US2685547A - Platinum catalysts - Google Patents
Platinum catalysts Download PDFInfo
- Publication number
- US2685547A US2685547A US268133A US26813352A US2685547A US 2685547 A US2685547 A US 2685547A US 268133 A US268133 A US 268133A US 26813352 A US26813352 A US 26813352A US 2685547 A US2685547 A US 2685547A
- Authority
- US
- United States
- Prior art keywords
- platinum
- wires
- catalysts
- elements
- catalyst
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 title claims description 44
- 239000003054 catalyst Substances 0.000 title description 37
- 229910052697 platinum Inorganic materials 0.000 title description 18
- 239000013078 crystal Substances 0.000 claims description 19
- 238000006555 catalytic reaction Methods 0.000 claims description 2
- 238000000137 annealing Methods 0.000 description 12
- 229910001260 Pt alloy Inorganic materials 0.000 description 10
- 238000010438 heat treatment Methods 0.000 description 6
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 4
- PXXKQOPKNFECSZ-UHFFFAOYSA-N platinum rhodium Chemical compound [Rh].[Pt] PXXKQOPKNFECSZ-UHFFFAOYSA-N 0.000 description 4
- 238000001953 recrystallisation Methods 0.000 description 4
- 229910000629 Rh alloy Inorganic materials 0.000 description 3
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 3
- 238000009941 weaving Methods 0.000 description 3
- 229910021529 ammonia Inorganic materials 0.000 description 2
- 230000003197 catalytic effect Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- -1 for example Chemical compound 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229910052703 rhodium Inorganic materials 0.000 description 1
- 239000010948 rhodium Substances 0.000 description 1
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 1
- 238000007788 roughening Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
- B01J23/42—Platinum
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
Definitions
- the present invention relates to improvements in shaped self-supportin platinum and platinum alloy catalysts employed in high temperature reactions such as the catalytic oxidation of ammonia and the cracking of hydrocarbons.
- Platinum catalysts are usually used in the form of networks of wires or strips or other structures which are produced from the appropriately worked platinum or platinum alloys such as, for example, platinum-rhodium alloys.
- the networks required are, for example, woven from" drawn unannealed wires, as annealed wires are not well suited to weaving.
- the life of platinum as well as platinum alloy catalysts can be substantially increased by subjecting the finished catalyst structures to an annealing at temperatures at least 150 C. and preferably 300 C.-500 C. over the recrystallization temperature of the platinum or platinum alloy from which they are formed for a sufficient period of time that the crystal structure of the individual catalyst elements, namely, the wires or strips and the like is such that the majority of the individual crystals are so dimensioned that they reach across the smallest dimension of the individual catalyst elements.
- the annealing temperature is below the melting point of the platinum or platinum alloy from which the catalyst is formed.
- Such annealing is continued until the upon the composition of the catalyst elements and to a slight extent upon the degree the platinum or platinum alloy has been worked.
- the recrystallization temperature of pure platinum which has been worked about 9.0% is about 900 C.
- the recrystallization temperature of platinum alloys is higher, for example, for a platinum rhodium alloy containing 5% of rhodium, it is around .1000" C.
- the recrystallization temperature can easily be recognized, as it is the temperature at whichadecrease in the deformation hardness begins.
- the duration of the annealing treatment according to the invention depends upon the crosssection .of individual catalyst elements from which the catalysts are formed and can vary between wide limits. As the annealing, according .to the invention, is continued until the catalyst elements are substantially composed of crystals of such dimensions that they reach across the entire smallest dimension of such elements, the required duration of the annealing increases with increased thickness of the elements.
- the annealing in accordance with the invention is preferably accomplished by direct current resistance heating of the catalyst itself as more easily reproducible .results are obtained and the time required for the annealing is considerably shortened. .Preferably low voltage such as 10-20 volts are employed for the resistance heating.
- the catalysts are preferably hung free in the annealing ,ovens to avoid contact with each other and the oven walls. The time required for such annealing is, however, considerably longer than when electric resistance heating is employed.
- the crystal structure of catalyst elements formed of pure platinum wires drawn more than 80% and having a diameter of 40-60 microns can be transformed to the desired structure according to the invention by annealing such elements for 3 to 5 hours at 1250 C.
- similarly suitable results can be obtained by electric resistance heating for about 20 minutes at 1350 C.
