DE19705490A1 - Easily manufactured catalyst assembly for exhaust gases comprising ceramic substrate with mineral and noble metal coatings - Google Patents

Abstract

The catalyst assembly for automobile exhaust gases and/or the exhaust of other internal combustion engines can be used for flue gases from industrial plant. The catalyst segment(s) (6) include gas flow passages (7) within the substrate body (9). The substrate body (9) is coated with catalytically-active material (8). In the new construction, the substrate, at least near the periphery, comprises predominantly cyclo-silicate and fibre-free mineral materials. These are selected from hydrous mica, rhyolite or porphyry. They form mouldings with the aid of binders and modifiers. Modifiers change the thermal capacity or thermal conductivity, being additives such as graphite, carbon, stone flour, fireclay grog or fireclay. The mouldings are subjected to gas flowing through and around them. Also claimed is the method of manufacturing the catalyst.

Description

According to a first inventive concept, the invention relates to a light catalytic converter for ka talytical conversion of flowing gases, in particular car exhaust gases and / or smoke gases sen of internal combustion engines and / or industrial plants, with at least one of the gas pas Catalyzable and / or washable, preferably provided with through-flow recesses sator segment, the best of predominantly heat-insulating, fiber-free mineral substance has base body with a surface-enlarging and catalytically active Be Layering is predictable, and goes according to a further inventive idea on a preferred Process for the production of such a catalyst.

The base body of the currently most common catalysts is a fired ceramic mono lith or as a metal sheet packing. In the ceramic moldings mentioned there is Danger of Span during large temperature fluctuations during operation Suffer from cracks, which are intensified by vibrations sooner or later to "trickle" the Kata lysators can lead. In addition, the ceramic monoliths due to lack of toughness in Occurrence of mechanical shocks are at risk of breakage. Have catalytically coated metal bodies the disadvantage that in addition to the relatively high weight, both in the cold and in the hot Can corrode condition, resulting in the typical "growth" of the metal catalyst in continuous operation tors leads.

In addition, due to the increasingly strict exhaust gas legislation, it is necessary that the Catalysts reach their operating temperature very quickly. Another disadvantage of both carriers In this regard, the relatively unfavorable physical characteristic data with regard to speci thermal capacity i. V. m. to see the thermal conductivity which leads to the heating up zen of the respective catalyst to operating temperature, especially in the cold start phase, still relatively takes long.

Another disadvantage of both types of carriers currently common is, for example, that in use ster G 92 10 010.4 based honeycomb or cellular structure of the carrier body. This The shape of the carrier limits the amount of the catalytically active coating that can be taken up due to the small duct cross sections and the inevitable increase in the exhaust gas counter pressure.  

Proceeding from this, it is therefore the object of the present invention to use a catalyst gangs mentioned type while avoiding the disadvantages described with simple and cost cheap means to improve so that not only a high resistance to Temperaturbe stresses and mechanical shock loads as well as high corrosion resistance and self-sustainability, but also rapid heating of the catalytic coating low weight with low pressure loss, no risk of clogging due to high loading quantities of coating and exhaust gas particles are guaranteed. Furthermore, a purpose moderate process for the rational production of a catalyst according to the invention will.

The first object is achieved in that the base or carrier body at least in the area its periphery mainly from minerals from the hydro mica group (e.g. Batavit, Jefferisit, Biotite, vermlculite, phlogopite) and / or the group of rhyolite or quartz porphyry glasses (e.g. Perlite) exists with the aid of binders and / or the heat capacity or the Thermal conductivity changing additives such. B. graphite, coal, rock flour, Scha moth or the like are processed into molded parts. This molding part just described rial is referred to below as mineral material.

The base body made of this mineral material forms the comparatively light, elastic core, of the catalyst segment, which can achieve a porosity of up to 90%. The coating, consisting of surface-enlarging oxides and catalytically active components when penetrating deeply into the pores ending on the surface, which creates a strong mutual network base body and coating.

The mineral material consists predominantly of layered minerals that form a shaped body be sealed. This molded body thus has a structure that is figuratively resembles a lightly compacted pile of leaves. The big advantage here is that induced Thermal stresses in this structure can relax completely without damage and thus completely is insensitive to the effects of thermal shock.

