Composite oxides or hydroxides comprising alumina and zirconia for automotive catalyst applications and method of manufacturing
An improved method for the formation of composite hydroxides or oxides comprising, on an oxide basis, Al 2 O 3 and ZrO 2 , and optionally CeO 2 , La 2 O 3 , Nd 2 O 3 , Pr 6 O 11 , Sm 2 O 3 , Y 2 O 3 , 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 ±1. The invention also relates to composites formed by this method comprising 20-70 wt % Al 2 O 3 , 10-77 wt % ZrO 2 , 0-34 wt % CeO 2 and 0-22 wt % REOs other than CeO 2 , and to composites per se comprising, on an oxide basis, 42-70 wt % Al 2 O 3 , 10-48 wt % ZrO 2 , 2-34 wt % CeO 2 and 0-9 wt % REOs other than CeO 2 and having the following properties after heating to 850° C. over four hours and holding at 850° C. for four hours then allowing to cool to ambient temperature: —a surface area after aging at 950° C. for 2 hours equal to or greater than 60 m 2 /g, and —a surface area after aging at 1100° C. for 2 hours equal to or greater than 30 m 2 /g.
1. A composite comprising, on an oxide basis, 42-70 wt % Al 2 O 3 , 10-48 wt % ZrO 2 , 2-34 wt % CeO 2 and 0-9 wt % REOs other than CeO 2 and having the following properties after heating to 850° C. over four hours and holding at 850° C. for four hours then allowing to cool to ambient temperature:
a surface area after aging at 950° C. for 2 hours equal to or greater than 60 m 2 /g, and
a surface area after aging at 1100° C. for 2 hours equal to or greater than 30 m 2 /g,
and having a sulfate ion content less than 0.05 percent by mass, a chloride ion content less than 200 ppm and a sodium ion content of less than 200 ppm, all on a dried oxide weight basis.
2. A composite as claimed in claim 1 comprising, on an oxide basis, 42-53 wt % Al 2 O 3 , 20-46 wt % ZrO 2 , 4-34 wt % CeO 2 and 0-7 wt % REOs other than CeO 2 and La 2 O 3 and having the following properties after heating to 850° C. over four hours and holding at 850° C. for four hours then allowing to cool to ambient temperature:
a surface area after aging at 950° C. for 2 hours equal to or greater than 70 m 2 /g, and
a surface area after aging at 1100° C. for 2 hours equal to or greater than 35 m 2 /g.
3. A composite comprising, on an oxide basis, 42-53 wt % Al 2 O 3 , 23-28 wt % ZrO 2 , 24-29 wt % CeO 2 and 1-6 wt % Pr 6 O 11 and having the following properties after heating to 850° C. over four hours and holding at 850° C. for four hours then allowing to cool to ambient temperature:
a surface area after aging at 950° C. for 2 hours equal to or greater than 70 m 2 /g,
a surface area after aging at 1000° C. for 4 hours equal to or greater than 56 m 2 /g, and
a surface area after aging at 1100° C. for 2 hours equal to or greater than 41 m 2 /g,
and having a sulfate ion content less than 0.05 percent by mass, a chloride ion content less than 200 ppm and a sodium ion content of less than 200 ppm, all on a dried oxide weight basis.
4. A composite as claimed in- claim 1 comprising, on an oxide basis, 45-53 wt % Al 2 O 3 , 20-27 wt % ZrO 2 , and 26-31 wt % CeO 2 and having the following properties after heating to 850° C. over four hours and holding at 850° C. for four hours then allowing to cool to ambient temperature:
a surface area after aging at 950° C. for 2 hours equal to or greater than 70 m 2 /g,
a surface area after aging at 1000° C. for 4 hours equal to or greater than 57 m 2 /g, and
a surface area after aging at 1100° C. for 2 hours equal to or greater than 43 m 2 /g.
5. A composite as claimed in- claim 1 , comprising, on an oxide basis, 44-50 wt % Al 2 O 3 , 35-43 wt % ZrO 2 , and 12-16 wt % CeO 2 and having the following properties after heating to 850° C. over four hours and holding at 850° C. for four hours then allowing to cool to ambient temperature:
a surface area after aging at 950° C. for 2 hours equal to or greater than 75 m 2 /g, and
a surface area after aging at 1100° C. for 2 hours equal to or greater than 41 m 2 /g.
6. A composite as claimed in claim 1 comprising, on an oxide basis, 60-70 wt % Al 2 O 3 , 10-15 wt % ZrO 2 , 10-15 wt % CeO 2 and 1-7 wt % REOs other than CeO 2 and having the following properties after heating to 850° C. over four hours and holding at 850° C. for four hours then allowing to cool to ambient temperature:
a surface area after aging at 950° C. for 2 hours equal to or greater than 75 m 2 /g,
a surface area after aging at 1000° C. for 4 hours equal to or greater than 70 m 2 /g,
a surface area after aging at 1050° C. for 2 hours equal to or greater than 65 m 2 /g, and
a surface area after aging at 1100° C. for 2 hours equal to or greater than 55 m 2 /g.
7. A composite comprising, on an oxide basis, 42-70 wt % Al 2 O 3 , 10-48 wt % ZrO 2 , 2-34 wt % CeO 2 and 1-9 wt % rare earth oxides (REOs) other than CeO 2 , where REOs correspond to
one or more of Nd 2 O 3 , Pr 6 O 11 , Sm 2 O 3 , or other rare earth oxide, other than La 2 O 3 or Y 2 O 3 ,
and having the following properties after heating to 850° C. over four hours and holding at 850° C. for four hours then allowing to cool to ambient temperature:
a surface area after aging at 950° C. for 2 hours equal to or greater than 60 m 2 /g, and
a surface area after aging at 1100° C. for 2 hours equal to or greater than 30 m 2 /g,
and having a sulfate ion content less than 0.05 percent by mass, a chloride ion content less than 200 ppm and a sodium ion content of less than 200 ppm, all on a dried oxide weight basis.