Method for treating gas containing nitrogen oxides (NOx), using composition comprising zirconium, cerium and niobium as catalyst

A nitrogen oxide, cerium oxide technology, applied in catalyst activation/preparation, physical/chemical process catalyst, metal/metal oxide/metal hydroxide catalyst, etc., to achieve the effect of stabilizing the specific surface area

Inactive Publication Date: 2014-04-02
RHODIA OPERATIONS SAS +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Thus, the catalytic systems currently used to practice this method are generally only effective at temperatures above 250 °C

Method used

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  • Method for treating gas containing nitrogen oxides (NOx), using composition comprising zirconium, cerium and niobium as catalyst
  • Method for treating gas containing nitrogen oxides (NOx), using composition comprising zirconium, cerium and niobium as catalyst

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0075] This example relates to the preparation of compositions based on oxides of cerium, zirconium and niobium with corresponding mass proportions of 18%, 72% and 10%.

[0076] Ammonium niobium(V) oxalate solution was prepared by thermally dissolving 192 g of ammonium niobium(V) oxalate in 300 g of deionized water. This solution was kept at 50°C. The concentration of this solution is Nb 2 o 5 Expressed as 14.2%. Then the mixed oxide powder of cerium and zirconium (mass composition CeO 2 / ZrO 2 20%-80%, the specific surface area after calcination at 800°C for 4 hours is 62m 2 / g) impregnated with this solution until the pore volume is saturated.

[0077] The impregnated powder was then calcined at 800°C for 4 hours.

Embodiment 2

[0079] This example relates to the preparation of compositions based on oxides of cerium, zirconium and niobium with corresponding mass proportions of 19%, 74% and 7%.

[0080] Ammonium niobium(V) oxalate solution was prepared by thermally dissolving 134 g of ammonium niobium(V) oxalate in 300 g of deionized water. This solution was kept at 50°C. The concentration of this solution is Nb 2 o 5 Expressed as 9.9%. The same mixed oxide powder of cerium and zirconium as in Example 1 was then impregnated with this solution. The impregnated powder was then calcined at 800°C for 4 hours.

Embodiment 4

[0090] This example describes the catalytic performance of the compositions of the above examples in SCR catalysis. These properties were evaluated under the following conditions.

[0091] In the first series of measurements, the composition used was the composition obtained directly from the synthesis described in the preceding examples, ie a composition that had been calcined at 800° C. for 4 hours.

[0092] In the second series of measurements, the composition used was that of the preceding examples, but after an additional calcination in both cases at 900° C. and 1000° C. for 2 hours.

[0093] The compositions were then evaluated by catalytic tests. In this test, a synthesis gas mixture (Table 2) representative of the catalytic process was passed (30 L / h) through the composition (90 mg).

[0094] Table 2

[0095]Composition of a representative mixture

[0096] NH 3

500vpm

NO

500vpm

O 2

13vol%

h 2 o

5vol%

N 2

...

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Abstract

The invention relates to a method for treating a gas containing nitrogen oxides (NOx), in which an NOx-reduction reaction is carried out using a nitrogen-containing reducing agent, which invention is characterized in that the catalyst used for the reduction reaction is a catalytic system containing a composition comprising zirconium, cerium and niobium in the following percentages by weight, expressed in terms of the weight of oxide: 10-50% of cerium, 5-20% of niobium and the remainder consisting of zirconium.

Description

technical field [0001] The present invention relates to a method for treating gases containing nitrogen oxides (NOx) using a composition based on zirconium, cerium and niobium as a catalyst. Background technique [0002] Motor vehicle engines are known to emit nitrogen oxides (NOx) containing gases which are harmful to the environment. These oxides therefore need to be treated to convert them to nitrogen. [0003] A known method for this treatment is the SCR method (Selective Catalytic Reduction), in which NOx is reduced by ammonia or ammonia precursors such as urea. [0004] The SCR method makes possible efficient treatment of the gas, but its efficiency at low temperatures still needs to be improved. Thus, the catalytic systems currently used to practice this method are generally only effective at temperatures above 250°C. It would therefore be advantageous to have a catalyst capable of significant activity at temperatures of about 250°C. [0005] Catalysts are therefo...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B01D53/94B01J23/00B01J23/10F01N3/10B01J21/06B01J23/20
CPCB01D2255/20715B01D2251/2062B01J2229/37B01J29/06Y02T10/24F01N2610/02B01J37/0203B01J2229/32B01D2251/2067B01J35/0006B01J21/066F01N3/206B01J29/48B01D2255/50B01J23/10B01J37/0009B01J23/20B01J37/04B01J2229/16B01J29/85B01J35/1014B01D2255/207F01N3/10B01D53/9418B01D2255/2065B01J29/78F01N3/2066B01J2229/36B01D2258/012Y02T10/12Y02A50/20B01D53/56B01D53/94B01J21/06B01J23/63
Inventor L·比松J·埃尔南德兹R·M·若热科埃略马克斯E·罗阿尔M·博尔图D·J·哈里斯C·约内斯
Owner RHODIA OPERATIONS SAS
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