MXPA97002631A - Die catalyst - Google Patents

Abstract

The present invention relates to a catalyst for the purification of exhaust gases from diesel engines. The catalyst contains a mixture of zeolites of several zeolites with different modules and metals of the platinum group as well as other metal oxides of the aluminum silicate group, aluminum oxide and titanium oxide, where the aluminum silicate has a weight ratio of silicon dioxide / 0.005 to 1 aluminum oxide and the metals of the platinum group are only embedded on additional metal oxides

Description

DIESEL CATALYST DESCRIPTION OF THE INVENTION The present invention relates to a catalyst for exhaust gas purification of diesel engines, which contains one or more zeolites as well as at least one metal of the platinum group. Exhaust gas from diesel engines presents carbon monoxide, unburned hydrocarbons, nitrogen oxides and soot particles as harmful elements of the air. Unburned hydrocarbons include paraffins, defines, aldehydes and aromatics. Compared with the exhaust gases of naphtha engines, the exhaust gases of diesel engines have a noticeably higher proportion of long-chain paraffins, which are difficult to oxidize. Furthermore, the exhaust gases of diesel engines are notoriously colder than the exhaust gases of naphtha engines and contain oxygen at a concentration between 3 and 10% by volume. The high concentration of oxygen is based on the fact that diesel engines operate with an air / fuel ratio (kilograms of air / kilograms of fuel) of more than 18. On the other hand, naphtha engines work with an air / fuel ratio of 14.6, which allows a stoichiometric combustion of the hydrocarbons. Therefore, the exhaust gas from naphtha engines is practically free of oxygen. In partial load operation the exhaust gas temperature of a diesel engine ranges from 100 to 250 ° C and only in the operation of REF: 24507 Maximum load reaches a maximum temperature that ranges between 550 and 650 ° C. On the other hand, the temperature of the exhaust gas from a naphtha engine oscillates in partial load operation between 400 and 450 ° C and can reach a maximum temperature of 1000 ° C during maximum load operation. The soot particles of the exhaust gas of diesel engines are composed of carbon germs and volatile organic compounds adhered to them (VOC = volatile organic compounds) and adsorbed sulphates, which are formed during combustion in the diesel engine due to the sulfur content of diesel fuel. Due to the special properties of the diesel exhaust gas, tailor-made exhaust gas purification systems have been developed for its purification. DE 39 40 758 A1 describes a catalyst for the oxidative purification of exhaust gases of diesel engines with high conversion rates for hydrocarbons and carbon monoxide at low temperatures and under the effect of oxidation against nitrogen oxides and sulfur dioxide. The active component of the catalyst is composed of vanadium or platinum, paiadium, rhodium and / or iridium in contact with an oxidic vanadium compound. The active component is embedded on aluminum oxide, titanium oxide, silicon oxide, zeolite as well as their mixtures, of fine particles. The catalyst is applied in the form of a coating on the freely flowing channels of a ceramic or metal carrier body in the form of a honeycomb. Start-up temperatures T 50% of this catalyst for carbon monoxide and hydrocarbons range between 210 and 275 ° C (when speaking of T 50 or 50 ° drop-off temperatures, reference is made to exhaust gas temperatures, to which a catalyst is capable of transforming exactly 50% of harmful substances into non-hazardous components harmful). At 350 ° C the catalyst has good conversion rates for carbon monoxide and hydrocarbons. The catalyst passes nitrogen oxides almost without exerting any influence. Sulfur dioxide is oxidized only slightly to sulfur trioxide. Due to the effect of decreased oxidation against sulfur dioxide, this catalyst also leads to a lower emission of particles than in other oxidation catalysts, since in the exhaust gas there is less amount of sulphates, which can be adsorbed on the germs of soot. The problem of particle emission decreases as the planned introduction of low sulfur diesel fuels is imposed, in such a way that the catalyst of DE 39 40 758 A1 will be losing importance. European patent EP 0 427 970 A2 describes a catalyst for the reduction of nitrogen oxides in an oxidizing exhaust gas with an air / fuel ratio of 22. The catalyst contains at least one zeolite with a molar ratio SiO2 / AI2O3 of more than 10 and pore diameters from 0.5 to 1 nm. Metals from the platinum group are embedded on the zeolites; where for each metal of the die platinum group the minimum weight ratio of the metal to the zeolite can not fall below a certain value, if even after the aging of the catalyst it is desired to obtain good transformation rates for nitrogen oxides. DE 44 35 073 A1 describes a catalyst, which contains a mixture of at least two zeolites with different pore diameters as well as palladium-laden ce- roxide. The mixture of the zeolites serves for the adsorption of the hydrocarbon molecules of different size of the exhaust gas during the cold initiation phase. Palladium and cerium are used to convert hydrocarbons adsorbed on non-harmful components. The purpose of the present invention is to provide a catalyst for the purification of exhaust gases of diesel engines improved with respect to the state of the art which is capable of oxidizing especially the long-chain paraffins difficult to oxidize in the exhaust gas at temperatures per below 200 ° C and at the same time reduce nitrogen oxides despite the high oxygen content of the diesel exhaust gas. This task is solved by means of a catalyst for the purification of exhaust gases of diesel engines, which contains several zeolites as well as at least one metal of the platinum group. The catalyst is characterized in that it additionally contains one or more oxides of metals of the group aluminum silicate, aluminum oxide and titanium oxide, where the aluminum silicate has a weight ratio of silicon dioxide / aluminum oxide of 0.005 to 1 and the metals of the die platinum group are embedded only on these additional metal oxides. According to the invention, the catalyst contains, in addition to the zeolites, other metal oxides, which serve as carriers for the metals of the platinum group. It is essential that the platinum group metals are only embedded on these additional metal oxides and not on the zeolites. The incrustation of the platinum group metals on the zeolites leads to less active catalysts (see comparative example V?). The incrustation of the metals of the die platinum group on the oxides of additional metals (what will also be called activation of the metal oxides) can take place in a different way. It is important that the selected scale process guarantees a uniform and finely distributed scale of metals from the platinum group, if possible. oxides of additional metals. A possible incrustation process is the impregnation of the additional metal oxides before mixing with the zeolites with a solution of soluble previous states of the platinum group metals. Preferably, aqueous solutions are used for this. As preconditions for the metals of the platinum group, all salts and salts of complexes thereof which are useful are suitable. Examples of such compounds are hexachloroplatinic acid, tetrachloroplatinic acid, diamindinitroplatinum (II), tetraaminplatin (II) chloride, ammonium tetrachloride (II) platinate, ammonium hexavachlor (IV) platinate, platinethylene diamine dichloride, tetraaminplatin nitrate ( II), tetraaminplatinum (II) hydroxide, palladium chloride, palladium nitrate, diamindinitropalladium (II), tetraaminpalladium hydroxide (II) and hexachloroiridium acid. For the impregnation of the additional metal oxides, they are contacted with an aqueous solution of the palladium group metal (s) under constant agitation, so as to form a wet powder. In this case, the volume of the solvent is measured in such a way as to equal approximately 100 to 130, preferably 110%, of the water absorption capacity of the metal oxide powder to be impregnated. After drying for about 1 to 3 hours at an increased temperature of 80 to 140 ° C, the powder formed is calcined for 1 to 4 hours at a temperature between 200 and 500, preferably at 300 ° C, in air and then reduced in a gas stream containing hydrogen, preferably formation gas of 96 vol.