DE3143039C2 - Catalyst and process for its preparation - Google Patents

Abstract

A catalyst element should have high activity per unit weight and volume, low pressure losses of the reacting gas in the catalyst layer, high general and high surface strength, low activity changes over the exposure time and low costs. So that these requirements are met at the same time, the catalyst element is characterized by at least one core layer (1, 11) made of metal and by at least one holding layer (2, 12) applied to the core layer (1, 11), the holding layer (2, 12) contains or consists of a glass fiber material with catalytically active particles embedded therein. In a method for producing this catalyst element, the glass fiber material for the retaining layer (2, 12) is dipped into a dispersion containing catalytically active particles, then the excess is squeezed out and the retaining layer (2, 12) obtained in this way is attached to the core layer (1, 11) , the holding layer (2, 12) being dried and fired before or after being applied to the core layer (1, 11).

Description

The invention relates to a catalyst with a core layer made of metal and with at least one on the Core layer applied porous retaining layer which is loaded with a catalytically active component

Such a plate-shaped catalyst is described in DE-OS 29 27 246. The core situation here consists of a metal net on which a porous retaining layer, for example made of activated alumina or silica is applied by means of an inorganic binder. This holding layer is then catalytic with a loaded active component.

Such a catalyst only has a satisfactory strength if it has a relatively large wall thickness The space requirement is correspondingly large, especially if there are several such plate-shaped catalysts be arranged within a housing.

In addition, the use of the binder ensures effective diffusion of the reacting gas into the hindered catalytically active component, so that the activity of the catalyst per unit volume does not is optimal

The invention is therefore based on the object of creating a catalyst that is characterized by low Space requirement and high activity per unit volume

This object is achieved according to the invention by a catalyst of the type mentioned, in which the Holding layer contains or consists of glass fiber material, in which the catalytically active component is in the form is embedded by particles

The advantages of this catalyst are, on the one hand, that the core layer gives the catalyst a high gives mechanical strength On the other hand, the holding layer with the glass fiber material is able to provide a large Amount of catalytically active particles to keep without the addition of a binder, resulting in effective diffusion of the allows reacting gas through the interior of the catalyst with reduced pressure loss and a good contact between the gas and the catalyst is ensured, resulting in a high activity of the In addition, the materials are cheap and easy to obtain.

The retaining layer can contain glass fiber fleece, paper, mat, fabric and / or strands. If glass fiber strands are used, they should be roughened on the inside, especially frizzy or hairy be trained. Furthermore, the catalytically active particles should not be larger than 150 μm, preferably be between 1 and 10 μΐη.

According to a further feature of the invention it is provided that a protective layer is applied to the outside of the holding layer to prevent the catalytically active particles from being released from the holding layer so According to the different tasks of the two layers, the holding layer should be one have a comparatively large number of fiber gaps and the protective layer has a comparatively small number. Good combinations consist in that the retaining layer contains glass fiber fleece, paper or mat and the protective layer contains glass fiber fabric.

According to the invention, the method for producing the above-described catalyst is characterized by

indicates that the glass fiber material for the retaining layer is contained in a catalytically active particle

Dipped dispersion, then squeezed out the excess and the retaining layer obtained in this way on the The core layer is attached, the holding layer being dried and before or after application to the core layer

is burned. The fiberglass material should preferably also be rolled in the dispersion.

The invention is illustrated in more detail in the drawing using exemplary embodiments F i g. 1 shows a cross section through a catalyst in layer construction;

F i g. 2 shows a cross section through a further catalyst in layer construction; F i g. 3 is a view of a partially sectioned, columnar catalyst; F i g. 4 is a view of another, partially sectioned, columnar catalyst; F i g. 5 is a graph showing the relationship between the sludge concentration and that of particles held by the fiberglass material;

F i g. 6 shows a vertical section through a reactor;

F i g. 7 is a graph showing the reactivity and the selectivity at various reaction temperatures and

F i g. 8 is a perspective view of a reactor.

The catalyst according to the invention can be shaped in various ways. Figures 1 to 4 show typical ones Examples.

The catalyst according to FIG. 1 is produced in a layered construction. It has a core layer 1 in the form of a flat metal plate, which is preferably made of steel. On both sides of the core layer 1 are flat Retaining layers 2 with catalytically active particles embedded therein attached, specifically by means of retaining clips 3.

The in Fi g. The catalyst element shown in FIG. 2 is the same as that in FIG. 1 shown, but has additional protective layers 4 which are applied to the outside of the holding layers 2. The protective layers 4 prevent the catalytically active particles that are stored in the holding layers 2 from being released are.

