WO2005014474A2 - Method for producing crystalline pyrophosphates, use of said compounds as catalysts or as additives for membranes, in particular for membranes of fuel cells - Google Patents

Method for producing crystalline pyrophosphates, use of said compounds as catalysts or as additives for membranes, in particular for membranes of fuel cells Download PDF

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WO2005014474A2
WO2005014474A2 PCT/EP2004/008857 EP2004008857W WO2005014474A2 WO 2005014474 A2 WO2005014474 A2 WO 2005014474A2 EP 2004008857 W EP2004008857 W EP 2004008857W WO 2005014474 A2 WO2005014474 A2 WO 2005014474A2
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range
formula
crystalline
particle size
acid
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French (fr)
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WO2005014474A3 (en
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Gordon Calundann
Brian Benicewicz
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Pemeas Gmbh
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/38—Condensed phosphates
    • C01B25/42—Pyrophosphates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/14—Dynamic membranes
    • B01D69/141—Heterogeneous membranes, e.g. containing dispersed material; Mixed matrix membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/58—Other polymers having nitrogen in the main chain, with or without oxygen or carbon only
    • B01D71/62—Polycondensates having nitrogen-containing heterocyclic rings in the main chain
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
    • H01M8/1018—Polymeric electrolyte materials
    • H01M8/102—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer
    • H01M8/103—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer having nitrogen, e.g. sulfonated polybenzimidazoles [S-PBI], polybenzimidazoles with phosphoric acid, sulfonated polyamides [S-PA] or sulfonated polyphosphazenes [S-PPh]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
    • H01M8/1018—Polymeric electrolyte materials
    • H01M8/1041—Polymer electrolyte composites, mixtures or blends
    • H01M8/1046—Mixtures of at least one polymer and at least one additive
    • H01M8/1048—Ion-conducting additives, e.g. ion-conducting particles, heteropolyacids, metal phosphate or polybenzimidazole with phosphoric acid
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
    • H01M8/124—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte characterised by the process of manufacturing or by the material of the electrolyte
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to a process for the preparation of crystalline pyrophosphates of the general formula (I) with a particle size in the nanometer range M (P 2 O 7 ) (I) by heating the corresponding hydrogen phosphates M (HPO 4 ) 2 .n H 2 O (II ).
  • the pyrophosphates obtained according to the invention are particularly suitable as additives for membranes for fuel cells to increase their stability and service life.
  • Pyrophosphates of formula (I) are known and undergo various modifications, e.g. the ⁇ , ⁇ and ⁇ modification. Pyrophosphates are known for their selectivity, high stability in acidic solvents and their resistance to radiation.
  • BESTATIGUNGSKOPIE the corresponding tetravalent acid phosphates with a layer structure are described, for example, in the following specialist literature: Koh-Ichi et al., Journal of Catalysis 101, 81-89 (1986); U. Constantino et al., Thermochimica Acta 58, 179-189, (1982); AMK Anderson et al., Inorganic Chem. 37, 876-881 (1998).
  • EP-A-0 855 217 describes a process for the preparation of mesoporous tetravalent acid phosphates with a high specific surface area by calcining acid phosphates with a layer structure in the presence of organic compounds at temperatures from 500 to 700 ° C.
  • the crystalline compounds obtained have a size in the range from 30 to 50
  • ZrO (H 2 PO 4 ) 2 • 3 H 2 O at 1100 ° C. for about 4 hours leads to the corresponding pyrophosphate, which has a particle size in the range from 2 to 25 ⁇ m. Further heating to temperatures around 1550 ° C leads to the conversion of Zr (PO 7 ) into (ZrO) 2 P 2 O 7 + P 2 O 5 .
  • the present invention solves this problem and relates to a process for the preparation of crystalline pyrophosphates of the general formula (I) M (P 2 O 7 ) (I) by heating a hydrogen phosphate of the general formula (II) M (HPO 4 ) 2 'n H 2 O (II) in a suitable liquid medium in which M is a tetravalent metal of group IVa or IVb and n is a number in the range from 0 to 20, in particular in the range from 0 to 7, and the pyrophophates of the formula (I) obtained have a particle size in the range from 1 to 1000 nm.
  • Formula (II) in a suitable liquid medium preferably a solvent, preferably under an inert gas, for example nitrogen or argon, with stirring to a temperature of 80 to 450 ° C., preferably 100 to 250 ° C., in particular 120 ° C. to 220 ° C. heated under reflux for a period of 1 to 24 hours, in particular 1 to 10 hours.
  • a suitable liquid medium preferably a solvent, preferably under an inert gas, for example nitrogen or argon
  • the reaction product is, for example, placed in water and washed and centrifuged several times until the washing water reacts neutrally to litmus paper.
  • the crystalline powder thus obtained is dried at 50 to 160 ° C, preferably at 80 to 140 ° C for 1 to 10, in particular 3 to 8 hours.
  • either amorphous tetravalent acid phosphate gels or the corresponding layered ⁇ and / or ⁇ acid phosphates and ⁇ -acid phosphates can be used.
  • the amorphous acid phosphate gels can be diluted by reacting the tetravalent metal oxychlorides or the tetravalent metal alkoxides Phosphoric acid can be obtained.
  • the preparation of the layered, ⁇ and ⁇ modifications of the acid phosphates is described in US-A-4,059,679.
