WO2009094891A1

WO2009094891A1 - A cu-ce-al catalyst for removing soot particles and nox simultaneously and its preparation method

Info

Publication number: WO2009094891A1
Application number: PCT/CN2008/073916
Authority: WO
Inventors: Xiaodong Wu; Duan WENG; Fan LIN; Jia Li
Original assignee: Tsinghua University
Priority date: 2008-01-29
Filing date: 2008-12-31
Publication date: 2009-08-06
Also published as: CN101239313B; CN101239313A

Abstract

A Cu-Ce-Al catalyst for removing soot particles and NOx simultaneously with a structure formula of CuO-CeO2-Al2O3, wherein the mole ratio of Cu : Ce is 1:19~1:4, the mass ratio of (CuO-CeO2): Al2O3 is 9:1 ~ 1:2. The catalyst can be prepared by sol-gel method or coprecipitation method which use cheap nonnoble metal salts as raw materials. The preparation method can be controlled easily and achieve industrialization readily. The catalyst can low the combustion temperature of soot particles from 500 °C to 400 °C, and reduce NO to a certain extent, thus can remove both pollutants simultaneously. The catalyst has superior heat stability.

Description

Copper beryllium aluminum catalyst for removing soot particles and nitrogen oxides at the same time and preparation method thereof

The invention belongs to the technical field of preparation of diesel exhaust gas catalysts, in particular to a copper-rhenium-aluminum catalyst for removing carbon smoke particles and nitrogen oxides simultaneously by selective oxidation removal of diesel vehicle exhaust gas by using ruthenium oxide as carrier. Preparation.

Background technique

Compared with gasoline engines, diesel engines have high thermal efficiency, economy and low CO ₂ emissions, so they have a bright future. With the increasingly strict environmental regulations, diesel exhaust pollutants, especially soot and nitrogen oxides (NOx), have been seriously polluted by the environment. Since the diesel engine is oxy-combusted, the most effective three-way catalyst (TWC) for gasoline engine exhaust purification is not suitable for diesel engines. The development of diesel vehicle exhaust catalytic purification materials and technologies such as gasoline TWC is in front of researchers. A challenging and urgent task.

In recent years, foreign research and development to eliminate soot and N0 _X catalytic purification technology books has become a research hotspot. The use of soot and N0 _X emitted by the diesel engine to generate redox reaction under oxygen-rich conditions, resulting in harmless and (3⁄4, is a very important and promising diesel exhaust gas treatment technology, has a good application prospect. Develop a single catalyst that simultaneously purifies soot and NOx, in addition to a single unit of lean NOx catalyst (LNC) and diesel particulate filter (DPF) or a combination of LNC and diesel oxidation catalyst (D0C). It has become a research and development hotspot in recent years, especially perovskites, spinel composite oxides and bimetallic catalysts containing alkali metals and transition metals. Catalysts can be used to ensure the coating properties and thermal stability of the catalyst on DPF. Dispersed in high specific surface materials such as Y-A1 ₂ 0 ₃ [Zhongpeng Wang et al, Catal. Commun. 8 (2007) 1659-1664; N. Nejar et al, Appl. Catal. B 70 (2007) 261-268] or zeolite Molecular sieves [Ν· Nejar et al., Catal. Today 119 (2007) 262-266].

Summary of the invention

SUMMARY OF THE INVENTION An object of the present invention is to provide a copper beryllium aluminum catalyst which is inexpensive and has a good application effect while removing soot particles and nitrogen oxides, and a preparation method thereof.

In order to achieve the above object, the technical solution adopted by the present invention is: a copper beryllium aluminum catalyst which simultaneously removes soot particles and nitrogen oxides, and the copper beryllium aluminum catalyst has the general formula CuO-Ce0 ₂ -Al ₂ 0 ₃ , Wherein the Cu: Ce molar ratio is 1: 19~1: 4, (Cu0+Ce0 ₂ ): A1 ₂ 0 ₃ mass ratio is 9:1~1: 2.

