DE2445468A1 - HIGH TEMPERATURE RESISTANT, THERMAL INSULATING, CERAMIC MATERIAL - Google Patents

Description

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VOLKSWAGEN WEEK *. τ τ ν -τ ~

Corporation

318 Iolfsburg

Our symbols: K I769
1702-pt-we-hr

S.

High temperature resistant, heat insulating, ceramic material

The invention "relates to a high temperature resistant, heat-insulating, ceramic material, a use of such a ceramic material and a method for the production of a hollow body exposed to hot gases, in particular a housing of a reactor and / or a catalytic one Converter for exhaust gas cleaning systems of internal combustion engines made of such a ceramic material.

The object of the invention is to create a ceramic material that can be used as a housing material for the acted upon by the hot exhaust gases of an internal combustion engine Eeactors and / or catalytic converters for exhaust gas cleaning systems is suitable, which is therefore both high-temperature resistant and heat-insulating and that which occurs in such devices Reactions supported whenever possible. Another requirement of such a material relates to a relatively high strength to withstand the high mechanical loads that occur in such an application keep.

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To solve this problem it is proposed according to the invention that the ceramic material consists of a mixture of 30 to 60 volume percent aluminum oxide - (A ^ O =) - powder and 70 to 40 volume percent alumina-silicate fibers, which at temperatures from 1200 to I550 ⁰ G is sintered.

The ceramic material according to the invention has a relatively high strength and good insulating effect and is characterized by it also characterized by an extremely high thermal shock resistance, the it is particularly suitable for use as a housing material for reactors and / or catalytic converters for exhaust gas cleaning systems in internal combustion engines makes appear advantageous.

Appropriately, to increase the insulating effect and the strength, the mixture of aluminum oxide powder and alumina-silicate-3? Aern a proportion of 5 to 20 wt. ^ Zirconium silicate (ZrSiO ^) was added will.

Another feature of the invention is that the mixture catalytically active additives are added. These additives can consist of 1 to 10% by weight of one or more elements of the group Titanium, vanadium, chromium, manganese, iron, cobalt, nickel or copper, from one or more oxides of these elements or from others Connections of these elements exist. It is also possible to add a rare earth element or a precious metal the platinum group. The advantage of these catalytically active additives in the ceramic material is that through this promotes the reactions taking place in reactors and catalytic converters, with an early start-up in particular these reactions are particularly to be welcomed. In particular the group of non-noble catalysts, such as nickel, ITickeloxide, copper, copper oxide, Cromoxyd, Eisenoxyd, Mariganoxyd, Titanoxyd and others. have in Connection with the oxide-ceramic sintered materials has another great advantage. You can namely as a sintering aid

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as well as for setting some essential material properties.

An essential feature of the invention is therefore the use of the high-temperature-resistant, heat-insulating, ceramic material as a material for hollow bodies exposed to hot gases, in particular for the housings of reactors and / or catalytic converters in exhaust gas cleaning systems of internal combustion engines.

To produce such a hollow body from a high-temperature-resistant, heat-insulating, ceramic material, the invention further proposes that the mixture, optionally provided with an additive, of 30 to 60 percent by volume of aluminum oxide (Al20 ·,) powder and 70 to 40 percent by volume of alumina-silicate fibers is mixed with dnem glue or binder and is formed in a mold into a green body which is then sintered to the finished body in a furnace at temperatures of 1200 bx3 I550 ⁰ C for about 10-5) hours. In order to further increase the starting behavior of such reactors and catalytic converters, a catalytically active layer can be applied to the inner surfaces of the hollow body before or after sintering in addition to the catalytically active additives or instead of these additives. This layer can also consist of one or more elements from the group titanium, vanadium, chromium, manganese, iron, cobalt, nickel or copper, from one or more oxides of these elements or from other compounds of these elements as well as from a rare earth element or consist of a noble metal of the platinum group. In all cases, this catalytically active application has the effect that the light-off behavior of a reactor or catalytic converter produced according to the invention is very good and that the reaction taking place in these hollow bodies can be optimally maintained, so that

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the harmful ones present in the exhaust gases of an internal combustion engine Components "eliminated, v / able to ground.

The drawings provide examples of how to use the Material according to the invention as a housing material for reactors and kcitalytic converters in exhaust gas cleaning systems of internal combustion engines shown and explained in more detail below. Show in a schematic representation

Figure 1 shows a longitudinal section through a switched into the exhaust pipe of an internal combustion engine Reactor, the core of which is made of the ceramic material according to the invention exists and

FIG. 2 shows a longitudinal section through a catalytic converter and a thermal converter Reactor-containing hollow body made of the ceramic material according to the invention.

the

In the figure. 1, 1 denotes a reactor, / Tn the exhaust pipe of an internal combustion engine, in particular in a motor vehicle near the engine, is switched on. In this case, the reactor has, for example, a rectangular cross-section and has a core 2 made of the ceramic material according to the invention. by means of an elastic insulating layer 5 under compressive stress, for example made of an alumina-silicate fiber material. Flanges 6 for the inlet and a flange 7 f ^r are arranged the outlet of the Yerbrennungsgase to the outer housing 3, the through holes 8 and 9 correspond mi * corresponding openings 10 and 11 in the reactor core. 2 In order to reduce the residence time of the exhaust gases in the reactor core 2

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A transverse web 12 is provided in front of the outlet opening 11 which forces the exhaust gases to go around the web 12 through the side openings 15 of the reactor space to the? Outlet opening 11 to flow.

