DE19945742C1 - Exhaust gas catalytic converter comprises a fabric consisting of metal and/or catalyst fibers produced by melt extraction - Google Patents

Abstract

Catalyst structure for purifying exhaust gases from internal combustion engines comprises a woven, knitted or nonwoven fabric consisting either of: (i) metal-catalyst alloy fibers produced by melt extraction; or (ii) separate metal and catalyst fibers, one or both of which are produced by melt extraction. An Independent claim is also included for a process for producing fibers for such a catalyst structure, comprising: (a) melting the metal and/or the catalyst material, or a mixture of the metal and catalyst material; (b) drawing threads from the melt; and (c) cooling the threads to form fine fibers.

Description

The invention relates to a metal fiber catalyst body for Cleaning exhaust gases from internal combustion engines, which is a tissue Contains knitted or fiber flow from metal fibers, being Kata lysatormaterial contained in the metal fibers or even in Form of fibers present in the fabric, and a method for Manufacture of fibers for this catalyst body.

There are various catalysts for cleaning exhaust gases known from internal combustion engines. These have the task Pollutants such as carbon monoxide, nitrogen oxides, and hydrocarbons substances to remove from the exhaust gas flow. For this, the Pollutants oxidized or converted chemically, so that Kohlendi oxide, water and nitrogen remain as reaction products. The one that causes and accelerates these chemical reactions For effective exhaust gas purification, the catalytic converter must have a large surface area per catalyst volume the. The catalysts are mostly from a carrier plant fabric, for example kerami with fine channels cal monoliths made on the for further enlargement a so-called washcoat is applied to the surface again coated with the catalytically active material is. Precious metals are generally used as catalyst material, such as platinum, palladium or rhodium, or oxides of various base metals such as chromium, molybdenum or vanadium set.  

The exhaust gas purification by means of catalysts starts at one agreed exhaust gas temperature, from about 250 ° C. At these tem temperatures that occur during driving, can then up to over 90% of the pollutants are removed. At Operating temperatures above 550 ° C can damage the cataly occur because thermal overheating to sinter the Coating leads.

Since at low temperatures during the warm-up phase to reach the reaction temperature, the exhaust gases almost unhealthy cleans the exhaust leaving, are u. a. electric heater elements provided that the catalyst to its starting temperature heat the door.

The wear of the thin kataly is still problematic table-like coating that extends the life of the Kataly limited and thus exhaust gas detoxification.

In EP 0 364 153 A1 a metal is used as the catalyst material lichen network of fibers proposed, made of a noble metal such as platinum or made of precious metal alloys. On Catalyst body that has wires or fibers that or multilayered as a woven, braided or knitted fabric are known from DE 40 22 937 A1 where the wires or fibers by sintering or welding at least are partially connected. Catalytically active Materials can be coated on the fabric be angry, or even form this. A similar one ches braid is proposed in DE 42 21 763 A1, at materials with a catalytic effect by sintering or applied to the braid by flame spraying or ka metallic powder in an oxidation process  is oxidized. This is intended to increase the catalytic converter r surface. Another method of opening bring catalytically active materials onto a Kataly Satorträger is known from DE 42 00 995 A1. Here will a honeycomb gas adsorption element first with a Impregnated dispersion of particles of the catalyst, wherein after drying, the spaces between the particles of the catalyst tors and the fibers evenly with a dispersion of one impregnated and dried organic binder. This ensures that the catalyst particles are firmly bonded with the catalyst carrier instead.

Finally, DE 40 12 719 A1 is made of fiber mats or cotton wool filter for exhaust gas cleaning known in diesel engines, which is also used as a carrier for oxidation and reduction catalysts can be used. The Kataly Sator material is applied to the filter in finely divided form applied, but it can also in the surface of the company sermaterials themselves, whereby the removal of catalys goal material should be significantly reduced. For implantation ren of catalyst material in an adsorptive layer is the known sol-gel method in DE 44 23 329 A1 suggested.

The known catalysts using metal fiber braids have several disadvantages. When coating with the catalytically active material is abrasion of the coating and a sintering in the event of thermal overheating is inevitable, so that the life of these catalysts is limited. With the previously known techniques Precious metal fibers have an unfavorable ratio of effective mer surface to the volume used, whereby the Effective catalyst reduced and unnecessarily much catalyst  material is wasted. Will the catalyst particles by means of implantation or by means of other common molten metal urgent processes are introduced into the catalyst carrier Observe inhomogeneities, segregation and segregation.

The object of the present invention is therefore an effective one To propose long-life metal fiber catalyst bodies which avoids the disadvantages mentioned, and a method for Production of a company suitable for such a catalyst to specify. The catalyst obtained is said to be close to the burner room of the internal combustion engine can be attached without to be damaged by thermal overheating.

This object is achieved by the features of Pa Tent claims 1 and 5 solved. Advantageous configurations each result from the subclaims.

In the metal fiber catalyst body according to the invention, this can Catalyst material either contained in the metal fibers be or even be in the form of fibers. In the first case the metal fibers consist of a homogeneous alloy of Catalyst material with the catalyst support material, the are produced by melt extraction. It is established from that the known melt extraction process ago is outstandingly suitable for the production of such fibers. in the Contrary to the other known melt metallurgical Ver driving surprisingly, no segregation or seige occurs and the homogeneity of the alloy remains long-lasting receive.

