EP1991340A1

EP1991340A1 - Catalyst material for treating products produced during combustion and production method

Info

Publication number: EP1991340A1
Application number: EP07703615A
Authority: EP
Inventors: Joerg Jockel; Kristina Pokorna; Nelson Ewane Olong
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2006-02-27
Filing date: 2007-01-03
Publication date: 2008-11-19
Also published as: WO2007098969A1; DE102006009015A1; US20090170694A1

Abstract

The invention relates to catalyst material for treating products produced during combustion, which is formed for catalytic conversion of particles containing carbon. Said catalyst material is applied to a carrier and comprises Cer as a catalyst component. In order to prepare a catalyst material which improves the catalytic conversion of particles containing carbon, the catalyst components comprise, in addition to Cer, at least one additional catalyst component, whereby the quantity of Cer is at least 92 mol % in relation to the total amount of catalyst components. The invention also relates to a method for producing a catalyst material.

Description

description

title

Catalyst material for treatment of combustion

Products and manufacturing processes

State of the art

For the treatment of combustion products or combustion exhaust gases, which are used, for example, in industrial processes or in the motor combustion of e.g. arise fossil fuels, catalyst devices are used. With catalyst devices both particulate and gaseous or liquid components or pollutants of the combustion products should be eliminated. For example, so-called diesel particulate filters are used in the exhaust gas treatment of exhaust gases which are produced during combustion of diesel fuel. With a diesel particulate filter in particular soot particles are filtered out of the exhaust stream and oxidized. In addition, exhaust gas components such as unburned hydrocarbons (HC) and carbon monoxide (CO) should be reacted with oxygen. Ideally, said exhaust gas ingredients are oxidized to carbon dioxide and water.

In particular, for a complete degradation of soot particles specific requirements are placed on the exhaust particulate filter. In the exhaust particulate filter catalytically active substances are used for the elimination of the exhaust gas ingredients. For example, catalytically active metals, e.g. Platinum, palladium or possibly vanadium or iron used.

Object of the invention

The object of the invention is to provide a catalyst material for the treatment of products resulting from combustion, with which the catalytic conversion of carbonaceous particles can be improved. This object is achieved by the claim 1 and the claim 10.

By the dependent claims advantageous variants of the invention are shown.

Disclosure of the invention

The invention is based on a catalyst material for the treatment of products resulting from combustion, which is designed for a catalytic conversion of carbonaceous particles, wherein the catalyst material is applied to a carrier and the catalyst material comprises cerium as a catalyst component. An essential aspect of the invention is that the catalyst constituents in addition to cerium have at least one further catalyst component, wherein based on the total amount of the catalyst components, the proportion of cerium is at least 92 mol percent. By this measure, the catalytic conversion of carbonaceous particles of the combustion products can be realized particularly effectively. It has been shown that soot catalysis is significantly improved, in particular by comparatively high proportions of cerium in the catalyst constituents. In particular, it is achieved that the temperature at which carbonaceous particles are degraded or oxidized to a significant extent and possibly completely burned off, in particular the so-called Rußabbrandtemperatur is significantly reduced compared to other catalyst material compositions. In particular, effective reduction of soot particles can be made possible with the proposed catalyst material even when the temperatures of the catalyst material are lower than in continuous operation, which can occur regularly. In particular, the cold start behavior in exhaust particulate filters, for example in vehicles with diesel engines is thereby improved. In particular, this makes it possible to provide an effective measure for meeting statutory environmental protection requirements, for example for reducing particulate matter pollution by car exhaust gases. The statement of proportions of the catalyst components in mole percent refers to the catalytically active substances or not to any existing fillers or support materials in the catalytic layer, which show no or almost no catalytic action. In the context of the invention, the term "catalyst constituents" is to be understood as meaning, in particular, constituents which are catalytically active on the degradation of combustion products, in particular metals or semiconductors such as platinum, palladium, rhodium or one of the elements with the chemical abbreviations mentioned below.

The catalyst components usually applied to ceramic supports, such as alumina particles, may for example be in an alloy or in compounds having different structures, e.g. as a mixture of elements, in molecular form or as complex compounds.

In addition to e.g. the lowering of Rußabbrandtemperatur is also achieved with the proposed catalyst material, that the temperature peaks arising during Rußabbrand are relatively lower or can be damped. Thus, the support material on which the catalyst components are applied can be spared from heat-related damage by Rußabbrand.

