METHOD FOR PRODUCING METAL EXCHANGED MICROPOROUS MATERIALS BY SOLID-STATE ION EXCHANGE

Abstract

A method is disclosed for the preparation of a metal exchanged microporous materials, e.g. metal exchanged silicoaluminophosphates or metal exchanged zeolites, or mixtures of metal exchanged microporous materials, comprising the steps of providing a dry mixture of a) one or more microporous materials that exhibit ion exchange capacity and b) one or more metal compounds; heating the mixture in a gaseous atmosphere containing ammonia and one or more oxides of nitrogen to a temperature and for a time sufficient to initiate and perform a solid state ion exchange of ions of the metal compound and ions of the microporous material; and obtaining the metal-exchanged microporous material.

Claims

1. Method for the preparation of a metal exchanged crystalline microporous material or mixtures of metal exchanged crystalline microporous materials comprising the steps of providing a dry mixture containing a) one or more crystalline microporous materials that exhibit ion exchange capacity and b) one or more metal compounds; heating the mixture in a gaseous atmosphere containing ammonia and one or more oxides of nitrogen to a temperature and for a time sufficient to initiate and perform a solid state ion exchange of ions of the metal compound and ions of the crystalline microporous material; and obtaining the crystalline metal-exchanged microporous material.

2. Method according to claim 1, wherein the crystalline microporous material is selected from the group consisting of zeolite or zeotype materials.

3. Method according to claim 2, where the zeolite or zeotype materials have the framework code of AEI, AFX, CHA, KFI, LTA, IMF, ITH, MEL, MFI, SZR, TUN, *BEA, BEC, FAU, FER, MOR, LEV.

4. Method according to claim 2, wherein the zeolite or zeotype materials are selected from the group consisting of ZSM-5, zeolite Y, beta zeolite, SSZ-13, SSZ-39, SSZ-62, Chabazite, and SAPO-34, SAPO-44, Ferrierite, TNU-9.

5. Method according to claim 1, wherein the crystalline microporous material or mixtures of crystalline microporous materials are in the H or NH4 form.

6. Method according to claim 1, wherein the crystalline microporous material or mixtures of crystalline microporous material contains an organic structure directing agent.

7. Method according to claim 1, wherein the metal compound is selected from the group of metal oxides, metal nitrates and phosphates, sulfates, oxalates, acetates or a combination thereof.

8. Method according to claim 1, wherein the metals in the metal compounds are selected from the group of Fe, Co, Cu.

9. Method according to claim 1, wherein the metal compounds comprise one or more oxides of Cu.

10. Method according to claim 1, wherein the oxide of nitrogen is selected from nitrogen monoxide, and nitrogen dioxide and mixtures thereof.

11. Method according to claim 1, wherein the content of ammonia in the atmosphere is between 1 and 5000 vol. ppm.

12. Method according to claim 1, wherein the content of the one or more nitrogen oxides in the gaseous atmosphere is between 1 and 5000 vol. ppm.

13. Method according to claim 1, wherein the molar ratio of ammonia to nitrogen oxides is larger than 0.01, preferably between 0.2 and 1.

14. Method according to claim 1, wherein the oxygen content in the atmosphere is 1% or lower.

15. Method according to claim 1, wherein the gaseous atmosphere contains 5% water or less.

16. A method according to claim 1, wherein the mixture is heated in the gaseous atmosphere containing ammonia and one or more oxides of nitrogen to a temperature lower than 300° C., preferably in a range from 100° C. and to below 300° C. and most preferred between 150° C. and 250° C.

17. A metal exchanged crystalline microporous material or mixtures of metal exchanged crystalline microporous materials obtained by a method according to claim 1.

18. A method for the removal of nitrogen oxides from exhaust gas by selective catalytic reduction with a reductant, comprising contacting the exhaust gas with a catalyst comprising a metal exchanged crystalline microporous material or mixtures of metal exchanged crystalline microporous materials obtained in a method according to claim 1.