During the melt extraction, a rotating, multi-bladed roller is immersed in a melt pool, with melt threads being pulled out of the melt pool at the edges of the roller. The filaments solidify very quickly at the edges of the water-cooled roller and are separated from it by the centrifugal force. In the case of alloys, the melt extraction usually works under a protective gas atmosphere or vacuum in order to prevent oxidation and slag formation on the surface of the weld pool. In addition to the type of alloy, the diameter and speed of rotation of the roller and the temperature of the melt pool and the roller are factors which determine the length and thickness of the metallic fibers and their homogeneity. Very thin metallic fibers with a diameter of less than 100 μm can be produced, which solidify into fibers with a temperature gradient of 10 ⁵ K / s over time. With this rapid cooling, segregation is not possible.

In the case of a catalyst body in which metal fibers and fibers of catalyst material can be connected to a fabric Fibers produced according to the invention by melt extraction be used. Leave the very thin metallic fibers works particularly well with known textile techniques Further processing, knitting or fiber flow and on because of their large reaction surface directly as a catalyst insert.

Another great advantage of the catalyst according to the invention body is that the homogeneous catalyzed gate material has a high temperature resistance where through it in an area of the engine near the burner chamber, in the Combustion chamber itself or in the exhaust manifold can be attached. Since the exhaust gases are very hot in this area, the Start temperature of the catalysis immediately after the start of the Motors reached so that the ent in the warm-up phase emissions are drastically reduced.  

Is preferably suitable as a temperature-resistant material Iron and / or nickel, which as a corrosion-resistant material Chromium and / or aluminum is added. As a catalyst material al are also the well-known elements platinum, paladium, Rhodium and other precious metals as well as chrome, molybdenum, vanadi um, manganese, etc. and their oxides can be used.

The catalyst body according to the invention can be in the form of Hoses, stockings, pipe inserts, mats or the like Structures used in or near the combustion chamber the.

The advantages over the known solutions can be as summarize as follows: space requirement and weight of the fiction Moderate catalyst body are significantly reduced, with none Abrasion or other signs of wear over the driving tool life can be determined. The exhaust emissions in the warm-up phase of the internal combustion engine are considerably reduced set. Preheaters for the catalyst during the Warm-up phase of the engine can be omitted. Because the catalyst material in pure form or as a homogeneous alloy with the me metallic carrier material is present, there is a high temperature Resistance to damage, damage or failure of the catalytic converter prevents thermal overheating.

In the following, exemplary embodiments are to be described with reference to the attached th drawings illustrate the invention in more detail.

Fig. 1 shows a catalyst body according to the invention in the Kol benboden the combustion chamber of a motor vehicle.

Fig. 2 shows the catalyst body according to the invention as a tissue in the manifold of the motor vehicle exhaust.

Fig. 3 shows a tubular catalyst body in the exhaust manifold of a motor vehicle.

In Figs. 1 to 3 of the combustion chamber 2 and the manifold are shown schematically of an exhaust of a motor vehicle 3, wherein the metal fiber catalyst body according to the invention 1 in Fig. 1 in the piston head of the combustion chamber 2 near the exhaust manifold 3, in Fig. 2 in the exhaust manifold 3 , filling this as a fabric, and in Fig. 3 also in the manifold 3 as a tubular catalyst structure. In the latter variant, the exhaust gas is passed through a deflection surface 4 to the inner surface of the manifold 3 through the tubular catalyst fabric 1 .

The high temperature resistance and the lack of coating in the catalyst body 1 according to the invention enable its arrangement in or near the combustion chamber 2 , so that the exhaust gas poisoning can start immediately when the motor vehicle is started and not only after a warm-up phase.

Claims (9)

1. Metal fiber catalyst body for cleaning exhaust gases from internal combustion engines, which contains a fabric, knitted fabric or fiber flow made of metal fibers, catalyst material contained in the metal fibers or even present in the form of fibers in the fabric, characterized in that
that the catalyst material in the metal fibers forms a homogeneous alloy produced by melt extraction, or
that the metal fibers and / or the catalyst fibers each form thin fibers produced by melt extraction. 2. A catalyst body according to claim 1, characterized net that the metal fibers from a corrosion and tempara resistant alloy, preferably iron and / or contains nickel and / or chromium and / or aluminum. 3. A catalyst body according to claim 1 or 2, characterized records that the catalyst material one or more of the following elements or connections of these elements, esp contains special oxides of these elements, such as platinum, palladium, Rhodium, cerium, chrome, molybdenum and vanadium. 4. Catalyst body according to one of claims 1 to 3, there characterized in that the fibers have a diameter of we have less than 100 µm.   5. Process for producing fibers for a metal fa ser catalyst body for cleaning exhaust gases from burning machines that are made of a woven, knitted or fiber flow Contains metal fibers, with catalyst material in the metal contain fibers or even in the form of fibers in the fabric is present, characterized in that the metal and / or the Catalyst material or the metal with the catalyst material al melted and from the melt using melt extract on threads are drawn that form thin fibers when cooled the. 6. The method according to claim 5, characterized in that as a metal a temperature-resistant material such as iron or Nickel, along with corrosion-inhibiting elements such as chrome, Yttrium and / or aluminum is used. 7. The method according to claim 5 or 6, characterized in that that the metal and / or the catalyst material or both too together in a protective gas atmosphere or under vacuum Melt extraction to be processed into fibers. 8. The method according to any one of claims 5 to 7, characterized ge indicates that fibers with a diameter of less than 100 µm getting produced. 9. Use of a metal fiber catalyst body according to claim 1 or produced according to claim 5 for cleaning exhaust gases from internal combustion engines in a motor vehicle, the metal fiber catalyst body ( 1 ) preferably in the combustion chamber ( 2 ) or in the exhaust manifold ( 3 ) of the motor vehicle is arranged.