EP2624939A2

EP2624939A2 - Exhaust-gas purification device, method for exhaust-gas purificiation, catalytic converter and pyrolysis reactor

Info

Publication number: EP2624939A2
Application number: EP11776085.0A
Authority: EP
Inventors: Robert Szolak; Alexander Susdorf; Thomas Aicher
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Priority date: 2010-10-04
Filing date: 2011-09-30
Publication date: 2013-08-14
Also published as: WO2012045423A2; DE102010049957B4; DE102010049957A1; US9074508B2; WO2012045423A3; US20130219866A1

Abstract

The present invention relates to an exhaust-gas purification device by means of which combustion exhaust gases emerging from combustion devices, in particular diesel engines, can be purified. At least a regeneration of the soot particle filter and/or of the NOx catalytic converter can be attained by means of the exhaust-gas purification device.

Description

Exhaust gas purification device, process for exhaust gas purification, catalyst and pyrolysis reactor

The present invention relates to an exhaust gas purification device with which combustion gases originating from combustion devices, in particular diesel engines, can be purified. At least regeneration of the soot particle filter and / or of the NO _x catalyst can be achieved with the exhaust gas purification device. In this case, a soot particle filter and / or a catalyst for reducing the content of nitrous gases (NO _x catalyst) is introduced into the exhaust gas stream of the combustion device. The core idea of the present invention is based on the fact that in a preceding pyrolytic process of liquid or gaseous carbonaceous fuels by means of a pyrolysis process, excluding gas containing oxygen or oxygen, a gas is produced which predominantly comprises hydrogen or hydrogen Synthesis gas, ie carbon monoxide and hydrogen contains. This pyrolytically produced hydrogen-rich gas mixture / synthesis gas is used to heat a soot particle filter over an oxidation catalyst or LNT (Lean Temperature N0 _X Trap).

This pyrolytically produced hydrogen-rich gas mixture / synthesis gas is also used to reduce the nitrous gases in the NO _x storage catalytic converter. The present invention also relates to a corresponding process for exhaust gas purification, suitable catalysts for the pyrolysis process and a corresponding pyrolysis reactor.

The share of diesel vehicles in new registrations in Germany more than doubled from 19% to 42% between 1993 and 2003. The reason for this are mainly the favorable fuel consumption and due to a high torque at low speeds good driving characteristics to call. At the same time, the exhaust emission limits in Europe have sharply tightened in recent years, in particular the soot particles (PM) and NO _x emissions are to be further reduced. Figure 1 (Ministry of Environment and Transport Baden-Württemberg, 2005) shows the permissible emission limits for commercial vehicles in Europe.

With the introduction of the Euro 4 standard in 2005, the upper limit for particulate emissions has been greatly reduced since 1993.

Figure 2 shows how the particle and NO _x emissions could previously be reduced by motor measures. In addition, the reduction of particulate matter and NO _x emission limits is represented by the European emission standards. With the most modern engine technologies, the Euro 4 standard can be met. With view on Euro 5 standard (January 2009), the use of particulate filters and NO _x reduction measures will inevitably become necessary. In addition, the prescribed emission limit values will also be introduced for commercial and off-road vehicles. An expansion to stationary applications will follow as well. Hereinafter, known from the prior art

Measures for the regeneration of soot particle filters or NO _x removal, as used in previous exhaust gas purification processes, are described: 1. Regeneration of soot particle filters

Particulate filters are loaded with soot until a maximum allowable exhaust backpressure is reached.

Then they have to be regenerated. For regeneration usually exhaust gas temperatures of more than 600 ° C are required at the filter inlet. However, such high temperatures are usually only achieved at high speeds in close to full load operating points. Therefore aids for soot erosion are necessary both for motors in mobile use as well as for stationary applications in combined heat and power plants.

Basically, a distinction can be made between active and passive regeneration. In practice, however, combinations of both are often used. FIG. 3 shows a listing of the common methods for the regeneration of soot particle filters.

In the active regeneration method, the exhaust gas or the particle filter is heated by a foreign energy to the required oxidation temperature. The systems of passive regeneration enable filter regeneration under certain operating conditions without targeted initiation of the oxidation process. In the passive regeneration is no

Foreign energy needed.

A common method for regenerating the soot particle filter is the combination of CRT (continuous regeneration trap) and post-injection. The

CRT system is a continuous regeneration system. Here, an oxidation catalyst is attached in front of the particulate filter, which oxidizes the NO in the exhaust gas to N0 ₂ . The N0 ₂ can oxidize the carbon black at significantly lower temperatures than the molecular weight

Oxygen in the exhaust gas (about 450 ° C). Depending on the operating condition, however, it is not possible to provide the necessary N0 ₂ tight. If the exhaust backpressure exceeds a certain value due to soot loading, fuel is injected in front of the oxidation catalyst. The fuel oxidizes in the catalyst and thereby heats the soot particle filter. The soot can then be burned with the N0 ₂ and the oxygen.

