SE1450942A1 - Exhaust aftertreatment systems and vehicles including such exhaust aftertreatment systems - Google Patents

Abstract

The exhaust after-treatment system (1) according to the present invention comprises a poison trap in the form of an element arranged upstream of an exhaust after-treatment device (3) in an exhaust duct (4) between an exhaust outlet (5) from an internal combustion engine and an exhaust inlet (6) of the exhaust after-treatment device. The element comprises a surface (14), which is intended to be exposed to the exhaust gases in the exhaust duct and adapted to adsorb chemical toxins in the exhaust gases. In this way, a large amount of chemical toxins can be captured from the exhaust gas flow even before it reaches the first catalyst in an exhaust gas aftertreatment device.

Description

1AVGASEFTERBEHANDLlNGSSYSTEl \ / I SAl \ / IT vehicle comprising SÃDANTAVGASEFTERBEHANDLlNGSSYSTEl \ / l The present invention relates to an exhaust gas aftertreatment system for exhaust gases from enförbränningsmotor, exhaust gas treatment system comprising enavgasefterbehandlingsanordning comprising at least one catalyst arranged attrena exhaust gases, such an exhaust gas after-treatment device comprising at least endieseloxidationskatalysator (DOC) and a The invention further relates to a vehicle comprising an internal combustion engine and an exhaust after-treatment system.

BACKGROUND An internal combustion engine burns an air and fuel mixture to generate a driving torque. The combustion process generates exhaust gases emitted from the internal combustion engine. These exhaust gases are led via an exhaust line to an exhaust line outlet arranged at the downstream end of the exhaust line, from which the exhaust gases are emitted to the surroundings. The exhaust gases from the internal combustion engine contain, among other things, nitrous exhaust gases (NOX), carbon dioxide (CO 2), carbon monoxide (CO) and particles. NOX is a generally accepted collective name for describing the nitrous exhaust gases which primarily comprise nitric oxide (NO) and nitrogen dioxide (NO2). Before the exhaust gases are discharged to the environment via the exhaust line outlet of the exhaust line, the exhaust gases are passed through an exhaust after-treatment device arranged in the exhaust line, which usually comprises one or more catalysts, one or more particulate filters for purifying the exhaust gases and any muffler. The exhaust gases are led from the internal combustion engine to the exhaust after-treatment device via an exhaust duct.

The exhaust aftertreatment device usually comprises a diesel oxidation catalyst (DOC catalyst) mainly adapted to oxidize hydrocarbons but also carbon monoxide and nitrogen monoxide. Furthermore, the exhaust gas aftertreatment system usually comprises a selective 2-catalytic reduction catalyst (SCR catalyst) in which a reducing agent and NOX can react and convert to nitrogen and water, thus reducing the amount of NOX released into the atmosphere. The reducing agent is usually a urea-based solution, such as Adblue®, and is injected into the exhaust line upstream of the SCR catalyst.

The exhaust aftertreatment device usually also comprises one or more diesel particulate filters (for example catalytically coated soot particulate filter CSF, Eng: Catalysed Soot Filter) for capturing and oxidizing, for example, soot particles. Other types of catalysts can also be used in an exhaust aftertreatment device, such as ammonia slip catalyst (ASC).

The various components of the exhaust aftertreatment device are arranged in a common housing which is gas tight apart from an exhaust inlet arranged in the housing to which the exhaust duct from the internal combustion engine is connected, an exhaust outlet from which the purified exhaust gases are allowed to be passed on to the surrounding atmosphere. used in the various components, such as urea-based solution for SCR.

The diesel oxidation catalyst is often arranged upstream of an SCR catalyst so as to oxidize hydrocarbons, carbon monoxide and nitrogen monoxide, before these reach the SCR catalyst, which otherwise can affect the efficiency of the SCR catalyst. In fact, it is common for the diesel oxidation catalyst to be the first component of the exhaust aftertreatment device. Thus, the diesel oxidation catalyst is often exposed to a wide variety of substances and compounds that can cause poisoning and deactivation of the diesel oxidation catalyst. In exhaust aftertreatment devices where the diesel oxidation catalyst is not the first catalyst in the device, the first catalyst which is exposed to the exhaust gases will of course be the one which is exposed to the greatest load of chemical toxins in the exhaust gases.