F i g. 3 shows a columnar catalyst which has a cylindrical core layer 11 and a holding layer 12 Has incorporated catalytically active particles, which surrounds the core layer 11 and with this via retaining rings 13 is connected The in F i g. The structure of the catalyst shown in FIG. 4 corresponds to that in FIG. 3 shown, only that a protective layer 14 is additionally applied to the holding layer 12, which prevents the catalytically active particles from the holding layer 12 prevented

Glass fiber materials that can be used are, for example, nonwovens, paper, mats, fabrics or strands of glass fiber. This is primarily understood to mean the following:

Glass fiber fleece or glass fiber paper are flat sheets of glass fibers that are interconnected by means of a Adhesive are connected. Such webs are referred to as nonwovens when long fibers are used. They are called fiberglass papers when they contain short fibers.

Fiberglass mats are made from a bulky body made of fiberglass strands in a certain thickness is shaped.

Glass fiber fabrics are made from yarns by twisting a variety of glass fibers with diameters between 5 to 15 μm woven Plain weave, fine weave or satin weave are used as weaves in question. Strands of glass fiber are obtained from long glass fibers and are not twisted during weaving. All these fiberglass materials have fiber gaps in which particles can be held and which allow diffusion of the reacting gas.

Since glass fiber nonwovens, papers and mats have a large number of fiber gaps and since the individual ones Fibers can move easily relative to each other when they are exposed to external forces, they can be a contain large numbers of catalytically active particles. Accordingly, fiberglass fleece, paper and • mats suitable as glass fiber materials to form a retaining layer with catalytically active Particles to form.

In the fiberglass fabrics, the fibers are with much higher tension and with a smaller number of fiber gaps included. The individual fibers are also less able to move relative to one another therefore only hold a smaller number of catalytically active particles between them. However, the Particles are retained even when the tissue is exposed to vibrations, for example. Corresponding are glass fiber fabrics especially for use as a protective layer to prevent loosening of the catalytically active particles

Fabrics made from fiberglass strands are similar to conventional fabrics. Will be such a thing Fabric needled, brushed or subjected to a similar process, so it is roughened on one side, like this that a suitable surface for holding the catalytically active particles is created Glass fiber fabric is attached to the core layer with the roughened surface facing inwards Tissue both the function of the holding layer for the catalytically active particles and the protective layer for Prevent these particles from leaching out.

Usable catalytically active particles are those which are not larger than 150 μm. Are particularly preferred Particles in the order of magnitude between 1 and 20 μm, as they are easy to keep and in the glass fiber material are difficult to extract. Particles smaller than 1 μm are easier to remove, but still useful when no strong mechanical vibrations occur. Particles that are larger than 20 μm, are difficult to store in the fiber gaps in the layers, but they can be in sufficient numbers be introduced into the layers when the layers are pressed several times with rubber rollers like this will be described later.

In order to store catalytically active particles in the glass fiber material, the material is placed in a sludge, consisting of water or other useful dispersing agent and catalytically active particles submerged, the sludge having a viscosity of 100 to 1000 Cp. Advantageously, the glass fiber material pressed with rubber rollers in the mud in order to bring it into the fiber gaps and to close it cause the particles to hold well in the material. To remove the excess sludge from the fiberglass material squeeze it out between rubber rollers at a pressure of 5 to 30 kg per unit of length Roles passed through. The wet material is then applied to the core layer and there with help fixed by fasteners The glass fiber material fixed on the core layer is then dried w> and optionally burned. The fiberglass material can also be dried beforehand and only then on the Be attached to the core layer. In this case, however, the material generates dust during handling, see above that provision must be made for good environmental conditions.

Attempt 1

There have been different types of materials in terms of differences in the number of particles examined, which are held by a glass fiber fabric.

A glass fiber fabric was produced which has a thickness of 0.2 mm, a weight of 200 g / m ² and a yarn density of 19 yarns per 25 mm. It was woven from yarns each of which had a twist of 25 mm and each of 800 glass fibers with diameters of 14 μm were composed. Slurries of various concentrations were prepared by adding water particles of ^ -alumina on the order of between 30 and 75 μΐπ. Then a piece of glass fiber fabric in each of the slurry was dipped and washed twice with rollers pressed then were impregnated with the slurry fiberglass fabric pieces at 100 ° C for one hour, dried and calcined for three hours at 400 ⁰ C. The number of particles contained in the pieces of fabric was then measured.

