EP2310156A2 - Metal fibres for catalyst nonwovens - Google Patents

Metal fibres for catalyst nonwovens

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Publication number
EP2310156A2
EP2310156A2 EP09777543A EP09777543A EP2310156A2 EP 2310156 A2 EP2310156 A2 EP 2310156A2 EP 09777543 A EP09777543 A EP 09777543A EP 09777543 A EP09777543 A EP 09777543A EP 2310156 A2 EP2310156 A2 EP 2310156A2
Authority
EP
European Patent Office
Prior art keywords
boron
fibers
phosphorus
metal
weight
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.)
Withdrawn
Application number
EP09777543A
Other languages
German (de)
French (fr)
Inventor
Uwe Jantsch
David F. Lupton
Harald Manhardt
Stefan Vorberg
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Heraeus Deutschland GmbH and Co KG
Original Assignee
WC Heraus GmbH and Co KG
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by WC Heraus GmbH and Co KG filed Critical WC Heraus GmbH and Co KG
Publication of EP2310156A2 publication Critical patent/EP2310156A2/en
Withdrawn legal-status Critical Current

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    • 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
    • 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
    • B01J23/46—Ruthenium, rhodium, osmium or iridium
    • B01J23/464—Rhodium
    • 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
    • B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/56—Platinum group metals
    • B01J23/64—Platinum group metals with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/652—Chromium, molybdenum or tungsten
    • 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
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
    • 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
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
    • 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
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
    • B01J35/56—Foraminous structures having flow-through passages or channels, e.g. grids or three-dimensional monoliths
    • 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
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
    • B01J35/58—Fabrics or filaments
    • 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
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • 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
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/61—Surface area
    • B01J35/617—500-1000 m2/g
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/28—Phosphorising
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/06—Metallic powder characterised by the shape of the particles
    • B22F1/062—Fibrous particles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/002—Manufacture of articles essentially made from metallic fibres
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B21/00—Nitrogen; Compounds thereof
    • C01B21/20—Nitrogen oxides; Oxyacids of nitrogen; Salts thereof
    • C01B21/24—Nitric oxide (NO)
    • C01B21/26—Preparation by catalytic or non-catalytic oxidation of ammonia
    • C01B21/265—Preparation by catalytic or non-catalytic oxidation of ammonia characterised by the catalyst
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
    • C01C3/00—Cyanogen; Compounds thereof
    • C01C3/02—Preparation, separation or purification of hydrogen cyanide
    • C01C3/0208—Preparation in gaseous phase
    • C01C3/0212—Preparation in gaseous phase from hydrocarbons and ammonia in the presence of oxygen, e.g. the Andrussow-process
    • C01C3/0216—Preparation in gaseous phase from hydrocarbons and ammonia in the presence of oxygen, e.g. the Andrussow-process characterised by the catalyst used
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C5/00—Alloys based on noble metals
    • C22C5/04—Alloys based on a platinum group metal
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
    • F01N3/28—Construction of catalytic reactors
    • F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
    • F01N3/2807—Metal other than sintered metal
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
    • F01N3/28—Construction of catalytic reactors
    • F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
    • F01N3/2835—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support fibrous

Definitions

  • the present invention relates to catalyst structures for the production of nitric acid and hydrocyanic acid and to the production of catalysts suitable metal fibers based on precious metals, nets and webs produced therefrom and to processes for producing such fibers, nonwovens and nets.
  • DE 199 45 742 C1 discloses a metal fiber catalyst body whose metal fibers are produced by melt extraction. From the fibers, using textile techniques i.a. Fiber fleece created. The catalyst material platinum, palladium rhodium is contained in the fibers or present as additional fibers in the fabric.
  • DE 100 00 097 A1 discloses melt extraction processes for the production of metal fibers from thin fibers with diameters of less than 100 ⁇ m with melt bath temperatures of more than 1500 ° C.
  • the object of the present invention is to produce fibers, nets or fleeces based on precious metals.
  • the procedure should be as simple as possible.
  • the catalysts are designed to maintain high efficiency in the long term.
  • the melting point of a metal before fiber processing by means of boron or phosphorus is drastically reduced and the boron or phosphorus after the production of fibers or nonwovens or nets made of fibers largely removed again.
  • the melting point of a precious metal-based metal in particular based on the platinum group metals platinum, palladium, rhodium, ruthenium and iridium and optionally additional alloying elements of up to 30 wt .-% of the metals nickel, cobalt, gold, rhenium, molybdenum and tungsten lowered significantly by boron or phosphorus, in particular by at least 400 0 C, preferably by at least 500 0 C.
  • boron or phosphorus in particular by at least 400 0 C, preferably by at least 500 0 C.
  • Phosphorus generated Such eutectic mixtures are generally between 1 to 5 wt .-% boron or phosphorus based on the metal to be processed.