  • Suitable tetravalent acid phosphates of the formula M (HPO 4 ) 2 .n H 2 O (II) are preferably those in which M represents Ti, Zr, Si, Ge, Sn or Pb, in particular Ti, Zr or Sn.
  • Suitable liquid media for the acid phosphates are those in which the compounds of the formula (II) are soluble or can be dispersed or suspended and which are suitable for removing the water formed during the reaction.
  • polyphosphoric acid or mixtures of phosphorus pentoxide and orthophosphoric acid are preferably used.
  • the polyphosphoric acid used according to the invention is a commercially available polyphosphoric acid, such as those available from Riedel-de-Haen, for example.
  • the polyphosphoric acids H m + 2 PmO 3 m + ⁇ (m> 1) usually have a content calculated as P 2 O 5 (acidimetric) of at least 83%.
  • the ratio of the compound M (HPO 4 ) 2 .n H 2 O (mol%) / 100 g of liquid medium is preferably in the range from 0.01 to 10, in particular in the range from 0.025 to 6.5.
  • concentration ie the proportion of acid phosphate (II) in the liquid medium
  • particle size decreases with an increase in concentration of (II). Small particle sizes in the single-digit nanometer range are also observed when the reaction is carried out in
  • the present invention further relates to crystalline pyrophosphate of the formula (I) which is in the form of nano-particles with a particle size in the range from 1 to 1000 nm is present. This can be obtained using the method described above.
  • Crystalline pyrophosphates as can be obtained with the present process, are valuable catalysts for organic reactions, for example, to name but a few, for alkylation, esterification, isomerization or dehydrogenation reactions. These compounds are also used as ceramic materials and as matrix materials or as a dispersion in one, in particular due to their good proton conductivity, their high surface activity and the high thermal stability, even at very high temperatures
  • Polymer for fuel cell applications For example, in the manufacture of membranes for fuel cells, proton-conducting fillers are added to improve the application properties.
  • the present invention therefore relates to a membrane with improved proton conductivity, increased stability and excellent chemical and thermal properties, in particular a polyazole membrane containing at least one compound of the formula (I).
  • Polyazole membranes suitable according to the invention are, for example, the subject of German Patent Applications No. 10 117 686.4, No. 10 117 687.2 and 10 144 815.5, to which reference is hereby expressly made, so that a more detailed description of the suitable membrane materials is dispensed with at this point.
  • a particle size of 300 to 750 nm was determined by electron microscopy.
  • Table 1 shows an overview of experiments 2 to 7 and comparative examples 1 and 2. All experiments were carried out analogously to example 1. If different reaction times or temperatures or product quantities were used, this can be found in the table.
  • Zirconium hydrogen phosphate gel (Aldrich) placed under a nitrogen atmosphere and 100 g of 85% phosphoric acid (Fisher Scientific) added with stirring. The reaction mixture is stirred for 2 hours at 180 ° C. in an inert gas atmosphere, then added to 250 ml of water and centrifuged to isolate the product. The product obtained is washed several times and centrifuged until the wash water reacts neutral to litmus paper. The product obtained is dried in an oven at 120 ° C. for 5 hours. The X-ray diffraction analysis of the dried powder confirms that, analogously to Clarfield and Stynes Report J. Inorg. Nucl. Chem., 26, 117 (1964) zirconium hydrogen phosphate was obtained in the ⁇ -form.
  • the X-ray diffraction analysis of the dried powder showed no crystalline structure.
  • the particle size ranged from 2 to 5 ⁇ m.
  • Comparative example 1 was carried out analogously to Clearfield and Stynes Report J. Inorg. Nucl.
  • Comparative example 2 was carried out analogously to the prior art in a mixture of o-xylene and somewhat concentrated sulfuric acid.
  • the product obtained was not crystalline and the particle diameter was in the range from 2 to 5 ⁇ m.
  • PPA polyphosphoric acid

Abstract

The invention relates to a method for producing crystalline pyrophosphates of general formula M(P207) (I) by heating a hydrogen phosphate of general formula (II) m(HP04)2 n H20 in a suitable liquid medium, where M represents a tetravalent metal of the group IVa or IVb and n is a number from 0 to 20 and the resultant compound of formula (I) has a particle size ranging between 1 and 1000 nm. Preferably, M stands for Ti, Zr, Si, Sn, Ge or Sn, in particular for Ti or Zr. Polyphosphoric acid, phosphorus(V) oxide and orthophosphoric acid, or a mixture of said compounds are preferably used as the liquid medium. The pyrophosphates of formula (I) produced according to said method are particularly suitable for use as additives in fuel cell membranes or for ceramics, or as catalysts in organic reactions, in particular alkylation, isomerisation, esterification or dehydrogenation reactions.

Description

Beschreibungdescription
Verfahren zur Herstellung von kristallinen Pyrophosphaten, sowie Verwendung dieser Verbindungen als Katalysatoren oder als Additiv für die Membranen, insbesondere für Membranen für BrennstoffzellenProcess for the preparation of crystalline pyrophosphates, and use of these compounds as catalysts or as an additive for the membranes, in particular for membranes for fuel cells
Die vorliegende Erfindung betrifft ein Verfahren zur Herstellung von kristallinen Pyrophosphaten der allgemeinen Formel (I) mit einer Partikelgröße im Nanometerbereich M(P2O7) (I) durch Erhitzen der entsprechenden Hydrogenphosphate M(HPO4)2 ■ n H2O (II). Die erfindungsgemäß erhaltenen Pyrophosphate eignen sich besonders gut als Additive für Membranen für Brennstoffzellen zur Erhöhung deren Stabilität und Lebensdauer.The present invention relates to a process for the preparation of crystalline pyrophosphates of the general formula (I) with a particle size in the nanometer range M (P 2 O 7 ) (I) by heating the corresponding hydrogen phosphates M (HPO 4 ) 2 .n H 2 O (II ). The pyrophosphates obtained according to the invention are particularly suitable as additives for membranes for fuel cells to increase their stability and service life.