%. of nitrogen and 5% in vol. of hydrogen. In this, temperatures ranging between 300 and 600, especially 500 ° C, are applied. The reduction ends after around from 1 to 3 hours. Studies carried out with an electron microscope show that the metals of the platinum group embedded in the specific surface of the metal oxides are finely distributed with particle sizes between 10 and 50 nm. With this procedure, additional metal oxides with a content of 0 can be covered, From 1 to 5% by weight of the metal of the platinum group with respect to the total weight of the impregnated metal oxides. To inhibit the oxidation of sulfur dioxide to sulfur trioxide, the additional metal oxides can be coated simultaneously with the metals of the platinum group or in any sequence with these with vanadium. In addition, other non-noble metals such as nickel and copper can be embedded to influence the catalytic activity exerted by the metals of the platinum group on the oxides of additional metals. For this, soluble precursor compounds of these metals are used. The additional metal oxides serve as the carrier material for the catalytically active platinum group metals. For this reason, metal oxides having a high specific surface area of more than 10 m2 / g are especially suitable. In the case of aluminum oxide, these are the so-called active aluminum oxides. They present the crystal structures of the transition series of the crystallographic phases of aluminum oxide, through which it passes, when aluminum oxides hydroxides are calcined, as for example. gibsite or bohemite, at more than 1000 ° C. In particular, it is chi, eta-, gamma-, kappa-, delta- and teta-aluminum oxide. Their specific surfaces can cover more than one hundred square meters per gram. These materials may be able to achieve the stabilization of their specific surface against high temperatures with, for example, rare earth oxides. Suitable materials are titanium oxide, which can be manufactured by wet chemical process (sulphate or chloride process) or by flame hydrolysis of titanium tetrachloride. Titanium oxides prepared by wet chemistry predominantly have the structure of anatasia and have a specific surface area of more than 50 m2 / g in general. The titanium oxides produced by flame hydrolysis have a mixed structure of approx. 70% anatase and 30% rutile. The specific surface of the so-called titanium oxides is around 50 m2 / g. Of the additional metal oxides, aluminum silicate is preferably used as the carrier material for the metals of the platinum group. This is a special aluminum silicate, which has a weight ratio of silicon dioxide / aluminum dioxide ranging between 0.005 and 1 and a very homogeneous distribution of aluminum oxide and silicon dioxide. The structure of the crystals of this aluminum silicate is, unlike that of the zeolite, bohemite and as the content of silicon oxide increases it becomes amorphous. The specific surface of this aluminum silicate varies depending on the silicon dioxide content between 200 and 500 m2 / g and has an excellent surface stability against the operating conditions during the purification of exhaust gases from diesel engines. Table 1 records these properties. In the upper half, it shows the specific surface area for different aluminum silicate compositions (BET surface according to Brunauer, Emmett and Teller according to DIN 66131) in fresh state and after forced aging (rest for 7 hours at 900 ° C) in a synthetic exhaust gas of 10 vol.% carbon dioxide, 6 vol.% oxygen, 10 vol.% water vapor, the remainder nitrogen). By means of the previously described impregnation of the aluminum silicate with the metals of the platinum group, it is obtained with a charge predetermined aluminum silicate (eg 1.5% by weight of Pt with respect to the total weight of aluminum silicate and platinum) a certain concentration of the metal particles per square meter of aluminum silicate surface area. The concentration of particles can be increased with the same load if the specific surface of the silicate is lowered. It has been shown that the starting temperatures of the catalyst for the conversion of carbon monoxide are positively influenced by an increase in the concentration of particles. To reduce the specific surface area while maintaining the composition of the aluminum silicate constant, it can be subjected to a calcination at 1000 ° C with different duration. In the lower half of Table 1, three materials treated in this way are indicated. By means of calcination, aluminum silicates of a given composition can then be produced with different specific surfaces. For the purposes of the present invention, materials with specific surfaces greater than 100 m2 / g are preferably applied. As a measure for the concentration of particles on the specific surface of the aluminum silicate, the last column of Table 1 indicates the concentration of platinum in mg of Pt per square meter of surface area (in the fresh state) in the case of a load of aluminum silicate with 1% by weight of platinum. It is recognized that a specific composition of the aluminum silicate (eg 95 AI2O3 / 5 SiO2) and pre-fixed platinum loading (eg 1% by weight) can influence the concentration of platinum on the specific surface and therefore on the concentration of particles by means of the variation of the specific surface. Table 1: Surface stability of aluminum silicate Content Content Relationship Surface mg of Pt of Al203 of SiO2 of specific weights 1 r mv, 2 [% by weight] [% by weight] Al203 / SiO2 [m2 / g] fresh aged. 98.5 1, 5 0.015 200 159 0.05 95 5 0.053 286 235 0.035 90 10 0.111 333 224 0.03 80 20 0.250 374 265 0.027 70 30 0.429 407 270 0.025 60 40 0.667 432 271 0.023 95 5 0.053 212 175 0.047 95 5 0.053 153 137 0.065 95 10 0.111 163 138 0.061 For the catalyst according to the invention, an aluminium silicate with a weight ratio between silicon dioxide / aluminum oxide of less than 0.5, especially less than 0.25, is preferably applied. These aluminum silicates can optionally contain homogeneously incorporated, oxide-forming elements stable at high temperatures. Suitable elements are eg. rare earths such as lanthanum and cer as well as zirconium and alkaline earth metals, which are introduced in the form of suitable precursor compounds. Preferred contents of these elements up to 10% by weight calculated as oxide. More unfavorable results were obtained with higher alkali metal contents such as eg. sodium. Very suitable aluminum silicates have a sodium content, calculated as oxide, of less than 75 ppm. The homogeneous distribution required between aluminum oxide and silicon oxide can not be obtained by usual process for the stabilization of aluminum oxide. Also physical mixtures of aluminum oxide and silicon dioxide are unsuitable for the catalyst according to the invention. An especially suitable aluminum silicate is described in DE 38 39 580 C1. According to this patent, aluminum silicate is obtained by mixing an aluminum compound with a silicic acid compound in an aqueous medium, drying and optionally calcination of the product. As the aluminum compound, a C2-C0 aluminum alcoholate is used which is hydrolyzed with purified water by means of an ion exchanger. 0.1 - 5.0% by weight of a solution of purified orthosilicic acid is added to the hydrolysis water by means of an ion exchanger. Alternatively, a clay / water mixture obtained by neutral hydrolysis can be added to a water mixture. 0.1-5.0% by weight orthosilicic acid purified by means of an ion exchanger. This especially suitable aluminum silicate can contain aggregates of lanthanum oxide or also other rare earth oxides. The zeolites to be used in the catalyst according to the invention must have a modulus greater than 10, in order to be stable enough against the acid components of the exhaust gas and at the maximum temperatures of the exhaust gas. Suitable zeolites are e.g. ZSM5, mordenite and Y-zeolite dealuminized (DA Y). They can be used in the Na * or in the H + form. The zeolites are can describe by means of the general formula M2 / n O Al203. x Si02. and H20 with x > 2 (Donald W. Breck: "Zeolithe Molecular Sieves", John Wiley &Sons, 1974). M describes in the formula a cation with the valence n as eg. H + (n = 1), Na + (n = 1) or Ca2 + (n = 2). x is the so-called modulus of the zeolite and indicates the molar ratio between silicon dioxide / aluminum dioxide. Taking into account Iso molar weights the zeolites therefore have a weight ratio between silicon dioxide / aluminum oxide of more than 1, 18. Preferably, for the catalysts according to the invention, zeolites with a modulus of more than 10, that is, with a weight ratio of silicon dioxide / aluminum oxide of more than 5.9, are used. Such a relationship guarantees sufficient stability of the characteristic crystal structure of the zeolites against the temperatures of the diesel exhaust gases and of the acidic harmful components contained therein. In a particularly advantageous embodiment of the invention, a mixture of zeolites of at least 2 zeolites is used, of which one has a modulus of less than 50 and the other has a modulus greater than 200. It has been observed that a spectrum if possible The wide range of the modules of the zeolites used has an advantageous effect on the conversion rates for the harmful substances. By means of a dealuminizing treatment it is possible, prepare zeolites of a structure type with a wide spectrum of modules. The module of a zeolite ZSM5 of stoichiometric composition has eg. a value of 5. By dealuminization, modulus values of up to more than 1000 can be adjusted. Y-zeolites and mordenite behave similarly. Table 2 is a list of the properties of some of the zeoiites that are adequate for the catalysts according to the invention. Table 2: Properties of some zeolites Zeolite Module Surface Diameter Specific volume of the pore pore [m2 / g] [nm] [mi / g] H-mordenite 20 565 0.4 • - 0.5 / 0.8 - 0.9 * 1, 76 H-ZSM5 40 360 0.5 - 0.6 2.09 H-ZSM5 120 415 0.5 - 0 , 6 0.6 DAY 200 755 0.74 1, 03 Na-ZSM5 > 1000 770 0.5 - 0.6 1, 61 *) bimodal pores Preferably, a mixture of the 5 zeolites indicated in the Table is applied to the catalyst according to the invention. However, the weight ratio of the zeolites to each other can vary within wide limits. Preferably, a mixture of equal parts by weight of all the zeolites is used. In a further advantageous embodiment of the invention, an aluminum silicate activated with platinum is combined with a zeolite mixture of a dealuminated Y-zeolite and a Na-ZSM5-zeolite, whose modules are greater than 120. Preferably the two are used. zeolites DAY and Na-ZSM5 of Table 2 with modules of 200 a > 1000. A particularly low starting temperature for the conversion of carbon monoxide is achieved if an aluminum silicate with a specific surface area between 100 and 200 m2 / g is used, which has a charge of platinum that ranges between 0.05 and 0.2 mg of Pt / m2. Especially suitable for this is an aluminum silicate with a SiO2 content of approx. 