  • the present invention is also still feasible outside the eutectic mixtures. Below 0.5% by weight of boron or phosphorus, however, the effect becomes unusable because the wide melting interval of the alloy leads to considerable segregation. If the proportion of boron or phosphorus is too high, on the one hand boron or phosphorus is unnecessarily burned, which leads to the increased consumption as a further disadvantage that the expense of removing these elements likewise increases unnecessarily.
  • the lowering of the melting point according to the invention is particularly pronounced with platinum, iridium and their alloys.
  • the use of boron to lower the melting point is preferred, since with the use of phosphorus generally higher safety precautions must be taken.
  • fibers with a diameter between 10 and 200 .mu.m, in particular between 50 and 100 microns are available.
  • the drawing of fibers from the melt, in particular by means of melt extraction according to the invention by lowering the melting temperature by means of boron or phosphor energy-saving and device conserving in particular compared to the effort without melting point reduction or compared to the cost of producing
  • the fibers can also be produced in a wire casting process according to DE 197 57 093 A1 or in a melt spinning process according to DE 31 36 303 A1.
  • nonwovens or nets are largely removed again.
  • the oxidation of the boron or phosphorus is not carried out under an air atmosphere, but milder conditions such.
  • the melting point of 1770 0 C can be reduced to 790 0 C. This facilitates the production of Pt alloy fibers, eg PtRh ⁇ , by the melt extraction process.
  • the melting point of Pd is reduced in a similar manner by alloying of about 3 wt .-% B of 1555 ° C at 1065 0 C.
  • the boron-alloyed PtRh5 fibers are at a temperature (eg. B. 750 0 C) presintered just below the eutectic. During presintering, the boron oxidizes and, for the most part, the resulting boron oxide liquefies or vaporizes. Also, first sintered connections are created between the fibers. By a short-term (a few minutes) sintering treatment at a temperature in the range 1200 ° C-1400 ° C (eg with the flame), the nonwoven sinters firmly together. Any remaining boric oxide traces can be removed by rinsing in warm water.
  • a temperature eg. B. 750 0 C
  • nonwovens can be produced from palladium alloys.
  • the eutectic of the Pd-B system is significantly higher at 1065 ° C and the melting point of the Pd at 1555 ° C is significantly lower than platinum, greater care is required in setting the temperatures for pre-sintering and sintering.
  • the suitable temperatures can be easily determined by simple aging experiments and subsequent metallographic ground investigations.
  • the prepared ingots of the B-containing PtRh5 alloy were melted in a zirconium oxide crucible in a melt extraction device (see description in DE 199 45 742 C1, column 2, from line 40) under an argon protective gas atmosphere, wherein the temperature of the molten bath in the range 820-860 0 C was held.
  • the fibers were scattered on a flat base made of aluminum oxide with dimensions of 400 mm ⁇ 800 mm until the basis weight of the fibers reached 1500 g / m 2 .
  • the thus-laid nonwoven fabric was placed on the support in a chamber furnace under air atmosphere, heated to 750 0 C and held at this temperature for 5 hours.
  • the boron diffused from the fibers, oxidized on the surface of PtRh alloy and formed boron oxide, which is liquid at this temperature (melting point 450 0 C).
  • the pre-sintered fleece backing was removed from the oven and cooled to room temperature. Upon cooling, the boron oxide was allowed to dissolve in warm water causing the web to dislodge from the pad. Due to the presintering, sufficient mechanical strength had already been created to suspend the nonwoven with platinum wires. At this stage, however, the fleece was still very fragile and had to be handled with great care.
  • the web was heated to white heat (estimated at about 1200 0 C) and held for 2-3 minutes. After this treatment, the strength had increased significantly. The strength was determined by firmly tensioning a nonwoven blank (diameter 95 mm) around the circumference and pressing in a steel hemisphere (diameter 40 mm) until the nonwoven was torn. The maximum force reached was measured at 95 N. In comparison, 2 nonwovens made by drawing and sintering drawn PtRh5 wires and also having a basis weight of 1500 g / mm 2 were tested. The first nonwoven was oven sintered at 1640 ° C. for 10 minutes and had a compressive strength of 10 N.
  • the second nonwoven fabric was sintered at 1350 ° C. for 12 hours and had a compressive strength of 85 N.
  • the nonwoven according to the invention could be handled without difficulty.
  • the boron content of the PtRh5 alloy had depleted to ⁇ 0.001%.
  • the nonwoven had a porosity of 91%.
  • the pressure losses of the nonwovens were by a factor of 1.4 higher than in the nets and the concentrations of nitrous oxide in the product gas in the nonwovens and nets were comparable.
  • the oxidation efficiency of the webs was 96.2% under the conditions tested and remained at that level throughout the test time of 126.0 hours.
