Diesel oxidation catalyst

Abstract

The present invention relates to a diesel oxidation catalyst comprising a carrier body having a length L extending between a first end face and a second end face, and material sections A and B of different composition arranged on the carrier body, wherein material section A comprises platinum and palladium applied to a cerium-titanium mixed oxide, and material section B comprises platinum and palladium applied to a carrier oxide B.

Description

Technical Field

[0001] The present invention relates to an oxidation catalyst for purifying the exhaust gas of a diesel engine.

Background Art

[0002] In addition to carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NO), x the oxygen content of the undiluted exhaust gas of a diesel engine is relatively high, up to 15% by volume. Furthermore, particulate emissions, which mainly consist of soot residues and in some cases organic agglomerates, are included, which are due to the incomplete combustion of a part of the fuel in the cylinder.

[0003] For the removal of particulate emissions, a diesel particulate filter is suitable regardless of the presence or absence of a catalytically active coating. Nitrogen oxides can be converted to nitrogen, for example, by selective catalytic reduction (SCR) with a so-called SCR catalyst. Carbon monoxide and hydrocarbons are oxidized and rendered harmless by a suitable oxidation catalyst.

[0004] Oxidation catalysts are widely described in the literature. These are, for example, so-called flow-through substrates made of ceramic or metallic materials, and noble metals such as platinum and palladium, which are essential catalytically active components, are supported on a high-surface-area, porous high-melting-point oxide, for example, on aluminum oxide. Pre-segmented oxidation catalysts having material segments of different compositions, with which the exhaust gas continuously comes into contact, in the direction of the exhaust gas flow, are also described.

[0005] ​For example, U.S. Patent Application Publication Nos. 2010 / 257843, 2011 / 099975, and International Publication No. 2012 / 079598 (A1) describe a compartmentalized oxidation catalyst containing platinum and palladium. International Publication No. 2011 / 057649 (A1) also describes oxidation catalysts, which can be used in layered and compartmentalized embodiments. In the case of the compartmentalized embodiment, the second compartment, i.e., the compartment with which the outflowing exhaust gas comes into direct contact, has a higher noble metal content than the upstream compartment with which the inflowing exhaust gas comes into direct contact. The oxidation catalyst according to International Publication No. 2011 / 057649 has a specific role of setting an optimal ratio of NO to NO2 for the SCR catalyst on the outflow side.

[0006] Further oxidation catalysts are disclosed in International Publication Nos. 2010 / 133309 (A1), 2013 / 050784 (A2), U.S. Patent Application Publication No. 2008 / 045405, International Publication Nos. 2012 / 137930 (A1) and 2012 / 071421 (A2).

[0007] European Patent No. 2000639 (A1) describes an oxidation catalyst containing, in addition to platinum, an oxide of a metal selected from magnesium, alkaline earth metals and alkali metals. The function of the catalyst is to raise the exhaust gas temperature in the fuel injection. International Publication No. 2010 / 083355 (A2) discloses a diesel oxidation catalyst including a first washcoat layer containing a first refractory metal oxide support containing palladium and cerium, and a second washcoat layer containing a second refractory oxide support and a platinum component. The second washcoat layer contains substantially no palladium and contains a molecular sieve.

[0008] International Publication No. 2013 / 042080 (A1) discloses a layered diesel oxidation catalyst containing palladium impregnated in a carrier material containing ceria in an amount of at least 45% by weight in a first layer.

[0009] International Publication No. WO 2015 / 031611 (A1) discloses a CO slip catalyst comprising palladium and a ceria-containing material which can be, for example, ceria, ceria-zirconia, ceria-zirconia-alumina or a mixture thereof.

[0010] U.S. Patent Application Publication No. 2019 / 162095 relates to a diesel oxidation catalyst comprising a carrier body and three catalytically active zones A, B and C. Zone A contains palladium or platinum and rhodium with a Pt:Pd weight ratio of ≤1, zone B contains cerium oxide and no platinum, and zone C contains platinum or platinum and palladium with a Pt:Pd weight ratio of ≥5.

[0011] U.S. Patent Application Publication No. 2016 / 339389 claims an oxidation catalyst comprising a carrier substrate and first and second washcoat layers. The first washcoat layer contains palladium supported by a first refractory metal oxide carrier containing cerium and optionally containing titania, and contains substantially no platinum in particular. The second washcoat layer contains a second refractory carrier and a platinum component, and contains substantially no palladium in particular.

