with a diameter within a determined range were sorted. A sufficiently large field was examined so that 250 or more Particles per sample could be measured.

The smaller particles were measured at a magnification of 32,500 times. Based on these observations, the percentage of particles in each group versus the total number of particles counted was determined. These percentages are given in the table below: Table I Size percentage of particles the Particles in each group (hop in the Sample group # Sample'Probe Sample Sample Sample in microns 3 4 5 6 7 - 8 2 0.037 83.31 35.93 42.75 31.53 49.15 11.24 3 0.053 3.95 14.30 4.25 24.00 2.90 15.20 4 0.075 2.35 16.10 8.00 18.00 6.60 19.00 5 0.107 3.30 10.70 8.50 10.00 10.00 19.40 6 0.150 2.25 10.50'7.50 6.10 9.20 - 18.00 7 0.215 1.78 4.30 8.50 3.50 8.90 6.20 8 0.300 1.26 3.00 6.60 2.90 4.70 6.30 9 0.430 0.70 2.07 4.80 2.30 3.90 2.40 10 0.600 0.43 0.98 2.70 0.76 2.70 1.20 11 0.850 0.48 0.48 1.13 4.30 0.46 0.90 0.53 12 1.2 0.19 0.66 1.40 0.30 0.30 0.34 13 1.7 0.27 0.12 0.70 0.15 0.45 0.19 14 2.4 0.09 0.12 - # 0.15 - 15 3.5 # 0.04 - - 0.15 - 16 4.75 0.09 - # 09 - From the figures in Table I, the distribution of the particle sizes in samples 3 to 8 for the range below 2 l was determined by calculating the weights of the particles in each group below 2 l and relating them to the entire sample, the value for the total weight of the particles below 2 liters was taken from the results of the sediment analysis. For sample 5 e.g. B. the sediment analysis (Fig. 2) shows that about 52 percent by weight of the material consists of particles of less than 2 μ in size. The distribution in this 52% can be determined by knowing the weights of the particles in each group below 2 lt. The distribution curves determined in this way for particles below 2 lt in size were combined with those for particles over 2 lt in size, as determined by the sediment analyzes (solid part of the curves in FIG. 2); these combined curves are shown in FIG. A comparison of FIG. 1 with FIG. 2 shows that the sediment analyzes for particle sizes below 2 liters give higher values than the electron microscope analysis.

With the curves in Fig. 1, the specific surface area of the material in samples 4 through 8, expressed in square centimeters of particle surface area per Cubic centimeters of volume determined by gradual graphical integration of these curves using the relationship: 60,000 specific surface area in cm2 / cm3 = Dt Dt is the particle size in microns; the specific total surface area for each Sample is the sum of the part surfaces that are inside using the above equation small particle size ranges can be determined along the curve. This method To determine the specific surface area, it is assumed that each particle is spherical or cubic shape with a diameter or side equal to Dt and represents of course only the outer geometrical surface of the particles and not that Inner surface created by pores and cracks. Specific surface determination other methods can result in slightly different numerical values.

The values determined in this way for the specific surface for the samples 4 to 8 are plotted against the sample number in FIG. 8; Curve 18 shows the relationship in which the specific surface area with successive passes through the colloid mill varies.

The lower dashed part of the curve is extrapolated. The curve shows that the specific surface area is in a relatively constant ratio enlarged with successive passes through the mill.

To show the improvement in extrudability and hardness, obtained by crushing to the required degree was carried out, each of the nine samples (Samples 0 to 8) was in the following Ways examined: any sample containing approximately equal amounts of water and alumina was divided into 2 parts. One part of each sample became 1 part by weight A1 (NO3) 9 9 H2O added to 10 parts by weight of the water-aluminum oxide sludge and stir vigorously until the aluminum nitrate crystals dissolve completely had.

Each of the 18 samples was then placed in a blender, where it was constantly being stirred while a stream of hot air ran over it for so long Surface was blown until the sample took on a dough-like consistency and one Dry solids content from 75 to 80 percent by weight.

The dough thus obtained from each part of each sample was then each made Brought by itself into a hydraulic press, in which an attempt was made to make the dough through to extrude an extrusion die with a 0.3175 cm diameter opening. The extrusion pressures varied from about 10.5 to 35 kg / cm2. The extrusion cord the round hole shape was cut into pieces approximately 0.3175 cm long. These Bits were dried, and those bits removed from the portion of each sample, containing dissolved aluminum nitrate, were heated to 232 °, to decompose the aluminum nitrate into catalytically active aluminum oxide.