Soot particle filters can not yet be effectively regenerated in all operating points of a vehicle. Especially in low load operation (for example, in city operation), the exhaust gas temperature is often too low to completely oxidize the injected fuel. At low exhaust gas temperatures, condensation effects can occur on the oxidation catalyst, and the injected fuel can then occupy the catalyst and possibly damage it. 2. NO _x removal

There are currently two NO _x removal systems, the SCR method and the NO _x (LN NOx trap) storage catalytic converter (LNT).

In the SCR method, the reducing agent (a urea-water mixture) is fed into the exhaust line of the engine. In the hot exhaust gas, the urea is converted to ammonia. In the SCR catalyst, the

Nitrogen oxides are converted to water and nitrogen with ammonia. This procedure is currently used by LKW ^ s. The SCR process is very efficient at temperatures> 300 ° C, rather ineffective at exhaust gas temperatures <200 ° C.

The nitrogen oxides in the exhaust gas are temporarily stored in an "NO _x" storage catalytic converter in the "lean" mode (engine air ratio> 1) .The nitrogen oxides are oxidized in the catalyst layer to N0 ₂ and subsequently adsorbed on the storage material Regeneration takes place in substoichiometric engine operation (engine air ratio ^ 1), where the stored N0 ₂ is converted into N ₂ with the reducing agents HC (hydrocarbons) and CO _2. The storage material is regenerated and is available for new NO _x deposits. This system is of particular interest to cars as it can be constructed more compactly than the SCR method, with regeneration usually taking place at temperatures of> 250 ° C. In urban areas, for example, the storage catalytic converter can only heat up to to 150 to 180 ° C. A reduction of the storage capacity There is only limited possibility for talysators. There are currently several ways to create a syngas. It can be the usual reforming processes, such as steam reforming, CPox

(Catalytic Partial Oxidation) and the ATR (Autothermal reforming) are used. In steam reforming, water vapor is required in addition to the fuel. The reforming is an endothermic process, so it must be supplied from the outside heat. The space velocity in steam reforming is low compared to the ATR or CPox. In addition, carbon is formed at too low temperatures and / or too little water. In partial oxidation, the fuel is reacted with oxygen to form a synthesis gas. For the CPox, it is important that the process parameters temperature and air ratio are set precisely, otherwise carbon is formed. The ATR requires water vapor and air. Similar to the previously described reforming processes, this process is susceptible to carbon formation.

The carbon blocks the active sites in the catalyst and is also the germ cell for the formation of new carbon. The catalyst becomes inactive and must be regenerated. The catalysts used in the reforming are not designed for such regeneration cycles. The occurring, higher temperatures can lead to sintering effects and significantly reduce the activity of the catalyst. The processes become inefficient. In addition, precious metals are usually used as active components. The catalysts used in reforming are therefore very expensive. Exhaust aftertreatment systems must be simple, cheap and robust in the first place. WO 2004/090296 discloses such a reforming unit for generating hydrogen by steam reforming, partial oxidation of hydrocarbons and / or mixed forms thereof. The reforming reactor described here and the synthesis gas produced therewith can be used for NO _x removal and for regeneration of soot particle filters. The reforming unit can be positioned directly in the exhaust gas chamber and operated with exhaust gas. For the

Steam reforming, the water contained in the exhaust gas and the residual oxygen can be used.

Disadvantages of this process over the pyrolysis are:

• The noble metal based catalyst used is very expensive.

• The process is very susceptible to carbon formation.

• Integration of the reformer in the exhaust gas space seems very difficult due to the changing conditions and the susceptibility to carbon formation.

Proceeding from this, it was therefore an object of the present invention to provide a device for exhaust gas purification and a corresponding method, which avoids the disadvantages of the prior art described above. It was also an object of the present invention to provide a corresponding pyrolysis catalyst and a method for producing this catalyst and a pyrolysis reactor, which allow the production of a hydrogen-rich gas mixture / synthesis gas by pyrolytic means. According to the invention, therefore, an exhaust gas purification device with the features of claim 1 is proposed. Likewise, according to the invention, a method for exhaust gas purification according to claim 12 is provided. The invention also relates to a catalyst according to claim 19 and to a process for the preparation of the catalyst according to the invention as claimed in claim 20. According to the invention, a pyrolysis reactor which makes use of the catalyst according to the invention is also provided according to claim 21. According to the invention, there is thus provided an exhaust gas purification device which comprises a) at least one pyrolysis reactor comprising intermittently anaerobic catalytic pyrolysis of fuels selected from the group consisting of liquid or gaseous hydrocarbons, oxygen-containing fuels (US Pat. eg alcohols, bio oils, biodiesel, pyrolysis oils), liquid or gaseous hydrocarbon mixtures or gas mixtures containing hydrocarbons, preferably fuels, in particular diesel fuel and aerobic regeneration of the catalyst, the production of a gas mixture containing hydrogen and a gas mixture containing hydrogen

Crack products from the feedstock allows, as well

b) downstream of the pyrolysis reactor

i. at least one oxidation catalyst

and / or a particulate filter and / or ii. at least one catalyst for reducing the content of nitrous gases (NO _x catalyst) and / or

iii. at least one Lean NO _x trap (LNT)

and / or a particulate filter,

wherein the oxidation catalyst and / or the soot particle filter and / or the NO _x storage and / or LNT and particulate filters in the exhaust stream of a combustion device, preferably an internal combustion engine, in particular a diesel engine is / are arranged.

