Selective platinum-copper alloy formation in a platinum, copper and rhobium Termetallic System In ZSm-5 : an exafs investigation

الملخص EN

Ln-situ EXAFS studies of Cu-Pt-Rh-ZSM-5 a termetallic system have been carried out for the as made catalyst and also for the same catalyst system after reduction under hydrogen.

The studies were carried out on all the three edges, namely Cu and Rh K-edges and Pt Lm-edge.

These studies show the interaction of metals with oxygen in as made catalyst and a complete reduction of all the three metals to zero oxidation state from +2, +2 and +3 respectively, when treated with molecular hydrogen at 250° C.

Before reduction there is no interaction between different metals, however, after reduction there is clear evidence of the formation of copper-platinum alloy as evidenced both by copper K-edge and Platinum Lm-edge.

Rhodium clearly reduces on its own without any interaction with the other metals.

These results clearly indicate the selective alloy formation between copper and platinum.

The coordination numbers found for copper and platinum clearly indicate nano particle formation for this alloy system, whereas, rhodium clearly forms large particles, with no interaction with the other two metals.

This indicates that the platinum-copper alloy particles stay inside ZSM-5 but rhodium comes out of the zeolite on the surface.