THREE-WAY CATALYST HAVING LOW NH3 FORMATION AND PREPARATION METHOD THEREFOR

Abstract

A three-way catalyst having low NH.sub.3 formation is disclosed. The catalyst includes a carrier and a coating material. The coating material includes a precious metal active component and a catalytic material. The precious metal active component includes a first precious metal active component and a second precious metal active component. The first precious metal active component is a composition containing Ru. The second precious metal active component is a composition containing Pt, Pd and Rh. Alternatively, the second precious metal active component is a composition containing Pd and Rh.

Claims

1. A three-way catalyst, comprising a carrier and a coating material, the coating material comprising a precious metal active component and a catalytic material, wherein: the precious metal active component includes a first precious metal active component and a second precious metal active component; the first precious metal active component comprises Ru; and the second precious metal active component comprises Pd and Rh, and optionally, Pt.

2. The three-way catalyst according to claim 1, wherein the Ru is present in the first precious metal active component in an amount of 1 ~ 100 g/ft.sup.3.

3. The three-way catalyst according to claim 2, wherein the Ru is present in the first precious metal active component in an amount of 5 ~ 40 g/ft.sup.3.

4. The three-way catalyst according to claim 1, wherein the Ru in the first precious metal active component contains metallic ruthenium and/or ruthenium oxide.

5. The three-way catalyst according to claim 1, wherein the catalytic material comprises an oxygen storage material and an alumina material.

6. The three-way catalyst according to claim 5, wherein the oxygen storage material comprises CeO.sub.2, CeO.sub.2—ZrO.sub.2, CeO.sub.2—ZrO.sub.2—Y.sub.2O.sub.3, CeO.sub.2—ZrO.sub.2—La.sub.2O.sub.3—Y.sub.2O.sub.3, CeO.sub.2—ZrO.sub.2—La.sub.2O.sub.3—Pr.sub.2O.sub.3, or CeO.sub.2—ZrO.sub.2—La.sub.2O.sub.3—La.sub.2O.sub.3.

7. The three-way catalyst according to claim 5, wherein the alumina material comprises pure alumina or a modified alumina containing La and/or Ce.

8. The three-way catalyst according to claim 1, wherein the carrier comprises a ceramic carrier or a metal carrier.

9. A method for preparing the three-way catalyst according to claim 1, comprising: loading a first salt solution of the first precious metal active component and a second salt solution of the second precious metal active component onto a catalytic material; drying and calcining the catalytic material with the first and second salt solutions loaded thereon to obtain a coating material; mixing the coating material, water, and a binder to obtain a coating material slurry; coating the coating material slurry on the carrier; and drying and calcining the carrier with the coating material slurry thereon to obtain the three-way catalyst.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG. 1 is CO conversion efficiency curve of the catalysts prepared in the comparative example and embodiment of the present invention prepares to. In FIG. 1, C1-1 and C2-1 are the catalysts of Comparative Example 1 and Comparative Example 2, and C3-1, C4-1 and C5-1 are the catalysts of embodiment 1, embodiment 2 and embodiment 3.

[0036] FIG. 2 is the HC (CH.sub.4) conversion efficiency curve of the catalysts prepared in the comparative example and the embodiment of the present invention. In FIG. 2, C1-1 and C2-1 are the catalysts of comparative Example 1 and embodiment 2, and C3-1, C4-1 and C5-1 are the catalysts of embodiment 1, embodiment 2 and embodiment 3.

[0037] FIG. 3 is the NO.sub.x (NO) conversion efficiency curve of the catalysts prepared in the comparative example and the embodiment of the present invention. In FIG. 3, C1-1 and C2-1 are the catalysts of Comparative Example 1 and embodiment 2, and C3-1, C4-1 and C5-1 are the catalysts of embodiment 1, embodiment 2 and embodiment 3.

[0038] FIG. 4 shows the different LambdaNH.sub.3formation of the catalysts prepared by the comparative examples and embodiments of the present invention. In FIG. 4, C1-1 and C2-1 are catalysts of comparative example 1 and embodiment 2, and C3-1, C4-1 and C5-1 are catalysts of embodiment 1, embodiment 2 and embodiment 3.

DETAILED DESCRIPTION OF THE INVENTION

[0039] The following describes the present invention in detail with reference to the drawings.

[0040] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be further explained in detail below with reference to the drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not for limiting the present invention.

Comparative Example 1

[0041] S1, preparation of coating material;

[0042] The Pd(NO.sub.3).sub.2 and Rh(NO.sub.3).sub.2 solutions were loaded on Al.sub.2O.sub.3 and CeO.sub.2—ZrO.sub.2 materials by dipping method, dried at 80° C. for 6 h, and calcined at 500° C. for 2 h to obtain a coating material, denoted as M1.

