Oxygen storage materials

Abstract

The present invention is concerned with oxygen storage materials. In particular an oxygen storage material (OSM) is proposed which comprises a certain mixed oxide as the oxygen storage component. The oxygen storage material can be used in conventional manner in three-way catalysts or NOx-storage catalysts for example.

Claims

1. Catalytic oxygen storage material comprising a catalytically active metal selected from the group consisting of Cu, Ag, Au, Pt, Pd, Rh, Ru, Ir and mixtures thereof and further a binary, ternary or higher mixed oxide consisting of the formula
(M1).sub.a(M2).sub.b(M3).sub.c(M4).sub.d(M5).sub.e(M6)f(M7).sub.gO.sub.x wherein 0a, b, c, d, e, f, g20 and x adapts a value to compensate the positive charge originating from the metal cations M1-M7 being selected from the group consisting of Fe, Mn, V, W, Nb, Ta, and Mo; and wherein the mixed oxide is supported on a high surface area refractory metal oxide support having a surface area of at least 50 m.sup.2/g.

2. Oxygen storage material according to claim 1, wherein a is from >0-20, b is from >0-20, c is from 0-5 and d, e, f, g is from 0-5.

3. Oxygen storage material according to claim 1, wherein M1-M5 are selected from the group consisting of Fe, Mn, V, Nb and W.

4. Oxygen storage material according to claim 1, wherein the storage capacity of the material is at least 8.000 g O.sub.2/mmol oxygen storage component.

5. Three-way catalyst, cDPF, oxidation catalyst or NOx-storage catalyst comprising the oxygen storage material according to claim 1.

6. Exhaust treatment system comprising one or more of the catalysts of claim 5.

7. Process for treating exhaust gas from combustion engines, wherein the exhaust gas is brought into contact with one or more of the catalysts of claim 5 under conditions effective to mitigate noxious pollutants in the exhaust.

Description

EXAMPLES

Example 1

1 w % Pd/10 w % CeO2 on Al2O3 (Comparative Sample)

(1) Preparation/Calcination

(2) The catalyst material was prepared by pore volume impregnation of a Al.sub.2O.sub.3 powder with a mixture of an aqueous solution of Pd(NO.sub.3).sub.2 and (NH.sub.4).sub.2Ce(NO.sub.3).sub.6. After drying, the sample was calcined in static air for 4 h at 700 C.

Example 2

1 w % Pd/10 w % VNbO5 on Al2O3

(3) The catalyst material was prepared by pore volume impregnation of a Al.sub.2O.sub.3 powder with a mixture of an aqueous solution of Pd(NO.sub.3).sub.2, Vanadyloxalate and Ammonium Niobium oxalate. After drying, the sample was calcined in static air for 4 h at 700 C.

Example 3

1 w % Pd/10 w % FeVO4 supported on Al2O3

(4) The catalyst material was prepared by pore volume impregnation of a Al.sub.2O.sub.3 powder with a mixture of an aqueous solution of Pd(NO.sub.3).sub.2, Vanadyloxalate and Iron nitrate. After drying, the sample was calcined in static air for 4 h at 700 C.

(5) Referring to FIG. 1 and Table 2 the redox activity characteristics are compared for the samples 1 w % Pd/10 w % CeO.sub.2 on Al.sub.2O.sub.3 (comparative example), 1 w % Pd/10 w % VNbO.sub.5 on Al.sub.2O.sub.3 and 1 w % Pd/10 w % FeVO.sub.4 supported on Al.sub.2O.sub.3. It is seen that the oxygen storage materials described in this patent show enhanced properties compared to the reference material containing CeO.sub.2. This is further demonstrated in Table 2 where the maxima in reduction temperatures are recorded as well as the relative oxygen storage capacity (in %), the absolute hydrogen uptake capacity (in g H.sub.2/mmol oxygen storage component), and the absolute oxygen storage capacity (in g O.sub.2/mmol oxygen storage component).

(6) TABLE-US-00002 TABLE 2 Compilation of the data obtained from H2 TPR absolute absolute hydrogen oxygen uptake storage relative capacity capacity oxygen (g H.sub.2/mmol (g O.sub.2/mmol H.sub.2 TPR storage oxygen oxygen Peak capacity storage storage position, (%); component); component); Material C. RT - 700 C. RT - 700 C. RT - 700 C. Redox reaction Example 1 107 31 306 2448 CeO.sub.2 .fwdarw. Ce.sub.2O.sub.3 (comparative +IV .fwdarw. +III example) Example 2 109 81 1617 12936 VNbO.sub.5 .fwdarw. VNbO.sub.3 +V/+V .fwdarw. +III/+III Example 3 95 68 2048 16384 FeVO.sub.4 .fwdarw. Fe.sub.2V.sub.2O.sub.5 +III/+V .fwdarw. +II/+III