  • the oxidation efficiency of the nets was 96.0% at the beginning of the test and dropped to 95.5% during the test period.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • General Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Inorganic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • General Health & Medical Sciences (AREA)
  • Nanotechnology (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Metallurgy (AREA)
  • Catalysts (AREA)
  • Inorganic Fibers (AREA)
  • Powder Metallurgy (AREA)
  • Nonwoven Fabrics (AREA)

Abstract

A metal fibre based on one or more elements from the group consisting of platinum, palladium, rhodium, ruthenium and iridium together with from 0 to 30% by weight of one or more additional alloying elements from the group consisting of nickel, cobalt, gold, rhenium, molybdenum and tungsten has, according to the invention, from 1 to 500 ppm by weight of boron or phosphorus. A nonwoven or mesh according to the invention, in particular for producing nitrogen oxide or for producing hydrocyanic acid, comprises such fibres. To produce fibres based on noble metals together with up to 30% by weight of additional alloying metals, the melting point of the metal is reduced by at least 400°C by addition of boron or phosphorus as alloying constituent before drawing of the fibres from a melt and the boron or the phosphorus is removed again from the fibres.

Description

Metallfasern für Katalysatorvliese Metal fibers for catalyst nonwovens
Die vorliegende Erfindung betrifft Katalysatorstrukturen für die Herstellung von Salpetersäure und Blausäure und zur Herstellung von Katalysatoren geeignete Metallfasern auf Basis von Edelmetallen, daraus hergestellte Netze und Vliese sowie Verfahren zur Herstellung derartiger Fasern, Vliese und Netze.The present invention relates to catalyst structures for the production of nitric acid and hydrocyanic acid and to the production of catalysts suitable metal fibers based on precious metals, nets and webs produced therefrom and to processes for producing such fibers, nonwovens and nets.
DE 199 45 742 C1 offenbart einen Metallfaser-Katalysatorkörper dessen Metallfasern durch Schmelzextraktion hergestellt werden. Aus den Fasern werden mit textilen Techniken u.a. Faservliese erstellt. Das Katalysatormaterial Platin, Palladium Rhodium ist in den Fasern enthalten oder als zusätzliche Fasern in dem Gewebe vorhanden.DE 199 45 742 C1 discloses a metal fiber catalyst body whose metal fibers are produced by melt extraction. From the fibers, using textile techniques i.a. Fiber fleece created. The catalyst material platinum, palladium rhodium is contained in the fibers or present as additional fibers in the fabric.
DE 100 00 097 A1 offenbart Schmelzextraktionsverfahren zur Metallfaserherstellung von dünnen Fasern mit Durchmessern unterhalb von 100 μm mit Schmelzbadtemperaturen bis über 15000C.DE 100 00 097 A1 discloses melt extraction processes for the production of metal fibers from thin fibers with diameters of less than 100 μm with melt bath temperatures of more than 1500 ° C.
DE 197 12 625 A1 beschreibt ein Verfahren, bei dem u.a. metallische Fasern durch die Maschen einer Streuwalze auf eine bewegte Unterlage abgelegt und an Kreuzungspunkten miteinander verbunden werden.DE 197 12 625 A1 describes a method in which u.a. metallic fibers are deposited by the meshes of a scattering roller on a moving surface and connected to each other at crossing points.
Diese Verfahren erscheinen zur Herstellung von Metallfasern und daraus erzeugten Netzen oder Vliesen für Metalle mit hohem Schmelzpunkt ungeeignet oder zumindest nur schwer realisierbar.These processes appear to be unsuitable or at least difficult to realize for producing metal fibers and nets or webs made therefrom for high melting point metals.
DE 100 40 591 C1 lehrt Platin, Iridium, Rhodium und Ruthenium u.a. mit Bor und Phosphor zu legieren.DE 100 40 591 C1 teaches platinum, iridium, rhodium and ruthenium u.a. to alloy with boron and phosphorus.
Die Effizienz bekannter Katalysatoren, insbesondere Platin-Rhodium Katalysatoren sinkt im Laufe der Zeit.The efficiency of known catalysts, in particular platinum-rhodium catalysts decreases over time.
BESTATIGUNGSKOPIE Die Aufgabe der vorliegenden Erfindung besteht darin, Fasern, Netze oder Vliese auf Edelmetallbasis zu erzeugen. Das Verfahren soll möglichst einfach sein. Die Katalysatoren sollen eine hohe Effizienz langfristig aufrecht halten.BESTATIGUNGSKOPIE The object of the present invention is to produce fibers, nets or fleeces based on precious metals. The procedure should be as simple as possible. The catalysts are designed to maintain high efficiency in the long term.
Zur Lösung der Aufgabe wird der Schmelzpunkt eines Metalls vor der Faserverarbeitung mittels Bor oder Phosphor drastisch gesenkt und das Bor oder Phosphor nach der Herstellung von Fasern oder aus Fasern hergestellten Vliesen oder Netzen weitgehend wieder entfernt.To solve the problem, the melting point of a metal before fiber processing by means of boron or phosphorus is drastically reduced and the boron or phosphorus after the production of fibers or nonwovens or nets made of fibers largely removed again.
Die Lösung der Aufgabe erfolgt mit den Merkmalen der unabhängigen Ansprüche. Die abhängigen Ansprüche beschreiben bevorzugte Ausführungsformen.The object is achieved by the features of the independent claims. The dependent claims describe preferred embodiments.
