CN205517799U - Cellular catalyst of canning - Google Patents

Abstract

A honeycomb catalyst, wherein the honeycomb catalyst comprises a substrate consisting of a slurry-coated fluted corrugated sheet and a slurry-coated flat substrate, the slurry-coated sheet consisting of a nonwoven made of fibrous material, the substrate is rolled into a cylinder to form multiple flow channels, and both the slurry-coated plate and the slurry-coated flat substrate contain a catalyst in the slurry coating, the honeycomb catalyst is Canned in a metal casing with inserted mats, wherein the honeycomb has a Young's modulus equal to or greater than about 10 MPa but less than or equal to about 1000 MPa, and the substrate has a bulk density between 250 and 700 g/l.

Description

Canned Honeycomb Catalyst

technical field

The present invention relates to a honeycomb-shaped catalyst packed in a metal shell.

Specifically, the present invention provides an improved honeycomb shaped catalyst prepared by rolling corrugated ceramic paper into a cylinder and coated with a wash coat to provide optimum bulk density of the catalyst , the catalyst has high radial compressive strength and elasticity during canning and improved holding force within the metal casing during operation of the catalyst.

Background technique

Honeycomb catalysts in the form of cylinders known in the art are prepared by rolling corrugated metal sheets to provide a stable structure when operating with hot exhaust or exhaust gases. See eg US2010254864, US7101602, EP0988892, EP0919280 and US6689328.

It is also known to produce cylindrical honeycomb catalysts from nonwoven fibrous materials such as ceramic paper. In this case, a plate of fibrous material is pre-coated with a binder and the structure of fibrous material is then filled with ceramic slurry, corrugated and usually lined with a flat plate. The corrugated sheets are wound together with the flat sheets to form a cylindrical honeycomb body, coated with a ceramic slurry and impregnated with a catalytically active material.

Honeycomb-shaped catalysts are often used to purify exhaust gases from automotive sources. In these applications, the catalyst is potted in a metal casing and placed in the engine exhaust system.

To keep the catalyst in place during operation and to prevent cracking, the honeycomb body is usually wrapped in a holding mat made of ceramic fibers. The pad also acts as a thermal insulator and seals to prevent exhaust gases from bypassing the catalyst. The precautions described above require the pad to have certain properties, including thermal conductivity, air tightness, and coefficient of friction.

Cans of encapsulated honeycomb catalysts in metal casings can be done by different methods. A common method is stuffing.

In the packing method, a mat-encased honeycomb catalyst is pushed into a cylindrical metal shell. Use a packing cone to facilitate smooth insertion of monolithic material.

To ensure sufficient friction between the mat and the honeycomb and between the mat and the shell, the diameter of the wrapped honeycomb must be slightly larger than the inner diameter of the shell.

The installation pressure of the mat and honeycomb increases during packing and can lead to severe cracking of the honeycomb catalyst if its elasticity is too low. On the other hand, if the elasticity of the honeycomb is too high, the holding force (ie friction) will not be sufficient to keep the honeycomb body in place in the metal casing during operation.

When using only non-woven fibrous material (such as wound corrugated sheets made of glass fibers) as the substrate of the honeycomb catalyst, the elasticity of the substrate will be too high, resulting in too low holding force inside the metal shell, which This is because the normal force applied to the pad through the elastic base is too low.

In this case, the canned honeycomb catalyst will experience severe vibrations during operation and eventually break, leading to failure.

Therefore, it is necessary to reduce the elasticity of the substrate to some extent. The elasticity of the substrate can be reduced by coating the substrate with a slurry coating and firing. However, the amount of slurry coating must be balanced within certain bulk density limits. Coating a paper substrate with too large a size coating results in too high a bulk density, can cause an undesired high pressure drop across the honeycomb catalyst when used in a gas purification process, and otherwise cause waste of expensive catalyst material.

Utility model content

We have found that a stable cylindrical honeycomb-shaped catalyst canned in a metal casing can be made from ceramic paper, ceramic paperboard reinforced with E-glass fibers, or ceramic Paper as starting material, the corrugated paper is coated with a ceramic slurry coating to obtain a bulk density between 250 and 700 g/l, and the coated substrate is fired to obtain the value E measured as Young's modulus Elasticity between 10 and 1000MPa.

Accordingly, the present invention provides a honeycomb catalyst having a plurality of flow through channels, wherein the honeycomb catalyst comprises a wash coated fluted corrugated plate and a slurry coated A base composed of a flat substrate, the size-coated board is made of non-woven fibrous material, the base is rolled into a cylinder to form a plurality of flow channels, and the size-coated board and the size-coated flat The catalyst is contained in the slurry coating of the substrate, the honeycomb catalyst is potted in a metal casing with interposed mats, wherein the Young's modulus E of the honeycomb is equal to or greater than about 10 MPa but less than or equal to about 1000 MPa, and The bulk density of the substrate is between 250 and 700 g/l.

Description of drawings

Fig. 1 is a cross-sectional view of a honeycomb catalyst according to the present invention.

detailed description

As shown in FIG. 1 , a substrate 1 of a honeycomb catalyst according to the present invention is composed of a slurry-coated substrate 2 and a slurry-coated corrugated plate 3 . Roll base 1 into a cylinder.