5% by weight and a specific surface area between 140 and 170 m2 / g. The low starting temperature of this catalyst is especially important for modern diesel direct injection engines, whose exhaust gas temperature in partial operation ranges between 100 and 150 ° C. In this temperature range a small decrease in the starting temperature means a marked improvement in the conversion of harmful substances. For the production of the catalyst according to the invention, the zeolite mixture is mixed with the additional catalytically activated metal oxides. Here we use ratios of metal oxide weights / zeolite mixture of 10: 1 to 1: 3, preferably of 6: 1 to 2: 1. The mixture of zeolite in the catalyst has the function above all of temporarily storing the hydrocarbons of exhaust gas at low starting temperatures, to re-release them under operating conditions of the diesel engine at higher exhaust gas temperatures. At these higher temperatures of the exhaust gas it is ible that the desorbed hydrocarbons of the catalytically activated additional metal oxides are partially oxidized into carbon monoxide and water. The non-oxidized components of the hydrocarbons also serve as carbon monoxide reducing agent for the catalytic reduction of the nitrogen oxides found in the exhaust gas. The optimum weight ratio of the additional metal oxides to the zeolite mixture depends on the average concentration of hydrocarbons in the exhaust gas and, therefore, also depends on the type of diesel engine. However, above a weight ratio of 10: 1 it is by no means ible to guarantee a sufficient storage of Iso hydrocarbons. Yes, in change, the weight ratio between the metal oxides / zeolite mixture decreases to less than 1: 3, then the catalytic activity of the catalyst is no longer sufficient, for direct or indirect injection diesel engines good results have been obtained with ratios of weights between 6: 1 and 2: 1. The resulting catalyst mixture can be further treated in the known manner to obtain shape bodies such as tablets and extruder products under the addition of suitable auxiliary agents such as inorganic binders (by ewj. silicasol), pore formers, plasticizers and wetting agents. However, preferably the catalyst is applied in the form of a coating on the inner walls of the honeycomb-shaped body stream channels. For the purification of exhaust gases from diesel engines, coating quantities of 50 to 400 g / l body volume in the form of honeycomb are required. The comtion of the catalyst should be adjusted in such a way that the active components on the additional metal oxides are present in a concentration of 0, 01 to 5 g / 1 volume of the honeycomb body. The necessary coating techniques are known to the person skilled in the art. Thus, for example, the mixture of the activated metal oxide catalyst and the zeolite mixture is treated until an aqueous coating dispersion is obtained. To this dispersion can be added eg. Silicasol as a binder. The viscosity of the dispersion can be adjusted by means of suitable auxiliary agents in such a way as to make it possible to apply on the walls of the current channels the amount of coating required in a single stage of work. When this is not possible, the coating can be repeated several times where the newly applied coating is fixed in each case by means of an intermediate drying. The finished coating is then dried at Increased temperature and calcined for 1 to 4 hours at temperatures between 300 and 600 ° C in the air. The invention will now be illustrated in greater detail on the basis of some examples and comparative examples of the state of the art. Comparative Example V1 In accordance with European patent EP 0 427 970 A2 a comparative catalyst was manufactured. For this, a coating dispersion with a solids content of 30% by weight was prepared. The dispersion contained 80% by weight of zeolite powder relative to the dry mass (H-mordenite, x = 25 and 20% by weight of silica-sol). A honeycomb body was then coated by immersion in the coating dispersion with the oxides and then dried in air at 100 ° C. After annealing at 300 ° C for 1.5 hours, the body was calcined for 3 hours at 500 ° C. The coated honeycomb body was then impregnated with an aqueous solution of tetraaminplatin (II) hydroxide, dried at 150 ° C and calcined at 250 ° C. The finished catalyst contained 120 g of oxide and 1.77 g of platinum per liter of volume of the honeycomb body. The honeycomb body of open cells consisted of cordierite with 2.5 cm diameter, 7.6 cm length, 62 cells or current channels per cm2 and a wall thickness of 0.2 mm current channels. Comparative Example V2 According to German Patent DE 39 758 A1, Example 18, a comparative catalyst was manufactured in the following manner. An aqueous coating dispersion with a solids content of 40% was prepared. The dispersion contained 60% by weight of aluminum oxide (180 m2 / g of surface area) and 40% by weight of titanium dioxide (50 m2 / g of surface area). A honeycomb body was then coated with the metal oxides by immersion in the coating dispersion and then dried in air at 120 ° C. After calcination at 400 ° C for 2 hours, the honeycomb body was impregnated with an aqueous solution of tetraaminplatin (II) hydroxide, dried at 150 ° C and calcined at 300 ° C. An impregnation with vanadium oxalate was then carried out. The drying was carried out at 120 ° C in the air, the decomposition of vanadium at 500 ° C in the air. The preliminary catalyst stage obtained in this way was reduced for 2 hours at 500 ° C in the formation gas stream (95% N2, 5% H2). The finished catalyst contained 64 g of titanium oxide, 96 g of aluminum oxide and 1.77 g of platinum per liter of honeycomb body volume. Comparative Example V3 Analogously to German patent DE 39 40 758 A1, a comparative catalyst was produced in the following manner. A coating dispersion with a solids content of 40% by weight was prepared. The dispersion contained 95% by weight of aluminum oxide (180 m2 / g of surface area) and 5% by weight of silicon dioxide (100 m2 / g of surface area). A honeycomb body was then coated with the metal oxides by immersion in the coating dispersion and then dried in the air at 120 ° C. After calcination at 400 ° C for 2 hours, the honeycomb body was impregnated with an aqueous solution of hexachloroplatinic acid, dried at 150 ° C and calcined at 300 ° C. The preliminary catalyst stage obtained in this way was reduced for 2 hours at 500 ° C in the formation gas stream (95% N2, 5% H2). The finished catalyst contained 200 g of oxide and 1.77 g of platinum per liter of volume of the honeycomb body. Comparative Example V4 Analogously to German patent DE 44 35 073 A1, example 3, a comparative catalyst was manufactured in the following manner. First it was impregnated cerium oxide with a specific surface area of 105 m2 / g with palladium. To do this, the cerium oxide was brought into contact with an aqueous solution of tetraaminpalladium (II) nitrate for constant stirring, in such a manner as to form a wet powder. After drying for two hours at 120 ° C in the air, the formed powder was calcined for 2 hours at 300 ° C in the air. The cerium-Pd oxide powder thus prepared contained, based on its total weight, 1.47% by weight of palladium. The prepared Pd / CeO2 powder was made an aqueous coating dispersion with a solids content of 40% by weight. To this were added the following zeolite powders in the ratio 1: 1: 1: 1: 1: DAY (x = 200); Na-ZSM5 (x> 1000); H-ZSM5 (x = 120); H-ZSM5 (x = 40); H-mordenite (x = 20). A honeycomb body was then coated with an amount of 180 oxides per liter of honeycomb body volume by immersion in the coating dispersion. The coating was dried in air at 120 ° C and finally calcined at 500 ° C for 2 hours. The finished catalyst contained 1.77 g of palladium per liter of honeycomb body volume. Example B1 For the catalyst according to the invention, an aluminum silicate was activated with 5% by weight of silicon dioxide (surface area of 286 m2 / g, see table 1) with platinum. For this, the aluminum silicate was brought into contact with an aqueous solution of tetraaminplatinum hydroxide (II) under constant stirring, in such a manner as to form a wet powder. After 2 two hours of drying at 120 ° C to air the dust formed was calcined for 2 hours at 300 ° C in the air. Subsequently, the reduction in the formation gas stream (95% by volume of N2 and 5% by volume H2) was carried out at 500 ° C for 2 hours. The aluminum silicate-Pt powder thus formed contained 1.47% by weight of platinum based on the total weight.