Another technical solution provided by the present invention is: a preparation method of a copper bismuth aluminum catalyst for simultaneously removing soot particles and nitrogen oxides, wherein the copper bismuth aluminum catalyst is prepared by a sol-gel method or a coprecipitation method, and is prepared. Proceed as follows:

(1) Take appropriate amount of soluble salts of Cu and Ce, and mix them in a molar ratio of Cu: Ce=l: 19~l: 4 to prepare ion concentration. a mixed aqueous solution of 1 to 1. 5 mol/L;

(2) Sol-gel method: Add the appropriate amount of complexing agent citric acid and pore-forming agent polyethylene glycol to the mixed solution obtained in step 1. The amount of polyethylene glycol added is 5~15wt% of the amount of citric acid, stirring Obtaining a solution; wherein the gram equivalent of citric acid is 1.1 to 1.3 times the sum of the gram equivalents of all metal ions;

Coprecipitation method: adding the precipitant ammonia water and the oxidant 0 _{2 to} the mixed solution obtained in the step 1, adding hydrogen peroxide when the Ce ³⁺ salt is used in the mixed solution, and adding hydrogen peroxide when using the Ce ⁴⁺ salt, wherein the ammonia water is added in an amount of Maintaining the pH value of the final solution > 10, the amount of addition of 0 ₂ is equivalent to 1.2 times the molar content of the ruthenium ion, and the precipitate is stirred to obtain a suspension;

(3) Add active Y-A1 ₂ 0 ₃ powder to the solution or suspension obtained in step 2, according to the final product (CuO+Ce0 ₂ ) :Al ₂ 0 ₃ mass ratio of 9:1~1:2 ratio , stirring vigorously, so that Y-A1 ₂ 0 _{3 is} evenly dispersed in the solution to form a suspension;

(4) When the sol-gel method is used, the suspension obtained in the step 3 is continuously heated and stirred at 100 to 12 (TC is evaporated to form a gel; or the suspension obtained in the step 3 is obtained by the coprecipitation method. Stirring was stopped, allowed to stand for 24 h, the supernatant liquid was poured off, and suction filtration was performed to obtain a lumpy precipitate, which was washed with water 2 to 3 times, and then the obtained gel or precipitate was baked at 120 ° C;

(5) The gel solid or precipitate obtained in the step 4 was crushed, ground, and calcined at 500 ° C for 3 hours to obtain a catalyst powder.

In the mixed aqueous solution of Cu and Ce in the step (1), the soluble salt of A1 is also added at the same time, and the ratio of the final product (CuO+Ce0 ₂ ) :Al ₂ 0 ₃ is 9:1 to 1:2. It is mixed with a soluble salt of Cu and Ce, and the catalyst powder is obtained in the same manner as in the other steps except that the step (3) is omitted.

The copper salt is Cu(N0 ₃ ) ₂ *6H ₂ 0, and CuS0 ₄ *5H ₂ 0 or CuCl ₂ *2H ₂ 0 may also be used in the coprecipitation method.

The sulfonium salt is Ce(N0 ₃ ) ₃ *6H ₂ 0 or Ce (Ν ) ₂ (Ν0 ₃ ) ₆ ·2Η ₂ 0, and Ce (S0 ₄ ) ₂ *4H ₂ 0 may be used in the coprecipitation method.

CeCl ₃ *7H ₂ 0.

The alumina is a high specific surface Y-A1 ₂ 0 ₃ (120~200m7g), the aluminum salt is Al (Ν0 ₃ ) ₃ ·9Η ₂ 0, and the Al ₂ (S0 ₄ ) ₃ can also be used in the coprecipitation method. · 183⁄40 or A1C1 ₃ .

The invention has the beneficial effects that: the cheap non-precious metal salt is used as the raw material, and the catalyst production cost is low; the simple catalyst preparation process such as the sol-gel method and the coprecipitation method is adopted, the reaction process is easy to control, and the industrial production is easy to be realized; The obtained CuO-Ce0 ₂ -Al ₂ 0 ₃ catalyst can greatly reduce the temperature of burning the soot collected on the particulate trap to C0 ₂ and at the same time have the ability to reduce nitrogen oxides, thereby simultaneously eliminating soot particles and The effect of nitrogen oxides. The catalyst still has a large specific surface area after being treated at 800 ° C for 10 hours in an air atmosphere. The alumina acts to prevent the growth of cerium oxide and copper oxide grains, and can catalytically burn soot particles at 455 ° C. And the reduction rate of NO is 34%, indicating that the catalyst has high high temperature resistance.

DRAWINGS

1 is a soot temperature-increasing reaction curve of CuCe-a and CuCeA12-a catalysts in Test Example 1. detailed description

The invention will be better illustrated by the following examples.