The strong interlocking of the layered minerals also results in considerable ver Improvement in the risk of breakage of the beams.  

The specific weight of this mineral material is approx. 0.6-0.8 g / cm and is therefore up to three times lighter than ceramic and up to nine times lighter than metal.

Since this mineral material consists of minerals, there is also a corrosion attack as with the Me tall carriers not possible.

Due to the formation of moldings of any geometry can be used today Honeycomb or cellular structure can be deviated and in contrast a turbu lent flow through the catalyst carrier can be realized.

But the biggest advantage of this new mineral material is that it is one to thirty has lower thermal conductivity with a comparable heat capacity as ceramic. This means that the overlying catalytically active coating is heated up very quickly can without too much energy in the cold start behavior to the insulating carrier material is delivered. In return, this means that once the carrier of the invention was driven hot, it remains hot for a significantly longer time after the engine has been switched off. Due to the high pore content due to the mineral material structure, the isolating we intensified.

The technical progress described allows a long service life for the kata according to the invention lysators and thus a high level of reliability and security and overall an excellent Expect economy.

Advantageous refinements and appropriate further training of the higher-level measures are specified in the subclaims. So can be useful for the formation of the base body Vermlculite and / or inorganic pearlite are used. These materials have both each individually as well as in combinations the required thermal, corrosive and mechanical resistance without further ado.

This mineral material advantageously becomes base segments with a high level of self-support ability shaped. For particularly robust applications, it can be useful if the base contains at least one support insert surrounded by the mineral material.

Another expedient measure can be that the input and / or from a baffle plate is arranged upstream or downstream of the base or catalyst segment on the aisle side. This  catches the impulse of the gas arriving or leaving the catalyst, whereby the individual base or catalyst segments are relieved, so that even when using very thin mineral material carriers a good fatigue strength is achieved.

The measures according to the invention can be particularly expedient in connection with realizing flat basic bodies. These can therefore be designed like plates or disks be what a simple parallel or series arrangement of several side by side or behind one another which enables placed base or catalyst segments. It is therefore possible in a simple manner Lich to offset the flow-through recesses so that the gas flowing through results in good contact with the catalytically active surface. They also enable this Measures a modular structure. With the sizes of the flow recesses can in addition, the pressure loss can be set very precisely to a minimum.

The disadvantages of the prior art described at the outset are therefore advantageously eliminated Technology completely eliminated.

The inventive solution of the procedural part of the task is that the mine ralmaterial through a shaping process to a preferably with passage recesses Provided base body is formed, which then with a surface enlarging and catalytically active coating is provided, preferably at least one tempera turbo treatment is provided. The shaping of mineral material with subsequent Drying results in self-supporting, stable moldings. Then the already mentioned Be layering and another temperature treatment, which increases the adhesion of the coating the carrier material is reinforced.

Further advantageous refinements and expedient further training of the higher level are specified in the remaining subclaims and from the example below removable spelling.

Fig. 1 shows a possible schematic representation of a motor vehicle exhaust system with a catalyst of this invention,

Fig. 2 shows a partial longitudinal section through a catalyst according to the invention

Fig. 3 is a partial view of a catalyst segment according to the invention

Fig. 4 is a plan view of a schematic, cube-shaped carrier or catalyst module composed of several base or catalyst segments

Figure 5 is a partial longitudinal section according to the invention of a further example.

Fig. 6 shows a partial longitudinal section through a catalyst according to the invention with axially arranged support or catalyst segments.

Fig. 7 is a plan view of another type of application.

Catalysts are used for the catalytic conversion of pollutants from exhaust gases. The basic structure and mode of operation of catalysts are known per se and need no further explanation in the present context.

The exhaust system on which FIG. 1 is based contains a catalytic converter 2 installed in a pipeline 1 , to which a silencer 3 is arranged. The catalytic converter 2 has a tubular housing 5 which is provided with an inlet and outlet cone 4 and which is fitted with disk-like or plate-like catalytic converter segments 6 arranged one behind the other at a distance. Likewise, the individual catalyst segments 6 can also be integrated in the muffler 3 , as is schematically outlined under 3a.