[0012] Both Catalysis Today 126 (2007) 382 - 386 and Journal of Catalysis 233 (2005) 41 - 50 deal with low-temperature CO oxidation on Pd supported on CeO2-TiO2 composite oxides.

[0013] Environmental Science & Technology, vol. 46, no. 17, pages 9600 - 9605 discloses a Ce-Ti amorphous oxide for the selective catalytic reduction of NO with NH3. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0014] The exhaust gas temperatures of current and future diesel engines related to Euro 5, 6 and 6+ exhaust gas regulations are increasingly decreasing due to fuel savings aimed at reducing CO2 emissions. Under low exhaust gas temperatures, diesel oxidation catalysts with sufficient CO light-off are becoming even more important. At the same time, the catalyst must also oxidize hydrocarbons sufficiently. Since currently known diesel oxidation catalysts do not fully meet this condition, further development corresponding to this is required.

Means for Solving the Problems

[0015] Here, it has been found that the diesel oxidation catalysts described and defined below meet these conditions.

[0016] The present invention is a diesel oxidation catalyst including a carrier body having a length L extending between a first end face and a second end face, and material partitions A and B of different configurations arranged on the carrier body, Material partition A includes platinum and palladium applied to a cerium-titanium mixed oxide, Material partition B includes platinum and palladium applied to carrier oxide B, relating to a diesel oxidation catalyst.

[0017] Material partition A preferably includes platinum and palladium in a weight ratio of 3:1 to 1:50, for example, 2:1 to 1:20, or 1:1 to 1:10.

[0018] Material partition A can further include rhodium.

[0019] Material partition A preferably includes platinum, palladium and optionally rhodium in an amount of 0.18 to 3.53 g / L based on the volume of the carrier body.

[0020] In material section A, platinum, palladium and optionally rhodium are applied to the cerium-titanium mixed oxide. In the context of the present application, the term "cerium-titanium mixed oxide" excludes a physical mixture of cerium oxide and titanium oxide. Rather, the term refers to a solid solution having a uniform crystal lattice in which the individual metal oxides cannot be distinguished. Or, the term refers to an agglomerate containing cerium oxide and titanium oxide that does not have a uniform crystal lattice and in which the phases of the individual metal oxides can be distinguished.

[0021] Preferably, the cerium-titanium mixed oxide contains 20 to 98% by weight of cerium oxide and 80 to 2% by weight of titanium oxide. More preferably, the cerium-titanium mixed oxide contains 25 to 95% by weight of cerium oxide and 75 to 5% by weight of titanium oxide.

[0022] Normally, material section A contains the cerium-titanium mixed oxide in an amount of 20 to 140 g / L based on the volume of the carrier body.

[0023] Preferably, material section A does not contain barium and barium oxide.

[0024] Material section B preferably contains platinum and palladium in a weight ratio of 10:1 to 1:3, for example 5:1 to 1:1.

[0025] Material section B preferably contains platinum and palladium in an amount of 0.73 to 6.36 g / L based on the volume of the carrier body.

[0026] The carrier oxide B advantageously has a high melting point, i.e., its melting point is sufficiently higher than the temperature that occurs during the intended operation of the oxidation catalyst according to the present invention. The carrier oxide B also advantageously has a large surface area, preferably having a specific surface area of 50 to 200 m 2 / g.

[0027] The carrier oxide B is selected in particular from the group consisting of aluminum oxide, doped aluminum oxide, silicon oxide, titanium dioxide, zirconium dioxide, and mixed oxides of one or more of these.

[0028] The doped aluminum oxide is, for example, aluminum oxide doped with silicon oxide, zirconium dioxide and / or titanium dioxide. Aluminum oxide doped with lanthanum is preferably used, and lanthanum is calculated as La2O3 respectively and used in an amount of 1 to 10% by weight, preferably 3 to 6% by weight, based on the weight of the stabilized aluminum oxide.

[0029] Preferably, the carrier oxide B is aluminum oxide or aluminum oxide stabilized with lanthanum.

[0030] Normally, the material section B contains the carrier oxide B in an amount of 10 to 160 g / L based on the volume of the carrier body.

[0031] In one embodiment of the oxidation catalyst according to the present invention, the material section B contains lanthanum oxide, magnesium oxide, barium oxide and / or strontium oxide, in particular in an amount of 0.5 to 8 g / L based on the volume of the carrier body. Lanthanum oxide is preferred.