Pyrophosphate der Formel (I) sind bekannt und treten verschiedenen Modifikationen, z.B. der α-, ß- und γ-Modifikation, auf. Pyrophosphate sind bekannt für ihre Selektivität, hohe Stabilität in säurehaltigen Lösungsmitteln und ihre Beständigkeit gegenüber Bestrahlung.Pyrophosphates of formula (I) are known and undergo various modifications, e.g. the α, β and γ modification. Pyrophosphates are known for their selectivity, high stability in acidic solvents and their resistance to radiation.
Clearfield (US-A-4, 059,679) beschreibt die Herstellung von kristallinen Phosphatmaterialien. So wurde bespielsweise gefunden, daß beim Erhitzen von Zirkonoylchlorid in verdünnter Phosphorsäure unter Rückfluß eine hochkristalline Verbindung, die der allgemeinen Formel Zr(HPO4)2 ' 2 H2O entspricht, entsteht. Erhitzt man die verschiedenen Schichtmodifikationen der tetravalentenClearfield (US-A-4,059,679) describes the production of crystalline phosphate materials. It has been found, for example, that when zirconoyl chloride is heated in dilute phosphoric acid under reflux, a highly crystalline compound which corresponds to the general formula Zr (HPO 4 ) 2 '2 H 2 O is formed. The different layer modifications of the tetravalents are heated
Säurephosphate auf Temperaturen im Bereich von 300 bis 600 °C so kondensieren alle HPO -Gruppen der interlamellaren Regionen zu Pyrophosphatgruppeπ. Allerdings ist diese Kondensation nicht möglich für solche HPO4-Gruppen, die sich an der Oberfläche des Kristalls befinden. Die Kondensation dieser Oberflächengruppen zu den entsprechenden Pyrophosphaten findet erst beiAcid phosphates at temperatures in the range of 300 to 600 ° C so all HPO groups of the interlamellar regions condense to Pyrophosphatgruppeπ. However, this condensation is not possible for those HPO 4 groups that are on the surface of the crystal. The condensation of these surface groups to the corresponding pyrophosphates only takes place at
Temperaturen oberhalb von 900 °C statt, wobei es zu einer Umlagerung der lamellaren Struktur unter Umwandlung in eine dreidimensionale Struktur vom kubischen Typ kommt. Allgemeine Methoden für die Synthese von PyrophosphatenTemperatures above 900 ° C take place, whereby there is a rearrangement of the lamellar structure with conversion into a three-dimensional structure of the cubic type. General methods for the synthesis of pyrophosphates
BESTATIGUNGSKOPIE aus den entsprechenden tetravalenten Säurephosphaten mit Schichtstruktur werden z.B. in folgender Fachliteratur beschrieben: Koh-Ichi et al., Journal of Catalysis 101 , 81-89 (1986); U. Constantino et al., Thermochimica Acta 58, 179-189, (1982); A.M.K. Anderson et al., Inorganic Chem. 37, 876-881 (1998).BESTATIGUNGSKOPIE the corresponding tetravalent acid phosphates with a layer structure are described, for example, in the following specialist literature: Koh-Ichi et al., Journal of Catalysis 101, 81-89 (1986); U. Constantino et al., Thermochimica Acta 58, 179-189, (1982); AMK Anderson et al., Inorganic Chem. 37, 876-881 (1998).
In EP-A-0 855 217 wird ein Verfahren zur Herstellung von mesoporösen tetravalenten Säurephosphaten mit hoher spezifischer Oberfläche durch Kalzinierung von Säurephosphaten mit Schichtstruktur in Gegenwart von organischen Verbindungen bei Temperaturen von 500 bis 700°C, beschrieben. Die erhaltenen kristallinen Verbindungen besitzen eine Größe im Bereich von 30 bis 50EP-A-0 855 217 describes a process for the preparation of mesoporous tetravalent acid phosphates with a high specific surface area by calcining acid phosphates with a layer structure in the presence of organic compounds at temperatures from 500 to 700 ° C. The crystalline compounds obtained have a size in the range from 30 to 50
Ä und eignen sich besonders für die Herstellung von Molekularsieben für größere Moleküle.Ä and are particularly suitable for the production of molecular sieves for larger molecules.
