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NOx purification triple-effect catalyst for working condition of excessive equivalent combustion intermittent oxygen and preparation method thereof

A three-way catalyst, intermittent technology, applied in the field of automobile exhaust gas purification, can solve the problems of restoring TWC oxygen storage capacity, NOx leakage, etc.

Inactive Publication Date: 2019-09-06
昆明贵研催化剂有限责任公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

When the engine is restarted, the TWC may be in a cold state (<250°C), and the oxygen storage capacity of the TWC cannot be effectively restored by the short-term rich combustion of the engine.
Therefore, the TWC cannot effectively convert the NOx in the exhaust gas after the engine is restarted (the air-fuel ratio fluctuates with a small range and high frequency around the equivalent), resulting in NOx leakage in the exhaust gas

Method used

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  • NOx purification triple-effect catalyst for working condition of excessive equivalent combustion intermittent oxygen and preparation method thereof
  • NOx purification triple-effect catalyst for working condition of excessive equivalent combustion intermittent oxygen and preparation method thereof
  • NOx purification triple-effect catalyst for working condition of excessive equivalent combustion intermittent oxygen and preparation method thereof

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0027] Example 1: Preparation of NOx storage catalytic material and application of the first coating

[0028] with barium acetate (BaCO 3 ), potassium carbonate (K 2 CO 3 ) as the precursor, ammonium carbonate ((NH 4 ) 2 CO 3 ) is a precipitating agent, and the precipitation method is used to prepare K 2 CO 3 -BaCO 3 -Al 2 o 3 powder, dried at 150°C and calcined at 700°C for 2 hours, the obtained K 2 CO 3 -BaCO 3 -Al 2 o 3 K in powder 2 CO 3 、BaCO 3 The mass percentages are 8% and 24% respectively. with K 2 In terms of O and BaO, the mass percentages are 5.45% and 18.65% respectively.

[0029] K 2 CO 3 -BaCO 3 -Al 2 o 3 and CeO 2 The powder is mixed at a mass ratio of 8:2, added with deionized water to make slurry, and the pH value is adjusted to 5-7 by nitric acid.

[0030] Add tetraammonium platinum acetate, the platinum loading is 50g / ft 3 .

[0031] Adjust the solid content of the slurry and the grinding particle size to an appropriate value to ...

Embodiment 2

[0036] Embodiment 2: Preparation of three-way catalytic material and second coating coating

[0037] The rare earth oxide, lanthanum-modified alumina and low-temperature alumina are mixed at a mass ratio of 5:4.5:0.5, and deionized water is added to make slurry.

[0038] Add palladium nitrate and rhodium nitrate aqueous solution, palladium and rhodium loading are 2g / ft respectively 3 , 8g / ft 3 .

[0039] Adjust the pH value, solid content, and abrasive particle size of the slurry to an appropriate value to ensure the firmness of the coating and the control of the coating height, and apply it on the surface of the coating of the NOx storage catalytic material to form the second layer, as the outer layer, the coating amount 100g / L.

[0040] The composition of the components in the second coating material is specified in Table 2.

[0041] Table 2

[0042] Coating Composition PD Rh CeO 2

[0043] Dry at 180°C and bake at 500°C for 2 hours.

Embodiment 3

[0044] Embodiment 3: Mixed coating of multiple catalytic materials

[0045] The NOx storage catalytic material (dry material) in Example 1, the three-way catalytic material (dry material) in Example 2, and the Pd modified molecular sieve material (dry material) were mixed at a mass ratio of 5:4:1.

[0046] The Pd modified molecular sieve material can be prepared by impregnation method, ion exchange method and other methods, and the loading amount (mass percentage) of Pd is 0.5%.

[0047] The catalytic material was dried at 150°C and calcined at 500°C for 2 hours to obtain a dry material.

[0048] The purpose of using dry material in practice is to prevent the active precious metals in different catalytic materials from migrating to the surface of other materials during the slurry mixing process.

[0049] Mix various catalytic materials fully and evenly by means of rubber mill, adjust the pH value, solid content, and grinding particle size of the slurry to a suitable value, an...

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Abstract

The invention discloses a NOx purification triple-effect catalyst for the working condition of excessive equivalent combustion intermittent oxygen. The catalyst comprises an active carrier oxide and aNOx storage catalytic material coating; the NOx storage catalytic material coating is selected from a palladium modified molecular sieve or a supported type palladium catalyst or the mixture of the ttriple-triple-effect catalytic material and one of the palladium modified molecular sieve and the supported type palladium catalyst. The NOx storage catalytic material is introduced in the catalyst ina mode of physical mixing, layering or partitioning coating, NOx is stored when exhaust of an engine is diluted and the catalyst is in the oxygen storage saturation state, NOx is released and converted when the normal oxygen storage capability of the catalyst is recovered and Nix can be effectively converted, and therefore the removal rate of NOx in automobile tail gas is increased. The inventionfurther provides a preparation method of the catalyst.

Description

technical field [0001] The invention relates to the technical field of automobile tail gas purification, in particular to a three-way catalyst for NOx purification and a preparation method thereof under the condition of intermittent excessive oxygen in equivalent combustion. Background technique [0002] The conventional three-way catalyst (TWC) is suitable for the simultaneous elimination of nitrogen oxides (NOx), carbon monoxide (CO), and hydrocarbons (HC) under stoichiometric or near-stoichiometric air-fuel ratio conditions. The engine equivalent operation mode is to complete the operation when the air-fuel ratio fluctuates around the equivalent with small amplitude and high frequency. When the exhaust gas is relatively rich, the conversion rate of CO and HC will decrease; and when the exhaust gas is relatively lean, the conversion rate of NOx will decrease sharply, so the exhaust gas conversion rate of TWC will fluctuate with the high frequency change of air-fuel ratio ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B01J29/068F01N3/20B01D53/94B01D53/56B01D53/62B01D53/72
CPCB01D53/945B01J29/068B01J2229/18F01N3/20Y02A50/20Y02T10/12
Inventor 杨冬霞徐立峰贺小昆王成雄杜君臣冯丰陆炳
Owner 昆明贵研催化剂有限责任公司
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