According to the invention, it is thus provided that a pyrolysis reactor is connected upstream of either an oxidation catalyst and a soot particle filter or a NO _x catalyst or an LNT. Likewise, there is the possibility that the soot particle filter nor an oxidation catalyst (either as a separate component in the exhaust stream or between pyrolysis and

Soot particle filter) is connected upstream. This possibility also applies to the LNT. In addition, all components can be combined to a total exhaust gas purification system, for example, by soot particulate filter and NO _x catalysts are connected in series.

The exhaust gas purification device according to the invention is based on the principle that, for example, soot particles and / or nitrous gases which are contained in the offgas stream originating from a combustion device are separated from the exhaust gas flow by means of soot particle filters or NOx catalysts. to

Soot particle filter regeneration and / or for the regeneration of NO _x storage catalysts, a hydrogen-containing gas mixture is used according to the invention. This hydrogen-containing gas mixture originates from a pyrolysis reactor, the pyrolysis reactor based on an anaerobic reaction principle. In this case, gaseous or liquid hydrocarbon-containing fuels are reacted under anaerobic conditions, ie, with the exclusion of air, oxygen or water vapor, to form a gas mixture containing hydrogen. The hydrogen-containing gas mixture produced from the fuels during anaerobic pyrolysis can be, for example, a gas mixture of hydrogen and alkanes, alkenes and / or alkynes produced from the fuel. For example, the gas mixture may contain hydrogen and methane. However, it is likewise possible for the gas mixture to contain residual fuels and / or cracked products in addition to the hydrogen.

Most preferably, in the pyrolysis, a synthesis gas-containing gas mixture, i. a gas mixture containing not only hydrogen but also carbon monoxide.

The above-mentioned synthesis gas-containing gas mixture may consist for example of pure synthesis gas, but also comprise gas mixtures which, in addition to the essential components of the synthesis gas, ie CO and H ₂ , may also contain hydrocarbons, such as alkanes, alkenes, especially methane. In addition, residues of the fuel used or cracked products, ie fragments of the hydrocarbons used, are also conceivable in the synthesis gas-containing gas mixtures obtained.

Particularly preferably usable fuels are, for example, gaseous hydrocarbons, such as methane, ethane, propane, butane, etc., or mixtures thereof, liquid hydrocarbons, but also mi about this. Particular preference is given to mention diesel, heating oil, gasoline, kerosene, etc. Likewise, oxygen-containing organic compounds, such as, for example, alcohols, organic acids, organic esters, biodiesel, bio oils, pyrolysis oil (for example flash pyrolysis), etc., can be used as fuels suitable according to the invention. Of course, all mixtures of the aforementioned components are possible.

Compared with the solutions known from the prior art, the new emission control device offers several advantages.

The pyrolysis system, compared to other syngas generators, such as steam reformer, CPox (Catalytic Partial Oxidation), or ATR (autothermal reforming), more robust, the control much easier. Parameters such as air ratio and temperature do not have to be set exactly and no additional water is needed. The common reforming processes require water and / or air. During pyrolysis, in addition to the fuel no other reactant is needed. The regeneration can take place with a very low air volume flow or with exhaust gas.

The formation of carbon is part of the reaction during pyrolysis. In the common

Reforming catalysts regeneration is not readily possible, since the occurring during regeneration high temperatures can damage the catalyst.

The pyrolysis system can replace air for Regeneration can be operated with exhaust gas, thereby eliminating the need for an air compressor or a larger compressed air tank. The regeneration can also be operated with a low air flow. Components with high electrical consumption, such as air pumps or a large fan, are eliminated. , Due to the intermittent operation with

In one reactor (pyrolysis regeneration) or in two reactors, which pyrolyze and regenerate alternately, the system only has to be heated up at the beginning. Thereafter, the system can be operated without external heat.

5. Simple operation management; the diesel and the

Air is switched on alternately. If the pyrolysis reactor is preceded by a fuel steamer which evaporates the liquid fuel by a partial oxidation, the diesel is turned on in the interval, the air or the exhaust gas are continuously passed through the pyrolysis system.

6. The resulting in the regeneration gas preferably contains a high carbon monoxide content. The carbon monoxide can in turn be ignited at the oxidation catalytic converter at low temperatures. Thus, both gas compositions after pyrolysis and after regeneration for the exhaust aftertreatment are advantageous.

In a preferred embodiment, the pyrolysis reactor comprises a housing inside which the catalyst is arranged, wherein the catalyst comprises a support which is at least partially filled with an alloy, containing iron and nickel, is coated.

Such a catalyst corresponds to the catalyst claimed according to the invention with claim 19.

There is currently no commercially available catalyst suitable for a pyrolysis system. A catalyst has been developed that is thermally and long-term stable. In the development of the catalyst has been dispensed with expensive precious metals, as the active component, therefore, a nickel alloy was used, which, for. is applied on a silica support. The composition of the active component, the preparation method and the carrier have a great influence on the gas composition and the stability of the catalyst. Many potential supports and active components have been tested and studied for thermal stability. The developed catalyst can pyrolyze a variety of fuels, gaseous and liquid fuels can be used, and the nature and composition of the fuel also affects the product gas composition.

