CN100391599C - CeO2 based composite oxide coating supported Pd catalyst and preparation method thereof - Google Patents

Abstract

The invention relates to a _CeO2- based composite oxide coating-loaded Pd catalyst and a preparation method thereof. The purpose of the present invention is to provide a method for the existing Al ₂ O ₃ coatings with poor thermal stability, easy to react with carriers or additives to form spinel compounds, and Al ₂ O ₃ coatings to fall off easily. A catalytic combustion catalyst with a _CeO2- based composite oxide coating on a carrier and a preparation method thereof. The catalyst comprises a bulky cordierite honeycomb ceramic carrier substrate, a CeO ₂ -based composite oxide coating and a noble metal active component Pd, wherein the CeO ₂ -based composite oxide coating and the noble metal active component are both prepared by an impregnation method. The catalyst has the advantages of firm bonding between the coating and the honeycomb ceramic carrier skeleton, and the coating is not easy to fall off during use, and the catalyst has the characteristics of high catalytic activity, good high temperature resistance, and high effective utilization rate of noble metal active components.

Description

CeO2 based composite oxide coating supported Pd catalyst and preparation method thereof

technical field

The invention relates to a _CeO2- based composite oxide coating-loaded Pd catalyst and a preparation method thereof, in particular to a catalyst for catalytic combustion and purification of organic waste gas and a preparation method thereof.

Background technique

Among the purification and treatment methods of organic waste gas, catalytic combustion technology, as a simple and practical organic waste gas purification technology, has received more and more attention. Catalytic combustion is an effective technology for purifying organic waste gas, and its core is a catalytic combustion catalyst. Therefore, the development of catalytic combustion catalysts with excellent performance has become the key to the development of this technology.

Most of the existing catalytic combustion catalysts adopt a honeycomb structure, that is, cordierite honeycomb ceramics are used as a substrate, and a coating is coated on it as a carrier, and then the active components are loaded. If the bonding strength between the carrier and the coating is low, the coating will crack and fall off, which will directly affect the catalytic activity. Al ₂ O ₃ coating is commonly used as the second carrier in existing catalysts, because Al ₂ O ₃ can provide a higher specific surface and can support other metal oxides and noble metals. However, Al ₂ O ₃ has poor thermal stability and affects the catalytic performance of the catalyst, so other additives are usually added to stabilize the Al ₂ O ₃ coating, such as ZrO ₂ , MgO, La ₂ O ₃ , CeO ₂ and so on. For example, in the disclosed method of Chinese Patent Document Patent No. 01133374.X, the coating is composed of Al ₂ O ₃ , TiO ₂ , CeO ₂ and ZrO ₂ ; in the disclosed method of Chinese Patent Document Patent Application No. 02133123.5, the coating is composed of The composition of Al ₂ O ₃ , SiO ₂ and alkaline earth metals all improve the high temperature resistance of the catalyst. However, the bonding strength between the added oxide additive powder and the Al ₂ O ₃ thin layer is not high, and it is easy to fall off. At the same time, the preparation process of the catalyst is complicated, and the solid phase reaction is prone to occur at high temperature to form spinel (AB ₂ O ₄ ) compounds, reducing the catalytic performance.

Contents of the invention

The purpose of the present invention is to solve the defects of existing Al ₂ O ₃ coatings such as poor thermal stability, easy reaction with carriers or additives to form spinel compounds, and easy peeling off of Al ₂ O ₃ coatings, and utilize CeO ₂ based composite oxidation High oxygen storage performance and high-temperature sintering resistance of the object, a kind of catalyst and its preparation method of loading _CeO2- based composite oxide coating on the honeycomb ceramic carrier are provided, the catalyst of the present invention has the coating and the honeycomb ceramic carrier skeleton combined firmly, The coating is not easy to fall off during use, and has the advantages of high effective utilization of precious metals, good catalytic performance and high temperature resistance.

