The present invention relates to a honeycomb shaped cata ^¬ lyst formed of a corrugated substrate composed of a non- woven fibrous material.

In particular, the invention provides an improved honeycomb shaped catalyst prepared from corrugated sheets of a non- woven fibrous material, preferably provided with a flat liner.

We have found that a stable honeycomb shaped catalyst can be made of non-woven fibrous material, for instance E-glass fibers as starting material, when coating the material with a first coat layer prior to corrugating and forming the fibrous material into a corrugated sheet. The first coat lay ^¬ er is applied as an aqueous suspension of ceramic material.

We have additionally found that when the first coat layer is applied on the substrate in an amount resulting in a to ^¬ tal weight of substrate and coat layer of between 60-100 g/m ² results in an improved stability and stiffness of the paper so that waves formed in the corrugation process sub ^¬ stantially retain their shape in subsequent forming stages of the final honeycomb catalyst product and operation of the honeycomb catalyst product.

Pursuant to the above finding, this invention provides a honeycomb catalyst with a plurality of flow through chan- nels, wherein the honeycomb catalyst comprises a corrugated substrate and optionally a liner applied on the corrugated substrate, the substrate and the optional liner are com- posed of non-woven fibrous material with a first coat of a ceramic material in an amount to result in total weight of the substrate and first coat of between 60-100 g/m ² and a washcoat layer applied on the first coat, the wash coat contains or is impregnated with one or more catalytically active compounds.

The first coat ceramic material comprises preferably tita- nia, silica and/or kaolin. The first coat can be applied on the substrate sheet in form of an aqueous slurry, having a total solid content of 15 - 25 wt%, on one side of the sheet or on both sides of the sheet.

In both coating methods, the slurry penetrates the sheet.

A honeycomb body is formed by stacking up a plurality of the coated and corrugated sheets, or by rolling-up a single coated and corrugated sheet, preferably lined with a flat liner, into a rectangular or cylindrical honeycomb body. In each case the formed honeycomb body has a plurality of par ^¬ allel flow through channels formed by waves of the corru ^¬ gated sheet (s) and the optional liner applied on the corru ^¬ gated sheet ( s ) . To obtain the final honeycomb catalyst product, the honey ^¬ comb body pre-coated with the first coat is formed by stacking up or rolling up the coated corrugated sheet (s) and the coated liner if present, and is subsequently coated with the washcoat.

The washcoat acts as a carrier for the catalytic materials and is used to disperse the materials over a large surface area. Alumina, titania, silica, or mixtures thereof can be used. Preferably, the washcoat consists of titania.

Washcoating of the honeycomb body is usually performed by slurry pickup in the honeycomb body pre-coated with the first coat by pouring the washcoat slurry into the channels of the honeycomb body, or by dipping the body at one side into the washcoat slurry and optionally applying vacuum at the opposite side.

There are two possible methods of catalysing the honeycomb body .

In one method the washcoat contains the catalytic active material.

In the other method, the pre-coated and washcoated honey ^¬ comb body is finally impregnated with an aqueous solution containing one or more precursors of the desired catalyti- cally active material, followed by drying and calcination.

In summary, a honeycomb catalyst according to the invention can be prepared by a method comprising the steps of

(a) providing a sheet of non-woven fibrous material;

(b) coating the sheet with an aqueous suspension of a ce ^¬ ramic material; partly removing the moisture from the coat ^¬ ed sheet prior to

(c) corrugating the coated sheet;

(d) rolling-up or stacking up the coated and corrugated sheet (s) into a spiral-wound cylindrical body or staked up rectangular body; (e) washcoating the cylindrical or rectangular body, op ^¬ tionally containing the catalytic active components or pre ^¬ cursors thereof and

(f) drying and optionally calcining the washcoated body; or alternatively

(el) impregnating the washcoated body with a solution of catalytic active components or precursors thereof, if not contained in the washcoat of step e) ;

(fl) drying and calcining the body of step (el) to obtain the final honeycomb catalyst.

Honeycomb catalysts are typically employed in the cleaning of engine exhaust gas. For this purpose the honeycomb cata ^¬ lyst is shaped as a cylindrical body and canned in a metal housing with a mat between the honeycomb catalyst body and the metallic housing. In the canning process the cylindrical honeycomb body is radially compressed in order to pro ^¬ vide sufficient friction between the mat and the body and between the mat and the metallic housing. Radially compres- sion typically causes cracks in the coated and calcined body. Thus, a further advantage of the first coat provided on the substrate is that the canning process causes a much reduced cracking of the honeycomb body. The canned honeycomb catalyst is as mentioned above typi ^¬ cally used in the catalytically removal of noxious com ^¬ pounds in the exhaust gas, including nitrogen oxides, un- burnt engine fuel and carbon monoxide. Thus, it is preferred that the catalytically active com ^¬ pounds of the honeycomb catalyst are active in the removal of noxious compounds in engine exhaust gas. Catalyst compounds active in engine exhaust gas cleaning are per se known in the art. To name a few, typically em ^¬ ployed catalysts are vanadium oxide, tungsten oxide, palla- dium and platinum, and zeolitic material either used alone or as mixtures thereof.

When operating the honeycomb shaped catalyst in the removal of nitrogen oxides contained in exhaust or off-gasses, the nitrogen oxides are converted to free nitrogen with a re ^¬ ducing agent, typically ammonia, in the presence of an SCR catalyst by selective, catalytic reduction:

4 NO + 4 NH3 + 02 → 4 N2 + 6 H20

NO + N02 + 2 NH3 → 2 N2 + 3 H20

Any of the known SCR catalyst compositions will be suitable for use in the invention.

Fig. 1 of the drawings is a sectional view of a honeycomb catalyst according to the invention.

As seen in Fig. 1, the substrate 1 of a honeycomb catalyst according to the invention is composed of a corrugated sheet 2 of non-woven fibrous material substrate, optionally provided with a liner (not shown) . Substrate 1 can be rolled-up to a cylindrical body. A first coat layer 3 made of ceramic material is coated on sheet 2. The first coat material can also diffuse through the fibrous material of sheet 2 and forms a first coat lay- er on both sides of sheet 2and within the fibrous material, as shown in Fig.l. A washcoat layer 4 is coated on the first coat layer 3. Washcoat layer 4 contains catalyst par ^¬ ticles 5.