PROCESS FOR PRODUCING A CATALYST COMPRISING AN INTERMETALLIC COMPOUND AND A CATALYST PRODUCED BY THE PROCESS

Abstract

The invention relates to aprocess for producing a catalyst comprising an intermetallic com-pound comprisingmixing of a salt comprising a metal selected from the group consisting of Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Auand Ru, a salt comprising a metal selected from the group consist-ing of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba,Sc, Y, La and the lanthanides, and a reducing agentcomprising a salt,wherein the mixing is carried out at a temperature where all compo-nents are solid; reacting the mixture obtained to form an intermetallic compound by heating said to a temperature in the range between the melting temperature of thereducing agent and the melting temperature of the intermetallic compound and holdingthe temperaturefor1 minute to 600 minutes; and washing the mixture to removeby-products andremainders of the salt of the cations of the reducing agent and at least one of the anions of the salts used in the first step. The invention further relates to a catalyst obtained by the process.

Claims

1. A process for producing a catalyst comprising an intermetallic compound, the process comprising following steps: (a) Mixing of a salt comprising a metal selected from the group consisting of Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au and Ru, a salt comprising a metal selected from the group consisting of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Sc, Y, La and the lanthanides, and a reducing agent comprising a salt, wherein the mixing is carried out at a temperature where all components are solid; (b) Reacting the mixture obtained in step (a) to form an intermetallic compound by heating said mixture to a temperature in the range between the melting temperature of the reducing agent and the melting temperature of the intermetallic compound and holding the temperature for 1 minute to 600 minutes; (c) Optionally, washing the mixture obtained in step (b) once or repeatedly with one or more aprotic solvents or combinations of aprotic solvents, whereby a salt of the cation of the reducing agent and at least one of the anions of the salts used in step (a) does not dissolve in said solvent, followed by heating the mixture obtained after washing to a temperature in the range between the melting temperature of the reducing agent and the melting temperature of the intermetallic compound and holding the temperature for 1 minute to 600 minutes, wherein the washing and heating can be carried out repeatedly; and (d) Washing the mixture obtained in step (b) or (c) to remove by-products and remainders of the salt of the cations of the reducing agent and at least one of the anions of the salts used in step (a).

2. The process according to claim 1, wherein a support is added in step (a) or during the washing in step (c) or in step (d) to achieve a supported catalyst comprising the support and the intermetallic compound, wherein the intermetallic compound is in the form of nanoparticles and deposited on the surface of the support and in the pores of the support.

3. The process according to claim 1, wherein an aprotic liquid is added to the solid components in step (a) as a plasticizer or stirring aid, the aprotic liquid being selected from the group consisting of alkanes, alkenes, aromatic hydrocarbons, amines, ethers and mixtures thereof, provided that each of said components is liquid at 50° C.

4. The process according to claim 3, wherein the aprotic liquid added in step (a) is selected from the group consisting of squalane, 1,13-tetradecadiene, 1-octadecene, trioctlyamine, 1,3-diisopropylbenzene and dioctyl ether.

5. The process according to claim 1, wherein in step (a) additionally an inert salt is added.

6. The process according to claim 5, wherein the inert salt is an alkali metal halide.

7. The process according to claim 1, wherein step (a), step (b) and the heating in step (c) are carried out in an inert atmosphere.

8. The process according to claim 1, wherein the salt comprising a metal selected from the group consisting of Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au and Ru is a platinum salt, a silver salt, a rhodium salt, an iridium salt, a palladium salt or a gold salt.

9. The process according to claim 1, wherein the salt comprising a metal selected from the group consisting of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Sc, Y, La and the lanthanides is a calcium salt, an yttrium salt, a scandium salt or a lanthanum salt.

10. The process according to claim 1, wherein the salt comprising a metal selected from the group consisting of Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au and Ru is a halide.

11. The process according to claim 1, wherein the salt comprising a metal selected from the group consisting of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Sc, Y, La and the lanthanides is a halide.