[0043] S2, preparation of coating material slurry;

[0044] Mix M1 with water and a binder to obtain a coating material slurry, denoted as N1.

[0045] S3, prepares three-way catalyst;

[0046] The N1 is coated on the cordierite ceramic carrier, and the carrier size is Φ25.4*101.6/400 cpsi. After drying at 80° C. for 6 h and calcining at 500° C. for 2 h, the coating amount is 200 g/L, the total content of Pd and Rh is 35 g/ft.sup.3, and the ratio of Pd and Rh is 9:1. The prepared catalyst is denoted as C1-1.

[0047] The N1 is coated on the cordierite ceramic carrier, and the carrier size is Φ304.8*152.4/400 cpsi. After drying at 80° C. for 6 h and calcining at 500° C. for 2 h, the coating amount is 200 g/L, the total content of Pd and Rh is 35 g/ft.sup.3, and the ratio of Pd and Rh is 9:1. The prepared catalyst is denoted as C1-2.

Comparative Example 2

[0048] S1, preparation of coating material;

[0049] The Pt(NO.sub.3).sub.2, Pd(NO.sub.3).sub.2 and Rh(NO.sub.3).sub.2 solutions were loaded onto the La—Al.sub.2O.sub.3 and CeO.sub.2—ZrO.sub.2 materials by dipping, dried at 80° C. for 6 h, and calcined at 500° C. for 2 h to obtain a coating. Layer material, denoted as M2.

[0050] S2, preparation of coating material slurry;

[0051] The M2 is mixed with water and a binder to obtain a coating material slurry, which is denoted as N2.

[0052] S3, prepares three-way catalyst;

[0053] The N2 is coated on the cordierite ceramic carrier, and the carrier size is 25.4+101.6/400 cpsi. After drying at 80° C. for 6 h and calcining at 500° C. for 2 h, the coating amount is 200 g/L, the total content of Pt, Pd and Rh is 35 g/ft.sup.3, and the ratio of Pt, Pd and Rh is 3:6:1. The prepared catalyst was denoted as C2-1.

[0054] N2 is applied to the cordierite ceramic carrier, the carrier size is Φ304.8*152.4/400 cpsi. After drying at 80° C. for 6 h and calcining at 500° C. for 2 h, the coating amount is 200 g/L, the total content of Pt, Pd and Rh is 35 g/ft.sup.3, and the ratio of Pt, Pd and Rh is 3:6:1. The prepared catalyst is denoted as C2-2.

Embodiment 1

[0055] S1, preparation of coating material;

[0056] The Pd(NO.sub.3).sub.2, Rh(NO.sub.3).sub.2 and Ru(NO.sub.3).sub.2 solutions were loaded onto Al.sub.2O.sub.3 and CeO.sub.2—ZrO.sub.2 materials by impregnation method, dried at 80° C. for 6 h, and calcined at 500° C. for 2 h to obtain a coating material, denoted as M3.

[0057] S2, preparation of coating material slurry;

[0058] The M3 is mixed with water and a binder to obtain a coating material slurry, which is denoted as N3.

[0059] S3, prepares three-way catalyst;

[0060] The N3 is coated on the cordierite ceramic carrier, the carrier size is Φ25.4*101.6/400 cpsi. After drying at 80° C. for 6 h and calcining at 500° C. for 2 h, the coating amount is 200 g/L, the total content of Pd and Rh is 35 g/ft.sup.3, the ratio of Pd and Rh is 9:1, and the content of Ru is 5 g/ft.sup.3. The prepared catalyst was denoted as C3-1.

[0061] The N3 is coated on the cordierite ceramic carrier, and the carrier size is Φ304.8*152.4/400 cpsi. After drying at 80° C. for 6 h and calcining at 500° C. for 2 h, the coating amount is 200 g/L, the total content of Pd and Rh is 35 g/ft.sup.3, the ratio of Pd and Rh is 9:1, and the content of Ru is 5 g/ft.sup.3. The prepared catalyst is denoted as C3-2.

Embodiment 2

[0062] S1, the preparation of coating material;

[0063] Pt(NO.sub.3).sub.2, Pd(NO.sub.3).sub.2, Rh(NO.sub.3)2 and Ru(NO.sub.3).sub.2 solutions were loaded onto La—Al.sub.2O.sub.3 and CeO.sub.2—ZrO.sub.2 materials by impregnation method, dried at 80° C. for 6 h, 500° C. calcined for 2 h to obtain a coating material, denoted as M4.

