Ozone purification catalyst and preparation method and application thereof

Abstract

An ozone purification catalyst, and a preparation method therefor and an application thereof are provided. The catalyst coating uses macroporous, high specific surface and CeO.sub.2 and/or La.sub.2O.sub.3 modified Al.sub.2O.sub.3 as the carrier material, and Mn and/or Pd as the active component. The preparation method is to prepare the Al.sub.2O.sub.3-based material by a sol-gel method, and then to load the active components on the carrier material, and to dry, calcinate and solidify to obtain the ozone purification catalyst. The catalysts as prepared shows a fast and efficient purification of ozone. The complete conversion temperature covers a wide range of temperature. The catalyst has excellent texture performance, high specific surface area and large pore volume, which is beneficial to ozone purification when the car is running at high speed. The particle sizes and colors of the catalyst can be modified according to various requirements. According to the actual application, it can be coated on the radiator fins of automobile water tanks, and any place where coating is allowed in public areas such as urban bus stations, stop signs, kiosks, roadside guardrails, or exterior walls of buildings that is in contact with outdoor air.

Claims

1. A method of preparing an ozone purification catalyst, comprising the following steps: preparing a CeO.sub.2 and La.sub.2O.sub.3 modified Al.sub.2O.sub.3 carrier by a sol-gel method: mixing a soluble Ce salt solution and a soluble La salt solution with pseudo-boehmite, adjusting the pH with an acid to 3.5 to 4.5, wherein the CeO.sub.2 has a content of 15 to 20 wt % in the carrier, the La.sub.2O.sub.3 has a content of 2 to 3 wt % in the carrier, and the Al.sub.2O.sub.3 has a content of 77 to 83 wt % in the carrier; then calcining at 500 to 600 C. in air for 2 to 5 hours, and then at 800 C. in air for 2 to 5 hours to obtain the modified Al.sub.2O.sub.3 carrier; loading a soluble Pd salt solution and/or a soluble Mn salt solution on the modified Al.sub.2O.sub.3 carrier by an equal-volume impregnation method: wherein the Pd salt solution provides a Pd content, based on the element, of 0.3 to 0.5 wt % of the total weight of the ozone purification catalyst; the Mn salt solution provides a Mn content, based on the element, of 0 to 8 wt % of the total weight of the ozone purification catalyst; then, drying at 60 to 120 C. for 2 to 6 hours, and then calcining at 400 to 550 C. in air for 2 to 7 hours to obtain the ozone purification catalyst.

2. The method according to claim 1, wherein the soluble Ce salt solution includes Ce(NO.sub.3).sub.3 solution, and the soluble La salt solution includes La(NO.sub.3).sub.3 solution.

3. The method according to claim 1, wherein the acid for adjusting the pH includes nitric acid.

4. The method according to claim 1, wherein the soluble Pd salt solution includes Pd(NO.sub.3).sub.2, and the soluble Mn salt solution includes Mn(CH.sub.3COO).sub.2.

5. The method according to claim 1, wherein the Mn content is 8 wt % of the total weight of the ozone purification catalyst.

6. The method according to claim 5, wherein the soluble Mn salt solution includes Mn (CH.sub.3COO).sub.2.

7. The method according to claim 1, wherein the Pd content is 0.5 wt % of the total weight of the ozone purification catalyst, and the Mn content is 0 wt % of the total weight of the ozone purification catalyst.

8. The method according to claim 7, wherein the soluble Pd salt solution includes Pd (NO.sub.3).sub.2.

9. The method according to claim 1, wherein calcining at 500 to 600 C. in air for 2 to 5 hours comprises calcining at 500 C. in air for 5 hours.

10. The method according to claim 9, wherein calcining at 800 C. in air atmosphere for 2 to 5 hours comprises calcining at 800 C. in air for 3 hours.

11. The method according to claim 1, wherein drying at 60 to 120 C. for 2 to 6 hours comprises drying at 60 to 120 C. for 5 hours.

12. The method according to claim 11, wherein calcining at 400 to 550 C. in air for 2 to 7 hours comprises calcining at 500 C. in air for 5 hours.

13. The method according to claim 1, wherein calcining at 400 to 550 C. in air for 2 to 7 hours comprises calcining at 500 C. in air for 5 hours.

14. The method according to claim 1, wherein the modified Al.sub.2O.sub.3 carrier has a particle size of 3 to 15 m.

15. The method according to claim 14, wherein the modified Al.sub.2O.sub.3 carrier has a specific surface area of 132-152 m.sup.2/g.