_The catalytic combustion catalyst of the present invention is a honeycomb ceramic type catalytic combustion catalyst. There is _a coating on the surface of the honeycomb ceramic. The mass percentage of the substance coating is 5% to 30% of the honeycomb ceramic carrier, and the ratio of the amount of _CeO2 to the third subgroup metal oxide in the mixed oxide coating (calculated as metal) is 9:1 to 1 : 9, the third subgroup metal oxide adopts one or a mixture of La ₂ O ₃ , Sm ₂ O ₃ and Y ₂ O ₃ ; the catalyst uses Pd loaded on the coating as the active component, and its The loading amount is 0.1-2.0g Pd per liter of catalyst.

The preparation method of catalytic combustion catalyst of the present invention is:

(1) Preparation and coating of coating liquid

① Add HNO ₃ to a certain amount of the third subgroup metal oxide, mix with Ce(NO ₃ ) ₃ and organic acid or ethylene glycol or a mixture of the two, add an appropriate amount of water, and stir evenly to obtain a coating solution . Wherein, the total substance amount of the organic acid or ethylene glycol or the mixture of the two used is 0.2～4 times of the total _substance amount of metal ions in the composite oxide coating;

② Immerse the honeycomb ceramic carrier in the coating solution and take it out to remove the coating solution remaining in the pores of the honeycomb ceramic carrier;

③ Place the honeycomb ceramics in ② to dry for 0.5-24 hours, and then dry at 80-120°C for 0.5-12 hours;

④ Baking the honeycomb ceramics in ③ at 400-1000°C for 0.5-2 hours;

⑤Repeat steps ②~④ for two to four times until the coating solution is fully impregnated and adsorbed, and finally baked at 400~1000°C for 1~5 hours to make a honeycomb ceramic carrier with coating.

(2) Impregnation of active metal components, carrying an appropriate amount of noble metal component Pd by impregnation, then drying at 80-120°C for 0.5-12 hours, and roasting at 400-1000°C for 1-5 hours, and finally the finished catalyst of the present invention is obtained .

The _CeO2- based composite oxide coating-loaded Pd catalyst prepared by the invention has the characteristics that the coating is firmly combined with the surface of the honeycomb ceramic carrier and is not easy to fall off during use. At the same time, the catalyst of the present invention has high catalytic activity, thermal stability, anti-sintering and anti-poisoning properties, adopts the impregnation method to support the noble metal active components, and has the advantages of strong adhesion, high dispersion and high effective utilization rate of the noble metal active components.

Detailed ways

The present invention will be further described below in conjunction with the examples, but the present invention is not limited to these examples.

Example 1

Weigh 10.67g Ce(NO ₃ ) ₃ ·6H ₂ O and 7.98g citric acid, mix them and add appropriate amount of deionized water to dissolve to obtain a coating solution. Dip the cordierite honeycomb ceramics with a size of 50mm×25mm×40mm, a porosity of 195cell/in ² , and a mass of 31.41g into the coating liquid, take it out, and blow out the residual liquid in the honeycomb channel. At this time, there is still part of the coating liquid remaining , Air the cordierite honeycomb ceramics at room temperature to 50°C until the surface is dry, then dry at 120°C for 1 hour, and then bake in a muffle furnace at 500°C for 1 hour. Repeat the above process 2 to 3 times until the coating solution is completely soaked and adsorbed, and finally baked in a muffle furnace at 500°C for 4 hours to obtain a CeO ₂ coating.

Prepare 100 mL of H ₂ PdCl ₄ aqueous solution with a concentration of 8.9 g Pd (1 g/L)/L solution as the impregnation solution for the noble metal active component. Measure 5.6mL of H ₂ PdCl ₄ aqueous solution and add deionized water to dilute the honeycomb ceramic carrier just enough to immerse the honeycomb ceramic carrier, then dip the coated honeycomb ceramic carrier into the diluted solution, shake it in a constant temperature water bath, take it out, and blow out the holes. The residual solution was then dried at 120°C in air for 1 hour, and then calcined at 500°C in air for 4 hours to obtain a Pd(1g/L)/CeO ₂ catalytic combustion catalyst.