In the final slurry-coated catalyst, the wall thickness of the substrate 2 is measured at a point outside the area where the substrate 2 contacts the corrugated sheet 3, as indicated by reference numeral 4 . In the final slurry-coated catalyst, the wall thickness of the corrugated sheet 3 is measured at a point 5 in the tangential area of the wave 6 . The wavelength in the final slurry coated catalyst is measured between the two troughs at points 7 and 8 . The corrugation height H in the final slurry-coated catalyst is measured between the inner surface 9 of the substrate 2 and the inner surface 10 of the waves 6 . The substrate 1 is potted in a metal casing 12 and held in the casing 12 by a mat 11 disposed between the inner wall of the casing and the substrate 2 .

In one embodiment, the mat comprises inorganic fibers. In another embodiment, the pad comprises biosoluble fibers.

Elasticity was calculated from Young's modulus E by dividing tensile stress by extension strain.

in:

E is Young's modulus (modulus of elasticity);

F is the force exerted on the object under tension;

A ₀ is the initial cross-sectional area through which the applied force passes;

ΔL is the change in the length of the object;

L ₀ is the initial length of the object.

Preferably, the wall thickness of the slurry coated fluted corrugated sheet is between 0.28 and 0.38 mm and the wall thickness of the slurry coated substrate is between 0.37 and 0.47 mm, the fluted corrugated The wavelength of the plate is between 2.40 and 3.40 mm, the corrugation height is between 0.65 and 2.05 mm, and the hydraulic diameter of the channels is between 0.6 and 1.5 mm.

Typical applications for canned honeycomb catalysts are engine exhaust purification, including the removal of unburned engine fuel and carbon monoxide by catalytic oxidation or selective catalytic reduction (SCR) of nitrogen oxides.

In these applications, the slurry coating comprises titanium dioxide impregnated with vanadium oxide and optionally tungsten oxide as a catalytic material active in the SCR reaction; or when used as an oxidation catalyst the slurry coating comprises titanium dioxide and/or or alumina impregnated with platinum and/or palladium.

In the honeycomb catalyst according to the present invention, the substrate can be coated in different areas with a slurry coating, wherein the slurry coating in each area contains the same or different catalysts; or with superimposed multi-layer slurry Coatings coat the substrate, where each layer contains the same or a different catalyst. The substrate may have a downstream region or bottom layer containing an ammonia slip catalyst.

Slurry coating of monolithic substrates or honeycomb monolithic substrates is typically performed by slurry pickup in the substrate by pouring the slurry into the channels of the monolithic substrate or by dipping one side of the substrate into the slurry of the slurry coating and optionally by applying a vacuum on the opposite side.

After having been coated with the slurry coating, the substrate is dried and fired before impregnating the slurry coating with an aqueous impregnation solution comprising a soluble precursor of the catalytically active metal oxide.

The dipping step comprises immersing the slurry-coated substrate in a dipping tank containing an aqueous dipping solution or spraying the slip-coated substrate with the dipping solution.

Instead of dipping the slurry coating, it is also possible to add the catalytic material to the slurry coating slurry before coating.

Claims (8)

1. a honeycombed catalyst, wherein said honeycombed catalyst comprises substrate, reeded corrugated board and the flat substrate of slurry coating that described substrate is coated by slurry are constituted, the plate of described slurry coating is made up of nonwoven material, described substrate is rolled into cylinder to form multiple circulation passages, and the slurry coating of the flat substrate of the plate of slurry coating and slurry coating all contains catalyst, described honeycombed catalyst is potted in the metal shell of the pad with insertion, wherein said honeycomb has equal to or more than 10MPa but is less than or equal to the Young's modulus of 1000MPa, and described substrate has the bulk density between 250 to 700g/l.

2. the honeycombed catalyst described in claim 1, wherein the wall thickness of the reeded corrugated board of slurry coating is between 0.28 to 0.38 millimeter, the wall thickness of the substrate of slurry coating is between 0.37 to 0.47 millimeter, the wavelength of reeded corrugated board is between 2.40 to 3.40 millimeters, and wave height is between 0.65 to 2.05 millimeter；And the hydraulic diameter of passage is between 0.6 to 1.5 millimeter.

Honeycombed catalyst the most according to claim 1 and 2, wherein said pad comprises inorfil.

Honeycombed catalyst the most according to claim 1 and 2, wherein said pad comprises biosoluble fibers.

Honeycombed catalyst the most according to claim 1 and 2, wherein slurry coating comprises titanium dioxide, and catalyst comprises vanadium oxide and optional tungsten oxide.

Honeycombed catalyst the most according to claim 1 and 2, wherein slurry coating comprises titanium dioxide and/or aluminum oxide, and catalyst comprises platinum and/or palladium.

Honeycombed catalyst the most according to claim 1 and 2, wherein coats in zones of different with slurry coating, containing identical or different catalyst in the slurry coating in the most each region in substrate；Or by the multilayer slurry coating coated substrate of superposition, each of which layer contains identical or different catalyst.

Honeycombed catalyst the most according to claim 7, wherein substrate has the downstream area containing NH_3 leakage catalyst or bottom.