[0032] In another embodiment of the oxidation catalyst according to the present invention, the material section B contains a hydrocarbon adsorbent material exemplified by zeolite. Preferably, the hydrogen adsorbent material is beta zeolite.

[0033] In yet another embodiment of the oxidation catalyst according to the present invention, the carrier body is different from the material sections A and B and includes a material section C containing platinum, palladium, or platinum and palladium applied to the carrier oxide C.

[0034] Preferably, the material section C contains platinum, or platinum and palladium, at a weight ratio of ≧1, for example, 20:1 to 10:1.

[0035] The material section C preferably contains platinum, palladium, or a combination of platinum and palladium in an amount of 1.06 to 7.06 g / L based on the volume of the carrier body.

[0036] The carrier oxide C advantageously has a high melting point, i.e., its melting point is sufficiently higher than the temperature that occurs during the intended operation of the oxidation catalyst according to the present invention. The carrier oxide C also advantageously has a large surface area, preferably having a specific surface area of 50 to 200 m 2 / g.

[0037] The carrier oxide C is particularly selected from the group consisting of aluminum oxide, doped aluminum oxide, silicon oxide, zirconium oxide, titanium dioxide, and mixed oxides of one or more thereof.

[0038] The doped aluminum oxide is, for example, aluminum oxide doped with silicon oxide, zirconium oxide, and / or titanium dioxide. Aluminum oxide stabilized with lanthanum is preferably used, and lanthanum is calculated as La2O3 and used in an amount of 1 to 10 wt%, preferably 3 to 6 wt%, based on the weight of the stabilized aluminum oxide.

[0039] Preferably, the carrier oxide C is aluminum oxide doped with silica in a total amount of 1 to 20 wt% based on the weight of the carrier oxide C.

[0040] Normally, the material section C contains the carrier oxide C in an amount of 30 to 180 g / L based on the volume of the carrier body.

[0041] In a particularly preferred embodiment, the present invention provides a diesel oxidation catalyst comprising a carrier body having a length L extending between a first end face and a second end face, and material sections A, B, and C of different configurations arranged on the carrier body, The material section A contains platinum and palladium applied to a cerium-titanium mixed oxide containing 25 to 95 wt% of cerium oxide and 75 to 5 wt% of titanium oxide in a weight ratio of 1:1 to 1:10, Material section B contains platinum and palladium applied to aluminum oxide or aluminum oxide stabilized with lanthanum in a weight ratio of 5:1 to 1:1, Material section C relates to a diesel oxidation catalyst comprising platinum and / or palladium applied to aluminum oxide doped with 1 to 20% by weight of silica, based on the doped aluminum oxide.

[0042] The carrier body is in particular a so-called honeycomb body made of ceramic, preferably cordierite, or metal. So-called flow-through honeycomb bodies are preferably used. However, embodiments using wall-flow filters as the carrier body are also envisaged.

[0043] As can be seen with reference to FIG. 1, material sections A and B, and, if present, material section C, can be arranged on the carrier body in different arrangements.

[0044] In the first arrangement, the oxidation catalyst of the present invention includes material sections A and B both extending over the entire length L of the carrier body, and material section B is located below material section A.

[0045] In the second arrangement, the oxidation catalyst of the present invention includes material sections A and B both extending over the entire length L of the carrier body, and material section A is located below material section B.

[0046] In the third arrangement, the oxidation catalyst of the present invention includes material sections A and B, where material section A extends starting from the first end face over 20 to 80% of the length L, and material section B extends starting from the second end face over 20 to 80% of the length L. In a preferred embodiment of the third arrangement, both material sections A and B extend over 40 to 60%, more preferably 50%, of the length L.

[0047] In the fourth arrangement, the oxidation catalyst of the present invention includes material sections A, B, and C. Both material sections A and B extend starting from the first end face over 40 - 60% of the length L. Material section A is located below material section B. Material section C extends from the second end face over 40 - 60% of the length L, where L = L A +L C and L A is the length of material section A, and L C is the length of material section C. Material section B has the same length as material section A.

[0048] In the fifth arrangement, the oxidation catalyst of the present invention includes material sections A, B, and C. Both material sections A and B extend starting from the first end face over 40 - 60% of the length L. Material section B is located below material section A. Material section C extends from the second end face over 40 - 60% of the length L, where L = L A +L C and L A is the length of material section A, and L C is the length of material section C. Material section B has the same length as material section A.