Example 2

Weigh 0.57g Y ₂ O ₃ , add HNO ₃ , mix with 9.16g Ce(NO ₃ ) ₃ ·6H ₂ O and 5.35g citric acid, add appropriate amount of deionized water, and stir evenly to obtain a coating solution. Dip the cordierite honeycomb ceramics with a size of 50mm×25mm×40mm, a porosity of 195cell/in ² , and a mass of 31.40g into the coating solution, take it out, blow out the residual liquid in the honeycomb channels, and heat the cordierite honeycomb ceramics at room temperature to 50 ℃ until the surface is dry, then dried at 120℃ for 1 hour, and then fired in a muffle furnace at 500℃ for 1 hour. Repeat the above process for 2 to 3 times until the coating solution is completely impregnated and adsorbed, and finally baked in a muffle furnace at 500°C for 4 hours to obtain a Ce _0.8 Y _0.2 O _1.9 coating.

Measure 5.6mL of H ₂ PdCl ₄ aqueous solution and add deionized water to dilute the honeycomb ceramic carrier just enough to immerse the honeycomb ceramic carrier, then dip the coated honeycomb ceramic carrier into the diluted solution, shake it in a constant temperature water bath, take it out, and blow out the holes. The remaining solution was then dried in air at 120°C for 1 hour, and then calcined in air at 500°C for 4 hours to obtain a Pd(1g/L)/Ce _0.8 Y _0.2 O _1.9 catalyst.

Example 3

Weigh 0.98g Sm ₂ O ₃ and add HNO ₃ , mix with 9.73g Ce(NO ₃ ) ₃ ·6H ₂ O and 4.93g citric acid, add appropriate amount of deionized water, and stir evenly to obtain a coating solution. Dip the cordierite honeycomb ceramics with a size of 50mm×25mm×40mm, a porosity of 195cell/in ² , and a mass of 31.23g into the coating solution, take it out, blow out the residual liquid in the honeycomb channels, and heat the cordierite honeycomb ceramics at room temperature to 50 ℃ until the surface is dry, then dried at 120℃ for 1 hour, and then fired in a muffle furnace at 500℃ for 1 hour. Repeat the above process 2 to 3 times until the coating solution is completely soaked and adsorbed, and finally baked in a muffle furnace at 500°C for 4 hours to form a Ce _0.8 Sm _0.2 O _1.9 coating.

Measure 5.6mL of H ₂ PdCl ₄ aqueous solution and add deionized water to dilute the honeycomb ceramic carrier just enough to immerse the honeycomb ceramic carrier, then dip the coated honeycomb ceramic carrier into the diluted solution, shake it in a constant temperature water bath, take it out, and blow out the holes. The remaining solution was then dried in air at 120°C for 1 hour, and then calcined in air at 500°C for 4 hours to obtain a Pd(1g/L)/Ce _0.8 Sm _0.2 O _1.9 catalyst.

Example 4

Weigh 0.91g La ₂ O ₃ , add HNO ₃ , mix with 9.73g Ce(NO ₃ ) ₃ ·6H ₂ O and 5.88g citric acid, add appropriate amount of deionized water, and stir evenly to obtain a coating solution. Dip the cordierite honeycomb ceramics with a size of 50mm×25mm×40mm, a porosity of 195cell/in ² , and a mass of 33.46g into the coating solution, take it out, blow out the residual liquid in the honeycomb channels, and heat the cordierite honeycomb ceramics at room temperature to 50 ℃ until the surface is dry, then dried at 120℃ for 1 hour, and then fired in a muffle furnace at 500℃ for 1 hour. Repeat the above process for 2 to 3 times until the coating solution is completely impregnated and adsorbed, and finally baked in a muffle furnace at 500°C for 4 hours to obtain a Ce _0.8 La _0.2 O _1.9 catalyst coating.