The same treatment was repeated with the exception that instead of the y-alumina now Siücium-aluminum oxide or magnesium oxide particles were used, in the same particle sizes as the / alumina. The number of particles embedded in the tissue thus obtained was then measured a

The relationship between the concentration of the sludge and the number of particles contained in the glass fiber cloth was found for the respective types of the particles. In the graph of FIG. 5 are the results listed The graph shows that the number of the respective types of particles with the Sludge concentration increases

Attempt 2

Various types of glass fiber materials have been provided with catalytically active particles and the Checks for differences in the amount of particles picked up

The same glass fiber fabric as in Experiment 1 was initially used as the glass fiber material Water with magnesium oxide particles of the order of 30 to 75 μm to form a sludge mixed which has a concentration of 25% by weight. The glass fiber fabric was made in the same manner as treated in Example 1 to incorporate the magnesium oxide particles therein. Then the number of in that Particles contained in fiberglass fabric are determined

The same process was repeated, except that instead of the glass fiber fabric, glass fiber fleece, a glass fiber mat or a fabric made of glass fiber strands was used, in the latter case one side was roughened ^{by a needling process with 108 needles per cm 2.} Here, too, the number of magnesium oxide particles contained in each of the glass fiber materials obtained in this way was determined. Table 1 shows the results.

Table 1

Glass fiber material Art

Weight) (kg / m ³ )

Particle
Included
Lot")
(kg / m ³ )

Included amount / weight of fiberglass material

Woven non-woven mat, roughened strands

1000

600

80

470

035 037 8.1 132

*) Weight of the material per apparent volume unit of the material.
**) Weight of the particles per apparent volume unit of the Fesermsteriate.

example 1

Magnesium oxide particles were found in the same glass fiber fabric that had already been used in Experiment 1 stored in the same manner as in Experiment 2 The glass fiber fabric was then attached to the opposite sides of a stainless steel core layer which was 35 mm × 50 mm × 1.5 mm in size would have. In this way, a catalyst A was obtained in a layered construction, as shown in FIG. 1 is then shown Catalysts B, C and D were produced in the same way, except that instead of the glass fiber fabric, glass fiber fleece, glass fiber mats or fabric made of glass fiber strands were used, the latter was roughened on one side. The fabric made of fiberglass strands was the same as that of the Experiment 2 and was attached to the steel plate with the roughened side inward

Example 2

Magnesium oxide particles became in the same in fiberglass mat, fiberglass mat and fiberglass cloth In the same manner as in Example 1, the glass fiber fleece was then stored attached as holding layers to a steel plate serving as core layer. The glass fiber fabric with embedded magnesium oxide particles was placed over the holding layers in order to provide a protective layer to prevent the Leaching out the particles to form. In this way, a catalyst G was formed as in FIG. 2 is shown

Furthermore, a catalyst F was prepared in the same manner except that instead of the non-woven glass fabric as Retaining layers of fiberglass mats with embedded magnesium oxide particles were used.

Table 2 shows the thicknesses and weights of the layers of the above-described catalysts as well as those Amount of magnesium oxide particles in the layers.

Table 2

Kataly Holding layer weight Protective layer weight layer Amount of sators Fiber material (g / m ² ) Fiber material (g / m ² ) thickness*) Magnesium oxide 200 (mm) (g / m ² ) A. tissue ■ 300 - 0.2 110 B. fleece 400 - 0.5 260 C. mat 570 - 3.0 1900 D. roughened strands 300 - 200 1.2 260 E. fleece 400 tissue 200 0.8 380 F. mat tissue 3.1 1900

catalyst Magnesium oxide contained (g / m ² ) after 1 hour after 2 hours after 4 hours At first 90 86 84 A. 110 180 110 40 B. 260 1100 620 120 C. 1900 235 228 225 D. 260 345 330 321 E. J80 1550 1420 1400 F. 1900

*) Thickness of the holding layer or the combination of holding layer and protective layer

The catalysts A to F were tested with regard to their wear resistance.

The catalyst A was in the middle of a metal screen with a mesh size of 550 μm and a diameter fastened by 300 mm. 200 g of aluminum balls, each 5 mm in diameter, were placed in the sieve and then vibrated the sieve in an automatic sieve device for four hours at 200 Vibrations per minute and an amplitude of 30 mm. The one dissolved out of the catalyst Amount, measured after one hour, two hours, and four hours, to determine which was still in the catalyst to determine contained particles. The same procedure was carried out with Catalysts B-F. Table 3 shows the results.