Advantageously, based on the total amount of the catalyst components, the proportion of cerium is between 92 mol percent and 99.5 mol percent. In order to achieve a catalytically effective degradation effect, e.g. also for non-particulate combustion products such as, for example, HC or CO, in addition to the main constituent cerium, in particular at least one further catalyst constituent is provided. In particular, metals or semiconductors can be used, for example platinum, palladium, rhodium or compounds or mixtures with these substances.

In a preferred embodiment of the subject matter of the invention, the catalyst constituents comprise, in addition to cerium, just one further catalyst constituent and the proportion of cerium based on the total amount of the catalyst fraction. - A -

components between 95 mole percent and 99.5 mole percent. It has been found that with the stated comparatively high proportions of cerium and precisely one further catalyst constituent, the degradation performance of particulate combustion products can be carried out particularly advantageously. In particular, with cerium content in said range and a further catalyst material is a significant reduction in the burning temperature of carbonaceous particles such as carbon black and an effective oxidation of HC and CO possible.

Advantageously, exactly one more catalyst component is one of the chemical elements with the chemical abbreviation K, B, Cd, Cr, Dy, Er, Gd, Ho, Ca, La, Li, Lu, Mg, Mn, Nd, Pr, Sm. Se, Y, Zn, Sn, Eu, Sb, Cs, Ru, Ga, Ge, Hf, In, Cu, Na, Ag, Si, Tb, Yb, Zr, Bi, Mo, Nb, Rb, Sc, W, Sr, Ti, Te, Ba, Tm, Ta, Co and Ni are formed. By combining one of said chemical elements with cerium, the composition of the catalyst materials can be made in a variety of different configurations. Due to the different possible combinations with cerium, the catalyst material can be optimally adapted in each case to different applications, in particular in order to realize a high catalytic activity for each combustion products to be treated.

In a particularly preferred embodiment of the subject invention, the proportions of the catalyst components are determined according to one of the following element formulas Ag ₃ Ceg ₇ , Mn ₃ Ceg ₇ and KaCegz, wherein the subscript numbers in the formulas the mole percent of the above catalyst component based on the total amount of specify both catalyst components. As a result of the abovementioned combinations of the catalyst constituents silver, manganese and potassium, in each case with cerium, it was possible to determine a comparatively clear reduction in the burning-off temperature of carbon-containing particles or of the soot burn-off temperature. For example, comparative experiments based on a differential thermal analysis (DTA) were carried out in which the respective catalyst materials were mixed with carbon black and heated in room temperature to 800 ^° C. in synthetic air. The decrease of the soot mass as relative mass of the soot to the starting mass or the thereby prevailing Temperature recorded in the test room, put into relationship and displayed as a curve. For a comparative assessment of the catalytic activity of the particular composition of the catalyst constituents, in particular those temperatures were determined in which a mass loss of the carbon black used of 50% occurred. As a reference curve, the combustion of pure soot without catalytic support was measured.

In an advantageous embodiment of the catalyst material, the catalyst constituents comprise, in addition to cerium, exactly two further catalyst components and the proportion of cerium based on the total amount of the catalyst constituents is between 92 mol percent and 99.4 mol percent. Inner content of the specified proportion of cerium in three catalyst components has a particularly effective reduction in the burning temperature of carbonaceous particles result in at the same time relatively high oxidation efficiency of the catalyst material to gaseous combustion products.

In the aforementioned embodiment of the invention, it is particularly advantageous if a catalyst component is formed by platinum, with a proportion based on the total amount of the catalyst components between 0.1 mol percent and 3.0 mol percent. This makes it possible to reliably realize catalytically assisted combustion of gaseous hydrocarbons (HC) and carbon monoxide (CO). In this case, comparatively small amounts of platinum based on the total amount of catalyst components are sufficient.

It is particularly advantageous if in addition to cerium and platinum, a third catalyst component is provided with a proportion based on the total amount of catalyst components between 0.5 mol percent and 5.0 mol percent. With the three catalyst components listed, the degradation efficiency of the catalyst material and the effectiveness with regard to particulate and gaseous combustion products can be effectively accomplished.