[0049] In the sixth arrangement, the oxidation catalyst of the present invention includes material sections A, B, and C. Material section A extends starting from the first end face over 40 - 60% of the length L. Material section C extends starting from the second end face over 40 - 60% of the length L. Material section B extends over the entire length L and is located below material sections A and C, where L = L A +L C and L A is the length of material section A, and L C is the length of material section C.

[0050] In the seventh arrangement, the oxidation catalyst of the present invention includes material sections A, B, and C. Material section B extends starting from the first end face over 40 - 60% of the length L. Material section C extends starting from the second end face over 40 - 60% of the length L. Material section A extends over the entire length L and is located below material sections B and C, where L = LB +L C and L B is the length of the material section B, and L C is the length of the material section C.

[0051] In the eighth arrangement, the oxidation catalyst of the present invention includes material sections A, B, and C. Both material sections B and C extend starting from the second end face over 40% to 60% of the length L. The material section B is located below the material section C. The material section A extends starting from the first end face over 40% to 60% of the length L. L = L A +L C and L A is the length of the material section A, and L C is the length of the material section C, and the material section B has the same length as the material section C.

[0052] In the ninth arrangement, the oxidation catalyst of the present invention includes material sections A, B, and C. Both material sections A and C extend starting from the second end face over 40% to 60% of the length L. The material section A is located below the material section C. The material section B extends starting from the first end face over 40% to 60% of the length L. L = L B +L C and L B is the length of the material section B, and L C is the length of the material section C, and the material section A has the same length as the material section C.

[0053] The oxidation catalyst of the present invention may be produced by coating a suitable carrier body by a method known per se with a coating suspension, a so-called wash coat. For example, to produce a coating suspension for each of the material sections A, B, and C, a selected carrier oxide is suspended in water. Then, platinum and / or palladium and / or rhodium are added to the suspension in the form of a suitable water-soluble precursor compound, such as palladium nitrate or hexahydroxyplatinate, while stirring, and are fixed on the carrier material, optionally by setting the pH and / or by adding auxiliary reagents.

[0054] Alternatively, the noble metal may also be applied to the carrier material in a manner similar to the method described in European Patent Application Publication No. 1101528 (A2).

[0055] The suspension thus obtained is then ground and applied to the carrier body by one of the standard coating methods. After each coating step, the coated part is dried with a hot air stream and, optionally, fired.

[0056] The aforementioned precursors and auxiliary reagents are known to those skilled in the art.

[0057] The diesel oxidation catalyst of the present invention is suitable for purifying the exhaust gas of a diesel engine, particularly with respect to carbon monoxide and hydrocarbons.

[0058] Accordingly, the present invention also relates to a method for treating diesel exhaust gas, which is characterized in that the diesel exhaust gas is passed through a diesel oxidation catalyst as described and defined above, and the diesel exhaust gas flows into the carrier body at a first end face and out of the carrier body at a second end face.

[0059] The diesel oxidation catalyst of the present invention is particularly used as a component of an exhaust gas purification system. In addition to the diesel oxidation catalyst of the present invention, the corresponding exhaust gas purification system includes, for example, a diesel particulate filter and / or a catalyst for selective catalytic reduction of nitrogen oxides, and the diesel particulate filter and the SCR catalyst are usually arranged downstream of the diesel oxidation catalyst of the present invention, which is on the outflow side. In one embodiment of the emission control system, the SCR catalyst is arranged on the diesel particulate filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0060]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0061] Example 1 a) 60 g / L of a ground CeTiOx material (CeO2 / TiO2 = 95 / 5) was added to a solution of a soluble Pt salt (0.35315 g / L of Pt), followed by the addition of 1.05944 g / L of Pd as a nitrate. Finally, 4.5 g / L of an alumina sol was added. The resulting product was dried and calcined at 550 °C for 2 hours.

[0062] b) A commercially available circular flow-through substrate of cordierite having a cell density of 62 cpcm (400 cpsi) and a wall thickness of 102 μm (4.0 mils) and dimensions of 14.4 cm × 7.6 cm (5.66 inches × 3.00 inches) was coated over its entire length with a washcoat containing 66 g / L of the product obtained according to a) above.

[0063] c) To 66.165 g / L of a ground powder containing 2.5897 g / L of Pt and 1.2949 g / L of Pd fixed to 100 g / L of alumina, 3.18 g / L of La2O3 and 25.48 g / L of beta zeolite were added. The powder was calcined at 550 °C for 2 hours.