Example 1

A 5 g copper beryllium aluminum catalyst (CuCeA19) was prepared by a sol-gel method. About 30 ml of deionized water was added to a 200 ml beaker, and 10.78 g of cerium nitrate, 0.68 g of copper nitrate, and 3.68 g of aluminum nitrate were added and dissolved by stirring. 28 g of citric acid and 0.8 g of polyethylene glycol were added to the solution and mixed well. The solution was continuously heated and stirred at 110 ° C until evaporated to form a gel; then dried in an oven at 120 ° C. The obtained gel solid was chopped, ground, and calcined at 500 ° C for 3 hours to obtain a CuCeA19 catalyst powder sample. The molar ratio of Cu to Ce in the catalyst was 1:9, and the mass ratio of (Cu0+Ce0 ₂ ) to A1 ₂ 0 ₃ was 9:1.

Example 2

5 g of copper beryllium aluminum catalyst (CuCeA12) was prepared by a sol-gel method. About 30 ml of deionized water was added to a 200 ml beaker, and 7.99 g of cerium nitrate and 0.51 g of copper nitrate were added and dissolved by stirring. 14 g of citric acid and 0.4 g of polyethylene glycol were added to the solution and mixed well. 1.67 g of active γ-Α1 ₂ ₃ powder was added and stirred vigorously to uniformly disperse Υ-Α1 ₂ ₃ in the solution to form a suspension. The suspension was continuously heated and stirred at 110 ° C until evaporated to form a gel; then dried in an oven at 120 ° C. The obtained gel solid was chopped, ground, and calcined at 500 ° C for 3 hours to obtain a CuCeA12 catalyst powder sample. The molar ratio of Cu to Ce in the catalyst was 1:9, and the mass ratio of (Cu0+Ce0 ₂ ) to A1 ₂ 0 ₃ was 2:1.

Example 3

5 g of copper beryllium aluminum catalyst (CuCeAll) was prepared by coprecipitation. About 30 ml of deionized water was added to a 200 ml beaker, and 5.57 g of barium sulfate and 0.61 g of copper sulfate were taken and dissolved by stirring. Add 100 ml of concentrated ammonia water (25 to 28%) to the solution, stir vigorously, and precipitate. 2.5 g of active Y-A1 ₂ _{3 3} powder was added and stirred vigorously to uniformly disperse Y-A1 ₂ 0 ₃ and the precipitate in the solution to form a suspension. Stirring was stopped, and the mixture was allowed to stand for 24 hours, and the supernatant liquid was poured off, and suction-filtered to obtain a lumpy precipitate, which was washed 3 times with water and dried at 120 °C. The obtained precipitate was crushed, ground, and calcined at 500 ° C for 3 hours to obtain a CuCeAll catalyst powder. The molar ratio of Cu to Ce in the catalyst was 1:9, and the mass ratio of (Cu0+Ce0 ₂ ) to A1 ₂ 0 ₃ was 1:1.

Example 4

5 g of copper beryllium aluminum catalyst was prepared by coprecipitation method. About 30 ml of deionized water was added to a 200 ml beaker, and 1.99 g of thallium chloride, 0.23 g of copper chloride, and 10.46 g of aluminum chloride were taken and dissolved by stirring. Add 200 ml of concentrated ammonia water (25 to 28%) to the solution, stir vigorously, and precipitate completely. After standing for 24 h, the supernatant was poured off and suction filtered to obtain a lumpy precipitate, which was washed 3 times with water and dried at 120 °C. The obtained precipitate was crushed, ground, and calcined at 500 ° C for 3 hours to obtain a CuO-Ce0 ₂ -Al ₂ O ₃ catalyst powder. The molar ratio of Cu to Ce in the catalyst was 1:4, and the mass ratio of (Cu0+Ce0 ₂ ) to A1 ₂ 0 ₃ was 1:2.

Example 5

5 g of copper beryllium aluminum catalyst (CuCeA12) was prepared by a sol-gel method. About 30 ml of deionized water was added to a 200 ml beaker, and 13.34 g of cerium nitrate nitrate and 0.36 g of copper nitrate were added and dissolved by stirring. Add 20g citric acid and 0.6g poly to the solution Glycol, mix well. Adding 1.0 g of active γ-Α1 ₂ _{3 3} powder, stirring vigorously, uniformly dispersing Y-A1 ₂ 0 ₃ in the solution to form a suspension. The suspension was continuously heated and stirred at 110 ° C until evaporated to form a gel; then dried in an oven at 120 ° C. The obtained gel solid was chopped, ground, and calcined at 500 ° C for 3 hours to obtain a powder sample of CuO-Ce0 ₂ -Al ₂ O ₃ catalyst. The molar ratio of Cu to Ce in the catalyst was 1:19, and the mass ratio of (Cu0+Ce0 ₂ ) to A1 ₂ 0 ₃ was 4:1.