In an attempt to extrude the dough made from the samples that had not passed through the colloid mill or only a few times only part of the material filled into the cylinder before the extrusion die through the shape to be pressed; the rest of the Materials tightly stuffed into shape in the cylinder a hard, non-plastic mass which is subjected to adequate extrusion pressure could not be extruded. Most of the moisture that is in that the original dough filled into the cylinder was used with the material that left the extrusion die, pushed out so that the hard one in the cylinder remaining mass was almost dry.

For the samples that had run through the colloid mill more often, however, essentially all of that filled in the cylinder prior to the extrusion die Material extruded with good success.

Fig. 4 graphically shows the improvement in extrudability which obtained by the colloid method. An equal amount of each part the sample was filled into the cylinder in front of the extrusion die and it was in In each case, an attempt was made to obtain this measured amount in pieces of 0.3175 cm Extruding diameter. In each case, the lump yield was from this measured amount of dough at a compression pressure of approximately 70 kg / cm2 in percent by weight certainly. Curve 10 shows the results obtained with the samples, which contained only aluminum oxide and water, while curve 11 shows the results obtained from the portion of each sample to which aluminum nitrate was added was. As can be seen, an essentially 1000 / ge yield was only obtained of the dough that was made from the last three samples and in which the particle size reduction occurred had been carried out sufficiently far.

The device that was used to measure the hardness of the bits To determine, consisted of a knife blade at one end of a spring tension scale that was hinged to the other end of the blade. The piece was placed on a plate near the middle of the blade length and the force measured that it was necessary to cut it diametrically. From every part everyone The sample was examined for five pieces and the values obtained were averaged. These Numbers are shown graphically in FIG.

Curve 13 relates to moldings from those samples which contained only water and alumina, while curve 12 represents the force that is necessary to the addition of aluminum nitrate from the extrusion dough cut through the resulting moldings. From Fig. 5 it can be seen that only one there was little improvement in hardness when the alumina was only up to that for Sample 5 had been crushed in the typical condition, and that from that point onwards the Hardness increased rapidly, especially-in the last three samples.

The information plotted in FIG. 5 also clearly illustrates the Effect of the aluminum nitrate. The moldings made from the aluminum nitrate containing Made dough and later used to decompose the aluminum nitrate into aluminum oxide Heat treated are many times harder than the briquettes that are made from it only Dough containing water and alumina was made.

The moldings prepared as described above are useful for many applications in the field of catalysis, especially where hardness and Resistance to abrasion are important. Excellent oxidation catalysts can e.g. B. be produced by impregnating the aluminum oxide moldings with various metals, such as-platinum, palladium, silver, nickel, copper, etc. Most convenient the impregnation is known to be achieved by immersing the moldings in a Dissolving a salt of the metal and decomposing the salt. So z. B-. according to the invention produced aluminum oxide moldings with a 1 percent by weight aqueous Impregnated solution of chloroplatinic acid and then the platinum compound in metallic Platinum are decomposed. Such catalysts can, for. B. used to the unpleasant oxidizable components of exhaust gases from internal combustion engines, which include a number of hydrocarbons and oxidized organics, as well as carbon monoxide contain to oxidize. In such an application, the catalyst becomes one exposed to strong and constant vibration and mechanical shocks acting on the catalyst bed transmitted through the machine and the moving vehicle. Under these Conditions produced according to the invention are much more permanent than manufactured by previous methods.

Example 2 A beryllium oxide calcined at 600 ° in powder form with the following composition BeO. ......... ........ 93.02% Fe .......... 0.053 % Al ... 0.343 01o Si ........ 0.059% Mn 0,. .... 0.0764 0 / o Ni ........... 0.0045% Insoluble substances ...... 0.081 0 /, Bound water ......... 5.21 01o (loss when heated) was mixed with the same amount of water to form a slurry. This slurry was passed through a colloid mill as in Example 1 a total of 7 times. Samples were taken after each run, as was the starting sludge. These samples were designated with the numbers O-A to 7-A. With progressive shredding there was approximately the same increase in viscosity and constant decrease in the tendency Phase separation as in Example 1. Samples 5-A, 6-A and 7-A had the shape a soft paste, similar to Samples 7 and 8 in Example 1.

The distribution of particle sizes in Samples 3-A, 5-A, 6-A and 7-A was determined by sediment analysis as in the example; the results are in Fig. 3 of the drawing. As can be seen from these curves, crushed the beryllium oxide is slightly faster, so that sample 3-A is essentially the same The degree of fineness is shown as sample 5 in FIG. 1.

To demonstrate the degree of comminution required according to the invention The hardness and malleability obtained from each sample were beryllium oxide moldings such as Prepared as follows: Any sample (0-A through 7-A) at approximately 42.8,010 solids (Rest of water) was divided.

To a part of each sample were 10 01, their weight aluminum nitrate crystals, Al (N 03) 2 9 H2 0 are added and the mixture is stirred vigorously until the aluminum nitrate is complete was resolved.