The catalyst developed (see below) is cheap and robust. It could be proven in long-term experiments that the catalyst is thermally stable (up to> 1000 ° C). The catalyst contains no precious metals, so it can be produced very inexpensively and is therefore particularly well suited for exhaust aftertreatment. The pyrolysis can be operated in a high power range.

In a further preferred embodiment, the molar ratio between iron and nickel in the Catalyst according to the invention, which is particularly suitable for use in a pyrolysis reactor in an exhaust gas purification device according to the present invention, between 3: 1 and 1: 5, preferably between 1: 2 and 1: 4, in particular between 1: 2.8 and

1: 3.2.

In a further preferred embodiment of the catalyst according to the invention, the total content of nickel and iron, based on the carrier, is between

0.5 and 15 wt .-%, preferably between 1 and 10% by weight, particularly preferably between 2.5 and 7.5 wt .-%.

Furthermore, it is advantageous if the material of the carrier is selected from the group consisting of ceramic materials, in particular silicon dioxide, silicon carbide, aluminum oxide, silicates, in particular aluminosilicates, zeolites, cordierite and / or metals.

Particularly preferred geometric shapes of the catalyst according to the present invention are in the form of a powder, a granulate, a honeycomb, a foam, a mesh or a sheet.

In a particularly preferred embodiment, the exhaust gas purification device comprises a fuel evaporator, which is arranged in the housing of the pyrolysis reactor and upstream of the catalyst or upstream of the pyrolysis reactor as a separate component. Such fuel evaporators and methods for their operation are known for example from the publications EP 0 716 225 AI, DE 10 2006 060 669 AI and DE 10 2010 012 945. These evaporators can be used in particular in the exhaust gas purification device according to the invention. The functional principle Such evaporator is based on partial oxidation of the fuels with, for example, air, whereby thermal energy for fuel evaporation (enthalpy of vaporization) is provided. The components thus formed hydrogen and carbon monoxide and by

Cracking reactions formed shorter hydrocarbons and olefins offer advantages in:

a) NO _x removal (see Table 2) and

b) Ignition temperature in the oxidation catalyst for the particle filter regeneration.

The pyrolysis reactor according to the invention can be formed in one piece, i. a gas inlet and

-auslass and a catalyst arranged therebetween. Such a reactor may be operated in alternating operation between pyrolysis and regeneration, i. intermittently, operated.

In a further advantageous embodiment, the pyrolysis reactor is formed at least in two parts along its direction of flow. In such a two-part embodiment of the pyrolysis reactor at least two separate chambers are present, which may be of identical construction. In both chambers at least one catalyst is present, which has the properties described above. Each chamber may be separately preceded by a fuel evaporator as described above. However, it is also possible that only one fuel evaporator is present, with which the two chambers of the reactor can be controlled at different times. Such a configuration of the pyrolysis reactor allows the intermittent catalytic pyrolysis and aerobic regeneration of the

Catalyst delayed in the two chambers off can run; ie while, for example, the pyrolysis reaction takes place in the first chamber, the regeneration can take place in the second chamber and vice versa. The two processes are preferably carried out in alternating operation between the two chambers. Since the two chambers are in direct proximity to one another, the thermal energy required for pyrolysis can be supplied directly by the regeneration process, in which carbon deposited on the catalyst surface is converted into carbon monoxide or carbon dioxide by oxidation of oxygen. In this respect, a particularly efficient and constant operation of the pyrolysis reactor and thus the entire exhaust gas purification device is possible. The two chambers can be arranged side by side, but it is also possible that one chamber is formed concentrically in the other chamber.

It is likewise preferred if the pyrolysis reactor has at least one inlet in the form of at least one air supply and / or at least one nozzle for supplying or injecting the fuels.

According to the invention, diesel particulate filters are particularly suitable as soot particle filters, in which case wall-flow filters or bypass filters are particularly preferred.

Preferred suitable NO _x catalysts are selected from the group consisting of NO _x storage catalysts (for example LNT).

It is also conceivable that the pyrolysis reactor of the above-described exhaust gas purification device in the main stream or in a side stream of the exhaust gas stream the incinerator is arranged, or is formed as a separate component. In such an embodiment, exhaust from the combustor may be used directly to regenerate the catalyst.

According to the invention, a method is also provided for the exhaust gas purification of exhaust gases originating from a combustion device by soot particle filter regeneration and / or at least partial removal of soot particles and / or nitrous gases from the exhaust gases, in which at least one oxidation catalyst and / or a soot particle filter and / or at least one catalyst for reducing the content of nitrous gases (NO _x catalyst) or LNT (lean NO _x trap) and / or a soot particle filter is arranged, wherein during the combustion process, the at least one soot particle filter and / or at least one NO _x catalyst at least temporarily with intermittently proceeding anaerobic catalytic pyrolysis of fuels selected from the group consisting of liquid or gaseous hydrocarbons, liquid or gaseous hydrocarbon mixtures, oxygen-containing fuels (eg alcohols, Bio-oils, biodiesel, pyrolysis oils) or gas mixtures which contain hydrocarbons, preferably fuels, in particular diesel fuels, hydrogen-rich gas mixtures or synthesis gases produced and hydrogen-containing gas mixtures produced by aerobic regeneration of the catalyst, in particular gas mixtures or synthesis gases containing hydrogen and carbon monoxide. The pyrolysis takes place in the absence of oxygen, air and / or water vapor, while in the regeneration process, an oxygen-containing Gas mixture, such as air or oxygen-containing combustion gases, are abandoned. Pyrolysis and regeneration are carried out alternately (= intermittent).