Sulfur poisoning of the diesel oxidation catalyst is a known problem in the technical field. The solution to this is usually to temporarily increase the temperature of the exhaust gases in such a way that the sulfur coating dissolves or decomposes. It is also known to try to capture sulfur before it reaches the diesel oxidation catalyst by arranging a suitable component therefor in the exhaust aftertreatment device.

US 2009/0107121 A1 discloses an exhaust aftertreatment system comprising a catalyst which acts as an SOX trap, an oxidation catalyst, a particulate filter and a NOX SCR catalyst. The catalyst that acts as an SOX trap consists of a honeycomb structure with several passages extending in the axial direction of the catalyst. Furthermore, this catalyst has a coating, comprising for example alkali metal, on which a noble metal is arranged. This means that the cost of the SOX trap is relatively high. In addition, it can be difficult to replace if the SOX trap itself is deactivated in such a way that it can no longer absorb chemical toxins.

In addition to sulfur, there are also other substances that can accumulate in the first catalyst in the exhaust gas aftertreatment device, which cannot be removed by an elevated temperature. It has been found that phosphorus in particular is a problem in prior art exhaust gas treatment systems as phosphorus-containing compounds poison and / or deactivate the catalyst. Phosphorus, for example, is present in certain fuels such as biofuels or is used as an additive in certain engine oils and thus also risks being present in the exhaust gases from the internal combustion engine. Post-mortem analyzes of diesel oxidation catalysts that have been arranged first in an exhaust aftertreatment device and where biofuels have been used in the pre-combustion engine show that large amounts of toxins, such as phosphorus, have accumulated in the diesel oxidation catalyst.

Poisoning and / or deactivation of the diesel oxidation catalyst leads to a deterioration efficiency of the diesel oxidation catalyst and eventually also affects subsequent components in the exhaust after-treatment system.

US 2002/0064491 A1 describes a process in which volatile phosphorus compounds in exhaust gases are removed by reaction with metal or metal-containing compounds which form solid compounds with the volatile phosphorus compounds in the exhaust gases. This can be done by dosing the metal or metal compound upstream of the catalyst, by adding to the engine oil or fuel of the internal combustion engine, or by an absorbent device arranged in an exhaust pipe between an engine and a catalyst which can remove phosphorus from the exhaust gases before reaching the catalyst. 4EP 0638349 A1 describes a process for protecting catalysts for purifying exhaust gases from poisons through an adsorbent which may consist of zeolite or mixtures of different zeolites.

The absorbent is arranged in the exhaust stream upstream of the catalyst and may be in honeycomb form.

It may also be coated on the catalytic coating of the catalyst.

Since the various catalysts are often built with additional components in a single unit, an exhaust aftertreatment device as described above, it is not easy to pick a single catalyst separately from a vehicle to clean, regenerate or replace it. Replacing the entire exhaust aftertreatment device also involves a significant cost. Replacing a catalyst, such as a diesel oxidation catalyst, with exhaust aftertreatment devices that allow this also involves a significant cost because such catalysts are expensive. It is therefore desirable to be able to minimize the poisoning or at least substantially delay the poisoning of a catalyst, in particular the catalyst which is arranged first in the direction of flow of the exhaust gases, in the exhaust after-treatment device.

In addition to this, today in some states, state unions or regions there are also legal requirements for the off-gas after-treatment device must have a minimum service life expressed in time and / or accumulated mileage for the vehicle, such as 7 years or 700,000 kilometers, without the emission requirements being exceeded. This means that an exhaust after-treatment system for vehicles must be designed in such a way that it either has such a service life or can easily be regenerated so that an exhaust after-treatment device does not need to be replaced with a new one within the statutory time / mileage.

SUMMARY OF THE INVENTION An object of the present invention is to reduce the risk of, alternatively delaying, deactivation of a catalyst, such as a diesel oxidation catalyst, in an exhaust after-treatment system in a cost-effective manner and preferably without substantially affecting the exhaust gas pressure in the exhaust after-treatment system. The object is obtained by means of the exhaust gas aftertreatment system according to the independent claim 1. Exemplary embodiments are defined by the independent claims.

The exhaust after-treatment system according to the present invention comprises a poison trap in the form of an element arranged upstream of an exhaust after-treatment device in an exhaust duct arrangement between an exhaust outlet of an internal combustion engine and an exhaust inlet of the exhaust after-treatment device. The element comprises a surface which is intended to be exposed to the exhaust gases in the exhaust duct and adapted to adsorb chemical toxins in the exhaust gases. In this way, a large amount of chemical toxins can be captured from the exhaust gas flow even before it reaches the first catalyst in an exhaust gas aftertreatment device. Furthermore, the location of the element means that it can be easily removed for replacement or regeneration without the exhaust after-treatment device having to be removed from the vehicle and dismantled.