16. The method according to claim 15, wherein the modified Al.sub.2O.sub.3 carrier has a pore volume of 0.35-0.36 ml/g.

17. The method according to claim 14, wherein the modified Al.sub.2O.sub.3 carrier has a pore volume of 0.35-0.36 ml/g.

18. The method according to claim 1, wherein the modified Al.sub.2O.sup.3 carrier has a specific surface area of 132-152 m.sup.2/g.

19. The method according to claim 1, wherein the modified Al.sub.2O3 carrier has a pore volume of 0.35-0.36 ml/g.

Description

DETAILED DESCRIPTION OF THE DISCLOSURE

(1) The present invention will be further described below in conjunction with specific embodiments. The specific embodiments are further explanations of the principles of the present invention and do not limit the present invention in any way. The same or similar technologies as the present invention do not exceed the protection scope of the present invention.

Example 1

(2) (1) A dilute HNO.sub.3 solution was added to pseudo-boehmite, and the pH was adjusted to 3.5 to 4.5, to prepare Al.sub.2O.sub.3 by the sol-gel method. The Al.sub.2O.sub.3 prepared by the sol-gel method was calcined at 550 C. in air atmosphere for 3 hours, and then continued to be calcined at 800 C. for 3 hours to improve the stability and durability of the catalyst. M1 was obtained. The material color was white. The particle size was 3 to 15 m. The specific surface area was 160 m.sup.2/g. The pore volume was 0.38 ml/g.

(3) (2) A Mn(CH.sub.3COO).sub.2 solution was loaded onto M1 by an equal volume impregnation method. The Mn content, based on the element, accounted for 12% of the catalyst mass. Then, it was dried at 60 to 120 C. for 5 hours and calcined at 450 C. in air atmosphere for 5 hours to obtain catalyst C1. The color of the catalyst was black.

Example 2

(4) (1) A dilute HNO.sub.3 solution and a La(NO.sub.3).sub.3 solution were added to pseudo-boehmite, and the pH was adjusted to 3.5 to 4.5, to prepare La.sub.2O.sub.3Al.sub.2O.sub.3 by the sol-gel method, wherein the La.sub.2O.sub.3 accounted for 3% of the mass of La.sub.2O.sub.3Al.sub.2O.sub.3. The La.sub.2O.sub.3Al.sub.2O.sub.3 prepared by the sol-gel method was calcined at 600 C. in air atmosphere for 5 hours, and then continued to be calcined at 800 C. for 3 hours to improve the stability and durability of the catalyst. M2 was obtained. The material color was white. The particle size was 3 to 15 m. The specific surface area was 178 m.sup.2/g. The pore volume was 0.43 ml/g.

(5) (2) A Mn(CH.sub.3COO).sub.2 solution was loaded onto M2 by an equal volume impregnation method. The Mn content, based on the element, accounted for 12% of the catalyst mass. Then, it was dried at 60 to 120 C. for 2 to 6 hours and calcined at 500 C. in air atmosphere for 5 hours to obtain catalyst C2. The color of the catalyst was black.

Example 3

(6) (1) A dilute HNO.sub.3 solution, a La(NO.sub.3).sub.3 solution and a Ce(NO.sub.3).sub.3 solution were added to pseudo-boehmite, and the pH was adjusted to 3.5 to 4.5, to prepare La.sub.2O.sub.3-Ce.sub.2O.sub.3Al.sub.2O.sub.3 by the sol-gel method, wherein the La.sub.2O.sub.3 accounted for 3% of the mass of La.sub.2O.sub.3-Ce.sub.2O.sub.3Al.sub.2O.sub.3, and the Ce.sub.2O.sub.3 accounted for 10% of the mass of La.sub.2O.sub.3-Ce.sub.2O.sub.3Al.sub.2O.sub.3. The La.sub.2O.sub.3-Ce.sub.2O.sub.3Al.sub.2O.sub.3 prepared by the sol-gel method was calcined at 500 C. in air atmosphere for 5 hours, and then continued to be calcined at 800 C. for 3 hours to improve the stability and durability of the catalyst. M3 was obtained. The material color was light yellow. The particle size was 3 to 15 m. The specific surface area was 152 m.sup.2/g. The pore volume was 0.37 ml/g.