[0064] d) The coated substrate obtained according to b) above was coated over its entire length with a washcoat containing 94 g / L of the product obtained according to c) above.

[0065] The resulting oxidation catalyst corresponds to Arrangement 2 above and is hereinafter referred to as C1.

[0066] Comparative Example 1 In step a), steps a) and b) of Example 1 were repeated except that 100 g / L of a ground CeTiOx material (CeO2 / TiO2 = 95 / 5) was added to a solution of a soluble Pt salt (0.9712 g / L of Pt), followed by the addition of 2.9135 g / L of Pd as a nitrate.

[0067] The obtained oxidation catalyst is hereinafter referred to as CC1.

[0068] Comparative Example 2 a) To 103.88 g / L of a pulverized powder containing 2.5897 g / L of Pt and 1.2949 g / L of Pd fixed on 100 g / L of alumina, 5 g / L of La2O3 and 40 g / L of beta zeolite were added. The powder was calcined at 550 °C for 2 hours.

[0069] b) A commercially available circular flow-through cordierite substrate having a cell density of 62 cpcm (400 cpsi) and a wall thickness of 102 μm (4.0 mils) and dimensions of 14.4 cm × 7.6 cm (5.66 inches × 3.00 inches) was coated over its entire length with a washcoat containing 148 g / L of the product obtained according to a) above.

[0070] The obtained oxidation catalyst is hereinafter referred to as CC2.

[0071] Example 2 a) 42 g / L of a pulverized CeTiOx material (CeO2 / TiO2 = 95 / 5) was added to a solution of a soluble Pt salt (1.059 g / L of Pt), followed by the addition of 1.059 g / L of Pd as a nitrate. Finally, 18 g / L of pulverized alumina was added, followed by 4.5 g / L of an alumina sol. The obtained product was dried and calcined at 550 °C for 2 hours.

[0072] b) A commercially available circular flow-through cordierite substrate having a cell density of 62 cpcm (400 cpsi) and a wall thickness of 102 μm (4.0 mils) and dimensions of 14.4 cm × 7.6 cm (5.66 inches × 3.00 inches) was coated over 50% of its length starting from its first end face with a washcoat containing 67 g / L of the product obtained according to a) above.

[0073] c) 50 g / L of pulverized alumina was added to a solution of Pt salt (0.942 g / L of Pt). Subsequently, 0.471 g / L of Pd as nitrate, 3 g / L of La2O3, 30 g / L of beta zeolite and 4.5 g / L of alumina - sol were added. The resulting product was dried and calcined at 550 °C for 2 hours.

[0074] d) The coated substrate obtained according to b) above was coated with a washcoat containing 89 g / L of the product obtained according to c) above, starting from its first end face, over 50% of its length.

[0075] e) 150 g / L of alumina doped with 10 wt% silica was added to a solution containing 2.608 g / L of Pt and 0.217 g / L of Pd (both in the form of nitrates). The resulting product was dried and calcined at 550 °C for 2 hours.

[0076] f) The coated substrate obtained according to d) above was coated with a washcoat containing 150 g / L of the product obtained according to e) above, starting from its second end face, over 50% of its length.

[0077] The obtained oxidation catalyst corresponds to the above - mentioned arrangement 4 and is hereinafter referred to as C2.

[0078] Example 3 The above Example 2 was repeated except that the substrate was first coated with a washcoat containing the product obtained according to step c) of Example 2, and subsequently coated with a washcoat containing the product obtained according to step a) of Example 2).

[0079] The obtained oxidation catalyst corresponds to the above - mentioned arrangement 5 and is hereinafter referred to as C3.

[0080] Example 4 a) A commercially available circular flow-through cordierite substrate having a cell density of 62 cpcm (400 cpsi) and a wall thickness of 102 μm (4.0 mils) with dimensions of 14.4 cm × 7.6 cm (5.66 inches × 3.00 inches) was coated over its entire length with a washcoat containing 89 g / L of the product obtained according to step c) of Example 2.

[0081] b) The coated substrate obtained according to a) above was coated over 50% of its length starting from its first end face with a washcoat containing 67 g / L of the product obtained according to step a) of Example 2.

[0082] c) 100 g / L of alumina doped with 10 wt% silica was added to a solution containing 1.304 g / L of Pt and 0.109 g / L of Pd (both in the form of nitrates). The resulting product was dried and calcined at 550 °C for 2 hours.