12. The process according to claim 10, wherein the halide is a chloride.

13. The process according to claim 1, wherein the reducing agent is an alkali metal alkylborohydride or an alkali metal arylborohydride or a mixture of an alkali metal hydride with an alkylborane or an arylborane.

14. The process according to claim 1, wherein the reducing agent is selected from the group consisting of alkali metal triethylborohydride, alkali metal tripropylborohydride, alkali metal tributylborohydride, alkali metal hydride with triethylborane, alkali metal hydride with tripropylborane, and alkali metal hydride with tributylborane.

15. The process according to claim 14, wherein the alkali metal of the reducing agent is potassium or sodium.

16. The process according to claim 1, wherein the aprotic solvent which is used for washing in step (c) is selected from the group consisting of tetrahydrofuran, dioxanes, ethylene glycol dimethyl ether and diethylene glycol dimethyl ether either alone or in conjunction with a low-boiling alkane from the group consisting of pentane, hexane, and heptane.

17. The process according to claim 1, wherein the washing in step (d) is carried out with water or an aqueous solution of an acid.

18. A catalyst produced by the process according to claim 1, wherein the catalyst comprises a support and an intermetallic compound comprising a metal selected from the group consisting of Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au and Ru, and a metal selected from the group consisting of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Sc, Y, La, and lanthanides, wherein the intermetallic compound is in the form of nanoparticles and is deposited on the surface of the support and in macropores, mesopores and micropores of the support.

19. The catalyst according to claim 18, wherein the intermetallic compound comprises platinum and one of Ca, Y, Sc and La.

20. The catalyst according to claim 18, wherein the support is a porous support having a BET surface of at least 4 m2/g.

21. The catalyst according to claim 18, wherein the support is a metal oxide or carbon.

22. The catalyst according to claim 18, wherein the support is selected from the group consisting of carbon black, activated carbon, graphenes and graphite.

23. The catalyst according to claim 18, wherein the intermetallic compound is Pt2Ca, Pt3Y, Pt3Sc or Pt3La.

24. The process according to claim 11, wherein the halide is a chloride.

Description

[0075] The powders obtained in example 1 and example 2 were analyzed by transmission electron microscopy (TEM) and x-ray diffraction (XRD). The results are shown in the accompanying figures.

[0076] FIG. 1 shows a TEM picture of the powder obtained in example 1,

[0077] FIG. 2 shows an XRD pattern of the powder obtained in example 1,

[0078] FIG. 3 shows a TEM picture of the powder obtained in example 2,

[0079] FIG. 4 shows an XRD pattern of the powder obtained in example 2.

[0080] TEM and electron diffraction were performed on a LaB.sub.6 FEI Tecnai G2 20 TEM operating at 200 kV. TEM samples were prepared by placing a drop of the particle solution onto a carbon-coated copper grid.

[0081] XRD was performed on a Bruker D8 GADDS diffractometer with a cobalt source (Kα1=1.79 Å). When necessary, XRD samples were dropcast onto a flat plastic holder.

[0082] As can be seen in FIG. 1, in the obtained final product of example 1 nanoparticles are present. The obtained final product of example 2 also is present in nanoparticles, however, as can be seen in FIG. 3, the nanoparticles are agglomerated.

[0083] The XRD spectrograph in FIG. 2 of the product obtained in example 1 shows the presence of Pt.sub.3Y as main phase and minor amounts of Pt.

[0084] In example 2 an intermetallic compound Pt.sub.3Y with high purity was obtained as can be seen in the XRD spectrograph in FIG. 4.

[0085] In FIGS. 2 and 4 the bars represent library data of Pt.sub.3Y. In FIG. 2 the triangular dots represent the library data of platinum.

[0086] In the XRD spectrographs the reflexes that are assigned to Pt.sub.3Y are shifted towards lower angles in comparison to library data, corresponding to higher lattice constants. These observations can be explained by interstitial hydrides as observed for La—Ni systems as described by Lynch, J. F.; Reilly, J. J., J. Less-Common Metals, 1982 87, pages 225-236.