From the prepared aluminum Pt-silicate powder a dispersion was made aqueous coating with 40% solids content. To this was added the following zeolite powders in the ratio 1: 1: 1: 1: 1: DAY (x = 200); Na-ZSM5 (x> 1000); H-ZSM5 (x = 120); H-ZSM5 (x = 40); H-mordenite (x = 20). The exact composition of the coating dispersion is indicated in Table 3. Table 3: Composition of the coating dispersion Raw material Composition [% by weight] Pt - aluminum silicate 67 H-mordenite (x = 20) 6.6 H-ZSM5 (x = 40) 6.6 H-ZSM5 (x = 120) 6.6 DAY (x = 200) 6.6 Na-ZSM5 (x> 1000) 6.6 As a catalyst carrier, a honeycomb body with open cells, cordierite honeycomb with 2.5 cm diameter, 7.6 cm long, was used. 62 cells or current channels per cm2 and a wall thickness of the channels current 0.2 mm. This honeycomb body was coated by means of a dip in the coating dispersion with an amount of 180 oxides per liter of honeycomb body volume. The coating was dried in air at 120 ° C and then calcined at 500 ° C for 2 hours. The finished catalyst contained 1.77 g of platinum per liter of catalyst volume. The composition of this catalyst and of all the catalysts of the following examples is indicated in Table 4. Example B2 Another catalyst was prepared according to example 1. Instead of using a zeolite mixture only the DAY zeolite was applied (x = 200) in an amount of 33% by weight based on the total weight of the catalyst mixture. Example B3 Another catalyst was prepared according to Example 1. Instead of using a zeolite mixture, only Na-ZSM5 (x> 1000) was applied in an amount of 33% by weight based on the total weight of the catalyst mixture. . Example B4 Another catalyst was prepared according to Example 1. Instead of using a zeolite mixture only H-ZSM5 (x = 120) was applied in an amount of 33% by weight based on the total weight of the catalyst mixture. Example B5 Another catalyst was prepared according to example 1. Instead of using a zeolite mixture only H-ZSM5 (x = 40) was applied in an amount of 33% by weight based on the total weight of the catalyst mixture. Example B6 Another catalyst was prepared according to example 1. Instead a mixture of zeolite was used, only mordenite (x = 20) was applied in an amount of 33% in weight based on the total weight of the catalyst mixture. Example B7 Another catalyst was prepared according to example 5. Instead of using a single zeolite, a zeolite mixture of H-ZSM5 (x = 40) and H-ZSM5 (x = 120) was applied in a 1: 1 ratio. The amount of zeolite was 33% by weight based on the total weight of the catalyst mixture. Example B8 Another catalyst was prepared according to Example 5. Instead of using a single zeolite, a mixture of H-ZSM5 zeolite (x = 40, H-ZSM5 (x = 120) and Na-ZSM5 (x >) was applied. 1000) in a 1: 1 ratio: 1. The amount of zeolite was 33% by weight based on the total weight of the catalyst mixture Example B9 Another catalyst was prepared analogously to Example 1 but with a weight ratio of Pt. aluminum silicate / zeolite mixture of 1: 2. To reach the same concentration of platinum as in example 1, the aluminum silicate was coated with 2.94% by weight of platinum.The exact composition of the catalyst can be extract from Table 4. Example B1Q Another catalyst was prepared analogously to Example 7 but with a weight ratio of aluminum Pt-aluminum silicate / zeolite mixture of 5: 1. Example B11-16 Six catalysts were prepared analogously to Example 1 with different concentrations of platinum. of Pt - aluminum silicate with platinum contents of 1, 06; 1, 17; 0.59; 0.29; 0.15 and 0.06% by weight.