The method according to the invention can be carried out particularly preferably with the exhaust gas purification device described above.

In the method according to the invention, therefore, the fuel used, depending on the type, to a hydrogen-rich product gas or to a synthesis gas to set. In pyrolysis hydrocarbons are thermochemically cleaved at higher temperatures, preferably between 500 and 1000 ° C. The Spaltun produces solid carbon and a product gas, which, depending on the fuel and reaction condition, has a high hydrogen concentration. The decomposition he follows under the action of the catalyst without the addition of oxygen or other reactants, but only under the action of heat.

In aerobic pyrolysis, carbon is deposited on the catalyst. This carbon can be removed under oxidative conditions during the regeneration phase. In this case, oxygen or an oxygen-containing gas mixture is introduced in example exhaust gas into the pyrolysis reactor and the deposited carbon and / or residual fuel material to a hydrogen and / or carbon monoxide-containing gas mixture implemented. Also this mixture Gasge can in the subsequent emission control devices, such as soot particulate filter and / or NO _x catalyst, abandoned and used there for further purification of exhaust gas and / or regeneration of the exhaust gas purification devices used become .

The newly developed process is simple, cheap and robust and therefore particularly well suited for exhaust aftertreatment. Depending on the fuel used and the choice of the duration of each pyrolysis step or regeneration step, different product gases can be obtained. In this regard, reference is made in particular to the gas mixtures already described above.

In an advantageous embodiment of the method, in the case of catalytic pyrolysis, the fuels are contacted with a catalyst which catalyzes the pyrolysis and at temperatures between 300 and 1000.degree. C., preferably between 500 and 900, more preferably between 700 and 800.degree Pyrolyzed hydrogen containing gas mixture. It is further preferred if the pyrolysis is carried out alternately with a regeneration phase, during which oxygen or an oxygen-containing gas mixture, but no fuel, is supplied to the reactor during the regeneration phase.

In the aforementioned alternating operation of the pyrolysis reactor, the latter is operated alternately by supplying the fuel and carrying out a pyrolysis with exclusion of oxygen, stopping the fuel injection in the so-called regeneration phase or a regeneration step and adding oxygen or oxygen-containing gas mixtures to the pyrolysis reactor. As a result, oxidation of the carbon layer formed on the catalyst surface during pyrolysis takes place; Depending on the reaction conditions, this is converted into carbon monoxide or carbon dioxide. set. The catalyst surface is exposed again; the catalyst is regenerated.

In a particularly preferred embodiment, a pyrolysis reactor is used along its

Direction of flow is formed at least two parts, wherein in the two parts of the pyrolysis pyrolysis is carried out in antipode in alternation with the regeneration phase. In an antipodean operation of such a two-part

Pyrolysis reactor takes place in two different parts of the pyrolysis reactor, for example, in the event that the pyrolysis reactor consists of two parts, in each case a part of the pyrolysis reactor, each separately and simultaneously, a pyrolysis instead of a regeneration, i. Pyrolysis is carried out in the first part of the pyrolysis reactor and regeneration in the other part of the pyrolysis reactor. After regeneration of the catalyst, the pyrolysis is then carried out in the other part. At the same time, the first part is being regenerated. Since the regeneration process is exothermic, the other part in which the endothermic pyrolysis takes place is simultaneously supplied with the necessary thermal energy. In this case, the pyrolysis catalyst needs no external power supply to ensure a continuous pyrolysis. In particular, in the case that liquid fuels are used, an evaporation of these fuels is carried out before the pyrolysis step. These fuels are converted to the gaseous state and then fed to the pyrolysis step.

It is also preferred if the evaporation of the liquid entrained enthalpy of vaporization is provided by partial oxidation of the liquid fuels used and / or by heat exchange with the resulting from the combustion device exhaust gases. For this purpose, for example, the fuel evaporator described above can be used.

It is further preferred that the catalyst and / or the catalyst be used before or at the beginning of the pyrolysis

Pyrolysis reactor and / or the evaporator is heated by a separate heating and / or by an oxidation of the fuels and / or by heat exchange with the combustion exhaust gases.

According to the invention, as already described above, a catalyst is likewise provided which comprises a ceramic carrier which is at least partially coated with an alloy containing iron and nickel.

With regard to advantageous embodiments of the catalyst, reference is made to the statements already made above.

The invention also provides a process for preparing the catalyst described above, in which a ceramic support material with an aqueous solution containing iron and nickel salts and a complexing agent, wetted, dried and then calcined at temperatures above 200 ° C, wherein the complexing agent is used overstoichiometrically with respect to the total amount of iron and nickel salts.