The exhaust after-treatment system according to the present invention comprises an exhaust after-treatment device and an exhaust duct adapted to be arranged between one exhaust outlet of a combustion engine and an exhaust inlet of the exhaust after-treatment device. The exhaust aftertreatment device comprises at least one catalyst adapted for purifying the exhaust gases. An element having a surface adapted to adsorb at least one substance or compound which can deactivate the catalyst in the exhaust gas purification device is arranged in the exhaust duct. Said surface comprises a material consisting of a pillared clay, PILC (Eng: Pillared layered clay). Conveniently, the entire surface of the element exposed to the exhaust gases is formed by PILC.

The element is preferably detachably arranged in relation to the exhaust duct and can thus be removed from the exhaust after-treatment system for cleaning or regeneration or alternatively replaced. This can be achieved, for example, by releasing the exhaust duct from the exhaust after-treatment device and the exhaust outlet of the internal combustion engine and pushing or pulling elements out of the exhaust duct. Another alternative is that the exhaust duct comprises a hatch through which the element can be inserted or removed from the exhaust duct. A further alternative is to arrange the element in a first exhaust duct section which is detachably arranged in relation to a second exhaust duct section adjacent in the axial direction of the exhaust duct, wherein the exhaust duct section can either be replaced or the element therein can be cleaned or regenerated.

The element may suitably comprise a plurality, through which the exhaust gases can flow, channels whose axial extent is arranged in the axial extent of the exhaust duct. In this way, the risk of the element causing a pressure drop decreases, for example in relation to whether the duct of the element should have an angular extent in relation to the main flow through the exhaust duct. Furthermore, it is preferred that the element has an open area in the radial cross-section of the exhaust duct which is larger than the open area of the first catalyst in the exhaust gas purification device. Thereby, the element does not risk being blocked by, for example, particles in the exhaust gases or to substantially affect the pressure of the exhaust gases in the exhaust duct. To achieve this, the element can for instance be shaped as a honeycomb structure, a net-shaped structure or an at least partially folded structure where said folds are arranged so that they extend in the axial direction of the exhaust duct. These structures also have the advantage of having a large surface which comes into contact with the exhaust gases and can thereby have a large adsorbent surface.

According to an exemplary embodiment, the PILC material is selected from a PILC comprising columns of alumina, silica, titanium oxide or a mixture of at least two of said oxides. These PILCs generally have good thermal properties and are stable at temperatures above 500 ° C.

The PILC material may conveniently be doped to increase the affinity of at least one substance or compound, preferably phosphorus or phosphorus-containing compounds, which risks deactivating said catalyst of the exhaust gas aftertreatment device.

According to an exemplary embodiment, the PILC is selected from a porous clay heterostructure, PCH (Porous Clay Heterostructure), preferably a PCH comprising columns of silica, titanium oxides or a mixture of silica and titanium oxide and is doped with iron or aluminum. These materials have been shown to have very good thermal properties and a particularly good ability to adsorb phosphorus and its compounds. 7PILC material can be arranged as a coating on a load carrier in such a way that the coating and the load carrier together form the element. It is also conceivable that the whole element consists of PILC.

For cost reasons, it is preferred that the surface of the element, preferably the entire element, be free of precious metal. The element is also not intended to constitute a catalyst for purifying exhaust gases, but only to adsorb toxins from the exhaust gases which risk deactivating the downstream catalysts, and thus does not have to function as a catalyst.

The element is preferably arranged at or near a downstream end of the exhaust duct. For example, it may be located in the immediate vicinity of the exhaust inlet of the exhaust aftertreatment device. In this way, for example, the mechanical stresses of the element, caused by vibrations during operation of the internal combustion engine, can be minimized. Furthermore, this placement of the element is preferred when the flow of the exhaust gases in this part of the exhaust duct is turbulent, which favors mass transport of toxins and storage of these in a surface exposed to the exhaust gases.