19. A method according to claim 18, wherein the reductant is ammonia or a precursor thereof.

20. A method according to claim 18, wherein the reductant is hydrocarbons.

Description

EXAMPLE 1

[0038] A catalyst was prepared by mixing CuO and H-ZSM-5 zeolite to a content of 12.5 wt % CuO. A sample of the catalyst was put in a quartz-U tube reactor, and heated to 250° C. for 10 h in a controlled gas atmosphere. After heating, the catalyst was cooled down to 200° C. and exposed to a gas mixture of 500 ppm NO, 533 ppm NH.sub.3, 5% H.sub.2O, 10% O.sub.2 in N.sub.2, and the conversion of NO was measured at a space velocity of 2700 Nl/g cat h, as a record for the material's SCR activity. Table 1 provides an overview of the treatment gas mixtures used in the 10 h preparation step of the catalyst, together with the SCR activity of thus prepared catalyst measured as NO conversion afterwards.

[0039] From the results in Table 1, it becomes clear that the highest SCR activity is obtained when the catalysts are prepared by heating with NH.sub.3 present in the treatment gas. The presence of NO enhances the effect of NH.sub.3, while it has only a very limited or no effect if NO is present without NH.sub.3. When water and/or oxygen are present during the heating, less active materials are obtained, and therefore the presence of water and oxygen is considered less favourable.

TABLE-US-00001 TABLE 1 Measured NOx conversion in the NH3-SCR reaction after treatment in different atmospheres as described in Example 1 Treatment for 10 h at 250° C. NOx conversion in the following atmosphere at 200° C. No treatment 1.4% 5% H.sub.2O + 10% O.sub.2 2.0% 500 ppm NO + 10% O.sub.2 + 5% H.sub.2O 2.0% 530 ppm NH.sub.3 + 10% O.sub.2 + 5% H.sub.2O 2.0% 500 ppm NO + 530 ppm NH.sub.3 + 10% O.sub.2 + 5% H.sub.2O 6.7% 10% O.sub.2 1.0% 500 ppm NO + 10% O.sub.2 2.1% 530 ppm NH.sub.3 + 10% O.sub.2 10.6% 500 ppm NO + 530 ppm NH.sub.3 + 10% O.sub.2 11.7% 5% H.sub.2O 3.0% 500 ppm NO + 530 ppm NH.sub.3 + 5% H.sub.2O 18.2% 500 ppm NO 4.6% 530 ppm NH.sub.3 36.2% 500 ppm NO + 530 ppm NH.sub.3 53.0%

EXAMPLE 2

[0040] This example shows that shortening the duration of the heating at 250° C. from 10 hours to 5 hours has only a minor effect on the SCR activity of the material. Two catalyst samples are prepared as described in Example 1. One sample is heated to 250° C. in a gas atmosphere containing NH.sub.3 and NO for 10 hours, the other sample is heated to 250° C. in a gas atmosphere containing NH.sub.3 and NO for 5 hours. An NH.sub.3-SCR activity measurement at 200° C., as described in Example 1, reveals that the NO conversion with the material heated for 5 hours is 50.8%, and with the material heated for 10 hours is 53.0%. This shows that the initial period of the heating at 250° C. is the most important in the preparation of the active material.

EXAMPLE 3

[0041] This example shows that the method of the invention can be applied using a wide variety of concentrations of ammonia and oxides of nitrogen to produce ion-exchanged zeolites to produce active SCR materials. Catalysts were prepared according to Example 1. The catalysts were also tested according to the procedure, but the concentrations of NO and NH.sub.3 was varied according to Table 2. The results shows that the concentrations of NO and NH.sub.3 can be varied over a large range of concentrations.

TABLE-US-00002 TABLE 3 Measured NOx conversion in the NH.sub.3-SCR reaction after treatment of different zeolites as described in Example3 Treatment for 10 h at 250° C. of H-ZSM-5 + CuO in NO and NH.sub.3 with the following NOx conversion concentrations at 200° C. 250 ppm NO and 265 ppm NH.sub.3 50.8% 500 ppm NO and 530 ppm NH.sub.3 53.0% 1000 ppm NO and 1060 ppm NH.sub.3 54.3%

EXAMPLE 4

[0042] This example shows that the method of the invention can be applied to produce SCR active materials based on zeolites with different crystal structures. Catalysts were prepared and the NO conversion was measured, according to the procedure described in Example 1, but instead of an H-ZSM-5, an H-Beta zeolite or an H-SSZ-13 zeolite was used. Table 3 shows the measured NO conversion by use of the different zeolite materials.