It is particularly preferred if the third catalyst component is replaced by one of the chemical elements with the chemical abbreviation K, B, Cd, Cr, Dy, Er, Gd, Ho, Ca, La, Li, Lu, Mg, Mn, Nd, Pr, Sm, Se, Y, Zn, Sn, Eu, Sb, Cs, Ru, Ga, Ge, Hf, In, Cu, Na, Ag, Si, Tb, Yb, Zr, Bi, Mo, Nb, Rb, Sc, W, Sr, Ti, Te, Ba, Tm, Ta, Co and Ni.

In a particularly preferred embodiment of the subject invention with cerium and exactly two other catalyst components are the proportions of the catalyst components according to one of the following element formulas Pto _{, 5} La ₃ Ceg _6.5 , Pto _{, 5} Al ₃ Ceg _6.5 and Pto _{, 5} K ₃ Ceg _6.5 , wherein the subscript numbers in the formulas indicate the mole percent of the foregoing catalyst component based on the total amount of the three catalyst components. With the abovementioned proportions of cerium, platinum and a further constituent, a significant reduction in the burning-off temperature of soot particles can be achieved, which could be confirmed experimentally, for example by combustion tests with the stated proportions of the catalyst constituents.

According to a further essential aspect of the invention, a method for producing a catalyst material on a support is proposed, in particular for one of the abovementioned catalyst materials, which is characterized in that a sol-gel process is used to form the catalyst constituents on the support. With a so-called sol-gel process (SGP), metals can be incorporated, for example, as complexes homogeneously distributed in oxide materials. A doping by the catalytically active component can be carried out in any amount. For example, by thermolytic decomposition of the metal complexes or by treatment in an oxygen plasma, highly dispersed metal oxide or metal particles can be produced, which can be used inter alia as heterogeneous catalyst materials. They are characterized by very small, homogeneously distributed and non-agglomerated particles, narrow particle size distribution and a very variable degree of loading. In particular, it is possible to use soluble organometallic compounds, for example alkoxides, alcoholates or propionates, which form a gel, for example by means of a condensation step with dehydration. One advantage of the sol-gel process is that, for example, it is possible to produce good ceramic or metal-oxide coatings with which, for example, ceramic fibers, particles coated or ceramic carrier. If an alcoholic solution of hydrolyzable alcoholates of polyvalent metal ions, for example titanium, cobalt, manganese, molybdenum, silicon, aluminum, etc., is applied to a surface, a metal hydroxide is formed in the presence of moisture already during the evaporation of the solvent at these temperatures. Network off. This contains numerous metal hydroxide (MOH) groups and is therefore hydrophilic and antistatic. As the temperature is raised, the MOH groups then undergo dehydration to form metal oxide moieties and the surfaces become very mechanically stable.

In an alternative method, a representation can be made starting from metal salt solutions of nitrates, acetates, citrates or carbonates. The solutions are dried and then calcined to temperatures of about 400 to about 800 ⁰ C, the corresponding anions are thermally decomposed and formed the corresponding metal oxides.

figure description

The invention will be explained in more detail with reference to the single figure shown in the drawing.

FIG. 1 shows graphs obtained by combustion experiments, one of which shows the combustion of soot without catalyst material and the other shows the combustion of soot, in each case mixed with another catalyst material of different composition. The experiments were carried out by means of a differential thermal analysis.

The different curves shown in Figure 1 are shown in a rectangular coordinate system, wherein measured on the abscissa axis in the test room temperature T in degrees Celsius to 800 ⁰ C and on the ordinate axis the relative weight m of the investigated amount of soot relative to the beginning of the experiment existing Ausgangsrußmenge is plotted. For the catalytically assisted combustion tests, the respective form of the catalyst materials mixed with carbon black in a ratio of carbon black to catalyst material of 1 to 4 and heated in synthetic air with 20% oxygen and 80% nitrogen from room temperature to about 800 ⁰ C. The heating rate was 10 Kelvin per minute. The volume flow of the synthetic air was set at 50 milliliters per minute.

In order to assess the catalytic effect of the different catalyst constituents, those temperatures were determined in addition to the entire course of the curve until complete combustion of the carbon black, in which a mass loss of the carbon black compared to the starting soot amount of 50% was determined. In the graph according to FIG. 1, these reference temperatures T50 in ⁰ C are to be determined by the intersection points of the individual measuring curves with the ordinate value of m = 0.5. In FIG. 1, curve 1 relates to the combustion test of pure soot, the further curves relate to the soot combustion with the catalyst material Ag ₃ Ce ₉₇ (curve 2), Pto, 5 La ₃ Ce ₉ 6.5 (curve 3), Pt _O , 5AI ₃ Ce ₆ 9.5 (curve 4), Mn ₃ Ce ₉₇ (Kur ^¬ ve 5) PtiK ₃ Ce ₉₆ (curve 6) and K ₃ ₉₇ Ce (curve 7).