In the process, a complexing agent is preferably used. set to increase the dispersity of iron and nickel on the support surface. Preferred complexing agents are organic acids, in particular di- or higher valent acids, such as citric or tartaric acid.

In a preferred embodiment, as

Iron and / or nickel salts in particular their nitrates, chlorides, bromides, citrates, tartrates or mixtures thereof used.

In a further preferred embodiment of the production method, a powder, a granulate, a honeycomb-shaped body, sheets or corresponding foam-like materials is used as the carrier material.

Further, it is preferred if the drying is carried out at temperatures between 20 and 190 ° C and / or over a period of between 12 hours and 5 days.

Preferred conditions which prevail in the calcination, for example, temperatures between 400 and 1000 ° C, preferably between 500 and 700 ° C.

The calcination is preferably carried out over a period of between 1 and 12 hours, preferably between 3 and 5 hours. According to the invention, a pyrolysis reactor is likewise provided, which comprises a housing with at least one front-side inlet and at least one rear-side outlet and a catalyst, which is arranged in the housing between inlet and outlet, as described above. Preferred embodiments of the pyrolysis reactor, such as the two-part design, have already been described in detail above.

The present invention will be explained in more detail with reference to the following embodiments and examples, without limiting the invention to the illustrated embodiments.

Regeneration of soot particle filters

Experiments have shown that the ignition temperature in the oxidation catalyst (light-off temperature) can be significantly reduced by introducing a synthesis gas. The experiments were carried out once with and once without NO _x in the exhaust gas (250 ppm).

Table 1 shows the light-off temperature of a synthesis gas on the oxidation catalyst with and without NO _x .

Table 1

The experiments have shown that initiating a

Synthesis gas compared to the post-injection with liquid fuels (CRT with post-injection) offers great advantages, the ignition temperature could be significantly reduced. The particle filter can be regenerated with syngas in all operating points.

NO _x removal Likewise, tests were carried out for NO _x removal from diesel exhaust gases at various reducing agents and exhaust gas temperatures. The experiments were carried out with HC, CO and mixtures of HC, CO and H ₂ .

Table 2 shows the NO _x conversion at different exhaust gas temperatures and reducing agents.

Table 2

-Distance from diesel exhaust

The tests have shown that the NO _x storage catalyst can only be regenerated with HC as reducing agent at higher exhaust gas temperatures (> 200 ° C). The best results were obtained with a blend of HC, CO and H _2, has already a NO _x conversion at an effluent temperature of 150 ° C can be achieved of 50%. The NO _x concentration could thus be significantly reduced even in city operation.

Tests have shown that pyrolysis with pre-evaporated diesel fuel is possible. Amongst others, the patented fuel evaporators, as in EP 0 716 225 A1 and DE 10 2006 060 669 A1 and DE 10 2010 012 945 described, used ^¬ the. Further evaporation processes are conceivable, and the fuel can also be added in liquid form. The fuel / vapor is reacted in the pyrolysis reactor in the manner described above according to the invention to a synthesis gas.

A fuel vaporizer was coupled to a pyrolysis reactor. Evaporator and pyrolysis reactor are housed in a reactor housing, thus a uniform flow of the fuel vapor is achieved at the catalyst inlet and the system can be very compact. FIG. 4 shows a first embodiment of a pyrolysis reactor according to the invention.

In the reactor (left picture), the fuel vapor in the pyrolysis reactor is converted to a synthesis gas. The fuel supply is interrupted when the catalyst is loaded with carbon. The pyrolytic reaction carried out in this case is carried out under exclusion of oxygen, in particular of air or oxygen-containing exhaust gases, ie anaerobically. FIG. 4 shows an additional air inlet, which, however, only serves to supply the fuel evaporator upstream of the catalytic converter in a substoichiometric manner with air. In this case, partial oxidation of the fuel used takes place, ie a part of the fuel is oxidized to CO or C0 ₂ . The thermal energy released in this process is used to vaporize the fuel. Preferred fuel evaporators are known from the patent applications already mentioned above and can be used according to the invention in the pyrolysis reactor. The right picture shows the regeneration of the catalyst with air. If the evaporation operated with air, the air flow can flow continuously through the reactor. The fuel evaporator is not shown in the right part of Figure 4 for reasons of clarity. Here (right picture) is the attached carbon with

Air oxidized to CO and C0 ₂ . The process according to the invention now takes place in such a way that alternately, ie intermittently, an anaerobic pyrolysis (left part of FIG. 4) is operated with the regeneration of the catalyst shown in the right-hand part of FIG. The fuel evaporator can also be operated during the pyrolysis with oxygen-containing exhaust gases. The process only needs to be heated up at the beginning.

During pyrolysis, the temperature of the catalyst decreases due to the endothermic pyrolysis reaction, and the heat released during the regeneration heats the reactor. It must therefore be supplied during operation, no heat from the outside.

Both product gases, the synthesis gas after pyrolysis and the regeneration gas, can lower the ignition temperature on the oxidation catalyst. The regeneration gas contains up to 30 vol.% CO, so pyrolysis is particularly well suited for use in exhaust aftertreatment systems.