- Wires of larger diameter require longer treatment, for example, wires of 0.1 mm. diameter require 1 hours electric resistance heating to produce similar results, namely, a crystal structure in which single crystals take up the entire transverse cross-section of the wire.
- OHEMICALLY PURE Pt WIRES Catalysts produced according to the invention have been found to possess catalytic activity substantially identical with those previously employed. They are employed with extreme advantage in the oxidation of ammonia to nitrogen oxides wherein high temperatures such as about 800 C. are employed, as the amount of platinum lost therefrom is substantially less than from the ordinarily employed catalysts which have not been annealed to provide the crystal structure according to the invention and, consequently, have a considerably longer life.
- catalysts for example, woven networks, which have been annealed according to the invention so that the crystal structure is such that the majority of the individual crystals reach across the smallest dimension of the wires or strips and preferably so that such crystals have a length which is a multiple of the smallest dimension of the wires or strips, will withstand the normal stresses and strains encountered during use as a catalyst.
- metallic platinum catalyst as used herein and in the appended claims is intended to cover not only pure platinum catalyst, but also platinum alloy catalysts. Accordingly, also the term platinum metal elements from which such metallic platinum catalysts are formed is used herein and in the appended claims not only to signify elements formed of pure platinum, but also elements formed of platinum alloys.
- the treatment of the catalysts in accordance with the new invention is not merely limited to catalysts formed of physically pure platinum. Surprisingly, it was found that the desired life increasing crystal structure may also be obtained in using chemically pure platinum as such or chemically pure platinum alloys for the manufacture of said catalysts.
- a woven platinum wire network suitable for high temperature catalytic reactions the wires of which are substantially composed of crystals having a cross-section transverse to the longitudinal axis of the wires identical with the transverse cross-section of the wires and whose size in the direction of the longitudinal axis of the wires is a multiple of the diameter of the wires.
- a self supporting platinum metal catalyst consisting of a network formed of a plurality of relatively thin extended platinum metal elements, wherein the elements are substantially composed of crystals whose size in the direction of the thinnest dimension of such elements is equal to such thinnest dimension and the size of such crystals in the direction transverse to the thinnest dimension of such elements is a multiple of such thinnest dimension.
- a self supporting platinum-rhodium alloy catalyst consisting of a network formed of a plurality of relatively thin extended platinumrhodium alloy elements, wherein the elements are substantially composed of crystals whose size in the direction of the thinnest dimension of such elements is equal to such thinnest dimension and the size of such crystals in the direction transverse to the thinnest dimension of such elements is a multiple of such thinnest dimension.
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Catalysts (AREA)
Description
Patented Aug. 3, 1954 PLATINUM CATALYSTS Hermann Holzmann and Gerhard Reinacher, .Hanau (Main), Germany,assignors to Deutsche Goldund Silber-Scheideanstalt vormals .Roessler, Frankfurt am Main, Germany, a corporation of Germany No Drawing. Application January 24, 1952, Serial No. 268,133
Claims priority, application Germany January 24, 1951 3 Claims. 1
The present invention relates to improvements in shaped self-supportin platinum and platinum alloy catalysts employed in high temperature reactions such as the catalytic oxidation of ammonia and the cracking of hydrocarbons.
Considerable losses in platinum from the catalysts usually occur at the high temperature at which they are employed such as 650 0. to 1000 (3. Such losses, to a great extent, are caused by the change in structure "of the catalyst during use which causes considerable roughening and loosening of the surface of the catalyst so that particles thereof are carried oii with the reaction gases. These structural changes and losses not only reduce the strength of the catalyst bodies,
It is a further object of the invention to provide platinum catalysts having a substantially longer life than those heretofore employed.
Platinum catalysts are usually used in the form of networks of wires or strips or other structures which are produced from the appropriately worked platinum or platinum alloys such as, for example, platinum-rhodium alloys. The networks required are, for example, woven from" drawn unannealed wires, as annealed wires are not well suited to weaving.
In accordance with the invention, it has been unexpectedly discovered that the life of platinum as well as platinum alloy catalysts can be substantially increased by subjecting the finished catalyst structures to an annealing at temperatures at least 150 C. and preferably 300 C.-500 C. over the recrystallization temperature of the platinum or platinum alloy from which they are formed for a sufficient period of time that the crystal structure of the individual catalyst elements, namely, the wires or strips and the like is such that the majority of the individual crystals are so dimensioned that they reach across the smallest dimension of the individual catalyst elements. The annealing temperature, of course, is below the melting point of the platinum or platinum alloy from which the catalyst is formed.
