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Vanadium-free catalyst for selective catalytic reduction and process for its preparation

A catalyst and reducing agent technology, applied in the field of catalysts, can solve problems such as difficult preparation, unsatisfactory use in motor vehicle activity and aging stability, and achieve cost-effective results

Active Publication Date: 2009-09-09
UMICORE AG & CO KG
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0013] Known vanadium- and tungsten-free SCR catalysts are sometimes of complex composition, difficult to prepare and / or do not meet the more stringent requirements for activity and aging stability for use in motor vehicles

Method used

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  • Vanadium-free catalyst for selective catalytic reduction and process for its preparation
  • Vanadium-free catalyst for selective catalytic reduction and process for its preparation
  • Vanadium-free catalyst for selective catalytic reduction and process for its preparation

Examples

Experimental program
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Effect test

Embodiment 1

[0075] A center sample was taken from the catalyst of Comparative Example 1 and sulfided in a furnace at 350°C for 48 hours in an atmosphere of 10 vol% oxygen, 10 vol% water, and 20 vol-ppm sulfur dioxide in nitrogen. The catalyst K1 obtained according to the invention was studied in a model gas.

[0076] figure 2 Shown are the nitrogen oxide conversions of catalyst K1 (●) according to the invention compared to comparative catalysts VK3 (◇, iron-zeolite-based), VK4 (□, vanadium-containing) and VK5 (×, Fe / W / ZrO 2 ) conversion rate of nitrogen oxides. Catalyst K1 according to the invention exhibits a higher conversion of nitrogen oxides in the SCR reaction over the entire temperature range than the comparative catalyst VK5 according to the prior art (which is also zeolite- and vanadium-free). Also surprisingly, in the temperature range from 300°C to 500°C, the nitrogen oxide conversion performance of the commercially available iron-zeolite-based catalyst VK3 was exceeded and...

Embodiment 2

[0078] A center sample was taken from the catalyst of Comparative Example 2 and sulfided in a furnace at 350°C for 48 hours in an atmosphere of 10 vol% oxygen, 10 vol% water, and 20 vol-ppm sulfur dioxide in nitrogen. The catalyst K2 obtained according to the invention was studied in a model gas.

[0079] image 3 The results of this study are shown and compared with the existing SCR catalysts VK3 (◇, based on iron-zeolite), VK4 (□, containing vanadium) and VK5 (×, Fe / W / ZrO 2 ) conversion rate of nitrogen oxides. The catalyst K2 according to the invention also exceeds the conversion performance of VK5 over the entire temperature range and the nitrogen oxide conversion performance of the iron-zeolite-based catalyst VK3 at temperatures above 300° C. The nitrogen oxide conversion performance of the vanadium-based comparative catalyst VK4 is fully achieved from 350° C. onwards.

Embodiment 3

[0081] A homogeneous cerium-zirconium mixed oxide with a ceria content of 48% by weight, based on its total amount, was activated for the SCR reaction by introducing tungsten. For this purpose, the amount of water which the homogeneous cerium-zirconium mixed oxide could absorb was first measured without the material losing its free-flowing properties. A tungsten compound having good water solubility in a proportion corresponding to 10% by weight of tungsten, based on the total weight of the activated cerium-zirconium mixed oxide to be produced, was dissolved in the corresponding amount of water. The tungsten-containing solution thus prepared was impregnated with the homogeneous cerium-zirconium mixed oxide until the pores were filled, and then stored in air in a furnace at 500° C. for 2 hours for thermal curing of the tungsten.

[0082] The activated cerium-zirconium mixed oxide thus obtained was suspended in water, ground and applied to a ceramic honeycomb element with a volu...

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Abstract

Selective catalytic reduction with ammonia or a compound which can be decomposed to give ammonia is a known process for removing nitrogen oxides from the exhaust gas of predominantly lean-burn internal combustion engines. Most of the vanadium-containing SCR catalysts used for this purpose to date are notable for a good conversion profile. However, the volatility of vanadium oxide at relatively high exhaust gas temperatures can lead to the emission of toxic vanadium compounds. Zeolite-based SCR catalysts, which are used especially in batchwise SCR systems, are a very costly solution to the problem. A process is presented, with which a homogeneous cerium-zirconium mixed oxide is activated for the SCR reaction by introducing sulfur and / or transition metal in a defined manner. The use of this process provides a highly active, ageing-stable SCR catalyst which constitutes a vanadium-free, inexpensive and high-performance alternative to the SCR catalysts to date and is suitable especially for use in motor vehicles.

Description

technical field [0001] The present invention relates to novel, vanadium-free catalysts for the selective catalytic reduction of nitrogen oxides using ammonia as reducing agent or compounds decomposing into ammonia, which are particularly suitable for use in exhaust gases from mainly lean-burn internal combustion engines in motor vehicles Remove nitrogen oxides. The invention further relates to a method for activating homogeneous cerium-zirconium mixed oxides for the selective catalytic reduction of nitrogen oxides. Background technique [0002] Emissions from motor vehicles can basically be divided into two categories. The term raw emissions thus denotes pollutant gases that are formed directly in the engine via the fuel combustion process and are already contained in the exhaust gas before passing through the exhaust gas cleaning system. Exhaust gas components that can form as by-products in exhaust gas cleaning systems are referred to as secondary emissions. [0003] Ex...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B01D53/94B01J35/04B01J37/02B01J23/00B01J23/10B01J27/04B01J23/24
CPCB01J23/10B01D2251/2062B01J27/04B01J23/30B01J37/0201B01D53/9418B01J23/888B01D2255/9155B01D2255/2063Y02T10/24B01D2255/20784B01D2255/20776B01D2255/407B01D2255/20769B01J23/002B01J23/24B01J37/0248B01J2523/00B01J2523/3706B01J2523/3712B01J2523/48Y02A50/20Y02T10/12B01J2523/69B01J2523/842B01J21/06B01D53/94
Inventor K·艾德尔曼N·泽格L·穆斯曼M·费弗尔G·杰斯克
Owner UMICORE AG & CO KG