Comparative example 1

A 5 g copper ruthenium catalyst (CuCe) was prepared by a sol-gel method. About 30 ml of deionized water was added to a 200 ml beaker, and 11.98 g of cerium nitrate and 0.776 g of copper nitrate were added and stirred to dissolve. 21 g of citric acid and 0.6 g of polyethylene glycol were added to the solution, and the mixture was uniformly mixed. The solution was continuously heated and stirred at 110 ° C until it was evaporated to form a gel; then dried at 120 ° C in an oven. The obtained gel solid was chopped, ground, and calcined at 500 ° C for 3 hours to obtain a CuCe catalyst powder sample. The molar ratio of Cu to Ce in the catalyst was 1:9.

Test example 1

Taking CuCeA19, CuCeA12, CuCeAl1 and CuCeAl of Comparative Example 1 in Examples 1, 2, and 3 as an example, the catalytic activity of soot catalytic combustion under the catalyst-smoke loose contact mode was tested in the atmosphere of simulated diesel exhaust. . Specific test procedure: Take 100 mg of catalyst, mix with 10 mg of soot (Printex-U, Degussa), gently scrape it in a mortar with a spatula for 5 min, and install the mixture in a quartz tube reactor for temperature-programmed reaction (TPR). experiment. The test atmosphere is 10% 0 ₂ /N ₂ or 1000 ppm NO/10% O ₂ /N ₂ , and the space velocity is 40000 h—

The results are shown in Table 1. In the absence of nitric oxide, the catalytic activity of the catalyst for soot combustion decreases with increasing A1 ₂ 0 ₃ content; in the atmosphere of nitric oxide, only when A1 ₂ 0 ₃ is present. When it is increased to 50^.%, it has a more obvious effect. When the mass ratio of (Cu0+Ce0 ₂ ) to A1 ₂ 0 ₃ is 2:1, the catalyst exhibits a high simultaneous reduction of nitrogen oxide activity, and the maximum conversion of N0 is close to 40%.

Referring to Figure 1, a temperature-programmed (TP0) activity test curve for CuCe and CuCeA12 catalyst aged samples, wherein the test atmosphere: 10% 0 ₂ + lOOOOppm N0 + N ₂ equilibrium; gas flow rate: 500 mL / min; heating rate: 20 ° C / Min.

Test example 2

CuCeA19, CuCeA12, CuCeAl1 in Example 1, 2, and 3 and CuCeAl1 in Comparative Example 1 were respectively placed in a crucible, and treated in an electric resistance furnace at 800 ° C for 10 hours, and after cooling, a catalyst sample after heat treatment was obtained. Marked with the suffix "_a". Taking CuCeA19_a, CuCeA12_a, CuCeAl l_a and CuCe_a catalysts as an example, the catalytic activity of soot catalytic combustion under the catalyst-smoke loose contact mode was tested in the atmosphere of simulated diesel exhaust. Specific test procedure: Take 100 mg of catalyst, mix with 10 mg of soot (Printex-U, Degussa), gently scrape it in a mortar with a spatula for 5 min, and install the mixture in a quartz tube reactor for temperature-programmed reaction (TPR). experiment. The test atmosphere is 10%0 ₂ /N ₂ or 1000ppmNO/10%0 ₂ /N ₂ , and the space velocity is 40000h—

The results are shown in Table 2. In the absence of nitric oxide, the CuCe-a catalyst containing no A1 ₂ 0 _{3 has} a faster surface than the surface. When the grain grows, the catalytic activity for soot combustion decreases significantly. In the atmosphere of nitric oxide, when the mass ratio of (010+(3⁄40 ₂ ) to ₂ 0 ₃ is 2:1, the catalyst shows a better The high simultaneous reduction of nitrogen oxide activity, the maximum conversion of NO is 34%.

