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Catalysts, Systems and Methods Utilizing Non-Zeolitic Metal-Containing Molecular Sieves Having the CHA Crystal Structure

Inactive Publication Date: 2009-08-06
BASF CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0012]One embodiment of the present invention pertains to metal-loaded non-zeolitic molecular sieves having the CHA structure and their application in exhaust gas systems such as those designed to reduce nitrogen oxides. In specific embodiments, novel metal-loaded non-zeolitic molecular sieve catalysts having the CHA structure are provided which exhibit improved NH3 SCR of NOx. The non-zeolitic molecular sieve catalysts made in accordance with one or more embodiments of the present invention provide a catalyst material which exhibits excellent hydrothermal stability and high catalytic ability over a wide temperature range. When compared with other zeolitic catalysts that find application in this field, such as Fe Beta zeolites, non-zeolitic molecular sieve catalysts materials according to embodiments of the present invention offer improved low temperature activity and hydrothermal stability.

Problems solved by technology

Three-way catalysts cannot be used for the treatment of exhaust from lean burn and diesel engines because of the low NOx conversion in the presence of oxygen.
However, the applicability of HC SCR for diesel engines does not appear to be viable because most of catalysts suitable for HC-SCR show a very narrow temperature window where a useful NOx reduction can be obtained.
Unfortunately, it has been found that under harsh hydrothermal conditions, such as reduction of NOx from gas exhaust at temperatures exceeding 500° C., the activity of many metal-promoted zeolites, such as Cu and Fe versions of ZSM-5 and Beta, begins to decline.
This decline in activity is believed to be due to destabilization of the zeolite such as by dealumination and consequent loss of metal-containing catalytic sites within the zeolite.

Method used

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  • Catalysts, Systems and Methods Utilizing Non-Zeolitic Metal-Containing Molecular Sieves Having the CHA Crystal Structure
  • Catalysts, Systems and Methods Utilizing Non-Zeolitic Metal-Containing Molecular Sieves Having the CHA Crystal Structure
  • Catalysts, Systems and Methods Utilizing Non-Zeolitic Metal-Containing Molecular Sieves Having the CHA Crystal Structure

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0078]A SAPO-34 was prepared from a gel composition of 1.0 Al2O3:1.06 P2O5:1.08 SiO2:2.09 R:66H2O. A reaction mixture was formed by combining 1.54 kg of 85 wt. % orthophosphoric acid with a mixture of 920 g of a pseudoboehmite alumina (Catapal B) in 1.8 kg of deionized water. Then a further 1 kg of deionized water was added. The mixture was stirred until homogeneous. To this mixture was added a mixture containing 409 g of fumed silica (Aerosil-200), 1.16 kg morpholine (Aldrich, 99%) and 1.5 kg deionized water. The silica-containing mixture was added slowly with stirring and stirred until homogeneous. A further 2.5 kg of deionized water was added and the mixture was stirred until homogenous. The resulting gel was transferred to 5 gallon autoclave where it was aged at 38° C. for 24 hours. This was then heated in the autoclave for 24 hours at 200° C. The crystalline product was recovered via filtration and was washed to a conductivity lower than 200 μScm−1. Washing the crystalline prod...

example 2

[0087]The NH4+-form of SAPO-34 was formed using the same hydrothermal synthesis and ammonium exchange conditions detailed in example 1.

[0088]A Cu-SAPO34 powder catalyst was prepared by mixing 320 g of NH4+-form SAPO-34 with 1.28 L of a copper(II) acetate monohydrate solution of 0.5 M. The pH was between 4.0 and 4.3 during the reaction. An ion-exchange reaction between the NH4+-form SAPO-34 and the copper ions was carried out by agitating the slurry at 70° C. for 1 hour. The resulting mixture was then filtered, washed until the filtrate had a conductivity lower than 200 μScm−1, which indicated that substantially no soluble or free copper remained in the sample, and the washed sample was dried at 90° C. The obtained Cu-SAPO34 catalyst comprised CuO at 3.18% by weight. The BET surface area of this sample as prepared was 307 m2 / g. The BET surface area of this sample after aging at 850° C. in 10% steam for 6 hours was 303 m2 / g.

[0089]The slurry preparation, coating and SCR NOx evaluation ...

example 3

[0090]A SAPO-44 was prepared from a gel composition of 1.0 Al2O3:1.0 P2O5:1.0 SiO2:1.9 R:63 H2O. A reaction mixture was formed by combining 1.54 kg of 85 wt. % orthophosphoric acid with a mixture of 971 g of a pseudoboehmite alumina (Catapal B) in 4 kg of deionized water. The mixture was stirred until homogeneous. To this mixture was added a mixture containing 399.6 g of fumed silica (Aerosil-200), 1.25 kg cyclohexylamine (Aldrich, 99%) and 2.66 kg deionized water. The silica-containing mixture was added slowly with stirring and stirred until homogeneous. The resulting gel was transferred to 5 gallon autoclave where it was heated in the autoclave for 48 hours at 190° C. The crystalline product was recovered via filtration and was washed to a conductivity lower than 200 μScm−1. The sample was dried before calcining at 600° C. for 4 hours. The crystalline product had an X-ray powder diffraction pattern indicating that it was SAPO-44, a non-zeolitic molecular sieve with the chabazite t...

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Abstract

Catalysts comprising metal-loaded non-zeolitic molecular sieves having the CHA crystal structure, including Cu-SAPO-34, methods for preparing such catalysts, and systems and methods for treating exhaust gas incorporating such catalysts are disclosed. The catalysts can be used to remove nitrogen oxides from a gaseous medium across a broad temperature range and exhibit hydrothermal stability at high reaction temperatures.

Description

TECHNICAL FIELD[0001]Embodiments of the invention relate to catalysts comprising non-zeolitic metal containing molecular sieves that have the CHA framework or crystal structure, methods for their manufacture and use, and exhaust gas treatment systems containing such catalysts.BACKGROUND ART[0002]Several technologies are available for the reduction of nitrogen oxides (NOx) from the exhaust of automobile engines. Three Way Catalysts (TWC) are designed to remove NOx from the exhaust of vehicles equipped with a gasoline engine. On the three-way catalyst, the nitrogen oxides react with the unburned hydrocarbons or CO in such a way that the oxygen of NOx is consumed for the oxidation of the unburned hydrocarbons or CO yielding nitrogen, carbon dioxide and water. Three-way catalysts cannot be used for the treatment of exhaust from lean burn and diesel engines because of the low NOx conversion in the presence of oxygen.[0003]For diesel engines, there are two types of technologies for the re...

Claims

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Application Information

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IPC IPC(8): B01D53/56B01J23/72B01J23/42B01J29/072B01J27/182B01D53/34
CPCB01D53/9418Y02T10/24B01D53/9477B01D2251/2062B01D2251/2067B01D2255/1021B01D2255/20715B01D2255/20761B01D2255/50B01D2255/9207B01J29/005B01J29/85B01J35/04B01J37/0246B01J2229/186F01N3/2066F01N2610/02F01N2610/08Y02C20/10Y02T10/22B01D53/945Y02T10/12B01J35/56B01D2255/20738B01D2255/915B01D2255/504B01D2255/502B01J35/615B01J35/617
Inventor BULL, IVORKOERMER, GERALD S.MOINI, AHMADUNVERRICHT, SIGNE
Owner BASF CORP
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