The element may have a limited extent in the axial extent of the exhaust duct as it has been found that the capture of chemical toxins can be effected effectively on a relatively short surface, especially when there is turbulent flow of the exhaust gases. A relatively small axial extent is also advantageous as the risk of the element substantially affecting the pressure of the exhaust gases in the exhaust duct is minimized. Suitably the axial extent of the element in the axial extent of the exhaust duct may be between 1 and 10 cm, preferably up to 5 cm. The present invention also relates to a vehicle comprising an internal combustion engine and an exhaust after-treatment system as described above. The vehicle can be, for example, a truck, a bus or a car. The vehicle can also be a marine vehicle or an off-road vehicle.

DESCRIPTION OF THE FIGURES Fig. 1a shows a schematic side view of a vehicle comprising an internal combustion engine and an exhaust aftertreatment device.

Fig. 1b shows a perspective view of an exhaust after-treatment system comprising an exhaust after-treatment device and an exhaust duct.

Fig. 1c schematically shows an example of an exhaust aftertreatment device.

Fig. 2 shows a part of a radial cross-section of an element adapted to be arranged in an exhaust gas after-treatment system in accordance with an exemplary embodiment of the present invention.

Fig. 3 shows a part of a radial cross-section of an element adapted to be arranged in an exhaust gas after-treatment system in accordance with another exemplary embodiment of the present invention.

Fig. 4 shows a part of a radial cross-section of an element adapted to be arranged in an exhaust gas after-treatment system in accordance with a further embodiment of the present invention.

DETAILED DESCRIPTION The invention is described in detail below with reference to the accompanying figures. The invention is not limited to the embodiments described and shown in the figures but can be modified within the scope of the appended claims. Furthermore, the figures should not be considered as scaled-down as certain features may be exaggerated to more clearly illustrate the invention.

The present invention is intended to overcome the problems caused by chemical toxins in exhaust gases. In this context, poisons refer to elements or compounds thereof which can poison or deactivate at least one catalyst in an exhaust after-treatment device, in particular a diesel oxidation catalyst of an exhaust after-treatment device. Such toxins can be present either in gaseous form, in particulate form or in some cases even in liquid form without departing from the invention. Poisoning of such a catalyst usually takes place by toxins accumulating in the catalyst and leading to so-called fouling (coating) on the 9 catalytic surfaces of the catalyst. Toxins can also accumulate in the catalyst via selective adsorption on the catalytic surfaces of the catalyst. Thus, the poisons may eventually deactivate the catalyst when the catalytic reaction is prevented or at least substantially deteriorated. Examples of poisons are sulfur, phosphorus, zinc, calcium, magnesium or alkali metals, or compounds comprising one or more of these elements. In accordance with the present invention, a elements with a surface adapted to trap substances or compounds in the exhaust gases from the internal combustion engine arranged in the exhaust duct arranged between an exhaust outlet of the internal combustion engine and an exhaust inlet of a exhaust gas aftertreatment device comprising one or more catalysts arranged pre-cleaning of the exhaust gases. In this way, said surface traps at least one substance or compound which risks poisoning or deactivating the components of the exhaust aftertreatment device, in particular the diesel oxidation catalyst of the exhaust aftertreatment device in those cases where it is arranged first by the catalysts in the exhaust aftertreatment device. as a transport distance for the exhaust gases from the internal combustion engine (more specifically from the turbine in the turbocharger of the internal combustion engine) to the exhaust after-treatment device. By arranging an element with a surface adapted to capture one or more substances or compounds which can poison or deactivate the diesel oxidation catalyst in this exhaust duct, the exhaust duct is utilized efficiently. In addition, the life of the exhaust aftertreatment device is extended by the exhaust aftertreatment system in that it can be used for a longer period of time before the exhaust aftertreatment device needs to be replaced or otherwise regenerated. Continues the fact that said element is arranged in the exhaust duct instead of the exhaust aftertreatment device that said element can easily be replaced or removed prior to regeneration, for example during a regular service of the vehicle, without the exhaust gas aftertreatment device itself having to be removed from the vehicle and dismantled. A further advantage of the present invention is that the exhaust after-treatment device does not need to be redesigned to enable the advantages of the invention, but the only exhaust gas duct needs to be adapted. In this way, existing vehicles can also utilize the advantages of the invention by only replacing the exhaust duct with an exhaust duct adapted to contain said elements.

Capture of toxins from the exhaust gases from the internal combustion engine by means of said element device arranged in the exhaust duct takes place by adsorption on a surface of the element. By adsorption is meant the retention of a substance, which may be an atom, ion, molecule or compound from a gel or liquid on a surface of a solid body. Adsorption can be divided into chemisorption which involves a chemical reaction between the surface and the absorbed substance, or physisorption in which the interacting forces between the surface and the substance are relatively weak and can be caused, for example, by van der Waal forces.