The reactor core shown in the drawing is made of two half-shells, each of which is in a styrofoam form made from a mixture of 50 percent by volume oC aluminum oxide powder (AlpO _5. ) And 50 percent by volume in the form of stuffing compound Alumina-silicate fibers were formed. After this raw form had been dried in an air circulation oven, the inner surfaces in particular were coated with a fine-grained aqueous throat made of Al ρ Oj powder with 5% by weight of C ^ Oz and 2% by weight of cobalt, for smoothing, but also for activation. The mixture consisting of molybdenum and chromium was coated. Once the inner coating had dried, the two half-shells were glued together with a mortar or binder and sintered in an oven at 1350 ° C. with a 10-hour holding period.

The ceramic hollow body manufactured in this way has a relatively good strength and good thermal insulation properties as well as extremely high thermal shock resistance. The particular The coating applied to the inside of the hollow body acts, among other things, as an activator that prevents the thermal Supports and stimulates the conversion reaction of the harmful components contained in the exhaust gases.

In FIG. 2 there is a ceramic material according to the invention existing hollow body shown, which in addition to a part with a catalytic converter a part with a thermal Reactor shows. Me outer wall 15 of the hollow body I4 has two Inlet openings 16 through which the internal combustion engine incoming exhaust gas enters. The outlet opening is labeled I7.

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Fig. 18 shows a partition dividing the case, which aji is theirs. Endea merges into transverse webs 19, the z \ -rischen and the housing end faces Include reduction zones 20. These reduction zones 20 can be provided by individual, spaced apart consists of lamellae formed from the housing material, which are coated with a catalytically active layer, for example a base metal catalyst, like ITickel, or a precious metal catalyst, like platinum, are coated. Instead of the lamellas, a separately manufactured, monolithic carrier body could also be introduced here be, which is also provided with a known catalytically active layer.

Immediately behind the reduction zones 20, the hollow body 15 has smaller inlet openings 21 for blowing in secondary air on. This secondary air takes place in the between the reduction zones 20 and the housing a / u si ritt I7 remaining seaktor space 22 a thermal reaction in which the remaining, so far unburned components of the combustion exhaust gases are oxidized will.

The hollow body shown in FIG. 2 can now have been manufactured from the same material and using the same method as the reactor core shown in the figure. However, a further example of the material according to the invention is given below. The base material consists of a mixture of 50 percent by volume of alumina-silicate fiber material, 40 percent by volume of O ^ -aluminum oxide (AI2O3) powder, 8 percent by volume of manganese oxide and 2 percent by volume of silicon oxide (SiO2) by volume, the hollow body is on the outside Inner surfaces, especially in the area of the reduction zone 20 and in the area of the thermal reaction space 22, are provided with a catalytically active layer, which can consist of a noble metal catalyst applied after firing or a base metal catalyst applied before firing. So an order from a watery one can be applied here before firing

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Slips can be used in addition to that of the basic mass of the materials containing the hollow body, additions of 5 "to 10% by weight of manganese oxide, copper oxide, iron oxide, chromium oxide and a mixture of carbon, molybdenum, silicon and chromium.

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Claims (7)

A Ή PROVERBS 1. High-temperature-resistant, heat-insulating, ceramic material, characterized by a mixture of 30 to 60 percent by volume aluminum oxide (Al2O3) powder sintered ^{at temperatures of 1200 to 1550 0 C?} and 70 to 40 percent by volume of alumina-silicate fibers, 2. Ceramic material according to claim 1, characterized in that the mixture has a proportion of 5 to 20 wt / S zirconium silicate is added. 3. Ceramic material according to claim 1 or 2, characterized in that catalytically active additives are added to the mixture. 4. Ceramic material according to claim 3 »characterized in that that the mixture an addition of 1 to 10 Gew.jS one or several elements of the group titanium, vanadium, chromium, manganese, iron, cobalt, hickel or copper, one or more oxides or other compounds of these elements is added. 5. Ceramic material according to claim 3 / characterized in that the mixture contains an addition of up to 3Gew.5 & an element which is added to the rare earths. 6. Ceramic material according to claim 3 »characterized in that the mixture contains an addition of up to 3 wt. $ £ of a noble metal is added to the platinum group. 7. Use of a high temperature resistant, heat insulating ceramic material according to one of claims 1 to 6 as 6098U / 1024 Material for hollow bodies exposed to hot gases, in particular for housings of heaters and / or catalytic converters in exhaust gas cleaning systems of internal combustion engines. Method for producing a hollow body exposed to hot gases, in particular a housing of a Reactor and / or a catalytic converter for exhaust gas cleaning systems of internal combustion engines, from einia high-temperature-resistant, heat-insulating, ceramic material according to one of claims 1 to 6; characterized, that the optionally provided with an additive mixture of aluminum oxide (ALGOO powder and alumina-silicate fibers is mixed with a glue or binder and shaped in a mold to form a raw body that then sintered in an oven at temperatures of 1200 to 1550 ° C for approx. 10-50 hours to form the finished body will. Method according to claim 8, characterized in that a catalytically active one is applied to the inner surfaces of the hollow body Layer is applied. 6098U / 102A