Table 3

Table 3 shows that all the catalysts are able to hold the particles well

The catalysts A to F were subjected to a test with regard to their vibration resistance. The catalyst A was attached to a metal sieve with a mesh size of 2500 μm and was used for two hours Subjected to vibrations applied by a 50 Hz vibrator. The loosened particles were measured after half an hour, one hour and two hours to find out that those still in the catalyst to determine contained particles. The same procedure was carried out with Catalysts B to F as well Table 4 shows the results.

Table 4 '

Table 4 shows that all the catalysts have high vibration resistance.

Example 3

300 g of Λ-aluminum oxide particles, not larger than 75 μm, were placed in a solution of 11.8 g of ammonium metavanadate, 3.8 g of ammonium molybdate tetrahydrate and 8 g of oxalic acid in 130 g of water. The mixture was evaporated dry in vacuo at a temperature of 6O ⁰ C with stirring and then over three

catalyst Magnesium oxide contained (g / m ² ) after 7 ₂ hours after 1 hour 105 after 2 hours At first 108 145 100 A. 115 202 1400 83 B. 260 1620 248 1250 C. 1830 250 325 245 D. 255 350 1720 318 E. 390 1750 1700 F. 1900

Fired at 400 ° C. for hours. The product thus obtained was comminuted to convert catalytically active particles into to get the size 30 to 75 μm. Then, water was added to obtain a sludge having a concentration of 25% by weight.

A strip of glass fiber strands, which was roughened on one side and had a thickness of 1.2 mm, a width of 20 mm and a weight of 570 g / m ² , was immersed in the mud. The strip was pressed twice by means of rollers within the slurry. Then the strip soaked in this way was placed with its roughened sides inward around a steel cylinder 18 mm in diameter and 80 mm in length and fastened at the upper and lower ends. Then the strip was dried at 100 ° C for one hour and then calcined at 400 ° C for one hour, so that a columnar catalyst,

ίο as shown in Fig. 3, was created, with the glass fiber strands having a length of 60 mm. The amount of the particles contained in the layer was 240 g / m ² .

Like F i g. 6 shows, the columnar catalyst 22 containing 03 g of catalytically active particles was shown in FIG placed a tube 21 of a quartz reactor, the diameter of the tube 21 being 23 mm. The quartz reactor was kept at a certain reaction temperature. It was a gasoline-air-gas mixture with

A gasoline concentration of 0.8 to 0.9% was passed into the quartz reactor through the narrow pipe 23 at a flow rate of 60 standard l / h. After flowing through the large pipe 21, the gas mixture was collected Measure the amount of maleic anhydride formed by the oxidation of the gasoline. the the same procedure was repeated at different reaction temperatures. Furthermore, the procedure - also at different reaction temperatures - carried out with a gasoline-air-gas mixture that had a greater gasoline concentration of 1.2 to 13%.

For comparison, 0.9 g of aluminum oxide 300 grains from 1875 to 2500 μπι with 9 g of quartz glass grains likewise from 1875 to 2500 μm, mixed to obtain a catalyst in the form of small pellets. This was tested for its activity under the same conditions as above F i g. 6 also shows a heater 24, a molten salt bath 25 and a thermocouple 26.

The reactivity and the selectivity were determined on the basis of the measurements described above in the respective reaction temperatures determined according to the following equations:

eit = ( 1 -

Responsiveness = ( 1 - gasoline concentration of the outflowN _χ V gasoline concentration of the inflow /

SI kf 'ft - amount of maleic anhydride (mol / h) ™ amount of reacted gasoline (mol / h)

The results are shown in FIG. 7 They show that the columnar catalyst according to Example 3 is much better than the pellet catalyst, both in terms of reactivity and in terms of selectivity

Example 4

A sludge consisting of 30 parts _{by weight of TiO 2 of} the anatase type and with particles no larger than 75 μm and 70 parts by weight of water was mixed with sulfuric acid so that a pH of 2 to 3 was established. Then ammonium metavanadate was added in an amount of 0.05 atomic ratio based on T1O2. The mixture was stirred at room temperature for five hours to dissolve the ammonium metavanadate in the sludge and _{adsorb the vanadate radical on the TiO 2} , so that a TiO ₂ sludge was formed, which retains the vanadium in it. A fabric made of glass fiber strands with a weight of 300 g / m ^{2 was} immersed in the sludge and pressed twice with rollers measuring 50 mm 29 mm χ χ 03 mm fixed at 150 ⁰ C for one hour, dried and then burned for three hours at 40O ⁰ C, so that a catalyst g in layer construction, as shown in F i g it. 1 shown was created.