The exhaust duct is a tubular element which may comprise a plurality of bends or the like and thus may have a center axis which is not straight. The exhaust duct can be divided into several exhaust duct sections. At least one exhaust duct section may be conventionally designed to allow uptake of vibrations in the exhaust duct so as to minimize the mechanical stresses of the exhaust duct.

The exhaust aftertreatment device comprises at least one catalyst intended to purify the exhaust gases from the internal combustion engine. Typically, the exhaust aftertreatment device includes a variety of catalysts, such as DOC, SCR, ASC, and / or CSF. It may also include other types of filters and / or sound attenuators. The exhaust aftertreatment device comprises a housing in which the various components thereof are arranged in a common unit. The housing comprises an exhaust inlet connected to the exhaust duct extending from the combustion engine to the exhaust aftertreatment device and an outlet from which purified exhaust gases can be passed on to the surrounding atmosphere. The exhaust after-treatment device is designed in such a way that exhaust gases cannot be allowed to leave the exhaust after-treatment device in any other way than through the outlet.

In accordance with the present invention, said element constitutes an element with a surface adapted to capture one or more substances or compounds which risk poisoning or deactivating a catalyst. The surface comprises a material consisting of a columned clay, PILC, which enables adsorption of said substance / substances or contaminant / contaminants. The element may, for example, be substantially cylindrical in shape and have a honeycomb structure, a net-shaped structure or a pleated structure, in such a way that the structure (i.e. the construction) of the element creates axial channels through which the exhaust gases can flow. Such a cylinder-shaped element is suitably arranged coaxially with the exhaust duct. Furthermore, the element is preferably in the form of a monolithic structure.

To minimize the risk of the element creating a pressure drop in the exhaust duct during operation of the internal combustion engine, it is preferred that it has a relatively open structure, i.e. a large open area in the radial cross-section of the exhaust duct. The open area of the element is the sum of the area of the ducts in the radial cross-section of the exhaust duct. However, the element should have a sufficiently large surface area to be able to adsorb as much of the chemical toxins in the exhaust gases as possible in order to minimize the risk of a catalyst in the exhaust aftertreatment device being poisoned.

The element may have a relatively short axial extent in the axial extent of the exhaust duct. Short axial extension is advantageous to minimize the pressure drop in the exhaust duct due to the element, i.e. to ensure that the element does not contribute to a significant pressure drop increase. Post-mortem analyzes of diesel oxidation catalysts first arranged in a single-exhaust purifier have shown that storage of chemical toxins takes place primarily in the first centimeter of the catalyst where the exhaust gas flow is turbulent. For this reason, an axial extension of the element in the exhaust duct can be as short as about 1 cm, above all the element is arranged in a part of the exhaust duct where the exhaust flow is turbulent, for example the proximity of the inlet to the exhaust after-treatment device. For the same reason, the element does not need to have an axial extent greater than 10 cm, although it is possible to design elements with a longer extent. Preferably, the element could have an axial extent in the axial extent of the exhaust duct about 1-5 cm.

Unlike prior art poison traps, such as conventional noble metal-containing honeycomb structures for trapping sulfur-containing compounds, the element for trapping toxins in accordance with the present invention is arranged in the exhaust duct, made of a relatively inexpensive material, preferably has a large open area and a relatively short axial extent. , and is preferably releasably arranged in the exhaust duct. This provides a cost-effective solution to the problem of deactivating a catalyst in the exhaust aftertreatment device without any significant effect on the pressure of the exhaust gases in the exhaust duct or in the exhaust aftertreatment device, which in turn could affect the internal combustion engine load and / or aftertreatment component aftertreatment.

Fig. 1a shows a schematic side view of a vehicle 100 in the form of a truck. The vehicle 100 is provided with an internal combustion engine 2 arranged to drive the drive wheels 17 of the vehicle via a gearbox and a propeller shaft (not shown). The internal combustion engine 2 is driven by a fuel which is fed to the internal combustion engine by means of a fuel system comprising a fuel tank 16. The exhaust gases from the internal combustion engine 2 are transported via an exhaust duct 4 to an exhaust after-treatment device 3.

Fig. 1b shows a perspective view of an exhaust after-treatment system 1 comprising an exhaust after-treatment device 3 and an exhaust duct 4. The exhaust duct 4 is arranged between an exhaust outlet 5 of an internal combustion engine 2 (shown only schematically) and an exhaust inlet 6 of the exhaust after-treatment device. the combustion engine of the exhaust aftertreatment device.