Ein Verfahren zur Herstellung von kubischen kristallinen Zirkoniumpyrophosphaten der Formel Zr(P2O7) wird in US-A-4, 687, 715 offenbart. Durch Erhitzen vonA process for the preparation of cubic crystalline zirconium pyrophosphates of the formula Zr (P 2 O 7 ) is disclosed in US Pat. No. 4,687,715. By heating
ZrO(H2PO4)2 • 3 H2O auf 1100 °C für etwa 4 Stunden gelangt man zu dem entsprechenden Pyrophosphat, das eine Partikelgröße im Bereich von 2 bis 25 μm aufweist. Durch weiteres Erhitzen auf Temperaturen um 1550°C kommt es zur Umwandlung von Zr(P O7) in (ZrO)2P2O7 + P2O5.ZrO (H 2 PO 4 ) 2 • 3 H 2 O at 1100 ° C. for about 4 hours leads to the corresponding pyrophosphate, which has a particle size in the range from 2 to 25 μm. Further heating to temperatures around 1550 ° C leads to the conversion of Zr (PO 7 ) into (ZrO) 2 P 2 O 7 + P 2 O 5 .
Alle im Stand der Technik beschriebenen Verfahren erfordern zur Herstellung von kristallinen tetravalenten Metalipyrophosphaten eine Kalzinierung der entsprechenden tetravalenten Metallsäurephosphate bei Temperaturen > 1000 °C. Die Partikefgrößen der so erhaltenen Pyrophosphate liegen im Bereich von 2 bis 25 μm.All processes described in the prior art require a calcination of the corresponding tetravalent metal acid phosphates at temperatures> 1000 ° C. in order to produce crystalline tetravalent metal pyrophosphates. The particle sizes of the pyrophosphates thus obtained are in the range from 2 to 25 μm.
Es bestand daher die Aufgabe ein wirtschaftliches Verfahren zur Herstellung von kristallinen tetravalenten Metalipyrophosphaten zur Verfügung zu stellen, daß es erlaubt die gewünschten Verbindungen bereits bei niedrigeren Temperaturen zu erhalten und ferner Produkte mit einer Größe im Nanometerbereich liefert, die eine gute Protonenleitfähigkeit zeigen und geeignet sind für die Verwendung als Füllstoffe z.B. für Membranen zur Erhöhung der Stabilität und Säurebeständigkeit oder als keramische Materialien und als Katalysatoren. Die vorliegende Erfindung löst diese Aufgabe und betrifft ein Verfahren zur Herstellung von kristallinen Pyrophosphaten der allgemeinen Formel (I) M(P2O7) (I) durch Erhitzen eines Hydrogenphosphats der allgemeinen Formel (II) M(HPO4)2 ' n H2O (II) in einem geeigneten flüssigen Medium worin M ein tetravalentes Metall der Gruppem IVa oder IVb ist und n eine Zahl im Bereich von 0 bis 20, insbesondere im Bereich von 0 bis 7, ist und die erhaltenen Pyrophophate der Formel (I) eine Partikelgröße im Bereich von 1 bis 1000 nm aufweisen.It was therefore an object of the invention to provide an economical process for the preparation of crystalline tetravalent metal pyrophosphates which allows the desired compounds to be obtained even at lower temperatures and also provides products with a size in the nanometer range which show good proton conductivity and are suitable for the use as fillers, for example for membranes to increase stability and acid resistance, or as ceramic materials and as catalysts. The present invention solves this problem and relates to a process for the preparation of crystalline pyrophosphates of the general formula (I) M (P 2 O 7 ) (I) by heating a hydrogen phosphate of the general formula (II) M (HPO 4 ) 2 'n H 2 O (II) in a suitable liquid medium in which M is a tetravalent metal of group IVa or IVb and n is a number in the range from 0 to 20, in particular in the range from 0 to 7, and the pyrophophates of the formula (I) obtained have a particle size in the range from 1 to 1000 nm.
Bei dem erfindungsgemäßen Verfahren werden Verbindungen der allgemeinenIn the process of the invention, compounds of the general
Formel (II) in einem geeigneten flüssigen Medium, vorzugsweise einem Lösungsmittel, vorzugsweise unter Inertgas, beispielsweise Stickstoff oder Argon, unter Rühren auf eine Temperatur von 80 bis 450°C, vorzugsweise 100 bis 250°C, insbesondere 120°C bis 220°C über einen Zeitraum von 1 bis 24 Stunden, insbesondere 1 bis 10 Stunden, unter Rückfluß erhitzt. Zur Isolation desFormula (II) in a suitable liquid medium, preferably a solvent, preferably under an inert gas, for example nitrogen or argon, with stirring to a temperature of 80 to 450 ° C., preferably 100 to 250 ° C., in particular 120 ° C. to 220 ° C. heated under reflux for a period of 1 to 24 hours, in particular 1 to 10 hours. To isolate the
Reaktionsproduktes wird die Lösung beispielsweise in Wasser gegeben und mehrmals gewaschen und zentrifugiert, bis das Waschwasser gegenüber Lackmuspapier neutral reagiert. Das so erhaltene kristalline Pulver wird bei 50 bis 160 °C, vorzugsweise bei 80 bis 140 °C für 1 bis 10, insbesondere 3 bis 8 Stunden getrocknet. Man erhält hochkristallines M(P2O7) mit einer Partikelgröße im Bereich von 1 bis 1000 nm, insbesondere 10 bis 850 nm.The reaction product is, for example, placed in water and washed and centrifuged several times until the washing water reacts neutrally to litmus paper. The crystalline powder thus obtained is dried at 50 to 160 ° C, preferably at 80 to 140 ° C for 1 to 10, in particular 3 to 8 hours. Highly crystalline M (P 2 O 7 ) with a particle size in the range from 1 to 1000 nm, in particular 10 to 850 nm, is obtained.