Example 17 A catalyst according to Example 13 was further coated with 0.18 g of Pt / 1 of honeycomb body by 30% of its length with the coating dispersion for the catalyst of Example 9. The additional coating presented a concentration of 39 g / l of honeycomb body volume. The finished catalyst contained 209 g of oxides per liter of honeycomb body and had a concentration of 0.72 g of Pt / 1. Example B18 The additional coating of the catalyst of example 15 was applied from each front surface of the honeycomb body about every 15% of the length of the honeycomb cell. Example B19 A catalyst according to Example 10 was prepared with 1.41 g of Pt / I of the honeycomb body but only with 60 g / dm3 of aluminum silicate. For this catalyst, an aluminum Pt-silicate with a platinum content of 2.34% by weight (double Pt content compared to Example 10) was prepared. Example B2Q A catalyst was prepared with 140 g / 1 Pt-aluminum silicate and 100 g / l zeolite mixture. The platinum content of the Pt-aluminum silicate was 1.0% by weight. The finished catalyst contained 1.41 g of Pt / 1. Example B21 A catalyst was prepared according to example 10. For the activation of the aluminum silicate, an aqueous solution of hexachloropyatinic acid was used. Example B22 A catalyst was prepared according to example 10. For the activation of the aluminum silicate, an aqueous solution of platinum nitrate (II) was used.