FIG. 5 shows the results of a "diesel vapor

Pyrolysis at different thermal input powers (based on the calorific value of diesel). The experiments were carried out with a Katatysatorvolumen of 77 ml.

FIG. 5 shows the gas composition during pyrolysis at different input powers (relative to FIG on the amount of diesel at the inlet of the evaporator). The experiments have shown that the pyrolysis can be operated with a high thermal input power.

The experiments have shown that the longer hydrocarbon chains are cracked even at higher thermal input powers. This results in shorter chains and above all a high proportion of olefins. The measurements have shown that at 4 kW _th and after cooling the product gas to 20 ° C, almost all hydrocarbons are gaseous. The hydrocarbon chains could therefore be cracked to <C 8. In the regeneration of soot particle filters, the gas mixture can thus be ignited at significantly lower temperatures on an oxidation catalyst. The gas composition (H ₂ , CO, HC) also offers, as shown in Table 2, great advantages in the conversion of NO _x .

The regeneration of the catalyst can be carried out instead of air with exhaust gas. The residual oxygen in diesel engines is completely sufficient. The water contained in the exhaust gas also offers advantages; The carbon can also become one with water

Synthesis gas to be implemented. This reaction is endothermic and can prevent any possible temperature peaks during regeneration. The reactor can be designed to have two

Catalyst beds (honeycomb, etc.) contains, which pyrolyze alternately and regenerate. During regeneration, the heat is provided for pyrolysis. FIG. 6 shows a possible design variant. The fuel is alternately fed into the left or the right fuel evaporator. directs.

FIG. 6 shows two fuel evaporators and pyrolysis reactors, which are spatially separated. The two beds are alternately pyrolyzed and regenerated. The regeneration cycle supplies the heat for the pyrolysis. To illustrate the procedure, the fuel evaporator is not shown in the two parts of the reactor in Figure 6, in which the regeneration takes place, but this is still present in the respective part of the reactor.

The fuel can be passed as a further modification directly without pre-evaporation in the pyrolysis reactor (see Figure 7). In the case of fuels without oxygen compounds, thermodynamically predominantly H ₂ and CH _{4 are formed} . The introduction of the fuel can take place via a nozzle. The fuel and the air for regeneration are given intermittently and alternately.

FIG. 7 shows the direct injection pyrolysis system. The fuel and the air for regeneration are given up intermittently.

The direct injection can be extended with a second catalyst bed (see Figure 8). While the fuel is pyrolyzed in one catalyst bed, the other catalyst bed is regenerated. The regeneration cycle provides the heat for pyrolysis. The temperature does not cool down so much during pyrolysis.

All design variants can be cylindrical or planar. The following section describes the preparation and the composition of a catalyst according to the invention which can be operated with a wide range of starting materials.

As support of the catalyst Si0 ₂ with a low surface area (support of Alfa Aesar, low

Surface) used. The active components of the catalyst are Fe and Ni. The molar ratio between Fe and Ni may be in the range of 3/1 to 1/5. The total metal content can be between 0.5 and 15 wt .-%. The optimum Fe / Ni ratio is 1/3. The catalyst was prepared as follows (the data refer to the coating of 500 g

Si0 ₂ ).

Preparation of a solution of:

60, 88 g Ni (NO ₃ ) ₂ × 6H ₂ O,

28.15 g of Fe (NO ₃ ) ₃ x 9H ₂ O,

88 g of citric acid,

filled with 53.6 g H ₂ O,

Impregnation of the Si0 ₂ support with the solution, drying

- 2 days at 25 ° C,

- 1 day at 88 ° C,

- 10 hours at 100-120 ° C,

calcination

- 4 hours at 600 ° C.

Claims

claims

An exhaust gas purification device, comprising

a) at least one catalyst having pyrolysis reactor, by means of intermittently proceeding anaerobic catalytic pyrolysis of fuels selected from the group consisting of liquid or gaseous hydrocarbons, oxygen-containing fuels (eg alcohols, bio-oils, biodiesel, pyrolysis oils), liquid or gaseous hydrocarbon mixtures or gas mixtures, the Contain hydrocarbons, preferably fuels, especially diesel fuel and aerobic regeneration of the catalyst, the production of a hydrogen-containing gas mixture and a hydrogen-containing gas mixture with cracking products from the feed allows, and

b) downstream of the pyrolysis reactor

i. at least one oxidation catalyst and / or a soot particle filter and / or ii. at least one catalyst for reducing the content of nitrous gases

(ΝΟχ-catalyst), and / or

iii. at least one Lean NO _x trap (LNT)

and / or a particulate filter,

wherein the oxidation catalytic converter and / or the soot particle filter and / or the NO _x storage catalytic converter and / or LNT and soot particle filter in the exhaust gas flow of a combustion device, vorzugt an internal combustion engine, in particular a diesel engine is / are arranged.

Exhaust gas purification device according to the preceding claim, characterized in that the pyrolysis reactor comprises a housing inside which the catalyst is arranged, the catalyst comprising a support which is at least partially coated with an alloy containing iron and nickel.

Exhaust gas purification device according to the preceding claim, characterized in that the molar ratio between iron and nickel is between 3: 1 and 1: 5, preferably between 1: 2 and 1: 4, in particular between 1: 2.8 and 1: 3.2.

