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Process for producing metal oxide particle and exhaust gas purifying catalyst

A technology of oxides and catalysts, applied in metal/metal oxide/metal hydroxide catalysts, rare earth metal compounds, physical/chemical process catalysts, etc. to metal oxides, etc.

Inactive Publication Date: 2008-02-13
TOYOTA JIDOSHA KK
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0008] In the above case of providing a metal oxide carrier comprising a plurality of materials and utilizing a combination of their properties, the plurality of metal oxide particles may be mixed, but if so mixed, a good combination of properties of these metal oxides may not be obtained, Because the combined metal oxide particles each have a large size
[0009] In addition, basically uniform metal oxide particles can be obtained from a sol obtained by mixing a variety of colloidal particles, but a uniform mixture may not necessarily achieve the best results
[0010] For example, composite metal oxides obtained by uniformly mixing ceria and zirconia are known to have good OSC and heat resistance, but sometimes ceria cannot fully exert its performance of preventing sintering of precious metals such as platinum
That is, both ceria and zirconia are present on the surface of this composite metal oxide, so a part of the precious metal is supported on the zirconia part instead of the ceria part, and thus sintering cannot be prevented

Method used

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  • Process for producing metal oxide particle and exhaust gas purifying catalyst
  • Process for producing metal oxide particle and exhaust gas purifying catalyst
  • Process for producing metal oxide particle and exhaust gas purifying catalyst

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1～6 and comparative example 1～4

[0082] In the following test, the pH of the sol was measured using a pH meter in which a pH meter electrode was directly immersed in the sol.

Embodiment 1

[0084] In this example, metal oxide particles comprising a zirconia-rich core and a ceria-rich surface layer were obtained from an alkali-stabilized zirconia hydrosol and an acid-stabilized ceria hydrosol.

[0085] Alkali-stabilized zirconia hydrosol (isoelectric point: pH 3.5) and acid-stabilized ceria hydrosol (isoelectric point: pH 8.5) were mixed to make zirconia (ZrO 2 ) and cerium oxide (CeO 2 ) The molar ratio between them is 1:1. While stirring, nitric acid (HNO 3 ) aqueous solution, adjusting the pH to 3.0, thereby agglomerating the zirconia. Then, while stirring, ammonia water (NH 3 ) solution, the pH was adjusted to 10, thereby agglomerating cerium oxide.

[0086] The obtained mixed sol was dried at 120° C. for 24 hours, and the dried product was fired at 700° C. for 5 hours to obtain metal oxide particles.

Embodiment 2

[0088] In this example, metal oxide particles comprising a titania-rich core and a ceria-rich surface layer were obtained from an alkali-stabilized titania hydrosol and an acid-stabilized ceria hydrosol.

[0089] Mix alkali-stabilized titanium dioxide hydrosol (isoelectric point: pH 3.9) and acid-stabilized cerium oxide hydrosol (isoelectric point: pH 8.5) 2 ) and cerium oxide (CeO 2 ) The molar ratio between them is 1:1. While stirring, an aqueous solution of nitric acid was added dropwise to the mixed sol to adjust the pH to 3.0, thereby coagulating titanium dioxide. Then, while stirring, an aqueous ammonia solution was added dropwise to the mixed sol to adjust the pH to 10, thereby agglomerating cerium oxide. Subsequently, it was dried and fired in the same manner as in Example 1 to obtain metal oxide particles.

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Abstract

The present invention provides an exhaust gas purifying catalyst and a process for producing a metal oxide particle comprising multiple species of metal oxides and capable of satisfactorily exerting the properties of respective metal oxides. A process of the present invention comprises providing a sol containing at least a population of first colloid particles and a population of second colloid particles differing in the isoelectric point with each other; adjusting the pH of the sol to be closer to the isoelectric point of the population of first colloid particles than to the isoelectric point of the population of second colloid particles, thereby aggregating the population of first colloid particles; adjusting the pH of the sol, thereby aggregating the population of second colloid particles onto the population of first colloid particles aggregated; and drying and firing the obtained aggregate.

Description

technical field [0001] The present invention relates to a method of producing metal oxide particles, and more particularly, the present invention relates to a method of producing metal oxide particles preferably used as a catalyst for exhaust gas purification by loading a noble metal. In addition, the present invention relates to a catalyst for purifying exhaust gas used in an internal combustion engine. Background technique [0002] Exhaust gases from internal combustion engines such as automobile engines contain nitrogen oxides (NO x ), carbon monoxide (CO), hydrocarbons (HC), etc. By being able to oxidize CO and HC while reducing NO x Catalysts for exhaust gas purification can remove these substances. As a representative catalyst for exhaust gas purification, a three-way catalyst obtained by supporting noble metals such as platinum (Pt), rhodium (Rh) and palladium (Pd) on a porous metal oxide carrier such as γ-alumina is known. [0003] Metal oxide supports can be for...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B01J37/03B01D53/94B01J23/10B01J23/63C01G23/00B01J32/00C01F17/00C01G25/00
Inventor 三浦真秀
Owner TOYOTA JIDOSHA KK
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