Example B23 A catalyst was prepared according to example 9. Palladium, introduced by means of an aqueous solution of palladium (II) nitrate, was used to activate the aluminum silicate. Example B24 A catalyst was prepared according to example 1. A mixture of platinum and rhodium in a 5: 1 ratio was used for the activation of aluminum silicate. As the precursor stage of platinum, hexachloroplatinic acid was applied and as a rhodium precursor stage. rhodium (III) chloride. Example B25 A catalyst was prepared according to example 1. For the activation of the aluminum silicate, a mixture of platinum, palladium and rhodium in a ratio of 10: 1: 3 was used. Tetraaminplatinum hydroxide was applied as a precursor to the platinum. (II), as a precursor to palladium palladium nitrate (II) and as a precursor to rhodium nitrate rhodium (II). Example B26 A catalyst was prepared according to example 10. For the activation of the aluminum silicate, an aqueous solution of methylethanolamine-platinum (II) hydroxide was used. Example B27 A catalyst was prepared according to example 1. Unlike example 1, the activated aluminum silicate was not reduced with platinum in the formation gas stream but only calcined for 2 hours in the air at 600 ° C. . Example B28 A catalyst was prepared according to example 1, but the aluminum Pt-silicate was not dried and calcined or reduced after impregnation but was it immediately mixed with the zeolite mixture and continued to be treated until the coating dispersion was obtained. For this purpose, the aluminum silicate was dispersed in an aqueous solution of platinum nitrate (II). The pH value of the dispersion was then raised by adding a concentrated aqueous ammonia solution to a value of 9. The zeolite mixture was then mixed with the dispersion. The finished dispersion had a solids content of 40% by weight. Example B29 A catalyst was prepared according to example 28. Instead of platinum nitrate (II), an aqueous solution of tetraaminplatin (II) nitrate was used. The adjustment of the pH value to a value of 2 was carried out by means of the addition of saturated aliphatic monocarboxylic acid. Example B30 A catalyst was prepared according to example 17. In place of the cordierite ceramic honeycomb body a metal body in the shape of a honeycomb was also used., of open cells with a diameter of 2.5 cm, a length of 7.5 cm and 62 cells or current channels / cm2 and a wall thickness of the current channels of 0.04 mm. Example B31 A catalyst according to Example 9 was prepared. Instead of the aluminum silicate, an α-aluminum oxide with a specific surface area of 188 m2 / g was used. Example B32 A catalyst was prepared according to example 9. Instead of aluminum silicate, a titanium oxide with a specific surface area of 95 m2 / 9 was used.