Fig. 1c schematically shows an exemplary exhaust gas aftertreatment device 3 comprising one diesel oxidation catalyst (DOC) 7, a downstream DOC arranged selective catalytic reduction catalyst (SCR) 8, and a downstream SCR catalyst arranged particle filter 9. The various components of the aftertreatment components can happen. For example, the exhaust aftertreatment device may also include sound attenuators, additional particulate filters, and additional catalysts if needed for specific application. Any exhaust gas aftertreatment device can be used according to the invention provided that it comprises at least one catalyst for purifying exhaust gases. Preferably, the exhaust aftertreatment device comprises at least one diesel oxidation catalyst and an SCR catalyst, and optionally a catalytically coated particulate filter, but not necessarily arranged in the order shown in Fig. 1c.

Since the element is arranged upstream of the exhaust after-treatment device, it will be subjected to a large load in the form of chemical toxins the exhaust gases and will thus be saturated long before the exhaust after-treatment device. It is therefore desirable to arrange the element in a detachable manner in the exhaust duct in order to thereby make it possible to easily replace it or to pick it out for cleaning or regeneration. The element according to the present invention can therefore be arranged in the exhaust duct either in the form of a single exhaust duct section which is detachably attached to at least one adjacent exhaust duct section, and another exhaust duct section or an inlet of the exhaust after-treatment device. Another alternative is to arrange an opening, preferably closable by means of a hatch or the like, in the exhaust duct through which the element can be inserted into the exhaust duct or removed from the exhaust duct.

In accordance with the present invention, the element has a surface which is intended to be exposed to the exhaust gases in the exhaust duct, which comprises a material consisting of a pillar clay, PILC. The PILC material is arranged in such a way that chemical toxins in the exhaust gases can be adsorbed by means of this material. The element may consist entirely of the PILC material, or the PILC material may be present in the form of a coating on a surface of the element which is intended to be exposed to the exhaust gases. In the latter case, the element comprises a load carrier and a single coating of PILC. Preferably, all surfaces which are intended to be exposed to the exhaust gases are formed of the PILC material. Furthermore, the PILC material constitutes the outermost surface of the hose element, i.e. there is no additional coating on the PILC material on the side of the PILC material which is opposite a possible load carrier. On the other hand, it is possible to arrange a coating between the load carrier and the coating of PILC if desired, for example to improve the adhesion of PILC to the load carrier.

PILC is a zeolite-like material with modified layers that are separated by controlled distances from each other and contains a two-dimensional network of pores. PILC is prepared from synthetic or natural clays, for example smectites (especially montmorillonite), vermiculites, or bentonite. PILC materials are prepared by exchanging cations in the silicate of the clay with, for example, hydroxycation ions, preferably large hydroxycation ions, which are formed by hydrolysis of metal oxides or salt. This can be done, for example, by swelling the clay with the aid of a suspending agent, for example water, and adding the desired cation to the suspension. Upon heating, the metal hydroxide ions are subjected to dehydration and dehydroxylation, forming stable metal oxide or other metal salt. The metal oxide or salt formed is a nanoparticle that acts as a pillar that keeps the thin silicate layers separated from each other. This creates space between the layers in the material of molecular size, usually 1-20 Å, even if it is possible to create even larger distances. Examples of oxides used as pillars are oxides of titanium, zirconium, aluminum, iron, silicon or chromium. If the cation added to the clay to form the columns is catalytically active, the resulting material can be used as a catalyst.

PILC can, if desired, be doped with metal or metal ions. Examples of dopants that can be used in PILC are alkaline earth metals or transition metals (incl. Lanthanoids), or ions thereof. It is also known that it is possible to dop with other substances, such as aluminum and gallium.

PILC was first developed in the 1970s and is used today, for example, as a catalyst for cracking hydrocarbons, and as catalysts or absorbents in soil and water remediation. PILC has also been proposed as a catalyst in SCR processes to reduce nitrogen oxides, for example in coal-fired boilers as described in US 5,415,850.

A new class of PILC was developed in the 1990s and is called Porous Clay Heterostructures (PCH). The preparation thereof is based on the introduction of silica columns into between the layers of clays by a method using a surfactant. Also, for example, titanium oxide can form pillars in PCH. PCH is characterized by high surface area, a structure-containing micro- and mesopores, surface acidity, and cation exchange properties. The structure of PCH is stable up to high temperatures and PCH can therefore be used in high temperature processes.