Exhaust gas purification device according to one of the two preceding claims, characterized in that the total content of nickel and iron, based on the carrier between 0.5 and 15% by weight, preferably between 1 and 10 wt .-%, particularly preferably between 2.5 and 7.5% by weight.

Exhaust gas purification device according to one of claims 2 to 4, characterized in that the material of the carrier is selected from the group consisting of ceramic materials, in particular silicon dioxide, silicon carbide, alumina, silicates, in particular

Aluminosilicates, zeolites, cordierite and / or metals.

Exhaust gas purification device according to one of claims 2 to 5, characterized in that the catalyst is in the form of a powder, a granulate, a honeycomb, a foam, a network or a sheet. Exhaust gas purification device according to one of the preceding claims, comprising a fuel evaporator, which is arranged in the housing of the pyrolysis reactor and upstream of the catalyst or upstream of the pyrolysis reactor as a separate component.

Exhaust gas purification device according to one of the preceding claims, characterized in that the pyrolysis reactor along its flow direction

i. is formed in one piece and / or

ii. at least two parts is formed.

Exhaust gas purification device according to one of the preceding claims, characterized in that the pyrolysis reactor at least one inlet in the form

a) at least one air supply, and / or

b) at least one supply of the fuels

(For example, nozzle, capillary tube, etc.).

Exhaust gas purification device according to the preceding claim, characterized in that

a) the soot particle filter is a diesel particulate filter and in particular is selected from the group consisting of wall-flow filters and / or bypass filters,

b) tor the soot particle filter or an oxidation catalysts LNT (Lean _NOx Trap) arranged upstream, and / or c) of the NO _x catalyst is selected from the group consisting of NO _x -Speicherkatalysa- factors, such as LNT (Lean NO _x Trap). Exhaust gas purification device according to one of the preceding claims, characterized in that the pyrolysis reactor is arranged in the main stream or in a side stream of the exhaust gas stream of the incinerator, or is formed as a separate component.

A method for purifying the exhaust gases from exhaust gases originating from a combustion device by soot particle filter regeneration and / or at least partial removal of soot particles and / or nitrous gases from the exhaust gases, in which at least one oxidation catalyst and / or a soot particle filter and / or at least one catalyst for reducing in the exhaust stream of the combustion device the content of nitrous gases (NO _x catalyst) is arranged, characterized in that during the combustion process, the at least one particulate filter and / or at least one NO _x catalyst at least temporarily with intermittently proceeding anaerobic catalytic pyrolysis of fuels selected from the group from liquid or gaseous hydrocarbons, liquid or gaseous hydrocarbon mixtures, oxygen-containing fuels (eg alcohols, bio-oils, biodiesel, pyrolysis oils) or gas mixtures containing hydrocarbons, Preferably, fuels, in particular diesel fuels, produced, hydrogen-rich gas mixtures or synthesis gases and by aerobic regeneration of the catalyst generated carbon monoxide-containing gas mixtures or synthesis gases, is charged. Method according to the preceding claim, characterized in that in the catalytic pyro ^¬ lyse the fuels contacted with a pyrolysis catalyzing catalyst and at temperatures between 300 and 1000 ° C, preferably between 500 and 900, more preferably between 700 and 800 ° C to a Hydrogen-containing gas mixture is pyrolyzed / become.

Method according to one of the two preceding claims, characterized in that the pyrolysis is carried out alternately with a regeneration phase, wherein the reactor oxygen or an oxygen-containing gas mixture during the regeneration phase, but no

Fuel is supplied.

Method according to the preceding claim, characterized in that a pyrolysis reactor is used which is along its direction of flow

i. is formed in one piece and pyrolysed and regenerated in alternating operation,

ii. at least two parts is formed, wherein in the two parts of the pyrolysis at least two catalysts antipodal pyrolyzing and regenerate.

Method according to one of claims 12 to 15, characterized in that, in the event that liquid fuels are used, before the pyrolysis step, an evaporation is carried out and the fuels are then supplied to the pyrolysis step in gaseous form. Method according to the preceding claim, characterized in that the required for vaporization of the liquid fuels Verdampfungsent ^¬ enthalpy is provided by partial oxidation of liquid fuels and / or used by heat exchange with the stemming from the combustion device exhaust.

Method according to one of claims 12 to 17, characterized in that before or at the first onset of pyrolysis of the catalyst and / or the pyrolysis reactor and / or the evaporator by a separate heating and / or by an oxidation of the fuels and / or by heat exchange with the combustion exhaust gases is heated.

A catalyst comprising a ceramic support at least partially coated with an alloy containing iron and nickel.

A process for the preparation of a catalyst according to the preceding claim, wherein a ceramic support material with an aqueous solution containing iron and nickel salts and a complexing agent, wetted, dried and then calcined at temperatures above 200 ° C, wherein the complexing agent with respect to the total amount of Iron and nickel salts are used more than stoichiometrically.

A pyrolysis reactor comprising a housing having at least one front-side inlet and at least one rear-side outlet and at least one catalyst arranged in the housing between inlet and outlet according to claim 19.