Measure 5.6mL of H ₂ PdCl ₄ aqueous solution and add deionized water to dilute the honeycomb ceramic carrier just enough to immerse the honeycomb ceramic carrier, then dip the coated honeycomb ceramic carrier into the diluted solution, shake it in a constant temperature water bath, take it out, and blow out the holes. The remaining solution was then dried in air at 120°C for 1 hour, and then calcined in air at 500°C for 4 hours to obtain a Pd(1g/L)/Ce _0.8 La _0.2 O _1.9 catalyst.

Example 5

Weigh 0.89g La ₂ O ₃ and add HNO ₃ , mix with 9.44g Ce(NO ₃ ) ₃ ·6H ₂ O and 1.69g ethylene glycol, add appropriate amount of deionized water, and stir evenly to obtain a coating solution. Dip the cordierite honeycomb ceramics with a size of 50mm×25mm×40mm, a porosity of 195cell/in ² , and a mass of 32.58g into the coating solution, take it out, blow out the residual liquid in the honeycomb channels, and heat the cordierite honeycomb ceramics at room temperature to 50 ℃ until the surface is dry, then dried at 120℃ for 1 hour, and then fired in a muffle furnace at 500℃ for 1 hour. Repeat the above process 2 to 3 times until the coating solution is completely soaked and adsorbed, and finally baked in a muffle furnace at 500°C for 4 hours to obtain a Ce _0.8 La _0.2 O _1.9 coating.

Measure 5.6mL of H ₂ PdCl ₄ aqueous solution and add deionized water to dilute the honeycomb ceramic carrier just enough to immerse the honeycomb ceramic carrier, then dip the coated honeycomb ceramic carrier into the diluted solution, shake it in a constant temperature water bath, take it out, and blow out the holes. The remaining solution was then dried in air at 120°C for 1 hour, and then calcined in air at 500°C for 4 hours to obtain a Pd(1g/L)/Ce _0.8 La _0.2 O _1.9 catalyst.

Example 6

Weigh 0.83g La ₂ O ₃ and add HNO ₃ , mix with 9.17g Ce(NO ₃ ) ₃ ·6H ₂ O and 5.36g citric acid, add appropriate amount of deionized water, and stir evenly to obtain a coating solution. Dip the cordierite honeycomb ceramics with a size of 50mm×25mm×40mm, a porosity of 195cell/in ² , and a mass of 32.56g into the coating solution, take it out, blow out the residual liquid in the honeycomb channel, and heat the cordierite honeycomb ceramics at room temperature to 50 ℃ until the surface is dry, then dried at 120℃ for 1 hour, and then fired in a muffle furnace at 500℃ for 1 hour. Repeat the above process 2 to 3 times until the coating solution is completely soaked and adsorbed, and finally baked in a muffle furnace at 500°C for 4 hours to obtain a Ce _0.8 La _0.2 O _1.9 coating.

Measure 5.6mL of H ₂ PdCl ₄ aqueous solution and add deionized water to dilute the honeycomb ceramic carrier just enough to immerse the honeycomb ceramic carrier, then dip the coated honeycomb ceramic carrier into the diluted solution, shake it in a constant temperature water bath, take it out, and blow out the holes. The remaining solution was then dried in air at 120°C for 1 hour, and then calcined in air at 900°C for 4 hours to obtain a Pd(1g/L)/Ce _0.8 La _0.2 O _1.9 catalyst.

Example 7

Weigh 0.83g La ₂ O ₃ , add HNO ₃ , mix with 9.16g Ce(NO ₃ ) ₃ ·6H ₂ O and 5.35g citric acid, add appropriate amount of deionized water, and stir evenly to obtain a coating solution. Dip the cordierite honeycomb ceramics with a size of 50mm×25mm×40mm, a porosity of 195cell/in ² , and a mass of 31.46g into the coating solution, take it out, blow out the residual liquid in the honeycomb channels, and heat the cordierite honeycomb ceramics at room temperature to 50 ℃ until the surface is dry, then dried at 120℃ for 1 hour, and then fired in a muffle furnace at 500℃ for 1 hour. Repeat the above process 2 to 3 times until the coating solution is completely soaked and adsorbed, and finally baked in a muffle furnace at 500°C for 4 hours to obtain a Ce _0.8 La _0.2 O _1.9 coating.