Preferably such annealing is continued until the upon the composition of the catalyst elements and to a slight extent upon the degree the platinum or platinum alloy has been worked. The recrystallization temperature of pure platinum which has been worked about 9.0% is about 900 C. The recrystallization temperature of platinum alloys is higher, for example, for a platinum rhodium alloy containing 5% of rhodium, it is around .1000" C. The recrystallization temperature can easily be recognized, as it is the temperature at whichadecrease in the deformation hardness begins.
The duration of the annealing treatment according to the invention depends upon the crosssection .of individual catalyst elements from which the catalysts are formed and can vary between wide limits. As the annealing, according .to the invention, is continued until the catalyst elements are substantially composed of crystals of such dimensions that they reach across the entire smallest dimension of such elements, the required duration of the annealing increases with increased thickness of the elements.
The annealing in accordance with the invention is preferably accomplished by direct current resistance heating of the catalyst itself as more easily reproducible .results are obtained and the time required for the annealing is considerably shortened. .Preferably low voltage such as 10-20 volts are employed for the resistance heating. When indirect heating methods are employed, the catalysts are preferably hung free in the annealing ,ovens to avoid contact with each other and the oven walls. The time required for such annealing is, however, considerably longer than when electric resistance heating is employed. For example, the crystal structure of catalyst elements formed of pure platinum wires drawn more than 80% and having a diameter of 40-60 microns can be transformed to the desired structure according to the invention by annealing such elements for 3 to 5 hours at 1250 C. On the other hand, similarly suitable results can be obtained by electric resistance heating for about 20 minutes at 1350 C. Wires of larger diameter require longer treatment, for example, wires of 0.1 mm. diameter require 1 hours electric resistance heating to produce similar results, namely, a crystal structure in which single crystals take up the entire transverse cross-section of the wire.
The following tables illustrate the results obtained by annealing catalysts produced from wires of 60 microns diameter. substantially all of the crystals obtained are of In each instance a such thickness that they take up the entire transverse cross-section of the wires.
OHEMICALLY PURE Pt WIRES Catalysts produced according to the invention have been found to possess catalytic activity substantially identical with those previously employed. They are employed with extreme advantage in the oxidation of ammonia to nitrogen oxides wherein high temperatures such as about 800 C. are employed, as the amount of platinum lost therefrom is substantially less than from the ordinarily employed catalysts which have not been annealed to provide the crystal structure according to the invention and, consequently, have a considerably longer life.
While it is possible to provide the desired crystal structure in the wires or strips from which the catalysts are produced, for example, by weaving,
this has not been found satisfactory. The coarse crystalline structure of such wires or strips effect the mechanical properties in such a way as to render the formation of the catalyst, for example, by weaving, diflicult, if not impossible.
On the other hand, it has been found that catalysts, for example, woven networks, which have been annealed according to the invention so that the crystal structure is such that the majority of the individual crystals reach across the smallest dimension of the wires or strips and preferably so that such crystals have a length which is a multiple of the smallest dimension of the wires or strips, will withstand the normal stresses and strains encountered during use as a catalyst.
The term metallic platinum catalyst as used herein and in the appended claims is intended to cover not only pure platinum catalyst, but also platinum alloy catalysts. Accordingly, also the term platinum metal elements from which such metallic platinum catalysts are formed is used herein and in the appended claims not only to signify elements formed of pure platinum, but also elements formed of platinum alloys.
The treatment of the catalysts in accordance With the new invention is not merely limited to catalysts formed of physically pure platinum. Surprisingly, it was found that the desired life increasing crystal structure may also be obtained in using chemically pure platinum as such or chemically pure platinum alloys for the manufacture of said catalysts.
We claim:
1. A woven platinum wire network suitable for high temperature catalytic reactions the wires of which are substantially composed of crystals having a cross-section transverse to the longitudinal axis of the wires identical with the transverse cross-section of the wires and whose size in the direction of the longitudinal axis of the wires is a multiple of the diameter of the wires.
