Influence of Support Materials on Durability of Palladium in Three-Way Catalyst

Mari Yamamoto; Hirohisa Tanaka

doi:10.4271/980664

1998-02-23

Influence of Support Materials on Durability of Palladium in Three-Way Catalyst 980664

In this paper, we studied the influence of support materials on Pd in three-way catalysts for the aim of enhancing the durability of Pd, particularly CO and NOx conversion efficiencies which are usually seriously damaged after aging. Since the durability of precious metals was found to be strongly influenced by the support material chosen, it should be possible to optimize catalyst performance by finding the appropriate support.

The performance of Pd three-way catalysts with different support materials (Aluminum oxide, Cerium - Zirconium Oxide, Cerium - Zirconium -Yttrium Oxide, Zirconium Oxide, or Titanium Oxide) was compared after high temperature agings under various gas conditions.

To assess Pd deterioration, the crystallite size of Pd was measured with XRD and the micro surface was observed by FE-SEM. The performance of the catalysts was evaluated.

In summary, Pd supported on Aluminum oxide maintained the smallest crystallite size, by maximizing activation points which is imperative under the static A/F condition.

On the other hand, Pd supported on Cerium -Zirconium - Yttrium Oxide (Ce-Zr-Y oxide) showed the best performance under A/F fluctuating conditions to simulate a close coupled catalyst. It is considered that Pd supported directly on Ce-Zr-Y oxide promoted the rapid response of Oxygen Storage Capacity (OSC).

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Influence of Support Materials on Durability of Palladium in Three-Way Catalyst 980664

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