TABLE-US-00003 TABLE 3 Measured NOx conversion in the NH3-SCR reaction after treatment of different zeolites as described in Example 4. Treatment for 10 h at 250° C. in NO and NH.sub.3 of the NOx conversion following zeolites at 200° C. H-ZSM-5 + CuO 53.0% H-BEA + CuO 50.1% H-SSZ-13 + CuO 46.0%

EXAMPLE 5

[0043] This example shows that the method of the invention is not limited to zeolites, which are microporous silica-aluminates, but also can be applied to other microporous materials with ion-exchange capacity. A catalyst was prepared and the conversion of NO was measured according to the procedure in Example 1, but instead of a H-ZSM-5 a H-SAPO-34 material was used. The measured NO conversion was 28.0%. It is noted that the SCR-active SAPO-34 material has not been heated further than 250° C. after addition of the Cu. This example illustrates that the method of the invention provides a way to produce an active catalyst based on SAPO-34 without the need of activation at elevated temperatures (>700° C.), which is the case for conventionally ion-exchanged SAPO-34 materials [P. N. R. Vennestrøm, A. Katerinopoulou, R. R. Tiruvalam, A. Kustov, P. G. Moses, P. Concepcion, A. Corma, ACS Catal. 2013, 3, 2158-2161.] after addition of Cu to the microporous material.

EXAMPLE 6

[0044] This example shows that the method of the invention is preferably applied in the temperature range 150-300° C. A powder mixture consisting of 30 mg H-beta zeolite and 3 mg CuO was put in a reactor and exposed for 5 hours to a gas mixture consisting of 500 ppm NH3 and 500 ppm NO in N2 at a predefined pretreatment temperature. After the pretreatment, the temperature was changed to 200° C. and the sample was exposed to a gas mixture of 600 ppm NH.sub.3, 500 ppm NO, 10% O.sub.2, 6% H.sub.2O in N.sub.2, at a total flow rate 300 Nml/min, and the conversion of NO was measured as a record for the material's SCR activity. Table 4 provides an overview of the treatment temperatures, together with the SCR activity of thus prepared catalyst measured as NO conversion afterwards.

TABLE-US-00004 TABLE 4 Measured NOx conversion in the NH.sub.3-SCR reaction after treatment of a H-Beta zeolite in a gas consisting of 500 ppm NH.sub.3, 500 ppm NO and balance N.sub.2 at different temperatures as described in Example 6. Treatment of a mixture of H-Beta zeolite and CuO for 5 h in a mixture of 500 ppm NO and 500 ppm NH.sub.3 in N2 NOx conversion at the following temperatures at 200° C. 100° C. 10.1% 150° C. 14.4% 175° C. 28.5% 200° C. 53.9% 225° C. 57.7% 250° C. 59.8% 300° C. 64.5%

[0045] From table 4 that a significant enhancement of the NO conversion is observed above 150° C., indicating a more efficient ion exchange in this temperature range.

EXAMPLE 7

[0046] This example shows that the NH.sub.3/NO ratio in the gaseous atmosphere containing NH.sub.3 and an oxide of nitrogen may be varied over a wide range. A powder mixture consisting of 30 mg H-beta zeolite and 3 mg CuO was put in a reactor and exposed for 5 hours to a treatment gas mixture containing 500 ppm NO and a predetermined amount of NH.sub.3 at 250° C. After the pretreatment, the sample was cooled to 200° C. and exposed to a gas mixture of 600 ppm NH.sub.3, 500 ppm NO, 10% O.sub.2, 6% H.sub.2O in N.sub.2, at a total flow rate 300 Nml/min, and the conversion of NO was measured as a record for the material's SCR activity. Table 5 provides an overview of NH.sub.3 content and NH.sub.3/NO ratio in the treatment gas mixture, together with the SCR activity of thus prepared catalyst measured as NO conversion afterwards.