Catalysts H to N were prepared in the same way, except that instead of the glass fiber strands, the * Glass fiber materials ~ listed in Table 5 below were used. The roughened glass fiber strands were applied to the steel plate in such a way that the roughened side came to lie inside.

Table 5

Catalyst fiberglass needling / cm ² *) G strands (300 g / m ² ) 0 H raised strands (300 g / m ² ) J 62 I raised strands (300 g / m ² ) 216 J strands (570 g / m ² ) 0 K raised strands (570 g / m ² ) 108 L raised strands (570 g / m ² ) 216 M fleece with 0.8 mm thickness (300 g / m ² ) - N fabric with a thickness of 0.2 mm (200 g / m ² ) -

*) The number of needles for roughening.

Comparative example

100 parts by weight of TiO ₂ powder with particle sizes up to 44 μm and a weight per unit area of 150 m ² / g were mixed with 100 parts by weight of colloidal silicon oxide, which contained approximately 20% by weight of SiO ₂ and acted as a binder, to form a sludge obtain. This sludge was applied to both sides of a metal net 5, which had a mesh size of 83 μm, had a size of 30 mm by 50 mm and consisted of steel wire with a diameter of 0.5 mm, then it was dried at 100 ° C. for one hour and then at Fired at 400 ^° C. for three hours.

In this way, a TiO _{2 support was formed} on the wire mesh in the form of a 0.8 mm thick plate. The plate was immersed in a 2N oxalic acid solution of ammonium metavanadate (1.0 mol / l) at room temperature for 10 minutes, then pulled out of the solution and then dried at 100 ° C. for one hour and then at 400 ^° C. for three hours Fired A catalyst O was created, which carried the catalytically active components on the metal mesh.

As in Fig. As shown in Fig. 8, in a cavity-type stainless steel reactor 32, three catalysts were placed 33 lined up one behind the other. They were held in place by metal nets 34 A 6 mm χ 30 mm channel 31 of the reactor 32 became a test gas of the composition shown in Table 6 with a flow rate of 13 l / min under normal conditions to increase the activity of the catalyst to test for reducing NO with NH3.

Table 6 20

Component volume ratio

NO about 150 ppm

NH3 about 150 ppm 25

H ₂ O 10%

CO ₂ 10%

O ₂ 5%

N ₂ balanced

In this way, the catalysts G to N and the catalyst O were tested for their activity at different reaction temperatures in order to determine the value K , which is defined as follows:

K = ~ (AV) xln (\ - x)

35 where:

Volume flow of the reaction ^{gas (Nm 3} Zh)
geometric surface of the catalyst (m ² )

x = NO responsiveness
The relationship between a K and the amount of TiO ₂ was found. Table 7 shows the results.

Table 7 45

Catalyst amount TiO ₂ 200 ⁰ C 250 ⁰ C 300 ° C 350 ° C (g / nvO

G 62 10.3 29.8 47.8 69.0 50

H 265 30.7 66.4 98.9 132

I 305 32.1 67.9 100 137

$ J 70 10.9 28.2 41.4 54.1

K 362 35.1 67.0 103 141

L 361 36.7 73.4 122 172 55

M 120 17.5 42.2 70.0 99.5

\ & N 65 9.8 243 36.2 47.3

O 400 123 26.3 40.9 49.4

g Table 7 shows that the catalysts G to N of Example 4 have a higher K value per amount of 60

■ is TiO ₂ and have a higher activity than the catalyst O of the comparative example.

- In addition 3 sheets of drawings

Claims (3)

Patent claims: 1. Catalyst with a core layer made of metal and with at least one applied to the core layer porous retaining layer, which is loaded with a catalytically active component, thereby characterizing indicates that the holding layer (2.12) contains or consists of glass fiber material, in which the catalytically active component is embedded in the form of particles _ 2. Catalyst according to claim 1, characterized in that on the outside of the holding layer (2, 12) a Protective layer (4, 14) is applied to prevent the catalytically active particles from being released, wherein the holding layer (2,12) and the protective layer (4,14) a large number of fiber gaps ίο have. 3. A method for producing the catalyst according to claim 1 by applying at least one with a catalytically active component loaded, porous holding layer on a core layer made of metal, characterized in that the glass fiber material for the holding layer (2, 12) in a catalytically active Particle-containing dispersion dipped, then squeezed out the excess and so obtained ne holding layer (2,12) is attached to the core layer (1,11), the holding layer (2,12) before or after after being applied to the core layer (1,11), it is dried and fired.