Es wird angenommen, dass beim Entfernen des Bors bzw. Phosphors die Oberflächenrauhigkeit der Fasern vergrößert wird und einhergehend mit dieser zusätzlichen Porosität die Effektivität des Katalysators erhöht wird. Weiterhin wird vermutet, dass Bor oder Phosphor die Bildung von Oxiden behindert, die katalytisch unwirksam sind und den Zutritt zum Katalysator versperren.It is believed that as the boron or phosphorus is removed, the surface roughness of the fibers is increased and, along with this additional porosity, the effectiveness of the catalyst is increased. Furthermore, it is believed that boron or phosphorus hinders the formation of oxides that are catalytically inactive and block access to the catalyst.
Erfindungsgemäß wird der Schmelzpunkt eines Metalls auf Edelmetallbasis, insbesondere auf Basis der Platingruppenmetalle Platin, Palladium, Rhodium, Ruthenium und Iridium und ggf. zusätzlicher Legierungselemente von insgesamt bis zu 30 Gew.-% der Metalle Nickel, Kobalt, Gold, Rhenium, Molybdän und Wolfram mittels Bor oder Phosphor erheblich abgesenkt, insbesondere um mindestens 400 0C, vorzugsweise um mindestens 500 0C. Hierzu werden vorzugsweise eutektische Zusammensetzungen mit Bor oderAccording to the invention, the melting point of a precious metal-based metal, in particular based on the platinum group metals platinum, palladium, rhodium, ruthenium and iridium and optionally additional alloying elements of up to 30 wt .-% of the metals nickel, cobalt, gold, rhenium, molybdenum and tungsten lowered significantly by boron or phosphorus, in particular by at least 400 0 C, preferably by at least 500 0 C. These are preferably eutectic compositions with boron or
Phosphor erzeugt. Derartige eutektische Gemische liegen im Allgemeinen zwischen 1 bis 5 Gew.-% Bor oder Phosphor bezogen auf das zu verarbeitende Metall.Phosphorus generated. Such eutectic mixtures are generally between 1 to 5 wt .-% boron or phosphorus based on the metal to be processed.
Die vorliegende Erfindung ist außerhalb der eutektischen Mischungen auch noch durchführbar. Unterhalb von 0,5 Gew.-% an Bor oder Phosphor wird der Effekt jedoch unbrauchbar, weil das breite Schmelzintervall der Legierung zu erheblichen Entmischungen führt. Bei zu hohem Bor- oder Phosphor-Anteil wird einerseits unnötig Bor oder Phosphor verbrannt, wozu sich zu dem erhöhten Verbrauch als weiterer Nachteil ergibt, dass der Aufwand für das Entfernen dieser Elemente ebenfalls unnütz steigt. Deshalb sind bei einer Konzentration oberhalb von 10 Gew.-% mit steigendem Bor- oder Phoshpor-Gehalt selbst bei Zusammensetzungen, die bis dahin noch kein Eutektikum erreicht haben, die Nachteile in Form des hohen Verbrauchs an Bor oder Phosphor und der steigende Aufwand zu deren Entfernung in Relation zu dem immer geringer werdenden Vorteil der Schmelzpunkterniedrigung zu sehen.The present invention is also still feasible outside the eutectic mixtures. Below 0.5% by weight of boron or phosphorus, however, the effect becomes unusable because the wide melting interval of the alloy leads to considerable segregation. If the proportion of boron or phosphorus is too high, on the one hand boron or phosphorus is unnecessarily burned, which leads to the increased consumption as a further disadvantage that the expense of removing these elements likewise increases unnecessarily. Therefore, at a concentration above 10 wt .-% with increasing boron or Phoshpor content even with compositions that hitherto no eutectic have achieved to see the disadvantages in the form of high consumption of boron or phosphorus and the increasing effort to remove them in relation to the ever decreasing advantage of melting point depression.
Die erfindungsgemäße Schmelzpunkterniedrigung erfolgt besonders ausgeprägt bei Platin, Iridium und deren Legierungen. Die Verwendung von Bor zur Schmelzpunkterniedrigung ist bevorzugt, da bei Anwendung von Phosphor im Allgemeinen höhere Sicherheitsvorkehrungen getroffen werden müssen.The lowering of the melting point according to the invention is particularly pronounced with platinum, iridium and their alloys. The use of boron to lower the melting point is preferred, since with the use of phosphorus generally higher safety precautions must be taken.
