Catalytically active material, method for producing same, and use thereof

Abstract

A catalytically active material is provided. The material includes a mixed oxide having a first metal selected from group 4 of the periodic table of elements and/or a second metal, and at least one further metal selected from group 11 of the periodic table of elements, wherein the macroscopic composition of the material given by the chemical formula corresponds to the composition of the material at a molecular level. A coating made of such a material is also provide, as is an article having such a coating, and a method for producing such a material.

Claims

1. A mixed oxide catalytically active material, comprising: a first metal (M1) selected from group 4 of the periodic table of elements and/or a second metal (M2); a third metal (M3) selected from group 11 of the periodic table of elements, wherein each of the first and/or second and third metals (M1, M2, M3) is present at an oxidation state greater than 0 and mixed at a molecular level so that a macroscopic composition given by the chemical formula of the material corresponds to the composition of the material at the molecular level; a catalytic activity that occurs at temperatures below 300? C., wherein the catalytic activity is defined as a start of oxidative decomposition of organic carbonaceous combustion products; a ratio V.sub.M,atomic of a content of the third metal (M3) to a sum of contents of the other metals (M1, M2) based on the atomic composition, $V_{M,\mathrm{atomic}}=\frac{M3}{.Math.\left(M1+M2\right)},$ is between 1 and 1:6; and a temperature resistance of at least 600? C.

2. The catalytically active material of claim 1, wherein the ratio V.sub.M,atomic is between 1 and 1:3.

3. The catalytically active material of claim 1, wherein the first metal (M1) comprises titanium and/or zirconium.

4. The catalytically active material of claim 1, wherein the second metal (M2) comprises a lanthanide.

5. The catalytically active material of claim 1, wherein the second metal (M2) comprises cerium.

6. The catalytically active material of claim 1, wherein the third metal (M3) is copper.

7. The catalytically active material of claim 1, further comprising an atomic ratio of the first metal (M1) to the second metal (M2) of 1:4.

8. The catalytically active material of claim 1, further comprising a porosity of less than 25 vol %.

9. The catalytically active material of claim 1, further comprising a refractive index between 1.7 and 2.2 at a wavelength of 589 nm.

10. A coating made of the catalytically active material of claim 1.

11. The coating of claim 10, comprising a transmittance of greater than 80% for electromagnetic radiation in a range from 380 to 780 nm.

12. The coating of claim 10, further comprising one or more components selected from the group consisting of Si, Al, Na, Li, Sr, B, P, Sb, Ti, F, MgF.sub.2, CaF.sub.2, and combinations thereof.

13. The coating of claim 10, further comprising inorganic amorphous and/or crystalline nanoparticles.

14. The coating of claim 10, further comprising oxidic nanoparticles having a mean diameter from 4 nm to 30 nm.

15. A mixed oxide catalytically active material, comprising: a first metal (M1) selected from group 4 of the periodic table of elements and/or a second metal (M2); a third metal (M3) selected from group 11 of the periodic table of elements, wherein each of the first and/or second and third metals (M1, M2, M3) is present at an oxidation state greater than 0 and mixed at a molecular level so that a macroscopic composition given by the chemical formula of the material corresponds to the composition of the material at the molecular level; a catalytic activity that occurs at temperatures below 300? C., wherein the catalytic activity is defined as a start of oxidative decomposition of organic carbonaceous combustion products; a ratio V.sub.M,atomic of a content of the third metal (M3) to a sum of contents of the other metals (M1, M2) based on the atomic composition, $V_{M,\mathrm{atomic}}=\frac{M3}{.Math.\left(M1+M2\right)},$ is between 1 and 1:6; and at least in part, a nanocrystalline fraction, wherein the nanocrystalline fraction is greater than 25 vol %.

16. The catalytically active material of claim 15, wherein the nanocrystalline fraction comprises nanocrystals having a crystallite size from 4 to 50 nm, wherein the crystallite size is specified as a mean diameter of the crystallites.

17. The catalytically active material of claim 15, further comprising a granular structure in which nanocrystals of the nanocrystalline fraction do not have a preferred orientation so that the nanocrystals are randomly distributed.

18. A mixed oxide catalytically active material, comprising: a first metal (M1) selected from group 4 of the periodic table of elements and/or a second metal (M2), the second metal (M2) comprising a lanthanide; a third metal (M3) selected from group 11 of the periodic table of elements, wherein each of the first and/or second and third metals (M1, M2, M3) is present at an oxidation state greater than 0 and mixed at a molecular level so that a macroscopic composition given by the chemical formula of the material corresponds to the composition of the material at the molecular level; a catalytic activity that occurs at temperatures below 300? C., wherein the catalytic activity is defined as a start of oxidative decomposition of organic carbonaceous combustion products; a ratio V.sub.M,atomic of a content of the third metal (M3) to a sum of contents of the other metals (M1, M2) based on the atomic composition, $V_{M,\mathrm{atomic}}=\frac{M3}{.Math.\left(M1+M2\right)},$ is between 1 and 1:6; and a refractive index between 1.7 and 2.2 at a wavelength of 589 nm.