Example B33 A catalyst according to Example 1 was prepared with the following modifications. The aluminum silicate was used with a surface decreased by calcination at 153 m2 / g (see Table 1). This material was impregnated with methylethanolamine-platinum (II) hydroxide as indicated in Example 26. As a mixture of zeolite, a mixture of DAY and Na-ZSM5 was chosen. The weight ratio between the aluminum silicate and the zeolites was adjusted to a value of 6: 1. The amount of coating per liter of volume of the honeycomb body was 140 g. In addition to the drying, recoction and reduction settings indicated in example 1, the catalyst was finally reduced for 2 hours in the die gas stream at 500 ° C. The finished catalyst contained 1.36 g of platinum per liter of catalyst volume. Example B34 A catalyst was prepared according to example 33. For the activation of aluminum silicate, an aqueous solution of tetraaminplatin (II) nitrate was used. Example B35 A catalyst was prepared according to example 34. As the carrier oxide, an aluminum silicate was used with 5% by weight of silicon dioxide and a specific surface area of 212 m2 / g (see Table 1). Example B36 A catalyst was prepared according to example 34. As the carrier oxide, an aluminum silicate was used with 5% by weight of silicon dioxide and a specific surface area of 320 m2 / g (see Table 1). Example B37 A catalyst was prepared according to example 36. As an oxide The carrier used an aluminum silicate with 10% by weight of silicon dioxide and a specific surface area of 163 m2 / g (see Table 1).

Example of application The catalytic activity of the exhaust gas purification catalysts of the previous examples was measured in a synthesis system. With this installation it is possible to simulate all the gas exhaust gas components present in the actual exhaust gas of a diesel or Otto engine. The selected test conditions and the composition of the model gas are indicated in Table 5. The hydrocarbon component was n-hexadecane, cetane Trivialname, which is known as a reference substance for the determination of the combustibility of diesel fuels. This long chain aliphatic compound is also found in notorious amounts in real diesel exhaust gas. For the measurement of the gas components contained in the exhaust gas, the measurement instruments indicated in Table 6 were used. In the synthesis gas installation, the conversions of carbon monoxide and hydrocarbons in the permanent operation at gas temperatures were measured. of 140 ° C exhaust. The measurements were made in both fresh and aged catalysts (oven aging: 16 a 750 ° C in the air + 10% in vol. of H2O + 25 ppm of SO2). To determine the starting temperatures, the exhaust gas was heated at a heating rate of 15 ° C / min. The determination of the conversion of nitrogen oxides was carried out at an exhaust gas temperature of 200 ° C. The calculation of the conversion speeds was carried out with the following formula N E - N A? =. 100% N E X = conversion rate [%] NE = concentration of the noxious substance before the catalyst [vppm] NA = concentration of the noxious substance after the catalyst [vppm] The conversions of harmful substances obtained with the catalysts of the comparative examples and the example B1 are indicated in Tables 7 and 8. Table 7 deals with the performance data of the fresh catalysts, while in Table 8 the results were obtained with catalysts that had been subjected to an oven aging of 16 ha 750 ° C of air + 10% in vol.de H2O + 25 ppm of S02. Table 5 Test conditions and composition of the model gas for the determination of the conversion rates of harmful substances CO, HC, Nox and SO2 in the synthesis gas installation.