Erfindungsgemäß sind Fasern mit einem Durchmesser zwischen 10 und 200 μm, insbesondere zwischen 50 und 100 μm erhältlich. Das Ziehen von Fasern aus der Schmelze, insbesondere mittels Schmelzextraktion ist erfindungsgemäß durch die Absenkung der Schmelztemperatur mittels Bor oder Phosphor energiesparend und geräteschonend insbesondere im Vergleich zum Aufwand ohne Schmelzpunkterniedrigung oder im Vergleich zum Aufwand für die Herstellung vonAccording to the invention fibers with a diameter between 10 and 200 .mu.m, in particular between 50 and 100 microns are available. The drawing of fibers from the melt, in particular by means of melt extraction according to the invention by lowering the melting temperature by means of boron or phosphor energy-saving and device conserving in particular compared to the effort without melting point reduction or compared to the cost of producing
Drahtabschnitten. Man kann mit dem erfindungsgemäßen Absenken des Schmelzpunktes die Fasern auch in einem Drahtgießverfahren gemäß DE 197 57 093 A1 oder in einem Schmelzspinnverfahren gemäß DE 31 36 303 A1 herstellen.Wire sections. With the lowering of the melting point according to the invention, the fibers can also be produced in a wire casting process according to DE 197 57 093 A1 or in a melt spinning process according to DE 31 36 303 A1.
Erfindungsgemäß wird neben der erleichterten Faserherstellung durch Ziehen aus der Schmelze, insbesondere mittels Schmelzextraktion auch die erforderliche Sintertemperatur und Zeit zur Herstellung von Netzen oder Vliesen aus den Fasern reduziert, ohne die katalytischen und mechanischen Eigenschaften der Vliese zu beeinträchtigen, da sowohl Bor als auch Phosphor vor der bestimmungsgemäßen Anwendung der Fasern, Vliese oder Netze wieder weitgehend entfernt werden. DieAccording to the invention, in addition to the facilitated fiber production by drawing from the melt, in particular by melt extraction and the required sintering temperature and time for the production of nets or webs from the fibers reduced without affecting the catalytic and mechanical properties of the nonwovens, as both boron and phosphorus before the intended use of the fibers, nonwovens or nets are largely removed again. The
Entfernung von Bor und Phosphor erfolgt teilweise während des Ziehens der Fasern und bei der Sinterung der Fasern zu Netzen oder Vliesen. Ein zu hoher Restgehalt an Bor oder Phosphor beeinträchtigt die gewünschten Eigenschaften für die Anwendung als Katalysator. Es hat sich besonders bewährt, das Bor oder den Phosphor nach einer Sinterung der Fasern zu Netzen oder Vliesen das Produkt wenige Minuten auf Weißglut zu erhitzen. Bei einem derartigen Behandlungsschritt steigt die Festigkeit des Materials unter Verringerung des Bor- oder Phosphorgehaltes. Es wird angenommen, dass Bor oder Phosphor oberhalb der üblichen Verunreinigungen durch diese Elemente verbleiben, insbesondere zwischen 1 und 500 ppm. Insbesondere bei einer Reduzierung des Bors auf 1 bis 20 Gew.-% oder des Phosphors auf 5 bis 20 Gew.-% sind keine negativen Auswirkungen dieser Elemente gegen die katalytische Wirkung und mechanischeRemoval of boron and phosphorus occurs in part as the fibers are drawn and sintered into nets or nonwovens. Excessive residual boron or phosphorus impairs the desired properties for use as a catalyst. It has proven particularly useful to heat the product for a few minutes to incandescent after sintering the fibers into nets or nonwovens. In such a treatment step, the strength of the material increases while reducing the boron or phosphorus content. It is believed that boron or phosphorus will remain above the usual impurities by these elements, especially between 1 and 500 ppm. In particular, with a reduction of the boron to 1 to 20 wt .-% or of the phosphorus to 5 to 20 wt .-% are not negative Effects of these elements against the catalytic action and mechanical
Stabilität der erfindungsgemäß hergestellten Fasern, Netze oder Vliese zu erwarten.Stability of the fibers, nets or nonwovens according to the invention to be expected.
Bei Anwendung unedler Legierungselemente oder oxydationsempfindlicher Platingruppenmetalle wie Iridium und Ruthenium erfolgt die Oxydation des Bors bzw. Phosphors nicht unter Luftatmosphäre, sondern milderen Bedingungen wie z. B. einem H2/H2O enthaltenden oxidierenden Gasgemisch. Diese schonende Methode ist insbesondere für die Vorsinterung vorteilhaft, wenn oxydationsempfindliche Metalle in der Legierung enthalten sind.When using base alloying elements or oxidation-sensitive platinum group metals such as iridium and ruthenium, the oxidation of the boron or phosphorus is not carried out under an air atmosphere, but milder conditions such. B. a H 2 / H 2 O containing oxidizing gas mixture. This gentle method is particularly advantageous for the pre-sintering, if oxidation-sensitive metals are included in the alloy.
Im Folgenden wird die vorliegende Erfindung anhand von Beispielen verdeutlicht.In the following, the present invention is illustrated by means of examples.
Durch die Zugabe von etwa 2 Gew.-% Bor zu Platin lässt sich der Schmelzpunkt von 17700C auf 7900C reduzieren. Dies erleichtert die Herstellung von Fasern aus Pt- Legierungen, z.B. PtRhδ durch das Verfahren der Schmelzextraktion. Der Schmelzpunkt von Pd wird auf ähnliche Weise durch das Zulegieren von etwa 3 Gew.-% B von 1555°C auf 10650C reduziert.By adding about 2 wt .-% boron to platinum, the melting point of 1770 0 C can be reduced to 790 0 C. This facilitates the production of Pt alloy fibers, eg PtRhδ, by the melt extraction process. The melting point of Pd is reduced in a similar manner by alloying of about 3 wt .-% B of 1555 ° C at 1065 0 C.