TABLE-US-00005 TABLE 5 Measured NOx conversion in the NH.sub.3-SCR reaction after treatment of a H-Beta zeolite in a gas atmosphere consisting of 500 ppm NO and various amounts of NH3 and balance N.sub.2 at 250° C. as described in Example 7. NOx conversion at 200° C. after NH3/NO treatment at Treatment gas composition ratio 250° C. for 5 h 0 ppm NO/500 ppm NH.sub.3/N.sub.2 infinite 52.2% 500 ppm NO/500 ppm NH.sub.3/N.sub.2 1.00 59.4% 500 ppm NO/375 ppm NH.sub.3/N.sub.2 0.75 57.3% 500 ppm NO/250 ppm NH.sub.3/N.sub.2 0.50 54.7% 500 ppm NO/125 ppm NH.sub.3/N.sub.2 0.25 54.1% 500 ppm NO/0 ppm NH.sub.3/N.sub.2 0.00 19.6%

[0047] From the data in Table 5, it can be seen that the ion exchange process according to the invention is effective for a wide range of compositions of the treatment gas atmosphere containing NH.sub.3 and NO. If no NH.sub.3 is present, the NOx conversion is significantly lower, indicating a less efficient ion-exchange process. The positive effect of NO on the ion exchange process in the presence of NH.sub.3 is clearly seen in the enhancement of the NO conversion compared to that after treatment in NH.sub.3 alone.

EXAMPLE 8

[0048] This example shows that the ion exchange process by the method of the invention is more effective at low oxygen concentrations. A powder mixture consisting of 30 mg H-beta zeolite and 3 mg CuO was put in a reactor and exposed for 5 hours to a treatment gas mixture containing 500 ppm NO, 500 ppm of NH.sub.3, and 0, 1, 5, or 10% oxygen, at 250° C. After the pretreatment, the sample was cooled to 200° C. and exposed to a gas mixture of 600 ppm NH.sub.3, 500 ppm NO, 10% O.sub.2, 6% H.sub.2O in N.sub.2, at a total flow rate 300 Nml/min, and the conversion of NO was measured as a record for the material's SCR activity. Table 6 provides an overview of the oxygen concentration in the treatment gas mixture, together with the SCR activity of thus prepared catalyst measured as NO conversion afterwards.

TABLE-US-00006 TABLE 6 Measured NO.sub.x conversion in the NH.sub.3-SCR reaction after treatment of a H-Beta zeolite in a gas consisting of 500 ppm NH.sub.3, 500 ppm NO and 0, 1, 5, or 10% O2, with balance N.sub.2 at 250° C. as described in Example 8. Treatment of a mixture of H-Beta zeolite and CuO for 5 h in a mixture of 500 ppm NO and 500 ppm NH.sub.3 in N2 at 250° C. with the following concentrations of oxygen in NOx conversion the treatment gas: at 200° C. 0% O.sub.2 59.4% 1% O.sub.2 47.5% 5% O.sub.2 47.8% 10% O.sub.2  46.7%

[0049] From Table 6, it is seen that the NOx conversion after treatment in a gas containing 1-10% O.sub.2 is almost the same, while the NOx conversion after treatment in a gas without oxygen is clearly higher, indicating a more efficient ion-exchange in that case.

EXAMPLE 9

[0050] This example shows that the ion exchange process according to the invention is more efficient at temperatures below 300° C. A powder mixture consisting of 30 mg H-beta zeolite and 3 mg CuO was put in a reactor and exposed for 5 hours to a treatment gas mixture containing 500 ppm NO and 500 ppm of NH.sub.3 in nitrogen at various temperatures in the range 150-450° C. After the pretreatment, the sample was cooled to 200° C. and exposed to a gas mixture of 600 ppm NH.sub.3, 500 ppm NO, 10% O.sub.2, 6% H.sub.2O in N.sub.2, at a total flow rate 300 Nml/min, and the conversion of NO was measured as a record for the material's SCR activity. Table 7 provides an overview of the treatment temperature and the corresponding SCR activity of thus prepared catalyst measured as the NO.sub.x conversion afterwards at 200° C.

TABLE-US-00007 TABLE 7 Measured NO.sub.x conversion in the NH.sub.3-SCR reaction after treatment of a H-Beta zeolite in a gas consisting of 500 ppm NH.sub.3, 500 ppm NO with balance N.sub.2 at different temperatures in the ranger 150-450° C. as described in Example 9. 5 h treatment in 500 ppm NH.sub.3/500 ppm NO/N.sub.2 at the NOx conversion following temperatures: at 200° C. 150° C. 14.3 175° C. 28.2 200° C. 53.7 250° C. 59.4 325° C. 59.4 350° C. 40.8 400° C. 26.3 450° C. 25.1

[0051] The results in Table 7 shows that the NOx conversion after treatment in the range 200-325° C. is highest, indicating that the ion-exchange procedure according to the invention is most effective in this temperature range.