The disk-like or plate-like catalyst segments 6 are, as can best be seen from FIGS. 2 and 3, preferably provided with slot-shaped throughflow recesses 7 . Other geometries of the segments are possible as shown in Fig. 5, 6 and Fig. 7 is shown. The clear flow cross section of the passage recesses 7 first decreases in Fig. 2 to achieve a Ven turieffektes in the flow direction and then increases again. In contrast, in the embodiment according to FIG. 1, the housing 5 is designed like a venturi nozzle, so that the outside diameter of the catalyst segments 6 increases and decreases. This creates in combination with the cylindrical outer shell of the catalyst 2 a, an air gap or structure-borne noise insulation or a heat shield 2 b. In the embodiment of Fig. 2, the catalyst successively arranged segments 6 have the same diameter, so that a cylindrical housing 5 a is obtained. Here, only the lengths of the slot-shaped throughflow recesses 7 are graduated from one another or, in the simplest case, brought to the same lengths, as is indicated by dashed lines in FIG. 7 a.

The through-flow recesses 7 of successive base or catalyst segments 9 and 6 are preferably offset from one another or designed differently to bring about a deflection of the flowing gas. In the example shown with essentially the same or geometrically similar, slot-shaped throughflow recesses 7 , this can be achieved in a simple manner in that the successive segments 6 and 9 are rotated relative to one another by a certain angle. The through-flow recesses are not tied to any particular geometry.

As can best be seen from FIG. 3, the catalyst segments 6 are provided on their surface with a catalytically active coating 8 applied at least in one step. This is, in a manner known per se, an oxidic coating which has a large surface and which can contain or contain additives (promoters) which increase the catalytic activity. Catalytically active metals, preferably noble metals, are applied to the chemically reactive BET surface. Aluminum oxide or a mixture of this oxide with other metal oxides can be provided as the surface-producing material. So-called "asorber materials" such. B. zeolites are possible as coating materials 8 for the inventive carrier.

Base bodies 9 are provided to accommodate the coating 8 described above and thus to produce catalyst segments 6 according to the invention. These consist of mineral material as already described. Vermlculite and / or perlite are preferably predominantly used for this.

To increase the strength, a support insert 10 embedded in the mineral material can be provided, as indicated by a broken line in FIG. 3. In the example shown, this is a heat-resistant and corrosion-resistant metal plate provided with the flow-through recesses 7 assigned to recesses 7 . Another material would also be conceivable, e.g. B. ceramics in the form of cordierite, corundum, mullite or the like.

The base or catalyst segments 9 and 6 are, as FIG. 2 further shows, received on their circumference in a socket 11 and fixed by this to the housing 5 a. The individual base or catalyst segments are supported with so-called swelling mats 11 a or aluminum oxide strips 11 b in the respective sockets 11 . The housing 5 a can also consist of deep-drawn parts (z. B. two half-shells), which already have the sockets 11 molded. The deep-drawn parts are preferably welded or mechanically z. B. connected to each other by positive locking. The distances between the individual base or catalyst segments 9 and 6 from one another can be selected as desired.

As shown in FIG. 2, the inlet-side base or catalyst segment 9 or 6 is preceded by a baffle plate 15 , which is also provided with throughflow recesses. A baffle plate 15 can also be arranged on the output side in order to prevent the last segment from breaking out. The baffle plate 15 can be fixed to the housing 5 a by welding etc.

The cube-shaped carrier or catalyst module on which FIG. 4 is based consists of a plurality of, preferably four, plate-like, square elements 9 a and 6 a, respectively, which are added side by side as well as one behind the other and surrounded by the catalyst housing. The through-flow recesses 7 of the segments 6 a and 9 a are preferably rotated against each other ver. Segments 6 a and 9 a arranged one behind the other can in turn also be rotated against one another, as a result of which a desired exhaust swirl can be achieved. The structure of such a catalyst module acc. Fig. 4 corresponds practically to the structure of the catalyst of the example described above. Fig. 2. Individual modules can in turn be attached to one another and / or one behind the other. Arrangements of the type on which FIG. 4 is based are particularly suitable for plants which require large catalyst cross sections or volumes. However, due to the modular design, the size of the modules to be manufactured remains limited.