Each part of each of the eight samples was then evaporated brought by liquid to the doughy consistency suitable for molding. The so The dough obtained from each sample was then individually placed in a hydraulic Introduced extruder with a nozzle opening of 0.3175 cm diameter. The extrusion cord the round hole shape was cut into short pieces approximately 0.3175 cm. These Bits were dried and those that were made from the dissolved aluminum nitrate containing portion of each sample were cut to approximately 232 ° heated to decompose the aluminum nitrate into aluminum oxide. The percent sentence the yield of moldings was determined for each sample by comparing the weight of the moldings determined with the material remaining in the extrusion cylinder as a hard mass. Curve 14 (Fig. 6) shows the results obtained with the beryllium oxide and water only containing portion of each sample were obtained, while curve 15 shows the results with represents the samples containing aluminum nitrate. As can be seen, an im substantial 100% yield of moldings was only obtained from samples 3-A onwards. As already stated and as can be seen from a comparison of FIGS. 2 and 3, shows sample 3-A essentially the same degree of fineness as sample 5 in the example 1.

The hardness of the chips produced from each sample is shown in Fig. 7 shown. Curve 16 shows the hardness of the moldings that are made from the molding dough containing only beryllium oxide and water, and curve 17 die Hardness of the bricks from those samples to which aluminum nitrate was added. The hardness the pieces were determined as in Example 1. As can be seen from these curves, the comminution causes an increase in the hardness of the moldings from very small ones Values in the first few runs to relatively high values in the later runs, whereby the hardness no longer increases or only increases insignificantly if the required The degree of fineness is reached approximately between samples 3-A and 5-A.

Example 3 A silica-alumina hydrate gel produced by coprecipitation, which contained about 1 part of Al 2 O 3 per 7 parts of SiO 2 was dried, but not calcined. This relatively finely divided material was mixed with so much water that that a sludge with about 30 weight percent solids was formed. (The solids content was determined by evaporation of the water at 121 °.) This mixture was repeated passed through a colloid mill by the same method as in Example 1.

The crushing was carried out to the point where the fineness of the material was the same as that of Samples 7 and 8 in Example 1. The watery one Sludge after the final pass through the colloid mill was approximately 34 percent by weight dry solids and had a slightly syrupy consistency. If this material evaporated to a dry solids content of about 45 weight percent it took on a soft paste-like consistency and showed little or no no tendency to separate into two phases when standing for a long time.

This material was then used for extrusion under constant working through evaporated further until a doughy consistency was obtained. The extrusion mold had a round nozzle orifice approximately 0.3175 cm in diameter. Of the Compression pressure was between 35 and 56 kg / cm2. The cylindrical extrusion was cut into pieces about 3 to 4 inches long, initially in one open bowl overnight at room temperature and then in one for 2 hours Oven dried at 121. The chips were then heated to 704 ° in. For 2 hours heated in an electric oven with exclusion of moisture.

With the briquettes produced in this way, knife tests were similar to the described in Example 1 carried out. For cutting through these silica-alumina moldings an average of 2.029 kg of force was required. Try to find the material which had not been ground to the required degree of fineness to be extruded, were unsuccessful.

Provide silica-alumina moldings of the type described here highly active catalysts for cracking hydrocarbons of great hardness and Abrasion resistance.

Claims (4)

PATENT CLAIMS: 1. Process for making hard shaped catalysts from difficult to reducible inorganic oxides by grinding the corresponding, Oxydhydrates present in non-gelatinous form in a colloid mill or a equivalent device that enables the required degree of disintegration, Compression molding and calcining, characterized in that the grinding of the optionally partially calcined hydrated oxides of aluminum, beryllium, thorium, magnesium, Silicon or mixtures of these hydrated oxides takes place until one is practically complete disintegration to a particle diameter of less than 40lt with one specific surface area of at least 60,000 cm2 / cm3, preferably less than 25 p is reached at a specific surface area of at least 65,000 cm21 cm3. 2. The method according to claim 1, characterized in that the comminution takes place in the wet milling process, in the resulting aqueous sludge a water-soluble, by heat in aluminum oxide, beryllium oxide, thorium oxide, magnesium oxide, or silica decomposable compound dissolved, then the moisture content of the aqueous sludge adjusted to achieve a consistency suitable for compression molding, and that after compression molding, the moldings are dried and heated so far that the water-soluble compound decomposes. 3. The method according to claim 2, characterized in that the by Heat decomposable compound a water soluble aluminum salt, preferably one strong acid, especially aluminum nitrate. 4. The method according to claim 1, characterized in that the inorganic Oxide is a partially calcined alumina hydrate which is 5 to 20 percent by weight contains chemically bound water. Considered publications: German Patent Specifications No. 664 817, 706 826.