Table 1 Effect of fresh catalyst on simultaneous removal of soot and nitrogen oxides

Soot Tj. C Soot Tj. C NO XJ%

Sample specific surface (m ² /g)

(0 ₂ atmosphere) (N0+0 ₂ atmosphere) (N0+0 ₂ atmosphere)

CuCe 480 400 27 65

CuCeA19 515 405 30 87

CuCeA12 545 410 39 111

CuCeAl l 565 440 25 128 Table 2 Effect of aging catalyst on simultaneous removal of soot and nitrogen oxides

Soot Tj. C Soot Tj. C NO XJ%

Sample specific surface (m ² /g)

(0 ₂ atmosphere) (N0+0 ₂ atmosphere) (N0+0 ₂ atmosphere)

CuCe-a 530 475 27 13

CuCeA19-a 545 485 26 25

CuCeA12-a 550 455 34 73

CuCeAl l - a 555 480 23 87

Claims

Claim

A copper beryllium aluminum catalyst for simultaneously removing soot particles and nitrogen oxides, characterized in that the copper beryllium aluminum catalyst has a general formula of CuO-Ce0 ₂ -Al ₂ 0 ₃ , wherein a molar ratio of Cu:Ce The ratio is 1:19~1:4, (Cu0+Ce0 ₂ ): A1 ₂ 0 ₃ mass ratio is 9:1~ 1:2.

2. A method for preparing a copper ruthenium aluminum catalyst for simultaneously removing soot particles and nitrogen oxides, characterized in that the copper ruthenium aluminum catalyst is prepared by a sol-gel method or a coprecipitation method, and the preparation steps are as follows:

(1) taking a soluble salt of Cu and Ce, mixing molarly with Cu:Ce=l:19~l:4, and preparing a mixed aqueous solution having an ion concentration of 1 to 1.5 mol/L;

(2) Sol-gel method: adding the complexing agent citric acid and the pore-forming agent polyethylene glycol to the mixed solution obtained in the step 1, the polyethylene glycol is added in an amount of 5 to 15% by weight of the citric acid, and stirred to obtain a solution; wherein the gram equivalent of citric acid is 1.1 to 1.3 times the sum of the gram equivalents of all metal ions;

(4) When the sol-gel method is used, the suspension obtained in the step 3 is continuously heated and stirred at 100 to 12 (TC is evaporated to form a gel; or the suspension obtained in the step 3 is obtained by the coprecipitation method. Stirring was stopped, allowed to stand for 24 h, the supernatant was poured off, and suction filtered to obtain a lumpy precipitate, which was washed with water 2 to 3 times, and then the obtained gel or precipitate was dried at 120 ° C to become a gel solid or a precipitate;

The method for preparing a copper-cerium-aluminum catalyst for simultaneously removing soot particles and nitrogen oxides according to claim 2, wherein in the mixed aqueous solution of Cu and Ce in the step (1), A1 is simultaneously added. The soluble salt is mixed with the soluble salt of Cu and Ce according to the ratio of the final product (CuO+Ce0 ₂ ) : Al ₂ 0 _{3 by} mass ratio of 9:1 to 1:2, and the step (3) is omitted, and the other steps are the same. A catalyst powder was obtained.

The method for preparing a copper-cerium-aluminum catalyst for simultaneously removing soot particles and nitrogen oxides according to claim 2 or 3, wherein the copper salt is Cu(N0 ₃ ) ₂ *6H ₂ 0 In the precipitation method, CuS0 ₄ *5H ₂ 0 or CuCl ₂ *2H ₂ 0 is used.

The method for preparing a copper-cerium-aluminum catalyst for simultaneously removing soot particles and nitrogen oxides according to claim 2 or 3, wherein the onium salt is Ce (Ν0 ₃ ) ₃ ·6Η ₂ 0 or Ce (ΝΗ ₄ ) ₂ (Ν0 ₃ ) ₆ ·2Η ₂ 0, Ce (S0 ₄ ) ₂ *4H ₂ 0 in the coprecipitation method Or CeCl ₃ *7H ₂ 0.

The method for preparing a copper-cerium-aluminum catalyst for simultaneously removing soot particles and nitrogen oxides according to claim 2 or 3, wherein the alumina is a high specific surface Y - A1 ₂ 0 ₃ (120~ 200 mV'g), the aluminum salt is A1 (Ν0 ₃ ) ₃ ·9Η ₂ 0, and the coprecipitation method uses Al ₂ (S0 ₄ ) ₃ · 183⁄40 or A1C1 ₃ .