Measure 5.6mL of H ₂ PdCl ₄ aqueous solution and add deionized water to dilute the honeycomb ceramic carrier just enough to immerse the honeycomb ceramic carrier, then dip the coated honeycomb ceramic carrier into the diluted solution, shake it in a constant temperature water bath, take it out, and blow out the holes. The remaining solution was then dried in air at 120°C for 1 hour, and then calcined in air at 1050°C for 4 hours to obtain a Pd(1g/L)/Ce _0.8 La _0.2 O _1.9 catalyst.

Example 8

Weigh 0.84g La ₂ O ₃ and add HNO ₃ , mix with 9.30g Ce(NO ₃ ) ₃ ·6H ₂ O and 5.44g citric acid, add appropriate amount of deionized water, and stir evenly to obtain a coating solution. Dip the cordierite honeycomb ceramics with a size of 50mm×25mm×40mm, a porosity of 195cell/in ² , and a mass of 31.96g into the coating liquid, take it out, blow out the residual liquid in the honeycomb channels, and heat the cordierite honeycomb ceramics at room temperature to 50 ℃ until the surface is dry, then dried at 120℃ for 1 hour, and then fired in a muffle furnace at 500℃ for 1 hour. Repeat the above process 2 to 3 times until the coating solution is completely soaked and adsorbed, and finally baked in a muffle furnace at 500°C for 4 hours to obtain a Ce _0.8 La _0.2 O _1.9 coating.

Measure 5.6mL of H ₂ PdCl ₄ aqueous solution and add deionized water to dilute the honeycomb ceramic carrier just enough to immerse the honeycomb ceramic carrier, then dip the coated honeycomb ceramic carrier into the diluted solution, shake it in a constant temperature water bath, take it out, and blow out the holes. The remaining solution was then dried in air at 120°C for 1 hour, and then calcined in air at 1200°C for 4 hours to obtain a Pd(1g/L)/Ce _0.8 La _0.2 O _1.9 catalyst.

Example 9

Weigh 0.42g La ₂ O ₃ , 0.29g Y ₂ O ₃ and add HNO ₃ respectively, mix with 9.19g Ce(NO ₃ ) ₃ ·6H ₂ O and 5.37g citric acid, add appropriate amount of deionized water, stir evenly, get coating solution. Dip the cordierite honeycomb ceramics with a size of 50mm×25mm×40mm, a porosity of 195cell/in ² , and a mass of 31.76g into the coating solution, take it out, blow out the residual liquid in the honeycomb channels, and heat the cordierite honeycomb ceramics at room temperature to 50 ℃ until the surface is dry, then dried at 120℃ for 1 hour, and then fired in a muffle furnace at 500℃ for 1 hour. Repeat the above process for 2 to 3 times until the coating solution is completely soaked and adsorbed, and finally baked in a muffle furnace at 500°C for 4 hours to obtain a Ce _0.8 La _0.1 Y _0.1 O _1.9 coating.

Measure 5.6mL of H ₂ PdCl ₄ aqueous solution and add deionized water to dilute the honeycomb ceramic carrier just enough to immerse the honeycomb ceramic carrier, then dip the coated honeycomb ceramic carrier into the diluted solution, shake it in a constant temperature water bath, take it out, and blow out the holes. The remaining solution was then dried in air at 120°C for 1 hour, and then calcined in air at 500°C for 4 hours to obtain a Pd(1g/L)/Ce _0.8 La _0.1 Y _0.1 O _1.9 catalyst.

