Noble metal-containing supported catalyst and a process for its preparation
The invention provides a noble metal-containing supported catalyst which contains one of the noble metals from the group Au, Ag, Pt, Pd, Rh, Ru, Ir, Os or alloys of one or more of these noble metals in the form of noble metal particles on a powdered support material. The particles deposited on the support material have a degree of crystallinity, determined by X-ray diffraction, of more than 2 and an average particle size between 2 and 10 nm. The high crystallinity and the small particle size of the noble metal particles lead to high catalytic activity for the catalyst. It is particularly suitable for use in fuel cells and for the treatment of exhaust gases from internal combustion engines.
1. A noble metal-containing supported catalyst comprising one or more noble metals selected from the group consisting of Au, Ag, Pt, Pd, Rh, Ru, Ir, Os and alloys thereof deposited in the form of noble metal particles on a powdered carbon-containing support material, wherein the noble metal particles have a relative degree of crystallinity of greater than 5 as determined by X-ray diffraction and an average particle size of between about 2 and about 10 nm.
2. A supported catalyst according to claim 1 , wherein the carbon-containing support material is selected from the group consisting of carbon black, graphite, active carbon and fibrous, and graphitic nanotubes.
3. A supported catalyst according to claim 2 , wherein the noble metals are alloyed with at least one base metal selected from the group consisting of Ti, Zr, V, Cr, Mn, Fe, Co, Ni, Cu and Zn.
4. A supported catalyst according to claim 2 , wherein the supported catalyst contains Pt on carbon black with a surface area of at least 40 m 2 /g in a concentration between 5 and 80 wt. % based on the total weight of support material and Pt.
5. A supported catalyst according to claim 2 , wherein the supported catalyst contains a Pt/Ru alloy on carbon black with a surface area of at least 40 m 2 /g in a concentration between 5 and 80 wt. % based on the total weight of support material and alloy, and wherein the atomic ratio Pt to Ru is between 5:1 and 1:5.