Die mit Bor legierten PtRh5-Fasern werden bei einer Temperatur (z. B. 7500C) knapp unterhalb des Eutektikums vorgesintert. Beim Vorsintern oxidiert das Bor, und zum Großteil verflüssigt oder verdampft das entstehende Boroxid. Ebenfalls werden erste Sinterverbindungen zwischen den Fasern erzeugt. Durch eine kurzzeitige (wenige Minuten) Sinter-Behandlung bei einer Temperatur im Bereich 1200°C-1400°C (z.B. mit der Flamme) sintert das Vlies fest zusammen. Eventuell verbleibende Boroxid-Spuren können durch spülen in warmem Wasser beseitigt werden.The boron-alloyed PtRh5 fibers are at a temperature (eg. B. 750 0 C) presintered just below the eutectic. During presintering, the boron oxidizes and, for the most part, the resulting boron oxide liquefies or vaporizes. Also, first sintered connections are created between the fibers. By a short-term (a few minutes) sintering treatment at a temperature in the range 1200 ° C-1400 ° C (eg with the flame), the nonwoven sinters firmly together. Any remaining boric oxide traces can be removed by rinsing in warm water.
Auf analoge Weise lassen sich Vliese aus Palladiumlegierungen herstellen. Da jedoch das Eutektikum des Pd-B-Systems mit 1065°C deutlich höher bzw. der Schmelzpunkt des Pd mit 1555°C deutlich niedriger liegt als beim Platin, ist bei der Einstellung der Temperaturen für das Vorsintern und das Sintern größere Sorgfalt erforderlich. Die geeigneten Temperaturen lassen sich jedoch durch einfache Auslagerungsversuche und anschließende metallographische Schliffuntersuchungen leicht ermitteln. Ausführungsbeispiel:In a similar manner, nonwovens can be produced from palladium alloys. However, since the eutectic of the Pd-B system is significantly higher at 1065 ° C and the melting point of the Pd at 1555 ° C is significantly lower than platinum, greater care is required in setting the temperatures for pre-sintering and sintering. However, the suitable temperatures can be easily determined by simple aging experiments and subsequent metallographic ground investigations. Embodiment:
5 kg einer auf konventionelle Weise vorgeschmolzenen Legierung aus PtRh5 wurden nach dem Abgießen zu einem Stab mit einem Durchmesser von 10 mm gewalzt und in Längen von etwa 30 mm geschnitten. Die Abschnitte wurden anschließend in einem Zirkoniumoxidtiegel unter Argonabdeckung langsam induktiv erhitzt, wobei 2,1 Gew.-% Borgranulat - entsprechend dem Pt-B-Eutektikum - der Schmelze zugegeben wurden. Nach kurzzeitigem Aufschmelzen wurde eine Erwärmung der Schmelze über 10000C sorgfältig vermieden, um die Gefahr einer Reaktion zwischen dem Bor und dem Zirkoniumoxid des Tiegels auf ein Minimum zu reduzieren. Die so hergestellte Legierung wurde in Kupferkokillen zu ca. 20 mm x 20 mm x 120 mm Barren gegossen.5 kg of a conventionally pre-melted PtRh5 alloy was rolled after casting into a 10 mm diameter rod and cut into lengths of about 30 mm. The sections were then slowly inductively heated in a zirconia crucible under argon cover, with 2.1% by weight of boron granules - corresponding to the Pt-B eutectic - added to the melt. After brief melting, heating of the melt above 1000 ° C. was carefully avoided in order to minimize the risk of a reaction between the boron and the zirconium oxide of the crucible. The alloy produced in this way was cast in copper molds to approximately 20 mm × 20 mm × 120 mm ingots.
Die vorbereiteten Barren aus der B-haltigen PtRh5-Legierung wurden in einem Zirkoniumoxidtiegel in einer Schmelzextraktionsvorrichtung (s. Beschreibung in DE 199 45 742 C1 , Spalte 2, ab Zeile 40) unter einer Argon-Schutzgasatmosphäre aufgeschmolzen, wobei die Temperatur des Schmelzbads im Bereich 820-8600C gehalten wurde.The prepared ingots of the B-containing PtRh5 alloy were melted in a zirconium oxide crucible in a melt extraction device (see description in DE 199 45 742 C1, column 2, from line 40) under an argon protective gas atmosphere, wherein the temperature of the molten bath in the range 820-860 0 C was held.