The affinity of PILC (as well as PCH) for toxins, such as phosphorus and others, and / or the catalytic effect of PILC can be further increased if desired by introducing a suitable dopant. In this way, the ability of the material to adsorb toxins can be further improved.

PILC has the advantage that it is a relatively cost-effective material compared to traditional precious metal-containing materials used as catalysts or, for example, sulfur traps in exhaust after-treatment systems. PILC also has a large specific surface area, which makes this material suitable for applications where one or more substances are to be adsorbed. Furthermore, PILC generally has a good ability to capture phosphorus and phosphorus-containing compounds as well as other chemical toxins in the exhaust gases and can, if desired, be doped to further improve this ability. PILC further has the advantage that they contain pores of different sizes, and can thereby accumulate impurities in the larger pores without the catalytic ability being prevented in cases where a catalytic effect is desired.

In accordance with the present invention, the PILC material is used to adsorb chemical toxins, in particular phosphorus and phosphorus-containing compounds, from the exhaust gases before the near-exhaust aftertreatment device with its catalysts for purifying the exhaust gases. To do this, the PILC material is arranged as a surface of an element in the exhaust duct which connects the combustion engine to the exhaust aftertreatment device. In order to be able to adsorb poison from the exhaust gases, said surface is exposed to the exhaust gases as they flow through the exhaust duct towards the exhaust after-treatment device. Depending on the substance or substances to be adsorbed and on which PILC material is used, the adsorption can take place by chemisorption or physiosorption.

To ensure that the material withstands the temperature conditions of the exhaust duct, typically up to at least 500 ° C, the PILC material for the surface of the element is preferably selected from a PILC that is thermally stable up to at least 500 ° C, preferably up to at least 550 ° C. PILCs containing silica columns, so-called Si-PILC, or silica and titanium oxide columns have been found to be stable up to temperatures of at least 800 ° C and are therefore examples of suitable alternatives. PILC with only titanium oxide as a pillar, so-called Ti-PILC, or PILC with an alumina pillar, so-called Al-PILC, are also conceivable. PILC materials with pillars of several different types, so-called "mixed pillars" have been shown to have extra good thermal properties.

According to an exemplary embodiment, PILC is selected from a PCH with columns of silica, or silica and titanium oxide. This material may, if desired, be doped to obtain better affinity for certain substances or impurities, in particular phosphorus and / or phosphorus-containing compounds, or for further improved thermal stability. According to an exemplary embodiment, the 16PCH material with columns of silica, or silica and titanium oxide, is doped with iron, vanadium or aluminum.

Furthermore, it is preferred that a PILC material with high affinity for phosphorus be used to thereby ensure that as high an amount of phosphorus and phosphorus-containing compounds as possible are captured before they reach the exhaust gas aftertreatment device. Substances that have been shown to be effective in capturing phosphorus and / or phosphorus-containing compounds include, for example, aluminum, zirconium, titanium, gallium, calcium, chromium, lanthanum or iron.

According to an exemplary embodiment, the PILC material is an HCP with columns of silica, or silica and titanium oxide, and doped with iron or aluminum. Such a material is stable at high temperatures and has a good ability to capture phosphorus and phosphorus-containing compounds.

According to another exemplary embodiment, the PILC material constitutes a PILC with columns of alumina, a so-called Al-PILC, preferably made of bentonite. Such a material has a good affinity for, above all, phosphate.

The PILC material can be manufactured in a conventional manner and designed for the element or for part thereof. For example, it could be extruded into a monolithic element, for example a honeycomb structure or the like as described above, or alternatively fed to a load carrier in the form of a washcoat.

Since the element is intended to capture toxins from the exhaust gases before the near exhaust gas aftertreatment device, which is intended to perform the actual purification of the exhaust gases so that they can be released into the atmosphere, the element should be designed so that it is interfering with particles in the exhaust gases. It is therefore desirable that it has a relatively large open area as described above. Preferably, it has an open area that is larger than the open area of each of the catalysts in the exhaust aftertreatment device. This also has the effect of minimizing the risk of pressure drop in the exhaust duct, which otherwise risks affecting the internal combustion engine and thus fuel consumption. 17However, the element should have as large a surface area as possible in order to be able to adsorb as much chemical toxins as possible without risking a pressure drop in the exhaust duct. For this reason, it is preferred that the element is designed in such a way that, seen in a radial cross-section of the exhaust duct, it has a honeycomb structure, a net-shaped structure or a pleated structure.