19. A coated article comprising: a substrate made of a material selected from the group consisting of glass, glass ceramic, ceramic, metal, enamel, and plastic; and a coating made of the catalytically active material of claim 1 on the substrate.

20. The coated article of claim 19, wherein the coating a thickness of at least 5 nm and at most 100 nm.

21. The coated article of claim 19, further comprising at least one layer applied between the substrate and the coating.

22. The coated article of claim 19, wherein the substrate is a transparent glass ceramic.

23. The coated article of claim 22, wherein the transparent glass ceramic has a glassy zone of a thickness in a range from 50 nm to 10 ?m.

24. The coat coated article of claim 22, wherein the glass ceramic comprises an element selected from the group consisting of Si, O, Na, Zr, Ca, Ti, Mg, Nb, B, Sr, La, Li, and combinations thereof.

25. The coated article of claim 19, wherein the coating comprises the catalytically active material embedded in a glassy matrix.

26. A mixed oxide catalytically active material, comprising: a first metal (M1) selected from group 4 of the periodic table of elements and/or a second metal (M2); a third metal (M3) selected from group 11 of the periodic table of elements, wherein each of the first and/or second and third metals (M1, M2, M3) is present at an oxidation state greater than 0 and mixed at a molecular level so that a macroscopic composition given by the chemical formula of the material corresponds to the composition of the material at the molecular level; a catalytic activity that occurs at temperatures below 300? C., wherein the catalytic activity is defined as a start of oxidative decomposition of organic carbonaceous combustion products; a ratio V.sub.M,atomic of a content of the third metal (M3) to a sum of contents of the other metals (M1, M2) based on the atomic composition, $V_{M,\mathrm{atomic}}=\frac{M3}{.Math.\left(M1+M2\right)},$ is between 1 and 1:6, and one of a temperature resistance of at least 600? C., a porosity of less than 25 vol %, and a refractive index between 1.7 and 2.2 at a wavelength of 589 nm.

27. A coated article comprising: a transparent substrate made of a material selected from the group consisting of glass, glass ceramic, ceramic, metal, enamel, and plastic; a transparent coating made of a mixed oxide catalytically active material on the substrate, the mixed oxide catalytically active material comprising: a first metal (M1) selected from group 4 of the periodic table of elements and/or a second metal (M2); a third metal (M3) selected from group 11 of the periodic table of elements, wherein each of the first and/or second and third metals (M1, M2, M3) is present at an oxidation state greater than 0 and mixed at a molecular level so that a macroscopic composition given by the chemical formula of the material corresponds to the composition of the material at the molecular level; a catalytic activity that occurs at temperatures below 300? C., wherein the catalytic activity is defined as a start of oxidative decomposition of organic carbonaceous combustion products; and a ratio V.sub.M,atomic of a content of the third metal (M3) to a sum of contents of the other metals (M1, M2) based on the atomic composition, $V_{M,\mathrm{atomic}}=\frac{M3}{.Math.\left(M1+M2\right)},$ is between 1 and 1:6.

28. The coated article of claim 27, further comprising at least one decorative layer applied between the transparent substrate and the transparent coating.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 schematically shows a ternary diagram of materials, in which compositions according to the invention are indicated;

(2) FIG. 2 shows a diagram of differential thermogravimetric measurements relating to the oxidative decomposition of soot on different coatings and on a non-coated reference sample; and

(3) FIG. 3 shows an article having a coating of a catalytically active material according to the invention.

DETAILED DESCRIPTION

(4) FIG. 1 schematically shows a ternary diagram of materials, in which compositions of the catalytically active material according to the present invention are indicated as a function of the metals or cations contained in the material. It is favorable in this case to solely consider the relevant content of metals, since in an oxidation catalyst the oxygen content usually is not equal to the precise stoichiometric content which is obtained by calculation with the assumption of specific oxidation states. However, this is why it is not possible to accurately indicate the molar ratios of specific metal oxides in such a catalytically active material.

(5) At each of the vertices of the triangle, the respective designated material is present as the only metal or as the only cation in the corresponding oxidic compound. At the edges of the triangle, the composition varies between two respective metals, for example between M3 and M2 at the base of the triangle. Compositions containing all three metals are located in the area of the illustrated triangle.