Ais Ausgangsverbindung der Formel (II) können entweder amorphe tetravalente Säurephosphat-Gele oder auch die entsprechenden schichtförmigen α- und/oder γ- Säurephosphate, sowie ß-Säurephosphate eingesetzt werden.As the starting compound of the formula (II), either amorphous tetravalent acid phosphate gels or the corresponding layered α and / or γ acid phosphates and β-acid phosphates can be used.
Die amorphen Säurephosphatgele können durch Umsetzung der tetravalenten Metalloxychloride oder der tetravalenten Metallalkoxide mit verdünnter Phosphorsäure erhalten werden. Die Herstellung der schichtförmigen -, ß- und γ- Modifikationen der Säurephosphate wird in US-A-4,059,679 beschrieben.The amorphous acid phosphate gels can be diluted by reacting the tetravalent metal oxychlorides or the tetravalent metal alkoxides Phosphoric acid can be obtained. The preparation of the layered, β and γ modifications of the acid phosphates is described in US-A-4,059,679.
Als tetravalente Säurephosphate der Formel M(HPO4)2 ■ n H2O (II) kommen vorzugsweise solche in Frage in denen M für Ti, Zr, Si, Ge, Sn oder Pb, insbesondere für Ti, Zr oder Sn steht.Suitable tetravalent acid phosphates of the formula M (HPO 4 ) 2 .n H 2 O (II) are preferably those in which M represents Ti, Zr, Si, Ge, Sn or Pb, in particular Ti, Zr or Sn.
Als flüssiges Medium für die Säurephosphate sind solche geeignet in denen die Verbindungen der Formel (II) löslich sind oder dispergiert oder suspendiert werden können und die geeignet sind, das während der Reaktion gebildete Wasser abzuführen. Erfindungsgemäß werden bevorzugt Polyphosphorsäure oder Gemische von Phosphorpentoxid und ortho-Phosphorsäure eingesetzt.Suitable liquid media for the acid phosphates are those in which the compounds of the formula (II) are soluble or can be dispersed or suspended and which are suitable for removing the water formed during the reaction. According to the invention, polyphosphoric acid or mixtures of phosphorus pentoxide and orthophosphoric acid are preferably used.
Bei der erfindungsgemäß verwendeten Polyphosphorsäure handelt es sich um handelsübliche Polyphosphorsäuren, wie diese beispielsweise von Riedel-de-Haen erhältlich sind. Die Polyphosphorsäuren Hm+2PmO3m+ι (m> 1 ) besitzen üblicherweise einen Gehalt berechnet als P2O5 (acidimetrisch) von mindestens 83%.The polyphosphoric acid used according to the invention is a commercially available polyphosphoric acid, such as those available from Riedel-de-Haen, for example. The polyphosphoric acids H m + 2 PmO 3 m + ι (m> 1) usually have a content calculated as P 2 O 5 (acidimetric) of at least 83%.
Das Verhältnis der Verbindung M(HPO4)2 • n H2O (mol%) / 100g flüssiges Medium liegt vorzugsweise im Bereich von 0,01 bis 10, insbesondere im Bereich von 0,025 bis 6,5. Durch Variation der Konzentration, d.h. des Anteils an Säurephosphat (II) im flüssigen Medium, ist es möglich Einfluß auf die Partikelgröße der gebildeten Verbindung (I) zu nehmen. Wie aus Beispiel 3 ersichtlich nimmt die Partikelgröße bei einer Konzentrationserhöhung von (II) ab. Ebenfalls kleine Partikelgrößen im einstelligen Nanometerbereich werden bei Durchführung der Reaktion inThe ratio of the compound M (HPO 4 ) 2 .n H 2 O (mol%) / 100 g of liquid medium is preferably in the range from 0.01 to 10, in particular in the range from 0.025 to 6.5. By varying the concentration, ie the proportion of acid phosphate (II) in the liquid medium, it is possible to influence the particle size of the compound (I) formed. As can be seen from Example 3, the particle size decreases with an increase in concentration of (II). Small particle sizes in the single-digit nanometer range are also observed when the reaction is carried out in
Schwefelsäure mit einem geringen Anteil eines organischen Lösungsmittels erhalten. Wie bereits erwartet führt dieses Verfahren nicht zu den gewünschten kristallinen Pyrophoshat , sondern lediglich zu nicht-kristallinen Modifikationen (Vergleichsbeispiel 2).Obtained sulfuric acid with a small proportion of an organic solvent. As already expected, this process does not lead to the desired crystalline pyrophoshate, but only to non-crystalline modifications (comparative example 2).
Die vorliegende Erfindung betrifft weiterhin kristallines Pyrophosphat der Formel (I) welches in Form von Nano-Partikeln mit einer Partikelgröße im Bereich von 1 bis 1000 nm vorliegt. Dieses ist mittels des vorstehend beschriebenen Verfahrens erhältlich.The present invention further relates to crystalline pyrophosphate of the formula (I) which is in the form of nano-particles with a particle size in the range from 1 to 1000 nm is present. This can be obtained using the method described above.