Vergleichsversuche zur Herstellung von Fasern aus der Legierung PtRhδ ohne Bor waren an der hohen Schmelztemperatur der Legierung (Liquidus ca. 18200C) und die dadurch verursachte Beschädigung des Schmelztiegels gescheitert. Der Extraktionsprozess wurde anhand von Vorversuchen so eingestellt, dass aus der PtRh5-B-Legierung 2,6 kg Fasern mit einem Durchmesser von 50-60 μm und einer mittleren Länge von 5 mm erzeugt wurden.Comparative experiments for the production of fibers from the alloy without boron PtRhδ had failed and the damage caused thereby of the crucible at the high melting temperature of the alloy (C Liquidus 1820 0). The extraction process was pre-set to produce 2.6 kg of 50-60 μm diameter fibers with a mean length of 5 mm from the PtRh5-B alloy.
Analog dem in DE 197 12 625 A1 beschriebenen Verfahren wurden die Fasern auf eine ebene Unterlage aus Aluminiumoxid mit den Abmessungen 400 mm x 800 mm gestreut, bis das Flächengewicht der Fasern 1500 g/m2 erreichte.Analogously to the process described in DE 197 12 625 A1, the fibers were scattered on a flat base made of aluminum oxide with dimensions of 400 mm × 800 mm until the basis weight of the fibers reached 1500 g / m 2 .
Das so gelegte Vlies wurde auf der Unterlage in einen Kammerofen unter Luftatmosphäre eingeführt, auf 7500C erwärmt und 5 Stunden bei dieser Temperatur gehalten. Das Bor diffundierte aus den Fasern, oxidierte an der Oberfläche der PtRh-Legierung und bildete Boroxid, das bei dieser Temperatur flüssig ist (Schmelzpunkt 4500C). Die Unterlage mit dem vorgesinterten Vlies wurde aus dem Ofen entfernt und auf Raumtemperatur abgekühlt. Nach dem Abkühlen ließ sich das Boroxid in warmem Wasser auflösen, wodurch das Vlies sich von der Unterlage löste. Durch die Vorsinterung war bereits eine ausreichende mechanische Festigkeit entstanden, um das Vlies mit Platindrähten aufzuhängen. In diesem Stadium war jedoch das Vlies noch sehr zerbrechlich und musste mit großer Vorsicht behandelt werden. Mit einer Wasserstoff-Sauerstoff-Flamme wurde das Vlies auf Weißglut (schätzungsweise etwa 12000C) erwärmt und 2-3 Minuten gehalten. Nach dieser Behandlung war die Festigkeit deutlich angestiegen. Die Festigkeit wurde ermittelt, indem eine Vliesronde (Durchmesser 95 mm) am Umfang fest gespannt und eine Stahlhalbkugel (Durchmesser 40 mm) bis zum Zerreißen des Vlieses eingedrückt wurde. Die maximal erreichte Kraft wurde mit 95 N gemessen. Im Vergleich dazu wurden 2 Vliese getestet, die durch Legen und Sintern aus gezogenen PtRh5-Drähten angefertigt wurden und ebenfalls ein Flächengewicht von 1500 g/mm2 hatten. Das erste Vlies wurde 10 min bei 16400C im Ofen gesintert und wies eine Druckfestigkeit von 10 N auf. Das zweite Vlies wurde 12 h bei 13500C gesintert und hatte eine Druckfestigkeit von 85 N. Das erfindungsgemäße Vlies konnte problemlos gehandhabt werden. Der Borgehalt der PtRh5-Legierung hatte sich auf < 0,001 % abgereichert. Das Vlies wies eine Porosität von 91 % auf.The thus-laid nonwoven fabric was placed on the support in a chamber furnace under air atmosphere, heated to 750 0 C and held at this temperature for 5 hours. The boron diffused from the fibers, oxidized on the surface of PtRh alloy and formed boron oxide, which is liquid at this temperature (melting point 450 0 C). The pre-sintered fleece backing was removed from the oven and cooled to room temperature. Upon cooling, the boron oxide was allowed to dissolve in warm water causing the web to dislodge from the pad. Due to the presintering, sufficient mechanical strength had already been created to suspend the nonwoven with platinum wires. At this stage, however, the fleece was still very fragile and had to be handled with great care. With a hydrogen-oxygen flame, the web was heated to white heat (estimated at about 1200 0 C) and held for 2-3 minutes. After this treatment, the strength had increased significantly. The strength was determined by firmly tensioning a nonwoven blank (diameter 95 mm) around the circumference and pressing in a steel hemisphere (diameter 40 mm) until the nonwoven was torn. The maximum force reached was measured at 95 N. In comparison, 2 nonwovens made by drawing and sintering drawn PtRh5 wires and also having a basis weight of 1500 g / mm 2 were tested. The first nonwoven was oven sintered at 1640 ° C. for 10 minutes and had a compressive strength of 10 N. The second nonwoven fabric was sintered at 1350 ° C. for 12 hours and had a compressive strength of 85 N. The nonwoven according to the invention could be handled without difficulty. The boron content of the PtRh5 alloy had depleted to <0.001%. The nonwoven had a porosity of 91%.