To form a catalyst segment 6 or module acc. FIG. 4 of the type described above is based on base parts 9 as carriers for the coating 8 . Mineral material is used to produce the base parts 9 as already described. As mineral material, as mentioned above, inorganic mineral material comes into question, preferably predominantly vermiculite and / or perlite. As a suitable binder for the minerals, water glass and / or metal aluminum phosphate and / or chemically or mechanically hydrated metal oxides can be used. A corresponding amount of mineral material is then sealed in or by means of molds, e.g. B. by injection molding or by simple stamping or rolling. It is also conceivable to suck the molded body by means of a vacuum suction process. The blank thus shaped is dried until the mechanical transport strength is reached. However, it would also be conceivable to connect the mineral material to one another by heating it to the sintering point in the pressed state.

The coating is then carried out in at least one step. This can be done by spraying, dipping, flooding and / or rinsing or pouring over. To dry the coating 8 follows a temperature treatment. Upon further tempering, the carrier and the coating are further solidified, which improves the adhesion. Due to the porous surface of the base body 9 made of mineral material, a reliable connection of the coating 8 with the base body results.

In another possible embodiment according to the invention, as shown schematically in FIG. 5, the base or catalyst segments 9 and 6 are installed in a curved exhaust pipe profile 17 analogous to FIG. 2 in the exhaust gas stream to be cleaned. The exhaust gas stream 18 coming from the engine follows the curvature, is catalytically cleaned in it and leaves the catalytic converter on the outlet side 19 . This type of catalytic converter enables even better utilization of the installation space geometries in front of a small amount of space.

The individual base or catalyst segments 9 and 6 can have different strengths and shapes from one another in a catalyst according to the invention and can be coated both with different coating types and catalytically active metal types and with different coating amounts and catalytically reactive metal amounts. This has the advantage that, on the one hand, the different axial temperature profile in the catalyzer between the gas inlet and the gas outlet can have differently effective individual segments 6 for converting the flue gases or exhaust gases.

In contrast to the preceding examples, in the embodiment according to FIG. 6 the plate-like elements 20 , 21 are arranged axially, preferably parallel to the flow direction 22 of the flue gases or exhaust gases. For intensive gas mixing and for mutually supporting the individual elements 20 , 21 , these have spacers 23 integrated through the shape and extending transversely to the direction of flow. By varying the position and the shape of these pins 23 , the clear gas flow cross-section can be changed as desired in order to be able to cope with a wide variety of exhaust gas or smoke gas situations.

Fig. 7 shows schematically the plan view of a further possible arrangement of the individual Ba sis or catalyst segments 9 and 6 in the exhaust stream 18, 19.

Claims (22)