Kristalline Pyrophosphate, wie sie mit dem vorliegenden Verfahren erhältlich sind, stellen wertvolle Katalysatoren für organische Reaktionen dar, beispielsweise, um nur einige zu nennen, für Alkylierungs-, Veresterungs-, Isomerisierungs- oder Dehydrierungsreaktionen. Femer finden diese Verbindungen, insbesondere aufgrund ihrer guten Protonenleitfähigkeit , ihrer großen Oberflächenaktivität und der hohen thermischen Stabilität auch bei sehr hohen Temperaturen Verwendung als keramische Materialien und als Matrixmaterialien oder als Dispersion in einemCrystalline pyrophosphates, as can be obtained with the present process, are valuable catalysts for organic reactions, for example, to name but a few, for alkylation, esterification, isomerization or dehydrogenation reactions. These compounds are also used as ceramic materials and as matrix materials or as a dispersion in one, in particular due to their good proton conductivity, their high surface activity and the high thermal stability, even at very high temperatures
Polymer für Anwendungen im Brennstoffzellenbereich. So werden z.B. bei der Herstellung von Membranen für Brennstoffzellen protonenleitende Füllstoffe zur Verbesserung der anwendungstechnischen Eigenschaften zugegeben.Polymer for fuel cell applications. For example, in the manufacture of membranes for fuel cells, proton-conducting fillers are added to improve the application properties.
In einer weiteren Ausführungsform betrifft daher die vorliegende Erfindung eine Membran mit verbesserter Protonenleitfähigkeit, erhöhter Stabilität und hervorragenden chemischen und thermischen Eigenschaften, insbesondere eine Polyazolmembran, enthaltend mindestens eine Verbindung der Formel (l).In a further embodiment, the present invention therefore relates to a membrane with improved proton conductivity, increased stability and excellent chemical and thermal properties, in particular a polyazole membrane containing at least one compound of the formula (I).
Erfindungsgemäß geeignete Polyazolmembranen sind beispielsweise Gegenstand der Deutschen Patenanmeldungen Nr. 10 117 686.4, Nr. 10 117 687.2 und 10 144 815.5, auf die hiermit ausdrücklich Bezug genommen wird, so daß auf eine ausführlichere Beschreibung der geeigneten Membranmaterialien an diesem Punkt verzichtet wird.Polyazole membranes suitable according to the invention are, for example, the subject of German Patent Applications No. 10 117 686.4, No. 10 117 687.2 and 10 144 815.5, to which reference is hereby expressly made, so that a more detailed description of the suitable membrane materials is dispensed with at this point.
Die Erfindung soll durch die nachfolgenden Beispiele näher erläutert werden, ohne diese darauf zu beschränken. BeispieleThe invention is intended to be explained in more detail by the examples below, without restricting it thereto. Examples
Beispiel 1:Example 1:
In einen 250 ml Dreihalskolben, versehen mit einem mechanischen Rührer, Rückflußkühler und einem Stickstoff Einlaß- und Auslaßventil, werden 5,0 gIn a 250 ml three-necked flask equipped with a mechanical stirrer, reflux condenser and a nitrogen inlet and outlet valve, 5.0 g
Zirkoniumhydrogenphosphat-Gel (Aldrich) unter einer Stickstoffatmosphäre vorgelegt und 100 g Polyphosphorsäure (FMC Chemical Co.) unter Rühren zugegeben. Das Reaktionsgemisch wird für 2 Stunden bei 150 °C in der Inertgasatmosphäre gerührt, anschliessend in 250 ml Wasser gegeben und zur Isolation des Produktes zentrifugiert. Das erhaltene Produkt wird mehrmals gewaschen und zentrifugiert bis das Waschwasser neutral gegenüber Lackmuspapier reagiert. Das erhaltene Produkt wird in einem Ofen bei 120 °C für 5 Stunden getrocknet. Die Röntgen Diffraktions Analyse des getrockneten Pulvers bestätigt, daß das erhaltene Zr(P2O ) kristalliner Struktur ist und in der Pyro-Form vorliegt. Mit Hilfe derZirconium hydrogen phosphate gel (Aldrich) placed under a nitrogen atmosphere and 100 g of polyphosphoric acid (FMC Chemical Co.) added with stirring. The reaction mixture is stirred for 2 hours at 150 ° C. in an inert gas atmosphere, then added to 250 ml of water and centrifuged to isolate the product. The product obtained is washed several times and centrifuged until the wash water reacts neutral to litmus paper. The product obtained is dried in an oven at 120 ° C. for 5 hours. The X-ray diffraction analysis of the dried powder confirms that the Zr (P 2 O) obtained is crystalline structure and is in the pyro form. With the help of
Elektronenmikroskopie wurde eine Partikelgröße von 300 bis 750 nm ermittelt.A particle size of 300 to 750 nm was determined by electron microscopy.
Tabelle 1 zeigt eine Übersicht über Versuche 2 bis 7 und die Vergleichsbeispiele 1 und 2. Sämtliche Versuche wurden analog zu Beispiel 1 durchgeführt. Sofern unterschiedliche Reaktionszeiten oder -temperaturen oder Produktmengen angewandt wurden, findet sich dies in der Tabelle wieder.Table 1 shows an overview of experiments 2 to 7 and comparative examples 1 and 2. All experiments were carried out analogously to example 1. If different reaction times or temperatures or product quantities were used, this can be found in the table.