Aus dem Vlies mit 1500 g /m2 Flächengewicht wurden 4 Ronden mit Durchmessern von jeweils 62 mm ausgestanzt. In einem Testreaktor zur Oxidation von Ammoniak zu Stickoxid wurden die Ronden unter einer Belastung 22,4 Tonnen Stickstoff proFrom the nonwoven with 1500 g / m 2 basis weight 4 blanks were punched out with diameters of 62 mm each. In a test reactor for the oxidation of ammonia to nitric oxide, the blanks under a load 22.4 tons of nitrogen per
Quadratmeter und Tag (t N/m2/d), einem Druck von 3,5 bar und einer Temperatur von 86O0C erprobt. Zum Vergleich wurden in einem parallelen Reaktor 10 übliche Katalysatornetze, die durch das Wirken von 76 μm-Drähten aus PtRh5 hergestellt wurden, jeweils mit einem Flächengewicht von 600 g/m2, getestet.Square meters and day (t N / m 2 / d), a pressure of 3.5 bar and a temperature of 86O 0 C tested. For comparison, in a parallel reactor 10 conventional catalyst networks, which were prepared by the action of 76 .mu.m wires of PtRh5, each with a basis weight of 600 g / m 2 tested.
Die Druckverluste der Vliese waren um den Faktor 1 ,4 höher als bei den Netzen, die Konzentrationen an Lachgas im Produktgas bei den Vliesen und den Netzen vergleichbar. Die Oxidationseffizienz der Vliese lagen unter den getesteten Bedingungen bei 96,2 % und blieb während der gesamten Testzeit von 126,0 Stunden auf diesem Niveau. Die Oxidationseffizienz der Netze betrug zu Beginn des Tests 96,0% und sank im Laufe der Testzeit auf 95,5% ab. The pressure losses of the nonwovens were by a factor of 1.4 higher than in the nets and the concentrations of nitrous oxide in the product gas in the nonwovens and nets were comparable. The oxidation efficiency of the webs was 96.2% under the conditions tested and remained at that level throughout the test time of 126.0 hours. The oxidation efficiency of the nets was 96.0% at the beginning of the test and dropped to 95.5% during the test period.

Claims

Patentansprüche claims
1. Metallfaser auf der Basis eines oder mehrerer Elemente aus der Gruppe Platin,1. Metal fiber based on one or more platinum group elements,
Palladium, Rhodium, Ruthenium oder Iridium mit 0 bis 30 Gew.-% eines oder mehrerer zusätzlicher Legierungselemente aus der Gruppe Nickel, Kobalt, Gold, Rhenium, Molybdän und Wolfram, dadurch gekennzeichnet, dass die Metallfaser 1 bis 500 Gew.-ppm Bor oder Phosphor aufweist.Palladium, rhodium, ruthenium or iridium with 0 to 30 wt .-% of one or more additional alloying elements from the group consisting of nickel, cobalt, gold, rhenium, molybdenum and tungsten, characterized in that the metal fiber 1 to 500 ppm by weight of boron or Having phosphorus.
2. Vlies oder Netz bestehend aus Fasern nach Anspruch 1.2. fleece or network consisting of fibers according to claim 1.
3. Verwendung von Fasern nach Anspruch 1 , insbesondere als Netz oder Vlies gemäß Anspruch 5 zur Herstellung von Stickoxid oder zur Herstellung von Blausäure.3. Use of fibers according to claim 1, in particular as a network or nonwoven according to claim 5 for the production of nitrogen oxide or for the production of hydrogen cyanide.
4. Verfahren zur Herstellung von Fasern auf Edelmetallbasis mit bis zu 30 Gew.- % zusätzlichen Legierungsmetallen durch Ziehen der Fasern aus einer Schmelze, dadurch gekennzeichnet, dass der Schmelzpunkt des Metalls vor dem Ziehen der Fasern durch Zulegieren von Bor oder Phosphor um mindestens 400 0C abgesenkt wird und aus den Fasern das Bor oder der Phosphor wieder entfernt wird.4. A process for the production of noble metal-based fibers with up to 30% by weight of additional alloying metals by drawing the fibers from a melt, characterized in that the melting point of the metal prior to pulling the fibers by addition of boron or phosphorus by at least 400 0th C is lowered and the boron or phosphorus is removed from the fibers again.
5. Verfahren nach Anspruch 4, dadurch gekennzeichnet, dass das Bor oder der Phosphor unter Schutzgasatmosphäre mit dem Metall gemischt werden.5. The method according to claim 4, characterized in that the boron or phosphorus are mixed under a protective gas atmosphere with the metal.
6. Verfahren nach Anspruch 4 oder 5, dadurch gekennzeichnet, dass die Fasern zu einem Vlies oder Netz gesintert werden.6. The method according to claim 4 or 5, characterized in that the fibers are sintered into a web or web.
7. Verfahren nach einem der Ansprüche 4 bis 6, dadurch gekennzeichnet, dass das Bor oder der Phosphor thermisch als Oxid entfernt wird. 7. The method according to any one of claims 4 to 6, characterized in that the boron or phosphorus is removed thermally as oxide.
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