(7) (2) A Mn(CH.sub.3COO).sub.2 solution was loaded onto M3 by an equal volume impregnation method. The Mn content, based on the element, accounted for 12% of the catalyst mass. Then, it was dried at 60 to 120 C. for 5 hours and calcined at 450 C. in air atmosphere for 3 hours to obtain catalyst C3. The color of the catalyst was black.

Example 4

(8) (1) A dilute HNO.sub.3 solution, a La(NO.sub.3).sub.3 solution and a Ce(NO.sub.3).sub.3 solution were added to pseudo-boehmite, and the pH was adjusted to 3.5 to 4.5, to prepare La.sub.2O.sub.3-Ce.sub.2O.sub.3Al.sub.2O.sub.3 by the sol-gel method, wherein the La.sub.2O.sub.3 accounted for 2% of the mass of La.sub.2O.sub.3-Ce.sub.2O.sub.3Al.sub.2O.sub.3, and the Ce.sub.2O.sub.3 accounted for 15% of the mass of La.sub.2O.sub.3-Ce.sub.2O.sub.3Al.sub.2O.sub.3. The La.sub.2O.sub.3-Ce.sub.2O.sub.3Al.sub.2O.sub.3 prepared by the sol-gel method was calcined at 500 C. in air atmosphere for 5 hours, and then continued to be calcined at 800 C. for 3 hours to improve the stability and durability of the catalyst. M4 was obtained. The material color was light yellow. The particle size was 3 to 15 m. The specific surface area was 152 m.sup.2/g. The pore volume was 0.36 ml/g.

(9) (2) A Mn(CH.sub.3COO).sub.2 solution and a Pd(NO.sub.3).sub.2 were loaded onto M4 by an equal volume impregnation method. The Mn content, based on the element, accounted for 8% of the catalyst mass. The Pd content, based on the element, accounted for 0.3% of the catalyst mass. Then, it was dried at 60 to 120 C. for 5 hours and calcined at 500 C. in air atmosphere for 5 hours to obtain catalyst C4. The color of the catalyst was black.

Example 5

(10) (1) A dilute HNO.sub.3 solution and a La(NO.sub.3).sub.3 solution were added to pseudo-boehmite, and the pH was adjusted to 3.5 to 4.5, to prepare La.sub.2O.sub.3Al.sub.2O.sub.3 by the sol-gel method, wherein the La.sub.2O.sub.3 accounted for 4% of the mass of La.sub.2O.sub.3Al.sub.2O.sub.3. The La.sub.2O.sub.3Al.sub.2O.sub.3 prepared by the sol-gel method was calcined at 600 C. in air atmosphere for 5 hours, and then continued to be calcined at 800 C. for 3 hours to improve the stability and durability of the catalyst. M5 was obtained. The material color was white. The particle size was 3 to 15 m. The specific surface area was 172 m.sup.2/g. The pore volume was 0.43 ml/g.

(11) (2) A Pd(NO.sub.3).sub.2 was loaded onto M5 by an equal volume impregnation method. The Pd content, based on the element, accounted for 0.5% of the catalyst mass. Then, it was dried at 60 to 120 C. for 2 to 6 hours and calcined at 500 C. in air atmosphere for 5 hours to obtain catalyst C5. The color of the catalyst was light brown.

Example 6

(12) (1) A dilute HNO.sub.3 solution, a La(NO.sub.3).sub.3 solution and a Ce(NO.sub.3).sub.3 solution were added to pseudo-boehmite, and the pH was adjusted to 3.5 to 4.5, to prepare La.sub.2O.sub.3-Ce.sub.2O.sub.3Al.sub.2O.sub.3 by the sol-gel method, wherein the La.sub.2O.sub.3 accounted for 3% of the mass of La.sub.2O.sub.3-Ce.sub.2O.sub.3Al.sub.2O.sub.3, and the Ce.sub.2O.sub.3 accounted for 20% of the mass of La.sub.2O.sub.3-Ce.sub.2O.sub.3Al.sub.2O.sub.3. The La.sub.2O.sub.3-Ce.sub.2O.sub.3Al.sub.2O.sub.3 prepared by the sol-gel method was calcined at 500 C. in air atmosphere for 5 hours, and then continued to be calcined at 800 C. for 3 hours to improve the stability and durability of the catalyst. M6 was obtained. The material color was light yellow. The particle size was 3 to 15 m. The specific surface area was 132 m.sup.2/g. The pore volume was 0.35 ml/g.