Vergleichsbeispiel 1 :Comparative Example 1:
In einen 250 ml Dreihalskolben, versehen mit einem mechanischen Rührer, Rückflußkühler und einem Stickstoff Einlaß- und Auslaßventil, werden 5,0 gIn a 250 ml three-necked flask equipped with a mechanical stirrer, reflux condenser and a nitrogen inlet and outlet valve, 5.0 g
Zirkoniumhydrogenphosphat-Gel (Aldrich) unter einer Stickstoffatmosphäre vorgelegt und 100 g 85%ige Phosphorsäure (Fisher Scientific) unter Rühren zugegeben. Das Reaktionsgemisch wird für 2 Stunden bei 180 °C in einer Inertgasatmosphäre gerührt, anschliessend in 250 ml Wasser gegeben und zur Isolation des Produktes zentrifugiert. Das erhaltene Produkt wird mehrmals gewaschen und zentrifugiert bis das Waschwasser neutral gegenüber Lackmuspapier reagiert. Das erhaltene Produkt wird in einem Ofen bei 120 °C für 5 Stunden getrocknet. Die Röntgen Diffraktions Analyse des getrockneten Pulvers bestätigt, daß analog zu Cläarfield and Stynes Report J. Inorg. Nucl. Chem., 26, 117 (1964) Zirkoniumhydrogenphophat in der α-Form erhalten wurde.Zirconium hydrogen phosphate gel (Aldrich) placed under a nitrogen atmosphere and 100 g of 85% phosphoric acid (Fisher Scientific) added with stirring. The reaction mixture is stirred for 2 hours at 180 ° C. in an inert gas atmosphere, then added to 250 ml of water and centrifuged to isolate the product. The product obtained is washed several times and centrifuged until the wash water reacts neutral to litmus paper. The product obtained is dried in an oven at 120 ° C. for 5 hours. The X-ray diffraction analysis of the dried powder confirms that, analogously to Clarfield and Stynes Report J. Inorg. Nucl. Chem., 26, 117 (1964) zirconium hydrogen phosphate was obtained in the α-form.
Vergleichsbeispiel 2:Comparative Example 2:
In einen 250 ml Dreihalskolben, versehen mit einem mechanischen Rührer, Rückflußkühler und einem Stickstoff Einlaß- und Auslaßventil,' erden 5,0 g Zirkoniumhydrogenphosphat-Gel (Aldrich) unter einer Stickstoffatmosphäre vorgelegt und 100 g o-Xylol (Acros.) mit 1 ml konzentrierter Schwefelsäure (Fisher Scientific) unter Rühren zugegeben. Das Reaktionsgemisch wird für 2 Stunden beiIn a 250 ml three-necked flask equipped with a mechanical stirrer, reflux condenser and nitrogen inlet and outlet, 'ground 5.0 g of zirconium hydrogen phosphate gel (Aldrich) are introduced under a nitrogen atmosphere, and 100 g o-xylene (Acros.) With 1 ml concentrated sulfuric acid (Fisher Scientific) added with stirring. The reaction mixture is at for 2 hours
180 °C in der Inertgasatmosphäre gerührt, anschliessend in 250 ml Wasser gegeben und zur Isolation des Produktes zentrifugiert. Das Reaktionsgemisch wird anschliessend filtriert und luftgetrocknet und abschliessend mit Wasser gewaschen, um überschüssige Schwefelsäure zu entfernen. Das erhaltene Produkt wird in einem Ofen bei 120 °C für 5 Stunden getrocknet.Stirred at 180 ° C in the inert gas atmosphere, then added to 250 ml of water and centrifuged to isolate the product. The reaction mixture is then filtered and air-dried and then washed with water to remove excess sulfuric acid. The product obtained is dried in an oven at 120 ° C. for 5 hours.
Die Röntgen Diffraktions Analyse des getrockneten Pulvers zeigte keine kristalline Struktur. Die Partikelgröße lag im Bereich von 2 bis 5 μm.The X-ray diffraction analysis of the dried powder showed no crystalline structure. The particle size ranged from 2 to 5 μm.
Bei den erfindungsgemäßen Beispielen 1 bis 7 wurde in allen Fällen kristallines Zirkonpyrophosphat in der Pyroform erhalten.In Examples 1 to 7 according to the invention, crystalline zirconium pyrophosphate was obtained in the pyroform in all cases.
Vergleichsbeispiel 1 wurde analog zu Clearfield and Stynes Report J. Inorg. Nucl.Comparative example 1 was carried out analogously to Clearfield and Stynes Report J. Inorg. Nucl.
Chem., 26, 117 (1964) durchgeführt und lieferte erwartungsgemäßChem., 26, 117 (1964) and delivered as expected
Zirkoniumhydrogenphosphat in der α-Form.Zirconium hydrogen phosphate in the α-form.
Vergleichsbeispiel 2 wurde analog zum Stand der Technik in einem Gemisch aus o- Xylol und etwas konzentrierter Schwefelsäure durchgeführt. Das erhaltene Produkt war nicht kristallin und der Partikeldurchmesser lag im Bereich von 2 bis 5 μm.Comparative example 2 was carried out analogously to the prior art in a mixture of o-xylene and somewhat concentrated sulfuric acid. The product obtained was not crystalline and the particle diameter was in the range from 2 to 5 μm.
In der nachfolgenden Tabelle steht PPA für Polyphosphorsäure.
Figure imgf000009_0001
In the table below, PPA stands for polyphosphoric acid.