Table 1 below shows the measured temperatures T50 in ⁰ C for pure carbon black or the individual investigated mixtures of carbon black with the various catalyst materials mentioned. The particular type of compound of the catalyst materials is also given in the table. The highest reference temperature T50 of 600 ^° C., measured in the tests, was measured for pure carbon black. The most significant lowering of the reference temperature T50 of 411 ⁰ C was ₃ ₇ Ceg measured for the catalyst material K.

Table 1:

Claims

claims

A catalyst material for the treatment of products formed by combustion, which is designed for a catalytic conversion of carbonaceous particles, wherein the catalyst material is supported and the catalyst material comprises cerium as a catalyst component, characterized in that the catalyst components in addition to cerium at least one have further catalyst component, wherein based on the total amount of the catalyst components, the proportion of cerium is at least 92 mol percent.

2. Catalyst material according to claim 1, characterized in that based on the total amount of the catalyst components, the proportion of cerium is between 92 mol percent and 99.5 mol percent.

3. Catalyst material according to one of the preceding claims, characterized in that the catalyst constituents in addition to cerium comprise exactly one further catalyst component and the proportion of cerium based on the total amount of catalyst components is between 95 mol percent and 99.5 mol percent.

4. Catalyst material according to claim 3, characterized in that the one further catalyst component by one of the chemical elements with the chemical abbreviation K, B, Cd, Cr, Dy, Er, Gd, Ho, Ca, La, Li, Lu, Mg, Mn, Nd, Pr, Sm, Se, Y, Zn, Sn, Eu, Sb, Cs, Ru, Ga, Ge, Hf, In, Cu, Na, Ag, Si, Tb, Yb, Zr, Bi, Mo, Nb, Rb, Sc, W, Sr, Ti, Te, Ba, Tm, Ta, Co and Ni.

5. Catalyst material according to one of claims 3 and 4, characterized in that the proportions of the catalyst components are determined in accordance with one of the following E lementformeln Ag ₃ Ceg ₇ , MnaCegz and KaCegz, wherein the subscript numbers in the formulas the mole percent of the preceding Catalyst component based on the total amount of the two catalyst constituents specify parts.

6. Catalyst material according to claim 1 or 2, characterized in that the catalyst constituents in addition to cerium comprise exactly two further catalyst components and the proportion of cerium based on the total amount of catalyst components is between 92 mol percent and 99.4 mol percent.

7. Catalyst material according to claim 6, characterized in that a catalyst component is formed by platinum, with a proportion based on the total amount of catalyst components between 0.1 mol percent and

3.0 mole percent.

8. Catalyst material according to claim 6 or 7, characterized in that in addition to cerium and platinum, a third catalyst component is provided with a proportion based on the total amount of the catalyst components between 0.5 mol percent and 5.0 mol percent.

9. Catalyst material according to one of claims 6 to 8, characterized in that the third catalyst component by one of the chemical elements with the chemical abbreviation K, B, Cd, Cr, Dy, Er, Gd, Ho, Ca, La, Li, Lu , Mg, Mn, Nd, Pr, Sm, Se, Y, Zn, Sn, Eu, Sb, Cs, Ru, Ga, Ge, Hf, In, Cu, Na, Ag, Si, Tb, Yb, Zr, Bi , Mo, Nb, Rb, Sc, W, Sr, Ti, Te, Ba, Tm, Ta, Co and Ni.

10. A catalyst material according to any one of claims 6 to 9, characterized in that the proportions of the catalyst components according to one of the following ele- formulas Pto, ₅ La ₃ Ceg ₆ , ₅ , Pto, ₅ Al ₃ Ceg ₆ , ₅ and Pto, ₅ K. ₃ Ceg ₆ , _{5 are} determined, wherein the subscript numbers in the formulas indicate the mole percent of the above catalyst component based on the total amount of the three catalyst components.

11. A process for producing a catalyst material on a support, in particular a catalyst material according to one of claims 1 to 10, characterized in that a sol-gel process for forming the catalyst components is used on the support.