The organic waste gas catalytic combustion catalyst prepared in the above-mentioned Examples 1 to 9 of the present invention is made into a cylindrical shape, packed in a fixed bed catalytic combustion reactor, and the catalytic combustion of toluene is used as a probe reaction to perform organic waste gas purification catalytic combustion performance Evaluation, the honeycomb ceramic catalyst packing specification is 20mm in diameter and 40mm in length, and the toluene ^is carried by the air to flow through the reactor ^. The results are shown in Table 1.

The toluene catalytic combustion effect of each catalytic combustion catalyst of table 1

From the data in Table 1, it can be seen that the catalyst of the present invention has higher activity in the purification and treatment of organic waste gas, has a lower light-off temperature for the catalytic combustion and purification treatment of organic waste gas, and the catalyst also has good thermal stability, as in example 7, 8. After calcination at high temperature, its activity decreases slowly, and the lower limit temperature of toluene oxidation of the catalyst calcined at 1200 ℃ is only increased by 40 ℃. At the same time, the catalyst coating is firmly combined with the surface of the honeycomb ceramic carrier, and the coating does not fall off during the impregnation and use.

Claims (6)

1. a CeO ₂ based composite oxide coating loaded Pd catalyst, it comprises honeycomb carrier framework, coating and noble metal Pd, it is characterized in that described coating is made of CeO ₂ , the third subgroup metal oxide One or several compositions, wherein the mass percentage of the _CeO2- based composite oxide coating is 5% to 30% of the honeycomb ceramic carrier, and the content of _CeO2 and the third subgroup metal oxide in the mixed oxide coating The amount ratio (calculated as metal) is 9:1-1:9, and the loading amount of active metal component Pd is 0.1-2.0g Pd per liter of catalyst. 2. The organic waste gas catalytic combustion catalyst according to claim 1, characterized in that the third subgroup metal oxide is one or more of La ₂ O ₃ , Sm ₂ O ₃ and Y ₂ O ₃ . 3. The catalyst for catalytic combustion of organic waste gas according to claim 1 or 2, characterized in that said honeycomb ceramic carrier framework is a cordierite honeycomb ceramic framework. 4. a CeO _base composite oxide coating load Pd catalyst preparation method, it is characterized in that the catalyst preparation method comprises the following steps: (1) Preparation of coating solution, add HNO ₃ to a certain amount of the third subgroup metal oxide, mix with Ce(NO ₃ ) ₃ and organic acid or ethylene glycol or a mixture of the two, add an appropriate amount of water, stirred evenly, to prepare the coating liquid; (2) Coating of the skeleton coating of the honeycomb ceramic carrier, ① soak the honeycomb ceramic carrier in the coating liquid and take it out, remove the coating liquid remaining in the pores of the honeycomb ceramic carrier; ② place the honeycomb ceramic in ① for 0.5- Dry for 24 hours, then dry at 80-120°C for 0.5-12 hours; ③ bake the honeycomb ceramics in ② at 400-1000°C for 0.5-2 hours; ④ repeat steps ①-③ two to four times until coated The layer liquid is impregnated and adsorbed completely, and finally baked at 400-1000°C for 1-5 hours to make a coated honeycomb ceramic carrier; (3) Loading of active metal components, preparing a certain concentration of H ₂ PdCl ₄ solution as an impregnation solution for loading noble metal active components. Immerse the coated honeycomb ceramic carrier into the H ₂ PdCl ₄ solution, take it out, remove the aqueous solution remaining in the pores of the honeycomb ceramic carrier, dry it at 80-120°C for 0.5-12 hours, and finally put it in a high-temperature furnace at 400-1000°C Roasting for 1 to 5 hours, the finished catalyst is obtained. 5. CeO according to claim 4 The method for preparing a Pd catalyst supported by a composite oxide coating based on _CeO2 is characterized in that the organic acid is one or more of citric acid, malic acid and tartaric acid. 6. CeO according to claim ₄ The preparation method of the supported Pd catalyst of the base composite oxide coating is characterized in that the total substance amount of the organic acid used or ethylene glycol or the mixture of the two is CeO _base composite oxidation 0.2 to 4 times the total amount of metal ions in the substance.