Figure imgf000009_0001

Claims

Patentansprüche: claims:
1. Verfahren zur Herstellung von kristallinen Pyrophosphaten der allgemeinen Formel (I)1. Process for the preparation of crystalline pyrophosphates of the general formula (I)
M(P2O7) (I) durch Erhitzen eines Hydrogenphosphats der allgemeinen Formel (II) M(HP04)2 ' n H20 (II) in einem geeigneten flüssigen Medium worin M ein tetravalentes Metall der Gruppem IVa oder IVb ist und n eine Zahl im Bereich von 0 bis 20 ist und die erhaltene Verbindung der Formel (I) eine Partikelgröße im Bereich von 1 bis 1000 nm aufweist.M (P 2 O 7 ) (I) by heating a hydrogen phosphate of the general formula (II) M (HP0 4 ) 2 'n H 2 0 (II) in a suitable liquid medium in which M is a tetravalent metal from groups IVa or IVb and n is a number in the range from 0 to 20 and the compound of formula (I) obtained has a particle size in the range from 1 to 1000 nm.
2. Verfahren nach Anspruch 1 , dadurch gekennzeichnet, daß M für Ti, Zr, Si, Sn, Ge oder Sn, insbesondere für Ti oder Zr steht.2. The method according to claim 1, characterized in that M stands for Ti, Zr, Si, Sn, Ge or Sn, in particular for Ti or Zr.
3. Verfahren nach Anspruch 1 und/oder 2, dadurch gekennzeichnet, daß als flüssiges Medium Polyphosphorsäure, Phosphorpentoxid und ortho- Phosphorsäure oder ein Gemisch dieser Verbindungen verwendet wird.3. The method according to claim 1 and / or 2, characterized in that polyphosphoric acid, phosphorus pentoxide and orthophosphoric acid or a mixture of these compounds is used as the liquid medium.
4. Verfahren nach einem oder mehreren der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß als Ausgangsverbindung der Formel (II) amorphes tetravalentes Säurephosphat-Gel oder die entsprechenden schichtförmigen α-, ß- und/oder γ- Säurephosphate eingesetzt werden.4. The method according to one or more of the preceding claims, characterized in that amorphous tetravalent acid phosphate gel or the corresponding layered α-, β- and / or γ-acid phosphates are used as the starting compound of the formula (II).
5. Verfahren nach einem oder mehrerem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Reaktionstemperatur im Bereich von 80 bis 450°C, vorzugsweise 100°C bis 250°C, liegt.5. The method according to one or more of the preceding claims, characterized in that the reaction temperature is in the range from 80 to 450 ° C, preferably 100 ° C to 250 ° C.
6. Verfahren nach einem oder mehrerern der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß das Verhältnis M(HPO )2 • n H2O (mol%) / 100g flüssiges Medium im Bereich von 0,01 bis 10, insbesondere im Bereich von 0,025 bis 6,5 liegt.6. The method according to one or more of the preceding claims, characterized in that the ratio M (HPO) 2 • n H 2 O (mol%) / 100g liquid medium is in the range from 0.01 to 10, in particular in the range from 0.025 to 6.5.
7. Verfahren nach einem oder mehrerem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Reaktion unter Schutzgas durchgeführt wird.7. The method according to one or more of the preceding claims, characterized in that the reaction is carried out under a protective gas.
8. Kristallines Pyrophosphat der Formel (I) M(P207) (I) worin M ein tetravalentes Metall der Gruppem IVa oder IVb ist und n eine Zahl im Bereich von 0 bis 20 ist und dessen Partikelgröße im Bereich von 1 bis 1000 nm liegt.8. Crystalline pyrophosphate of the formula (I) M (P 2 0 7 ) (I) wherein M is a tetravalent metal from groups IVa or IVb and n is a number in the range from 0 to 20 and its particle size in the range from 1 to 1000 nm.
9. Kristallines Pyrophosphat gemäß Anspruch 8, dadurch gekennzeichnet, daß die Partikelgröße im Bereich von 10 bis 850 nm liegt.9. Crystalline pyrophosphate according to claim 8, characterized in that the particle size is in the range from 10 to 850 nm.
10. Verwendung von kristallinem Pyrophosphat gemäß der Ansprüche 8 und/ oder 9 als Additiv in Brennstoffzellen-Membranen oder keramische Materialien, oder als Katalysator in organischen Reaktionen, insbesondere Aklylierungs-, Isomerisierungs-, Vereesterungs- oder Dehydrogenierungsreaktionen.10. Use of crystalline pyrophosphate according to claims 8 and / or 9 as an additive in fuel cell membranes or ceramic materials, or as a catalyst in organic reactions, in particular alkylation, isomerization, esterification or dehydrogenation reactions.
11. Protonenleitende Polymermembran enthaltend kristallines Pyrophosphat der Formel (I) M(P2O7) (I) dessen Partikelgröße im Bereich von 10 bis 850 nm liegt.11. Proton-conducting polymer membrane containing crystalline pyrophosphate of the formula (I) M (P 2 O 7 ) (I) whose particle size is in the range from 10 to 850 nm.
12. Polymermembran gemäß Anspruch 11 , dadurch gekennzeichnet, daß es sich um eine Polymermembran enthaltend Polyazole handelt. 12. A polymer membrane according to claim 11, characterized in that it is a polymer membrane containing polyazoles.
PCT/EP2004/008857 2003-08-08 2004-08-06 Method for producing crystalline pyrophosphates, use of said compounds as catalysts or as additives for membranes, in particular for membranes of fuel cells WO2005014474A2 (en)

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