[0064] S2, preparation of coating material slurry;

[0065] The M4 is mixed with water and a binder to obtain a coating material slurry, which is denoted as N4.

[0066] S3, prepares three-way catalyst;

[0067] The N4 is coated on a cordierite ceramic carrier with a carrier size of 25.4*101.6/400 cpsi. After drying at 80° C. for 6 h and calcining at 500° C. for 2 h, the coating amount is 200 g/L, the total content of Pt, Pd and Rh is 35 g/ft.sup.3, the ratio of Pt, Pd and Rh is 3:6:1, and the Ru content is 20 g/ft.sup.3. The prepared catalyst is denoted as C4-1.

[0068] The N4 is coated on the cordierite ceramic carrier, the carrier size is Φ304.8*152.4/400 cpsi. After drying at 80° C. for 6 h and calcining at 500° C. for 2 h, the coating amount is 200 g/L, the total content of Pt, Pd and Rh is 35 g/ft.sup.3, the ratio of Pt, Pd and Rh is 3:6:1, and the Ru content is 20 g/ft.sup.3. The prepared catalyst is denoted as C4-2.

Embodiment 3

[0069] S1, the preparation of coating material;

[0070] Pt(NO.sub.3)2, Pd(NO.sub.3)2, Rh(NO.sub.3)2 and Ru(NO.sub.3).sub.2 solutions were loaded onto La—Al.sub.2O.sub.3 and CeO.sub.2—ZrO.sub.2 materials by impregnation method, dried at 80° C. for 6 h, and calcined at 500° C. for 2 h to obtain a coating material, which is denoted as M5.

[0071] S2, preparation of coating material slurry;

[0072] The M5 is mixed with water and a binding agent to obtain a coating material slurry, denoted as N5.

[0073] S3, prepares three-way catalyst;

[0074] The N5 is coated on a cordierite ceramic carrier with a carrier size of Φ25.4*101.6/400 cpsi. After drying at 80° C. for 6h and calcining at 500° C. for 2h, the coating amount is 200 g/L, the total content of Pt, Pd and Rh is 35 g/ft.sup.3, the ratio of Pt, Pd and Rh is 3:6:1, and the Ru content is 40 g/ft.sup.3. The prepared catalyst was denoted as C5-1.

[0075] The N5 is coated on the cordierite ceramic carrier, the carrier size is Φ304.8*152.4/400 cpsi. After drying at 80° C. for 6h and calcining at 500° C. for 2 h, the coating amount is 200 g/L, the total content of Pt, Pd and Rh is 35 g/ft.sup.3, the ratio of Pt, Pd and Rh is 3:6:1, and the Ru content is 40 g/ft.sup.3. The prepared catalyst is denoted as C5-2. Test example 1

[0076] Catalyst C1-1, C2-1, C3-1, C4-1 and C5-1 obtained in above-mentioned comparative example and embodiment are carried out activity evaluation test on vehicles exhaust sample simulation device, test condition is as follows:

[0077] Simulated atmosphere: HC (CH.sub.4): 1000 ppm; CO: 4000 ppm; NO: 1000 ppm; O.sub.2: 3500 ppm; H.sub.2O: 10%; CO.sub.2: 10%; N.sub.2 is the balance gas, and the airspeed is 40,000 h-1 (the airspeed calculated according to the volume of TWC). The patent of the present invention adopts CH.sub.4 with the most stable structure to represent HC in vehicles exhaust gas; NO.sub.x is adopted to represent NO.sub.x (including NO.sub.x such as NO and NO.sub.2) in vehicles exhaust gas. The catalysts were tested for the conversion efficiency of CO, CH.sub.4 and NO at 300-600° C. (the main temperature range of vehicles exhaust) under the simulated atmosphere.

[0078] FIG. 1, FIG. 2 and FIG. 3 are the corresponding catalysts C1-1, C2-1, C3-1, C4-1 of comparative example 1, comparative example 2, embodiment 1, embodiment 2 and embodiment 3 respectively and the conversion efficiency curves of C5-1 to three pollutants of CO, CH.sub.4 and NO.

[0079] FIG. 1 result shows, comparative example and embodiment all have very high conversion efficiency to CO, and performance difference is little.

[0080] The results of FIG. 2 show that, for the light-off temperature performance of CH.sub.4, the activity of embodiment 1 is slightly lower than that of comparative example 1; the activities of embodiment 2 and comparative example 2 are basically equivalent; the above results show that the TWC prepared according to the patented preparation process and catalytic material of the present invention, the addition of metal Ru has inconsistent effects on the activity of PtPdRh and PdRh type, the activity of PdRh type TWC is slightly inhibited, and the activity of PtPdRh type TWC has almost no effect, even with the increase of Ru addition, the activity of PtPdRh-type TWC was slightly improved.

