Magnesium Elektron, Inc.

University of Kentucky Research Foundation

John G Darab

Deborah Jayne Harris

David Alastair Scapens

Mark Crocker

Yaying Ji

A passive NOadsorbent includes: palladium, platinum or a mixture thereof and a mixed or composite oxide including the following elements in percentage by weight, expressed in terms of oxide: 10-90% by weight zirconium and 0.1-50% by weight of least one of the following: a transition metal or a lanthanide series element other than Ce. Although the passive NOadsorbent can include Ce in an amount ranging from 0.1 to 20% by weight expressed in terms of oxide, advantages are obtained particularly in the case of low-Ce or a substantially Ce-free passive NOx adsorbent.

Zirconia-based compositions for use in passive NOx adsorber devices

An improved method for the formation of composite hydroxides or oxides comprising, on an oxide basis, AlOand ZrO, and optionally CeO, LaO, NdO, PrO, SmO, YO, and other rare earth oxides, comprising the steps of preparing an aqueous metal salt solution and forming a hydroxide precipitate slurry by combining the aqueous metal salt solution with an aqueous solution of a caustic alkali at a pH greater than 8.5 to precipitate out all the metal species. The variation in pH during the precipitation reaction is &#xb1;1. The invention also relates to composites formed by this method comprising 20-70 wt % AlO, 10-77 wt % ZrO, 0-34 wt % CeOand 0-22 wt % REOs other than CeO, and to composites per se comprising, on an oxide basis, 42-70 wt % AlO, 10-48 wt % ZrO, 2-34 wt % CeOand 0-9 wt % REOs other than CeOand having the following properties after heating to 850&#xb0; C. over four hours and holding at 850&#xb0; C. for four hours then allowing to cool to ambient temperature: &#x2014;a surface area after aging at 950&#xb0; C. for 2 hours equal to or greater than 60 m/g, and &#x2014;a surface area after aging at 1100&#xb0; C. for 2 hours equal to or greater than 30 m/g.

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Flemington, NJ, United States of America

John G Darab