(13) (2) A Pd(NO.sub.3).sub.2 was loaded onto M6 by an equal volume impregnation method. The Pd content, based on the element, accounted for 0.5% of the catalyst mass. Then, it was dried at 60 to 120 C. for 5 hours and calcined at 500 C. in air atmosphere for 5 hours to obtain catalyst C6. The color of the catalyst was yellowish brown.

(14) Evaluation Test

(15) The catalysts prepared in the above examples were subjected to an activity evaluation test. In order to evaluate the activity of the catalyst, the prepared catalyst was coated on the metal honeycomb substrate. The catalyst coated on the metal honeycomb substrate was tested for the activity of each catalyst under the following test conditions.

(16) Simulated atmosphere: O.sub.3 concentration of (5.80.2)10.sup.7 (volume fraction), air as balance gas, relative humidity of 70 to 90%, SV=500,000 h.sup.1.

(17) The catalyst was programmed to be heated to 120 C. under the simulated atmosphere, kept at a constant temperature for 2 hours, and then cooled to room temperature.

(18) During the cooling process, an O.sub.3 analyzer was used to test the O.sub.3 content at the downstream of the catalyst. The formula for calculating the conversion efficiency of O.sub.3 at a certain temperature is: (the initial O.sub.3 concentration minus the unconverted O.sub.3 concentration in the exhaust)/the initial ozone concentration. The temperature at which the conversion efficiency reaches 90% is called the complete conversion temperature and is denoted as T.sub.90.

(19) Table 1 compares the complete O.sub.3 conversion temperature T.sub.90 of the catalyst prepared in the example.

(20) TABLE-US-00001 Catalyst T.sub.90 ( C.) Example 1 49 Example 2 52 Example 3 43 Example 4 22 Example 5 26 Example 6 23

(21) It can be seen from Table 1 that

(22) 1) Comparing Examples C1 and C2, wherein the active component MnO.sub.x was loaded on M1 and M2, respectively, under the test conditions of the present invention, although the T.sub.90 of M2 was 3 C. higher than that of M1, M2 has a larger specific surface, larger pore volume and higher temperature tolerance, such that the relative stability of the catalyst was higher, which is suitable for scenarios with higher requirements on the service life of the catalyst.

(23) 2) Comparing Examples C2 and C3, after adding a certain amount of Ce.sub.02 to La.sub.2O.sub.3Al.sub.2O.sub.3, the prepared catalyst has a significant increase in O.sub.3 activity, and T.sub.90 is reduced by 9 C.

(24) 3) Comparing Examples C3 and C4, after the single active component MnO.sub.x is changed to the dual active component MnO.sub.x and PdO, the prepared catalyst has a significant increase in activity to O.sub.3, and the T.sub.90 is reduced to 22 C. At room temperature, O.sub.3 can be completely converted.

(25) 4) Examples C2, C3, C5 and C6 are compared, wherein the two groups of C2 and C5, C3 and C6, respectively, have the same catalytic materials and different active components, which are MnO.sub.x and PdO respectively. Comparing the activity of the four catalysts to O.sub.3, the results all show that when PdO is used as the active component, the activity is significantly better than that with MnO.sub.x as the active component. Due to the high price of noble metals, catalysts with noble metals as active components are mainly suitable for scenarios where the application temperature is low and the purification efficiency and rate are high.

(26) 5) Examples C4, C5, C6 are compared, wherein C4 has a dual active component, and C5 and C6 have a single noble metal active component. By using dual active components, on the basis of a slight increase in activity (T.sub.90 decreased by 1 C. and 4 C., respectively), the amount of noble metals also decreased (from 0.5% to 0.3%).

(27) The above results show that the C1, C2 and C3 catalysts are relatively inexpensive, the T.sub.90 of 03 is higher than room temperature, the purification temperature is within the temperature range of the radiator fin of the water tank when the car is running, and the particle size of the catalyst is 3 to 15 m, with moderate particle size. After coating, the firmness is high, and it can be coated on the radiator of the car radiator or used in application scenarios that do not require high purification efficiency and speed. For C4, C5 and C6 catalysts, the catalyst price is slightly higher, T.sub.90 of O.sub.3 is closed to the ambient temperature in most areas in Southern China. In addition, the T.sub.90 of the catalyst can be adjusted by increasing the amount of active components to be suitable for lower ambient temperature. It can be applied to any place where coating is allowed in public areas such as urban bus stations, stop signs, kiosks, roadside guardrails, or exterior walls of buildings that is in contact with outdoor air.