(6) Furthermore in FIG. 1, the approximate location of a composition 1 of a catalytically active material according to the present invention is indicated, which in terms of the atomic content of metals includes equal fractions of the metal M1 and the metal M3. The ratio V.sub.M,atomic of M3 to the sum of metals M1 and M2 is therefore 1 in this case. If zirconium is used as the metal M1 and copper as the metal M3, a composition is obtained which corresponds to the coating solution of implementation example 1, or to the composition of the coating of implementation example 2. However, generally, without being limited to the example discussed herein it is also possible that not a single pure metal is used as M1, but rather a mixture of two suitable metals M1. In addition to or instead of zirconium, for example, hafnium or titanium could be used. In such a case, the respective atomic contents would add up, that is the content of M1 would be composed of the sum of the contents of titanium, zirconium, and/or hafnium.

(7) Furthermore, the approximate location of a compositions 2 of a catalytically active material according to the present invention is indicated, which only comprises a metal M2 and a metal M3. In this example, the content of metal M3 only amounts to one part, and that of metal M2 to three parts. Thus, the ratio V.sub.M,atomic has a value of 1:3. If cerium is used as the only metal M2 and copper as the only metal M3, a composition of the catalytically active material is obtained which corresponds to the solution of implementation example 3 or to the composition of the coating according to implementation example 4, respectively. However, similarly as with metal M1 it is also possible that a plurality of metals M2 are contained in the catalytically active material of the present invention, and in this case, again, the respective atomic contents would add up, i.e. M2 would be composed of the sum of the contents of the individual metals M2.

(8) Furthermore, the approximate location of a composition 3 is indicated, which includes 3 parts of M1 and additionally three parts of M2 and one part of M3. Here, a ratio V.sub.M,atomic of 1:6 is resulting. If only zirconium is used as M1, only cerium as the metal M2, and furthermore copper as the metal M3, a composition is obtained which corresponds to the composition of implementation example 5 or to the coating of implementation example 6, respectively.

(9) Also indicated is the approximate location of a composition 4 of a catalytically active material of the present invention. In this case, the catalytically active material has a ratio V.sub.M,atomic of 1, i.e. equal parts of M2 and M3 are included. If cerium and copper are used as M2 and M3, respectively, this corresponds to the composition of implementation example 7.

(10) Particularly preferred are compositions of the catalytically active material in which the ratio of M1 to M2 is 1:4. Such compositions are located on a section line through the ternary space, which is indicated as a straight line 5 in the diagram of FIG. 1. The approximate locations of such preferred compositions 6 and 7 are also indicated in the ternary diagram. In terms of its atomic composition, composition 6 includes a content of one part of M1, four parts of M2, and 3 parts of M3. Thus, the ratio V.sub.M,atomic resulting therefrom is 3:(1+4), or 1:1.667. If zirconium is used as M1, cerium as M2, and copper as M3, a macroscopic composition 6 or chemical formula of the catalytically active material of Cu.sub.3Ce.sub.4ZrO.sub.x is obtained, with an oxygen content that cannot be accurately determined due to varying valences. Furthermore, composition 7 includes 3 parts of M1, 12 parts of M2, and 5 parts of M3. The ratio V.sub.M,atomic resulting therefrom is 5:(12+3), or 1:3. If zirconium is used as M1, cerium as M2, and copper as M3, a macroscopic composition 7 or chemical formula of the catalytically active material of Cu.sub.5Ce.sub.12Zr.sub.3O.sub.y is obtained, with an oxygen content that cannot be accurately determined due to varying valences, similarly as in case of composition 6. Catalytically active materials having a ratio V.sub.M,atomic of 1:3 and in which furthermore the ratio of M1 to M2 is 1:4 are preferred herein. Particularly preferred is a catalytically active material in which the metals zirconium, cerium, and copper are included in an atomic ratio of 3 to 12 to 5 and which has the chemical formula Cu.sub.5Ce.sub.12Zr.sub.3O.sub.y, with an oxygen content that cannot be precisely specified because of changing valences.

(11) Without being limited to the implementation examples described herein, it has been generally been found that compositions exhibiting a particularly high catalytic activity are located in the sub-portion 8 of the ternary system consisting of materials M1, M2, and M3, although compositions that include only M1 and M2, i.e. which are located in the region of the binary system of M1 and M2 that is limiting the ternary system, do not represent compositions according to the invention. However, already slight doping with a metal M3, e.g. copper, provides a catalytically active material.

(12) FIG. 2 shows the behavior of differently synthesized powder samples in the degradation of a carbonaceous organic compound, in this case soot Printex U by way of example, for a composition of a catalytically active material that corresponds to the composition 7 of FIG. 1, i.e. which has a chemical formula of Cu.sub.5Ce.sub.12Zr.sub.3O.sub.y,

(13) Powder samples SOL450 TC and SOL650 TC were produced as described under implementation example 9 and were sintered at 450? C. and 650? C., respectively.