Concentration component CO 350 [vppm] H2 117 [vppm] C16H34 90 [vppm] S02 25 [vppm] NO 270 [vppm] o2 6 [% in vol.] H20 10 [% in vol.] C02 10.7 [% in vol.] N2 rest amount of gas 1950 [Nl / h] catalyst size f 25 mm x 76 mm speed in space 50000 [h'1] heating speed 15 [° C / min] Table 6 Arrangement of the measuring devices for the measurement of the concentration of the exhaust gas in the test state of the synthesis gas Analyzed gas Measuring device Manufacturer 02 Oxymat Siemens AG hydrocarbon FID Pierburg messtechnik Nox CLD 700 Elht Zellweger ECO-Systeme CO Binos Rosemount C02 Binos Rosemount S02 Binos Rosemount Table 7 Conversion of harmful substances by catalysts of examples B1-B32 and V1-V4 in the fresh state Example T50% Conversion to Conversion at 140 ° C 200 ° C [° C] [%] [%] CO HC CO HC NOx V1 145 155 35 26 11 V2 160 175 17 10 1 V3 150 160 29 25 9 V4 202 < 75 5 78 5 B1 138 < 75 55 83 59 B2 148 < 75 46 77 40 B3 147 < 75 52 75 46 B4 148 < 75 47 75 45 B5 146 < 75 47 75 45 B6 145 < 75 50 76 44 Example T50% Conversion to Conversion at 140 ° C 200 ° C [° C] [%] [%] CO HC CO HC NOy B7 144 < 75 47 80 42 B8 140 < 75 50 83 48 B9 139 < 75 53 87 58 B10 140 < 75 50 78 59 B11 135 < 75 55 83 70 B12 142 < 75 45 85 61 B13 155 < 75 22 85 50 B14 160 < 75 15 80 48 B15 171 < 75 5 74 48 B16 185 < 75 5 76 40 B17 147 < 75 46 78 48 Example T50% Conversion to Conversion at 140 ° C 200 ° C [° C] [%] [%] CO HC CO HC NOx B18 144 < 75 47 78 55 B19 141 < 75 49 83 59 B20 139 < 75 51 79 61 B21 141 < 75 47 80 55 B22 183 < 75 10 78 12 B23 175 < 75 25 85 18 B24 145 < 75 45 83 51 B25 149 < 75 45 79 45? B26 144 < 75 47 86 59 B27 141 < 75 70 81 75 0p74S2ß 141 < 75 69 80 73 Example T50% Conversion to Conversion at 140 ° C 200 ° C 5 [° C] [%] [%] CO HC CO HC NOx B29 137 < 75 69 80 73 0 B30 141 < 75 59 82 70 B31 137 < 75 49 78 55 B32 139 < 75 51 81 59 5 B33 133 < 75 98 80 40 B34 137 < 75 90 80 38 B35 138 < 75 83 79 41 B36 141 < 75 65 78 37 B37 135 < 75 94 81 37 Table 8 Conversion of harmful substances by catalysts of selected examples after oven aging (16 h, 750 ° C, air + 10 vol of H2O + 25 ppm of SO2) Example T50% Conversion to Conversion at 140 ° C 200 ° C [° C] [%] [%] CO HC CO HC NOx V1 199 215 V2 209 235 V3 190 199 8 8 V4 222 < 75 1 76 B1 175 < 75 18 75 53 B2 180 < 75 13 B3 188 < 75 12 70 29 B4 187 < 75 11 71 26 B5 186 < 75 13 69 31 B6 186 < 75 12 71 30 Ejenr íplo T50% Conversion to Conversion at 140 ° C 200 ° C [° C] [%] [%] CO HC CO HC NOx B7 180 < 75 14 70 31 B8 177 < 75 16 75 40 B32 185 < 75 11 74 41 B33 174 < 75 21 76 35 It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects or products to which it refers. Having described the invention as above, property is claimed as contained in the following:

Claims (9)

1. Catalyst for exhaust gas purification of die engines: containing one or more zeolites as well as at least one metal of the platinum group c, characterized in that the catalyst additionally contains one or several metal oxides of the group aluminum silicate, aluminum oxide and titanium oxide wherein the aluminum silicate has a weight ratio of silicon dioxide aluminum dioxide of 0.005 to 1 and the metals of the platinum group are only embedded on these additional metal oxides.

2. Catalyst according to claim 1, characterized in that the mixture of zeoites is composed of up to five zeolites with different moduli

3. Catalyst according to claim 2, characterized in that it contains a mixture of zeolites of at least two zeolites with larger moduli. 10, of which one has a modulus less than 50 and the one has a modulus greater than 200.

4. Catalyst according to claim 3, characterized in that the weight ratio of the additional metal oxides including the metals of the platinum with respect to the mixture of zeolites ranges from 10: 1 to 1: 3, preferably between 6: 1 and 2: 1. Catalyst according to claim 1, characterized in that it contains an aluminum silicate activated with platinum and a mixture of zeolite of u Y-zeolite dealuminizada and a Na-ZSM5-zeolite with modules greater than 12 where aluminum silicate has a specific surface between 100 and 200 ng , which is covered with 0.05 to 0.2 mg Pt / m2. Catalyst according to claim 5, characterized in that weight ratio of the aluminum silicate to the mixture of zeolite between 6: 1 and 2: 1. Catalyst according to one of the preceding claims, characterized in that it is applied on the inner walls of a honeycomb body of 50 to 400 g / l volume of honeycomb body in the form of a coating. Catalyst according to one of the preceding claims, characterized in that the metals of the diethylene group are present in a concentration of 0.01 to 5 g / 1 volume of the honeycomb body. Use of the catalyst according to one of the preceding claims for the purification of exhaust gases from diesel engines.