1. Catalyst for the catalytic conversion of flowing gases, in particular car exhaust gases and / or flue gases from internal combustion engines and / or industrial plants, with at least one catalyst segment ( 6 ) which is passable by the gas and preferably provided with throughflow recesses ( 7 ) and which has a base body ( 9 ) which can be provided with a catalytically active coating ( 8 ), characterized in that, at least in the region of its periphery, the base body ( 9 ) consists predominantly of ring-silicate and fiber-free mineral material which belongs to the group of hydro mica and / or the group of rhyolites or Porphyry comes from and with the help of binders and / or the heat capacity or the thermal conductivity changing additives such. B. graphite, coal, rock flour, chamotte, clay or the like is processed into moldings so that it is installed in the gas stream to be cleaned, that the mold parts around and / or between them the flow paths for the gas to be cleaned. 2. Catalyst according to claim 1, characterized in that the mineral material at least one or more of the following minerals such as Batavit, Jefferisit, Biotit, Phlogopit, Ver contains miculite, liparite, rhyolite or pearlite. 3. Catalyst according to one of the preceding claims, characterized in that the base body ( 9 ) contains at least one support insert ( 10 ) surrounded by the mineral material. 4. Catalyst according to claim 3, characterized in that the support insert ( 10 ) made of ceramic and / or metal, preferably a stainless, temperature-resistant Stahlle alloy. 5. A catalyst according to claim 3 and / or 4, characterized in that the support insert ( 10 ) is plate-like. 6. Catalyst according to one of the preceding claims, characterized in that an impact plate ( 15 ) is provided on the input and / or output side. 7. A catalyst according to claim 6, characterized in that the baffle plate ( 15 ) consists of ceramic and / or metal, preferably a stainless, temperature-resistant steel alloy. 8. Catalyst according to one of the preceding claims, characterized in that the mineral material forming the base body ( 9 ) according to claims 1 and 2 compresses and / or by means of a binder, preferably in the form of water glass and / or metal aluminum phosphate and / or chemically or mechanically hydrated metal oxides, is bound and / or with the help of the heat capacity or the thermal conductivity changing additives such. B. graphite, coal, rock flour, clay, chamotte or the like is processed into molded parts. 9. A catalyst according to one of the preceding claims, characterized in that a plurality of catalyst segments (6, 6 a) are / spaced plate-like base body (9) next to and or behind one another, wherein the serially-arranged catalyst segments (6, 6a) in each case at least one Have throughflow recess ( 7 , 16 ) and the catalyst segments ( 20 , 21 ) arranged laterally next to one another flank the throughflow paths running between them and / or are also provided with throughflow recesses. 10. A catalyst according to claim 9, characterized in that the catalyst segments ( 6 , 6 a) are arranged next to each other and / or one behind the other with any spacing, spacers ( 23 ) being provided between adjacent catalyst segments, which are preferably formed before. 11. Catalyst according to one of the preceding claims, characterized in that the flow cross-sections of the catalyst segments ( 6 , 6 a) arranged next to and / or one behind the other are preferably out of alignment. 12. Catalyst according to one of the preceding claims, characterized in that that the clear flow cross-section preferably changes in the direction of flow or in Flow direction remains the same over the entire length of the catalyst. 13. Catalyst according to one of the preceding claims, characterized in that the catalyst segments ( 6 , 6 a) of at least partially surrounding sockets ( 11 ) are fixed. 14. Catalyst according to one of the preceding claims, characterized in that the individual catalyst segments ( 6 , 6 a) can be installed along non-linear Abgaska channels ( Fig. 5). 15. Catalytic converter according to one of the preceding claims, characterized in that the catalyst segments ( 6 , 6 a) can also be combined with silencers ( Fig. 1). 16. Catalyst according to one of the preceding claims, characterized in that the catalyst segments ( 6 , 6 a) are designed as modules ( Fig. 4) which can be attached to one another to form larger modules. 17. Catalyst according to one of the preceding claims, characterized in that the base body ( 9 ) according to claim 1 and 2 within an overall catalyst can have different strengths, through-flow recesses, distances from one another and geometries. 18. Catalyst according to one of the preceding claims, characterized in that the base body ( 9 ) according to claim 1 and 2 each have different surface-enlarging and / or adsorbing coating quantities and / or types of coating. 19. A catalyst according to claim 17 and / or 18, characterized in that the Ba siskkörper ( 9 ) according to claim 1 and 2 each different from each other catalytically active Me tallarten and / or amounts of metal, preferably at least partially contain noble metals. 20. Catalyst according to one of the preceding claims, characterized in that a structure-borne noise ( 2 b) and / or air gap insulation ( 2 b) and / or a heat shield ( 2 b) is attached to the outer shell of the catalyst. 21. A method for producing a catalyst according to any one of the preceding claims, by the base body ( 9 ) in one or more steps with an aqueous acid or basic surface-enlarging oxide dispersion, which can also contain the active at least partially noble metal components or only in a further step in the form of Edelme tall solutions are applied, by means of spray, immersion, flooding, suction and / or pouring process coated, dried and tempered, characterized in that the mineral material for the shaped body according to claim 1 and 2nd mixed with binder and is formed by a shaping process into base bodies ( 9 ) provided with at least one flow-through recess ( 7 ) and can contain support inserts ( 10 ) to improve the mechanical stability of the base bodies ( 9 ). 22. Catalyst according to one of the preceding claims, characterized in that the base or catalyst segments ( 9 ) or ( 6 ) on their circumference with so-called swelling mats ( 11 a) or aluminum oxide strips ( 11 b) in the respective sockets ( 11 ) are stored.