[0081] The results of FIG. 3 show that the influence characteristics of each embodiment and the comparative example on the light-off temperature performance of NO are consistent with the law of CH.sub.4.

Test Example 2

[0082] The catalysts C1-1, C2-1, C3-1, C4-1 and C5-1 obtained in the comparative examples and embodiments are verified different lambda NH.sub.3 on the vehicles exhaust sample simulation device (N.sub.2 Selectivity), The test conditions are as follows:

[0083] Simulated atmosphere: HC (CH.sub.4): 1000 ppm; CO: 4000 ppm; NO: 1000 ppm; H.sub.2O: 10%; CO.sub.2: 10%; N.sub.2 is the balance gas, and the airspeed is 40,000 h-1 (the airspeed calculated according to the volume of TWC). O.sub.2 content is determined according to the Lambda value. The patent of the present invention adopts CH.sub.4 with the most stable structure to represent HC in vehicles exhaust gas; NO.sub.x is adopted to represent NO.sub.x (including NO.sub.x such as NO and NO.sub.2) in vehicles exhaust gas. The catalyst was tested at 500° C. in a simulated atmosphere (this temperature is the temperature at which the TWC NH.sub.3formation is relatively high, and the average exhaust temperature of the vehicles exhaust is also near this, so it is more representative to choose this temperature test),The NH.sub.3formation of each comparative example and embodiment at different Lambdas. Lambda is the equivalent air-fuel ratio.

[0084] FIG. 4 is the NH.sub.3 formation of corresponding catalyst C1-1, C2-1, C3-1, C4-1 and C5-1 of comparative example 1, comparative example 2, embodiment 1, embodiment 2 and embodiment 3 at lambda value when 0.93-1.05. The five curves in FIG. 4 correspond to C1-1, C2-1, C3-1, C4-1 and C5-1 in order from top to bottom.

[0085] The results of FIG. 4 show that the NH.sub.3formation of the embodiment is greatly reduced compared with the comparative example, indicating that the addition of metal Ru has a significant effect on the reduction of the catalyst NH.sub.3formation. Compared with embodiment 1 and embodiment 2, when lambda is less than 1, the formation ofNH.sub.3 in embodiment 3, decreases to a certain extent, which shows that the addition amount of Ru also affects the formation of NH.sub.3. With the increase of the addition amount, the formation of NH.sub.3 will decrease slightly.

Test Example 3

[0086] The catalyzer C1-2, C2-2, C3-2, C4-2 and C5-2 that above-mentioned comparative example and embodiment are obtained are in the gas engine bench of heavy-duty equivalence ratio combustion, according to the test method specified inGB17691-2016″Diesel Vehicle Pollutant Emission Limits and Measurement Methods (China Phase VI)″ validates the WHTC test cycle conditions, comparative examples and implementation of CO, HC (CH.sub.4), NO.sub.x and NH.sub.3 emission values.

[0087] Table 1 shows results of the corresponding catalysts C1-2, C2-2, C3-2, C4-2 and C5-2 of comparative example 1, comparative example 2, embodiment 1, embodiment 2 and embodiment 3 according to WHTC cycle and the CO, HC(CH.sub.4), NO.sub.x and NH.sub.3 emission values of the operating conditions test.

TABLE-US-00001 The emission values of pollutants in engine bench WHTC test of comparative example and embodiments. CO HC (CH.sub.4) NO.sub.x NH.sub.3 mg/kWh mg/kWh mg/kWh ppm 4000 500 460 10 C1-2 199 19 192 36.4 C2-2 259 25 208 32.7 C3-2 200 51 224 2.48 C4-2 341 40 202 1.71 C5-2 342 36 209 0.36

Pollutants

National VI Limit

[0088] The results in Table 1 show that the three pollutants of embodiment and Comparative Example, CO, HC(CH.sub.4) and NO.sub.x, are all purified to within 50% of the national six limit, showing very high pollutant purification efficiency. The NH.sub.3formation of comparative example 1 and comparative example 2 is more than three times of the national six limit, and the emission exceeds the standard; the NH.sub.3formationof embodiment 1, embodiment 2 and embodiment 3 are all lower than 10 ppm, the NH.sub.3formationis very low, showing high N.sub.2 selectivity. The above results show that, while embodiment 1, embodiment 2 and embodiment 3 efficiently purify CO, CH.sub.4 and NO.sub.x, NH.sub.3 emission is greatly reduced and N.sub.2 selectivity is greatly improved.

[0089] The above discusses preferred embodiments of the present invention, and is not intended to limit the present invention. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of protection of the present invention.