2. A self supporting platinum metal catalyst consisting of a network formed of a plurality of relatively thin extended platinum metal elements, wherein the elements are substantially composed of crystals whose size in the direction of the thinnest dimension of such elements is equal to such thinnest dimension and the size of such crystals in the direction transverse to the thinnest dimension of such elements is a multiple of such thinnest dimension.
3. A self supporting platinum-rhodium alloy catalyst consisting of a network formed of a plurality of relatively thin extended platinumrhodium alloy elements, wherein the elements are substantially composed of crystals whose size in the direction of the thinnest dimension of such elements is equal to such thinnest dimension and the size of such crystals in the direction transverse to the thinnest dimension of such elements is a multiple of such thinnest dimension.
Name Date Streicher Jan. 3, 1939 Number
Claims (1)
1. A WOVEN PLATINUM WIRE NETWORK SUITABLE FOR HIGH TEMPERATURE CATALYTIC REACTIONS THE WIRES OF WHICH ARE SUBSTANTIALLY COMPOSED OF CRYSTALS HAVING A CROSS-SECTION TRANSVERSE TO THE LONGITUDINAL AXIS OF THE WIRES IDENTICAL WITH THE TRANSVERSE CROSS-SECTION OF THE WIRES AND WHOSE SIZE IN THE DIRECTION OF THE LONGITUDINAL OXIS OF THE WIRES IS A MULTIPLE OF THE DIAMETER OF THE WIRES.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2685547X | 1951-01-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US2685547A true US2685547A (en) | 1954-08-03 |
Family
ID=7996721
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US268133A Expired - Lifetime US2685547A (en) | 1951-01-24 | 1952-01-24 | Platinum catalysts |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | US2685547A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2802925A (en) * | 1954-03-13 | 1957-08-13 | Degussa | Resistance thermometer |
| US2813811A (en) * | 1954-11-22 | 1957-11-19 | Gen Electric | High strength crystals |
| US3247254A (en) * | 1966-04-19 | Er saturated hydrocarbon |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2142660A (en) * | 1934-11-17 | 1939-01-03 | American Platinum Works | Platinum crucible |
-
1952
- 1952-01-24 US US268133A patent/US2685547A/en not_active Expired - Lifetime
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2142660A (en) * | 1934-11-17 | 1939-01-03 | American Platinum Works | Platinum crucible |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3247254A (en) * | 1966-04-19 | Er saturated hydrocarbon | ||
| US2802925A (en) * | 1954-03-13 | 1957-08-13 | Degussa | Resistance thermometer |
| US2813811A (en) * | 1954-11-22 | 1957-11-19 | Gen Electric | High strength crystals |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| KR101082363B1 (en) | Alloy | |
| EP1740733B1 (en) | Iron-chrome-aluminum alloy | |
| US3881966A (en) | Method for making aluminum alloy product | |
| US2391458A (en) | Spark gap electrode | |
| US2545438A (en) | Spark plug electrode | |
| US2816200A (en) | Electrical heating unit | |
| EP0098996A1 (en) | Zirconium alloy having superior corrosion resistance | |
| US2685547A (en) | Platinum catalysts | |
| EP3748026A1 (en) | Fe-cr alloy, method for producing same, and resistance heating element | |
| US2984894A (en) | Composite material | |
| US3143442A (en) | Copper-base alloys and method of heat treating them | |
| US4566915A (en) | Process for producing an age-hardening copper titanium alloy strip | |
| Clarebrough et al. | The energy stored in fatigued metals | |
| US2422477A (en) | Low-temperature heating element | |
| EP0387670A1 (en) | Ferritic-steel alloy | |
| US2780543A (en) | High resistivity alloy | |
| US3136634A (en) | Noble metal alloys having a high specific electric resistance | |
| US3915760A (en) | Process of producing a material having good spring properties | |
| US4384891A (en) | Metal alloy with high catalytic activity | |
| US2645575A (en) | Chromium-nickel titanium base alloys | |
| DE2339869A1 (en) | HIGH TEMPERATURE AND OXYDATION RESISTANT ALLOY | |
| US4507156A (en) | Creep resistant dispersion strengthened metals | |
| US3117894A (en) | Hardening spring by internal oxidation | |
| US3262779A (en) | Iridium-tungsten alloy products | |
| Zehetbauer et al. | Effect of Short-Range Order on the Mechanical Properties of α-Cu Al |