Fig. 2 schematically shows a radial cross-section of a part of honeycomb structure 10 of an element, each surface 14 of the channels 13 comprising PILC. Similarly, Fig. 3 shows a cross-section of a part of a net-shaped structure 11 where each surface 14 of the channels 13 comprises PILC and Fig. 4 a cross-section of a part of a pleated structure 12 where each surface 14 of the channels 13 comprises PILC. The structure shown in Fig. 4 also comprises spacers 15, for example in the form of disc elements, which support the pleated structure and / or increase the mechanical strength of the element. The ducts 13 as shown in Figs. 2 to 4 are arranged in such a way that their axial extent is arranged in the axial extent of the exhaust duct.

The invention according to the present description is not limited to the embodiments shown and described above, but may be modified within the scope of the appended claims. For example, the vehicle is not limited to a truck as shown in Fig. 1a but may be any vehicle that includes an internal combustion engine and an exhaust aftertreatment system as described above. Furthermore, the element need not have such a structure as shown in Figs. 2-4 as long as it allows the passage of exhaust gases through the element over a surface thereof.

Claims (1)

An exhaust aftertreatment system (1) for treating exhaust gases from an internal combustion engine (2), said exhaust aftertreatment system comprising an exhaust aftertreatment device (3) and an exhaust duct (4) arranged between an exhaust gas outlet (5) of an internal combustion engine and an inlet (6) an exhaust gas purification catalyst, characterized in that an element having a surface (14) adapted to adsorb at least one substance or compound which can deactivate a catalyst of the exhaust gas purification device is arranged in the exhaust duct (4), said surface (14) comprising a material comprising of a columned clay, PILC. Exhaust after-treatment system according to claim 1, wherein said element is releasably arranged in relation to the exhaust duct. Exhaust after-treatment system according to claim 2, wherein a wall of the exhaust duct comprises a hatch through which the element can be inserted or taken out of the exhaust duct. Exhaust after-treatment system according to claim 2, wherein the element is arranged in a first exhaust duct section which is detachably arranged in relation to a second exhaust duct section adjacent in the axial direction of the exhaust duct. Exhaust after-treatment system according to any one of the preceding claims, wherein the element comprises a plurality of channels whose axial extent is arranged to the axial extent of the exhaust duct and the element has an open area in the radial cross-section of the exhaust duct which is larger than the open area of said catalyst. Exhaust after-treatment system according to any one of the preceding claims, wherein the element has a honeycomb structure, net-shaped structure or an at least partially pleated structure. An exhaust aftertreatment system according to any one of the preceding claims, wherein the PILC material is selected from a PILC comprising columns of alumina, silica, titanium oxide or a mixture of at least two of these. An exhaust aftertreatment system according to any preceding claim, wherein the PILC material is doped to increase the affinity of the at least one substance or compound which can inactivate the at least one catalyst of the exhaust gas purifier, preferably to increase the affinity for phosphorus and / or phosphorus-containing compounds. Exhaust after-treatment system according to one of the preceding claims, wherein the PILC material is selected from a porous clay heterostructure, PCH. The exhaust after-treatment system according to claim 8, wherein the PILC material is a PCH-containing column of silica, titanium oxide, alternatively silica and titanium oxide, and is doped with iron, vanadium or aluminum. Exhaust after-treatment system according to one of the preceding claims, wherein the PILC material material is arranged as a coating on a load carrier, the coating and the load carrier together forming that element. Exhaust after-treatment system according to one of Claims 1 to 10, in which the entire element consists of the PILC material. Exhaust after-treatment system according to any one of the preceding claims, wherein the surface is free of precious metal, preferably wherein the entire element is free of precious metal. Exhaust after-treatment system according to any one of the preceding claims, wherein the element is arranged at or near a downstream end of the exhaust duct. Exhaust after-treatment system according to claim 14, wherein the element is arranged in the immediate vicinity of the exhaust inlet of the exhaust after-treatment device. Vehicle (100) comprising an internal combustion engine (2) and an exhaust after-treatment system (1) according to any one of the preceding claims, said exhaust after-treatment system adapted for after-treatment of exhaust gases from the internal combustion engine. A vehicle according to claim 16, wherein the vehicle is a truck, a bus or a passenger car.