[0083] d) The coated substrate obtained according to b) above was coated over 50% of its length starting from its second end face with a washcoat containing 102 g / L of the product obtained according to c) above.

[0084] The resulting oxidation catalyst corresponds to Arrangement 6 above and is hereinafter referred to as C4.

[0085] Example 5 a) 84 g / L of a pulverized CeTiOx material (CeO2 / TiO2 = 95 / 5) was added to a solution of a soluble Pt salt (1.413 g / L of Pt), followed by the addition of 1.413 g / L of Pd as a nitrate. Finally, 36 g / L of pulverized alumina was added, followed by 9 g / L of an alumina sol. The resulting product was dried and calcined at 550 °C for 2 hours.

[0086] b) A commercially available circular flow-through cordierite substrate with a cell density of 62 cpcm (400 cpsi) and a wall thickness of 102 μm (4.0 mils) having dimensions of 14.4 cm × 7.6 cm (5.66 inches × 3.00 inches) was coated with a washcoat containing 134 g / L of the product obtained according to a) above, starting from its first end face, over 50% of its length.

[0087] c) The coated substrate obtained according to b) above was coated with a washcoat containing 66.8 g / L of the product obtained according to step c) of Example 2, starting from its second end face, over 50% of its length.

[0088] d) 100 g / L of alumina doped with 10 wt% silica was added to a solution containing 2.282 g / L of Pt and 0.109 g / L of Pd (both in the form of nitrates). The resulting product was dried and calcined at 550 °C for 2 hours.

[0089] e) The coated substrate obtained according to c) above was coated with a washcoat containing 102 g / L of the product obtained according to d) above, starting from its second end face, over 50% of its length.

[0090] The resulting oxidation catalyst corresponds to Arrangement 8 above and is hereinafter referred to as C5.

[0091] Example 6 a) 84 g / L of a pulverized CeTiOx material (CeO2 / TiO2 = 95 / 5) was added to a solution of a soluble Pt salt (1.413 g / L of Pt), followed by the addition of 1.413 g / L of Pd as a nitrate. Finally, 36 g / L of alumina and 9 g / L of alumina - sol were added. The resulting product was dried and calcined at 550 °C for 2 hours.

[0092] b) A commercially available circular flow-through cordierite substrate having a cell density of 62 cpcm (400 cpsi) and a wall thickness of 102 μm (4.0 mils) with dimensions of 14.4 cm × 7.6 cm (5.66 inches × 3.00 inches) was coated over its entire length with a washcoat containing 66 g / L of the product obtained according to a) above.

[0093] c) The coated substrate obtained according to b) above was coated over 50% of its length, starting from its first end face, with a washcoat containing 66.8 g / L of the product obtained according to step c) of Example 2.

[0094] d) The coated substrate obtained according to c) above was coated over 50% of its length, starting from its second end face, with a washcoat containing 102 g / L of the product obtained according to step d) of Example 5.

[0095] The obtained oxidation catalyst corresponds to the above Arrangement 7 and is hereinafter referred to as C6.

[0096] Comparative Experiment a) Cores were taken out from catalysts C1 - C6, CC1, and CC2. All the cores were aged at 800 °C for 16 hours in a hydrothermal atmosphere.

[0097] b) The T 50 CO- and T 50 C3H6 - light-off values were measured on a synthetic gas bench using the gas mixture shown in Table 1. Before the test, the catalysts were pre-conditioned at 650 °C in the same gas atmosphere.

[0098]

Table 1

[0099] c) The results obtained are shown in Figure 2.

[0100] Additional Experiments A. The catalysts C7 - C10 were produced by washcoating a normal commercially available flow-through substrate by means of normal coating techniques. All the catalysts contained 110 g / ft 3 of platinum and / or palladium on alumina, and the washcoat loading was 110 g / L in each case. The catalysts differed as follows: C7 contained only platinum. C8 contained platinum and palladium in a Pt:Pd weight ratio of 2:1. C9 contained platinum and palladium in a Pt:Pd weight ratio of 1:3. C10 contained only palladium. Platinum was applied as a solution of soluble Pt salt and palladium as nitrate.