(14) With these powder samples, a measurable catalytic effect arises starting at a temperature of about 260? C. (sample SOL650 TC) and about 280? C. (SOL450 TC), respectively. As can be seen in FIG. 2, this catalytic effect can be determined by differential thermogravimetry and is evident by an increase in the differential thermogravimetric graph (DTG). Furthermore it can be seen that the soot is completely decomposed already at a temperature of about 375? C. (sample SOL450 TC) and of about 390? C. (sample SOL650 TC), respectively. If, by contrast, soot is subjected to such differential thermogravimetry without the addition of a catalytically active material according to the invention (see curve Printex U), the soot begins to decompose to any significant extent only starting at about 475? C. Complete decomposition of the carbonaceous combustion products occurs at a temperature of 640? C. Thus, with a catalytic material of the invention the temperature for complete decomposition of soot is reduced by about 250? C.

(15) So, in the context of the present invention catalytic activity means that the oxidative decomposition of soot or of carbonaceous organic combustion products begins. Catalytic activity of the material is therefore defined as the start of oxidative decomposition of organic carbonaceous combustion products, such as soot.

(16) On a sheet provided with a coating, for example a glass or glass ceramic sheet, the effect will occur in the same temperature range. This can be measured, for example, by placing a coated sheet contaminated with carbonaceous organic combustion products in an oven under a defined temperature, and by comparing the optical transmittance of the coated but uncontaminated sheet with that of the sheet contaminated with carbonaceous organic combustion products and then treated in the oven.

(17) Further evidence of the catalytic activity of the catalytically active material of the invention is obtained when installing a sheet coated with the material of the invention in a furnace and performing combustion under reduced oxygen supply. In this case, the sheet will become strongly covered by carbonaceous organic combustion products to exhibit what is known as sooting.

(18) Subsequently, the furnace is operated under normal conditions, i.e. with sufficient supply of oxygen, and the temperature at the sheet is recorded using a thermal imaging camera. Now it can be determined, again by a measurement of transmittance, whether the original transparence could be restored by the catalytic decomposition of the contamination.

(19) However, these effects can be verified on a purely visual basis as well. After the decomposition of the soot, the powder will again be in the form of its original color and it will be possible to look through the sheet again.

(20) FIG. 3 shows an inventive article 10 that has a coating 101 made of a catalytically active material according to the present invention. Article 10 consists of a substrate which may be a glass, glass ceramic, ceramic, metal, enamel, and/or a plastic substrate, for example. The coating preferably has a thickness of at least 5 nm and at most 100 nm, preferably of at least 10 nm and at most 90 nm. Furthermore preferably, the coating exhibits a transmittance in a range of greater than 80%, preferably greater than 85%, and more preferably greater than 88% for electromagnetic radiation in the range from 380 to 780 nm. Furthermore preferably, the refractive index of the coating at a wavelength of 589 nm is from 1.7 to 2.2, preferably from 1.8 to 2.1.

(21) According to another embodiment of the invention, in addition to the catalytically active material, such a coating may furthermore include one or more components selected from the group consisting of Si, Al, Na, Li, Sr, B, P, Sb, Ti, F, and/or MgF.sub.2, and/or CaF.sub.2, and alternatively or additionally inorganic amorphous and/or crystalline nanoparticles, preferably oxidic nanoparticles having a mean diameter from 4 nm to 30 nm.

(22) Preferably, such an article 10 is formed as a viewing window or an inner lining, for example as a viewing window for an oven or another cooking appliance, or as a viewing window for a fireplace or another stove, or as an inner lining for an oven or furnace or for exhaust pipes or chimneys. The article 10 is therefore an article which is exposed to a high temperature load of up to 700? C. in operation.

(23) Preferably, such a material is produced by a method for creating a material structure from a fluid phase on a support, comprising the steps of: separating the starting substances so that they are released from their solid-state association to be provided in the form of reactive particles in a surrounding fluid; solvating the reactive particles by at least one component of the fluid surrounding the particles so that the particles are provided in the form of a solvated complex; and preferably generating a potential gradient between the fluid and a support so that the solvated reactive particles reactively join together on the support to form a material mixed at a molecular level so as to form a mixed oxide.

(24) According to another embodiment of the invention, the creation of a material structure may be followed by a post-treatment step so as to adjust adhesion between the material and the support, preferably a thermal post-treatment such as in the form of drying and/or sintering.

LIST OF REFERENCE NUMERALS

(25) M1 Metal, preferably present in oxidation state +4 in compounds M2 Metal, preferably present in oxidation state +4 in oxides M3 Metal, selected from group 11 of the periodic table of elements 1 Composition of a catalytically active material including M1 and M3 2, 4 Composition of a catalytically active material including M2 and M3 3, 6, 7 Composition of a catalytically active material including M1, M2, and M3 Preferred composition range of the ternary system of materials M1, M2, and M3 Exactly a ratio M1:M2 of 1:4 in the ternary system of materials M1, M2 and M3 10 Article with catalytically active coating 101 Catalytically active coating