[0101] B. The catalysts C11 - C14 were produced by washcoating a normal commercially available flow-through substrate by means of normal coating techniques. All the catalysts contained 110 g / ft 3 of platinum and / or palladium on ceria, and the washcoat loading was 110 g / L in each case. In addition, each washcoat contained 7 g / L of Alusol. The catalysts differed as follows: C11 contained only platinum. C12 contained platinum and palladium in a Pt:Pd weight ratio of 2:1. C13 contained platinum and palladium in a Pt:Pd weight ratio of 1:3. C14 contained only palladium. Platinum was applied as a solution of soluble Pt salt and palladium as nitrate.

[0102] C. Under the conditions immediately after production and after aging (in a hot water atmosphere at 800 °C for 16 hours), the T of the catalysts C7 - C14 50The co-write-off value was measured on a synthesis gas bench using the gas mixture shown in Table 2. Before the test, the catalyst was pre-conditioned at 500 °C in the same gas atmosphere.

[0103]

Table 2

[0104] The results are shown in Table 3.

[0105]

Table 3

Claims

1. A diesel oxidation catalyst comprising a carrier body having a length L extending between a first end face and a second end face, and material sections A and B of different configurations arranged on the carrier body, wherein the material section A contains platinum and palladium applied to a cerium-titanium mixed oxide, and the material section B contains platinum and palladium applied to a carrier oxide B, the diesel oxidation catalyst.

2. The diesel oxidation catalyst according to claim 1, characterized in that the material section A contains platinum and palladium in a weight ratio of 3:1 to 1:

50.

3. The diesel oxidation catalyst according to claim 1 or 2, characterized in that the cerium-titanium mixed oxide contains 20 to 98% by weight of cerium oxide and 80 to 2% by weight of titanium oxide.

4. The diesel oxidation catalyst according to any one of claims 1 to 3, characterized in that the material section B contains platinum and palladium in a weight ratio of 10:1 to 1:

3.

5. The diesel oxidation catalyst according to any one of claims 1 to 4, characterized in that the carrier oxide B is selected from the group consisting of aluminum oxide, doped aluminum oxide, silicon oxide, titanium dioxide, zirconium oxide, and one or more mixed oxides thereof.

6. The diesel oxidation catalyst according to any one of claims 1 to 5, characterized in that the material section B contains lanthanum oxide, magnesium oxide, barium oxide, and / or strontium oxide.

7. The diesel oxidation catalyst according to any one of claims 1 to 6, characterized in that the material section B contains a hydrocarbon adsorbent material.

8. The diesel oxidation catalyst according to any one of claims 1 to 7, characterized in that the carrier body is different from the material sections A and B and includes a material section C containing platinum, palladium, or platinum and palladium applied to a carrier oxide C.

9. The diesel oxidation catalyst according to claim 8, characterized in that the material section C contains platinum or platinum and palladium in a weight ratio of ≥1.

10. The diesel oxidation catalyst according to claim 8 or 9, characterized in that the carrier oxide C is selected from the group consisting of aluminum oxide, doped aluminum oxide, silicon oxide, zirconium oxide, titanium dioxide, and one or more mixed oxides thereof.

11. The diesel oxidation catalyst includes a carrier body having a length L extending between a first end face and a second end face, and material sections A, B, and C of different configurations arranged on the carrier body. The material section A contains platinum and palladium in a weight ratio of 1:1 to 1:10, which are applied to a cerium-titanium mixed oxide containing 25 to 95% by weight of cerium oxide and 75 to 5% by weight of titanium oxide. The material section B contains platinum and palladium in a weight ratio of 5:1 to 1:1, which are applied to aluminum oxide or aluminum oxide stabilized with lanthanum. The material section C contains platinum and / or palladium applied to aluminum oxide doped with 1 to 20% by weight of silica based on doped aluminum oxide. The diesel oxidation catalyst according to any one of claims 1 to 10, characterized in that.

12. The diesel oxidation catalyst according to any one of claims 1 to 8, characterized in that both the material sections A and B extend over the entire length L of the carrier body, and the material section A is located below the material section B.

13. A method for treating diesel exhaust gas, characterized in that the diesel exhaust gas is passed through the diesel oxidation catalyst according to any one of claims 1 to 12, and the diesel exhaust gas flows into the carrier body at the first end face and out of the carrier body at the second end face.

14. An apparatus for purifying exhaust gas from a diesel engine having the diesel oxidation catalyst according to any one of claims 1 to 12.

15. The apparatus according to claim 14, characterized in that the diesel oxidation catalyst according to any one of claims 1 to 12 is arranged upstream of a diesel particulate filter and / or a catalyst for selective catalytic reduction of nitrogen oxides.

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